Abstracts From the 38th Annual Scientific Meeting of the HBPRCA
HBPRCA Oral Presentations
TOLERABILITY OF COMBINATION BLOOD PRESSURE LOWERING ACCORDING TO BLOOD PRESSURE LEVELS – AN ANALYSIS OF THE PROGRESS AND ADVANCE TRIALS
Atkins ERab, Hirakawa Ya, Salam Aab, Woodward Mac, Chalmers Ja, Rodgers Aab, on behalf of the ADVANCE and PROGRESS investigators
aThe George Institute for Global Health, Sydney, New South Wales, Australia; bSydney Medical School, University of Sydney, Sydney, New South Wales, Australia; cThe George Institute for Global Health, University of Oxford, Oxford, UK
Background: Combination blood-pressure lowering therapy provides greater blood pressure reduction than monotherapy and therefore greater reductions in major cardiovascular events. One concern is that combination therapy produces higher rates of adverse effects, particularly among those with baseline systolic blood pressure below 140 mmHg. The ADVANCE and PROGRESS placebo-controlled trials of combination therapy recruited participants with a wide range of blood pressure levels and so provide a unique opportunity to investigate side-effects of combination therapy according to baseline blood pressure.
Aims: To measure the placebo-controlled effects of combination therapy on hypotension, treatment discontinuation and major renal outcomes, according to baseline blood pressure.
Methods: 14,684 participants allocated combination therapy or placebo were stratified into five groups by baseline systolic blood pressure (SBP) <120 mmHg, 120–129 mmHg, 130–139 mmHg, 140–159 mmHg, and ≥160 mmHg. Cessation of study treatment during the active run-in phase and post-randomization follow-up was assessed for hypotension and other causes.
Results: Discontinuation during the 4–6-week active run-in phase due to hypotension/dizziness ranged from 3.6% in those with SBP <120 mmHg to 1.3% in those with SBP ≥160 mmHg. Median follow-up in the randomized phase was 5.6 years, and discontinuation for hypotension was higher with combination therapy compared to placebo in the <120 mmHg group (4.7% vs. 1.2%). However, for each subgroup with baseline SBP 120–129, 130–139 and 140–159 mmHg the absolute excess of discontinuation due to hypotension with combination therapy was 0.7%.
Conclusion: Compared to those with baseline SBP 140–159 mmHg, side-effects of dual combination blood-pressure lowering are essentially the same for people with SBP 130–139 mmHg and only modestly increased among patients with SBP 120–129 mmHg. During long-term therapy, side-effects sufficient to stop treatment, in excess of rates seen with placebo, occur at <0.5%/year in patients with baseline SBP 120–139 mmHg. These results have important implications in assessing the likely balance of benefits and side-effects of blood-pressure lowering with combination therapy among those with SBP 120–139 mmHg.
HUMAN AMNION STEM CELL-DERIVED EXOSOMES IMPROVE STROKE OUTCOME IN MALE MICE
Broughton BRSa, Ghaly Aa, Lim Rb, Wallace EMb, Sobey CGa
aDepartment of Pharmacology, Monash University, Clayton, Victoria, Australia; bThe Ritchie Centre, Hudson Institute of Medical Research, Clayton, Victoria, Australia
Background: Recent findings by our Laboratory indicate that human amnion epithelial cells (hAECs), which are a placental stem cell, are neuroprotective following stroke. However, little is known about the factors that these cells release to elicit neuroprotection. Like most cell types, stem cells secrete extracellular microvesicles called exosomes, which are involved in cellular communication and thought to be the active component of stem cells.
Aims: To test whether hAEC-derived exosomes exhibit similar neuroprotective effects as hAECs post-stroke.
Methods: Male mice (8–12 weeks old) were anaesthestized with intraperitoneal ketamine (80 mg/kg) and xylazine (10 mg/kg) and subjected to 30 min middle cerebral artery occlusion (n=20) or sham surgery (n=6). At 1 h following reperfusion, mice were injected intravenously with vehicle (saline; n=8), 106 hAECs (n=8) or 10 μg of hAEC-derived exosomes (n=6). After 24 h, functional outcomes and infarct volumes were assessed and immune cell infiltration and glial scarring were analysed via immunohistochemistry.
Results: Mice treated with either hAECs or exosomes were able to grip a wire for 63% and 45% longer compared to vehicle, respectively. Furthermore, the treated mice had a lower neurological deficit score compared to vehicle-treated mice. Infarct volume was reduced by 56% (P=0.05) and 65% (P<0.05) following hAEC and exosome administration, respectively. Consistent with hAEC treatment, exosomes prevented the increase in neutrophils and T cells in the ischemic hemisphere. Finally, exosomes abolished stroke-induced glial scar formation and hAECs reduced its size by 58%, although this was not statistically significant
Conclusion: These data indicate that hAEC-derived exosomes provide similar neuroprotective benefits as hAECs following ischemic stroke, thus demonstrating the potential of exosomes as a future stroke therapy.
DIETARY SALT INCREASES ARTERIAL STIFFNESS INDEPENDENT OF BLOOD PRESSURE AND LIFESTYLE FACTORS
Butlin Ma, Connolly Kb, Spronck Bc, Georgevsky Da, McEneiry CMb, Wilkinson IBb, Avolio APa
aFaculty of Medicine and Health Sciences, Macquarie University, Sydney, New South Wales, Australia; bDivision of Experimental Medicine, University of Cambridge, Addenbrooke’s Hospital, Cambridge, UK; cDepartment of Biomedical Engineering, CARIM School for Cardiovascular Diseases, Maastricht University Medical Centre, Maastricht, The Netherlands
Background: Human studies show an association between high salt consumption and increased large artery stiffness, but are confounded by concomitant differences in blood pressure and altered lifestyle factors.
Aims: To examine the effects of a high-salt diet on aortic function independent of all other factors.
Methods: Sprague-Dawley rats were fed normal chow (control, 0.26% sodium chloride, n=8) or high-salt diet (HS, 8% sodium chloride, n=6) from weaning. A third group received a high-salt diet and an antihypertensive (HS+Tx, s.c. amlodipine 5 mg/kg/day, n=6). At 14–17 weeks, thoracic and abdominal aortic pressure (invasive solid-state catheters) was recorded under anesthesia over a mean arterial pressure (MAP) range of 60–150 mmHg (i.v. phenylephrine and sodium nitroprusside, 30 μg/kg/min). Aortic stiffness was assessed by pulse wave velocity (PWV) and thoracic to abdominal aortic pulse pressure amplification (PPA).
Results: Conscious systolic blood pressure (tail-cuff) was greater in HS rats (control 117±13 mmHg, HS 125±12 mmHg; P=0.004) and normalized by antihypertensive treatment (HS+Tx 112±13 mmHg, P=0.12). Higher blood pressure was associated with increased kidney mass (normalized to body weight, control 0.8±0.1%, HS 1.0±0.2%; P=0.002; HS+Tx 0.9±0.1%; P=0.17) without left ventricular hypertrophy (P=0.58). Food intake was similar amongst all groups but HS and HS+Tx rats drank more with correspondingly higher urine output. HS had higher PWV (across MAP range 60–150 mmHg: control 3.6±0.1 to 4.0±0.3 m/s; HS, 4.2±0.2 to 4.6±0.3 m/s; P<0.001 at each 5 mmHg MAP interval). Increased PWV was maintained with antihypertensive treatment (HS+Tx 3.9±0.1 to 4.8±0.1 m/s; P<0.001). PPA was greater in HS (across MAP range 60 to 150 mmHg: control 0.64±0.08 to 1.24±0.11; HS 0.89±0.02 to 1.54±0.04; P<0.001 at each 5 mmHg MAP interval) and with antihypertensive therapy (HS+Tx 0.79±0.05 to 1.39±0.03; P<0.001).
Conclusion: Under controlled blood pressure, a high-salt diet induced greater aortic stiffness and higher PPA, indicating salt effects on arterial stiffness are independent of blood pressure and other lifestyle factors.
FIRST EVIDENCE OF PULSATILE PRESSURE INTERACTION BETWEEN THE MACRO-VASCULATURE AND MICRO-VASCULATURE: PROOF-OF-CONCEPT BY ASSOCIATION WITH KIDNEY DYSFUNCTION AMONG PATIENTS WITH TYPE 2 DIABETES
Climie REab, Picone DSb, Blackwood Sb, Qasem Ac, Rattigan Sb, Sharman JEb
aBaker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia; bMenzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia; cUniversity of New South Wales, Sydney, New South Wales, Australia
Background: It is widely thought that excess pulsatile pressure energy from increased stiffness of large central arteries (macro-vasculature) is transmitted to capillary networks (micro-vasculature) and causes end-organ damage (i.e. kidneys). However, this hypothesis has never been tested.
Aims: The aim of this study was to firstly determine the association between simultaneously measured macro-vasculature and micro-vasculature waveform features in people with increased macro-vascular stiffness (patients with type 2 diabetes; T2DM) compared with non-diabetic controls; and secondly to determine the association of waveform features with kidney function.
Methods: Among 13 T2DM patients (aged 68±6 years) and 15 controls (58±11 years) macrovascular function was measured by aortic stiffness and radial artery waveforms by tonometry. Forearm microvascular waveforms were simultaneously measured via low power laser Doppler flowmetry, with augmentation index (AIx) and augmented pressure (AP) derived on all waveforms. Kidney function was assessed by estimated glomerular filtration rate (eGFR).
Results: Aortic stiffness was higher among T2DM patients (9.3±2.5 vs. 7.5 ±1.4 m/s; P=0.046). There was an obvious pulsatile micro-vascular waveform, with qualitative features similar to radial waveforms. Macro-vasculature AIx and AP were significantly related to micro-vasculature AIx (r=0.428, P=0.005 and r=0.545, P=0.004 respectively). Microvascular (but not macrovascular) AIx was associated with eGFR in T2DM (r=–0.632, P=0.037).
Conclusion: This is the first-in-human evidence of pulsatile pressure interaction between the macro-vasculature and micro-vasculature, and provides potential explanation for accelerated kidney dysfunction.
LONGITUDINAL CHANGES IN AORTIC RESERVOIR FUNCTION INDEPENDENTLY PREDICT DECLINING RENAL FUNCTION AMONG HEALTHY INDIVIDUALS
Climie REab, Picone DSb, Sharman JEb
aBaker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia; bMenzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia
Background: Aortic reservoir function independently predicts end-organ damage in cross-sectional analyses. Longitudinal associations are more important regarding causation, but have never been examined.
Aims: To determine the longitudinal changes in aortic reservoir characteristics and the relationship with renal function in healthy individuals.
Methods: Aortic reservoir function (excess pressure integral [xsP] and aortic reservoir pressure), aortic stiffness, brachial and central blood pressure (BP), and renal function (estimated glomerular filtration rate [eGFR]) were recorded among 33 healthy individuals (age 57±9 years; 55% male) at baseline and after an average 3.0±0.3 years.
Results: Over the follow-up period there was no significant change in brachial BP (P>0.05), whereas there was a trend for xsP (P=0.061) and central BP (P=0.068) to increase. On the other hand, aortic stiffness and blood glucose increased significantly (P<0.05 for both). The change over time in xsP (but not aortic stiffness) was significantly related to the change in eGFR (r=–0.370, P=0.044) and this remained independent age, 24-hour systolic BP and body mass index (β=–0.031, P=0.045), but not blood glucose (β=–0.031, P=0.053). There was no interaction between the change in glucose and change in xsP.
Conclusion: Aortic reservoir function, as determined by excess pressure, is independently associated with a decline in renal function among healthy people followed over 3 years. These novel findings indicate the need to determine the underlying physiological determinants of aortic reservoir function.
EPIGENETIC CLUES TO THE BLOOD PRESSURE “LEGACY EFFECT” IN SPONTANEOUSLY HYPERTENSIVE RATS
De Vries Na, Prestes Pa, Kiran Sa, Allen Ab, Rana Ia, Samani Nc, Harrap SBb, Charchar FJa
aSchool of Applied and Biomedical Sciences, Faculty of Science and Technology, Federation University Australia, Ballarat, Victoria, Australia; bDepartment of Physiology, University of Melbourne, Melbourne, Victoria, Australia; cDepartment of Cardiovascular Sciences, University of Leicester, Leicester, UK
Background: In the spontaneously hypertensive rat (SHR) the “legacy effect” is the persistent reduction in blood pressure (BP) and increased lifespan after short-term treatment with an angiotensin converting enzyme inhibitor (ACEi). However, the molecular machinery involved in resetting BP is unclear. Genes, non-coding RNA and DNA methylation are potential candidates.
Aims: To examine whether epigenetic changes might be associated with the “legacy effect” in the spontaneously hypertensive rat (SHR).
Methods: 6-week-old male SHR were treated with the ACEi perindopril (1 mg/kg/d) (n=6) or vehicle (n=6) for 48 hours. Average global DNA methylation was quantified in renal cortices using the 5-mC ELISA Kit (Zymo Research, USA) which features a unique anti-5-methylcytosine monoclonal antibody that is both sensitive and specific for 5-mC. We also measured the expression of epigenetic regulators histone deacetylase 1 (Hdac1), solute carrier family 16 member 3 (monocarboxylate transporter, Mct3) and DNA (cytosine-5-)-methyltransferase 1 (Dnmt1) using quantitative PCR.
Results: Global DNA methylation was reduced in the renal cortices of animals treated with ACEi (P<0.05, Figure 1). Acute treatment with perindopril did not significantly change the renal expression of Hdac1, Dnmt1 and Mct3 (P>0.05).
Conclusion: Acute treatment by ACEi results in a reduction in global DNA methylation indicating that epigenetics may play an important role in the “legacy effect”. Using next-generation RNA sequencing we are currently investigating the long-term effect and specific genes that contribute to these changes.
RELATIONSHIPS BETWEEN FATNESS AND FITNESS AND CARDIOMETABOLIC RISK FACTORS IN ADOLESCENTS FROM THE WESTERN AUSTRALIAN PREGNANCY (RAINE) COHORT STUDY
Demmer DLa, Beilin LJa, Hands Bb, Burrows Sa, Cox KLa, Oddy WHc, Mori TAa
aSchool of Medicine and Pharmacology, Royal Perth Hospital Unit, The University of Western Australia, Perth, Western Australia, Australia; bInstitute for Health Research, The University of Notre Dame Australia, Western Australia, Perth, Australia; cThe Menzies Institute for Medical Research, The University of Tasmania, Hobart, Tasmania, Australia
Background: Independent effects of cardiorespiratory fitness and obesity on cardiovascular risk factors are well established in adults. However, their relative importance is uncertain, particularly during the crucial developmental stage of late adolescence.
Aim: To examine and compare the concurrent influences of cardiorespiratory fitness and fatness in relation to cardiometabolic risk factors in adolescents from the Western Australian Pregnancy (Raine) Cohort Study at age 17 years.
Methods: Fatness was determined from waist circumference. Cardiorespiratory fitness was estimated from heart rate recordings during sub-maximal cycle ergometry with adjustment for body weight. Fatness and fitness were assessed as continuous measures to avoid the use of arbitrary cut points and linear regression analyses were used.
Results: Fatness was positively associated with systolic blood pressure (P<0.001), triglycerides (P<0.001), low density lipoprotein-cholesterol (P=0.007) and high-sensitivity C-reactive protein (P<0.001). Fatness also increased the risk of being pre-hypertensive or hypertensive (P=0.001). There were no significant effects of fitness on any of these measures. A positive association between homeostatic model assessment of insulin resistance and fatness (P<0.001) was attenuated by fitness (P<0.001). Fatness was inversely associated with high density lipoprotein-cholesterol in both sexes (P<0.001), while fitness was positively associated with high density lipoprotein-cholesterol only in females (p=0.03). Fitness was inversely associated with diastolic blood pressure (P<0.001), whereas there was no association with fatness.
Conclusion: Fitness attenuated the adverse effects of fatness on few cardiometabolic risk factors. However, fatness had generally stronger associations with an adverse cardiometabolic profile in this population of 17-year-olds. Strategies to avoid excessive weight gain will need to focus on both eating patterns and physical activity in early childhood to minimize the risk of cardiovascular and metabolic disease in later life.
IMPORTANCE OF LYMPHOCYTES, ESTROGEN AND THE G PROTEIN COUPLED ESTROGEN RECEPTOR 1 IN ALDOSTERONE/SALT-INDUCED HYPERTENSION
Dinh QNa, Vinh Aa, Broughton BRSa, Chrissobolis Cb, Drummond GRa, Sobey CGa
aCardiovascular Disease Program, Biomedicine Discovery Institute and Department of Pharmacology, Monash University, Clayton, Victoria, Australia; bDepartment of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio, USA
Background: The G protein-coupled estrogen receptor 1 (GPER), a membrane-localized estrogen receptor, may contribute to some of the effects of aldosterone. Aldosterone may not bind to GPER but it can promote interaction between the GPER and its classical target, the mineralocorticoid receptor. G1, a GPER agonist, can exert T cell-mediated anti-inflammatory actions and has been reported to acutely lower blood pressure in normotensive male rats. We tested whether GPER activity might influence chronic pressor changes during aldosterone/salt-induced hypertension, and if those effects were sex-specific and immune cell-dependent.
Aims: To test the effects of G1 and G15 (GPER antagonist) in two models of hypertension: 1) aldosterone/salt and 2) angiotensin II, and to examine the role of lymphocytes in those effects.
Methods: C57Bl6 mice (n=140) and RAG1-deficient mice (n=24) were treated with vehicle, aldosterone/salt (0.72 mg/kg/d s.c. plus 0.9% NaCl for drinking) or angiotensin II (0.7 mg/kg/d s.c.) ± G1 (0.03 mg/kg/d s.c.) and/or G15 (0.3 mg/kg/d s.c.) for 14 d. Blood pressure was measured by tail-cuff. GPER expression was assessed by flow cytometry or immunofluorescence.
Results: In male C57Bl6 mice, aldosterone/salt caused a sustained increase in blood pressure of ~24 mmHg within 7 d and this increase was attenuated by ~50% in the presence of G1 (n=11–13, P<0.05). The antihypertensive effect of G1 was prevented by G15, whereas G15 alone did not alter hypertension caused by aldosterone/salt. By contrast, in male RAG1-deficient mice, aldosterone/salt had no effect on blood pressure (n=8, P<0.05). In female C57Bl6 mice, aldosterone/salt alone had no effect on blood pressure after 7 d, but co-administration of aldosterone/salt with G15 resulted in a profound increase of ~18 mmHg (n=6–8, P<0.05). By day 14, aldosterone/salt alone had increased blood pressure in females to a similar level as aldosterone/salt + G15. Neither G1 nor G15 had any effect on angiotensin II-induced hypertension in male C57Bl6 mice (n=5–7). CD4+ T cells, CD8+ T cells, CD19+ B cells and F4/80+ macrophages in spleen and kidney of both male and female C57Bl6 mice were found to express GPER intracellularly.
Conclusion: Aldosterone/salt-induced hypertension is lymphocyte-dependent and is attenuated/delayed in females due to GPER activity. Therapeutic activation of GPER, likely on T and/or B cells, exerts antihypertensive effects during hypertension caused by aldosterone/salt but not angiotensin II.
CONSTRUCTING HUMAN CARDIAC TISSUE FROM PLURIPOTENT STEM CELLS INCLUDING ELECTRICAL STIMULATION
Dusting GJabc, Hernandez Dab, Sivakumaran Pa, Shepherd RKbd, Wong Raymond CBbc, Pebay Abc, Lim SYab
aO’Brien Institute Department, St Vincents Institute, Melbourne, Victoria, Australia; bDepartments of Surgery, Medicine, Medical Bionics and Ophthalmology; cCentre for Eye Research Australia; dBionics Institute, University of Melbourne, Melbourne, Victoria, Australia
Background: Cardiac tissue engineering, particularly that utilizing autologous human stem cells, has the potential to produce constructs of cardiac tissue for surgical replacement of inefficient or damaged cardiac muscle or pacemaker tissue. Both pediatric and adult applications may be possible. Such constructs will also be useful as testing platforms for development of new drugs and pharmacological safety. We have established platforms to grow robust cardiac constructs with an integrated vasculature, constructs that grow and survive transplantation. Fully vascularized, robust beating cardiac tissue has been grown in pedicles constructed in polyacrylate chambers, and implanted in vivo in rats.
Aim: To grow integrated constructs of human cardiac tissue of mature ventricular phenotype from stem cells.
Methods: We have used both mesenchymal stem cells (MSC) and induced pluripotent stem (iPS) cells as sources of human cardiomyocytes to grow cardiac constructs in vivo. Using the traditional embryoid body (EB) approach to generate beating, cardiomyocyte-like cells from iPS cells, we stimulated these differentiating cells electrically in bespoke chambers for short periods of up to 15 min. In a separate series of experiments, iPS cells were grown in monolayers, replated into the stimulating chambers for 4 d then stimulated continuously (1 ms, 200 mV/mm, 1Hz) for 7 d. Finally other iPS-derived cells grown in monolayers were replated into a fibrin matrix (>I.5 million cells per batch), then implanted into specially designed polyacrylate chambers incorporating miniaturized power packs and stimulating electrodes. These cell batches were wrapped around arterial and venous femoral vessels, implanted in vivo in immunocompromised rats, and stimulated for 4 h daily for 3 weeks, using a cage with pulsating orthogonal magnetic field, which generated charge-balanced electrical pulses in the chamber with the same parameters as those previously used in vitro. The tissues thus produced were examined after 3 weeks of stimulation in one leg, the tissues growing in the other with similar chambers that lacked stimulating electrodes, acting as controls.
Results: Stimulating iPS–derived cells electrically for prolonged periods (at 1 Hz up to 7 d) in vitro increased the maturation of derived cardiomyocytes towards an adult ventricular phenotype as assessed by several measures, including promoting their alignment with the electrical field. In vivo, disassociated cells did not survive the transplantation for 4 weeks, but transplanted human cell clumps grew into robust cardiac tissue in the constructs, characterized by troponin T striations interspersed with lectin-stained vessels. The modified bionic chambers described above, which enabled electrical stimulation of developing constructs in vivo, thus encouraged the development of contracting constructs in the chamber, incorporating human cardiac cells vascularized profusely by rat host vessels. In preliminary studies to date it was not possible to discern any difference resulting from 3 weeks of electrical stimulation in vivo. Further studies with more powerful and prolonged stimulating protocols are underway.
Conclusion: These tissue engineering approaches incorporating endogenous vascularization provide proof-of-principle for generation of substantial, transplantable cardiac tissue from human iPS cells. Electrical stimulation of sufficient power promotes maturation of the cardiomyocytes towards an adult ventricular phenotype, a goal that has eluded many in the field to date.
VITAMIN D SUPPLEMENTATION REDUCES BRAIN INJURY AND INFLAMMATION FOLLOWING ISCHEMIC STROKE
Evans MAa, Kim HAa, Ling YHa, Uong Sa, Drummond GRab, Broughton BRSa, Sobey CGab
aCardiovascular Disease Program, Biomedicine Discovery Institute and Department of Pharmacology Clayton, Victoria, Australia; bDepartment of Surgery, Southern Clinical School, Monash University, Clayton, Victoria, Australia
Background: Following ischemic stroke, inflammation is a major contributor to secondary brain injury and further tissue infarction. Beyond its well-characterized role in calcium metabolism, the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25-VitD3), has been shown to elicit anti-inflammatory actions. Given the contributing role of the immune system in acute post-stroke brain injury, we hypothesized that vitamin D3 supplementation may reduce brain injury in association with reduced inflammation following stroke.
Aims: To determine whether supplementation of 1,25-VitD3 reduces inflammatory brain injury after ischemic stroke in mice.
Methods: Male C57BL/6 mice (aged 7–10 weeks) were randomly assigned either 1,25-VitD3 (n=32; 100 ng/kg per day i.p.) or vehicle (n=30; mixture of dH2O, propylene glycol and ethanol) commencing 5 d prior to stroke. Stroke was induced via middle cerebral artery occlusion for 1 h followed by 23 h reperfusion. Twenty-four hours after stroke induction, hanging grip and parallel rod tests were used to assess grip strength and locomotor activity, respectively. In addition, infarct volume was assessed by thionin staining and cerebral inflammation was evaluated using real-time PCR and immunohistochemistry.
Results: Supplementation with 1,25-VitD3 reduced cerebral infarct volume by 50% compared to vehicle (18±3 mm3 versus 36±6 mm3, respectively; n=12–14, P<0.05). However, at this early time-point there were no differences in functional outcomes, with hanging grip time and total time mobile being similar in 1,25-VitD3- and vehicle-supplemented groups. Expression of key pro-inflammatory cytokines, IL-6, IL-1β and IL-23a, was reduced in brains of mice that received 1,25-VitD3 versus vehicle (n=9–12, P<0.05). Expression of the T regulatory cell marker, FOXP3, was further elevated in mice supplemented with 1,25-VitD3 (n=11 per group; P<0.05). Immunohistochemistry revealed that numbers of neutrophils and T cells infiltrating the ischemic hemisphere were similar in 1,25-VitD3- and vehicle-supplemented groups (n=5–8). Ongoing experiments are assessing other immune cell types, and whether pre-existing vitamin D deficiency predisposes to a worse stroke outcome.
Conclusion: These data indicate that administration of exogenous vitamin D to vitamin D-replete mice can attenuate infarct development and exert anti-inflammatory actions. This may represent a direction for acute stroke therapy.
POST HOC ANALYSIS OF THE EFFECTIVENESS OF BLOOD PRESSURE-LOWERING DRUG TREATMENT BY LEVELS OF ABSOLUTE RISK IN THE ANBP STUDY
Ho CLBa, Breslin Ma, Doust Jb, Reid CMc,d, Nelson MRa
aMenzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia; bBond University, Robina, Queensland, Australia; cCurtin University, Bentley, Western Australia, Australia; dMonash University, Clayton, Victoria, Australia
Background: Cardiovascular disease (CVD) continues to represent a considerable burden on the health care system. International guidelines for the primary prevention of CVD recommend drug treatment for elevated blood pressure (BP) based on BP thresholds with due deference to underlying absolute CVD risk. Guidelines in Australia and New Zealand give pre-eminence to risk stratification using risk calculators to determine BP-lowering drug treatment thresholds. However clinicians are concerned that the average risk approach compared with a BP threshold may be an inferior strategy.
Aims: To examine if BP-lowering treatment based on baseline CVD risk would have superior outcomes compared with a simple BP threshold for those with “mildly” elevated BP.
Methods: We conducted a post hoc subgroup analysis of the Australian National Blood Pressure study (ANBP). The ANBP study was a randomized placebo controlled trial, in which participants were recruited from the community with “mildly” elevated diastolic BP between 1973 and 1979. In the present study, we involved participants aged 35 to 69 years. All analyses were based on the “intention to treat.” The Cox proportional hazard model was used to estimate the hazard ratios (HRs) and corresponding 95% confidence intervals for participants classified by tertile of Framingham risk scores.
Results: Participants had an average 5-year CVD risk in the intermediate range (10.5±6.5) with moderately elevated BP (159/103 mmHg) and were middle-aged (52±8 years). We identified no significant effect of BP lowering drug treatment on major CVD events with a HR 0.83 (0.65–1.07) or all-cause mortality with a HR 0.75 (0.45–1.36) and a borderline significant effect of stroke with a HR 0.55 (0.31–1.00). In subgroup analyses, the relative and absolute effects did not significantly differ across the CVD risk groups. In terms of absolute benefit, BP-lowering drug treatment significantly reduced the number of events in the high-risk tertile with respect to any event with a number needed to treat (NNT) of 19 (95% CI 11–78), death from any cause with a NNT of 49 (95% CI 26–338)) and major CVD event with a NNT of 23 (95% CI 12–164).
Conclusion: BP-lowering drug treatment produced non-significant effects in the overall study population. Our analysis confirms that the benefit of treatment was substantial only in the high-risk tertile, reaffirming the rationale of treating elevated BP in the setting of all risk factors rather than in isolation.
CCL18 AS A MEDIATOR OF THE PRO-FIBROTIC ACTIONS OF M2 MACROPHAGES IN THE VESSEL WALL DURING HYPERTENSION
Lewis CVa, Zhu Ma, Lieu Ma, Moodley Sa, Wang Ya, McConaghy TEa, Larner Ba, Widdop REa, Sobey CGa, Drummond GRa, Kemp-Harper BKa
aDepartment of Pharmacology, Monash University, Clayton, Victoria, Australia
Background: M2 macrophages contribute to vascular fibrosis and stiffening in hypertension. A potential mediator of these actions is the macrophage-derived, pro-fibrotic chemokine, CCL18, which signals via its cognate receptor, CCR8. Little is known about the role of CCL18 in cardiovascular disease. In addition, the localization and expression of CCR8 in the vascular wall has not been investigated.
Aims: To determine if angiotensin II augments CCL18 production from human primary M2 macrophages, identify cardiovascular targets of CCL18 and investigate the ability of CCL18 to promote fibrosis.
Methods: Human primary macrophages were treated with the M2-polarising stimulus, IL-4 (0.05–50 ng/mL, 6–72 h) and CCL18 expression was measured (qRT-PCR, ELISA). Following a submaximal dose of IL-4 (0.5 ng/mL, 24 h), angiotensin II (100 pM) was added for a further 24–48 h in the presence or absence of the angiotensin II type 1 receptor (AT1R) antagonist, candesartan (1 μM), and effects on CCL18 expression were measured. The BP of saline or angiotensin II (0.7 mg/kg/d s.c., 28 d)-treated male C57BL/6J mice were measured by tail cuff. Localization and expression of CCR8 and the murine functional analogue of CCL18, CCL8, were assessed in the thoracic aorta by immunohistochemistry and qRT-PCR, respectively. Type 1 collagen was measured via western blotting in CCL18 (3–300 ng/ml, 72 h)-treated human cardiac fibroblasts.
Results: IL-4 caused concentration- and time-dependent increases in macrophage CCL18 mRNA (up to 1700-fold, P<0.05, n=5–7) and protein (up to 500-fold, p<0.05, n=4–7) expression. In M2-polarised macrophages (0.5 ng/mL IL-4), angiotensin II appeared to increase CCL18 protein levels by a further 70% and this was attenuated by candesartan (n=2–4). In aortas from hypertensive mice, mRNA expression of CCL8, but not CCR8, was elevated 3-fold (P<0.05, n=4–8) and CCL8 and CCR8 co-localized with macrophages and endothelial cells, respectively. CCR8 expression was also evident in the adventitia and perivascular fat. Finally, CCL18 increased pro- and mature type 1 collagen expression in human cardiac fibroblasts (n=4).
Conclusion: Angiotensin II increases CCL18 generation from M2 macrophages, which may target CCR8 expressing endothelial, adventitial and/or perivascular fat cells to promote fibrosis and vascular stiffening. CCL18 also promotes collagen synthesis from human cardiac fibroblasts. Thus, CCL18 and its receptor CCR8, may serve as potential targets for the treatment of vascular and cardiac fibrosis during hypertension.
GENETIC VARIATION IN KRUPPEL-LIKE FACTOR 15 INFLUENCES MYOCARDIAL MASS IN PATIENTS WITH TYPE 2 DIABETES AND IS ASSOCIATED WITH HEART FAILURE HOSPITALIZATION
Patel SKa, Wai Bb, Velkoska Ea, Harrap SBc, Srivastava PMab, Burrell LMab
aDepartment of Medicine, University of Melbourne, Austin Health, Melbourne, Victoria, Australia; bDepartment of Cardiology, Austin Health, Melbourne, Victoria, Australia; cDepartment of Physiology, University of Melbourne, Melbourne, Victoria, Australia
Background: Left ventricular (LV) hypertrophy (LVH) is prevalent in type 2 diabetes and associated with adverse cardiovascular (CV) outcomes including heart failure. The transcriptional factor Kruppel-like factor 15 (KLF15) is expressed in the heart and acts as a repressor of cardiac hypertrophy.
Aims: To investigate whether KLF15 gene variants are associated with increased LV mass and heart failure hospitalization in patients with type 2 diabetes.
Methods: We recruited 346 asymptomatic patients with type 2 diabetes for transthoracic echocardiography (Melbourne Diabetes Heart Cohort). Patients with valvular dysfunction/replacement/repair (n = 28) were excluded. No patient had a previous history of heart failure. Two common KLF15 tagging single nucleotide polymorphisms (SNPs) were genotyped (rs9838915, rs6796325) in 318 patients. LVH was defined as LV mass (indexed to body surface area) of >115 g/m2 in men and >95 g/m2 in women.
Results: The mean age (±SD) was 64±12 years (54% male), BMI was 32±6 kg/m2, hypertension was present in 79% and median diabetes duration was 10 years [25, 75th quartile 5, 16]. The KLF15 SNP rs9838915 A allele was associated in a dominant manner with LV mass (GA+AA genotype vs. GG homozygotes: 105.8±28.3 vs. 95.9±25.5 g/m2) before (P = 0.003) and after (P = 0.001) adjustment for age, gender, BMI and hypertension, and with adjusted septal (P<0.0001) and posterior (P=0.004) wall thickness. There were no significant associations between the KLF15 SNP rs6918698 and LV mass. LVH was present in 35% of patients. Over a median follow up of 5.6 years, there were 22 (7%) heart failure hospitalizations. The adjusted risk of heart failure hospitalization was 5.5-fold greater in those with LVH and the rs9838915 A allele compared to those without LVH and the GG genotype (hazard ratio 5.5 (95% CIs 1.6–18.6; P=0.006). This association was independent of age, gender, BMI, systolic blood pressure and hypertension.
Conclusion: We report for the first time that genetic variation in KLF15 influences myocardial mass in patients with type 2 diabetes and is associated with heart failure hospitalization. Studies are needed to characterize the functional importance of these results, and to determine if the KLF15 SNP rs9838915 A allele is associated with LVH in patients without diabetes.
DISCOVERY OF A NEW BLOOD PRESSURE PHENOTYPE FROM INTRA-ARTERIAL CENTRAL-TO-PERIPHERAL RECORDINGS: IMPLICATIONS FOR CUFF BLOOD PRESSURE ACCURACY AND CARDIOVASCULAR RISK ASSESSMENT
Picone DSa, Schultz MGa, Peng Xa, Black JAab, Dwyer Nab, Roberts-Thomson Pab, Srikanth VKacd, Sharman JEa
aMenzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia; bRoyal Hobart Hospital, Hobart, Tasmania, Australia; cCentral Clinical School, Faculty of Medicine, Monash University, Clayton, Victoria, Australia; dDepartment of Medicine, Peninsula Health, Frankston, Victoria, Australia
Background: Individual variability in central-to-peripheral systolic blood pressure (SBP) amplification might make it difficult for brachial cuff blood pressure (BP) to accurately reflect intra-arterial BP, but this has never been determined.
Aims: To characterize SBP-amplification phenotypes and examine the association of these with cuff BP accuracy.
Methods: Following coronary angiography, intra-arterial BP was measured at the ascending aorta, brachial and radial arteries in 99 patients (aged 61.9±10.0 years; 68% male). Cuff BP was measured using two separate oscillometric devices at the following times: (A) bilaterally before catheterization (A&D UA-767) and (B) simultaneously with intra-arterial brachial BP (SphygmoCor Xcel). SBP-amplification was defined by ≥ 5 mmHg SBP increase between the aorta-to-brachial or brachial-to-radial arteries.
Results: Average aortic-to-brachial and brachial-to-radial SBP-amplification were 8.1±9.2 mmHg and 6.4±10.1 mmHg respectively. However, four distinct SBP-amplification phenotypes were observed: (i) both aortic-to-brachial and brachial-to-radial SBP-amplification (n=29); (ii) only aortic-to-brachial SBP-amplification (n=30); (iii) only brachial-to-radial SBP-amplification (n=22); (iv) no aortic-to-brachial or brachial-to-radial SBP-amplification (n=18). Compared with the first three phenotypes, patients with no SBP-amplification had elevated aortic SBP (144±23 mmHg vs. 125±19; 130±23 and 135±11 mmHg, respectively; P=0.019) that was significantly underestimated by each brachial cuff BP device (–12.9±21 mmHg; P=0.046 (A) and –8.4±9.6 mmHg; P=0.002 (B)), despite no differences in clinical characteristics or cuff BP between phenotypes (P>0.05 for all).
Conclusion: These are the first data to describe distinctive central-to-peripheral SBP-amplification phenotypes, and includes discovery of a phenotype in which cardiovascular risk is likely to be elevated because of significantly increased aortic SBP that is not detected by conventional cuff BP methods.
RENAL DENERVATION PREVENTS PROGRESSION OF HYPERTENSION AND CHANGES TO BAROREFLEX IN A RABBIT MODEL OF CHRONIC KIDNEY DISEASE
Sata Ya, Burke SLa, Denton KMb, Schlaich MPa, Head GAa
aBaker IDI Heart & Diabetes Institute, Melbourne, Victoria, Australia; bDepartment of Physiology, Monash University, Clayton, Victoria, Australia
Background: Hypertension associated with chronic kidney disease (CKD) rapidly progresses to become treatment-resistant but the benefits of renal denervation (RDN) in this disease are unknown. A rabbit model of moderate CKD, induced by 11/12th nephrectomy and characterized by rapid and sustained elevation of plasma creatinine and hypertension, allows for determination of the effects of RDN and whether its efficacy improves with time.
Aims: To determine the effects of RDN on CKD-induced changes to mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), baroreflex function and renal function and whether they are altered by time after RDN.
Methods: Rabbits underwent RDN of the left renal nerve 2 weeks after CKD was induced by lesion of the left kidney and right nephrectomy. In sham rabbits, both kidneys were denervated. MAP, RSNA recorded from the left renal nerve and baroreflexes were examined 2 and 4 weeks after RDN.
Results: Two weeks after induction of CKD, creatinine increased by 59% and remained elevated by 41% over the following 4 weeks. MAP had increased by 14% to 77±1 mmHg after CKD and continued to rise from this level by +8% and +13% after 2 and 4 weeks in sham RDN rabbits, while creatinine did not change. However, in rabbits which underwent RDN, there was no further increase in MAP (P<0.001 after 4 weeks RDN). RSNA was 23% lower 2–3 weeks following RDN than after sham RDN (P<0.05) and the hypotensive response to pentolinium was reduced by 50%. CKD shifted the RSNA baroreflex towards the higher MAP and this was reversed after 2 weeks of RDN with marked reductions in gain (38%) and range (42%). There was no further change to the baroreflex after 4 weeks RDN. Neither GFR (14±2 mL/min in controls), which was 45% lower in CKD rabbits, nor creatinine levels, were altered by 4 weeks of RDN.
Conclusion: RDN is effective for at least 4 weeks in ameliorating the hypertension in this model of CKD. Sympathetic activation and changes to the RSNA baroreflex were also reversed without altering renal function. Our results suggest that RDN may be an effective treatment for moderate CKD.
EXAGGERATED EXERCISE BLOOD PRESSURE IS ASSOCIATED WITH RAISED LEFT-VENTRICULAR MASS AND AORTIC STIFFNESS IN ADOLESCENCE: A cross-sectional analysis of the Avon Longitudinal Study of Parents and Children (ALSPAC)
Schultz MGa, Park Cb, Fraser Ac, Howe LDc, Jones Sb, Rapala Ab, Davey Smith Gc, Sharman JEa, Lawlor DAC, Chaturvedi Nb, Deanfield Jb, Hughes ADb
aMenzies Institute for Medical Research, University of Tasmania, Hobart, Tsmania, Australia; bInstitute of Cardiovascular Sciences, University College London, London, UK; cMRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK
Background: Dynamic exercise results in increased systolic blood pressure (BP). Irrespective of resting BP, some individuals may experience an exaggerated rise in systolic BP with exercise, which in adulthood is associated with risk of developing hypertension, cardiovascular (CV) morbidity and mortality. It is unknown if exercise BP is associated with adverse CV risk during adolescence.
Aims: In a large group of adolescents, we aimed to determine if exercise systolic BP was associated with hypertension-related CV risk markers (left-ventricular mass (LVM) and aortic stiffness) independent of resting (office) BP status, with further consideration of the possible confounding effect of body composition.
Methods: A total of 4,036 adolescents (mean age 17.8±0.4 years, 45% male), part of a UK population-based birth cohort study, completed a sub-maximal step-test with BP measurement post-exercise. Sub-samples underwent assessment of echocardiographic LVM (n=2,067), aortic pulse wave velocity (aPWV; n=3,582) and body composition by dual-energy x-ray absorptiometry (DXA; n=3,875). Resting BP status was classified as raised if systolic and/or diastolic BP was in the ≥ 95th percentile.
Results: Each 5 mmHg increase in post-exercise systolic BP was associated with a 0.31 g/m2.7 (95% CI 0.22, 0.40) greater LVM index, and 0.03 m/s (95% CI 0.02, 0.03) increased aPWV after adjustment for age, sex and resting BP status (P<0.05). Further adjustment for DXA-measured total body fat and lean mass attenuated the relationship with LVMI to 0.14 g/m2.7 (95% CI 0.05, 0.22; P<0.001) and aPWV to 0.02 m/s (95% CI 0.02, 0.03) per 5 mmHg of post-exercise systolic BP (P<0.001).
Conclusion: In adolescents, exercise systolic BP is associated with hypertension-related CV risk markers that are prognostic in adults independent of resting (office) BP status. Adjustment for body composition attenuates, but does not abolish, these associations. Given the clinical relevance of exaggerated exercise BP in adulthood, these results may have implications for CV risk in later life.
VARIABILITY IN CENTRAL-TO-PERIPHERAL GRADIENTS OF MEAN ARTERIAL PRESSURE AND DIASTOLIC BLOOD PRESSURE WITHIN THE HUMAN LARGE ARTERIES: RELEVANCE TO ARTERIAL PHYSIOLOGY AND ESTIMATED CENTRAL BLOOD PRESSURE
Schultz MGa, Picone DSa, Peng Xa, Black JAa,b, Dwer Na,b, Roberts-Thomson Pa,b, Sharman JEa
aMenzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia; bRoyal Hobart Hospital, Hobart, Tasmania, Australia
Background: In order to aid blood flow, the gradient of mean arterial pressure (MAP) and diastolic blood pressure (DBP) is thought to decline approximately 1–3 mmHg through the large arteries. The magnitude of this gradient is also of potential importance for accurate waveform calibration and non-invasive estimation of central BP. However, there are few data determining the individual variability of MAP and DBP gradients from central to peripheral large arteries.
Aims: To determine the magnitude and variability in MAP and DBP gradients from the aorta to the brachial and radial arteries.
Methods: A total of 75 patients (mean age 62±11 years) undergoing cardiac angiography had intra-arterial BP measured via fluid-filled catheter in the ascending aorta, brachial and radial arteries by sequential pull-back. MAP was calculated by integration of ensemble averaged waveforms, and DBP from the foot of the waveforms at each intra-arterial site.
Results: On average, MAP and DBP gradients decreased over the aortic-brachial (MAP –1.4±4.0 mmHg; DBP –2.5±3.8 mmHg), brachial-radial (MAP –2.4±4.1 mmHg; DBP –2.0±3.1 mmHg) and aortic-radial (MAP –3.8±4.4 mmHg; DBP –4.5±3.6 mmHg) arterial segments. The magnitude of the aortic-radial MAP (range –14.9 to 6.8 mmHg) and DBP (range –13.1 to 2.6 mmHg) gradient was, however, highly variable, and included reversal of the MAP and DBP gradient (increase) among 23% and 12% of patients, respectively.
Conclusion: Although MAP and DBP gradients reduce on average from central to peripheral large arteries, the magnitude of this gradient is variable. These new observations are highly relevant to understanding arterial hemodynamic pathophysiology and accurate non-invasive estimation of central BP.
VARIABILITY IN BRACHIAL-TO-RADIAL SYSTOLIC BLOOD PRESSURE AMPLIFICATION AFFECTS ACCURACY OF CENTRAL SYSTOLIC BLOOD PRESSURE ESTIMATED FROM THE RADIAL ARTERY: AN INTRA-ARTERIAL STUDY
Schultz MGa, Picone DSa, Peng Xa, Black JAa,b, Dwyer Na,b, Roberts-Thomson Pa,b, Sharman JEa
aMenzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia; bRoyal Hobart Hospital, Hobart, Tasmania, Australia
Background: Central systolic blood pressure (SBP) can be non-invasively estimated from radial pressure waveforms. Calibration of the radial waveform using brachial BP is advocated on the assumption of negligible brachial-to-radial SBP amplification. However, recent evidence suggests there may be significant variability in brachial-to-radial SBP amplification, and this could affect accuracy of central BP estimation, although has never been examined.
Aims: To determine the level of brachial-to-radial SBP amplification and the consequent effect on the accuracy of estimated central SBP.
Methods: Intra-arterial BP was measured via sequential catheter pull-back at the ascending aorta, brachial and radial arteries among 77 patients (mean age 62±11 years) undergoing diagnostic coronary angiography. Accuracy of estimated central SBP was assessed by comparison of intra-arterial aortic SBP with estimated central SBP (SphygmoCor) derived by calibrating the radial pressure waveform with either brachial or radial SBP and diastolic BP (DBP).
Results: SBP increased stepwise from the aorta to the brachial and radial arteries (128.6±19.5, 137.9±18.8, 144.0±21.5 mmHg, respectively; P<0.001). Calibrating the radial pressure waveform with brachial SBP and DBP resulted in a significant underestimation of central SBP (–8.7±9.3 mmHg, P<0.001). Recalibration with radial SBP and DBP significantly (P<0.001) improved the accuracy of estimated central SBP (–5.2±10.4, P<0.001). Importantly, brachial-to-radial SBP amplification was highly variable (6.1±9.7, range –14 to +28 mmHg). Underestimation of central SBP increased stepwise with each increasing tertile of brachial-to-radial SBP amplification when the radial waveform was calibrated with brachial SBP and DBP (–5.8±6.1, –8.2±7.2, –12.6±12.4 mmHg, P<0.001).
Conclusion: There is significant variability in brachial-to-radial SBP amplification and this affects the accuracy of estimated central SBP when radial pressure waves are calibrated with brachial SBP and DBP. Thus, brachial SBP and DBP should not be used to calibrate radial pressure waveforms in the estimation of central BP.
PRESSURE-INDUCED T CELL INFILTRATION IS CAVEOLIN-1 DEPENDENT
Shihata WAa,b, Andrews KLa, Sampson AKb, Jefferis AMa, Vinh Aa, Murphy AJb, Chin-Dusting JPFa
aCardiovascular Disease Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia; bBaker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
Background: A common cause of cardiac hypertrophy is high blood pressure that we have previously shown to induce changes in endothelial phenotype via a caveolin-1 (cav-1) dependent mechanism. A role for the adaptive immune system has been established in the onset and progression of hypertension. Specifically, T cell infiltration is thought to play a pivotal role.
Aims: To investigate the contribution of pressure to the infiltration of T cells in both in vitro and in vivo settings and its subsequent effects on cardiovascular pathology.
Methods: Supernatants collected from cav-1 scrambled (SCR) or knockdown (KD) mouse endothelial cells that were either untreated, treated with the known migration stimulus CCL21 (100 ng/mL), tumor necrosis factor (TNF)-α 24 (10 ng/mL) or that were pressurized at 0 or 120 mmHg for 24 hours, were examined for their ability to induce T cell migration in a dual chamber migratory assay system. The number and phenotype of migrated T cells was assessed via flow cytometric analysis. In addition, we examined whether T cell migration into the heart was altered in the 4 week angiotensin II (Ang II; 490 ng/min/kg) induced hypertensive model in wild-type (C57BL/6) and cav-1–/– mice. Systolic blood pressure (SBP) and cardiac hypertrophy were also assessed.
Results: Compared to untreated, unpressurized cells (8,020±2,772 SD, n=4), T cell migration was induced by supernatant from CCL2-treated SCR cells (27,612±3,117, n=7; P<0.001), TNF-α–treated cells (25,936±5,173, n=10; P<0.001) and pressurized SCR cells (32,913±1,458; n=6; P<0.01). However, a significant increase in T cell migration was observed only in the TNF-α– and CCL21-treated cav-1 KD cells (P<0.001), but not in the pressurized setting (2,328±749, n=12) relative to the untreated cav-1 KD cells (4,305±1,897, n=4; P>0.05). Of note, approximately 50% of migrated T cells in all treatment groups were of the T helper subtype. Although an increase in SBP was observed in both Ang II-treated wild-type and cav-1–/– mice, increases in T cell infiltration in the heart were observed only in Ang II-treated wild-type mice, but not in Ang II-treated cav-1–/– mice relative to their controls. This was accompanied by Ang II-induced cardiac hypertrophy in the Ang II-treated wild-type, but not the Ang II-treated cav-1–/– mice compared to the untreated wild-type and cav-1–/– mice, respectively.
Conclusion: We found that elevated pressure induces T cell migration and infiltration via a cav-1 dependent mechanism. Since cardiac hypertrophy was not exacerbated despite the increase in SBP in AII-treated cav-1–/– mice, we postulate that cardiac T cell infiltration may play a role, potentially via a fibrotic process.
PRENATAL HYPOXIA AND A POSTNATAL HIGH SALT DIET PREDISPOSES MOUSE OFFSPRING TO CARDIOVASCULAR AND RENAL IMPAIRMENTS IN ADULTHOOD
Walton SLa, Singh RRb, Bielefeldt-Ohmann Ha, Li Ja, Paravicini TMa, Little MHc, Moritz KMa
aSchool of Biomedical Sciences, University of Queensland, St Lucia, Queensland, Australia; bCardiovascular Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Victoria, Australia; cMurdoch Childrens Research Institute< Melbourne, Victoria, Australia
Background: In Australia, chronic kidney disease and cardiovascular disease are prominent public health issues. Both are linked to abnormal kidney development, notably reduced nephron number, which may result from in utero perturbations.
Aims: We evaluated the impact of prenatal hypoxia on renal and cardiovascular development and function in the mouse, and whether high salt intake could exacerbate functional impairments.
Methods: Pregnant CD1 mice were housed in a hypoxic chamber (12.0% O2) or control (21% O2) environment from embryonic day 14.5 to 19.5 (birth). Offspring consumed control (0.2% NaCl) or high-salt (5% NaCl) diets from 10 weeks to 12 months of age. Renal function was examined via 24 h metabolic cages and blood pressure was measured by radiotelemetry at 12 months of age. Mesenteric arteries were collected for pressurized in vitro myography studies. Kidneys were used to determine nephron number by unbiased stereology. Hearts and kidneys from 12-month-old offspring were evaluated by an expert pathologist.
Results: Male hypoxia-exposed offspring presented with elevated urinary albumin excretion at 12 months of age. This was associated with a 25% reduction in nephron endowment, significant glomerular hypertrophy and glomerulosclerosis compared to male control offspring. These histopathological changes were exacerbated by the high-salt diet. In contrast, female hypoxia-exposed offspring had normal nephron endowment and no overt signs of renal impairment or histopathology. Male and female hypoxia-exposed offspring both presented with an approximately 14 mmHg increase in mean arterial pressure and mild vascular endothelial dysfunction. Consumption of a high-salt diet in both sexes led to marked mesenteric vascular stiffening and cardiac fibrosis in hypoxia-exposed offspring.
Conclusion: Prenatal hypoxia perturbed kidney development, impaired renal function and increased susceptibility to salt-induced renal injury in male offspring. Both sexes developed signs of cardiovascular disease in adulthood. This suggests that female offspring are afforded some renoprotection from hypoxia in utero. However, this protection does not extend to the cardiovascular system.
PLASMA POTASSIUM NEGATIVELY EFFECTS ABUNDANCE OF THE THAIZIDE SENSITIVE SODIUM-CHLORIDE COTRANSPORTER IN HUMANS
Wolley Ma, Wu Aa, Gordon RDa, Fenton RAb, Stowasser Ma
aEndocrine Hypertension Research Centre, University of Queensland School of Medicine, Greenslopes and Princess Alexandra Hospitals, Brisbane, Queensland, Australia; bUniversity of Aarhus, Department of Biomedicine, Aarhus, Denmark
Background: The thiazide sensitive sodium-chloride cotransporter (NCC) is important for sodium reabsorption and blood pressure. With-no-lysine-kinase 4 (WNK4) is now thought to be an important regulator of NCC, and is mutated in some cases of Gordon’s syndrome, causing hypertension and hyperkalemia. We have previously demonstrated that WNK4 and NCC in human urinary exosomes appears to be sensitive to mineralocorticoids, but recent animal studies suggest that potassium is a dominant regulator of NCC, possibly via regulation of WNK4.
Aims: To test the effect of potassium on regulation of NCC and WNK4.
Methods: We isolated urinary exosomes from 26 subjects (20 with primary aldosteronism and 6 cured after adrenalectomy for aldosterone-producing adenoma), before fludrocortisone suppression testing and again after 3 days of fludrocortisone administration, and quantified abundance of NCC, phosphorylated NCC (pNCC) and WNK4 by Western blot.
Results: The patients with cured primary aldosteronism had lower aldosterone (144 pmol/L vs. 643 pmol/mL; P<0.001) and a higher potassium (4.7 mmol/L vs. 3.6 mmol/L; P<0.001) compared to those with primary aldosteronism. NCC was > 4 fold, pNCC was > 5.5 fold, and WNK4 was > 6 fold higher in patients with primary aldosteronism compared to those who had been cured (P<0.05 for all). There were very strong negative correlations at baseline between plasma potassium and WNK4 (R2=0.57; P<0.001), NCC (R2=0.66; P<0.001) and pNCC (R2=0.43; P<0.01). There were weaker positive associations between plasma aldosterone and NCC (R2=0.34; P<0.01) and WNK4 (R2=0.24; P=0.03). After 3 days of fludrocortisone administration, however, there was no apparent relationship between potassium and abundance of NCC, WNK4 or pNCC.
Conclusion: NCC and its phosphorylated form pNCC are upregulated in primary aldosteronism, along with the regulatory kinase WNK4. Plasma potassium is closely related to the abundance of WNK4, NCC and pNCC, suggesting that potassium plays a role in NCC regulation, but might be over-ridden by mineralocorticoid stimulation in some circumstances.
HBPRCA Poster Presentations
EFFECT OF MOXONIDINE ON THE ALDOSTERONE/RENIN RATIO CALCULATED BY BOTH PLASMA RENIN ACTIVITY AND DIRECT RENIN CONCENTRATION IN HEALTHY MALE VOLUNTEERS
Ahmed AHa, Gordon RDa, Ward Gb, Wolley Ma, McWhinney BCc, Ungerer JPc, Stowasser Ma
aEndocrine Hypertension Research Centre, University of Queensland School of Medicine, Greenslopes and Princess Alexandra Hospitals, Brisbane, Queensland, Australia; bSullivan & Nicolaides Pathology, Brisbane, Queensland, Australia; cDepartment of Chemical Pathology, Pathology Queensland, Royal Brisbane and Women’s Hospital, Brisbane, Queensland, Australia
Background: The most popular screening test for primary aldosteronism (PA) is the plasma aldosterone/renin ratio (ARR). Medications, dietary sodium, posture and time of day all affect renin and aldosterone levels, and can result in false negative or positive ARRs if not controlled. Most antihypertensive medications affect the ARR and can interfere with interpretation of results. To our knowledge, no study has been undertaken to evaluate the effects of moxonidine on the ARR.
Aims: To evaluate the effects of moxonidine on the ARR.
Methods: Normotensive, non-medicated male volunteers (n=20) underwent measurement (seated, midmorning) of plasma aldosterone (by HPLC-tandem mass spectrometry), direct renin concentration (DRC), renin activity (PRA), cortisol, electrolytes and creatinine and urinary aldosterone, cortisol, electrolytes and creatinine at baseline, and after one week of moxonidine at 0.2 mg/d and a further five weeks at 0.4 mg/d.
Results: Compared with baseline, despite the expected significant falls in both systolic and diastolic blood pressure, levels of plasma aldosterone (median 134 [range 90–535] pmol/L), DRC (20 [10–37] mU/L), PRA (2.2 [1.0–3.8] ng/mL/h) and ARR using either DRC (8.0 [4.4–14.4]) or PRA (73 [36–218]) were not significantly changed after either one (135 [98–550] pmol/L, 20 [11–35] mU/L, 2.0 [1.2–4.1] ng/mL/h, 8.8 [4.2–15.9] and 73 [32–194], respectively) or six weeks 130 (90–500) pmol/L, 22 (8–40) mU/L, 2.1 (1.0–3.2) ng/mL/h, 7.7 (4.3–22.4) and 84 (32–192)] of moxonidine. There were no changes in any urinary measurements.
Conclusion: Moxonidine was associated with no significant change in the ARR and may therefore be a good option for maintaining control of hypertension when screening for PA.
EFFECT OF COMBINED HORMONAL REPLACEMENT THERAPY ON THE ALDOSTERONE/RENIN RATIO IN POSTMENOPAUSAL WOMEN
Ahmed AHa, Gordon RDa, Ward Gb, Wolley Ma, McWhinney BCc, Ungerer JPc, Stowasser Ma
aEndocrine Hypertension Research Centre, University of Queensland School of Medicine, Greenslopes and Princess Alexandra Hospitals, Brisbane, Queensland, Australia; bSullivan & Nicolaides Pathology, Brisbane, Queensland, Australia; cDepartment of Chemical Pathology, Pathology Queensland, Royal Brisbane and Women’s Hospital, Brisbane, Queensland, Australia
Background: Plasma aldosterone/renin ratio (ARR) is the most popular screening test for primary aldosteronism (PA). Both estrogen and progesterone affect aldosterone and renin levels, but the effects of combined hormonal replacement therapy (HRT) on ARR have not been studied.
Aims: To examine the effects of combined hormonal replacement therapy (HRT) on ARR, measuring renin as both direct renin concentration (DRC) and plasma renin activity (PRA).
Methods: 15 normotensive, healthy postmenopausal women underwent measurement (seated, midmorning) of plasma aldosterone, DRC, PRA, electrolytes and creatinine and urinary aldosterone, cortisol, electrolytes and creatinine at baseline and after 2 and 6 week’s treatment with combined HRT (conjugated oestrogens 0.625 mg and medroxyprogesterone 2.5 mg daily).
Results: Treatment with combined HRT was associated with significant increases in aldosterone (baseline median [range] 150 [85–600], 2 weeks 230 [129–790], 6 weeks 434 [200–1200] pmol/L; P<0.001 [Friedman test]) and PRA (2.3 [1.2–4.3], 3.8 [1.4–7.0], 5.1 [1.4–10.8] ng/mL/h; P<0.001], but decreases in DRC (21 [10–31], 21 [10–39], 14 [8.0–30] mU/L; P<0.01) leading to increases in ARR calculated by DRC (7.8 [3.6–34.8], 11.4 [5.4–48.5], 30.4 [10.5–90.2]; P<0.001]. The ARR calculated by DRC exceeded the cut off value (70) in three patients after 6 weeks. There were no significant changes in ARR calculated by PRA (79 [26–184], 91 [23–166], 88 [50–230]; P=0.282], plasma electrolytes and creatinine, and all urinary measurements.
Conclusion: The combined oral HRT used in this study is capable of significantly increasing ARR with a risk of false positive results during screening for PA, but only if DRC (and not PRA) is used to calculate the ratio.
FLAVONOID-RICH APPLE IMPROVES ENDOTHELIAL FUNCTION IN INDIVIDUALS AT RISK FOR CARDIOVASCULAR DISEASE
Bondonno NPa, Bondonno CPa, Rich La, Ward NCab, Hodgson JMa, Croft KDa
aUniversity of Western Australia, School of Medicine and Pharmacology, Royal Perth Hospital, Perth, Western Australia, Australia; bSchool of Biomedical Sciences and Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia
Background: Studies show an inverse association between apple intake and coronary mortality. The health benefits of apples have been attributed to their flavonoid content, which is considerably higher in the peel compared to the flesh. Endothelial dysfunction occurs before vascular disease is detected and is an independent predictor of cardiovascular risk. Our previous research has shown an improvement in endothelial function following apple consumption. To determine if the benefits of apples are due to their flavonoid-rich skin, we gave volunteers apples with skin or apple flesh-only as a control.
Aims: To determine if acute and chronic (4 weeks) ingestion of flavonoid-rich apple would improve endothelial function and BP in human volunteers with at least one risk factor for CVD.
Methods: We conducted a randomized, controlled, crossover trial with 30 men and women with one or more of the following: 120 < systolic BP < 160, 5.6 < blood glucose < 6.5, 5 < total cholesterol < 8 or central obesity (men > 94 cm; women > 80cm). We assessed acute and chronic changes in BP, endothelial function, arterial stiffness, and levels of plasma flavonoid metabolites, cholesterol, glucose, nitrate and nitrite. Differences between interventions were assessed by mixed models ANOVA with adjustments for baseline.
Results: We observed significant improvements in endothelial function 2 hours after acute ingestion (0.7%; P<0.0001) and after 4 weeks chronic ingestion (0.58%; P<0.0001) of the apple with skin intervention compared to the control. We saw a significant increase in plasma quercetin metabolites after the acute and chronic apple with skin intervention. We saw no significant changes in other measurements.
Conclusion: Our results support the theory that flavonoid-rich foods protect against cardiovascular disease by improving endothelial function, both acutely and chronically. The mechanism behind this is yet to be elucidated.
THE ACUTE EFFECTS OF QUERCETIN-3-O-GLUCOSIDE ON ENDOTHELIAL FUNCTION AND BLOOD PRESSURE: A RANDOMIZED DOSE-RESPONSE STUDY
Bondonno NPa, Bondonno CPa, Rich La, Mas Ea, Shinde Sa, Ward NCab, Hodgson JCa, Croft KDa
aUniversity of Western Australia, School of Medicine and Pharmacology, Royal Perth Hospital, Perth, Western Australia, Australia; bSchool of Biomedical Sciences and Curtin Health Innovation Research Institute, Curtin University, Perth, Western Australia, Australia
Background: Epidemiological studies suggest that a flavonoid-rich diet can reduce the risk of developing cardiovascular disease. Certain flavonoids, in particular quercetin, have been shown to ameliorate endothelial dysfunction and reduce blood pressure, possibly by increasing the bioavailability of the potent vasodilator, nitric oxide (NO). Several studies indicate that improvements in measures of cardiovascular health do not improve linearly, but rather plateau or decrease with increasing dose of flavonoids.
Aims: To determine if acute administration of increasing doses quercetin-3-O-glucoside improved endothelial function and reduced blood pressure (BP) in a dose-dependent manner. We also explored whether any effects correlated with changes in plasma NO production.
Methods: A randomized controlled crossover study was performed in 15 healthy volunteers who each completed 5 visits with a minimum washout period of 1 week in between testing days. Participants received each of the 5 interventions, in a random order: (i) 0 mg, (ii) 50 mg, (iii) 100 mg, (iv) 200 mg or (v) 400 mg quercetin-3-O-glucoside. Endothelial function and blood pressure were assessed before and 60 min post-intervention. A blood sample was taken before and 90 min post-intervention for analysis of plasma nitrate and nitrite as markers of NO production, as well plasma quercetin metabolites.
Results: Although we observed a significant correlation between dose of quercetin-3-O-glucoside and plasma concentrations of total quercetin (R2=0.52, P<0.001) and isorhamnetin (R2=0.12, P=0.005), we found no improvements in endothelial function or BP and no changes in NO production after any dose.
Conclusion: There were no acute changes in BP or NO-mediated endothelium-dependent relaxation of the brachial artery with doses of quercetin ranging from 50 mg to 400 mg in a group of healthy men and women.
INTER-ARM DIFFERENCES IN MEASURED BRACHIAL SYSTOLIC BLOOD PRESSURE TRANSLATE TO FALSE DIFFERENCES IN CALCULATED CENTRAL AORTIC BLOOD PRESSURE
Butlin Ma, Cook MTDa, Theobald DAa, Avolio APa, Peebles Ka
aFaculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia
Background: Inter-arm differences in brachial systolic blood pressure (SBP) may be real and cardiovascular risk predictive or measurement artefact. If real, measurement from either arm should result in similar calculated central, aortic SBP, there being only one aortic SBP at any time. If artefactual, differences may correlate with inter-arm asymmetry in factors influencing brachial SBP assessment, such as arm geometry.
Aims: To ascertain whether inter-arm differences in brachial SBP translate to differences in aortic SBP and to determine whether these inter-arm differences are correlated with arm geometry.
Methods: Brachial SBP was measured simultaneously in both arms 4 times (alternating blood pressure devices for each measurement) in 79 people (aged 18–71 years; 40 male). Each measurement included brachial volumetric displacement waveform recording, from which central, aortic SBP was calculated (SphygmoCor XCEL). Arm volume covered by the cuff was measured using a perometer and an indication of arm muscle mass asymmetry was measured using a maximal hand grip strength test with appropriate position of the arm.
Results: Brachial SBP was significantly higher in one arm compared to the other in 11 subjects (average difference across those 11 subjects: 5.4±0.7 mmHg). Aortic SBP was higher when calculated from one arm than when calculated from the other in 18 subjects (average difference across those 18 subjects: 3.1±0.6 mmHg). Across the cohort, average brachial SBP inter-arm difference was 4.1±2.5 mmHg. Aortic SBP as calculated from each arm exhibited a difference of 3.1±2.0 mmHg, and was highly correlated with inter-arm difference in brachial SBP (R2=0.67, P<0.0001). Dominant/non-dominant difference in SBP was not correlated with inter-arm difference in brachial volume or grip strength. However, inter-arm brachial SBP difference was positively associated with BMI and dominance in the right arm (i.e., more prevalent in right handed people) and negatively associated with age and absolute brachial systolic pressure.
Conclusion: Calculation of aortic SBP from both arms simultaneously leads to a false “difference” in aortic pressure as measured from each arm. This was highly associated with the inter-arm brachial SBP difference. The brachial SBP inter-arm difference was negatively associated with traditional cardiovascular risk factors such as age and SBP magnitude, but was not associated with asymmetry in arm strength or volume.
PET OWNERSHIP AND SURVIVAL IN AN ELDERLY HYPERTENSIVE POPULATION
Chowdhury EKa, Nelson MRb, Jennings GLRc, Wing LMHd, Reid CMa.e
aCentre of Cardiovascular Research and Education in Therapeutics, Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Victoria, Australia; bUniversity of Tasmania, Hobart, Tasmania, Australia; cBaker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia; dSchool of Medicine, Flinders University, Adelaide, South Australia, Australia; eSchool of Public Health, Curtin University, Perth, Western Australia, Australia
Background: Observational studies have demonstrated a health benefits from having a companion animal. However, the association between pet ownership, survival and improved cardiovascular risk is still unclear.
Aims: To assess the association of pet ownership and all-cause and cardiovascular mortality over a long-term follow-up among elderly treated hypertensive participants.
Methods: Pet ownership data from a sub-cohort of the Second Australian National Blood Pressure (ANBP2) study were used. Participants were aged 65–84 years at enrolment (1995–1997), and responded to a pet-ownership questionnaire during the year 2000. Participants’ survival information was determined over a median of 10.9 years that included the ANBP2 in-trial period (median 4.2 years) together with the post-trial follow-up period (median 6.9 years). For the current study end-points were any fatal cardiovascular event and all-cause fatal events.
Results: Of those who responded to a pet-ownership questionnaire (4039/6018 [67%]), 86% (3490/4039) had owned at least one pet at any time during their life (current or previous pet owner), with 36% (1456/4039) owning at least one pet at the time of the survey. During the follow-up period 958 participants died. These included 499 deaths of cardiovascular origin. Using a Cox proportional hazard regression model adjusting for possible confounders, there was a 22% and 26% reduction in cardiovascular mortality observed among previous and current pet owners, respectively, compared to those who had never owned one. A similar non-significant trend was observed for all-cause mortality once adjusted for potential confounders.
Conclusion: Pet ownership was associated with an improved cardiovascular disease survival in a treated elderly hypertensive population.
RISK FACTORS ASSOCIATED WITH HYPERTENSIVE DISORDERS OF PREGNANCY WITHIN AN URBAN INDIGENOUS POPULATION IN SOUTHWESTERN SYDNEY
Daly ALa,b, Sriram Na,c, Woodall Cd, Selvakumar Ka,c, Briggs Kd, Garg Pa,e, Russell Ld, Yu Ma,f, Beetson Kd, Hennessy Aa,g
aDepartment of Medicine, Western Sydney University, Penrith, New South Wales, Australia; bCanberra Hospital, Garran, Australian Capital Territory, Australia; cWestmead Hospital, Westmead, New South Wales, Australia; dTharawal Aboriginal Medical Service, St Helens Park, New South Wales, Australia; eLiverpool Hospital, Liverpool, New South Wales, Australia; fNepean Hospital, Kingswood, New South Wales, Australia; gCampbelltown Hospital, Campbelltown, New South Wales, Australia
Background: The prevalence of hypertensive disorders of pregnancy (HDP) in Australia’s Indigenous women is significantly greater than the general population, the aetiology of which remains to be fully elucidated. We explored the risk factors associated with HDP for a cohort of urban Indigenous women in southwestern Sydney, Australia.
Aims: To explore the current salient risk factors for HDP in an urban Indigenous population.
Methods: The study was conducted in close conjunction with the Tharawal Aboriginal Medical Service (AMS). A quantitative questionnaire was formulated. It included participant characteristics, obstetric history and personal and family history of hypertension. Anthropometric measurements and blood pressure recordings were also documented. Women within the reproductive age range (18–45 years) were recruited in the waiting room of Tharawal AMS and at community events. Rates were compared with Australian Bureau of Statistics (ABS)-reported national rates.
Results: There were 83 participants who completed the questionnaire. The prevalence of ever having HDP in a pregnancy was 36.1%. The national reported rate (ABS) for the general population is 9.8% and for Indigenous women, 14%. The mean maternal age at first pregnancy of the sample population was 20.8 years (S.D. 3.7 years). There was a possible trend between younger maternal age at first pregnancy and HDP, although statistical significance was not achieved (P=0.066). The mean body mass index (BMI) of the sample population (n=81) was 32.2 kg/m2 (S.D. 9.5 kg/m2). The BMI did not show a statistically significant relationship with HDP (P=0.197). Of those questioned, 25.3% of women had an individual history of hypertension and 63.9% of women had a family history of hypertension. Statistical significance was achieved for the effect of family history of hypertension (OR 4.29; 95% CI 1.42–12.9; P=0.020) and individual history of hypertension (OR 15.7; 95%CI; 4.5–54.8; P<0.001) on developing HDP.
Conclusion: We found a higher prevalence of HDP in this study population compared to the national prevalence of HDP in Indigenous Australiana. Family history or individual history of hypertension were the most significant risk factors in the study population, with a possible trend for younger maternal age at first pregnancy. BMI was not identified as a risk factor for HDP in this population.
FOXO3 GENOTYPE PROTECTS AGAINST TELOMERE SHORTENING WITH AGE
Davy PMCa, Morris BJb.c.d, Willcox DCc.d.e.f, Shimabukaro Mg, Donlon TAc.d.h, Suzuki Mf, Higa Mi, Masuzaki Hj, Sata Mk, Chen Rc, He Ql, Murkofsky Rl, Lim Em, Allsopp RCa, Willcox BJc.d
aInstitute for Biogenesis Research, University of Hawaii, Honolulu, Hawaii, USA; bSchool of Medical Sciences and Bosch Institute, University of Sydney, Sydney, NSW, Australia; cDepartment of Research, Honolulu Heart Program/Honolulu-Asia Aging Study, Kuakini Medical Center, Honolulu, Hawaii, USA; dDepartment of Geriatric Medicine, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA; eDepartment of Human Welfare, Okinawa International University, Ginowan, Okinawa, Japan; fOkinawa Research Center for Longevity Science, Okinawa, Japan; gDepartment of Cardio-Diabetes Medicine, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan; hOhana Genetics, Honolulu, Hawaii, USA; iThe Diabetes and Life-Style Related Disease Center, Tomishiro Central Hospital, Okinawa, Japan; jDivision of Endocrinology, Diabetes and Metabolism, Hematology, Rheumatology (Second Department of Internal Medicine), Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan; kDepartment of Cardiovascular Medicine, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan; lPacific Health Research and Education Institute, VA Pacific Islands Medical Center, Honolulu, Hawaii, USA; mOffice of Biostatistics & Quantitative Sciences, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA
Background: Minor alleles of multiple genetic variants of FOXO3 are associated with longevity, principally via protection against CAD mortality. Telomere shortening with age may affect lifespan. Telomere length is reduced in hypertension. Genetic variation in FOXO3 is associated with blood pressure and hypertension.
Aims: To assess the effect of longevity-associated FOXO3 and APOE alleles on telomere attrition with age.
Methods: The study involved 127 Okinawan Japanese subjects aged 25–94 years. Leukocyte telomere length was determined by Southern blot analysis of terminal restriction fragments. FOXO3 and APOE genotyping was performed by PCR.
Results: We found telomere shorting of ~42 bp/year of telomeres in 84 subjects with the TT genotype of FOXO3 single nucleotide polymorphism rs28802292, but no telomere attrition in 43 carriers of the longevity-associated FOXO3 G allele. Telomerase enzyme activity did not differ between FOXO3 genotypes. Genetic variation in APOE is associated with longevity and cardiovascular disease. Telomere length did not, however, differ between APOE allele ε2 carriers, subjects with the ε3/3 genotype and allele ε4 carriers.
Conclusion: Protection against telomere attrition may be one way by which longevity associated genotype(s) of FOXO3 increase health span and lifespan.
FOXO3 LONGEVITY INTERACTOME ON HUMAN CHROMOSOME 6
Donlon TAa,b, Morris BJa,c,d, He Qa,e, Chen Ra, Masaki KHa,d, Allsopp RCb, Willcox DCa,d,f, Elliott Aa, Willcox BJa,d
aDepartment of Research, Honolulu Heart Program/Honolulu-Asia Aging Study, Kuakini Medical Center, Honolulu, Hawaii, USA; bJohn A. Burns School of Medicine, University of Hawaii Manoa, Honolulu, Hawaii, USA; cBasic & Clinical Genomics Laboratory, School of Medical Sciences and Bosch Institute, University of Sydney, New South Wales, Australia; dDepartment of Geriatric Medicine, John A. Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, USA; eVeterans Affairs Pacific Islands Health Care System, Honolulu, Hawaii, USA; fDepartment of Human Welfare, Okinawa International University, Okinawa, Japan
Background: Minor alleles of several FOXO3 polymorphisms are associated with increased lifespan, as well as lower blood pressure, less hypertension and reduced risk of death from coronary artery disease.
Aims: To determine the local genomic mechanisms by which FOXO3 exerts its health benefits.
Methods: Using leukocyte DNA from long-lived American subjects of Japanese ancestry we sequenced 7.2 Mb of chromosome 6q21 DNA surrounding FOXO3. SNPs were genotyped by Geneious®. The WashU Epigenome Browser public database and the program Juicebox were used to determine contact points.
Results: We identified all SNPs in FOXO3 and showed 41 were highly significant for longevity. Thirteen of these had predicted alterations in transcription factor binding sites. Those SNPs appeared to be in physical contact, via RNA polymerase II binding and chromatin looping, with sites in the FOXO3 promoter, and likely function together as a cis-regulatory unit. The SNPs were in a high degree of linkage disequilibrium in the Asian population, in which they define a specific longevity haplotype that is relatively common in Asians. The haplotype was less frequent in whites and virtually non-existent in blacks. We identified distant contact points between FOXO3 and neighboring genes, through long-range physical contacts via CCCTC-binding factor zinc finger protein (CTCF) binding sites, over a 7.2 Mb distance on chromosome 6. The 7.2 Mb achipelago was flanked by gene deserts. FOXO3 appeared to lie at the center of these contacts and of an early-replicating region on chromosome 6, suggesting that in addition to regulating the expression patterns of genes on other chromosomes, through its role as a transcription factor, FOXO3 may also function at the genomic level to help regulate neighboring genes by virtue of its central location in chromatin conformation.
Conclusion: We identified genotype-specific mechanisms affecting FOXO3 expression. Protective genotypes of FOXO3 form distinct conformations within the gene itself and between neighboring genes. FOXO3 is at the hub of an interacting set of genes on chromosome 6 involved in cell and disease protection.
ASSOCIATION OF IDIOPATHIC INFLAMMATORY MYOSITIS WITH STATIN EXPOSURE: A POPULATION BASED CASE CONTROL AND ECOLOGICAL STUDY
Gabb GMa,b, Caughey Gc, Ronson Sd, Ward Md, Hill CLef, Limaye Vb,g
aDiscipline of General Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia; bDiscipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia; cQuality Use of Medicines and Pharmacy Research Centre, Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Adeliade, South Australia, Australia; dSchool of Pharmacy and Medical Science, University of South Australia, Adelaide, South Australia, Australia; eDepartment of Rheumatology, The Queen Elizabeth Hospital, Woodville, South Australia, Australia; fThe Health Observatory, Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia; gRheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia
Background: Statins are widely prescribed for cardiovascular risk reduction. The muscular adverse effects associated with statin use, including myalgia and rhabdomyolysis are well recognized. Idiopathic inflammatory myositis is a rare, severe, debilitating condition, most commonly presenting with painless proximal limb girdle weakness. It requires aggressive immunosuppressive therapy and may result in permanent disability and even death. The relationship between statin use and idiopathic inflammatory myositis is less certain.
Aims: To examine the association between histologically confirmed idiopathic inflammatory myositis and prior exposure to statins.
Methods: A retrospective population based case-control study was conducted between 1990 and 2014 of all histologically confirmed cases of inflammatory myositis in adults aged 40 years and older from the South Australian Myositis Database. Data on exposure to statins were compared to controls matched 3:1 on age (within two years) and gender from the North West Adelaide Health Study. The prevalence and odds ratio (95% CI) for statin exposure were calculated.
Results: A total of 221 cases and 662 controls were included in the study. Polymyositis (n=87, 39.4%) was the most common type identified, followed by inclusion body myositis (n=66, 29.9%), dermatomyositis (n=26, 11.8%), necrotising myositis (n=24, 10.9%) and non-specific chronic inflammatory myositis (n=18, 8.1%). A total of 30.8% of cases were exposed to statins, by comparison to 21.6% for controls. Calculated OR of exposure to statins was 1.6 (95% CI 1.15–2.27; P=0.00051) and with stratification of the analysis by time of exposure the OR increased to 2.11 (95% CI 1.33–3.35; P=0.0015). The majority of cases were not exposed to concomitant interacting medications (CYP3A4 inhibitors).
Conclusion: Patients with histologically confirmed inflammatory myositis had an increased likelihood of prior statin exposure compared with a control population. This warrants further investigation in view of the increasing population exposure to statins and the severity of the disease outcome.
RELATIONSHIP BETWEEN SLEEP AND CARDIOMETABOLIC FACTORS IN YOUNG ADULTS
Hamidi Aa, Huang RCb, Beilin LJa, Burrows Sa, Eastwood PRc, Mori TAa
aDepartment of Medicine and Pharmacology, Royal Perth Hopsital, University of Western Australia, Perth, Western Australia, Australia; bTelethon Kids Institute, University of Western Australia, Perth, Western Australia, Australia; cSchool of Anatomy, Physiology and Human Biology, University of Western Australia, Perth, Western Australia, Australia
Background: Several studies have shown a relationship between sleep (especially duration) and poor cardiometabolic health in young adults. Individuals with short sleep duration have reportedly increased body mass index (BMI), waist circumference and blood pressure. However other studies have not reported such a relationship. Reasons for the discrepant findings might relate to the use of subjective methods of sleep measurement, which can be influenced by recall bias.
Aims: To examine the relationship between objective sleep characteristics and cardiometabolic risk factors in participants from the Western Australian Pregnancy Cohort (Raine) Study at 22 years of age.
Methods: Demographic, lifestyle and medical questionnaires were obtained from 975 participants that attended the Centre for Sleep Science, at the University of Western Australia. Physical assessments included weight, height and waist measurements, and blood pressure. Venous fasting blood samples were collected and analysed for glucose, insulin, total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides (TG) and high sensitivity C-reactive protein (hs-CRP). Participants were required to wear a wrist accelerometer device (GTX3) continuously for 7 days and complete a sleep diary. Raw accelerometer data were recorded in one-minute periods. Data were downloaded and analysed using the Actilife software (Actigraph 2012, Actilife 6.8). Derived measurements included total sleep time, sleep efficiency, sleep latency and Wake After Sleep Onset. Linear regression analyses were used to assess the relationships between sleep and cardiometabolic measures.
Results: Of subjects, 59% of males and 64% females had normal weight. More males were categorized as overweight and pre-hypertensive compared to females (P<0.001). No significant association with sleep (quantity and quality) was detected in either univariate or multivariate linear regression (adjusting for gender, smoking, alcohol intake and physical activity) for any cardiometabolic variables. There was no significant association between sleep (quantity and quality) and glucose, insulin, lipids and hs-CRP.
Conclusion: No association was observed between objective sleep characteristics and cardiometabolic risk factors In the study population. More studies are, however, required in this age group to verify these findings.
CARDIOVASCULAR DISEASE, MEDICATIONS, AND HEAT: WHAT PRECAUTIONARY ADVICE IS AVAILABLE?
Jeyakumaran Na, Gabb Gb, Rowett Dc, Rami Td
aUniversity of Adelaide, Adelaide, South Australia, Australia; bDepartment of Medicine, Royal Adelaide Hospital, Adelaide, South Australia, Australia; cPharmacy, The Repatriation General Hospital Daw Park, Adelaide; cPharmacy, The Repatriation General Hospital Daw Park, Adelaide, South Australia, Australia; dDepartment of General Medicine and Department of Clinical Pharmacology, Royal Adelaide Hospital, Adelaide, South Australia, Australia
Background: Global temperatures are rising, increasing the probability of population exposures to extreme heat events. Patients with cardiovascular disease may be at increased risk during extreme heat events, and cardiovascular medications may exacerbate this risk, for example, through dehydration and electrolyte imbalance, including hyponatremia. Normal cardiovascular adaptation to severe heat stress can involve an increase in cardiac output (CO) by up to 20 L/min and a shift of heated blood from the core to the peripheral circulation. An inability to increase CO results in impaired heat tolerance and increased susceptibility to heat stroke.
Aims: To review commonly used health professional medical resources in relation to heat-related precautionary advice for cardiovascular disease management and people prescribed cardiovascular medications.
Methods: We conducted a content analysis of the following: (1) Australian Therapeutic Guideline Cardiovascular Version 6; (2) Australian Medicines Handbook 2015; (3) Australian Heart Foundation Guidelines; (4) Approved Product Information for specific drugs (i.e., atenolol, metoprolol, frusemide, spironolactone, glyceryl trinitrate, perindopril, irbesartan, amlodipine, atorvastatin). These resources were searched manually for the following terms: “heat”, “weather” and “season.”
Results: No advice was found for health professionals regarding the potential effects of exposure to extreme heat in patients with cardiovascular disease, nor precautionary advice for people prescribed cardiovascular medications, except for generic storage of medicines advice.
Conclusion: Precautionary advice regarding the effects of heat in patients with cardiovascular disease and use of cardiovascular medications is not generally available.
TNF-α IN THE AREA POSTREMA ELICITS SYMPATHETIC EXCITATION TO THE HEART IN RATS
Korim WSa, Basser JRa, Elsaafien Ka, Yao STa
aFlorey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia
Background: Neuro-inflammation is a consequence of high levels of circulating cytokines commonly observed in heart failure. A leading mediator of this response is tumor necrosis factor alpha (TNF-α), the receptors for which are expressed throughout the area postrema, a circumventricular organ found in the dorsal medulla.
Aims: To determine whether activation of TNF-α receptors type 1 (TNFR1) in the area postrema increases the sympathetic drive to the heart, contributing to the detrimental effects in heart failure.
Methods: In anesthetized male Sprague-Dawley rats, we found that TNF-α increased sympathetic nerve activity to both the heart and blood vessels in the periphery.
Results: Microinjection of TNF-α augmented (P<0.01, n=5) cardiac (+53±12 %) and renal (+34±7 %) sympathetic nerve activities, resulting in rises (n=7) in arterial blood pressure (Δ: +8.3±3.7 mmHg; P<0.05) and heart rate (Δ: +27.1±9.2 bpm; P<0.01). All responses were attenuated by prior microinjection of TNFR1 antibody in the same site.
Conclusion: Together the results suggest that activation of TNFR1 in the area postrema enhances the detrimental hemodynamic effects in heart failure by predominantly increasing cardiac sympathetic nerve activity.
NON-INVASIVE ASSESSMENT OF CENTRAL, AORTIC SYSTOLIC BLOOD PRESSURE VARIABIBLITY AND BARORECEPTOR SENSITIVITY: COMPARISON TO MEASURES USING A PERIPHERAL PULSE
Kouchaki Za, Butlin Ma, Qasem Aab, Alberto APa
aDepartment of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, North Ryde, New South Wales, Australia; bAtCor Medical, Ryde, New South Wales, Australia
Background: The difference between aortic and peripheral (e.g., brachial) systolic blood pressure (SBP) is heart rate dependent. Traditionally, SBP variability and baroreceptor sensitivity (BRS) is calculated from a peripheral pulse, yet the organs of impact and the baroreceptors are located centrally.
Aims: To ascertain whether there is a difference between SBP variability and BRS estimated using a peripheral pulse or a derived, central aortic pulse.
Methods: Continuous finger blood pressure (Nexfin, Edwards Life Sciences) and electrocardiogram were measured in 33 subjects (age 20–66 years; 17 female) over a 10-minute interval in the supine position. A generalized transfer function was used to calculate central aortic pressure from the finger blood pressure waveform. BRS was estimated using both the sequence technique and spectral analysis and SBP variability was calculated, all using both the finger and the calculated aortic blood pressure.
Results: Aortic SBP variability was highly correlated with peripheral SBP variability (R2=0.96, P<0.001). Peripheral SBP variability was, however, greater than aortic SBP variability at higher levels of variability (slope=0.94). The same trend was seen in BRS calculated by the sequence technique, with BRS calculated using the peripheral pulse being correlated with calculation by the aortic pulse (R2=0.92, P<0.001) but higher at higher values of BRS (slope –0.82). Spectral techniques of BRS estimation showed the same trend but the overestimation was greater in the low frequency range (0.05–0.15 Hz, slope=0.67, R2=0.93, P<0.001) than in the high frequency range (0.15–0.4 Hz, slope=0.86, R2=0.86, P<0.001).
Conclusion: Given the heart rate-dependent amplification of the arterial pulse between the aorta and peripheral sites, both SBP and BRS calculated using the peripheral pulse differ from that calculated using the aortic pulse, with the magnitude of the difference being greater at higher values of SBP and BRS.
EFFECTS OF MOXONIDINE AND LOW-CALORIE DIET IN YOUNG OVERWEIGHT MALES
Lambert EAa, Sari CLa, Head GAa, Grima Ma, Eikelis Na, Straznicky Na, Schlaich MPb, Dixon JBa, Lambert GWa
aBaker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia; bFaculty of Medicine, Dentistry and Health Sciences, University of Western Australia, Western Australia, Australia
Background: Elevated sympathetic nervous system activity in overweight individuals is believed to play a detrimental role in metabolic and cardiovascular health in early adulthood.
Aims: To compare the effects of a treatment with either a low-calorie diet (LCD), a sympatholytic agent or a combination of both on hemodynamic and metabolic parameters and renal and endothelial function.
Methods: Overweight (body mass index > 25 kg/m2), young (18–30 years), otherwise healthy males were randomly allocated to receive either a low calorie diet (LCD; n=10), moxonidine (MOX; n=10; 0.4 mg/day), a combination of both (LCD+MOX; n=11) or to act as controls (CONT; n=6) for a period of 6 months. Muscle sympathetic nerve activity (MSNA) was measured by microneurography, endothelial function was assessed using digital pulse tonometry, and renal function was assessed using creatinine clearance derived from the Cockcroft Gault formula before and after intervention.
Results: Weight loss occurred in the LCD and LCD+MOX (–7.5±1.9 and –7.6±1.9 kg). MSNA was significantly decreased in the LCD, MOX and LCD+MOX groups (–14±3, –14±3 and –14±2 bursts per 100 heartbeats, respectively) and this was associated with a decrease in systolic blood pressure (–8.9±3.3, –8.8±5.5 and –9.8±3.2 mmHg, respectively). All other metabolic parameters for the LCD, CON and MOX groups remained unchanged. Endothelial function remained unchanged in all groups. In the LCD+MOX group, additional benefits included decreased waist circumference (–8.3±1.9 cm), decreased total cholesterol (–0.78±0.23 mmol/L), LDL cholesterol (–0.49±0.16 mmol/L), fasting insulin (–6.5±2.8 mmol/L) and attenuated glomerular hyperfiltration (from 187±4 to 167±4 mL/min).
Conclusion: The addition of moxonidine to a LCD may have beneficial effects on the metabolic profile and renal function of overweight young males.
THE TRANS-GENERATIONAL OBESITY RELATED HYPERTENSION: NEURONAL PLASTICITY
Lim Ka, Burke SLa, Armitage JAb, Head GAa,c
aBaker IDI Heart & Diabetes Institute, Melbourne, Victoria, Australia; bSchool of Medicine (Optometry), Deakin University, Waurn Ponds, Victoria, Australia; cDepartment of Pharmacology, Monash University, Clayton, Victoria, Australia
Background: Obesity during pregnancy is associated with a greater risk of developing obesity and hypertension in the offspring later in life. The ventromedial hypothalamus (VMH) is a key centre of energy homeostasis, hemodynamic and sympathetic tone to renal vasculature. It is possible that exposure to over-nutrition during development alters the activity of the neurons in the VMH, amplifying sympathetic output leading to hypertension in the offspring. We assessed the contribution of leptin and melanocortin (MC) signaling pathway in the VMH of adult offspring that were born from obese mothers.
Aims: To determine whether maternal obesity plays a role in programming leptin and melanocortin signaling pathway in the VMH of adult offspring.
Methods: Female New Zealand White rabbits were fed a high fat diet (13%; mHFD) or a control diet (4%; mCD) during pregnancy and lactation. Offspring received CD after weaning. All offspring received a VMH cannula and a renal nerve recording electrode. Experiments were conducted in conscious rabbits and mean arterial pressure (MAP), heart rate (HR) and RSNA were measured. Rabbits received increasing doses of α-melanocortin stimulating hormone (α-MSH; 0.3 and 1 nmol), a melanocortin receptor antagonist (SHU9119; 0.02 and 0.04 nmol) or leptin receptor antagonist (5 and 10 μg).
Results: mHFD rabbits exhibited higher MAP and RSNA than mCD rabbits (P<0.05). α-MSH injection into the VMH increased MAP (+6%), HR (+12%) and RSNA (+80%) and SHU9119 reduced MAP (–7%) in mHFD rabbits. Leptin receptor antagonist normalized hypertension in mHFD rabbits (P<0.05). mCD did not respond to any drug injections into the VMH.
Conclusion: Exposure to over-nutrition during development alters leptin and MC signaling pathway in the VMH of the offspring.
THE OPTIMAL AUTOMATED IN-CLINIC BLOOD PRESSURE MEASURE
Moore MNa, Black JAa, Dwyer Nb, Jose Ma,b, Nelson Ma, Picone DSa, Schultz MGa, Sharman JEa
aMenzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia; bRoyal Hobart Hospital, Hobart, Tasmania, Australia
Background: There is clinical interest in automated in-clinic blood pressure (AutoBP) as an alternative to ambulatory BP (ABP). AutoBP involves repeated, unobserved clinic BP measures, but there is variability among protocols regarding the number of readings and measurement duration. The best AutoBP protocol is unknown but needs to be determined for clinical feasibility.
Aims: To determine the optimal AutoBP protocol that has best concordance with daytime ABP and can be achieved in the shortest duration with the fewest measures.
Methods: Patients (n=117; mean age 61.5±12.5 years; 52.5% female) referred to a specialist BP clinic underwent AutoBP in a quiet room alone. Eight BP measurements were taken starting immediately after sitting and then at 2-minute intervals (15 minutes total). The optimal AutoBP protocol compared with daytime ABP was defined by the smallest mean difference and highest intra-class correlation coefficient (ICC). The same BP device (Mobil-o-graph, IEM) was used for both AutoBP and daytime ABP.
Results: Average 15-minute AutoBP and daytime ABP were 138.4±18.1/84.8±12.2 and 140.9±15.2/86.2±10.6 mmHg, respectively. The optimal AutoBP protocol was derived within six minutes by the average of two measures taken after two and four minutes of seated rest (systolic BP: mean difference = 0.3 (95%CI –3.0, 2.4) mmHg; P=0.84; ICC=0.80; diastolic BP: mean difference = –0.42 (95%CI –2.0,1.1) mmHg; P=0.60; ICC=0.85). AutoBP measures taken before six minutes tended to overestimate daytime ABP, but measures taken after this time underestimated daytime ABP (whether as a single BP or the average of more than one BP reading).
Conclusion: A clinically feasible AutoBP protocol that best concords with daytime ABP is achievable within a short duration and using a small number of BP measures.
CAN LONG-TERM ENDURANCE EXERCISE CHANGE microRNA PROFILES AND PREVENT CARDIOVASCULAR DISEASE?
Prestes PRa, O’Brien BJa, Charchar FJa
aFaculty of Science and Technology, Federation University, Ballarat, Victoria, Australia
Background: Exercise improves cardiovascular fitness and reduces the incidence of cardiovascular disease (CVD). MicroRNAs (miR) are small non-coding RNA molecules that regulate gene expression and cardiovascular physiology.
Aims: We investigated the effects of exercise on microRNA signatures in leukocytes.
Methods: We sequenced total microRNAs from leukocytes of 12 long-term endurance athletes and 12 healthy age-matched controls using the Illumina TruSeq Small RNA library prep on MiSeq. Our findings were validated in a larger group of 68 athletes and 58 controls using qPCR. We also investigated microRNA abundance before and after a short bout of exercise leading to exhaustion in 15 healthy individuals.
Results: Mature microRNA miR-30e was up-regulated in athletes in our total microRNA investigation (P<0.05; FC=8), validation study (P<0.05; FC=1.55) and after a short bout of exercise (P<0.05; FC=1.43). miR-30e is down-regulated in cardiomyopathies and the up-regulation of this microRNA in athletes could be cardioprotective and caused by exercise. Three novel microRNAs were only found in athletes and one in controls. The possible targets for these microRNAs are still unknown and need to be investigated.
Conclusion: Long-term endurance and short strenuous exercise influences microRNA profiles helping prevent or protect against CVD.
HIGH DENSITY LIPOPROTEINS AND PRESSURE-INDUCED INFLAMMATION
Putra MRAa, Shihata WAa,b, Andrews KLa, Sviridov Db, Murphy AJb, Chin-Dusting JPFa
aCardiovascular Disease Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia; bBaker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia
Background: In Australia, cardiovascular disease accounts for ~50,000 deaths/year. Notably, 64% of the adult population have >3 modifiable risk factors for cardiovascular disease (CVD). Accordingly, assessment of absolute CV risk, based on the patient’s gender, age, systolic blood pressure (BP), smoking status, total and high density lipoprotein (HDL)-cholesterol, type 2 diabetes and the presence of left ventricular hypertrophy, is currently widely adopted. Although the goal is to reduce absolute CVD risk, this is usually by managing individual risk factors such as high BP and lipid levels. Since both have a continuous association with CVD events, moderate alterations in several factors may however be more effective than a major change in any one factor.
Aims: To explore whether promoting cholesterol efflux or uptake influences pressure-induced leukocyte adhesion.
Methods: Carotid arteries were isolated from male 8 week-old Sprague Dawley rats and mounted on a specialized pressure myograph to record leukocyte adhesion in real time. Inflammation was induced by the exertion of high intraluminal pressure after incubation (1 h) or HDL (50 μg/ml), oxidized LDL (oxLDL; 50 μg/ml) or control. Adhesion molecule and inflammatory cytokine gene expression (intercellular adhesion molecule-1 [ICAM-1], monocyte chemoattractant protein-1 [MCP-1] and interleukin-6 [IL-6]) was assessed by real time-PCR.
Results: High intraluminal pressure (120 mmHg) induced an increase in leukocyte adhesion to the endothelium, indicative of an inflammatory response (0 vs. 120 mmHg: 11±1 vs. 18±4 leukocytes per field of view; n ≥ 4; P=0.1). HDL had no significant effect on unpressurized vessels. However, in vessels pre-incubated with HDL for 1 h prior to pressurization, there was a significant reduction in leukocyte adhesion (120 mmHg vs. HDL + 120 mmHg: 18±4 vs. 8±2 leukocytes per field of view; n ≥ 4; P<0.05). Measuring the expression of endothelial adhesion markers mirrored this effect. Interestingly, oxidized low density lipoprotien (oxLDL) augmented leukocyte adhesion and endothelial activation.
Conclusion: We found that HDL reduced high intraluminal pressure-induced inflammation in rat carotid arteries, while oxLDL potentiated inflammation. This study suggests that alterations in lipoprotein species influence the inflammatory response of vessels in the setting of hypertension.
PLASMA ACE2 ACTIVITY IS ELEVATED IN PATIENTS WITH SIGNIFICANT CORONARY ARTERY DISEASE, BUT IS NOT ASSOCIATED WITH LONG-TERM MAJOR ADVERSE CARDIOVASCULAR EVENTS
Ramchand Ja,b, Patel SKa, Srivastava Pa,b, Farouque Oab, Velkoska Ea, Burrell LMa,b
aDepartment of Medicine, University of Melbourne, Austin Health, Heidelberg, Victoria, Australia; bDepartment of Cardiology, Austin Health, Heidelberg, Victoria, Australia
Background: Angiotensin converting enzyme 2 (ACE2) is an important counter-regulator of the renin-angiotensin system. In patients with heart failure, elevated plasma ACE2 activity predicts adverse outcomes. It is unknown whether plasma ACE2 activity is elevated in patients with significant coronary artery disease (CAD) or if it is associated with major adverse cardiovascular events (MACE).
Aims: To determine whether plasma ACE2 activity is increased in patients with CAD and if levels predict MACE.
Methods: Plasma ACE2 activity was measured in a prospectively recruited cohort of patients (n=77) with significant CAD (determined by coronary angiography) and compared to healthy controls (n=17). Time to first occurrence of MACE (cardiovascular death, myocardial infarction, stroke, heart failure) was investigated in the CAD cohort over a mean follow-up period of 5.3±1.6 years.
Results: The median (25th, 75th quartiles) plasma ACE2 activity was significantly higher (P<0.001) in patients with CAD compared to healthy controls (29.3 [95% CI 22.0, 41.4] vs. 14.3 [11.4, 23.5] pmol/mL/min). Among the patients with significant CAD, 50 patients (65%) presented with an acute coronary syndrome (ACS) and 27 (35%) had stable angina. Plasma ACE2 activity was not significantly different between those presenting with ACS compared to stable angina (29.8 [23.1, 45.1] vs. 27.1 [18.7, 40.5] pmol/mL/min; P=0.69). There were 31 MACE (40%) over the follow-up period. On Kaplan-Meier analysis, patients with ACS had an increased incidence of MACE compared to those with stable angina (log-rank test, P=0.008). On Cox proportional hazard analysis, troponin I level >99th percentile (HR 3.7; 95% CI 1.3–10.8; P=0.017) was the only independent predictor of MACE after adjustment for age, log-transformed plasma ACE2 activity, abnormal renal function and abnormal left ventricular ejection fraction.
Conclusion: Plasma ACE2 activity is increased in patients with significant CAD, but is not associated with long-term adverse cardiovascular outcomes. Further clinical studies are needed in patients with non-significant CAD to determine if plasma ACE2 activity is increased, and to determine whether ACE2 predicts adverse cardiovascular events in patients with early atherosclerosis.
INCREASED LARGE ARTERY STIFFNESS AND IMPAIRED BAROREFLEX SENSITIVITY INDEPENDENTLY PREDICT EXAGGERATED EXERCISE BLOOD PRESSURE: A POPULATION-BASED ANALYSIS FROM THE PARIS PROSPECTIVE STUDY III
Sharman JEa,b, Jouven Xa,c,d, Laurent Sa,c,e, Perier MCa,c, Boutouyrie Pa,c,e, Empana JPa,c
aINSERM, U970, Paris Cardiovascular Research Center, Department of Epidemiology, Paris, France; bMenzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia; cUniversité Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, France; dAssistance Publique-Hôpitaux de Paris, Georges Pompidou European Hospital, Cardiology Departments, Paris, France; eAssistance Publique-Hôpitaux de Paris, Georges Pompidou European Hospital, Pharmacology Departments, Paris, France
Background: People with normal resting blood pressure (BP) but with an exaggerated BP response to submaximal exercise have adverse cardiovascular outcomes. Mechanisms of this association are unknown but could be explained through increased large artery stiffness and/or impaired baroreflex sensitivity (BRS).
Aims: To determine the associations of carotid stiffness and carotid BRS with exercise BP.
Methods: Ausculatory BP was recorded at rest and immediately following an exercise step-test among 8,976 adults aged 50–75 years from the Paris Prospective Study III. Carotid artery stiffness was measured by the cross-sectional distensibility coefficient using ArtLab echotracking. BRS (low frequency gain) was calculated from carotid distension rate and heart rate using fast Fourier transformation and cross-spectral analysis. A threshold of ≥ 150 mmHg defined exaggerated exercise BP based on previous data. Normal resting BP was < 140/90 mmHg (± antihypertensive treatment).
Results: Participants with exaggerated exercise BP had significantly higher carotid stiffness (mean±SD 7.35±1.38 vs 6.77±1.25 m/s; P<0.001) but lower BRS (median(Q1,Q3); 0.10(0.06,0.16) vs. 0.12(0.08,0.19) (ms2/mm)2 x 108; P<0.001) compared to those with normal exercise BP. Both carotid stiffness (OR 1.14(95% CI 1.09, 1.20) per 1 m/s; P<0.001) and BRS (OR 0.83 (0.78,0.88) per 1SD; P<0.001) were significantly associated with exaggerated exercise BP among participants with normal resting BP, independent of multiple covariables including age, sex, body mass index and antihypertensive medications.
Conclusion: Both increased carotid stiffness and impaired baroreflex sensitivity independently predict exaggerated exercise BP among people with normal resting BP irrespective of antihypertensive treatment.
ARTERIAL STIFFNESS INDEX BETA AND CARDIO-ANKLE VASCULAR INDEX INHERENTLY DEPEND ON BLOOD PRESSURE, BUT CAN BE READILY CORRECTED
Spronck Ba,b, Avolio APb, Tan Ib, Butlin Mb, Reesink KDa, Delhaas Ta
aDepartment of Biomedical Engineering, Cardiovascular Research Institute Maastricht (CARIM) School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands; bDepartment of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, North Ryde, New South Wales, Australia
Background: Arterial stiffness index β and cardio-ankle vascular index (CAVI) are widely accepted for quantification of the intrinsic exponent (β0) of the blood pressure (BP)-diameter relationship. CAVI and β assume an exponential relationship between pressure (P) and diameter (d).
Aims: (1) to demonstrate that, under this assumption, β and CAVI as currently implemented are inherently BP-dependent; and (2) to provide corrected, BP-independent forms of CAVI and β.
Methods: In the intrinsic arterial BP-diameter relationship , usually reference BP (Pref) and reference diameter (dref) are substituted with diastolic BP and diastolic diameter to accommodate measurements. Consequently, the resulting exponent (stiffness index β) is not equal to the intrinsic, pressure-independent β0, but instead varies with BP. CAVI does not only suffer from this “reference pressure” effect, but also from a linear approximation of . We derived corrected forms of β and of CAVI (CAVI0) that do not change with BP and represent the pressure-independent β0. To further substantiate the BP effect on CAVI in a typical follow-up study, we realistically simulated patients (n=161) before and following BP-lowering “treatment” (assuming no follow-up change in intrinsic β0 and therefore in actual P-d relationship).
Results: As an example, in a person with β0=7, an increase of systolic/diastolic BP from 110/70 to 170/120 mmHg increased β by 8.1% and CAVI by 14.3%. In our simulated patient study, lowering BP from 160±14/111±11 to 120±15/79±11 mmHg (P<0.001) resulted in a significant CAVI decrease (8.1±2.0 to 7.7±2.1; P=0.008); CAVI0 did not change (9.8±2.4 and 9.9±2.6; P=0.499).
Conclusion: Stiffness index β and CAVI as currently implemented are inherently BP-dependent, potentially leading to erroneous conclusions in arterial stiffness trials. BP-independent forms of β and CAVI are presented to readily overcome this problem.
EFFECTS OF SALT SUPPLEMENTATION ON microRNA EXPRESSION IN TYPE 2 DIABETES
Tai Ja,b, Clarke Ma, Baqar Sa, Hachem Mb, Kantharidis Pc, Churilov Ld, MacIsaac Rb,e, Jerums Ga,b, Ekinci EIa,b
aEndocrine Centre of Excellence, Austin Health, Heidelberg Repatriation Hospital, Heidelberg, Victoria, Australia; bDepartment of Medicine, University of Melbourne, Melbourne, Victoria, Australia; cBaker IDI Heart and Diabetes Institute, Melbourne, Victoria, Australia; dFlorey Institute of Neuroscience and Mental Health, University of Melbourne, Melbourne, Victoria, Australia; eDepartment of Endocrinology & Diabetes, St. Vincent’s Hospital, Melbourne, Victoria, Australia
Background: The benefits of salt restriction in type 2 diabetes mellitus (T2DM) have been challenged given recent observational and experimental research suggesting an association between increased cardiovascular mortality and reduced dietary salt intake. Mechanistic studies to explain this paradoxical finding are limited. MicroRNA (miRNA) are non-coding RNAs linked to T2DM and its vascular complications. MicroRNAs-27a, 126, 221 and 320a are considered surrogate markers for endothelial dysfunction. The effect of salt supplementation on miRNA expression has not previously been investigated in patients with T2DM. We hypothesized that salt supplementation compared to placebo would upregulate miR-126 and downregulate miR-27a, miR-221 and miR-320a.
Aims: To determine the effect of salt supplementation on the expression of miRNAs in patients with T2DM and habitual low-moderate salt intake.
Methods: Participants in this pilot prospective crossover study, conducted at a university teaching hospital, were recruited from a diabetes outpatient clinic. Participants (n=19) with low-moderate habitual dietary salt intake determined by 24-h urinary collection (corrected sodium excretion less than 150 mmol in 2 out of 3 collections) were randomized to salt supplementation (100 mmol NaCl/24 h over 3 weeks) or placebo. Platelet-free plasma samples collected post-NaCl supplementation (n=19) and post-placebo (n=19) were analyzed for microRNA expression utilizing a protocol that was optimized for the extraction of miRNA then quantified by real-time PCR. Expression was compared to an endogenous control.
Results: From the 38 patient samples that were analysed, miRNAs-27a, 126, 221 and 320a were expressed at a detectable level in 18 samples from 9 patients following salt and placebo supplementation, respectively. Logarithmic transformation was applied for non-parametric data and Wilcoxon signed-rank statistical analysis was performed. No significant differences in miRNA expression between salt and placebo were demonstrated; miR-320a (P=0.59), miR-221 (P=0.76), miR-126 (p=0.44), miR-27a (P=0.68).
Conclusion: In this pilot study, we demonstrated the feasibility of detecting microRNA expression from plasma samples of patients with diabetes. However, we found no significant difference in miRNA expression with or without salt supplementation. This proof-of-concept study may provide a platform for larger studies aimed at elucidating the relationship between miRNA and vascular disease in T2DM.
HEART RATE DEPENDENCY OF ARTERIAL STIFFNESS: UNDERLYING MECHANISMS RELATED TO FREQUENCY DEPENDENCY OF ARTERIAL ELASTICITY
Tan Ia, Xiao Hb, Butlin Ma, Avolio APa
aDepartment of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, North Ryde, New South Wales, Australia; bChongqing Key Laboratory of Modern Photoelectric Detection Technology and Instrument, School of Optoelectronic Information, Chongqing University of Technology, Chongqing, China
Background: It has been established that the stiffness of large arteries has a dependency on acute heart rate (HR) changes. However, possible mechanisms behind this HR dependency are harder to establish.
Aims: To explore a plausible mechanism by which HR exerts an influence on arterial stiffness.
Methods: Using a computerized transmission line model of the human arterial tree, effects of HR on aortic arch to femoral pulse wave velocity (afPWV) were determined with elasticity of the arterial segments modelled with varying degrees of frequency dependence between 0 to 20 Hz. Magnitude of the elasticity was varied as a proportion of the particular segment’s static elastic modulus.
Results: In scenarios in which the arterial wall elasticity had low to zero frequency dependence, afPWV was shown to decrease with HR. As the degree of frequency dependence increased, an increase in afPWV with increasing HR was observed. The critical frequency, defined as the frequency where arterial wall elasticity reached 80% of the static elastic modulus, above which HR was shown to positively influence afPWV, was approximately 3 Hz. The change in afPWV with increasing HR plateaued at around 0.06 m/s per 10 bpm increase in HR as the degree of frequency dependence was increased to above 9 Hz.
Conclusion: The magnitude of the frequency dependency of arterial wall elasticity alters measures of large arterial stiffness across physiological ranges of HR. This could be a partial mechanism through which large artery stiffness changes with HR. Physiological studies are required to confirm this mechanism.
POWER SPECTRUM ANALYSIS AS A MEASURE OF VASCULAR REACTIVITY: EXPLORING NEURAL CONTROL OF CARDIOVASCULAR FUNCTION
Ucak Sa, Lattimore JDb, Pilowsky PMc
aDepartment of Physiology, University of Sydney, Sydney, New South Wales, Australia; bDepartment of Medicine, University of Sydney, Sydney, New South Wales, Australia; cHigh Blood Pressure Group Heart Research Institute, Sydney, New South Wales, Australia
Background: Non-invasive methods are valuable in order to estimate vascular reactivity as well as study physiology and pathophysiological conditions such as heart failure. Power spectral analysis is used to convert data from the time domain into the frequency domain using a fast Fourier transform (FFT) algorithm. Vascular reactivity governs the state of dilation or constriction of muscular resistance arterioles, which in turn determine blood flow to different vascular beds in response to changes detected by the autonomic nervous system. Previous work suggests that changes in total peripheral resistance and cardiac output are reflected by fluctuations in power of the low frequency band of systolic blood pressure (SBP), since this band is most affected by sympathetic blockade.
Aims: To estimate the neural control of cardiovascular function in older male heart failure patients using power spectrum analysis as a measure of vascular reactivity.
Methods: Continuous, non-invasive blood pressure recordings were obtained using the Nexfin® apparatus in the supine and standing positions for older males (> 65 years of age) with heart failure (n=7), and in age-matched controls (n=8). Spike2 software was used to extract a waveform representing SBP variability. Power spectral analysis was used to decompose this complex, periodic waveform into its component waves using an FFT algorithm. The area under curve value for the low frequency (LF) band (0.04–0.15 Hz) was normalized against the difference between total power of the spectrum and the very low frequency band (≤ 0.04 Hz).
Results: Patients with heart failure displayed significantly lower LF-SBP (n=7; 22.2±1.8; P<0.05) compared with age-matched controls (n=8; 33.6±2.2). Heart failure patients also had lower mean SBP (n=8; 111.2±5.3) compared to age-matched controls (n=8; 129.6±5.3)
Conclusion: Our results indicate that the low frequency band (0.04–0.15 Hz) power of male heart failure patients is significantly lower than the control group. This suggests a decrease in efferent control of resistance arterioles. Therefore, power spectral analysis of SBP variability appears to be a powerful non-invasive tool that can be used to measure vascular reactivity. We speculate that the use of this measure would be a valuable addition to available clinical measures of the success, or failure, of management of cardiovascular disease.
SEX DIFFERENCES IN OUTCOME AFTER PERMANENT FOCAL CEREBRAL ISCHEMIA
Uong Sa, Kim HAa, Sobey CGa
aDepartment of Pharmacology, Monash University, Clayton, Victoria, Australia
Background: Stroke incidence is lower in young females than age-matched males. Females appear, however, to experience worse long-term outcomes. Dampening of the immune system after stroke leaves the patient more susceptible to infections, but the effect of sex on this phenomenon is unknown. A key estrogen receptor, the G-protein coupled estrogen receptor (GPER), exhibits sex-dependent neuroprotective effects after stroke and could potentially influence immunosuppression.
Aims: To test whether a sex difference exists in outcomes after permanent focal cerebral ischemia, and if estrogen-mediated activation of GPER is involved.
Methods: Brain infarct volume and bacterial infection in lungs were assessed 24 h after permanent middle cerebral artery occlusion (pMCAO) in female (n=41) and male (n=20) mice. GPER agonist (G-1) or vehicle were administered to ovariectomized female mice immediately before induction of pMCAO and infection levels were assessed 23 h later.
Results: Higher mortality was observed in females than males (27% vs. 15%). No sex difference was detected in infarct size, mortality or bacterial infection. Stroke, however, decreased spleen weight selectively in females (n=14–28; P<0.01). G-1 worsened bacterial infection in females (n=4–7; P<0.0001) with no effect on infarct size.
Conclusion: Independent of the degree of brain injury, females suffer greater mortality after permanent focal ischemia. Furthermore, a GPER agonist increases infection levels after stroke in females in the absence of endogenous estrogen. More studies are needed to elucidate whether GPER modulation could be exploited for post-stroke neuroprotective therapy in older females.
NIGHT-TIME AMBULATORY BLOOD PRESSURE IS THE BEST PRE-TREATMENT BLOOD PRESSURE PREDICTOR OF 11-YEAR MORTALITY IN OLDER HYPERTENSIVES
Wing LMa, Chowdhury EKb, Reid CMb,c, Beilin LJd, Brown MAe
aSchool of Medicine, Flinders University, Adelaide, South Australia, Australia; bCentre of Cardiovascular Research and Education in Therapeutics, Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Victoria, Australia; cSchool of Public Health, Curtin University, Perth, Western Australia, Australia; dDepartment of Medicine, University of Western Australia and Royal Perth Hospital, Perth, Western Australia, Australia; eSt George Hospital Clinical School, University of New South Wales, Kogarah, New South Wales, Australia
Background: Population-based and prospective observational studies have demonstrated a stronger relationship between ambulatory blood pressure (ABP) and subsequent cardiovascular events than for clinic blood pressure (BP), and some of these studies suggest that this relationship is strongest for night-time BP. Only one previous study has examined these relationships in the context of a clinical trial, demonstrating that ABP was a better predictor of outcome than clinic BP in placebo-treated but not actively-treated participants.
Aims: To test the hypothesis, in elderly hypertensives from the Second Australian National Blood Pressure study (ANBP2), that at study entry ABP was a better predictor of long-term mortality than clinic BP.
Methods: ANBP2 was a comparative outcome trial of different BP-lowering treatment regimens in 6,083 off-treatment or previously untreated hypertensives aged 65–84 years. In the ABP sub-study, at study entry participants had ABP recordings in addition to nurse-performed standardized clinic BP measurements. Cox proportional hazards analysis with relevant adjustments assessed the relationships between both clinic BP and ABP at study entry and 11 year all-cause and cardiovascular mortality (including both in-trial and post-trial periods). Both treatment arms were pooled.
Results: Of participants, 702 out of 735 in the ABP sub-study had “successful” ABP recordings at study entry. Over a median period of 10.8 years, including 6.7 years post-trial follow-up, 167 of these 702 participants died, with 82 cardiovascular deaths. “Night” ambulatory systolic BP and pulse pressure were the best significant BP predictors at study entry of “11-year” cardiovascular mortality (hazard ratios [HR] 1.26; 95% CI 1.10–1.45; P=0.001 and 1.18; 1.06–1.31; P=0.003), respectively) and all-cause mortality (HR 1.15; 1.05–1.28; P=0.005) and 1.09; 1.10–1.31; P=0.029, respectively) compared to other 24-hour ABP components (“24 hour” and “day”), and to clinic BP, which was not a significant predictor of outcome.
Conclusion: In untreated or off-treatment elderly hypertensives participating in a clinical outcome trial, post-trial all cause or cardiovascular deaths were significantly related to ABP measured at study entry, particularly to night-time systolic BP and pulse pressure, but not to clinic BP.
THE INVOLVEMENT OF KIDNEY DNA METHYLATION IN BLOOD PRESSURE REGULATION
Wise IAa, Prestes Pa, Tomaszewski Mb, Charchar FJa,c
aFaculty of Science and Technology, Federation University, Ballarat, Victoria, Australia; bDivision of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK; cDepartment of Physiology, University of Melbourne, Melbourne, Victoria, Australia
Background: Increasing evidence suggests that epigenetic modifications such as DNA methylation (5mC) is important to the development of essential hypertension, and that changes in DNA methylation of blood cells are associated with blood pressure (BP). So far there have been no studies of epigenetic changes in the kidney – an important effector organ in BP regulation.
Aim: To compare loci-specific methylation in the kidney between normal and hypertensive subjects.
Methods: We used 96 human renal samples from the TRANScriptome of RenaL HumAN TissueE (TRANSLATE) Study to measure DNA methylation. TRANSLATE consists of carefully characterized collections of “apparently healthy” specimens of human kidneys. DNA was extracted from kidney tissue using the DNeasy blood and tissue Qiagen kit and loci-specific methylation status was determined using Infinium HumanMethylation 450K array (Illumina®, Australia).
Results: We found 505 (P<0.01) loci were differentially methylated between hypertensive and normotensive individuals. Included in these loci were genes previously associated to blood pressure modulation (BAT4, CASZ1, DNM3, FGGY, HEXIM2, INSR, KCNJ11, LY6G5B, PPL, SIK1, TBC1D1, THBS2, MAP3K11, EHBP1L1 and XKR6) in genome-wide association studies. Of these, one gene (NR3C2) is associated with monogenic forms of hypertension. The variants identified implicate biological pathways related to aldosterone-regulated sodium reabsorption, vasopressin-regulated water reabsorption and vascular smooth muscle contraction.
Conclusion: DNA methylation in the kidney is an important molecular mechanism contributing to BP variation and hypertension in humans.
QUANTITATIVE mRNA ANALYSIS OF THE THIAZIDE-SENSITIVE SODIUM CHLORIDE COTRANSPORTERS IN URINARY EXOSOMES FROM NORMAL CONTROLS AND PATIENTS WITH PRIMARY ALDOSTERONISM
Wu Aa, Wolley MJa, Xu Sa, Gordon RDa, Stowasser Ma
aEndocrine Hypertension Research Centre, University of Queensland School of Medicine, Greenslopes and Princess Alexandra Hospitals, Greenslopes and Wooloongabba, Queensland, Australia
Background: The thiazide-sensitive sodium chloride cotransporter (NCC) is responsible for the major sodium chloride reabsorption in the distal convoluted tubule of the renal nephron. As an aldosterone-modulated cotransporter, NCC regulation by aldosterone remains unclear. Our preliminary data show, in humans, mineralocorticoid administration acutely increased NCC abundance, NCC phosphorylation and WNK4 abundance by 3.68-fold, 2.73-fold, and 3.23-fold, respectively (P<0.01). These results suggested that mineralocorticoid administration is associated with a rapid increase in abundance of NCC and its activated form, possibly via the WNK pathway.
Aims: To establish and evaluate a novel approach for quantification of NCC mRNA in human urinary exosomes, and to investigate the relationship between NCC mRNA expression and the increased NCC protein abundance previously reported by us to be induced by fludrocortisone administration in primary aldosteronism (PA) patients.
Methods: Morning spot urine samples from non-hypertensive volunteers were collected and stored at –80°C for method optimization. Urinary exosomes were harvested by progressive ultracentrifugation, and NCC abundance was quantified by Western blot. Exosomal total RNA was isolated by total exosome RNA and a protein isolation kit. NCC expression was determined and quantified by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR).
Results: Among non-hypertensive volunteers, NCC mRNA analysis for NCC expression (Ct=35.0, CV=0.087; n=8) melt curves suggest the product is consistent with NCC mRNA isolated from kidney tissue. In method optimization, the minimum urine volume required for exosome RNA isolation is 200 mL. The exosome pellets obtained required resuspending in 200 μL phosphate buffered saline (PBS) and 30 μL of elution buffer is required to recover exosome RNA. The minimum RNA required for RT-qPCR is 205 ng. In ongoing studies, the optimized method of quantitative analysis is being applied to hypertensive patients with raised plasma aldosterone/renin ratios who are undergoing fludrocortisone suppression testing (100 μg q6h) in order to diagnose or exclude PA, and NCC expression and NCC abundance will be compared.
Conclusion: Total RNA in human urinary exosomes has been successfully isolated by the optimized methods. This will help in the exploration of molecular mechanisms that govern NCC expression and abundance, including those induced by mineralocorticoids, and may ultimately aid in the clinical diagnosis and treatment of PA.
CHANGES IN LEFT VENTRICULAR EJECTION TIME BUT NOT PERIPHERAL RESISTANCE ALTER CAROTID AND FEMORAL WAVEFORM SHAPE, IMPACTING ON MEASURED CAROTID-FEMORAL PULSE WAVE VELOCITY: A MODELLING STUDY
Xiao Ha, Tan Ib, Butlin Mb, Avolio APb
aChongqing Key Laboratory of Modern Photoelectric Detection Technology and Instrument, School of Optoelectronic Information, Chongqing University of Technology, Chongqing, China; bDepartment of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, North Ryde, New South Wales, Australia
Background: Large artery stiffness, a cardiovascular risk factor, is blood pressure and heart rate (HR) dependent. However, the effects of waveform input (for example, left ventricular ejection time, LVET) and wave reflection (for example, changes in peripheral resistance) are harder to elucidate.
Aims: To quantify the effect of LVET and peripheral resistance changes on carotid-femoral pulse wave velocity (cfPWV), a measure of large artery stiffness, through a computational model.
Methods: Using a transmission line model of the human arterial tree, changes in HR (60–100 bpm), LVET (0.1–0.45 s) at a fixed HR of 70 bpm, and peripheral resistance (50–150%) were modelled and the blood pressure waveform at the carotid and femoral sites generated for a static elastic modulus (non-pressure and non-frequency dependent). cfPWV was calculated using waveform shape methods as applied in the clinic (intersecting tangents, maximum systolic upstroke) and by calculation of the phase velocity.
Results: Without a dynamic elastic component of elasticity, cfPWV was not dependent on HR, but increased significantly with increasing LVET (0.17±0.22 m/s per 50 ms) when calculated using the intersecting tangents or systolic upstroke method. Correlation of cfPWV with peripheral resistance was strong, but the magnitude of the dependency was low (0.03±0.01 to 0.05±0.05 m/s per 10% increase in resistance) when calculated by the intersecting tangent or systolic upstroke method. When cfPWV was calculated using phase velocity (independent of blood pressure waveform shape), the expected zero dependency on LVET or peripheral resistance was identified.
Conclusion: Increased LVET causes changes in blood pressure waveform shape that increased cfPWV if measured by the intersecting tangents or maximum systolic upstroke methods. Changes in HR (without accounting for viscoelasticity) and changes in peripheral resistance (independent of blood pressure) either have no, or minimal, effect on measured cfPWV.
- © 2017 American Heart Association, Inc.