(Hypertension. 1998;31:409.)
© 1998 American Heart Association, Inc.
Scientific Contributions |
From Department of Physiology and Biophysics and Center for Excellence in Cardiovascular-Renal Research, University of Mississippi Medical Center, Jackson, Miss.
Correspondence of John E. Hall, PhD, Department of Physiology and Biophysics, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216-4505
| Abstract |
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Key Words: leptin hypertension sympathetic blood pressure heart rate food intake
Abbreviations: CNS = central nervous system GFR = glomerular filtration rate HR = heart rate MAP = mean arterial pressure PRA = plasma renin activity RPF = renal plasma flow RVR = renal vascular resistance SNS = sympathetic nervous system
| Introduction |
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The aim of this study, therefore, was to determine whether increases in circulating leptin, to levels similar to those found in obesity, cause sustained changes in cardiovascular, renal, and neurohumoral function. Furthermore, we investigated the role of CNS versus systemic mechanisms by comparing the chronic effects of carotid artery and IV leptin infusion on control of arterial pressure and renal function.
| Methods |
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Rats were allowed to recover from the surgery and were housed in individual metabolic cages in a quiet, air-conditioned room with a 12:12 hour light/dark cycle. In the CNS infusion group, the carotid artery catheters were connected to a syringe pump (Harvard Apparatus) via a dual-channel hydraulic swivel (Instech) mounted above the cage for continuous 24-hour infusion. The aortic catheter was filled with heparin solution (1000 USP U/mL) and plugged. For arterial pressure measurement, the aortic catheter was flushed and connected to a pressure transducer (Cobe) mounted on the cage exterior at the level of the rat. Pulsatile arterial pressure signals were sent to an analog-to-digital converter and analyzed by computer using customized software. The analog signal was sampled for 4 seconds every 15 seconds from 7:00 AM to 1:00 PM daily. In the IV-infused group, the venous catheter was connected to a syringe pump via one port of the hydraulic swivel for continuous 24-hour infusion, and the aortic catheter was connected to the transducer via the other port.
The rats received food and water ad libitum throughout the study. Sodium intake was maintained constant at approximately 3.0 mEq/d by continuous infusion of 20 mL of 0.9% saline/d, combined with feeding a sodium-deficient rat chow. In addition, 21 mL of sterile water/d was infused as a vehicle for the leptin infusion during the experimental period, yielding a total volume of 41 mL/d. This infusion began immediately after placement of rats in their metabolic cages. A minimum of 5 to 7 days were allowed for acclimation before control measurements were made. All solutions contained antibiotic (penicillin G potassium 30,000 U/d and mezlocillin 27 mg/d) and were infused through a Millipore filter (22µm, Cathivex, Millipore).
Experimental Protocol
After 7 days of control measurements, murine leptin (Amgen Inc.) was infused into the carotid arteries or femoral vein at 0.1 µg/kg/min for 5 days and at 1 µg/kg/min for 7 days, followed by a 7-days recovery period. Mean arterial pressure (MAP), heart rate (HR), urine volume, urinary sodium excretion, and food and water intake were recorded daily. Blood samples (2 mL) were collected on the fifth day of the control, leptin infusion, and recovery periods for the measurement of plasma insulin, leptin, aldosterone, corticosterone and protein concentration, blood glucose, hematocrit, PRA, GFR, and RPF. The blood sample was replaced with an equal volume of saline.
Analytical Methods
PRA was measured by radioimmunoassay using 125I-angiotensin I from New England Nuclear and antibody from Arnel. Plasma insulin, aldosterone, and corticosterone concentrations were measured by radioimmunoassay (Diagnostic Products). Plasma leptin concentration was measured by enzyme immunoassay (Amgen Inc.). Plasma protein concentration was measured by refractometry (American Optical). Urine sodium concentration was determined by using ion-sensitive electrodes (Nova). Blood glucose was measured by using an AccuCheck III blood glucose monitor (Boehringer Mannhein Corporation). GFR and RPF were measured by using a 4-hour fasted plasma sample following a 24-hour IV infusion of 125I-iothalamate (Glofil) and 131I-iodohippuran, respectively. Steady state is achieved after 24 hours of IV isotope infusion in this protocol; therefore, urinary excretion rate is equal to infusion rate of the isotope, and the infusion rate of isotope can be substituted for urinary excretion rate to calculate clearance.8
Statistical Analysis
All data are expressed as mean ± SE. Data were analyzed by a two-factor ANOVA with repeated measures and Dunnetts test for multiple comparisons, when appropriate.9,10 Statistical significance was accepted at P<.05.
| Results |
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MAP increased slightly by day 5 of carotid artery leptin infusion at 0.1 µg/kg/min, but the increase was not statistically significant (Fig 2). At the 1 µg/kg/min dose, however, MAP increased significantly, to 94 ± 2 mm Hg by the fifth day. Leptin infusion at 0.1 µg/kg/min IV did not change MAP but, at the higher dose, raised MAP significantly from 87 ± 1 mm Hg to 93 ± 1 mm Hg (Fig 2). Arterial pressure decreased rapidly to levels below control levels after leptin infusion was stopped in both carotid artery and IV infusion groups.
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Chronic carotid artery infusion of leptin at 0.1 µg/kg/min did not change heart rate significantly, but at the 1 µg/kg/min dose, HR increased from 323 ± 4 beats/min to 355 ± 5 beats/ min by day 7 of the infusion (Fig 3). Similar to the effect of carotid artery infusion, chronic IV infusion of leptin did not affect HR at the low dose, but heart rate increased significantly at the high dose, from 305 ± 9 beats/min during the control period to 322 ± 10 beats/min by day 7 of leptin infusion period (Fig 3). HR decreased rapidly in both carotid artery and IV infusion groups after leptin infusion was stopped and was significantly below control (302 ± 5 beats/min and 284 ± 5 beats/min, respectively) by day 3 of the recovery period.
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Effect of Leptin Infusion on Renal Function
Although there was a tendency for urine volume to increase during leptin infusion at 1 µg/kg/min in both carotid artery and IV infusion groups, the increase was not statistically significant (Fig 4). There also was no significant change in urinary sodium excretion in either group during leptin infusion at 0.1 or 1 µg/kg/min (Fig 5). GFR, RPF, and RVR did not change during carotid artery leptin infusion at either dose (Fig 6), but in the IV infusion group, RPF decreased significantly and RVR increased significantly at the infusion rate of 1 µg/kg/min (Fig 6). Leptin infusion at 1 µg/kg/min in both carotid and IV infusion groups markedly decreased potassium excretion, paralleling the decrease in food intake and potassium intake, since the food contained all of the daily potassium intake. This resulted in a negative cumulative potassium balance of -6.2 ± 0.4 mEq and -7.0 ± 1.0 mEq in the carotid and IV infusion groups, respectively, after 12 days of leptin infusion. After stopping leptin infusion for 7 days, there was still a negative cumulative potassium balance of -3.8 ± 0.8 mEq and -6.1 ± 1.3 mEq in the carotid and IV infusion groups, respectively.
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Effects of Leptin Infusion on Circulating Hormones
Plasma leptin concentration did not change significantly at the infusion rate of 0.1 µg/kg/min in either the carotid artery or the IV infusion group but increased significantly at 1 µg/kg/min, from 1.2 ± 0.4 to 91 ± 5 ng/mL in the carotid artery infusion group (Table 1) and from 0.9 ± 0.1 to 94 ± 9 ng/mL in the IV infusion group (Table 2). Blood glucose and insulin levels also did not change at the low infusion rate in either the carotid artery or the IV infusion group but decreased significantly at 1 µg/kg/min in both groups. Plasma leptin, insulin, and blood glucose returned to control levels after leptin infusion was stopped in both groups. There were no significant changes in PRA, plasma aldosterone, or corticosterone concentrations during leptin infusion in either group (Table 1 and 2).
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| Discussion |
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Humoral and Metabolic Actions of Leptin
Food intake did not change during carotid artery or IV leptin infusion at 0.1 µg/kg/min but was decreased significantly at 1 µg/kg/min in both groups. These observations are consistent with previous studies that chronic injection of leptin in ob/ob mice, animals with deficient leptin production, significantly reduces food intake.1113 The mechanism for leptins effect to reduce food intake has been suggested to be suppression of hypothalamic NPY mRNA expression and NPY release,14 although most previous studies have used very high concentrations of leptin to demonstrate these effects. In the present study, increased circulating leptin concentration, to levels comparable to those found in obese humans,3 markedly reduced food intake. These observation provide further support for the concept that leptin is an important physiological regulator of energy balance.
Increased circulating leptin also markedly decreased plasma insulin concentration and modestly reduced blood glucose. Although the mechanisms responsible for leptins effects on plasma insulin and glucose levels are not clear, a recent study by Kieffer et al15 indicates that there are leptin receptors located on the pancreatic ß-cells, although the function of these receptors is not known. Leptin may also decrease insulin release by stimulating
-adrenergic receptors in the pancreas via its effect on sympathetic activity. However, the finding that leptin decreased plasma glucose suggests additional effects besides a simple inhibition of insulin secretion. Another possibility is that leptin increased glucose utilization or improved insulin sensitivity in peripheral tissues, which enhanced glucose disposal in skeletal muscle and fat cells and suppressed glucose output by the liver. Thus, the decrease in plasma insulin could be a compensatory response to a fall in plasma glucose. Additional studies are needed, however, to determine how leptin affects glucose control and insulin secretion.
Leptin, at the higher dose, did not alter plasma renin activity, but corticosterone and aldosterone tended to decrease, although not significantly. The reduced plasma aldosterone levels may be related to reduced potassium intake associated with reduced food consumption.
Arterial Pressure and Heart Rate Responses to Leptin
Previous studies5,6,16 have reported that arterial pressure and heart rate were not changed by acute leptin infusion. One possible explanation is that arterial pressure and heart rate were measured under anesthesia in those studies, whereas our studies were conducted in conscious rats. In addition, leptin was administered acutely in previous studies, either by a single bolus injection or by short-term infusion. Our results are consistent with those findings, because the increases in arterial pressure and heart rate were not apparent until 3 to 4 days after the leptin infusion was started. This was true even for the low infusion rate, which appeared to have a small centrally mediated effect on arterial pressure, since there was no significant change in systemic plasma leptin concentration and IV leptin infusion at this rate caused no changes in heart rate and arterial pressure. Thus, both the arterial pressure and heart rate responses to physiological increases in circulating leptin levels appear to be slow in onset.
The mechanisms by which increased circulating levels of leptin elevate arterial pressure and heart rate chronically are not entirely clear. One possible explanation is activation of the sympathetic nervous system. The finding that animals with deficient leptin production (ob/ob mice) or defective leptin receptors (db/db mice) also have decreased metabolic activity and hypothermia is consistent with the concept that leptin interacts with hypothalamic receptors to reduce food intake and activate the SNS.2 Furthermore, leptin has been shown to increase norepinephrine turnover in interscapular brown adipose tissue,17 and a recent study by Haynes and colleagues5 reported that acute IV infusion of leptin in rats increased sympathetic nerve activity in the adrenals, brown adipose tissue, and the kidneys.
Our finding that there was a tendency for arterial pressure to increase with low-dose carotid artery infusion suggests a possible CNS mechanism, but our studies cannot determine the precise role of CNS compared to systemic actions of leptin in chronic blood pressure regulation. Further studies are needed to determine the role of the CNS and peripheral effects of leptin in long-term blood pressure regulation.
Heart rate also increased significantly with chronic carotid artery and IV leptin infusion at 1µg/kg/min. Although leptin receptor mRNA has been shown to be expressed in the heart,4 the physiological role of this receptor remains to be determined. Leptin could increase heart rate by increasing cardiac sympathetic activity or by withdrawal of parasympathetic tone. A recent study in our laboratory, for example, demonstrated that the increased heart rate associated with 5 weeks of a high-fat diet in dogs was due mainly to decreased cholinergic activity.18 However, additional studies are required to determine the contribution of sympathetic and parasympathetic mechanisms in mediating leptins effect on heart rate.
Renal Effects of Leptin
Previous acute studies have shown that infusion of leptin at high doses caused natriuresis and diuresis.6,16 For example, Jackson and Li6 reported that intrarenal leptin injection at 30 µg/min caused a twofold increase in urine volume and sodium excretion in normal rats. Reams et al16 also reported that bolus IV injection of leptin at 400 µg/kg significantly increased urine volume and sodium excretion in normotensive Sprague-Dawley rats, although natriuresis was not observed in spontaneously hypertensive rats.
In the present study, we found no significant changes in sodium excretion or urine volume during chronic infusion of leptin at a rate that produced physiological increases in plasma leptin concentration. However, the absence of significant changes in sodium excretion in our study does not necessary imply that leptin had no effect on renal function. In fact, IV leptin infusion significantly decreased RPF and increased RVR. Moreover, the observation that leptin did not increase sodium excretion, despite raising arterial pressure, provides evidence that leptin, infused IV or via the carotid arteries, shifted the renal-pressure natriuresis relationship to higher blood pressures. In the absence of an impaired pressure natriuresis, increased arterial pressure would tend to increase renal sodium and water excretion.19,20 Whether this effect of leptin to shift pressure natriuresis is due to direct renal action or to other effects, such as sympathetic stimulation, is still unclear.
In summary, our studies demonstrated that leptin, at physiological concentration, markedly decreased food intake and plasma insulin, supporting the concept that leptin plays an important role in regulating energy balance. Our studies also indicate that increases in circulating leptin concentration, to levels similar to those found in obesity, significantly elevate arterial pressure and heart rate, findings suggesting a possible role for leptin in obesity hypertension. Further studies are needed, however, to determine the precise role of the CNS and peripheral effects of leptin in long-term blood pressure regulation in obesity.
| Acknowledgments |
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This study was supported by National Heart, Lung, and Blood Institute Grant HL-51971.
Received September 16, 1997; first decision October 20, 1997; accepted October 29, 1997.
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R. Wolk, A. S.M. Shamsuzzaman, and V. K. Somers Obesity, Sleep Apnea, and Hypertension Hypertension, December 1, 2003; 42(6): 1067 - 1074. [Abstract] [Full Text] [PDF] |
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C. Plut, C. Ribiere, Y. Giudicelli, and J.-P. Dausse Hypothalamic Leptin Receptor and Signaling Molecule Expressions in Cafeteria Diet-Fed Rats J. Pharmacol. Exp. Ther., November 1, 2003; 307(2): 544 - 549. [Abstract] [Full Text] [PDF] |
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A. J. Marsh, M. A.P. Fontes, S. Killinger, D. B. Pawlak, J. W. Polson, and R. A.L. Dampney Cardiovascular Responses Evoked by Leptin Acting on Neurons in the Ventromedial and Dorsomedial Hypothalamus Hypertension, October 1, 2003; 42(4): 488 - 493. [Abstract] [Full Text] [PDF] |
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L. A. Barouch, D. E. Berkowitz, R. W. Harrison, C. P. O'Donnell, and J. M. Hare Disruption of Leptin Signaling Contributes to Cardiac Hypertrophy Independently of Body Weight in Mice Circulation, August 12, 2003; 108(6): 754 - 759. [Abstract] [Full Text] [PDF] |
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K. Rahmouni, W. G. Haynes, D. A. Morgan, and A. L. Mark Role of Melanocortin-4 Receptors in Mediating Renal Sympathoactivation to Leptin and Insulin J. Neurosci., July 9, 2003; 23(14): 5998 - 6004. [Abstract] [Full Text] [PDF] |
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J. M. Fernandez-Real and W. Ricart Insulin Resistance and Chronic Cardiovascular Inflammatory Syndrome Endocr. Rev., June 1, 2003; 24(3): 278 - 301. [Abstract] [Full Text] [PDF] |
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C. J. Lyon, R. E. Law, and W. A. Hsueh Minireview: Adiposity, Inflammation, and Atherogenesis Endocrinology, June 1, 2003; 144(6): 2195 - 2200. [Abstract] [Full Text] [PDF] |
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G. Coatmellec-Taglioni, J.-P. Dausse, Y. Giudicelli, and C. Ribiere Sexual Dimorphism in Cafeteria Diet-Induced Hypertension Is Associated with Gender-Related Difference in Renal Leptin Receptor Down-Regulation J. Pharmacol. Exp. Ther., April 1, 2003; 305(1): 362 - 367. [Abstract] [Full Text] |
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J. J. Kuo, O. B. Jones, and J. E. Hall Chronic cardiovascular and renal actions of leptin during hyperinsulinemia Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2003; 284(4): R1037 - R1042. [Abstract] [Full Text] [PDF] |
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T. Shirasaka, M. Takasaki, and H. Kannan Cardiovascular effects of leptin and orexins Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2003; 284(3): R639 - R651. [Abstract] [Full Text] [PDF] |
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J. E. Hall The Kidney, Hypertension, and Obesity Hypertension, March 1, 2003; 41(3): 625 - 633. [Abstract] [Full Text] [PDF] |
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J. J. Kuo, A. A. Silva, and J. E. Hall Hypothalamic Melanocortin Receptors and Chronic Regulation of Arterial Pressure and Renal Function Hypertension, March 1, 2003; 41(3): 768 - 774. [Abstract] [Full Text] [PDF] |
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A. Fortuno, A. Rodriguez, J. Gomez-Ambrosi, P. Muniz, J. Salvador, J. Diez, and G. Fruhbeck Leptin Inhibits Angiotensin II-Induced Intracellular Calcium Increase and Vasoconstriction in the Rat Aorta Endocrinology, September 1, 2002; 143(9): 3555 - 3560. [Abstract] [Full Text] [PDF] |
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M. Shintani, H. Ikegami, T. Fujisawa, Y. Kawaguchi, M. Ohishi, T. Katsuya, J. Higaki, K. Shimamoto, and T. Ogihara Leptin Gene Polymorphism Is Associated with Hypertension Independent of Obesity J. Clin. Endocrinol. Metab., June 1, 2002; 87(6): 2909 - 2912. [Abstract] [Full Text] [PDF] |
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A. L. Mark and W. I. Sivitz Uncoupling Metabolism and Coupling Leptin to Cardiovascular Disease Arterioscler Thromb Vasc Biol, June 1, 2002; 22(6): 881 - 883. [Full Text] [PDF] |
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C. Bernal-Mizrachi, S. Weng, B. Li, L. A. Nolte, C. Feng, T. Coleman, J. O. Holloszy, and C. F. Semenkovich Respiratory Uncoupling Lowers Blood Pressure Through a Leptin-Dependent Mechanism in Genetically Obese Mice Arterioscler Thromb Vasc Biol, June 1, 2002; 22(6): 961 - 968. [Abstract] [Full Text] [PDF] |
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P. Quehenberger, M. Exner, R. Sunder-Plassmann, K. Ruzicka, C. Bieglmayer, G. Endler, C. Muellner, W. Speiser, and O. Wagner Leptin Induces Endothelin-1 in Endothelial Cells In Vitro Circ. Res., April 5, 2002; 90(6): 711 - 718. [Abstract] [Full Text] [PDF] |
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M. L.G. Correia, W. G. Haynes, K. Rahmouni, D. A. Morgan, W. I. Sivitz, and A. L. Mark The Concept of Selective Leptin Resistance: Evidence From Agouti Yellow Obese Mice Diabetes, February 1, 2002; 51(2): 439 - 442. [Abstract] [Full Text] [PDF] |
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M. Carlyle, O. B. Jones, J. J. Kuo, and J. E. Hall Chronic Cardiovascular and Renal Actions of Leptin: Role of Adrenergic Activity Hypertension, February 1, 2002; 39(2): 496 - 501. [Abstract] [Full Text] [PDF] |
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L. E. Wold, D. P. Relling, J. Duan, F. L. Norby, and J. Ren Abrogated Leptin-Induced Cardiac Contractile Response in Ventricular Myocytes Under Spontaneous Hypertension: Role of JAK/STAT Pathway Hypertension, January 1, 2002; 39(1): 69 - 74. [Abstract] [Full Text] [PDF] |
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S. J. Swoap Altered leptin signaling is sufficient, but not required, for hypotension associated with caloric restriction Am J Physiol Heart Circ Physiol, December 1, 2001; 281(6): H2473 - H2479. [Abstract] [Full Text] [PDF] |
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J. L. Mitchell, D. A. Morgan, M. L.G. Correia, A. L. Mark, W. I. Sivitz, and W. G. Haynes Does Leptin Stimulate Nitric Oxide to Oppose the Effects of Sympathetic Activation? Hypertension, November 1, 2001; 38(5): 1081 - 1086. [Abstract] [Full Text] [PDF] |
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M. L.G. Correia, D. A. Morgan, J. L. Mitchell, W. I. Sivitz, A. L. Mark, and W. G. Haynes Role of Corticotrophin-Releasing Factor in Effects of Leptin on Sympathetic Nerve Activity and Arterial Pressure Hypertension, September 1, 2001; 38(3): 384 - 388. [Abstract] [Full Text] [PDF] |
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M. Winnicki, B. G. Phillips, V. Accurso, P. van de Borne, A. Shamsuzzaman, K. Patil, K. Narkiewicz, and V. K. Somers Independent Association Between Plasma Leptin Levels and Heart Rate in Heart Transplant Recipients Circulation, July 24, 2001; 104(4): 384 - 386. [Abstract] [Full Text] [PDF] |
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A. Sonmez, U. Kisa, G. Uckaya, T. Eyileten, B. Comert, B. Koc, F. Kocabalkan, and M. Ozata Effects of losartan treatment on T-cell activities and plasma leptin concentrations in primary hypertension Journal of Renin-Angiotensin-Aldosterone System, June 1, 2001; 2(2): 112 - 116. [Abstract] [PDF] |
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K. Hotta, T. Funahashi, N. L. Bodkin, H. K. Ortmeyer, Y. Arita, B. C. Hansen, and Y. Matsuzawa Circulating Concentrations of the Adipocyte Protein Adiponectin Are Decreased in Parallel With Reduced Insulin Sensitivity During the Progression to Type 2 Diabetes in Rhesus Monkeys Diabetes, May 1, 2001; 50(5): 1126 - 1133. [Abstract] [Full Text] |
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M. L. G. Correia, D. A. Morgan, W. I. Sivitz, A. L. Mark, and W. G. Haynes Leptin Acts in the Central Nervous System to Produce Dose-Dependent Changes in Arterial Pressure Hypertension, March 1, 2001; 37(3): 936 - 942. [Abstract] [Full Text] [PDF] |
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J. M. Overton, T. D. Williams, J. B. Chambers, and M. E. Rashotte Central Leptin Infusion Attenuates the Cardiovascular and Metabolic Effects of Fasting in Rats Hypertension, February 1, 2001; 37(2): 663 - 669. [Abstract] [Full Text] [PDF] |
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J. J. Kuo, O. B. Jones, and J. E. Hall Inhibition of NO Synthesis Enhances Chronic Cardiovascular and Renal Actions of Leptin Hypertension, February 1, 2001; 37(2): 670 - 676. [Abstract] [Full Text] [PDF] |
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M. W. Nickola, L. E. Wold, P. B. Colligan, G.-J. Wang, W. K. Samson, and J. Ren Leptin Attenuates Cardiac Contraction in Rat Ventricular Myocytes : Role of NO Hypertension, October 1, 2000; 36(4): 501 - 505. [Abstract] [Full Text] [PDF] |
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R. Rosmond, Y. C. Chagnon, G. Holm, M. Chagnon, L. Pérusse, K. Lindell, B. Carlsson, C. Bouchard, and P. Björntorp Hypertension in Obesity and the Leptin Receptor Gene Locus J. Clin. Endocrinol. Metab., September 1, 2000; 85(9): 3126 - 3131. [Abstract] [Full Text] |
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N. Anim-Nyame, S.R. Sooranna, P.J. Steer, and M.R. Johnson Longitudinal analysis of maternal plasma leptin concentrations during normal pregnancy and pre-eclampsia Hum. Reprod., September 1, 2000; 15(9): 2033 - 2036. [Abstract] [Full Text] [PDF] |
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P. Stenvinkel Leptin and blood pressure--is there a link? Nephrol. Dial. Transplant., August 1, 2000; 15(8): 1115 - 1117. [Full Text] [PDF] |
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B. G. Phillips, M. Kato, K. Narkiewicz, I. Choe, and V. K. Somers Increases in leptin levels, sympathetic drive, and weight gain in obstructive sleep apnea Am J Physiol Heart Circ Physiol, July 1, 2000; 279(1): H234 - H237. [Abstract] [Full Text] [PDF] |
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G. Paolisso, D. Manzella, N. Montano, A. Gambardella, and M. Varricchio Plasma Leptin Concentrations and Cardiac Autonomic Nervous System in Healthy Subjects with Different Body Weights J. Clin. Endocrinol. Metab., May 1, 2000; 85(5): 1810 - 1814. [Abstract] [Full Text] |
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K. Matsumura, I. Abe, T. Tsuchihashi, and M. Fujishima Central effects of leptin on cardiovascular and neurohormonal responses in conscious rabbits Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2000; 278(5): R1314 - R1320. [Abstract] [Full Text] [PDF] |
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A. N. Vgontzas, D. A. Papanicolaou, E. O. Bixler, K. Hopper, A. Lotsikas, H.-M. Lin, A. Kales, and G. P. Chrousos Sleep Apnea and Daytime Sleepiness and Fatigue: Relation to Visceral Obesity, Insulin Resistance, and Hypercytokinemia J. Clin. Endocrinol. Metab., March 1, 2000; 85(3): 1151 - 1158. [Abstract] [Full Text] |
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G. Uckaya, M. Ozata, A. Sonmez, C. Kinalp, T. Eyileten, N. Bingol, B. Koc, F. Kocabalkan, and I. C. Ozdemir Is Leptin Associated with Hypertensive Retinopathy? J. Clin. Endocrinol. Metab., February 1, 2000; 85(2): 683 - 687. [Abstract] [Full Text] |
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T. D. Williams, J. B. Chambers, O. L. May, R. P. Henderson, M. E. Rashotte, and J. M. Overton Concurrent reductions in blood pressure and metabolic rate during fasting in the unrestrained SHR Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2000; 278(1): R255 - R262. [Abstract] [Full Text] [PDF] |
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T. Shirasaka, M. Nakazato, S. Matsukura, M. Takasaki, and H. Kannan Sympathetic and cardiovascular actions of orexins in conscious rats Am J Physiol Regulatory Integrative Comp Physiol, December 1, 1999; 277(6): R1780 - R1785. [Abstract] [Full Text] [PDF] |
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G. Paolisso, M. R. Tagliamonte, M. Galderisi, G. A. Zito, A. Petrocelli, C. Carella, O. de Divitiis, and M. Varricchio Plasma Leptin Level Is Associated With Myocardial Wall Thickness in Hypertensive Insulin-Resistant Men Hypertension, November 1, 1999; 34(5): 1047 - 1052. [Abstract] [Full Text] [PDF] |
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S. Soderberg, B. Ahren, B. Stegmayr, O. Johnson, P.-G. Wiklund, L. Weinehall, G. Hallmans, and T. Olsson Leptin Is a Risk Marker for First-Ever Hemorrhagic Stroke in a Population-Based Cohort Stroke, February 1, 1999; 30(2): 328 - 337. [Abstract] [Full Text] [PDF] |
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A. L. Mark, M. Correia, D. A. Morgan, R. A. Shaffer, and W. G. Haynes Obesity-Induced Hypertension : New Concepts From the Emerging Biology of Obesity Hypertension, January 1, 1999; 33(1): 537 - 541. [Abstract] [Full Text] [PDF] |
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D. Villarreal, G. Reams, R. H. Freeman, and A. Taraben Renal effects of leptin in normotensive, hypertensive, and obese rats Am J Physiol Regulatory Integrative Comp Physiol, December 1, 1998; 275(6): R2056 - R2060. [Abstract] [Full Text] [PDF] |
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P. M. Smith, V. Mollaret, and A. V. Ferguson Leptin acts in the rat hypothalamic paraventricular nucleus to induce gastric mucosal damage Am J Physiol Regulatory Integrative Comp Physiol, December 1, 1998; 275(6): R2081 - R2084. [Abstract] [Full Text] [PDF] |
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H. Mise, N. Sagawa, T. Matsumoto, S. Yura, H. Nanno, H. Itoh, T. Mori, H. Masuzaki, K. Hosoda, Y. Ogawa, et al. Augmented Placental Production of Leptin in Preeclampsia: Possible Involvement of Placental Hypoxia J. Clin. Endocrinol. Metab., September 1, 1998; 83(9): 3225 - 3229. [Abstract] [Full Text] |
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P. Quehenberger, M. Exner, R. Sunder-Plassmann, K. Ruzicka, C. Bieglmayer, G. Endler, C. Muellner, W. Speiser, and O. Wagner Leptin Induces Endothelin-1 in Endothelial Cells In Vitro Circ. Res., April 5, 2002; 90(6): 711 - 718. [Abstract] [Full Text] [PDF] |
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