(Hypertension. 2001;37:1303.)
© 2001 American Heart Association, Inc.
Scientific Contributions |
From the Department of Endocrinology (K.B, M.O.M., O.M., L.G.) and Department of Community Medicine (U.L. L.R.), Malmö University Hospital, Lund University, Malmö, Sweden; Billingen Health Care Center (K.B.), Skövde, Sweden; Skaraborg Institute (U.L.), Skövde, Sweden; and Malmö University (J.R.), Malmö, Sweden.
Correspondence and reprint requests to K. Bengtsson, MD, Billingen Health Care Center, Ekängsvägen 15, S-541 40 Skövde, Sweden. E-mail kristina.a.bengtsson{at}vgregion.se
| Abstract |
|---|
|
|
|---|
Key Words: genetics hypertension, genetic blood pressure diabetes receptors, adrenergic, beta sibling
| Introduction |
|---|
|
|
|---|
The Gly16 allele of the Arg16Gly polymorphism has been ascribed a greater degree of agonist-induced downregulation of the receptor in transfected fibroblasts and human bronchial smooth muscle12 but also with a 5-fold increased sensitivity to catecholamine-induced lipolysis in human adipocytes.6 The Gly16 allele has been associated with hypertension in African Caribbeans8 and with elevated blood pressure and reduced vasodilatation after infusion of salbutamol in normotensive Austrian males.13 However, the Arg16 allele has been associated with elevated blood pressure in the offspring of Norwegians9 and Germans.10 Although the Gln27Glu polymorphism has been associated with obesity,6 7 14 type 2 diabetes, and hypertriglyceridemia,15 these findings have not been replicated in other studies.16 17 The Gln27Glu polymorphism is in linkage disequilibrium with the 5'LC-Arg19Cys polymorphism in the 5'-leader cistron (5'LC).4 The 5'LC codes for a polypeptide that seems to affect the expression of the receptor18 and could therefore influence the susceptibility to hypertension,4 obesity, and type 2 diabetes.19
The aim of this study was to investigate the role of the Arg16Gly, Gln27Glu, and 5'LC-Arg19Cys polymorphisms in the B2AR gene in hypertension and type 2 diabetes in a case-control association study and in genotype-discordant sibling pairs.
| Methods |
|---|
|
|
|---|
60 years and 265 unrelated healthy control subjects
without medication, personal history of hypertension, first-degree
family history of hypertension, or type 2 diabetes from southern
Sweden.20 The subjects
identified in the Skaraborg Hypertension and Diabetes Project
consisted of 2 cohorts. One cohort included 1149 patients with
hypertension and/or diabetes and the other cohort included an
age-stratified, random sample (1400 invited, 1109 participating) from
the population 40 years of age and older. Hypertensive patients and
normotensive spouses from 250 families were recruited from healthcare
centers in the Scania region. In addition, 124 unrelated hypertensive
patients with type 2 diabetes were ascertained from the Skaraborg
Hypertension and Diabetes
project.21 Three
subjects were excluded because of genotyping failure and
misclassification. Hypertension was defined as 3 consecutive blood
pressure measurements
160 mm Hg (systolic blood
pressure) and/or
90 mm Hg (diastolic blood
pressure) or ongoing antihypertensive treatment. The control subjects
had systolic and diastolic blood pressures
150 mm Hg and
80 mm Hg, respectively. The diagnosis of
type 2 diabetes was based on criteria from the World Health
Organization.22 The
participants were categorized as
follows:1 all hypertensives
are patients with hypertension, regardless of whether they had type 2
diabetes or not (n=415);2
hypertensives without type 2 diabetes
(n=291);3 hypertensives with
type 2 diabetes (n=124); and4
healthy controls (n=265)
(Table 1).
|
For the genotype-discordant sib pair study, 494 normotensive siblings were ascertained from 118 families with type 2 diabetes in Botnia, Finland,23 and they were genotyped for the B2AR gene Arg16Gly and Gln27Glu polymorphisms to identify genotype discordant pairs. In total, we identified 72 sib pairs in which 1 of the siblings was homozygous for the Gly16 allele and the other sibling carried either 1 or 2 Arg16 alleles. Similarly, we identified 40 sib pairs in which 1 of the siblings was homozygous for the Glu27 allele whereas the other sibling had 1 or 2 Gln27 alleles. The 72 sib pairs who were discordant for Arg16Gly polymorphism originated from 46 sibships that comprised 118 individuals, and the 40 sib pairs who were discordant for the Gln27Glu polymorphism originated from 26 sibships and included 64 individuals (Table 1). The ethics committees of the Gothenburg and Lund University approved the study. Informed consent was obtained from all the participants.
Blood pressure was measured with a sphygmomanometer after 5
minutes of rest in the supine position in the Swedish subjects and
twice within 10 minutes after 15 minutes of rest in the sitting
position in the Finnish subjects, the values given are the averages of
the 2 measurements. Body weight and height were measured and body mass
index (BMI) was calculated. BMI
27 kg/m2
was considered as overweight. Total genomic DNA was extracted from the
whole blood by standard
methods.24
The Arg16Gly and Gln27Glu polymorphisms were genotyped by polymerase chain reaction and restriction fragment-length polymorphism methods. The Arg16Gly polymorphism was amplified in a genomic 203-bp fragment using primers ß2 to 16-MM-F (5'-CGCCTTCTTGCTGGCACGCAAT) and ß2 to 16/27-R (5'-CCAGTGAAGTGATGAAGTAGTT), of which the former contains a nucleotide mismatch (underlined) to create a BsrDl recognition site in case of the Gly16 allele. The Gln27Glu polymorphism was amplified in a genomic 169-bp fragment with primers ß2 to 27-MM-F (5'-CCGGACCACGACGTCACCCAG) and ß2 to 16/27-R, of which the former contains a nucleotide mismatch (underlined) to create a BstNl recognition site in case of the Glu27 allele. The primers were designed according to the published B2AR cDNA sequence.1 PCR reactions were performed with 50 ng of genomic DNA in a total volume of 20 µL containing 10 pmol of each primer, 4 nmol dNTPs, 0.5 U Taq polymerase (Pharmacia) in 1x (NH4)2SO4-buffer (16 mmol/L [NH4]2SO4; 67 mmol/L Tris, pH 8.8; 0.01% Tween), with 3% formamide, and 1.5 mmol/L MgCl2. PCR conditions were as follows: initial denaturation at 94°C for 5 minutes, followed by 30 cycles of denaturation (94°C for 30 seconds), annealing (60°C for 30 seconds), and extension (72°C for 30 seconds), with the final extension at 72°C for 10 minutes. The PCR products were digested for 2 hours at 60°C using the buffers recommended by the manufacturer. The product containing the Arg16Gly polymorphism was digested with 1 U of BsrDl (New England Biolabs), which produced 2 fragments of 22 and 181 bps in case of the Gly16 allele, leaving the Arg16 allele uncut. The product containing the Gln27Glu polymorphism was digested with 1 U of BstNl (New England Biolabs), which resulted in 2 fragments of 95 and 75 bps in case of Gln27 allele and 3 fragments of 20, 58, and 95 bps in case of the Glu27 allele. The fragments were separated on 4.5% multipurpose agarose gel (Appligene) with ethidium bromide and visualized under ultraviolet light.
A genomic 172-bp fragment containing the 5'LC-Arg19Cys polymorphism was PCR amplified with a forward primer 5'-GAATGAGGCTTCCAGGCGTCC and a reverse primer 5'- GTCGTGGTCCGGCGCATGGC. PCR reactions were performed with 50 ng of genomic DNA in a total volume of 20 µL containing 10 pmol of each primer, 2 nmol dNTPs, 0.5 U Taq polymerase (Amersham Pharmacia) in a PCR buffer recommended by the manufacturer (Pharmacia) with 1.5% formamid. PCR conditions were as follows: initial denaturation at 95°C for 5 minutes, followed by 30 cycles of denaturation (94°C for 30 seconds), annealing (65°C for 30 seconds), and extension (72°C for 30 seconds), with the final extension at 72°C for 10 minutes. The PCR products were digested in a total volume of 30 µL for 3 hours at 37°C with 1 U of MspA1I restriction endonuclease (Promega) in a buffer recommended by the manufacturer. The MspA1I cuts the 5'LC-Arg19 allele to fragments of 144 and 54 bps, whereas the 5'LC-Cys19 allele remains intact. The fragments were separated on 4.5% multipurpose agarose gel (Appligene) with ethidium bromide and visualized under ultraviolet light.
Statistical Methods
Results are presented as mean±SD.
Differences between group means were tested by ANCOVA. Association
between genotypes and hypertension was analyzed by
logistic regression and expressed as odds ratio (OR) with 95%
confidence interval (CI) and with the Gly16Gly and Glu27Glu
genotypes as reference. Data from the
genotype-discordant sib pairs were analyzed using a
modified permutation test for paired
replicates.25 26
The 2-tailed probability value was estimated using a large
(107) random sample from all possible
permutations. If the observed sum of differences entered into the 5%
region of rejection, the difference between pairs was considered
statistically significant. For sib pairs discordant for the Arg16Gly
polymorphism, the differences in phenotypic variables were
computed as the values in the sibling with the Arg16Arg or Gly16Arg
genotype minus the value in the sibling with the Gly16Gly
genotype. For sib pairs discordant for the Gln27Glu
polymorphism, the differences were computed as the values in the
sibling with the Gln27Gln or Gln27Glu genotype minus the value
in the sibling with the Glu27Glu genotype. Analyses,
except the permutation tests, were performed using BMDP Statistical
Software version 1.12 and an SPSS statistical program (SPSS/PC+ for the
IBM-PC/XT/AT, 1986). All statistical tests were 2-sided, and
P<0.05 was considered
statistically significant.
| Results |
|---|
|
|
|---|
There was a significant increase in the OR (OR 2.14; 95% CI, 1.05 to 4.33, P=0.035) for hypertension in the Arg16Arg genotype carriers with type 2 diabetes (Table 2). Similarly, there was an increase in the OR for hypertension in the Gln27Gln genotype carriers (OR 1.55; 95% CI, 1.00 to 2.41, P=0.050). Neither the Arg16 nor the Gln27 allele conferred an increased risk for hypertension in subjects without type 2 diabetes. The carriers of the different genotypes showed no statistically significant difference between the serum creatinine values and the occurrence of proteinuria. The Arg16Arg genotype was associated with hypertension, especially in the nonobese (BMI<27 kg/m2) subgroup of patients with hypertension and type 2 diabetes (OR 3.47; 95% CI, 1.06 to 11.33, P=0.040).
|
Among the sib pairs discordant for the Arg16Gly polymorphism, those siblings carrying 1 or 2 Arg16 alleles had higher systolic blood pressure compared with individuals homozygous for the Gly16 allele (P=0.049, Table 3). Among the nondiabetic pairs (n=54), siblings with 1 or 2 Arg16 alleles had a higher BMI than siblings homozygous for Gly16 (P=0.026). This was due to the male siblings (11 pairs), 25.9 kg/m2 versus 24.4 kg/m2 (P=0.018). Figure 1 shows the difference in blood pressure and BMI of the individuals in the sib pair combinations used in the permutation test. There was a significant difference in systolic blood pressure between the siblings and in BMI in nondiabetic siblings homozygous for the Gly16 allele and carriers of 1 or more Arg16 alleles.
|
|
There were no significant differences in blood pressure levels or BMI between siblings discordant for the Gln27Glu polymorphism.
| Discussion |
|---|
|
|
|---|
There are several other polymorphisms in the vicinity of the Arg16Gly polymorphism, such as the 5'LC-Arg19Cys, Gln27Glu, and Thr164Ile. Unfortunately, previous studies have not taken linkage disequilibrium between these polymorphisms into account. In vitro the 5'LC-Cys19 allele has been associated with an increase in B2AR gene expression, the Glu27 allele has been associated with a resistance to downregulation, the Ile164 allele has been associated with an impaired Gs-protein coupling,12 and the Arg16 allele has been associated with decreased receptor density on the surface of cultured human fibroblasts.29 Liggett and coworkers reported that the Gly16 allele is associated with increased agonist-induced downregulation of the B2AR in Chinese hamster fibroblasts and that the effect of the Gly16 allele dominates when combined with the Glu27 allele.12 Interestingly, the Glu27 allele has otherwise been shown to be resistant to agonist-induced downregulation.30
In this study we found that the haplotype LC-Cys19-Arg16-Gln27 was associated with increased risk for hypertension in the case-control association study and with elevated systolic blood pressure and higher BMI in genotype-discordant sib pairs. The allele frequencies of the polymorphisms in the B2AR gene differ between different populations.31 The findings that the Arg16 allele is associated with hypertension and higher blood pressure levels in Scandinavians, whereas the Gly16 allele is associated with hypertension in other populations,8 13 may suggest that it is not the Gly16Arg polymorphism per se but rather some polymorphism in linkage disequilibrium with the Gly16Arg polymorphism that is responsible for the association.
Because of the well-established link between hypertension and obesity, we also analyzed BMI in relation to codon 16 and 27 genotypes. We observed that the Arg16 allele was associated with a higher BMI in the sib-pair study. This is not surprising because of the strong linkage disequilibrium between the Gly16Arg and Gln27Glu polymorphisms. Several studies have shown that the Glu27 allele is associated with obesity.6 15 19 However, other studies have found the Gln27 allele to be associated with obesity in males.7 32 Our data are in accordance with a predominant role of the B2AR gene in promoting obesity in males. The difference in BMI in sib pairs was restricted to male subjects with the Arg16 allele.
In conclusion, the Arg16 and Gln27 alleles of the B2AR gene confer an increased risk for hypertension in nonobese patients with type 2 diabetes. This association was replicated in a sib-pair analysis showing that siblings with 1 or 2 Arg16 alleles had higher systolic blood pressure levels and BMI than siblings homozygous for the Gly16 allele.
| Acknowledgments |
|---|
Received May 25, 2000; first decision June 21, 2000; accepted October 30, 2000.
| References |
|---|
|
|
|---|
-adducin gene in primary hypertension in Scandinavians.
J Hum Hypertens. 2000;14:4346.[Medline]
[Order article via Infotrieve]
This article has been cited by other articles:
![]() |
T. Lucas, D. Losert, M. Allen, J. Halaschek-Wiener, B. Pratscher, C. Friedrich, M. Wolschek, G. Fuchsjager-Mayrl, L. Schmetterer, H. Pehamberger, et al. Combination Allele-Specific Real-Time PCR for Differentiation of {beta}2-Adrenergic Receptor Coding Single-Nucleotide Polymorphisms Clin. Chem., April 1, 2004; 50(4): 769 - 772. [Full Text] [PDF] |
||||
![]() |
J. H. Eisenach, A. M. McGuire, R. M. Schwingler, S. T. Turner, and M. J. Joyner The Arg16/Gly {beta}2-adrenergic receptor polymorphism is associated with altered cardiovascular responses to isometric exercise Physiol Genomics, February 13, 2004; 16(3): 323 - 328. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Dallongeville, N. Helbecque, D. Cottel, P. Amouyel, and A. Meirhaeghe The Gly16->Arg16 and Gln27->Glu27 Polymorphisms of {beta}2-Adrenergic Receptor Are Associated with Metabolic Syndrome in Men J. Clin. Endocrinol. Metab., October 1, 2003; 88(10): 4862 - 4866. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Castellano, F. Rossi, M. Giacche, C. Perani, F. Rivadossi, M. L. Muiesan, M. Salvetti, M. Beschi, D. Rizzoni, and E. Agabiti-Rosei {beta}2-Adrenergic Receptor Gene Polymorphism, Age, and Cardiovascular Phenotypes Hypertension, February 1, 2003; 41(2): 361 - 367. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Tomaszewski, N. J.R. Brain, F. J. Charchar, W. Y.S. Wang, B. Lacka, S. Padmanabahn, J. S. Clark, N. H. Anderson, H. V. Edwards, E. Zukowska-Szczechowska, et al. Essential Hypertension and {beta}2-Adrenergic Receptor Gene: Linkage and Association Analysis Hypertension, September 1, 2002; 40(3): 286 - 291. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. J. Ostgren, U. Lindblad, A. Melander, and L. Rastam Survival in Patients With Type 2 Diabetes in a Swedish Community: Skaraborg Hypertension and Diabetes Project Diabetes Care, August 1, 2002; 25(8): 1297 - 1302. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Hypertension Home | Subscriptions | Archives | Feedback | Authors | Help | AHA Journals Home | Search Copyright © 2001 American Heart Association, Inc. All rights reserved. Unauthorized use prohibited. |