Renin-angiotensin and endothelial nitric oxide synthase gene polymorphisms are not associated with the risk of incident type 2 diabetes mellitus: a prospective cohort study

OBJECTIVE

The renin-angiotensin system and endothelial function have both been implicated in the pathogenesis of type 2 diabetes. The aim of this study was to assess the relationship between a set of well-characterized genetic variants of the renin-angiotensin system and the endothelial nitric oxide synthase (NOS3) gene and the incidence of type 2 diabetes.

DESIGN

Prospective cohort study.

SETTING

Women's Health Study, United States.

SUBJECTS

A total of 24,309 Caucasian women free of diabetes at baseline.

MAIN OUTCOME MEASURES

Six previously characterized single nucleotide polymorphisms (NOS3 rs1800779, NOS3 rs3918226, NOS3 rs1799983, ACE rs1799752, AGT rs699 and AGTR rs5186) were genotyped. Cox proportional-hazards models were constructed to compare the incidence of type 2 diabetes according to the different genotypes.

RESULTS

During a median follow-up of 10.2 years (interquartile range 9.6-10.6 years), 999 women developed type 2 diabetes. The age-adjusted incidence rates across the six genotypes were very similar, and ranged from 3.7 to 4.8 cases/1000 person-years of follow-up. The multivariable adjusted hazard ratios (95% confidence intervals) for rs1800779, rs3918226, rs1799983, rs1799752, rs699, and rs5186 were 1.01 (0.92-1.10), 1.09 (0.93-1.27), 0.95 (0.86-1.05), 1.04 (0.95-1.14), 1.08 (0.98-1.18), 1.01 (0.91-1.11), confirming the lack of association between the genotypes and incident type 2 diabetes. Stratification by body mass index revealed essentially unchanged results. Finally, there was no association between NOS3-haplotypes and incident type 2 diabetes.

CONCLUSION

We did not find an association between six well-characterized genetic polymorphisms of the renin-angiotensin system or the NOS3 gene and the occurrence of type 2 diabetes.

Qualitative and quantitative effects of APOE genetic variation on plasma C-reactive protein, LDL-cholesterol, and apoE protein

A genetic link between lipid metabolism and inflammation has been suggested by the association between variation in the APOE gene and plasma C-reactive protein (CRP). This association was confirmed among Caucasians and extended to an African-American population, and the well-known associations of APOE variation with LDL-C and apoE protein were also observed. While eight common variants in APOE were examined, the association with CRP involved primarily the two nonsynonymous SNPs that define the major epsilon2, epsilon3, and epsilon4 alleles. In particular, the strongest link involved lower CRP levels among carriers of the APOE epsilon4 allele that also contributes to the risk of cardiovascular and Alzheimer's diseases as well as to higher lipid levels. A lesser effect was characterized by lower CRP levels among carriers of a subtype of the epsilon3 allele. The magnitude of the association with plasma CRP was at least as great as the effect of variation in the CRP gene itself. Quantitative analysis suggested that the effect on CRP is more likely a consequence of intrinsic functional differences among the E2, E3, and E4 apoE proteins than different levels of apoE protein or LDL-C in the plasma.

Qualitative and quantitative effects of APOE genetic variation on plasma C-reactive protein, LDL-cholesterol, and apoE protein

A genetic link between lipid metabolism and inflammation has been suggested by the association between variation in the APOE gene and plasma C-reactive protein (CRP). This association was confirmed among Caucasians and extended to an African-American population, and the well-known associations of APOE variation with LDL-C and apoE protein were also observed. While eight common variants in APOE were examined, the association with CRP involved primarily the two nonsynonymous SNPs that define the major epsilon2, epsilon3, and epsilon4 alleles. In particular, the strongest link involved lower CRP levels among carriers of the APOE epsilon4 allele that also contributes to the risk of cardiovascular and Alzheimer's diseases as well as to higher lipid levels. A lesser effect was characterized by lower CRP levels among carriers of a subtype of the epsilon3 allele. The magnitude of the association with plasma CRP was at least as great as the effect of variation in the CRP gene itself. Quantitative analysis suggested that the effect on CRP is more likely a consequence of intrinsic functional differences among the E2, E3, and E4 apoE proteins than different levels of apoE protein or LDL-C in the plasma.

Non-random chromosomal distribution of SSLPs: systematic assessment using a novel genetic linkage map between two closely related rat strains

Simple sequence length polymorphisms (SSLPs) are a widely used tool for genetic studies in humans and model animals. Experimental crosses among closely related strains that differ primarily in the trait that is to be mapped carry the advantage of avoiding co-segregation of potentially confounding traits. However, their realization is encumbered by the limited availability of newly arisen informative SSLPs among such strains. Here we report the establishment of a genome-wide SSLP panel for the spontaneously hypertensive rat (SHR) and its close relative, the stroke-prone SHR (SHRSP), consisting of a total of 273 polymorphic markers that were found among 2,734 rat SSLPs screened. In addition to limitations in numbers, we also found the distribution of informative markers to be heterogeneous, with clustering and paucity of informative markers, respectively, in particular regions. Notably, the majority of regions thus identified was also seen when we examined an unrelated set of strains from the literature, indicating, on a more generic level, the presence of mutagenically more and less stable genomic regions.

A prospective evaluation of the interleukin-1 receptor antagonist intron 2 gene polymorphism and the risk of myocardial infarction

While an interleukin-1 receptor antagonist gene polymorphism (IL1RN-VNTR) has recently been hypothesized to be a risk factor for coronary artery disease, no prospective data relating this polymorphism to subsequent risk of coronary events are available. We therefore investigated the association between IL1RN-VNTR genotype and the incidence of myocardial infarction (MI) in a large, prospective cohort of initially healthy men. The IL1RN-VNTR was evaluated among 385 MI case subjects and an equal number of age- and smoking-matched control subjects during a 12-year follow-up. Overall, the allele and genotype distributions were similar among cases and controls, both in the total cohort and in all subgroups evaluated. All observed genotype frequencies were in Hardy-Weinberg equilibrium. Furthermore, the relative risk in a comparison of homozygous mutant to homozygous wild-type was 0.89 (95%CI = 0.5-1.6; P = 0.9). In this large, prospective study, the IL1RN-VNTR gene polymorphism is not associated with risks of future MI. These data also highlight the importance of hypothesis testing studies in genetic epidemiology, particularly for hypotheses generated from small samples or post hoc subgroup analyses.

Ace D/I polymorphism and incidence of post-PTCA restenosis: a prospective, angiography-based evaluation

Early restenosis is the major complication of percutaneous transluminal coronary angioplasty (PTCA), occurring in approximately 30% of all initially successful procedures. The D/I polymorphism of the ACE gene, which has variably been reported to represent a risk factor for manifestations of ischemic heart disease, has recently been implicated in the pathophysiology of restenosis after PTCA by some investigators but not by others. All studies conducted thus far involved relatively small sample sizes. We investigated the possible association of ACE D/I genotype and post-PTCA restenosis in a large, prospective sample of patients followed by quantitative coronary angiography. The ACE D/I gene polymorphism was characterized in a cohort of 779 patients, of whom 342 (cases) had developed restenosis (as defined by >50% loss of lumen compared with immediate postprocedure results) at repeat quantitative coronary angiography at 6 months after PTCA. Allele frequencies for the ACE D and I: alleles were 0.58 and 0.42 in cases and 0.58 and 0.42 in control subjects. All observed genotype frequencies were in Hardy-Weinberg equilibrium. There was no evidence for an association between genotype and restenosis or degree of lumen loss. The data from this largest study of its kind conducted so far provide no evidence for an association of the ACE D/I allelic polymorphism with incidence of restenosis after PTCA. On the basis of the power of this study, we conclude that in a general population, the ACE D/I polymorphism is not a useful marker to assess risk of post-PTCA restenosis.

A prospective evaluation of the CD14 C(-260)T gene polymorphism and the risk of myocardial infarction

The T allele at position -260 of the CD14 lipopolysaccharide receptor gene (CD14) has recently been hypothesized to be a risk factor for myocardial infarction (MI). However, no prospective data relating this polymorphism to risk of future MI are available. In the physicians' health study (PHS), 14916 apparently healthy men were followed over a 12-year period for incident MI. Employing a nested case-control study design, the CD14 C(-260)T polymorphism was evaluated among 387 study participants who developed MI (cases) and among an equal number of age- and smoking-matched study participants who remained free of vascular diseases during follow-up (controls). All observed genotype frequencies were in Hardy-Weinberg equilibrium. However, the allele and genotype distributions of the CD14 polymorphism were similar among cases and controls, both in the total cohort and in all subgroups evaluated. Furthermore, no evidence of association was observed assuming additive, dominant, or recessive mode of inheritance. For example, the relative risk of future MI in a comparison of homozygous mutants to homozygous wild types was 1.00 (95% CI=0.7-1.5; P=0.9). In this large prospective study, the CD14 C(-260)T gene polymorphism was not associated with risks of future MI. Thus, in contrast to prior studies, these data indicate that screening for CD14 C(-260)T genotypes is unlikely to be a useful tool for risk assessment.

Absence of linkage for bone mineral density to chromosome 12q12-14 in the region of the vitamin D receptor gene

Polymorphisms in the region of the gene for the vitamin D receptor (VDR) (chromosome 12q12-14) have been associated with differences in bone mineral density (BMD) in some studies but not in others. Because linkage analysis assesses allele sharing identical-by-descent among relatives instead of the association of a particular allele of an anonymous marker, we have performed a linkage study for bone BMD using microsatellite markers flanking the VDR locus. The present study explores whether or not relatives who share the chromosomal region containing the VDR gene have more similar bone density. Participants in the Framingham Osteoporosis Study (aged 37-89 years) who had undergone BMD testing were used to test for concordance of genotype with phenotype in the hip (femoral neck, Ward's area, trochanter) and lumbar spine (L2-L4) with adjustment for covariates. Multipoint quantitative trait linkage analysis using variance components methods was conducted with microsatellite markers flanking the VDR locus (GATA91H06, GATA5A09, GGAT2G06) in 332 extended families containing 1062 individuals with both bone density measures and marker data. In addition, quantitative trait sib-pair linkage analysis, with a marker (AFM345xf1) in close proximity to the VDR locus, was performed in a second sample of 169 sibships (n = 413), comprising 284 full-sib pairs. Neither analysis revealed evidence for linkage of this region to femoral neck, Ward's area, lumbar spine, and trochanter in age or sex BMI, and height-adjusted bone density measures. Additional adjustment for alcohol intake, caffeine consumption, smoking status, and estrogen supplement (female only) did not alter the results. The present study could not demonstrate linkage of BMD to chromosome 12q12-14. These findings suggest that neither the VDR gene nor other genes at this locus are likely to have a substantial impact upon bone density.

Prospective evaluation of the angiotensin-converting enzyme insertion/deletion polymorphism and the risk of stroke

BACKGROUND

The D/I polymorphism of the ACE gene has been studied in relation to a variety of cardiovascular disorders, including stroke. A number of small studies have been conducted, with inconsistent results. We investigated the association between ACE genotype and the incidence of stroke in a large, prospective, matched case-control sample from the Physicians' Health Study.

METHODS AND RESULTS

In the Physicians' Health Study, 348 subjects who had been apparently healthy at enrollment suffered a stroke during 12 years of follow-up, as determined from medical records and autopsy. A total of 348 cases were matched by age, time of randomization, and smoking habit to an equal number of controls (who had remained free of stroke). The D/I polymorphism was determined by polymerase chain reaction. Data were analyzed for the entire nested case-control sample, and also among a subgroup without a history of hypertension or diabetes mellitus, considered to be at low conventional risk (207 cases and 280 controls). All observed genotype frequencies were in Hardy-Weinberg equilibrium. The relative risk associated with the D allele was 1.11 (95% CI, 0.90 to 1.37; P=0.35), assuming an additive model in the matched analysis. Additional analyses assuming dominant or recessive effects of the D allele, as well as the analysis after stratification for low-risk status, showed no material as a statistically significant association.

CONCLUSIONS

The results of this large, prospective study indicate that the ACE D/I gene polymorphism is not associated with subsequent risk of stroke.

Insulin receptor exon 11+/- isoform mRNA in spontaneously hypertensive and adrenocorticotropin-hypertensive rats

OBJECTIVE

To test the hypothesis that insulin resistance of the spontaneously hypertensive rat (SHR) and adrenocorticotropin-hypertensive rat is related to a difference in the proportion of the functionally different, alternatively spliced exon 11 isoforms of the insulin receptor.

DESIGN

We determined the proportions of mRNA for the exon 11+ and exon 11- isoforms in various tissues of SHR and Wistar-Kyoto rats aged 3, 6, 9 and 12 weeks, which span the pre-hypertensive phase through to established hypertension, as well as in Sprague-Dawley rats with adrenocorticotropin-induced hypertension and Sprague-Dawley controls.

METHODS

Detection of mRNA involved a reverse-transcriptase polymerase chain reaction technique specific for each isoform and quantification was by slot and dot blot hybridization.

RESULTS

Mean proportions of exon 11+ mRNA in SHR, Wistar-Kyoto rats, adrenocorticotropin-hypertensive rats and Sprague-Dawley control rats at each age were 95% for liver, 82% for adipose tissue, 77% for kidney, 66% for adrenal, 53% for heart, 26% for cerebral cortex, 23% for hypothalamus, and 3% for skeletal muscle. There was also no difference in concentration of total insulin receptor mRNA.

CONCLUSIONS

The absence of any difference in proportions of insulin receptor mRNA isoforms argues against the hypothesis that an alteration of differential splicing plays a role in the models of hypertension studied.

Three candidate genes and angiotensin-converting enzyme inhibitor-related cough: a pharmacogenetic analysis

Unexplained, persistent cough limits the use of angiotensin-converting enzyme (ACE) inhibitors in a significant number of patients. It has been speculated that occurrence of this adverse effect is genetically predetermined; in particular, variants of the genes encoding ACE, chymase, and B2-bradykinin receptor have been implicated. To investigate this question, we determined genotypes for common polymorphisms for these three genes in subjects with a history of ACE inhibitor-related cough. Specificity of the adverse effect was confirmed by a blinded, double-crossover design protocol in which subjects were rechallenged with either lisinopril or placebo. In 99 case subjects and 70 control subjects (who failed to develop cough on rechallenge with ACE inhibitor) thus selected, frequencies for the ACE D and I alleles were 0.56 and 0.44 (cases) and 0.56 and 0.44 (controls), respectively; frequencies for chymase A and B alleles (absence/presence of BstXI site) were 0.56 and 0.44 (cases) and 0.46 and 0.54 (controls), respectively; frequencies for B2-bradykinin receptor + and - alleles (presence/absence of a 21 to 29 nonanucleotide sequence) were 0.52 and 0.48 (cases) and 0.53 and 0.47 (controls), respectively. All observed genotype frequencies were in Hardy-Weinberg equilibrium. There was no evidence for association between genotype at either gene examined and cough (adjusted for gender and age). Our data indicate that common genetic variants of ACE, chymase, and B2-bradykinin receptor do not explain the occurrence of ACE inhibitor-related cough.

Association analyses of S(A) gene variant in essential hypertensives

A gene designated S(A) has been implicated in hypertension (HT) in rat genetic models and Japanese HT patients. However, a linkage study in whites was negative. Because of the limitations of genetic analyses, confirmation in different settings is imperative. Therefore, we conducted a cross-sectional case-control study involving 106 HT and 96 normotensive (NT) white subjects. A polymerase chain reaction technique was developed for PstI restriction fragment length polymorphism (RFLP) determination. We could find no association of this RFLP with HT (frequency of minor allele, A2 = 0.11 in HTs v 0.07 in NTs). However, A2 displayed an association with increase in body mass index in HTs: for a body mass index mean of 26 kg/m2 or more, A2 = 0.17 compared to 0.06 for body mass index of less than 26 kg/m2 (chi2 = 6.4, P = .01; odd ratio 3.4, 95% confidence interval 1.2 to 10.0); for a body mass index of 28 kg/m2 or more, A2 = 0.20 (chi2 = 10.4, P = .001; odds ratio 4.0, 95% confidence interval 1.5 to 10.5). Furthermore, A2 tracked significantly with elevation in body mass index in the HTs (F = 4.8, P = .01 by one-way ANOVA). In conclusion, we could find no association of S(A) genotype with HT, but obtained preliminary evidence for a possible association with variation in body mass index in a severely affected HT group with a strong family history of HT.

Construction and characterization of a 10-genome equivalent yeast artificial chromosome library for the laboratory rat, Rattus norvegicus

Increasing attention has been focused in recent years on the rat as a model organism for genetic studies, in particular for the investigation of complex traits, but progress has been limited by the lack of availability of large-insert genomic libraries. Here, we report the construction and characterization of an arrayed yeast artificial chromosome (YAC) library for the rat genome containing approximately 40,000 clones in the AB1380 host using the pCGS966 vector. An average size of 736 kb was estimated from 166 randomly chosen clones; thus the library provides 10-fold coverage of the genome, with a 99.99% probability of containing a unique sequence. Eight of 39 YACs analyzed by fluorescence in situ hybridization were found to be chimeric, indicating a proportion of about 20-30% of chimeric clones. The library was spotted on high-density filters to allow the identification of YAC clones by hybridization and was pooled using a 3-dimensional scheme for screening by PCR. Among 48 probes used to screen the library, an average of 9.3 positive clones were found, consistent with the calculated 10-fold genomic coverage of the library. This YAC library represents the first large-insert genomic library for the rat. It will be made available to the research community at large as an important new resource for complex genome analysis in this species.

Association of angiotensin II type 1 receptor gene polymorphism with essential hypertension

The renin-angiotensin system is involved in control of blood pressure and salt and fluid homeostasis. Genes for components of this system have been of major focus in research on the causation of the common, complex, polygenic trait, essential hypertension (HT). Association of an A-->C variant at nucleotide 1166 of the angiotensin II type 1 receptor (AT1R) gene with HT, but an absence of linkage of this locus with this disease, has been reported recently. Since confirmation in a different setting is imperative, we performed a cross-sectional case-control study of the A1166C variant in a well-characterized group of 108 Caucasian HT subjects with a strong family history (two affected parents) and early onset disease. Genotyping was by mismatch polymerase chain reaction/BfrI restriction fragment length polymorphism analysis. Frequency of the C1166 allele was 0.40 in HTs and 0.29 in normotensives. The difference in genotype (chi 2 = 13, P = 0.0015) and allele (chi 2 = 5.3, P = 0.02) frequencies between the two groups was significant (odds ratio for CC vs AA + AC = 7.3 [95% CI, 1.9-31.9). The present results implicate the AT1R gene, or a locus in linkage disequilibrium with the variant tested, in the causation of essential HT.

Effect of angiotensin-converting enzyme genotype on renin-angiotensin components in hypertensives

Plasma angiotensin-converting enzyme (ACE) tracks with the deletion allele of an insertion/deletion (I/D) polymorphism of the ACE gene. The aim of the present study was to determine plasma renin and angiotensinogen for each ACE genotype in 54 hypertensive and 96 normotensive subjects. Plasma renin was reduced by 52 +/- 15 S.E.% in DD and by 24 +/- 12% in ID hypertensives when compared to II hypertensives (P < 0.05 by one-way ANOVA), but in the normotensive subjects, renin values were similar for each genotype. Plasma angiotensinogen did not differ across ACE genotypes, but was elevated by 25 +/- 3 S.E.% in hypertensives and showed a significant correlation with blood pressure. In conclusion, although renin does not differ significantly between ACE genotypes of normotensives, a reciprocal relationship may exist between plasma renin and plasma ACE in hypertensives.

No difference in the proportion of insulin receptor exon 11 +/- isoform mRNA in the liver of rats after development of hypertension

1. There are two functionally different isoforms of the insulin receptor in humans and rats. We hypothesized that a change in their relative proportion could be of relevance to insulin resistance in hypertension. 2. A reverse-transcriptase polymerase chain reaction technique was established for the detection of mRNA for the exon 11+ and exon 11- isoforms and the proportion of each was determined in 3, 6, 9 and 12 week old spontaneously hypertensive rats and Wistar-Kyoto rats, as well as adrenocorticotrophin (ACTH)-induced hypertensive rats and controls. 3. The proportion of the exon 11+ form (approximately 95%) and exon 11- form (approximately 5%) was similar in the liver of all rats studied. 4. We conclude that there is no change in insulin receptor isoform expression in the liver in the models of hypertension studied.

Association analyses of NsiI RFLP of human insulin receptor gene in hypertensives

Plasma angiotensinogen is elevated in essential hypertensives and shows a strong correlation with blood pressure. Patients with hypertension often display insulin resistance and we have found previously an association of a RsaI RFLP in intron 9 of the insulin receptor gene (INSR) with hypertension. Since insulin resistance is accompanied by hyperinsulinaemia and insulin can stimulate angiotensinogen production, we hypothesized that hypertension-associated genotypes of INSR may be associated with elevation in plasma angiotensinogen. We used PCR to detect a NsiI RFLP in exon 8 of INSR and examined its relationship with plasma angiotensinogen, as well as hypertension, in 134 Caucasian hypertensives with two hypertensive parents and in 126 normotensives. Plasma angiotensinogen tracked weakly with the major allele of the NsiI RFLP in hypertensives (p = 0.08). Moreover, the frequency of this allele was higher in lean hypertensives than in lean normotensives (p < 0.05) and in normolipidaemic hypertensives than normolipidaemic normotensives (p < 0.02). The present study thus suggests that there could be a relationship of plasma angiotensinogen with INSR genotype, and of each with hypertension.

Association of HincII RFLP of low density lipoprotein receptor gene with obesity in essential hypertensives

Obese (BMI > or = 26 kg/m2; n = 51) and lean (BMI < 26 kg/m2; n = 61) Caucasian patients with severe, familial essential hypertension, were compared with respect to genotype and allele frequencies of a HincII RFLP of the low density lipoprotein receptor gene (LDLR). A similar analysis was performed in obese (n = 28) and lean (n = 68) normotensives. A significant association of the C allele of the T-->C variant responsible for this RFLP was seen with obesity (chi 2 = 4.6, P = 0.029) in the hypertensive, but not in the normotensive, group (odds ratio = 3.0 for the CC genotype and 2.7 for CT). Furthermore, BMI tracked with genotypes of this allele in the hypertensives (P = 0.046). No significant genotypic relationship was apparent for plasma lipids. Significant linkage disequilibrium was, moreover, noted between the HincII RFLP and an ApaLI RFLP (chi 2 = 33, P < 0.0005) that has previously shown even stronger association with obesity (odds ratio 19.6 for cases homozygous for the susceptibility allele and 15.2 for heterozygotes). The present study therefore adds to our previous evidence implicating LDLR as a locus for obesity in patients with essential hypertension.

Similarity of blood pressure for each genotype of the insertion/deletion polymorphism of the dipeptidyl carboxypeptidase-1 gene in different age groups of patients with severe, familial essential hypertension

1. The association of alleles of an insertion/deletion polymorphism (I/D) of the dipeptidyl carboxypeptidase-1 gene with hypertension is controversial. If a particular allele makes a major contribution to blood pressure, then hypertensives homozygous for this allele could be expected to have higher high blood pressure than those homozygous for the alternate allele. 2. The present study examined this hypothesis by comparing pretreatment blood pressures of hypertensives who had been genotypes for the I/D polymorphism. Blood pressures for different age groups (< 50, 50-59 and > or = 60 years) were also examined for each genotype. In addition, several other parameters were examined. 3. Systolic blood pressures were found to be 167 +/- 3, 167 +/- 3 and 170 +/- 6 mmHg (mean +/- s.e.) for the genotypes II, ID and DD, respectively. Diastolic blood pressures were 113 +/- 4, 111 +/- 2 and 111 +/- 4, for the respective genotypes. One-way ANOVA showed that the respective blood pressure values did not differ significantly across genotypes. Blood pressures for different age groups of hypertensives were also similar. 4. In addition, body mass index, mean age and sex did not differ between genotypes, either for the group as a whole or for the different age groups. 5. In conclusion, the present study could find no evidence to support a genetic association between the I/D polymorphism of DCP1 and blood pressure in a group with severe, familial hypertension living in Sydney.

Frequencies of variants of candidate genes in different age groups of hypertensives

1. In severe, familial hypertension, we have reported that the proportion of patients homozygous for the deletion allele of an insertion/deletion polymorphism of the angiotensin I-converting enzyme gene is markedly decreased in older age groups, suggesting that this genotype is associated with increased risk of premature death. The aim of the present study was to examine the relationship with age, of variants of other genes that encode proteins having an influence on the cardiovascular system. 2. Genotypes of 13 different variants at 12 relevant genetic loci were determined by either Southern blotting, followed by hybridization probing, or polymerase chain reaction techniques, as appropriate, using genomic DNA extracted from blood leukocytes. Genotype numbers were then assigned to the age categories of < 50, 50-59 and > or = 60 years. 3. Polymorphisms at the atrial natriuretic factor, antithrombin III, renin, angiotensinogen, neuropeptide-Y Y1 receptor, insulin, alpha 2-adrenoceptor, beta 1-adrenoceptor, growth hormone, low density lipoprotein receptor, insulin receptor and renal kallikrein gene loci were found to display similar allele frequencies in each age group of hypertensives, as well as in normotensive controls. 4. In conclusion, we were unable to detect any difference with age for a range of variants of genes whose products have cardiovascular significance, suggesting that, like most polymorphisms, they carry no selective survival advantage or disadvantage in the hypertensive and normotensive population groups studied.

Different frequencies of angiotensin-converting enzyme genotypes in older hypertensive individuals

The frequency of the D allele of an insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene has been reported to be elevated in myocardial infarction and other patients. We therefore hypothesized that death rate of DD individuals should be increased in the population as a whole and this should be evident as a decrease in DD frequency with age. This hypothesis was tested in 118 Caucasian subjects who were already at high risk of cardiovascular events by having severe, early onset, familial hypertension (HT). A group of 196 age-, sex- and body mass index-matched normotensives (NTs) was used as a control. In the NT group II, ID, and DD genotype frequencies were similar for different age groups. DD frequency was 0.42 in NTs, but in HTs was 0.28, 0.26, and 0.10 for the age groups < 50, 50-59, and > or = 60 yr, respectively. Corresponding D allele frequencies were 0.52, 0.46, and 0.40 in the respective age groups of HTs, compared with 0.61 in NTs (by chi 2-analysis, P = 0.1, 0.047, and 0.0006, respectively). In HTs aged > or = 60, DD frequency was only 14% of expected. Plasma ACE activity tracked similarly with I/D genotype in HTs (P = 0.027; n = 35) as in NTs (P = 0.0001; n = 94) and Michaelis constant was identical for DD and II. Neither blood pressure, body mass index, nor sex bore any relationship with I/D genotype. In conclusion, in a group of severely HT patients not selected for cardiac pathology, there appeared to be a marked, selective decrease, in subgroups of increasing age, in frequency of the ACE DD genotype. One possibility suggested by this data might be that DD increases risk of premature death, at least in HTs who have two HT parents.

Significant relationships of plasma lipids and body mass index with polymorphisms at the linked low-density-lipoprotein receptor gene and insulin receptor gene loci (19p13.2) in essential hypertensive patients

1. Recent molecular genetic studies have implicated the low-density-lipoprotein receptor gene locus (LDLR, at chromosome 19p13.2) in obesity in essential hypertensive patients and in the atherogenic lipoprotein phenotype. The present study examined genotypes for the obesity-associated ApaLI restriction fragment length polymorphism of LDLR, and genotypes for a hypertension-associated RsaI restriction fragment length polymorphism at the insulin receptor gene (INSR) locus, which is linked to LDLR, in relation to plasma lipids, body mass index and blood pressure in 27 obese and 57 non-obese Caucasians with severe essential hypertension, selected on the basis of having parents who were both hypertensive, and in 25 obese and 45 non-obese normotensive subjects selected on the basis of having parents who were both normotensive after the age of 50 years. 2. Plasma triacylglycerol and low-density-lipoprotein-cholesterol were elevated in hypertensive patients, but did not differ between the obese and non-obese hypertensive groups. Significant positive correlations were seen between body mass index and triacylglycerol and low-density-lipoprotein-cholesterol in the obese and non-obese hypertensive patients, respectively. In addition, obese hypertensive patients had significantly higher diastolic blood pressure than non-obese hypertensive patients. 3. The eight obese hypertensive patients who were homozygous for the obesity-associated 6.6 kb allele of the ApaLI restriction fragment length polymorphism of LDLR ('6.6. kb homozygotes') had a significantly higher body mass index [34 +/- 6.0 (SD) kg/m2] than the 18 heterozygotes (29 +/- 2.7 kg/m2) and the single subject who was homozygous for the 9.4 kb allele (29 kg/m2) (P = 0.012 by one-way analysis of variance). The body mass index of the eight hypertensive 6.6 kb homozygotes was also greater than the body mass index of 29 +/- 2.4 kg/m2 observed for the eight obese normotensive 6.6 kb homozygotes. In addition, the eight obese hypertensive 6.6 kb homozygotes had a higher plasma triacylglycerol [4.2 +/- 0.77 (SEM) mmol/l] than the 18 obese hypertensive heterozygotes (2.4 +/- 0.33 mmol/l; P = 0.045). Non-obese hypertensive patients showed no significant genotypic differences in relation to the LDLR restriction fragment length polymorphism. 4. In the normotensive group, however, the frequency of the 6.6 kb allele of the LDLR ApaLI restriction fragment length polymorphism in obese subjects (0.54) was not significantly greater than in non-obese subjects (0.48) [cf. the significantly (P = 0.004( different values of 0.63 and 0.39, respectively, in obese and non-obese hypertensive patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Insertion variant in intron 9, but not microsatellite in intron 2, of the insulin receptor gene is associated with essential hypertension

OBJECTIVE

To determine whether a microsatellite polymorphism of the insulin receptor gene (INSR) is associated with essential hypertension, as has been demonstrated previously for an RsaI restriction fragment length polymorphism (RFLP), and to examine blood pressure and plasma lipid profiles in relation to genotype.

DESIGN AND METHODS

The study involved 75 Caucasian, non-diabetic hypertensive patients whose parents were both hypertensive, and 75 age-matched normotensive subjects whose parents were each normotensive after the age of 50 years. Genotypes for the microsatellite polymorphism were determined for each subject using leucocyte DNA and a polymerase chain reaction method. Other parameters, including pretreatment blood pressure, body mass index and plasma lipids, were also determined.

RESULTS

Comparison of microsatellite data for the eight genotypes and four alleles that were detected showed no significant difference by chi 2 analysis, either between the hypertensive and normotensive groups, or between obese and non-obese subgroups of hypertensives. This is in contrast to the significantly higher frequency seen for the R1- allele of an RsaI RFLP of INSR: 0.71 in the hypertensive group compared with 0.56 in the normotensive group. R1- allele frequency was elevated in all age groups of hypertensives and did not differ between obese and non-obese subgroups. The non-obese hypertensives also had different plasma lipid profiles according to genotypes of the RFLP, with higher total and low-density lipoprotein-cholesterol in patients having the hypertension-associated R1- allele of the intron 9 polymorphism. Moreover, systolic blood pressure was significantly greater in patients carrying the R1- allele and aged > or = 60 years.

CONCLUSIONS

The present study allows definition of the hypertension-associated variants of INSR as those which are in linkage disequilibrium with a (CA)-repeat insertion polymorphism in intron 9 of the large, 22 exon, > 120-kb gene, but not those associated with a polymorphism in the second intron.

Short report: insertion variant in intron 9, but not microsatellite in intron 2, of the insulin receptor gene is associated with essential hypertension

OBJECTIVE

To determine whether a microsatellite polymorphism of the insulin receptor gene (INSR) is associated with essential hypertension, as has been demonstrated previously for an Rsal restriction fragment length polymorphism (RFLP), and to examine blood pressure and plasma lipid profiles in relation to genotype.

DESIGN AND METHODS

The study involved 75 Caucasian, non-diabetic hypertensive patients whose parents were both hypertensive, and 75 age-matched normotensive subjects whose parents were each normotensive after the age of 50 years. Genotypes for the microsatellite polymorphism were determined for each subject using leucocyte DNA and a polymerase chain reaction method. Other parameters, including pretreatment blood pressure, body mass index and plasma lipids, were also determined.

RESULTS

Comparison of microsatellite data for the eight genotypes and four alleles that were detected showed no significant difference by chi 2 analysis, either between the hypertensive and normotensive groups, or between obese and non-obese subgroups of hypertensives. This is in contrast to the significantly higher frequency seen for the R1- allele of an Rsal RFLP of INSR: 0.71 in the hypertensive group compared with 0.56 in the normotensive group. R1- allele frequency was elevated in all age groups of hypertensives and did not differ between obese and non-obese subgroups. The non-obese hypertensives also had different plasma lipid profiles according to genotypes of the RFLP, with higher total and low-density lipoprotein-cholesterol in patients having the hypertension-associated R1- allele of the intron 9 polymorphism. Moreover, systolic blood pressure was significantly greater in patients carrying the R1- allele and aged > or = 60 years.

CONCLUSIONS

The present study allows definition of the hypertension-associated variants of INSR as those which are in linkage disequilibrium with a (CA)-repeat insertion polymorphism in intron 9 of the large, 22 exon, > 120-kb gene, but not those associated with a polymorphism in the second intron.

Neuropeptide-Y Y1 receptor gene polymorphism: cross-sectional analyses in essential hypertension and obesity

Neuropeptide Y increases blood pressure and appetite, disorders of which have a genetic component. The present study examined the neuropeptide-Y Y1 receptor gene (NPYY1R) for involvement in essential hypertension (HT) and obesity. Frequency of alleles of the only known variant, involving a point mutation in intron 1, was determined by PCR and PstI digestion. Minor allele frequency was 0.37 in 75 HT offspring of two HT parents, compared with 0.35 in 86 normotensives (NTs) ( chi 2 = 0.11; P = 0.73). In obese and lean HTs frequency was 0.40 and 0.35 (chi 2 = 0.51; P = 0.46); and was 0.38 and 0.34 in obese and lean NTs (chi 2 = 0.16; P = 0.69). In conclusion, variant(s) in linkage disequilibrium with the NPYY1R RFLP are not involved in HT or obesity.

Independent, marked associations of alleles of the insulin receptor and dipeptidyl carboxypeptidase-I genes with essential hypertension

1. There is evidence to suggest that essential hypertension is a polygenic disorder and that it arises from yet-to-be-identified predisposing variants of certain genes that influence blood pressure. The cloning of various hormone, enzyme, adrenoceptor and hormone receptor genes whose products are involved in blood pressure control and the identification of polymorphisms of these has permitted us to test their genetic association with hypertension. 2. Cross-sectional analyses of a number of candidate gene markers were performed in hypertensive and normotensive subjects who were selected on the basis of both parents being either hypertensive or normotensive, respectively, and the difference in total alleles on all chromosomes for each polymorphism between the hypertensive and normotensive groups was tested by chi 2 analysis with one degree of freedom. 3. A marked association was observed between hypertension and insertion alleles of polymorphisms of the insulin receptor gene (INSR) (P < 0.0040) and the dipeptidyl carboxypeptidase-1 (angiotensin I-converting enzyme; kininase II) gene (DCP1) (P < 0.0018). No association with hypertension was evident, however, for polymorphisms of the growth hormone, low-density lipoprotein receptor, renal kallikrein, alpha 2- and beta 1-adrenoreceptor, atrial natriuretic factor and insulin genes. 4. All but one of the hypertensive subjects had at least one of the hypertension-associated alleles, and although subjects homozygous for both were three times more frequent in the hypertensive group, examination of the nine possible genotypes suggested that the INSR and DCP1 alleles are independent markers for hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

Marked association of a RFLP for the low density lipoprotein receptor gene with obesity in essential hypertensives

RFLPs at the low density lipoprotein receptor locus (LDLR) display marked linkage disequilibrium between each other. Cross-sectional analysis of a bi-alleleic ApaLI RFLP of LDLR showed that the 9.4- and 6.6-kb alleles were present in similar frequency between a group of 84 Caucasian essential hypertensive (HT) and a group of 96 normotensive subjects whose parents each had a similar blood pressure status at age > or = 50. After subdividing HTs into lean and obese, however, the frequency of the 6.6-kb allele in the 27 HTs with BMI > or = 26 kg/m2 was 0.63, compared with 0.39 for HTs with BMI < 26 (chi 2 = 8.8; P = 0.004). The difference in genotype frequencies was even more striking (chi 2 = 23; P = 0.00008), with a virtual absence of 9.4-kb homozygotes in the obese HT group (1 vs 22). Genetic variation at LDLR (19p13.2) is thus associated with obesity in HT.

Association of a polymorphism of the angiotensin I-converting enzyme gene with essential hypertension

Angiotensin I-converting enzyme (ACE) is responsible for production of angiotensin II and breakdown of kinins, leading to increased blood pressure (BP). Furthermore, ACE inhibitors are effective antihypertensive agents. A 287 bp insertion/deletion polymorphism in intron 16 of the ACE gene (ACE) was examined by PCR in a cross-sectional study of 80 hypertensive (HT) and 93 normotensive (NT) subjects whose parents had a similar BP status at age greater than or equal to 50. The frequency of the insertion allele was 0.56 in HTs and 0.41 in NTs, and the difference between observed alleles in all subjects in each group was significant (chi 2 = 7.6, P less than 0.01). The data thus provide evidence in favour of an association of HT with a polymorphism at the ACE locus (17q23), so implicating this locus, and possibly a genetic variant of ACE itself, in human essential hypertension.

Association of a RFLP for the insulin receptor gene, but not insulin, with essential hypertension

Insulin has cardiovascular actions and patients with essential hypertension display insulin resistance. A cross-sectional study of the R1 RFLP of the insulin receptor gene (INSR) was carried out in 67 hypertensive (HT) and 75 normotensive (NT) subjects whose parents had a similar blood pressure status at age greater than or equal to 50. The frequency of the minor (+) allele was 0.31 in HTs and 0.44 in NTs, and the difference between observed alleles in all subjects in each group was significant (chi 2 = 4.8, P less than 0.05). Allele frequencies of a BglI RFLP of the insulin gene, however, did not differ between the HT and NT groups. The data thus provide evidence in favour of an association of HT with a polymorphism at the INSR locus (19p13.3-13.2), so implicating this locus, and possibly a genetic variant of the insulin receptor itself, in HT.

Association and linkage analyses of restriction fragment length polymorphisms for the human renin and antithrombin III genes in essential hypertension

Essential hypertension is a highly hereditable disorder in which genetic influences predominate over environmental factors. The molecular genetic profiles which predispose to essential hypertension are not known. In rats with genetic hypertension, there is some recent evidence pointing to linkage of renin gene alleles with blood pressure. The genes for renin and antithrombin III belong to a conserved synteny group which, in humans, spans the q21.3-32.3 region of chromosome I and, in rats, is linkage group X on chromosome 13. The present study examined the association of particular human renin gene (REN) and antithrombin III gene (AT3) polymorphisms with essential hypertension by comparing the frequency of specific alleles for each of these genes in 50 hypertensive offspring of hypertensive parents and 91 normotensive offspring of normotensive parents. In addition, linkage relationships were examined in hypertensive pedigrees with multiple affected individuals. Alleles of a REN HindIII restriction fragment length polymorphism (RFLP) were detected using a genomic clone, lambda HR5, to probe Southern blots of HindIII-cut leucocyte DNA, and those for an AT3 PstI RFLP were detected by phATIII 113 complementary DNA probe. The frequencies of each REN allele in the hypertensive group were 0.76 and 0.24 compared with 0.74 and 0.26 in the normotensive group. For AT3, hypertensive allele frequencies were 0.49 and 0.51 compared with normotensive values of 0.54 and 0.46. These differences were not significant by chi 2 analysis (P greater than 0.2).(ABSTRACT TRUNCATED AT 250 WORDS)

A locus on the long arm of chromosome 1 as a possible cause of essential hypertension

1. None of the genes responsible for essential hypertension has been identified. Recent work in genetically hypertensive rats has shown linkage of blood pressure with alleles of the renin gene. Since the renin gene is a member of a conserved synteny group that in humans spans chromosome 1q21.3-32.3 and includes the gene for antithrombin III (AT3), we used linkage studies to examine the relationship between alleles of AT3 and hypertension in a family having 10 affected members. 2. From the lod score obtained at a recombination fraction of zero the odds for linkage of AT3 and hypertension in this family were calculated as 6:1 in favour of linkage. This result provides grounds for further examination of the possible role of the 1q23 locus in the aetiology of essential hypertension.