Peroxisome proliferator-activated receptor-gamma2-Pro12Ala and endothelial nitric oxide synthase-4a/b gene polymorphisms are associated with essential hypertension:

Association of endothelial nitric oxide synthase intron 4a/b gene polymorphisms and hypertension: a systematic review and meta-analysis

OBJECTIVE

We conducted meta-analysis of relevant case-control trials to determine the association between endothelial nitric oxide synthase (eNOS) intron 4a/b gene polymorphisms and hypertension susceptibility.

METHODS

We searched the PubMed, Cochrane, and Embase databases using relevant keywords and reviewed pertinent literature sources. All articles published up to July 2019 were considered for inclusion. Based on the qualified studies, we performed a meta-analysis of the associations between eNOS intron 4a/b polymorphisms and the risk of hypertension.

RESULTS

Fourteen studies were included in this meta-analysis, including 3344 cases and 3377 controls. The eNOS intron 4a/b locus was significantly associated with increased susceptibility to hypertension (including essential hypertension) in the overall population, according to dominant, allelic, homozygote, heterozygote, and regressive models, in the mixed population according to the regressive model, and in Caucasians according to the dominant, allelic, heterozygote, and regressive models. The eNOS intron 4a/b locus was also significantly associated with increased susceptibility to essential hypertension in the mixed population according to the heterozygote model.

CONCLUSION

eNOS intron 4a/b gene polymorphisms increase susceptibility to hypertension, including essential hypertension.

Pro12Ala PPAR-γ2 and +294T/C PPAR-δ Polymorphisms and Association with Metabolic Traits in Teenagers from Northern Mexico

Peroxisome proliferator-activated receptors (PPARs) play roles in glucose and lipid metabolism regulation. Pro12Ala PPAR-γ2 and +294T/C PPAR-δ have been associated with dyslipidemia, hyperglycemia and high body mass index (BMI). We compared metabolic traits and determined associations with Pro12Ala PPAR-γ2 or +294T/C PPAR-δ polymorphism among teenagers from different ethnicity. Four hundred and twelve samples with previous biochemical and biometric measurements were used. Genomic DNA from peripheral blood was extracted and analyzed by end-point PCR for Pro12Ala PPAR-γ2. The +294T/C PPAR-δ PCR product was also digested with Bsl I. Two genotype groups were formed: major allele homozygous and minor allele carriers. Pro12Ala PPAR-γ2 G minor allele frequencies were: 10% in Mestizo-1, 19% in Mestizo-2, 23% in Tarahumara, 12% in Mennonite, and 17% in the total studied population. The +294T/C PPAR-δ C minor allele frequencies were: 18% in Mestizo-1, 20% in Mestizo-2, 6% in Tarahumara, 13% in Mennonite, and 12% in the total studied population. Teenagers with PPAR-γ2 G allele showed a greater risk for either high waist/height ratio or low high-density lipoprotein; and, also had lower total cholesterol. Whereas, PPAR-γ2 G allele showed lower overweight/obesity phenotype (BMI Z-score) frequency, PPAR-δ C allele was a risk factor for it. Metabolic traits were associated with both PPAR polymorphisms.

Association between peroxisome proliferator-activated receptor γ-2 gene Pro12Ala polymorphisms and risk of hypertension: an updated meta-analysis

Previous studies investigate the relationship between peroxisome proliferator-activated receptor γ-2 (PPAR) gene Pro12Ala polymorphisms and risk of hypertension. However, the number of available studies was extremely limited. We updated this evidence and gave more significant results. We performed comprehensive computer-based searches in the PubMed, Web of Science, Embase, Google Scholar, the Cochrane library, Wanfang database, China National Knowledge Infrastructure, and China Biological Medicine Database. All studies that reported the association between the PPARγ2Pro12Ala polymorphisms and hypertension were identified. Twenty-one studies were finally included in the present study. In the domain model, the PPARγ1Pro12Ala polymorphism was not associated with hypertension (odds ratio (OR) = 0.85, 95% confidence interval (CI): 0.71-1.03, P=0.108). The significant relationship was found in the recessive model (OR = 0.67, 95% CI: 0.53-0.85), in the additive model (OR = 0.61, 95% CI: 0.48-0.77), and in the allele genetic model (OR = 0.81, 95% CI: 0.66-0.99). Subgroup analysis indicated that the PPARγ1Pro12Ala polymorphism from the all gene models was also not related to the risk of hypertension in Caucasians. In Asians, however, the results (P=0.002; I² = 57.6%) suggested a significant relationship between PPARγ1Pro12Ala and hypertension in the domain model (OR = 0.80, 95% CI: 0.65-0.99), in the recessive model (OR = 0.57, 95% CI: 0.44-0.75), in the additive model (OR = 0.51, 95% CI: 0.39-0.66), and in the allele model (OR = 0.75, 95% CI: 0.60-0.94). The PPARγ1Pro12Ala polymorphism could affect the risk of primary hypertension amongst Asians. The A allele gene was a protective genotype for primary hypertension. The PPARγ1Pro12Ala polymorphism was not associated with hypertension amongst Caucasians.

Quantitative evaluation of PPAR-γ2 Pro12Ala polymorphism with hypertension

BACKGROUND

The peroxisome proliferator-activated receptor γ2 (PPARγ2)Pro12Ala polymorphism has been reported to be associated with hypertension. However, relevant studies have shown inconsistent results.

METHODS

To quantitatively evaluate the relationship between the PPARγ2Pro12Ala polymorphism and hypertension risk, we conducted a meta-analysis based on all available studies selected from Scopus, Web of Science, PubMed, Chinese National Knowledge Infrastructure, and Wanfang databases.

RESULTS

In all, 13 studies were finally included in this meta-analysis. In the allelic model (Ala vs. Pro), the Ala allele of PPARγ2 Pro12Ala polymorphism was associated with hypertension (Odds Ratio [OR] = 0.723, 95% confidence interval [CI] = 0.607-0.861). Sensitivity analysis and exclusion of studies with poor quality scores or controls complicated by other diseases confirmed the validity of this association. Moreover, the PPARγ2Pro12Ala polymorphism was associated with hypertension in the codominant (OR = 0.710, 95% CI = 0.626-0.806), recessive (OR = 0.561, 95% CI = 0.418-0.754), and dominant (OR = 0.693, 95% CI = 0.577-0.833) models.

CONCLUSION

The Ala allele appears to have a protective effect against hypertension and a dominant function.

Associations between PPARG polymorphisms and the risk of essential hypertension

Background

Peroxisome proliferator-activated receptor gamma (PPARG) plays an important role in the pathogenesis and maintenance of essential hypertension (EH). It has been suggested that polymorphisms of PPARG are associated with the risk of EH. However, findings to date remain controversial. To elucidate the associations between the PPARG Pro12Ala and C161T polymorphisms and EH risk, a meta-analysis was carried out.

Methods

A comprehensive literature search of PubMed, Embase, CNKI (Chinese National Knowledge Infrastructure), VIP and Wanfang databases was conducted. The pooled odds ratios (ORs) and 95% confidence interval (CI) were calculated to estimate the size of the effect using the random-effects model. At the same time, the pooled standardized mean difference (SMD) with 95% CI was used for the meta-analysis of the PPARG Pro12Ala polymorphism and blood pressure.

Results

Finally, Fifteen papers (seventeen studies) including 4,151 cases and 4,997 controls to evaluate the association of the PPARGPro12Ala polymorphism and EH risk, were included in this study. Overall, the results suggested that Ala allele was associated with the decreased EH risk (for allelic model, OR = 0.757, 95%CI: 0.624–0.918, P = 0.005; for dominant model, OR = 0.771, 95%CI: 0.627–0.946, P = 0.013). The subgroup analysis stratified by ethnicity showed that the significant association between the PPARG Pro12Ala polymorphism and EH was only detected in the Asian subgroup. There was no difference in blood pressure values between Ala carriers and non-carriers. For the C161T polymorphism, only 5 studies comprising 1,118 cases and 1,357 controls met the inclusion criteria. The overall results showed that the PPARG C161T polymorphism was not associated with the risk of EH. But in the subgroup analysis, we found that the PPARG C161T polymorphism significantly associated with the risk of EH in the Asian subgroup (for allelic model, OR = 0.719, 95% CI: 0.537–0.963, P = 0.027; for dominant model, OR = 0.653, 95% CI: 0.439–0.972, P = 0.036).

Conclusion

Our meta-analysis suggested that the PPARG polymorphisms might be associated with the risk of EH.

PPARG gene C161T CT/TT associated with lower blood lipid levels and ischemic stroke from large-artery atherosclerosis in a Han population in Guangdong

OBJECTIVE

Peroxisome proliferator-activated receptor gamma (PPARG) is a transcription factor involved in atherosclerosis and related diseases. In this study, we aimed to investigate whether PPARG C161T was associated with lipid levels and large-artery atherosclerosis (LAA) ischemic stroke in a Han Chinese population in Guangdong province.

METHODS

The genotype PPARG C161T in 149 LAA ischemic stroke patients and 125 healthy controls was examined by polymerase chain reaction-restriction fragment length polymorphism (RFLP) assay. Associations with LAA ischemic stroke were analyzed for PPARG C161T genotype, total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), and a logistic regression analysis was performed to identify risk factors for LAA ischemic stroke.

RESULTS

The frequency of CC was higher than that of CT + TT and was significantly associated with LAA ischemic stroke. In both the LAA and control groups, TC and LDL-C levels were significantly higher in the CC type than the CT + TT, but TG and HDL-C levels were comparable. The only verified independent risk factors for LAA ischemic stroke were ischemic heart disease (OR: 2.784, 95% CI: 1.377-5.632; p = 0.004) and systolic blood pressure (OR: 1.014, 95% CI: 1.001-1.026; p = 0.029); the PPARG C161T allele was not independently associated with an increased risk of LAA ischemic stroke (OR = 0.697, 95% CI: 0.372-1.305; p = 0.260).

CONCLUSION

In this Han population, PPARG C161T CT/TT was associated with LAA ischemic stroke and lower levels of blood TC and LDL-C, but was not an independent risk factor for LAA ischemic stroke.

Association of PPAR-γ2 and β3-AR Polymorphisms With Postmenopausal Hypertension

The aim of this study was to test the association of peroxisome proliferator-activated receptor (PPAR-γ2) (Pro12Ala, C1431T) and β3-AR (Trp64Arg) polymorphisms with metabolic, nutritional, and blood pressure parameters in 271 postmenopausal women (151 hypertensive and 120 normotensive controls). The TaqMan genotyping assay and restriction fragment length polymorphism methods were used to determine the distributions of selected alleles and genotype frequencies. Nutritional status was determined by a bioimpedance method and dietary habits were assessed via 7-day dietary recall. The distribution of selected genotypes and allele frequencies did not differ between hypertensive women and normal controls after analysis by chi-square test. The postmenopausal hypertensive women were older and had higher body fat mass, serum glucose, and triglyceride levels. The cluster analysis showed that the hypertensive group with Pro12Pro genotype had highest pulse pressure and mean arterial pressure values when compared with Pro12Ala patients. In the logistic regression analysis, blood glucose (Pro12Ala polymorphism) and energy intake (C1431Tand T1431T polymorphisms) determined hypertension.

Endothelial nitric oxide synthase polymorphism influences renal allograft outcome

BACKGROUND

Atherosclerotic lesions within the graft are considered to be a major cause of interstitial fibrosis/tubular atrophy (IF/TA). We evaluated the factors that influence the development of IF/TA and three- and five-yr graft survival including nitric oxide synthase (eNOS) and angiotensin II type 1 and type 2 receptor gene polymorphism.

METHODS

Seventy-one male and 35 female patients (age: 34.9 ± 11.2 yr) who underwent living-related renal transplantation were included. Angiotensin type 1 and type 2 receptor gene polymorphisms and eNOS intron 4 gene polymorphism were analyzed. The pre- and post-transplant laboratory data, patient characteristics, acute rejection episodes, and presence of IF/TA were evaluated.

RESULTS

Patients with the bb allele of eNOS gene had a lower prevalence of post-transplant third year (12.6% and 38.5%, p = 0.005) and fifth year IF/TA (46.6% and 82.3%, p = 0.02) and a lower incidence of five-yr graft failure (35.4% and 55.6%, p < 0.005). The eNOS gene polymorphism was independent and was the most prominent factor associated with third and fifth year IF/TA (p = 0.01, RR: 29.72, and p = 0.03, RR: 4.1, respectively). No significant relationship existed when angiotensin II gene polymorphisms were considered.

CONCLUSIONS

We concluded that recipient eNOS gene polymorphism can predict IF/TA, and the presence of the bb allele is associated with better graft outcome.

An updated meta-analysis of endothelial nitric oxide synthase gene: three well-characterized polymorphisms with hypertension

Background

Numerous individually underpowered association studies have been conducted on endothelial nitric oxide synthase (eNOS) genetic variants across different ethnic populations, however, the results are often irreproducible. We therefore aimed to meta-analyze three eNOS widely-evaluated polymorphisms, G894T (rs1799983) in exon 7, 4b/a in intron 4, and T−786C (rs2070744) in promoter region, in association with hypertension from both English and Chinese publications, while addressing between-study heterogeneity and publication bias.

Methods

Data were analyzed using Stata software (version 11.0), and random-effects model was applied irrespective of between-study heterogeneity, which was evaluated by subgroup and meta-regression analyses. Publication bias was weighed using the Egger's test and funnel plot.

Results

There were total 19284/26003 cases/controls for G894T, and 6890/6858 for 4b/a, and 5346/6392 for T−786C polymorphism. Overall comparison of allele 894T with 894G in all study populations yielded a 16% increased risk for hypertension (odds ratio [OR] = 1.16; 95% confidence interval [95% CI]: 1.07–1.27; P = 0.001), and particularly a 32% increased risk (95% CI: 1.16–1.52; P<0.0005) in Asians and a 40% increased risk (95% CI: 1.19–1.65; P<0.0005) in Chinese. Further subgroup analyses suggested that published languages accounted for the heterogeneity for G894T polymorphism. The overall OR of allele 4a versus 4b was 1.29 (95% CI: 1.13–1.46; P<0.0005) in all study populations, and this estimate was potentiated in Asians (OR = 1.42; 95% CI: 1.16–1.72; P<0.0005). For T−786C, ethnicity-stratified analyses suggested a significantly increased risk for −786C allele (OR = 1.25; 95% CI: 1.06–1.47; P = 0.007) and −786CC genotype (OR = 1.69; 95% CI: 1.20–2.38; P = 0.003) in Whites. As an aside, the aforementioned risk estimates reached significance after Bonferroni correction. Finally, meta-regression analysis on other study-level covariates failed to provide any significance for all polymorphisms.

Conclusion

We, via a comprehensive meta-analysis, ascertained the role of eNOS G894T and 4b/a polymorphisms on hypertension in Asians, and T−786C polymorphism in Whites.

Postgraduate Symposium The MTHFR C677T polymorphism, B-vitamins and blood pressure

High blood pressure (BP) and elevated homocysteine are reported as independent risk factors for CVD and stroke in particular. The main genetic determinant of homocysteine concentrations is homozygosity (TT genotype) for the C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, typically found in approximately 10% of Western populations. The B-vitamins folate, vitamin B12and vitamin B6are the main nutritional determinants of homocysteine, with riboflavin more recently identified as a potent modulator specifically in individuals with the TT genotype. Although observational studies have reported associations between homocysteine and BP, B-vitamin intervention studies have shown little or no BP response despite decreases in homocysteine. Such studies, however, have not considered the MTHFR C677T polymorphism, which has been shown to be associated with BP. It has been shown for the first time that riboflavin is an important determinant of BP specifically in individuals with the TT genotype. Research generally suggests that 24 h ambulatory BP monitoring provides a more accurate measure of BP than casual measurements and its use in future studies may also provide important insights into the relationship between the MTHFR polymorphism and BP. Further research is also required to investigate the association between specific B-vitamins and BP in individuals with different MTHFR genotypes in order to confirm whether any genetic predisposition to hypertension is correctable by B-vitamin intervention. The present review will investigate the evidence linking the MTHFR C677T polymorphism to BP and the potential modulating role of B-vitamins.

Peroxisome proliferator-activated receptor gamma polymorphisms and coronary heart disease

Single nucleotide polymorphisms (SNPs) in the peroxisome proliferator-activated receptor γ (PPARG) gene have been associated with cardiovascular risk factors, particularly obesity and diabetes. We assessed the relationship between 4 PPARG SNPs (C-681G, C-689T, Pro12Ala, and C1431T) and coronary heart disease (CHD) in the PRIME (249 cases/494 controls, only men) and ADVANCE (1,076 cases/805 controls, men or women) studies. In PRIME, homozygote individuals for the minor allele of the PPARG C-689T, Pro12Ala, and C1431T SNPs tended to have a higher risk of CHD than homozygote individuals for the frequent allele (adjusted OR [95% CI] = 3.43 [0.96–12.27], P = .058, 3.41 [0.95–12.22], P = .060 and 5.10 [0.99–26.37], P = .050, resp.). No such association could be detected in ADVANCE. Haplotype distributions were similar in cases and control in both studies. A meta-analysis on the Pro12Ala SNP, based on our data and 11 other published association studies (6,898 CHD cases/11,287 controls), revealed that there was no evidence for a significant association under the dominant model (OR = 0.99 [0.92–1.07], P = .82). However, there was a borderline association under the recessive model (OR = 1.29 [0.99–1.67], P = .06) that became significant when considering men only (OR = 1.73 [1.20–2.48], P = .003). In conclusion, the PPARG Ala12Ala genotype might be associated with a higher CHD risk in men but further confirmation studies are needed.

Genetic variations in peroxisome proliferator-activated receptor gamma expression affect blood pressure

Metabolic syndrome, a clustering of conditions including obesity, insulin resistance, and hypertension, is a risk factor for cardiovascular morbidity and mortality. Because peroxisome proliferator-activated receptor gamma (PPARgamma) regulates adipocyte differentiation and lipid metabolism and is the molecular target of a class of insulin sensitizers, genetic variants that alter Pparg gene expression are potential contributors to the metabolic syndrome. To test this possibility, we generated mice having 182% of the normal steady-state level of PPARgamma mRNA by replacing the 3'-UTR of the natural Pparg gene with that of the beta-globin gene, thereby stabilizing the Pparg transcripts. This increase in PPARgamma mRNA level had no apparent consequences in various physiological parameters, except that the mice repeatedly showed a trend toward lower blood pressures (by about 3 mm Hg) than their WT littermates. In contrast, the opposite trend, toward increased blood pressure, was observed in mice with genetically reduced levels of PPARgamma mRNA as a consequence of insertion of an allele with an mRNA-destabilizing sequence into the endogenous 3'-UTR of the Pparg gene. By combining 12 sets of blood pressure measurements in more than 350 mutant mice having PPARgamma expression levels varying from 28% to 182% and more than 280 WT littermates, we show that a 2-fold genetic increase (or decrease) in PPARgamma expression levels decreases (or increases) blood pressure by about 2.8 mm Hg. Thus, our experiments demonstrate that quantitative variants causing decreased Pparg expression are a potential causative risk factor for essential hypertension.

PPARγ2 polymorphism and human health

The nuclear hormone receptor peroxisome proliferator activated receptor gamma (PPARγ) is an important transcription factor regulating adipocyte differentiation, lipid and glucose homeostasis, and insulin sensitivity. Numerous genetic mutations of PPARγ have been identified and these mutations positively or negatively regulate insulin sensitivity. Among these, a relatively common polymorphism of PPARγ, Pro12Ala of PPARγ2, the isoform expressed only in adipose tissue has been shown to be associated with lower body mass index, enhanced insulin sensitivity, and resistance to the risk of type 2 diabetes in human subjects carrying this mutation. Subsequent studies in different ethnic populations, however, have revealed conflicting results, suggesting a complex interaction between the PPARγ2 Pro12Ala polymorphism and environmental factors such as the ratio of dietary unsaturated fatty acids to saturated fatty acids and/or between the PPARγ2 Pro12Ala polymorphism and genetic factors such as polymorphic mutations in other genes. In addition, this polymorphic mutation in PPARγ2 is associated with other aspects of human diseases, including cancers, polycystic ovary syndrome, Alzheimer disease and aging. This review will highlight findings from recent studies.

Association of a 27-bp repeat polymorphism in intron 4 of endothelial constitutive nitric oxide synthase gene with hypertension in a Tunisian population

OBJECTIVES

Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) mediates endothelium-dependent vasodilatation and antithrombotic action. Controversial results regarding the association of eNOS gene (NOS3) polymorphisms with hypertension have been reported. In the present study, we examined a possible association between the 27-base pair (bp) repeat polymorphism in intron 4 of the NOS3 gene and hypertension in a sample of the Tunisian population.

DESIGN AND METHODS

A total of 295 Tunisian patients with hypertension and 395 healthy controls were included in the study. The NOS3 gene intron 4a4b variable number of tandem repeats polymorphism was analyzed by PCR.

RESULTS

A significant differences in genotype distribution and allele frequency was observed between patients and controls. Patients with hypertension had a frequency of 6.4% for the 4a4a genotype, 32.7% for the 4a4b genotype and 60.9% for the 4b4b genotype. The controls had a frequency of only 2.3% for the 4a4a genotype, 28.4% for the 4a4b genotype and 69.4% for the 4b4b genotype (chi(2)=11.81, p=0.003). The hypertension patient group showed a significant higher frequency of the 4a allele compared to the controls (0.23 vs. 0.16; chi(2)=8.61, p=0.003). The odds ratio of hypertension for 4a vs 4b allele frequencies was statistically significant 1.66 [1.09-2.53] at 95% CI, p=0.01 in males, whereas it was non-significant in females (1.23 [0.84-1.81], p=0.26).

CONCLUSION

The present study showed a significant and independent association between the NOS34a4b gene polymorphism (presence of 4a allele) and hypertension in the Tunisian population.

Association of the Glu298Asp polymorphism of the eNOS Gene with ischemic heart disease in Japanese diabetic subjects

We analysed the association of the Glu298Asp polymorphism of the endothelial nitric oxide synthase (eNOS) gene with ischemic heart disease (IHD) and albuminuria in 337 Japanese diabetes patients. Restriction fragment length polymorphism analysis of Glu298Asp of the eNOS gene was performed by amplification of genomic DNA isolated from whole blood followed by digestion with the restriction enzyme BanII. Individuals with IHD were identified by review of medical records and were identified based on apparent ischemic change of electrocardiography, significant stenosis of coronary artery, or a history of myocardial infarction, coronary artery bypass surgery, or catheter intervention. Albuminuria was confirmed by a positive test on at least two separate examinations. Of the 337 subjects analysed for polymorphisms of the eNOS gene, 45 with the GluAsp and five with the AspAsp genotype were combined into 1 group (GluAsp or AspAsp group). Among these 50 subjects, 16 (32%) had IHD, and among 287 subjects with the GluGlu genotype, 38 (13.2%) had IHD. The number of subjects with IHD was significantly greater in the GluAsp or AspAsp group than in the GluGlu group (P=0.0006). There was no difference in the frequency of albuminuria among the genotypes. The GluAsp or AspAsp genotype of the Glu298Asp polymorphism was significantly associated with IHD, but not albuminuria in these Japanese diabetic subjects.

Lack of association between the Pro12Ala polymorphism of the PPAR-gamma 2 gene and type 2 diabetes mellitus in the Qatari consanguineous population

Peroxisome proliferators-activated receptor gamma (PPAR gamma) is a nuclear hormone receptor that serves as a master regulator for adipocytes-specific genes contributing to adipocytes differentiation, insulin sensitivity and lipid metabolism. The substitution of proline to alanine at codon 12 of the PPAR gamma 2 gene (Pro12Ala polymorphism) is most widely studied, and the associations with diabetes, obesity, and other clinical parameters have been reported and discussed in several ethnic groups. Among native Qatar ethnicity, however, there is no report about this polymorphism. The aim of this study was to estimate the allele frequency of the Pro12Ala polymorphism of PPAR gamma 2 gene among Qatari population and investigate the association between this polymorphism and obesity or type 2 diabetes. This is a matched case-control study. It was carried out among diabetic patients and healthy subjects at the Primary Healthcare Clinics, and the survey was conducted from February 2003 to March 2006 in Qatari male and female nationals aged 35 to 60 years. The study was based on matched age, sex, and ethnicity of 400 cases (with diabetes) and 450 controls (without diabetes). Face-to-face interviews were based on a questionnaire that included variables such as age, sex, sociodemographic status, body mass index (BMI), and obesity. Their health status was assessed by medical conditions, family history, and blood pressure measurements. The allele frequency of Pro12Ala polymorphism in PPAR gamma 2 gene among Qataris is lower than that in many Caucasian ethnic groups. No association is seen between the Pro12Ala and type 2 Diabetes (0.055 vs 0.059, OR = 1.1311, P = 0.669). Nearly half of the diabetic type 2 patients (48.5%) were obese (BMI > 30) compared to nondiabetic subjects (29.8%) (P < 0.001). In this study, no association is seen between the Pro12Ala polymorphism in PPAR gamma 2 gene and the type 2 diabetes in Qatar.

Three endothelial nitric oxide (NOS3) gene polymorphisms in hypertensive and normotensive individuals: meta-analysis of 53 studies reveals evidence of publication bias

BACKGROUND

Studies on the relationship between endothelial nitric oxide (NOS3) gene variants and hypertension have been conflicting. To explore this hypothesis further, we performed a meta-analysis and re-evaluated the relationship between the three most widely studied NOS3 polymorphisms and hypertension status and blood pressure levels.

METHODS

Data on 40,413 subjects from 53 studies were combined in five distinct meta-analyses, and heterogeneity and publication bias were explored.

RESULTS

Heterogeneity was observed in all meta-analyses. By a random-effects model, carriers of the four 27-basepair repeat variable number of tandem repeats in intron 4 were associated with a 28% increase in the risk of hypertension compared with those homozygous for the 5 repeat: odds ratio (OR) 1.28, 95% confidence interval (CI) 1.11-1.47, P=0.001. In Asian individuals, Asp allele carriers displayed a similar association: OR 1.28, 95% CI 1.06-1.54, P=0.01, as well as a 2 mmHg increase in both systolic (P=0.04) and diastolic (P=0.009) blood pressure levels. Furthermore, meta-regression analysis indicated that the effect of the Glu298Asp genotype on the risk of hypertension might be dependent on total cholesterol status. No effect of the T-786C variant on hypertension was detected. There was evidence that such findings might be a result of selectively reporting/publishing positive reports.

CONCLUSION

Our results suggest that current data on the relationship between NOS3 variants and hypertension are subject not only to important heterogeneity but also to publication bias. Future research should preferentially focus on gene-environment interactions as well as haplotype analyses.

Endothelial nitric oxide synthase gene polymorphisms and cardiovascular disease: a HuGE review

This review examines the association of a subset of endothelial nitric oxide synthase gene (NOS3) polymorphisms (Glu298Asp, intron 4, and -786T>C) with cardiovascular disease. The Glu298Asp polymorphism within exon 7 is the only common nonsynonymous variant. The variants have been associated with low plasma nitric oxide concentrations and reduced vascular reactivity; difficulties in measuring those phenotypes means that their functional role remains unclear. A large meta-analysis of NOS3 polymorphisms in coronary heart disease revealed per-allele odds ratios of 1.17 (95% confidence interval: 1.07, 1.28) for Glu298Asp, 1.17 (95% confidence interval: 1.07, 1.28) for -786T>C, and 1.12 (95% confidence interval: 1.01, 1.24) for intron 4. However, there was evidence that small studies with more striking results could affect the associations of the Glu298Asp and -786T>C polymorphisms with coronary heart disease. Associations of NOS3 polymorphisms with hypertension, preeclampsia, stroke, and diabetes remain uncertain. To date, no reliable gene-gene or gene-environmental interactions have been described. Use of these variants in predictive testing is unlikely to be useful, although the population attributable fraction could be substantial if the modest associations are causal. The need for large-scale genetic association studies using tagging polymorphisms is warranted to confirm or refute a role of the NOS3 gene in coronary heart disease.

Genetic and environmental influences on body fat and blood pressure in African-American adult twins

OBJECTIVE

African Americans have a particularly high prevalence of excessive body fat and high blood pressure. Genetic and environmental influences may be implicated for both of these risk factors. We investigated the potential for common genetic and environmental influences on body fat (waist circumference (WC), body mass index (BMI)) and blood pressure measures (systolic and diastolic pressure (SBP, DBP)) among African-American male and female subjects.

RESEARCH METHODS AND PROCEDURES

Measurements were taken as part of the Carolina African-American Twin Study of Aging (CAATSA). The CAATSA sample contains 217 same-sex African-American male and female twins with average age of 47 years. This analysis included 39 monozygotic male pairs (MZ), 43 dizygotic male pairs (DZ); 63 MZ female pairs, and 72 DZ female pairs. Maximum likelihood quantitative genetic analyses were used.

RESULTS

The total genetic variance for SBP was 22% in male subjects and 40.1% in female subjects. Of this total variance, 3.1% was in common with BMI in male subjects and 6% was in common with BMI in female subjects. After controlling for the effects of BMI, WC had less than 1% of its variance in common with SBP in male and female subjects. For DBP, the total genetic variance was 16.9% in male and 38.7% in female subjects. Of this total variance 6.1% was in common with BMI in male subjects and 3.7% was in common in female subjects. Again, WC had less than 1% of its genetic variance in common with DBP in both male and female subjects. The environmental variance common among these measures was also very small. The remaining variance was primarily accounted for by genetic and environmental effects unique to each measure as well as age.

DISCUSSION

Based on the very small common genetic variance for BMI, SBP, and DBP as well as WC and the blood pressure measures, our results suggest that searching for common genes among these measures may be inconclusive.

Endothelial NO synthase gene polymorphisms and hypertension: a meta-analysis

Studies investigated the association between endothelial NO synthase gene polymorphisms and hypertension-reported contradicted or nonconclusive results. A meta-analysis of 35 genetic association studies that examined the relation between hypertension and the G894T, 4a/b, T786C, and G23T polymorphisms of the endothelial nitric oxide synthase gene was carried out. Subgroup analysis by ethnicity and potential sources of heterogeneity and bias were explored. The meta-analysis included genotype data on 7779/10 498, 2216/3222, 2491/3913, and 833/587 cases/controls for G894T, 4b/a, T786C, and G23T, respectively. For the 4b/a polymorphism, overall, the heterogeneity between studies was not significant (P=0.82), and the allele b was associated with a 15% decreased risk of hypertension relative to allele a (odds ratio: 0.85; 95% CI: 0.74 to 0.98). Overall and in whites, the recessive model for allele b produced significant results (odds ratios: 0.78; 95% CI: 0.68 to 0.90 and OR: 0.76 95% CI: 0.62 to 0.92, respectively), whereas the dominant model produced nonsignificant results. In studies involved East Asians and blacks, an association was not demonstrated. Regarding the G894T, T768C, and G23T polymorphisms, in no case (ie, overall, in whites, or in East Asians) was a statistically significant association and heterogeneity found. There was no substantial source of bias in the selected studies. In conclusion, there is evidence of association only between 4b/a polymorphism and hypertension; however, studies exploring combinations of the polymorphisms may help us better understand the genetics of hypertension.

A possible association of Pro12Ala polymorphism in peroxisome proliferator-activated receptor gamma2 gene with obesity in native Javanese in Indonesia

BACKGROUND

Peroxisome proliferators-activated receptor gamma (PPAR gamma) is a nuclear hormone receptor that serves as a master regulator of adipocytes-specific genes contributing to adipocytes differentiation, susceptibility to obesity, and insulin sensitivity. The substitution of proline to alanine at codon 12 of the PPAR gamma2 gene (Pro12Ala polymorphism) is most frequently identified and the associations with diabetes, obesity, and other clinical parameters have been reported and discussed in several ethnic groups. Among native Javanese ethnicity, however, there is no report about this polymorphism.

AIMS AND METHODS

Aims of this study were to estimate the allele frequency of the Pro12Ala polymorphism of PPAR gamma2 gene among native Javanese in Indonesia and to investigate the relationship between this polymorphism and obesity or diabetes. This study included 540 native Javanese subjects consisting of 337 diabetic patients and 203 normal glucose tolerance subjects. Both groups included totally 160 obese subjects (body mass index > or = 25 kg/m(2)). PCR-restriction fragment length polymorphism was used for the genotype determination.

RESULTS

The allele frequency of Pro12Ala polymorphism in PPAR gamma2 gene among native Javanese is lower than that in other ethnic groups. No association is seen between the Pro12Ala and diabetes (0.01 vs 0.017%, p = 0.404), a trend of the higher BMI was observed in Pro12Ala carriers in nondiabetic subjects, although this association is limited by small numbers.

CONCLUSION

In this study, no association is seen between the Pro12Ala polymorphism in PPAR gamma2 gene and diabetes; a weak association with obesity is seen.

The Pro12Ala and C-681G variants of the PPARG locus are associated with opposing growth phenotypes in young schoolchildren

AIMS/HYPOTHESIS

Peroxisome proliferator-activated receptor gamma is an important regulator of adiposity in mouse and man, and common variation in the PPARG gene has been associated with birthweight, adult obesity, insulin sensitivity and type 2 diabetes. We hypothesised that these variants may be associated with childhood obesity.

METHODS

Height and weight were recorded for 2454 prepubertal children aged between 4 and 10 years, who were then genotyped for three common variants of the PPARG locus: C-681G, Pro12Ala and C1431T.

RESULTS

No single variant of PPARG was significantly associated with height, weight or BMI. However, when modelling the variants together we detected an opposing interaction between the -681G and the Ala12 variants in height and weight, but not BMI (p=0.018, 0.013 and 0.119 respectively). The data were consistent with the Ala12 carriers being deficient in energy storage/utilisation, leading to reduced growth. In contrast, the -681G variant, which has been associated with increased adult height, was associated with accelerated growth. The two variants were in strong linkage disequilibrium. However, rare individuals bearing the isolated variants demonstrated the greatest variation from the mean, the most contrasting genotypes being associated with a variation of 7 kg in weight and 6 cm in height, standardised to 7.4-year-olds (p=0.006 and p=0.02 respectively).

CONCLUSIONS/INTERPRETATION

This study demonstrates that quantitative trait analysis of energy balance/growth and the PPARG locus is complex and requires the use of multiple genetic markers.

Endothelial nitric oxide synthase polymorphism, nitric oxide production, salt sensitivity and cardiovascular risk factors in Hispanics

Mutations in the endothelial nitric oxide synthase (eNOS) gene may be associated with abnormal nitric oxide (NO) production and cardiovascular diseases. In this study, we investigated the prevalence of two eNOS polymorphisms, the Glu298Asp variant on exon 7, and the 4a/b variable number of tandem repeats (VNTR) on intron 4, and their association with blood pressure (BP), NO production, salt sensitivity and cardiovascular risk factors in healthy Venezuelans. The prevalence of both polymorphisms in Venezuelans was comparable to that described for Caucasians, but significantly different from that known for African-Americans and Japanese. The 4a/b genotype was associated with reduced levels of NO metabolites (25% decrease), larger BP lowering in response to salt restriction (9.0 vs 4.8 mmHg, P<0.05), greater prevalence of salt sensitivity (39% in 4a/b and 27% in 4b/b; P<0.05) and with higher LDL-cholesterol levels. The Glu298T polymorphism did not affect NO production, nor it was associated with salt sensitivity. Glu298Asp polymorphism was positively associated with higher weight, triglycerides and LDL-cholesterol. Neither polymorphism was associated with changes in fasting or postload serum glucose, BP, obesity and albuminuria. In conclusion, the prevalence of eNOS polymorphisms is strongly determined by ethnic factors. The 4a/b gene polymorphism could be a genetic susceptibility factor for the BP response to salt intake and for the genetic control of NO production. The reduced NO production in subjects with the 4a/b genotype may be responsible for the increased sensitivity of their BP to salt.

Relationship of eNOS gene variants to diseases that have in common an endothelial cell dysfunction

The endothelial cell (EC) dysfunction is a common characteristic of various pathologies that include atherosclerosis, hypertension, and Fabry's disease. Aware of the role of eNO and ACE in EC dysfunction, we questioned whether polymorphism of eNOS and/or ACE gene may be a common denominator in these pathologies. Patients with CHD (108), HT (109), Fabry's disease (37) and healthy subjects (control, 141) were genotyped for the eNOSG894T by RFLP-PCR technique and for eNOS4b/a, and ACEI/D polymorphisms by PCR amplification. The results of these studies were statistically evaluated. Compared to controls, the frequency of the eNOSG894T (T allele) was higher in CHD (P=0.03) and Fabry (P=0.01), while the eNOS4b/a (a allele) in CHD (P=0.01) and HT patients (P=0.01). The proportion of the ACEI/D was similar in all subjects. In CHD patients at "low risk" of atherogenic factors, the frequency of the T and a alleles of eNOS gene was high (P=0.03 and 0.02, respectively). Carriers of the T allele of eNOSG894T were over-represented (P=0.04) in Fabry subgroup with renal failure. Compared to women, the eNOS894T alleles were more frequent (P=0.03) in men with CHD and HT, whereas ACE I/D in men (P=0.03) with HT. These findings suggest: (i) the frequency of eNOSG894T and/or eNOS4b/a is significantly associated with coronary dysfunction; (ii) eNOS4b/a confers a relatively high risk of hypertension in subjects with atherogenic risk factors; (iii) the frequency of eNOSG894T is high in Fabry hemizygotes with renal complications. Therefore, eNOS gene polymorphism represent a frequent risk factor for vascular abnormalities in CHD, HT and Fabry's disease, afflictions which have in common, the endothelial dysfunction.

Peroxisome proliferator-activated receptor-??2 Pro12Ala and endothelial nitric oxide synthase-4a/b gene polymorphisms are not associated with hypertension in diabetes mellitus type 2

OBJECTIVE AND DESIGN

The Pro12Ala and the 4a/b polymorphisms of the peroxisome proliferator-activated receptor gamma (PPARgamma) and the endothelial nitric oxide-synthase (eNOS) genes, respectively, have been associated with hypertension in some but not all studies. The purpose of this study was to investigate the association between these polymorphisms and hypertension in patients with diabetes mellitus type 2 (DM2).

METHODS

We determined, by polymerase chain reaction (PCR), the Pro12Ala PPARgamma2 and the eNOS 4a/b gene polymorphisms in a total of 395 patients with diabetes mellitus 2 (DM2) (225 men and 170 women) from the LIANCO (Lipid-Analytic-Cologne) study. Hypertension was defined as known or newly diagnosed hypertension according to current national guidelines. Associations were determined using chi-square statistics. The influence of genotype and other parameters on blood pressure was determined by analysis of variance (ANOVA) and multivariate analyses.

RESULTS

The genotype frequencies of the Pro12Ala polymorphism were 3% AlaAla, 23% ProAla and 74% ProPro and of the eNOS 4a/b polymorphism 3% a/a, 25% b/a and 72% b/b. There were 65% patients with, and 35% without hypertension. A total of 77% of the patients with hypertension were under pharmacological treatment. The mean systolic and diastolic blood pressure (SBP, DBP) was 148 +/- 22 and 84 +/- 11 mmHg in patients with, and 131 +/- 12 and 79 +/- 8 mmHg in patients without, hypertension. There was no difference in the occurrence of hypertension among ProAla and AlaAla subjects compared with ProPro subjects (P = 0.98). There was also no difference between a-allele carriers and non-carriers of the eNOS polymorphism (P = 0.42). There were no differences between men and women in the associations. Analysis of variance did neither identify an influence on systolic or diastolic blood pressure by the presence of the Ala or the a-allele of the respective genotypes nor a significant interaction of the two.

CONCLUSIONS

In DM2 the Pro12Ala and 4a/b gene polymorphisms of the PPARgamma2 and eNOS genes, respectively, are not associated with systolic or diastolic blood pressure, either in men or in women. Our results in a large cohort fail to confirm reports of recent studies suggesting an association of lower blood pressure in patients with DM2 and carriers of Pro12Ala polymorphism.

Association of the Pro12Ala and C1431T variants of PPARG and their haplotypes with susceptibility to Type 2 diabetes

AIMS/HYPOTHESIS

The Pro12Ala polymorphism of peroxisome proliferator-activated receptor (PPAR)gamma has been consistently associated with Type 2 diabetes. The rare Ala12 variant is estimated to reduce the risk of developing Type 2 diabetes by 20 percent. This variant is in linkage disequilibrium with another common variant, T1431. Both have opposing associations with body weight. We therefore examined the association of specific haplotypes marked by these two variants with susceptibility to Type 2 diabetes.

METHODS

We determined the PPARG genotype of a large Scottish cohort of Type 2 diabetic patients ( n=1997) and compared allele frequencies with a cohort of local children ( n=2444) and a middle-aged, population-based cohort from Scotland ( n=1061).

RESULTS

Frequency of the Ala12 allele was slightly lower in the Type 2 diabetic cohort than in the children [odds ratio (OR)=0.91, p=0.1]. In contrast, the Ala12 variant was under-represented in the Type 2 diabetic population when compared with similarly aged non-diabetic adults (OR=0.74, p=0.0006). When the Ala12 variant was on a haplotype not bearing the 1431T variant, it conferred greater protection (OR=0.66, p=0.003). However, when it was present in haplotypes containing the 1431T variant (70% of Ala12 carriers), this protection was absent (OR=0.99, p=0.94).

CONCLUSIONS/INTERPRETATION

We replicated the finding that the Ala12 variant of PPARgamma affords protection from Type 2 diabetes, and suggest that this protection is modulated by additional common variation at the PPARG locus.

The Methylentetrahydrofolate Reductase Gene Variant (C677T) as a Risk Factor for Essential Hypertension in Caucasians

Essential hypertension (EH) is a common, multifactorial disorder likely to be influenced by multiple genes of modest effect. The methylenetetrahydrofolate reductase (MTHFR) gene C677T mutation is functionally important, being strongly associated with reduced enzyme activity and increased plasma levels of homocysteine. Mild hyperhomocysteinemia is a known risk factor for cardiovascular disease (CVD) and hypothesised also to be involved in hypertension pathophysiology. The present study was performed to determine the prevalence of the 677T mutation in Australian Caucasian patients diagnosed with EH and to test whether the C677T variant is associated with the disorder. A case-control cohort, consisting of 250 EH patients and 250 age, sex and racially matched normotensive controls, were used for the association study. Comparison of C677T allele frequencies revealed a higher proportion of the mutant allele (T) in the EH group (40%) compared to unaffected controls (34%) (p=0.07). Furthermore, genotypic results indicated that the prevalence of the homozygous mutant genotype (T/T) in the affected group was higher than that of controls (14%:10%) (p=0.17). Interestingly, conditional logistic regression showed that the MTHFR C677T mutation conferred a mild, yet significant increase in risk of essential hypertension after adjusting for body mass index (odds ratio=1.57, 95% confidence interval: 1.04-2.37, p=0.03). These findings require further investigation in large independent samples, but suggest that essential hypertension, like CVD, may be mildly influenced by the MTHFR C677T variant.