Relationship between genetic polymorphisms of angiotensin-converting enzyme and methylenetetrahydrofolate reductase as risk factors for type 2 diabetes in Tunisian patients

Meta-analysis of MTHFR C677T polymorphism and type 2 diabetes mellitus in MENA region

BACKGROUND AND AIMS

The association of the C677T polymorphism of the Methylenetetrahydrofolate Reductase (MTHFR) gene with susceptibility to type 2 diabetes mellitus (T2DM) has been widely debated. Therefore, our aim is to conclusively resolve this controversy in the Middle East and North Africa region population through a meta-analysis.

MATERIEL AND METHODS

We identified relevant articles by searching literature databases, such as PubMed, Web of Science, and Science Direct, to retrieve studies that examined the association between the MTHFR C677T polymorphism and the risk of developing T2DM. Using meta-analysis, we calculated the odds ratio (OR) and confidence interval (CI) values of these studies to assess the susceptibility to T2DM related to the C677T polymorphism of MTHFR gene.

RESULTS

In this meta-analysis, we included a total of 13 publications comprising 2072 T2DM patients and 2164 control subjects. The results of the meta-analysis suggested that there is a significant association between the C677T polymorphism and T2DM risk in overall comparisons for allele contrasts (T vs C): OR = 1.25, 95% CI = 1.04-1.50, p = 0.015 and homozygous (TT vs CC): OR = 1.44, 95% CI = 1.01-2.05, p = 0.038). Subgroup analysis revealed that the C677T polymorphism is associated with a risk of T2DM in Asian populations, while there is no significant association between this polymorphism and T2DM in Caucasian and African populations. Furthermore, there was no evidence of publication bias.

CONCLUSION

Our study's results suggest that the allele contrast of the C677T polymorphism of the MTHFR gene is associated with an increased risk of T2DM in the overall population, particularly among Asians.

Relationship between insertion/deletion (I/D) polymorphism of angiotensin converting enzyme (ACE) gene and susceptibility to type 2 diabetes mellitus in the Middle East and North Africa Region: A meta-analysis

BACKGROUND AND AIMS

The association between insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene and the risk of type 2 diabetes mellitus (T2DM) remains controversial. This study aimed to assess the effect of the ACE I/D gene polymorphism on T2DM in the Middle East and North Africa region (MENA region).

MATERIAL AND METHODS

Our data was extracted from PubMed, Science Direct, and the Web of Science. The predefined inclusion criteria included only the human case-control studies of English Peer-reviewed papers containing the data on genotype distributions of ACE I/D polymorphism and the T2DM risk. Review articles, meeting abstracts, editorials, animal studies, and studies not providing genotype distribution data or without sufficient data were excluded from this work. Results of this meta-analysis were expressed using odds ratios (OR) and 95% confidence intervals (CI). Indeed, the potential sources of heterogeneity and bias were examined by the Egger regression.

RESULTS

Of 2755 identified articles, 10 studies were selected, including 2710 patients with T2DM and 2504 control subjects. Overall, we found a significant increased risk of T2DM susceptibility and the D allele of ACE I/D gene polymorphism (OR = 1.97; 95% CI = 1.33-2.93, p = 0.0007), recessive (OR = 2.16; 95% CI = 1.27-3.67; p = 0.004), dominant (OR = 2.45; 95% CI = 1.54-3.91; p = 0.0001), homozygote (OR = 3.35; 95% CI = 1.78-6.29; p = 0.0001) and heterozygote comparisons (OR = 1.76; 95% CI = 1.07-2.88; p = 0.024).

CONCLUSION

Our result suggests that this polymorphism may contribute to the development of T2DM in the MENA Region. This result needs to be confirmed by future well-designed studies with larger sample sizes in diverse populations and ethnicities.

Methylenetetrahydrofolate (MTHFR), the One-Carbon Cycle, and Cardiovascular Risks

The 5-10-methylenetetrahydrofolate reductase (MTHFR) enzyme is vital for cellular homeostasis due to its key functions in the one-carbon cycle, which include methionine and folate metabolism and protein, DNA, and RNA synthesis. The enzyme is responsible for maintaining methionine and homocysteine (Hcy) balance to prevent cellular dysfunction. Polymorphisms in the MTHFR gene, especially C677T, have been associated with various diseases, including cardiovascular diseases (CVDs), cancer, inflammatory conditions, diabetes, and vascular disorders. The C677T MTHFR polymorphism is thought to be the most common cause of elevated Hcy levels, which is considered an independent risk factor for CVD. This polymorphism results in an amino acid change from alanine to valine, which prevents optimal functioning of the enzyme at temperatures above 37 °C. Many studies have been conducted to determine whether there is an association between the C677T polymorphism and increased risk for CVD. There is much evidence in favour of this association, while several studies have concluded that the polymorphism cannot be used to predict CVD development or progression. This review discusses current research regarding the C677T polymorphism and its relationship with CVD, inflammation, diabetes, and epigenetic regulation and compares the evidence provided for and against the association with CVD.

Association of angiotensin-converting enzyme insertion/deletion (ACE I/D) and angiotensinogen (AGT M235T) polymorphisms with the risk of obesity in a Tunisian population

Objective:

This study aims to determine whether genetic variants in ACE I/D and AGT M235T are associated with overweight-obesity and body mass index (BMI) in a Tunisian population.

Methods:

We designed an age- and sex-matched case-control study. The height and weight were measured and BMI was calculated. A total of 259 overweight-obese patients and 369 healthy controls were genotyped for the ACE I/D and AGT M235T genes using polymerase chain reaction and restriction fragment length polymorphism.

Results:

ACE I/D and AGT M235T genes were associated with BMI, waist circumference and overweight-obesity (p⩽0.001). In an additive model, the I and the M alleles in ACE and AGT variants, respectively, were associated with a lower BMI: –1.45 and −2.29 units, respectively. ACE I/D genotypes were associated with dyslipidemia; AGT M235T genotypes with dyslipidemia and total cholesterol.

Conclusion:

These data suggest that variations in ACE I/D and AGT M235T affect the risk of overweight-obesity, BMI and dyslipidemia, and could point to a key molecular pathway of metabolic syndrome and its related comorbidities.

Association of MTHFR C677T polymorphism and type 2 diabetes mellitus (T2DM) susceptibility

Introduction

Methylenetetrahydrofolate reductase (MTHFR) is essential in mediating folate metabolism, and thus plays an important role in diabetes and diabetic complications. MTHFR C677T (rs1801133 C>T) polymorphism has been proposed to be linked with type 2 diabetes mellitus (T2DM) susceptibility. However, the conclusions are inconsistent. Therefore, we rechecked their linkage aiming to obtain a more reliable estimation by performing an updated meta‐analysis.

Methods

We searched electronic databases PubMed, EMBASE, CNKI, and Wanfang to obtain studies updated to October 2019.

Results

After carefully screening, we finally incorporated 68 studies with 10,812 cases and 8,745 controls. The genotype frequency of C677T polymorphism was analyzed pooled to generate odds ratios (ORs) and 95% confidence intervals (CIs). Pooled results presented that MTHFR C677T polymorphism was significantly associated with T2DM under homozygous (OR = 1.64, 95% CI = 1.39–1.94), heterozygous (OR = 1.38, 95% CI = 1.20–1.59), recessive (OR = 1.41, 95% CI = 1.23–1.61), dominant (OR = 1.47, 95% CI = 1.27–1.70), and allele (OR = 1.37, 95% CI = 1.23–1.52) genetic models. Stratified analysis demonstrated that C677T genotype was associated with T2DM in Asian populations, but not Caucasian and African populations.

Conclusion

Our results indicated that MTHFR C677T polymorphism confers to T2DM, especially in Asian populations. Much more large‐scale case–control studies are needed to strengthen such conclusion in the future.

Association between MTHFR variant and diabetic neuropathy

BACKGROUND

Methylene-tetrahydrofolate reductase (MTHFR) gene variant may play an important role in the pathophysiology of diabetes and its complications due to its influence on plasma homocysteine levels and also its effect on scavenging peroxynitrite radicals. Diabetic peripheral neuropathy (DPN) is one of the most common diabetic chronic complications. The aim of this study was to investigate the relationship between diabetic neuropathy and MTHFR gene C677T and 1298A ⁄C polymorphisms.

METHOD

Patients with type 2 diabetes N=248 were enrolled in the study, consisting of patients with neuropathy (N=141) and patients without neuropathy (N=107). MTHFR C677T polymorphism was analyzed using polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP) of genomic DNA for genotyping of samples. 1298A/C polymorphism was evaluated using ARMS-PCR.

RESULT

There was a significant difference in MTHFR polymorphism between the groups with and without neuropathy.

CONCLUSION

Our results suggest that MTHFR 677 variant confer risk for diabetic neuropathy among Iranian patients with type 2 diabetes.

Pathological interactions between the endothelin-1 and the angiotensin- converting enzyme among Tunisian coronary patients

Background

The correct understanding of the biochemical and metabolic interactions between coronary risk factors contribute to the exploration of cardiovascular pathophysiology and improves therapeutic care.

The aim of this study was to explore the endothelin-1 (ET-1) concentration and the angiotensin converting enzyme (ACE) activity among Tunisian patients with coronary heart disease, and to investigate the metabolic relationships between these two markers,… and to assess the possible relationship between them and the different risk factors.

In this present study, ET-1 concentration was determined by an analytical method (High Performance Chromatography, coupled by Mass Spectrometry), ACE activity was measured by a kinetic method for patients and healthy controls. These subjects (157 patients and 142 controls) beneficed also by a biochemical exploration (lipid, apolipoproteins and glucose profiles) to quantify cardiovascular risk.

Results

A statistically significant increase of the ET-1 concentration was found among patients compared to healthy controls (15.2 ± 5.3 nM vs 7.1 ± 2.7 nM, p < 0,00001). For the ACE activity, in spite the treatment of the majority of patients (97%) with ACE inhibitors, this activity was statistically elevated in patients compared to healthy subjects (86.7 ± 25.4 IU/L vs 42.8 ± 12.1 IU/L, p < 0.00001).

Furthermore, a statistically positive correlation was identified between these two cardiac markers (r = 0.68 p < 0.00001).

Conclusion

The study of the metabolic relationship between the ET-1 and ACE among coronary patients reveals other therapeutics targets.

Angiotensin-converting enzyme insertion/deletion polymorphism association with obesity and some related disorders in Egyptian females: a case-control observational study

BACKGROUND

According to the WHO report in 2015, obesity is the fifth leading cause of death worldwide, and the prevalence of Egyptian female obesity is 37.5 %. Since obesity is highly influenced by genetics, and adipose tissue renin-angiotensin system is over-activated in obesity, the effect of angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism on obesity and related disorders was studied in several populations, because of its effect on ACE activity. Our objective was to study the association of ACE I/D polymorphism with obesity and certain related disorders, namely hypertension, insulin resistance and metabolic syndrome, in Egyptian females.

METHODS

Eighty female volunteers were recruited, blood pressure and body measurements were recorded and a fasting blood sample was obtained for the quantitation of glucose, lipid profile, insulin, leptin and identification of ACE I/D polymorphs. Subjects were grouped based on hypertension and obesity states. Comparisons of continuous parameters were made with independent sample t-test between two groups. The frequencies of ACE genotypes and alleles, and the association between gene polymorphism and metabolic parameters were assessed using chi-square or Fisher's exact test.

RESULTS

Genotype frequencies were in Hardy-Weinberg equilibrium for all groups. Genotype distribution did not differ significantly between controls and cases of all the studied disorders. Although DD carriers had apparently higher parameters of blood pressure, lipid profile and insulin resistance, only diastolic blood pressure was almost significant (p = 0.057). I-carriers were significantly less susceptible to hypertension than DD carriers having normal waist/hip ratio (p = 0.007, OR = 17.29, CI = 1.81-164.96) and normal conicity index (p = 0.024, OR = 7.00, CI = 1.36-35.93). In DD genotype carriers, a significant association was found between insulin resistance and high body mass index (p = 0.004, OR = 8.89, CI = 1.94-40.71), waist circumference (p = 0.003, OR = 9.63, CI = 2.14-43.36) and waist/height ratio (p = 0.034, OR = 6.86, CI = 1.25-37.61), although the variations in percentages between DD and I-carriers were not high enough to conclude an effect of ACE I/D on such an association.

CONCLUSIONS

In this sample of Egyptian females, ACE I/D polymorphism was not significantly associated with obesity nor with any of its related disorders studied. The I allele seemed protective against hypertension in subjects with normal, not high, waist/hip ratio and conicity index compared to DD genotype carriers.

Genetic risk of type 2 diabetes in populations of the African continent: A systematic review and meta-analyses

BACKGROUND

Type 2 diabetes (T2D) is growing faster in Africa than anywhere else, driven by the dual effects of genetic and environmental factors. We conducted a systematic review and meta-analyses of published studies on genetic markers of T2D in populations within Africa.

METHODS

Multiple databases were searched for studies of genetic variants associated with T2D in populations living in Africa. Studies reporting on the association of a genetic marker with T2D or indicators of glycaemia were included. Data were extracted on study design and characteristics, genetic determinants, effect estimates of associations with T2D.

FINDINGS

Overall, 100 polymorphisms in 57 genes have been investigated in relation with T2D in populations within Africa, in 60 studies. Almost all studies used the candidate gene approach, with >88% published during 2006-2014 and 70% (42/60) originating from Tunisia and Egypt. Polymorphisms in ACE, AGRP, eNOS, GSTP1, HSP70-2, MC4R, MTHFR, PHLPP, POL1, TCF7L2, and TNF-α gene were found to be associated with T2D, with overlapping effect on various cardiometabolic traits. The polymorphisms investigated in multiple studies mostly had consistent effects across studies, with only modest or no statistical heterogeneity. Effect sizes were modestly significant [e.g., odd ratio 1.49 (95%CI 1.33-1.66) for TCF7L2 (rs7903146)]. Underpowered genome-wide studies revealed no diabetes risk loci specific to African populations.

INTERPRETATION

Current evidence on the genetic markers of T2D in African populations mostly originate from North African countries, is overall scanty and largely insufficient to reliably inform the genetic architecture of T2D across Africa.

Meta-analytic research on the relationship between cumulative risk alleles and risk of type 2 diabetes mellitus

BACKGROUND

Our aim is to examine the dose-response association between cumulative genetic risk and actual risk of type 2 diabetes mellitus (T2DM) and the influence of adjustment for covariates on T2DM risk through a comprehensive meta-analysis of observational studies.

METHODS

Electronic literature search using EMBASE and MEDLINE (from 2003 to 2014) was conducted for cross-sectional or longitudinal studies that presented the odds ratio (OR) for T2DM in each group with categories based on the total number of risk alleles (RAs) carried (RAtotal ) using at least two single-nucleotide polymorphisms. Spline regression model was used to determine the shape of the relationship between the difference from the referent group of each study in RAtotal (ΔRAtotal ) and the natural logarithms of ORs (log OR) for T2DM.

RESULTS

Sixty-five eligible studies that included 68 267 cases among 182 603 participants were analysed. In both crude and adjusted ORs, defined by adjusting the risk for at least two confounders among age, gender and body mass index, the slope of the log OR for T2DM became less steep as the ΔRAtotal increased. In the analysis limited to 14 cross-sectional and four longitudinal studies presenting both crude and adjusted ORs, regression curves of both ORs in relation to ΔRAtotal were almost identical.

CONCLUSION

Using only single-nucleotide polymorphisms for T2DM screening was of limited value. However, when genotypic T2DM risk was considered independently from risk in relation to covariates, it was suggested that genetic profiles might have a supplementary role related to conventional T2DM risk factors in identifying individuals at high risk of T2DM. Copyright © 2015 John Wiley & Sons, Ltd.

Role of homocysteinylation of ACE in endothelial dysfunction of arteries

The direct impact of de novo synthesis of homocysteine (Hcy) and its reactive metabolites, Hcy-S-S-Hcy and Hcy thiolactone (HCTL), on vascular function has not been fully elucidated. We hypothesized that Hcy synthesized within endothelial cells affects activity of angiotensin-converting enzyme (ACE) by direct homocysteinylation of its amino- and/or sulfhydryl moieties. This covalent modification enhances ACE reactivity toward angiotensin II (ANG II)-NADPH oxidase-superoxide-dependent endothelial dysfunction. Mesenteric and coronary arteries isolated from normal rats were incubated for 3 days with or without exogenous methionine (Met, 0.1-0.3 mM), a precursor to Hcy. Incubation of arteries in Met-free media resulted in time-dependent decreases in vascular Hcy formation. By contrast, vessels incubated with Met produced Hcy in a dose-dependent manner. There was a notably greater de novo synthesis of Hcy from endothelial than from smooth muscle cells. Enhanced levels of Hcy production significantly impaired shear stress-induced dilation and release of nitric oxide, events that are associated with elevated production of vascular superoxide. Each of these processes was attenuated by ANG II type I receptor blocker or ACE and NADPH oxidase inhibitors. In addition, in vitro exposure of purified ACE to Hcy-S-S-Hcy/HCTL resulted in formation of homocysteinylated ACE and an enhanced ACE activity. The enhanced ACE activity was confirmed in isolated coronary and mesenteric arteries that had been exposed directly to Hcy-S-S-Hcy/HCTL or after Met incubation. In conclusion, vasculature-derived Hcy initiates endothelial dysfunction that, in part, may be mediated by ANG II-dependent activation of NADPH oxidase in association with homocysteinylation of ACE.

Methylenetetrahydrofolate reductase C677T polymorphism and type 2 diabetes mellitus in Chinese population: a meta-analysis of 29 case-control studies

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR), a key enzyme in folate metabolism, had significant effects on the homocysteine levels. The common functional MTHFR C677T polymorphism had been extensively researched. Several studies had evaluated the relationship between MTHFR C677T polymorphism and type 2 diabetes mellitus (T2DM), but the results were still controversial in the Chinese Han population. This meta-analysis was conducted to evaluate the relationship between MTHFR C677T polymorphism and T2DM in the Chinese Han population.

METHODS

We searched the relevant studies in multiple electronic databases, which published up to December 2013. We reviewed and extracted data from all the included studies on the relationship between MTHFR C677T polymorphism and T2DM in the Chinese Han population. The odds ratios (ORs) and their 95% confidence intervals (95%CIs) were used to evaluate the relationship. Fixed-effects and random-effects meta-analysis were used to pool ORs by the heterogeneity. Publication bias and sensitivity analysis were also examined.

RESULTS

29 studies were finally included in our meta-analysis, which contained 4656 individuals with T2DM and 2127 healthy controls. There was a significant relationship between MTHFR C677T polymorphism and T2DM under dominant (OR: 1.70, 95% CI: 1.42-2.02), recessive (OR: 1.48, 95% CI: 1.21-1.80), homozygous (OR: 1.89, 95% CI: 1.47-2.42), heterozygous (OR: 1.58, 95% CI: 1.33-1.87), and additive (OR: 1.46, 95% CI: 1.28-1.68) genetic model in a random-effects model. Subgroup analysis also reached similar results. Sensitivity analysis indicated that the overall result were dependable.

CONCLUSIONS

There was a significant relationship between MTHFR C677T polymorphism and T2DM in the Chinese Han population. The results of our meta-analysis suggested that MTHFR 677T allele might be a risk genetic factor of T2DM in the Chinese Han population.

Does the MTHFR C677T gene polymorphism indicate cardiovascular disease risk in type 2 diabetes mellitus patients?

Objective:

Diabetes mellitus is a major risk factor for cardiovascular disease (CVD). We investigated the relationship among biochemical and cardiac risk parameters with the methylenetetrahydrofolate reductase (MTHFR) C677T genotype in type 2 diabetes mellitus (T2DM) patients.

Methods:

One hundred seven T2DM subjects with severe CVD diagnosed by angiography were included consecutively in this cross-sectional study. Biochemical and clinical parameters were obtained from patients who were not positive for nephropathy and retinopathy. MTHFR C677T genotypes were analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. Normally and abnormally distributed continuous variables were analyzed using student t- and Mann-Whitney U tests. Categorical variables were analyzed using chi-square test.

Results:

In the study, 31 T2DM subjects had the CC (29.0%), 62 had the CT (57.9%), and 14 had the TT (13.1%) genotypes. There were no significant differences between subjects with wild-type (677CC) and with mutant (677CT+677TT) alleles in terms of diabetes duration, visceral fat area, total cholesterol, triglyceride, fasting plasma glucose, systolic blood pressure, diastolic blood pressure, high-sensitivity C-reactive protein, homocysteine (Hcy), and carotid intima-media thickness values.

Conclusion:

This study suggests that MTHFR gene polymorphisms can not be used as a marker for the assessment of cardiovascular risk in T2DM patients.

Association of homocysteine with type 2 diabetes: a meta-analysis implementing Mendelian randomization approach

BACKGROUND

We tested the hypothesis that elevated homocysteine (Hcy) level is causally associated with increased risk of type 2 diabetes mellitus (T2DM).

RESULTS

The meta-analysis and Mendelian randomization analysis were performed among 4011 cases and 4303 controls. The absolute pooled mean Hcy concentration in subjects with MTHFR 677TT was 5.55 μmol/L (95% CI, 1.33 to 9.77) greater than that in subjects with MTHFR 677CC in T2DM. Overall, the T allele of the MTHFR 677 C > T conferred a greater risk for T2DM [Random effect (RE) OR = 1.31(1.17-1.64), I² = 41.0%, p = 0.055]. The random effect (RE) pooled OR associated with T2DM for MTHFR 677TT relative to the 677CC was [RE OR = 1.38(1.18-1.62)]. The fixed-effect pooled OR of the association for the MTHFR 677 TT vs CT was 1.29 (95% CI, 1.09-1.51). MTHFR 677 TT showed a significantly higher risk for T2DM compared with MTHFR 677 CC + CT [Fixed effect (FE) OR = 1.32(1.14-1.54), I² = 0.0%, p = 0.686]. The absolute pooled mean Hcy concentration in individuals with T2DM was 0.94 μmol/L (95% CI, 0.40-1.48) greater than that in control subjects. The estimated causal OR associated with T2DM was 1.29 for 5 μmol/L increment in Hcy.

CONCLUSIONS

Our findings provided strong evidence on the causal association of Hcy level with the development of T2DM.

Methylenetetrahydrofolate reductase gene polymorphism and risk of type 2 diabetes mellitus

OBJECTIVE

This review aimed to comprehensively assess the literature examining a possible link between the rs1801133 polymorphism (677C → T) in the gene encoding the methylenetetrahydrofolate reductase (MTHFR) gene and risk of type 2 diabetes mellitus (DM).

RESEARCH DESIGN AND METHODS

Several research databases were systematically searched for studies examining the genotype at the rs1801133 polymorphism in healthy control individuals and individuals with type 2 DM. Genotype frequency data were examined across all studies and across subsets of studies according to ethnicity and presence of serious DM-related complications. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

RESULTS

A total of 4855 individuals with type 2 DM and 5242 healthy controls from 15 countries comprising Asian, Caucasian and African ethnicities were found to satisfy the inclusion criteria and included in the review. Genotype at the rs1801133 polymorphism was not consistently associated with either increased or reduced risk of type 2 DM; the OR across all studies was 0.91 (95%CI 0.82 to 1.00) for the C- vs. T-allele, 0.88 (0.75 to 1.03) for CC vs. CT+TT, 0.82 (0.71 to 0.95) for CC vs. TT, and 1.15 (1.03 to 1.29) for TT vs. CC+CT. Similar results were found when the meta-analysis was repeated separately for each ethnic subgroup, and for subgroups with or without serious DM-related complications.

CONCLUSIONS

There does not appear to be compelling evidence of an association between the genotype at the rs1801133 polymorphism of the MTHFR gene and risk of type 2 DM.

ACE I/D and MTHFR C677T polymorphisms are significantly associated with type 2 diabetes in Arab ethnicity: a meta-analysis

In this meta-analysis study, SNPs were investigated for their association with type 2 diabetes (T2D) in both Arab and Caucasian ethnicities. A total of 55 SNPs were analyzed, of which 11 fulfilled the selection criteria, and were used for analysis. It was found that TCF7L2 rs7903146 was significantly associated with a pooled OR of 1.155 (95%C.I.=1.059-1.259), p<0.0001 and I(2)=78.30% among the Arab population, whereas among Caucasians, the pooled OR was 1.45 (95%C.I.=1.386-1.516), p<0.0001 and I(2)=77.20%. KCNJ11 rs5219 was significantly associated in both the populations with a pooled OR of 1.176(1.092-1.268), p<0.0001 and I(2)=32.40% in Caucasians and a pooled OR of 1.28(1.111-1.475), p=0.001 among Arabs. The ACE I/D polymorphism was found to be significantly associated with a pooled OR of 1.992 (95%C.I.=1.774-2.236), p<0.0001 and I(2)=83.20% among the Arab population, whereas among Caucasians, the pooled OR was 1.078 (95%C.I.=0.993-1.17), p=0.073 and I(2)=0%. Similarly, MTHFR C677T polymorphism was also found to be significantly associated among Arabs with a pooled OR of 1.924 (95%C.I.=1.606-2.304), p<0.0001 and I(2)=27.20%, whereas among Caucasians, the pooled OR was 0.986 (95%C.I.=0.868-1.122), p=0.835 and I(2)=0%. Meanwhile PPARG-2 Pro12Ala, CDKN2A/2B rs10811661, IGF2BP2 rs4402960, HHEX rs7923837, CDKAL1 rs7754840, EXT2 rs1113132 and SLC30A8 rs13266634 were found to have no significant association with T2D among Arabs. In conclusion, it seems from this study that both Arabs and Caucasians have different SNPs associated with T2D. Moreover, this study sheds light on the profound necessity for further investigations addressing the question of the genetic components of T2D in Arabs.

Genetic combination of angiotensin-converting enzyme with methylene tetrahydrofolate reductase polymorphisms and the risk of type 2 diabetes mellitus in Bahrain

INTRODUCTION

Bahrain has a high prevalence of type 2 diabetes mellitus (T2DM). Previously, Angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism was found to be associated with T2DM in Bahrainis. The relationship between the disease progression in Bahraini T2DM population and the genetic polymorphism of methylene-tetrahydrofolate-reductase (MTHFR) C677T is still under investigation.

AIM

The current study investigated the distribution of MTHFR C677T gene polymorphism among Bahraini T2DM patients and examined the interaction between ACE I/D and MTHFR C677T polymorphisms on the risk of developing T2DM and its long-term complications.

MATERIALS AND METHODS

Polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (RFLP) were used to test for the presence of ACE I/D and MTHFR C677T polymorphisms in 171 patients with T2DM compared to 188 healthy (non-diabetic) age-matched control subjects from Bahrain.

RESULTS

The incidence of the DD genotype and D allele of the ACE gene was high among Bahraini T2DM patients. MTHFR allele and genotype frequencies did not differ between patients and controls. No significant relationship was identified between the combinations of ACE I/D and MTHFR C677T polymorphisms with T2DM.

CONCLUSIONS

The results clearly showed an association of the ACE I/D polymorphism with the progression of T2DM, but when it interacts with MTHFR polymorphism no influence was detected on the increased risk of T2DM.

Genetic variant of AMD1 is associated with obesity in urban Indian children

BACKGROUND

Hyperhomocysteinemia is regarded as a risk factor for cardiovascular diseases, diabetes and obesity. Manifestation of these chronic metabolic disorders starts in early life marked by increase in body mass index (BMI). We hypothesized that perturbations in homocysteine metabolism in early life could be a link between childhood obesity and adult metabolic disorders. Thus here we investigated association of common variants from homocysteine metabolism pathway genes with obesity in 3,168 urban Indian children.

METHODOLOGY/PRINCIPAL FINDINGS

We genotyped 90 common variants from 18 genes in 1,325 children comprising of 862 normal-weight (NW) and 463 over-weight/obese (OW/OB) children in stage 1. The top signal obtained was replicated in an independent sample set of 1843 children (1,399 NW and 444 OW/OB) in stage 2. Stage 1 association analysis revealed association between seven variants and childhood obesity at P<0.05, but association of only rs2796749 in AMD1 [OR = 1.41, P = 1.5×10(-4)] remained significant after multiple testing correction. Association of rs2796749 with childhood obesity was validated in stage 2 [OR = 1.28, P = 4.2×10(-3)] and meta-analysis [OR = 1.35, P = 1.9×10(-6)]. AMD1 variant rs2796749 was also associated with quantitative measures of adiposity and plasma leptin levels that was also replicated and corroborated in combined analysis.

CONCLUSIONS/SIGNIFICANCE

Our study provides first evidence for the association of AMD1 variant with obesity and plasma leptin levels in children. Further studies to confirm this association, its functional significance and mechanism of action need to be undertaken.

Association of the C677T polymorphism in the human methylenetetrahydrofolate reductase (MTHFR) gene with the genetic predisposition for type 2 diabetes mellitus in a Moroccan population

AIMS

Type 2 diabetes mellitus (T2DM) is a major public health problem around the world. The C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene have been reported to be associated with T2DM and its complications. This study aimed to investigate this association in the Moroccan population.

METHODS

A case-control study was performed among 282 Moroccan diabetic patients and 232 healthy controls. The MTHFR C677T and A1298C polymorphisms were genotyped by polymerase chain reaction, followed by enzymatic digestion with HinfI and MboII enzymes, respectively.

RESULTS

There was a significant association between C677T polymorphism and T2DM in both additive and dominant models. In addition, the 677T allele frequency differed significantly between the diabetic and control groups (26.06% vs. 33.20%, respectively). However, no significant association was found between A1298C polymorphism and T2DM. The frequencies of combined genotypes 677CC/1298AA and 677CT/1298AC differed significantly between the diabetic and control groups (32.62% vs. 20.61% and 9.57% vs. 17.55%, respectively).

CONCLUSIONS

These results show an evident association between the MTHFR C677T polymorphism and T2DM in Moroccan patients but no significant association with the MTHFR A1298C polymorphism.

Common variants of homocysteine metabolism pathway genes and risk of type 2 diabetes and related traits in Indians

Hyperhomocysteinemia, a risk factor for cardiovascular disorder, obesity, and type 2 diabetes, is prevalent among Indians who are at high risk of these metabolic disorders. We evaluated association of common variants of genes involved in homocysteine metabolism or its levels with type 2 diabetes, obesity, and related traits in North Indians. We genotyped 90 variants in initial phase (2.115 subjects) and replicated top signals in an independent sample set (2.085 subjects). The variant MTHFR-rs1801133 was the top signal for association with type 2 diabetes (OR = 0.78 (95%  CI = 0.67-0.92), P = 0.003) and was also associated with 2 h postload plasma glucose (P = 0.04), high-density lipoprotein cholesterol (P = 0.004), and total cholesterol (P = 0.01) in control subjects. These associations were neither replicated nor significant after meta-analysis. Studies involving a larger study population and different ethnic groups are required before ruling out the role of these important candidate genes in type 2 diabetes, obesity, and related traits.

Renin-angiotensin system polymorphisms in relation to hypertension status and obesity in a Tunisian population

Essential hypertension (HTA) is the clinical expression of a disordered interaction between the genetic, physiological, and biochemical systems that under usual conditions maintain cardiovascular homeostasis. We studied the effects of the angiotensinogen M235T, angiotensin converting enzyme insertion/deletion (ACE I/D), and angiotensin II receptor 1 (AT1R) A1166C gene polymorphisms on the risk of HTA and to evaluate the relationship between these polymorphisms and obesity. We performed AGT, ACE and AGTR genotyping in 142 hypertensive patients and 191 control subjects using PCR-RFLP methods and PCR, respectively. The three polymorphisms were significantly associated with HTA. Individuals carrying the mutated TT of AGT, DD of ACE and CC of AT1R genotypes had an 1.67 (P = 0.032), 3.09 (P < 0.001) and 3.45 (P < 0.001)-fold increased risk of HTA. After adjustment for sex, smoking, diabetes, dyslipidemia, BMI, triglycerides and DD, TT and CC genotypes, BMI was independent risk factor of HTA (OR = 3.14; P < 0.001). An association of BMI with ACE gene polymorphism (P = 0.035), whereas no association with AGT and AT1R gene polymorphisms was obtained. The proportion of hypertensives is as high as 21.8 and 13.4% in the overweight and the obese DD group. The present study implies that the genotyping for the variants of RAS gene could in the future become an important part of the clinical process of risk identification for HTA.

Genotypic interactions of renin-angiotensin system genes with diabetes type 2 in a Tunisian population

AIMS

To explore the role of genetic variants of angiotensinogen (AGT M235T), angiotensin-converting enzyme (ACE I/D), and angiotensin type 1 receptor (AT1R A1166C) as predictors of diabetes risk and to examine their combined effects on type 2 diabetes mellitus (T2DM) patients.

MAIN METHODS

One hundred and fourteen T2DM patients were compared to 175 healthy controls with similar age and sex.

KEY FINDINGS

The genotypic frequencies for all three genes alone were significantly associated with increased risk of developing diabetes. Logistic regression analysis of classic coronary risk factors and the genetic polymorphisms demonstrated that hypertension and ACE DD genotype were the most significant contributors to T2DM. For the renin-angiotensin system (RAS) genes, the risk of T2DM in individuals with one risk genotype was 1.9 (95%CI: 1.1-3.0, p=0.017) higher than those with zero risk genotype. Individuals who carried two risk genotypes had a 4.0 (95%CI 1.7-9.4, p=0.001) times higher risk of T2DM than those who did not carry any risk genotypes of the RAS genes. Most interestingly, the risk of T2DM for individuals with three risk genotypes was 26.2 (95%CI: 5.8-117.9, p<0.001) higher than those with zero risk genotype.

SIGNIFICANCE

The results of the present study imply that genotyping of renin-angiotensin system genes could become an important part of the clinical process of risk identification for T2DM in Tunisian population.

Angiotensin converting enzyme D allele is associated with an increased risk of type 2 diabetes: evidence from a meta-analysis

Associations of angiotensin converting enzyme gene (ACE) insertion/deletion (I/D) polymorphism with type 2 diabetes (T2D) have been inconsistent with both positive, null and negative results. We thereby performed a meta-analysis from all English-published reports to examine ACE I/D polymorphism in association with T2D risk. Case-control studies were identified from MEDLINE, EMBASE and Web of Science as of Dec 10, 2009. A total of 14 studies with 1985 patients with T2D and 4602 controls were finally identified. Random-effects model was applied irrespective of between-study heterogeneity. Study quality was assessed in duplicate. Compared with ACE I allele, presence of D allele conferred a significant increased risk for T2D (OR=1.33; 95% CI, 1.10-1.61; p=0.003). This trend was potentiated after comparing homozygotes of D allele with I allele with a 90% increased risk (p=0.0008). Carriers of D allele had a moderate increased risk for T2D compared with the II genotype carriers (OR=1.34; 95% CI, 1.04-1.72; p=0.02), whereas under recessive model this effect was significantly enhanced (OR=1.73; 95% CI, 1.26-2.38; p=0.0008). Subgroup analyses indicated significant association for population-based study design only, as well as among populations from Africa and Europe ancestries rather than from Asia ancestry. No publication bias was observed using the fail-safe number at the level of 0.05. Our results demonstrated that ACE D allele was significantly associated with an increased risk of T2D, and this effect appeared to be additive. Moreover, this association was more prominent for population-based studies and among Africans and Caucasians.