Association of the insertion/deletion polymorphism of the angiotensin-converting enzyme gene with type 2 diabetes in two ethnic groups of Jerba Island in Tunisia

Decoding the genetic relationship between Alzheimer's disease and type 2 diabetes: potential risk variants and future direction for North Africa

Introduction

Alzheimer's disease (AD) and Type 2 diabetes (T2D) are both age-associated diseases. Identification of shared genes could help develop early diagnosis and preventive strategies. Although genetic background plays a crucial role in these diseases, we noticed an underrepresentation tendency of North African populations in omics studies.

Materials and methods

First, we conducted a comprehensive review of genes and pathways shared between T2D and AD through PubMed. Then, the function of the identified genes and variants was investigated using annotation tools including PolyPhen2, RegulomeDB, and miRdSNP. Pathways enrichment analyses were performed with g:Profiler and EnrichmentMap. Next, we analyzed variant distributions in 16 worldwide populations using PLINK2, R, and STRUCTURE software. Finally, we performed an inter-ethnic comparison based on the minor allele frequency of T2D-AD common variants.

Results

A total of 59 eligible papers were included in our study. We found 231 variants and 363 genes shared between T2D and AD. Variant annotation revealed six single nucleotide polymorphisms (SNP) with a high pathogenic score, three SNPs with regulatory effects on the brain, and six SNPs with potential effects on miRNA-binding sites. The miRNAs affected were implicated in T2D, insulin signaling pathways, and AD. Moreover, replicated genes were significantly enriched in pathways related to plasma protein binding, positive regulation of amyloid fibril deposition, microglia activation, and cholesterol metabolism. Multidimensional screening performed based on the 363 shared genes showed that main North African populations are clustered together and are divergent from other worldwide populations. Interestingly, our results showed that 49 SNP associated with T2D and AD were present in North African populations. Among them, 11 variants located in DNM3, CFH, PPARG, ROHA, AGER, CLU, BDNF1, CST9, and PLCG1 genes display significant differences in risk allele frequencies between North African and other populations.

Conclusion

Our study highlighted the complexity and the unique molecular architecture of North African populations regarding T2D-AD shared genes. In conclusion, we emphasize the importance of T2D-AD shared genes and ethnicity-specific investigation studies for a better understanding of the link behind these diseases and to develop accurate diagnoses using personalized genetic biomarkers.

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.

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.

Implications of ACE (I/D) Gene Variants to the Genetic Susceptibility of Coronary Artery Disease in Asian Indians

Angiotensin-1-converting enzyme (ACE) gene has established substantial attention in the recent years as a candidate gene for hypertension, cardiovascular diseases and type 2 diabetes. The aim of the present study was to investigate the association of ACE (I/D) polymorphism with coronary artery disease (CAD) in a north Indian population. A total of 662 subjects (330 CAD patients and 332 healthy controls) were examined for association of ACE gene (I/D) polymorphism and environmental risk factors. The mean age of the CAD patients and control subjects was 60.53 ± 8.6 years and 56.55 ± 7.7 years, respectively (p = 0.000). Anthropometric and demographic data showed BMI values significantly higher among CAD patients and control subjects (26.98 ± 4.9 vs 24.04 ± 4.7, p = 0.000). We observed pronounced central obesity in both CAD patients and controls, even at the lowest BMI values (<23 kg/m²). Dyslipidemia was highly prevalent in CAD patients compared to control subjects. Genotypic data showed significantly higher frequency of DD genotype in CAD patients than that of control subjects (40 vs 28.3 %). No significant difference was observed in the distribution of ID genotypes between CAD patients and control subjects. Logistic regression analysis of data demonstrate that DD genotype was associated with 1.8 fold increased risk of development of CAD in Asian Indians (OR 1.8; 95 % CI 1.22-2.66; p = 0.003). The frequency of D allele was significantly higher in CAD patients (p = 0.001). No significant difference was observed in the clinical and biochemical characteristics of CAD patients and controls when the data was stratified according to the genotypes of ACE gene. In conclusion, DD genotype of ACE gene may be associated with increased risk of CAD in Asian Indian population.

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.

Association of Angiotensin Converting Enzyme Insertion-Deletion Polymorphism with Hypertension in Emiratis with Type 2 Diabetes Mellitus and Its Interaction with Obesity Status

The association of Angiotensin Converting Enzyme (ACE) insertion-deletion (I/D) polymorphism with Type 2 Diabetes Mellitus (T2DM) and hypertension has been extensively studied throughout various ethnic populations but largely with inconsistent findings. We investigated these associations in Emirati population and their interaction with obesity status. Saliva samples were collected from a total of 564 Emiratis (277 T2DM and 297 healthy). DNA was extracted and the samples were genotyped for ACE I/D polymorphism by a PCR based method followed by gel electrophoresis. Upon evaluation of the ACE I/D polymorphism amongst all T2DM, hypertensive patients, and respective controls regardless of obesity status, ACE DD genotype was not found to be associated with either T2DM [odds ratio (OR) = 1.34, p = 0.086] or hypertension [odd ratio (OR) = 1.02, p = 0.93]. When the genetic variants amongst the nonobese and obese population were analyzed separately, the risk genotype ACE DD conferred significantly increased risk of hypertension in nonobese population [odds ratio (OR) = 1.80, p = 0.02] but was found to be protective against the hypertension in the obese group ((OR) = 0.54, p = 0.01). However, there was no effect of obesity status on the association of ACE genotypes with T2DM. The risk of hypertension associated with ACE DD is modulated by obesity status and hence future genetic association studies should take obesity into account for the interpretation of data. We also confirmed that ACE I/D polymorphism is not associated with T2DM risk in Emirati population.

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.

The relationship of ACE and CETP gene polymorphisms with cardiovascular disease in a cohort of Asian Indian patients with and those without type 2 diabetes

INTRODUCTION

Hypertension and dyslipidemia have been associated with cardiovascular disease (CVD). We investigated the association of candidate gene polymorphisms in angiotensin-converting enzyme (ACE) and cholesterol ester transfer protein (CETP) genes in a cohort of Asian Indian patients with and those without type 2 diabetes.

METHODS

PCR-based genotyping of insertion/deletion (I/D) polymorphism of ACE (rs4646994) and -629C>A of CETP (rs1800775) was carried out in 520 individuals, of whom 160 had CVD+type 2 diabetes mellitus (T2DM), 90 were CVD patients without T2DM, 150 had T2DM with no cardiovascular complications, and 120 were age- and sex-matched healthy controls.

RESULTS

With respect to the ACE gene I/D polymorphism, there was a higher percentage of D/D genotype in CVD+T2DM patients, but it was not statistically significant, while the CETP -629A allele was significantly associated with CVD+T2DM patients (P=.000007; odds ratio=0.46; 95% confidence interval=0.32-0.65) as compared with the normal controls and not with CVD alone. Additive interactions between the AA+I/I genotypes, AC+I/D genotypes, and AC+D/D were identified between the patients and the controls with P values of .0052, .0009, and .0078, respectively.

CONCLUSIONS

Our study suggests that candidate gene polymorphism -629C>A of CETP may serve as a susceptibility biomarker for CVD in T2DM patients. Analyzing the combined effect of both ACE and CETP genotypes would enhance the sensitivity and specificity of CVD risk estimation in the T2DM patients in our population.

Pharmacogenetic association of hypertension candidate genes with fasting glucose in the GenHAT Study

BACKGROUND

Several clinical studies report increased risk of diabetes mellitus with pharmacologic treatment for hypertension (HTN). HTN genes may modify glycemic response to antihypertensive treatment.

METHOD

The current study examined the association of 24 single nucleotide polymorphisms (SNPs) in 11 HTN candidate genes with fasting glucose measured at 2, 4, and 6 years after treatment initiation. The study sample included participants free of diabetes at baseline in the Genetics of Hypertension Associated Treatment (GenHAT) study (N = 9309). GenHAT participants were randomized to receive treatment with a diuretic (chlorthalidone), calcium channel blocker (amlodipine), or angiotensin-converting enzyme (ACE) inhibitor (lisinopril). Mixed models for repeated measures were employed to test for gene and pharmacogenetic associations with fasting glucose during follow-up.

RESULTS

Fasting glucose at year 2 increased on average 6.8, 4.8 and 3.0 mg/dl from baseline in the chlorthalidone, amlodipine and lisinopril groups, respectively. Carrying the I allele (rs1799752) of the ACE I/D polymorphism was associated with lower fasting glucose levels (P = 0.02). Additionally, an ACE promoter polymorphism (-262, rs4291) was associated with lower fasting glucose for the model AA/AT vs. TT, which remained significant after correction for multiple testing (P = 0.001). Finally, a SNP in the α-subunit of the amiloride-sensitive epithelial sodium channel (SCNN1A, rs2228576) modified the association of amlodipine vs. chlorthalidone treatment with fasting glucose (P < 0.001).

CONCLUSION

Further examination of these genes and their relationships with cardiometabolic disease could foster development of pharmacogenetic guidelines aimed to prevent increases in fasting glucose during antihypertensive treatment.

Renin angiotensin system polymorphisms in patients with metabolic syndrome (MetS)

BACKGROUND

The genes associated with hypertension could be genetic risk factors for metabolic syndrome (MetS).

AIM

To determine the frequency of M235T and T174M-AGT, I/D-ACE and A1166C-AGTR1 in hypertensive patients with MetS and to evaluate the relationship between these polymorphisms and central obesity and dyslipidemia, respectively.

MATERIALS AND METHODS

We performed AGT, AGTR1 and ACE genotyping in 56 hypertensive women (24 with MetS) and 71 normotensive women using PCR-RFLP methods and PCR, respectively.

RESULTS

Hypertensive patients carrying the mutated TT235, MM174 and DD genotypes had an 1.53 (p=0.56), 1.78 (p=0.52) and 1.28 (p=0.78)-fold increased risk to develop MetS. Hypertensive carriers of both mutated TT235 and MM174 or TT235 and D/D or TT235 and CC+AC genotypes had an 8.15 (p=0.04), 4.83 (p=0.04) and 10.53 (p=0.05)-fold increased risk to develop MetS. Hypertensive patients with MetS and TT, D/D or CC genotypes had higher body mass index compared to hypertensive patients without MetS (p</=0.05 for all the genotypes). Hypertensive patients with MetS and TT235, MM174, D/D or CC1166 genotypes had higher triglyceride levels, lower HDL-cholesterol levels and higher waist circumference compared to hypertensive patients without MetS (p</=0.05, except for the association between CC1166 and HDL-cholesterol level).

CONCLUSIONS

The effect of the T174M, I/D and A1166C polymorphisms on MetS may depend on the M235T polymorphism. Among hypertensive subjects with MetS, the presence of TT235, MM174, DD and CC1166 genotypes could be a risk factor for central obesity and dyslipidemia.

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.