Meta-analysis of genetic association studies on gestational diabetes mellitus

Background Several molecular epidemiological studies have analyzed the associations between genetic variants and the risk of gestational diabetes mellitus (GDM). However, all these studies suffer from inconsistent and conflicting results owing to relatively smaller sample sizes, fewer genetic variants included in the research, and limited statistical power. Hence, a coherent review and meta-analysis were carried out to provide a quantitative summary related to the associations of commonly studied SNPs with GDM risk. Methods Eligible studies were retrieved from PubMed,updated on Dec. 2019. Based on several inclusion and exclusion criteria, 71 articles with 42928 GDM patients and 77793 controls were finally considered for meta-analysis. The genotype data from 23 variants of sixteen genes were statistically analyzed using RevMan v 5.2 software. Newcastle-Ottawa Scale (NOS) was used to assess the quality of the research article. Heterogeneity among studies was tested by I2 and odds ratio with 95% confidence interval (CI) was carried out for all five genetic models. Results The overall combined odds ratio reveals that variants like MTNR1B (rs1083963, rs1387153), GCK (rs1799884), CANP10 (rs3792267), and GCKR (rs780094) are significantly associated with GDM in all genetic models while CANP10 (rs5030952), ADRB (rs4994) and FTO (rs8050136) are not significantly associated with GDM in any genetic models. Variants MTNR1B (rs1083963, rs1387153) and GCK (rs1799884) are associated with increased risk (OR>1, p<0.05) of GDM, and all these are related to insulin secretion. Other variants related to insulin secretion like TCF7L2 (rs7903146) and SLC30A8 (rs1326634) are also associated with increased risk (OR>1, p<0.05) of GDM. On the contrary, CANP10 (rs3792267) and GCKR (rs780094) are found associated with decreased risk (OR<1, p<0.05) of GDM. Other variants are significantly associated with the GDM in at least one or more genetic models. Conclusion Our study identified that most of the variants related to insulin secretions like MTNR1B (rs1083963), GCK (rs1799884), TCF7L2 (rs7903146), GCKR (rs780094), and SLC30A8 (rs1326634) are more strongly associated (p<0.005) with GDM as compared to the variants related to the insulin resistance like PPARG (rs1801282), IRS1 (rs1801278) and ADIPOQ (rs266729).

Transcription Factor 7-Like-2 (TCF7L2) rs7903146 (C/T) Polymorphism in Patients with Type 2 Diabetes Mellitus

Background Type 2 diabetes mellitus (T2DM) is a heterogeneous group of metabolic disorders characterized by the incapability of pancreatic beta cells to increase insulin secretion to compensate for insulin resistance in the peripheral tissues. T2DM is a multi-factorial disease including several environmental factors with the presence of genetic predisposition. The transcription factor 7-like-2 gene (TCF7L2) rs7903146 (C/T) polymorphism is one of the most susceptible genes to T2DM discovered to date, with contribution to the disease through the Wnt/β –catenin signaling pathway affecting pancreatic islet development, expression of several genes involved in insulin granules exocytosis and the incretin glucagon-like peptide 1 (GLP-1) gene. Aim of the Work In this study we aimed to investigate the potential association of the transcription factor 7-like-2 (TCF7L2) rs7903146 (C/T) gene polymorphism in patients with type 2 diabetes mellitus. Patients and Methods The study was a case- control study conducted on 70 T2DM patients recruited from the endocrinology clinic at Ain Shams University Hospitals, and 30 non diabetic healthy controls matched with the patients in age and sex. All subjects underwent full history taking, thorough clinical examination, routine laboratory investigations including haemoglobin A1c (HbA1c), lipid profile; total cholesterol (TC), triglycerides (TG), high density lipoprotein-cholesterol (HDL-C) and low density lipoprotein-cholesterol (LDL-C) and determination of TCF7L2 gene polymorphism by real-time quantitative polymerase chain reaction (RT-PCR). Results The minor T allele of the rs7903146(C/T) SNP was associated with high risk of development of T2DM with an OR of 1.35 (95% CI: 0.68-2.6), the heterozygous genotype (CT) with an OR 1.16 (95% CI: 0.49-2.7) and the homozygous mutant genotype (TT) with OR of 3.16 (95% CI: 0.15-6.31), however, they were statistically insignificant (p-value &gt;0.05). Conclusion Our study did not confirm the presence of significant association between the TCF7L2 rs7903146(C/T) polymorphism and T2DM, however, it pointed to the possibility of presence of high risk of development of T2DM in patients with TT genotype. Further studies with higher sample size are needed to clarify the association.

Genetic Predictors of Type 2 Diabetes in Yakuts

The goal of this study was to investigate the distribution of alleles and genotypes of the KCNJ11 rs5219, PPARG rs1801282, TCF7L2 rs7903146/rs12255372 SNPs in Yakuts with T2D, in comparison with other ethnic populations. Methods and Results: The study cohort consisted of 26 Yakut patients diagnosed with T2D (YKT2D). Genotyping of rs5219 (KCNJ11), rs1801282 (PPARG), rs7903146 and rs12255372 (TCF7L2) SNPs was performed by pyrosequencing using PyroMark Q48 Autoprep sequencer (QIAGEN). The genotyping of the studied group of Yakuts did not reveal statistically significant differences between control groups and YKT2D patients with respect to the polymorphic variants of the KCNJ11, PPARG, and TCF7L2 genes. The allele frequency analysis of the polymorphisms of the KCNJ11, PPARG, and TCF7L2 genes demonstrated a low frequency of the risk T-allele in the TCF7L2 (rs7903146, rs12255372) in Asian populations, compared to other human populations. We identified three haplotypes [CG (90.5%), TT (6.8%), and TG (2.7%)] in the YKT2D cohort. Also, we observed a strong LD between two SNPs (rs7903146 and rs12255372) of the TCF7L2 gene in the majority of groups, including YKT2D (D '= 1, LOD = 4.92), except for African populations, where a very weak LD (D '= 0.001-0.435, LOD = 0.0-0.73) was observed.

The T Allele of TCF7L2 Rs7903146 Predicts Increased Blood Glucose After Seven Days of Bed Rest in Nondiabetic Older Adults in a Secondary Analysis of a Randomized Controlled Trial

Inpatient populations are at increased risk of hyperglycemia due to factors such as medications, physical inactivity and underlying illness, which increases morbidity and mortality. Unfortunately, clinicians have limited tools available to prospectively identify those at greatest risk. We evaluated the ability of 10 common genetic variants associated with development of type 2 diabetes to predict impaired glucose metabolism. Our research model is a simulated hospital stay (7 day bed rest protocol, standardized diet, and physical inactivity) and included a cohort of healthy older adults (n = 31, 65 ± 8 years) with baseline fasting blood glucose < 100 mg/dL. Participants completed a standard 75 g oral glucose tolerance test (OGTT) at baseline and post-bed rest. In multiple regression modeling, the transcription factor 7-like 2 (TCF7L2) rs7903146 T allele predicted elevated 2-hour OGTT blood glucose (p = 0.03925). We show that the TCF7L2 rs7903146 T allele confers risk for elevated 2-hour OGTT blood glucose in nondiabetic older adults following 7 days of bed rest.

Interaction between TCF7L2 rs7903146 Genotype, HbA1c Levels, and the Periodontal Status of Dental Patients

Objective The aim of the study was to investigate the potential interaction between TCF7L2 rs7903146 genotype, which is implicated for type-2 diabetes mellitus genetic susceptibility, HbA1c levels, and the periodontal status of dental patients. Materials and Methods HbA1c levels, clinical periodontal parameters (probing depth, clinical attachment level, bleeding on probing, and plaque index), and several parameters (such as body mass index [BMI], smoking habits, education level, and age) were recorded in 150 patients who fulfilled the criteria for screening for prediabetes/diabetes of the Centers for Disease Control and Prevention. DNA was extracted and the TCF7L2 single nucleotide polymorphism (SNP) rs7903146 was genotyped in all participants. Results Thirty-one patients out of 150 tested were found with unknown hyperglycemia (20.7%). Regarding sex, education, parent with diabetes, normal BMI, smoking, age ≥45 years and prior testing for diabetes, no differences were observed between patients displaying HbA1c < 5.7 and ≥ 5.7% (Pearson’s Chi-square test, p > 0.05). Regarding periodontal parameters and differences between subgroups (HbA1c levels ≥ 5.7 and HbA1c levels < 5.7), statistically significant differences were observed for probing depth (3.20 ± 0.94 vs. 2.81 ± 0.78 mm), clinical attachment level (3.54 ± 1.20 vs. 3.18 ± 1.06 mm) and bleeding on probing (0.62 ± 0.25 vs. 0.50 ± 0.24%) with hyperglycemic patients exhibiting worse periodontal conditions (Mann–Whitney test p < 0.05). The allelic and genotype frequencies for the transcription factor 7-like 2 (TCF7L2) gene, SNPs 7903146 did not exhibit a significant difference between the HbA1c > 5.7 and HbA1c < 5.7 groups and the periodontitis and nonperiodontitis subgroups respectively (Fisher’s exact test >0.05). Statistical Analysis Patient characteristics and their association with prediabetes were tested by Pearson’s Chi-square test (asymptotic, two sided). Differences of periodontal parameters between subgroups were tested with the Mann–Whitney U-test. The associations of allele and genotype frequencies in the patient and control groups were analyzed using the Fisher’s exact test of independence.The significance level was set at the 0.05 for all tests. Conclusion A statistically significant association between TCF7L2 rs7903146 genotype and periodontal condition or HbA1c levels was not observed in contrast to statistically significant differences of clinical parameters of periodontitis in patients with hyperglycemia.

Prevalence of IGFBP3, NOS3 and TCF7L2 polymorphisms and their association with hypertension: a population-based study with Brazilian women of African descent

Objective African ancestry seems to be a risk factor for hypertension; however, few genetic studies have addressed this issue. This study aimed to investigate the prevalence of polymorphisms NOS3; rs1799983, IGFBP3; rs11977526 and TCF7L2; rs7903146 in Brazilian women of African descent and their association with hypertension. Results The prevalences of the less frequent genotypes were 26.5% TT genotype of NOS3; rs1799983, 16.7% AA genotype of IGFBP3; rs11977526, and 18.3% TT genotype of TCF7L2; rs7903146. For these conditions, the prevalence of hypertension and PR (adjusted) relatively to the ancestral genotype were, respectively: 52.0% vs 24.5% (PR = 1.54; p < 0.001), 62.0% vs 24.1% (PR = 1.59; p < 0.001), and 38.9% vs 27.9% (PR = 0.86; p = 0.166). Associations with hypertension were statistically significant, except for the TCF7L2; rs7903146 polymorphism, after adjusted analysis. Brazilian Afro-descendant women with the TT genotype for the NOS3 gene and the AA genotype for the IGFBP3 gene are more susceptible to hypertension. The understanding of underlying mechanisms involving the pathogenesis of hypertension can motivate research for the development of new therapeutic targets related to nitric oxide metabolism and the management of oxidative stress.