Ethnic difference in patients with type 2 diabetes mellitus in inter-East Asian populations: a systematic review and meta-analysis focusing on gene polymorphism

The Uyghur population and genetic susceptibility to type 2 diabetes: potential role for variants in CAPN10, APM1 and FUT6 genes

Genome‐wide association studies have successfully identified over 70 loci associated with the risk of type 2 diabetes mellitus (T2DM) in multiple populations of European ancestry. However, the risk attributable to an individual variant is modest and does not yet provide convincing evidence for clinical utility. Association between these established genetic variants and T2DM in general populations is hitherto understudied in the isolated populations, such as the Uyghurs, resident in Hetian, far southern Xinjiang Uyghur Autonomous Region, China. In this case–control study, we genotyped 13 single‐nucleotide polymorphisms (SNPs) at 10 genes associated with diabetes in 130 cases with T2DM and 135 healthy controls of Uyghur, a Chinese minority ethnic group. Three of the 13 SNPs demonstrated significant association with T2DM in the Uyghur population. There were significant differences between the T2DM patients and controls in the risk allele distributions of rs3792267 (CAPN10) (P = 0.002), rs1501299 (APM1) (P = 0.017), and rs3760776 (FUT6) (P = 0.031). Allelic carriers of rs3792267‐A, rs1501299‐T, and rs3760776‐T had a 2.24‐fold [OR (95% CI): 1.35–3.71], 0.59‐fold [OR (95% CI): 0.39–0.91], 0.57‐fold [OR (95% CI): 0.34–0.95] increased risk for T2DM respectively. We further confirmed that the cumulative risk allelic scores calculated from the 13 susceptibility loci for T2DM differed significantly between the T2DM patients and controls (P = 0.001), and the effect of obesity/overweight on T2DM was only observed in the subjects with a combined risk allelic score under a value of 17. This study observed that the SNPs rs3792267 in CAPN10, rs1501299 in APM1, and rs3760776 in FUT6 might serve as potential susceptible biomarkers for T2DM in Uyghurs. The cumulative risk allelic scores of multiple loci with modest individual effects are also significant risk factors in Uyghurs for T2DM, particularly among non‐obese individuals. This is the first investigation having observed/found genetic variations on genetic loci functionally linked with glycosylation associated with the risk of T2DM in a Uyghur population.

The TCF7L2 rs7903146 (C/T) polymorphism is associated with risk to type 2 diabetes mellitus in Southern-Brazil

OBJECTIVE

The aim of this study was to investigate the association between the rs7903146 (C/T) polymorphism in the TCF7L2 gene and type 2 diabetes mellitus, in a Southern-Brazilian population.

MATERIALS AND METHODS

The TCF7L2 rs7903146 polymorphism was genotyped in 953 type 2 diabetic patients and 535 non-diabetic subjects. All subjects were white. The polymorphism was genotyped by Real-Time PCR using TaqMan MGB probes (Life Technologies). Odds ratios (OR) and 95% confidence intervals (CI) were calculated for additive, recessive and dominant inheritance models.

RESULTS

Genotype and allele frequencies of the rs7903146 polymorphism differed significantly between type 2 diabetic patients and non-diabetic subjects (P = 0.001 and P = 0.0001, respectively). The frequency of the minor allele was 38% in type 2 diabetes group and 31% in non-diabetic subjects, and this allele was significantly associated with type 2 diabetes risk (OR = 1.42, 95% CI 1.15 - 1.76 for the dominant model of inheritance). Moreover, the T/T genotype was associated with a higher risk for type 2 diabetes (OR = 1.83, 95% CI 1.3-2.5) than the presence of only one copy of the T allele (OR = 1.31, 95% CI 1.1-1.6). Both results were adjusted for age and gender.

CONCLUSIONS

Our results confirm the association between the TCF7L2 rs7903146 polymorphism and increase risk for type 2 diabetes in Southern-Brazil.

SAA1 genetic polymorphisms are associated with plasma glucose concentration in non-diabetic subjects

BACKGROUND

Serum amyloid A (SAA) was reported to be associated with insulin resistance and type-2 diabetes. The present study aimed to investigate the association of SAA genetic polymorphisms with plasma glucose levels in non-diabetic subjects.

METHODS

All participants (n=1220) were selected from subjects participating in the Cardiovascular Risk Survey (CRS) study. Five single-nucleotide polymorphisms (SNPs) (rs2229338, rs12218, rs4638289, rs7131332 and rs11603089) of SAA gene were genotyped using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analysis.

RESULTS

In the present study, we found rs2229338, rs4638289 and rs12218 were significantly associated with plasma glucose levels in a dominate model, recessive model or additive model before and after multivariate adjustment (all p<0.05). These associations were not found in rs7131332 and rs11603089 before and after adjustment of key co-variants.

CONCLUSIONS

The genetic polymorphisms of SAA1 were associated with plasma glucose levels in non-diabetic subjects.

Evidence for association of the E23K variant of KCNJ11 gene with type 2 diabetes in Tunisian population: population-based study and meta-analysis

Aims. Genetic association studies have reported the E23K variant of KCNJ11 gene to be associated with Type 2 diabetes. In Arab populations, only four studies have investigated the role of this variant. We aimed to replicate and validate the association between the E23K variant and Type 2 diabetes in Tunisian and Arab populations. Methods. We have performed a case-control association study including 250 Tunisian patients with Type 2 diabetes and 267 controls. Allelic association has also been evaluated by 2 meta-analyses including all population-based studies among Tunisians and Arabs (2 and 5 populations, resp.). Results. A significant association between the E23K variant and Type 2 diabetes was found (OR = 1.6, 95% CI = 1.14–2.27, and P = 0.007). Furthermore, our meta-analysis has confirmed the significant role of the E23K variant in susceptibility of Type 2 diabetes in Tunisian and Arab populations (OR = 1.29, 95% CI = 1.15–1.46, and P < 10⁻³ and OR = 1.33, 95% CI = 1.13–1.56, and P = 0.001, resp.). Conclusion. Both case-control and meta-analyses results revealed the significant association between the E23K variant of KCNJ11 and Type 2 diabetes among Tunisians and Arabs.

Role of calpain-10 in the development of diabetes mellitus and its complications

Calpain activity has been implicated in several cellular processes such as cell signaling, apoptosis, exocytosis, mitochondrial metabolism and cytoskeletal remodeling. Evidence has indicated that the impairment of calpain expression and the activity of different calpain family members are involved in diverse pathologies. Calpain-10 has been implicated in the development of type 2 diabetes, and polymorphisms in the CAPN10 gene have been associated with an increased risk of developing this disease. The present work focused on the molecular biology of calpain-10, supporting its key participation in glucose metabolism. Current knowledge regarding the role of calpain-10 in the development of type 2 diabetes mellitus and diabetes-related diseases is additionally reviewed.

The new perspectives on genetic studies of type 2 diabetes and thyroid diseases

Recently, genome-wide association studies (GWAS) have led to the discovery of hundreds of susceptibility loci that are associated with complex metabolic diseases, such as type 2 diabetes and hyperthyroidism. The majority of the susceptibility loci are common across different races or populations; while some of them show ethnicity-specific distribution. Though the abundant novel susceptibility loci identified by GWAS have provided insight into biology through the discovery of new genes or pathways that were previously not known, most of them are in introns and the associated variants cumulatively explain only a small fraction of total heritability. Here we reviewed the genetic studies on the metabolic disorders, mainly type 2 diabetes and hyperthyroidism, including candidate genes-based findings and more recently the GWAS discovery; we also included the clinical relevance of these novel loci and the gene-environmental interactions. Finally, we discussed the future direction about the genetic study on the exploring of the pathogenesis of the metabolic diseases.

Meta-analysis of associations between TCF7L2 polymorphisms and risk of type 2 diabetes mellitus in the Chinese population

Background

Associations between transcription factor 7-like 2 (TCF7L2) polymorphisms and type 2 diabetes mellitus (T2DM) have been evaluated extensively in multiple ethnic groups. TCF7L2 has emerged as the strongest T2DM susceptibility gene in Europeans, but the findings have been inconsistent in the Chinese population. The purpose of this meta-analysis was to evaluate the associations between TCF7L2 single nucleotide polymorphisms (SNPs) and T2DM risk in the Chinese population.

Methods

We performed searches in the PubMed, EMBASE, Cochrane, and Chinese databases (CNKI, CQVIP and Wanfang databases) for literature published from January 2007 to February 2012. We reviewed all relevant articles on TCF7L2 polymorphisms and susceptibility to T2DM in the Chinese population written in English and Chinese. Two reviewers extracted data independently using a standardized protocol, and any discrepancies were adjudicated by a third reviewer. Fixed-effects and random-effects meta-analyses were performed to pool the odds ratios (ORs). Publication bias and heterogeneity were examined.

Results

A total of 21 articles were confirmed to be eligible for and included in this meta-analysis: 7 (with 3942 cases and 3502 controls) concerning rs11196218 (IVS−/+4G>A), 8 (with 3377 cases and 2975 controls) concerning rs290487 (IVS3−/+C>T), and 14 (with 7902 cases and 7436 controls) concerning rs7903146 (IVS3−/+C>T). Overall, the results showed a significant association between rs7903146 and T2DM risk. The pooled ORs were 1.54 for the comparison of T and C alleles (95% CI [confidence interval]: 1.37–1.74, p = 1.47 × 10^-12, I² = 25.20%) and 1.56 for TC heterozygotes and CC homozygotes (95% CI : 1.38–1.76, p = 8.25 × 10^-9, I² = 21.00%). The rs11196218(IVS4G>A) and rs290487 (IVS3C>T) SNPs were not associated with T2DM risk.

Conclusions

The rs7903146 SNP of the TCF7L2 gene is associated with increased susceptibility to T2DM in the Chinese population as a whole as well as northern Chinese and southern Chinese as subgroups.

Type 2 diabetes in Asians: prevalence, risk factors, and effectiveness of behavioral intervention at individual and population levels

This review summarizes the current data on diabetes risk factors, prevalence, and prevention efforts in Asia and Asian migrant populations. Studies indicate that type 2 diabetes mellitus is a large and growing threat to public health in Asian populations. Furthermore, Asian subgroups (e.g., South Asians/Asian Indians, Chinese) have unique risk factor profiles for developing diabetes, which differ from other populations and between Asian ethnic groups. Lifestyle intervention programs are effective in preventing diabetes in Asians, as with other ethnicities. The strength of these findings is lessened by the lack of systematically collected data using objective measurements. Large epidemiologic studies of diabetes prevalence and risk factor profiles and translational trials identifying sustainable and culturally acceptable lifestyle programs for Asian subgroups are needed.

The importance of global studies of the genetics of type 2 diabetes

Genome wide association analyses have revealed large numbers of common variants influencing predisposition to type 2 diabetes and related phenotypes. These studies have predominantly featured European populations, but are now being extended to samples from a wider range of ethnic groups. The transethnic analysis of association data is already providing insights into the genetic, molecular and biological causes of diabetes, and the relevance of such studies will increase as human discovery genetics increasingly moves towards sequencing-based approaches and a focus on low frequency and rare variants.