Genetic advances of type 2 diabetes in Chinese populations

Low-Frequency Genetic Variant in the Hepatic Glucokinase Gene Is Associated With Type 2 Diabetes and Insulin Resistance in Chinese Population

Glucokinase (GCK) regulates insulin secretion and hepatic glucose metabolism, and its inactivating variants could cause diabetes. We aimed to evaluate the association of a low-frequency variant of GCK (rs13306393) with type 2 diabetes (T2D), prediabetes, or both (impaired glucose regulation [IGR]) in a Chinese population. An association study was first conducted in a random cluster sampling population (sample 1: 537 T2D, 768 prediabetes, and 1,912 control), and then another independent population (sample 2: 3,896 T2D, 2,301 prediabetes, and 868 control) was used to confirm the findings in sample 1. The A allele of rs13306393 was associated with T2D (odds ratio 3.08 [95% CI 1.77-5.36], P = 0.00007) in sample 1; rs13306393 was also associated with prediabetes (1.67 [1.05-2.65], P = 0.03) in sample 2. In a pooled analysis of the two samples, the A allele increased the risk of T2D (1.57 [1.15-2.15], P = 0.005), prediabetes (1.83 [1.33-2.54], P = 0.0003) or IGR (1.68 [1.26-2.25], P = 0.0004), insulin resistance estimated by HOMA (β = 0.043, P = 0.001), HbA_1c (β = 0.029, P = 0.029), and urinary albumin excretion (β = 0.033, P = 0.025), irrespective of age, sex, and BMI. Thus, the Chinese-specific low-frequency variant increased the risk of T2D through reducing insulin sensitivity rather than islet β-cell function, which should be considered in the clinical use of GCK activators in the future.

Prevalence of hypertension, diabetes, and dyslipidemia, and their additive effects on myocardial infarction and stroke: a cross-sectional study in Nanjing, China

BACKGROUND

This study aimed to investigate the prevalence and risk factors for hypertension, diabetes, and dyslipidemia, and to evaluate their additive effects on myocardial infarction (MI) and stroke in Nanjing in East China.

METHODS

A multistage, stratified random cluster sampling method was used to select representative participants. All eligible participants completed questionnaires, physical measurements, and blood tests. Multivariable and univariable logistic regression analyses were used to identify associated risk factors and evaluate additive effects on cardiovascular events, respectively.

RESULTS

Hypertension was the most prevalent chronic disease among 11,036 participants enrolled (18.5%), followed by dyslipidemia (8.3%) and diabetes (6.0%). The prevalence of hypertension was higher in men than in women while no sex-related difference was observed in the prevalence of diabetes and dyslipidemia. Older age and higher body mass index were risk factors for all three diseases. Sex, central obesity, smoking, number of family members, salt intake, and family history of hypertension were associated with hypertension; central obesity, smoking, alcohol assumption, and family history of diabetes correlated with diabetes; and female sex, higher education, and alcohol assumption were risk factors for dyslipidemia. Hypertension complicated with dyslipidemia conferred more risk of MI and stroke than independent effects. Diabetes also contributed to risk based on hypertension or dyslipidemia.

CONCLUSIONS

The burden of hypertension and diabetes has stopped increasing. However, total cholesterol (TC) concentration in the population has not been well controlled. A more comprehensive approach to managing dyslipidemia, hypertension, and diabetes needs to be developed, especially for individuals with multiple cardiovascular risk factors.

Association and in silico studies of ENPP1 gene variants with type 2 diabetes mellitus in a Northern Iranian population

In the current study, a sample population of Northern Iranians was selected to investigate the association of K121Q, rs1799774, rs7754561, and rs997509 ENPP1 gene variants and their haplotypes with T2DM. Genomic DNAs of 978 samples were extracted by Salting Out standard technique and then genotyped by the TaqMan assay. The results show significant differences between study groups for K121Q (p = 0.0004) under a Dominant and rs7754561 (p = 0.002) under a co-dominant hereditary model. Based on allele frequency, there was a significant difference between two study groups at K121Q and rs7754561 variants (p = 0.010 and p = 0.01, respectively). There was no evidence for an association between ENPP1 haplotypes and overall risk of T2DM. Genotype-phenotype sub-analyses showed no significant relationship of four studied polymorphisms with age, gender, FBS, and systolic and diastolic blood pressures. Homology modeling and molecular docking of ENPP1 in K173 and Q173 models with ATP, AMP, and 2'3'-cGAMP as ligands revealed that all ligands had a more binding affinity to Lys173 protein model, and 2'3'-cGAMP had a higher affinity to both ENPP1 protein models compared to ATP and AMP. These findings suggest that ENPP1 gene variants may have a potential impact on the occurrence of T2DM in Northern Iranians.

A variant of GRK5 is associated with the therapeutic efficacy of repaglinide in Chinese Han patients with type 2 diabetes mellitus

Post-Market Research We aimed to investigate the impact of G protein-coupled receptor kinase 5 (GRK5) rs10886471 polymorphism on repaglinide efficacy in Chinese patients with type 2 diabetes mellitus (T2DM). A total of 300 T2DM patients and 210 healthy controls were genotyped for GRK5 rs10886471 on a three-dimensional polyacrylamide gel-based DNA microarray. Eighty-five patients with the same genotypes of cytochrome P450 (CYP) 2C8*3 139Arg and organic anion-transporting polypeptide 1B1 (OATP1B1) 521TT were randomly selected to orally take repaglinide for eight consecutive weeks. Then, the biochemical indicators and pharmacodynamic parameters were measured before and after repaglinide treatment. The T allelic frequency of GRK5 rs10886471 was higher in T2DM patients than in healthy subjects (p < .01). T2DM patients with genotypes CC and CT at GRK5 rs10886471 had a significant reduction in terms of fasting plasma glucose (FPG) compared with those with genotype TT (p < .01). In addition, the carriers of genotypes CC and CT at GRK5 rs10886471 had higher differential values of postprandial serum insulin (PINS) compared with genotype TT carriers (p < .05). These findings suggest that GRK5 rs10886471 polymorphism may influence the therapeutic efficacy of repaglinide in Chinese Han T2DM patients.

CRP-level-associated polymorphism rs1205 within the CRP gene is associated with 2-hour glucose level: The SAPPHIRe study

C-reactive protein (CRP) encoded by CRP gene is a reflection of systemic inflammation. Many studies associated CRP level with diabetes and glucose levels, but the association of CRP gene with these traits is unclear. We conducted a cross-sectional study consisting of 945 siblings from 330 families collected by the Stanford Asian Pacific Program in Hypertension and Insulin Resistance (SAPPHIRe) to investigate associations between CRP polymorphisms, circulating CRP, diabetes, and glucose levels. Five single-nucleotide polymorphisms were analyzed: rs3093059, rs2794521, rs1417938, rs1800947, and rs1205. The generalized estimating equation approach was used to deal with correlated data within families. CRP level was positively correlated with diabetes prevalence and levels of fasting and 2-hour glucose (each P < 0.008). Alleles C at rs3093059 and G at rs1205 were associated with elevated CRP level (each P < 1.2 × 10⁻⁶). Allele C at rs3093059 was associated with fasting glucose (β = 0.20, P = 0.045) and G at rs1205 was associated with 2-hour glucose (β = 0.46, P = 0.00090) post oral glucose tolerance test, but only the latter passed Bonferroni correction. No polymorphism was associated with diabetes. Since 2-hour glucose is an indicator of glucose tolerance, this study indicated CRP gene is associated with glucose intolerance.

Common variants of HNF1A gene are associated with diabetic retinopathy and poor glycemic control in normal-weight Japanese subjects with type 2 diabetes mellitus

AIM

This study investigated the associations between the common hepatocyte nuclear factor-1A (HNF1A) variants and the risk of diabetic retinopathy (DR) in relation to the glycemic control and weight status.

METHODS

A retrospective longitudinal analysis was conducted among 354 Japanese patients with type 2 diabetes mellitus (T2DM) (mean follow-up duration: 5.8±2.5 years). The multivariable-adjusted hazard ratio (HR) for the cumulative incidence of DR was calculated using a Cox proportional hazard model. During the observation period, the longitudinal associations of the HNF1A diplotypes with the risk of DR and the clinical parameters were also analyzed using the generalized estimating equations approach.

RESULTS

The combination of risk variants, i.e., rs1169288-C, rs1183910-A and rs2464196-A, was defined as the H1 haplotype. The incidence of DR was higher in the H1/H1 diplotype cases than in the others (HR 2.75 vs. non-H1/non-H1; p=0.02). Only in normal-weight subjects, the risks of DR and poor glycemic control were higher in the H1/H1 diplotype cases than in the others [odds ratio 4.08 vs. non-H1/non-H1, p=0.02; odds ratio 3.03, p=0.01; respectively].

CONCLUSIONS

This study demonstrated that the common HNF1A diplotype of three risk variants may be an independent risk factor for the development of DR resulting from poor glycemic control in normal-weight patients with T2DM. These results need to be replicated in larger and more varied study populations.

Association of HaeIII single nucleotide polymorphisms in the SLC2A1 gene with risk of diabetic nephropathy; evidence from Kurdish patients with type 2 diabetes mellitus

AIMS

Given the growing rate of patients with type 2 diabetes mellitus, uncovering the effects of gene polymorphism on diabetes pathogenesis has attracted a lot of attention. Because glucose transporter 1 is involved in glucose uptake, the polymorphism of this gene may be an important risk factor in type 2 diabetes mellitus or in the progression of diabetes complications such as diabetic nephropathy. As far as the authors are concerned, this study is the first one aiming at evaluating the probable effects of solute carrier family 2 facilitated glucose transporter member 1 (SLC2A1) HaeIII polymorphism on clinical and laboratory outcomes of Kurdish patients with type 2 diabetes mellitus.

METHODS

This study was conducted involving 126 diabetic nephropathy patients and 150 diabetic patients without renal involvement. Serum levels of Cystatin C, fasting blood glucose, creatinine and urinary albumin; levels of glycated hemoglobin and estimated glomerular filtration rate were measured. Moreover, the Hae III polymorphism of SLC2A1 gene was determined by PCR-restriction fragment length polymorphism (RFLP).

RESULTS

The rate of CC genotype was higher (37%) in patients with diabetic nephropathy compared with controls. There were a significant correlation between the CC genotype and risk of diabetic nephropathy. There were significant correlations between genotypes, serum Cystatin C and estimated glomerular filtration rate in patients with diabetic nephropathy.

CONCLUSIONS

The results demonstrated the high frequency of C allele of SLC2A1 HaeIII in Kurdish patients with diabetic nephropathy. It was also found that this polymorphism is a significant risk factor for diabetic nephropathy. The effect of this polymorphism on clinical and laboratory characteristics of diabetic nephropathy patients was significant.

Glucose Tolerance, MTHFR C677T and NOS3 G894T Polymorphisms, and Global DNA Methylation in Mixed Ancestry African Individuals

The aim of this study is to quantify global DNA methylation and investigate the relationship with diabetes status and polymorphisms in MTHFR C677T and NOS3 G894T genes in mixed ancestry subjects from South Africa. Global DNA methylation was measured, and MTHFR rs1801133 and NOS3 rs1799983 polymorphisms were genotyped using high throughput real-time polymerase chain reaction and direct DNA sequencing. Of the 564 participants, 158 (28%) individuals had T2DM of which 97 (17.2%) were screen-detected cases. Another 119 (21.1%) had prediabetes, that is, impaired fasting glucose, impaired glucose tolerance, or the combination of both, and the remainder 287 (50.9%) had normal glucose tolerance. Global DNA methylation was significantly higher in prediabetes and screen-detected diabetes than in normal glucose tolerance (both p ≤ 0.033) and in screen-detected diabetes compared to known diabetes on treatment (p = 0.019). There was no difference in global DNA methylation between known diabetes on treatment and normal glucose tolerance (p > 0.999). In multivariable linear regression analysis, only NOS3 was associated with increasing global DNA methylation (β = 0.943; 95% CI: 0.286 to 1.560). The association of global DNA methylation with screen-detected diabetes but not treated diabetes suggests that glucose control agents to some extent may be reversing DNA methylation. The association between NOS3 rs1799983 polymorphisms and DNA methylation suggests gene-epigenetic mechanisms through which vascular diabetes complications develop despite adequate metabolic control.

Contribution of ENPP1, TCF7L2, and FTO polymorphisms to type 2 diabetes in mixed ancestry ethnic population of South Africa

BACKGROUND

Transcription factor 7-like 2 gene (TCF7L2), fat mass and obesity-associated gene (FTO), and ectonucleotide pyrophosphatase/phosphodiesterase gene (ENPP1) are known risk loci for type 2 diabetes (T2DM) mostly in European populations.

OBJECTIVES

To assess the association of these genes with T2DM risk in a South African mixed-ancestry population.

METHODS

Five hundred and sixty six participants were genotyped for ENPP1-rs997509 and -rs1044498, FTO-9941349 and -rs3751812, TCF7L2-rs12255372 and -rs7903146 polymorphisms using Taqman genotyping assays and validated by automated sequencing to assess the association of the polymorphisms with cardiometabolic traits.

RESULTS

In logistic regression models adjusted for age, sex, body mass index (BMI) and insulin resistance, minor allele of rs997509 was associated with a higher risk of prevalent T2DM under a recessive model [odd ratio 4.60 (95% confidence interval: 1.07 to 19.86); p = 0.040].Under additive model, the rs7903146 [1.43 (1.00 to 2.04); p= 0.053] and rs9941349 [1.43 (1.00 to 2.04); p = 0.052] minor alleles showed marginally significant associations with a high risk of T2DM. However, only the rs7903146 alleles (p=0.011) and genotypes (p=0.025) distributions were statistically significantly different between diabetic and non-diabetic individuals.

CONCLUSION

Our findings demonstrate that ENPP1, TCF7L2, and FTO may predispose to T2DM in the mixed-ancestry population.

Association study of polymorphisms in miRNAs with T2DM in Chinese population

Accumulated evidence indicates that microRNA (miRNA or miR) is involved in the development of type 2 diabetes (T2DM). Several studies have shown that single nucleotide polymorphisms (SNPs) located in miRNAs are associated with T2DM in Caucasian populations. The association studies of miRNA's SNPs with T2DM in Asian are rarely reported, and there are distinct genetic differences between Caucasian and Asian populations. The focus of this study, therefore, is the association of T2DM with five SNPs (rs895819 in miR-27a, rs531564 in miR-124a, rs11888095 in miR-128a, rs3820455 in miR-194a and rs2910164 in miR-146a) located in five miRNAs in a Han Chinese population. A total of 738 subjects with T2DM and 610 non-diabetic subjects were genotyped using the TaqMan method. Next, the associations between the five SNPs with T2DM and individual metabolic traits were evaluated. Our data showed that the C allele of rs531564 in miR-124a may protect against T2DM (P=0.009, OR=0.758; 95%CI: 0.616-0.933). Conversely, the C allele of rs2910164 in miR-146a may increase the risk of developing T2DM (P<0.001, OR=1.459; 95%CI: 1.244-1.712). However, these five SNPs did not exhibit significant associations with individual metabolic traits in either the T2DM or non-diabetic groups. Our results revealed that genetic variations in miRNAs were associated with T2DM susceptibility in a Han Chinese population, and these results highlight the need to study the functional effects of these variants in miRNAs on the risk of developing T2DM.

Causes of type 2 diabetes in China

The prevalence of diabetes in China has increased substantially over recent decades, with more than 100 million people estimated to be affected by the disease presently. During this period there has been an increase in the rates of obesity and a reduction in physical activity. Many of the changes in lifestyle and diet are a result of increased economic development and urbanisation. In addition to an increasingly westernised diet, the traditional Chinese diet also plays a part, with the quantity and quality of rice intake linked to the risk of type 2 diabetes. Familial factors including inherited genetic variants are important, although differences in the genetic architecture suggest a different combination of genetic variants could be most relevant in Chinese when compared with Europeans. Recent advances have also emphasised the role of early life factors in the epidemic of diabetes and non-communicable diseases: maternal undernutrition, maternal obesity, and gestational diabetes are all linked to increased risk of diabetes in offspring. A mismatch between developmentally programmed biology and the modern environment is relevant for countries like China where there has been rapid economic transformation. Multisectoral efforts to address the risks will be needed at different stages throughout the lifecourse to reduce the burden of diabetes.

Dapagliflozin as monotherapy in drug-naive Asian patients with type 2 diabetes mellitus: a randomized, blinded, prospective phase III study

OBJECTIVE

Dapagliflozin is a highly selective, orally active inhibitor of renal sodium-glucose cotransporter 2 that reduces hyperglycemia by increasing urinary glucose excretion. The goal of this study was to evaluate dapagliflozin as monotherapy in drug-naive Asian patients with type 2 diabetes whose disease was inadequately controlled with diet and exercise.

METHODS

In this Phase III, multicenter, parallel-group, double-blind study, drug-naive patients with glycosylated hemoglobin (HbA1c) levels ≥7.0% to ≤10.5% (≥53-≤91 mmol/mol) were randomized (by using an interactive voice response system) to receive placebo (n = 132), dapagliflozin 5 mg (n = 128), or dapagliflozin 10 mg (n = 133). The primary end point was mean change from baseline in HbA1c level at week 24 (last-observation-carried-forward). Secondary end points included changes in fasting plasma glucose, 2-hour postprandial glucose, body weight, and other glycemic parameters.

RESULTS

Baseline characteristics were balanced across groups. Most patients (89%) were Chinese, median disease duration was 0.2 year, and mean HbA1c level was 8.26%. Most patients (87%) completed the study. At week 24, mean reductions in HbA1c were -0.29% for placebo versus -1.04% and -1.11% for dapagliflozin 5 and 10 mg, respectively (P < 0.0001 for both doses). Changes in fasting plasma glucose were 2.5, -25.1, and -31.6 mg/dL (0.14, -1.39, and -1.75 mmol/L) for placebo, dapagliflozin 5 mg, and dapagliflozin 10 mg. Changes in 2-hour postprandial glucose were 1.1, -46.8, and -54.9 mg/dL (0.06, -2.60, and -3.05 mmol/L). Reductions in body weight were -0.27, -1.64, and -2.25 kg. Proportions of patients achieving HbA1c levels <7.0% (53 mmol/mol) were 21.3%, 42.6%, and 49.8%. Adverse events (AEs) occurred in 63.6%, 61.7%, and 60.9% of patients, and serious AEs occurred in 1.5%, 3.9%, and 3.0% of patients. No deaths occurred. Hypoglycemia was uncommon (1.5%, 0.8%, and 0.8%); no hypoglycemic event led to discontinuation. Genital infections occurred in 0.8%, 3.1%, and 4.5% of patients and urinary tract infections in 3.0%, 3.9%, and 5.3% of patients. No AEs of renal infection or pyelonephritis were reported. No changes in renal function or AEs of renal failure occurred.

CONCLUSIONS

Compared with placebo, dapagliflozin 5 and 10 mg demonstrated clinically and statistically significant improvements in HbA1c levels after 24 weeks of treatment. Dose-dependent, statistically significant reductions in fasting plasma glucose, postprandial glucose, and weight were also observed for both doses compared with placebo. AEs and serious AEs were balanced across groups, with low rates of hypoglycemia and no increase in renal events. Genital infections and urinary tract infections were more common with dapagliflozin. Dapagliflozin as monotherapy in these drug-naive Asian patients was well tolerated, significantly improving glycemic control with the additional benefit of weight loss.

Effects of NOS1AP rs12742393 polymorphism on repaglinide response in Chinese patients with type 2 diabetes mellitus

STUDY OBJECTIVE

To investigate the associations of NOS1AP rs12742393 polymorphism with the risk of type 2 diabetes mellitus (T2DM) and repaglinide therapeutic efficacy in Chinese patients with T2DM.

DESIGN

Prospective case-control study.

SETTING

Academic medical center.

PATIENTS

A total of 300 patients with T2DM and 200 healthy volunteers were enrolled to identify NOS1AP rs12742393 genotypes using the polymerase chain reaction-restriction fragment length polymorphism assay. Eighty-four patients with various genotypes were randomly selected to receive oral repaglinide as a single-agent therapy (3 mg/day) for 8 weeks.

MEASUREMENTS AND MAIN RESULTS

Anthropometric measurements and fasting plasma glucose (FPG), postprandial plasma glucose, hemoglobin A1c , fasting serum insulin (FINS), postprandial serum insulin, homeostasis model assessment for insulin resistance (HOMA-IR), triglyceride, total cholesterol, low-density lipoprotein-cholesterol, and high-density lipoprotein-cholesterol tests were obtained before and after repaglinide treatment. The risk C allelic frequency of NOS1AP rs12742393 was higher in patients with T2DM than in healthy volunteers (p<0.001). Patients with T2DM and genotypes AA and AC at NOS1AP rs12742393 had a significant reduction in FPG (mmol/l) compared with those with genotype CC (p<0.01). Patients with CC homozygotes and AC heterozygotes had a greater increase in FINS (mU/l) than those with wild-type AA (p<0.05). In addition, the carriers of genotype CC at NOS1AP rs12742393 had higher differential values of HOMA-IR compared with genotypes AC and AA carriers (p<0.001). The effects of repaglinide treatment on FPG (p<0.01), FINS (p<0.05) and HOMA-IR (p<0.001) were reduced in patients with T2DM carrying the NOS1AP rs12742393 risk C allele compared with the AA genotype carriers.

CONCLUSION

The NOS1AP rs12742393 polymorphism is associated with therapeutic efficacy of repaglinide in Chinese T2DM patients.

Association between glucose transporter 1 rs841853 polymorphism and type 2 diabetes mellitus risk may be population specific (1rs8418532)

BACKGROUND

So far, studies on the association between the glucose transporter 1 (GLUT1) rs841853 polymorphism and type 2 diabetes mellitus (T2DM) risk have generated considerable controversy. The present study was performed to clarify the association of this genetic variation with T2DM.

METHODS

A comprehensive literature search of electronic databases was conducted to obtain articles focused on the relationship between the GLUT1 rs841853 polymorphism and T2DM, followed by a systemic meta-analysis.

RESULTS

Fourteen articles and 19 individual studies were included for analysis. Main analyses revealed extreme heterogeneity and random effect pooled odds ratios (OR) were weakly significant in allele contrast (OR 1.28; 95% confidence interval [CI] 1.01, 1.63; P=0.04) and dominant model (OR 1.52; 95% CI 1.19, 1.94; P=0.0008) for T allele. Subgroup analyses for Caucasians showed marginal positive results in the dominant model. However, analyses for Asians yielded an obvious relationship to T2DM risk in all genetic models. Interestingly, T allele even seemed to be a protective factor against the development of T2DM in Blacks in allele contrast. Sensitivity analyses did not alter materially for most comparisons and no publication bias was found in this meta-analysis.

CONCLUSIONS

The results of the present meta-analysis provide evidence that the GLUT1 rs841853 polymorphism may confer increased susceptibility to T2DM in Asians. However, there is no currently available strong evidence supporting the association between this genetic variation and T2DM in Caucasians, Blacks, or the overall population.

Genetics of type 2 diabetes in European populations

Type 2 diabetes (T2D) has become a leading health problem throughout the world. It is caused by environmental and genetic factors, as well as interactions between the two. However, until very recently, the T2D susceptibility genes have been poorly understood. During the past 5 years, with the advent of genome-wide association studies (GWAS), a total of 58 T2D susceptibility loci have been associated with T2D risk at a genome-wide significance level (P < 5 × 10(-8) ), with evidence showing that most of these genetic variants influence pancreatic β-cell function. Most novel T2D susceptibility loci were identified through GWAS in European populations and later confirmed in other ethnic groups. Although the recent discovery of novel T2D susceptibility loci has contributed substantially to our understanding of the pathophysiology of the disease, the clinical utility of these loci in disease prediction and prognosis is limited. More studies using multi-ethnic meta-analysis, gene-environment interaction analysis, sequencing analysis, epigenetic analysis, and functional experiments are needed to identify new susceptibility T2D loci and causal variants, and to establish biological mechanisms.