Association between KCNJ11 gene polymorphisms and risk of type 2 diabetes mellitus in East Asian populations: a meta-analysis in 42,573 individuals

KCNJ11 rs5219 Gene Polymorphism Is Associated With T2DM in a Population of Bangladesh: A Case-Control Study

Introduction: As a polygenic disorder, Type 2 diabetes mellitus is a prevalent disease developed by many multigenetic factors, of which multiple genes located on different chromosomes contribute to its susceptibility. The KCNJ11 gene is involved in the Kir6.2 proteins that help release insulin from the potassium channels in pancreatic beta cells. Many studies have found that KCNJ11 polymorphism is significantly associated with the incidence of T2DM. Therefore, this study was carried out to investigate the association between KCNJ11 gene polymorphism and T2DM in the Bangladeshi population. Materials and Methods: In a case-control study (n = 697), 326 nondiabetic controls and 371 diabetic subjects (diagnosed based on American Diabetes Association criteria) were recruited for this study. The serum fasting glucose, lipid profiles, creatinine, alanine aminotransferase (ALT), HbA1C, and serum insulin level were measured by standard methods. HOMA-B%, HOMA-S%, and HOMA-IR were calculated using HOMA-SIGMA software Version 2.2. A standard formula calculated QUICKI and Secretory-HOMA. The chemical method was used for DNA extraction from whole blood samples. The PCR-RFLP method was used to detect KCNJ11 polymorphisms by restriction enzyme (BanII) digestion. As appropriate, data were analyzed using an independent t-test, chi-square, or Fisher exact test. p < 0.05 was considered significant. Results: The frequency of the risk allele K was significantly higher in the T2DM group than control (p ≤ 0.01). The frequency of the KK genotype was higher among the T2DM group (3.77% vs. 1.84%, p < 0.05), and the frequency of the EK genotype was significantly higher among the T2DM than the control group (42.86% vs. 27.91%, p < 0.001). The EE genotype was significantly associated with T2DM in the dominant model EE + EK with an OR of 2.06 (95% CI 1.51-2.82, p ≤ 0.001). Conclusion: This study showed that rs5219 polymorphism of the KCNJ11 gene is a significant risk factor for Type 2 diabetes mellitus in the Bangladeshi population.

Sex differences of the shared genetic landscapes between type 2 diabetes and peripheral artery disease in East Asians and Europeans

Type 2 diabetes (T2D) is a critical risk factor for peripheral artery disease (PAD). However, the sex differences in genetic basis, causality, and underlying mechanisms of the two diseases are still unclear. Using sex-stratified and ethnic-based GWAS summary, we explored the genetic correlation and causal relationship between T2D and PAD in both ethnicities and sexes by linkage disequilibrium score regression, LAVA and six Mendelian Randomization approaches. We observed stronger genetic correlations between T2D and PAD in females than males in East Asians and Europeans. East Asian females exhibit higher causal effects of T2D on PAD than males. The gene-level analysis found KCNJ11 and ANK1 genes associated with the cross-trait of T2D and PAD in both sexes. Our study provides genetic evidence for the sex difference of genetic correlations and causal relationships between PAD and T2D, indicating the importance of using sex-specific strategies for monitoring PAD in T2D patients.

Metabolic and Genetic Markers Improve Prediction of Incident Type 2 Diabetes: A Nested Case-Control Study in Chinese

CONTEXT

It is essential to improve the current predictive ability for type 2 diabetes (T2D) risk.

OBJECTIVE

We aimed to identify novel metabolic markers for future T2D in Chinese individuals of Han ethnicity and to determine whether the combined effect of metabolic and genetic markers improves the accuracy of prediction models containing clinical factors.

METHODS

A nested case-control study containing 220 incident T2D patients and 220 age- and sex- matched controls from normoglycemic Chinese individuals of Han ethnicity was conducted within the Wuxi Non-Communicable Disease cohort with a 12-year follow-up. Metabolic profiling detection was performed by high-performance liquid chromatography‒mass spectrometry (HPLC-MS) by an untargeted strategy and 20 single nucleotide polymorphisms (SNPs) associated with T2D were genotyped using the Iplex Sequenom MassARRAY platform. Machine learning methods were used to identify metabolites associated with future T2D risk.

RESULTS

We found that abnormal levels of 5 metabolites were associated with increased risk of future T2D: riboflavin, cnidioside A, 2-methoxy-5-(1H-1, 2, 4-triazol-5-yl)- 4-(trifluoromethyl) pyridine, 7-methylxanthine, and mestranol. The genetic risk score (GRS) based on 20 SNPs was significantly associated with T2D risk (OR = 1.35; 95% CI, 1.08-1.70 per SD). The area under the receiver operating characteristic curve (AUC) was greater for the model containing metabolites, GRS, and clinical traits than for the model containing clinical traits only (0.960 vs 0.798, P = 7.91 × 10-16).

CONCLUSION

In individuals with normal fasting glucose levels, abnormal levels of 5 metabolites were associated with future T2D. The combination of newly discovered metabolic markers and genetic markers could improve the prediction of incident T2D.

Independent case-control study in KCNJ11 gene polymorphism with Type 2 diabetes Mellitus

Background

Type 2 Diabetes Mellitus (T2DM) is the most common form of diabetes in the aging population. This chronic metabolic disorder has discovered many candidate genes, and KCNJ11 was one of the genes associated with insulin secretion pathways mediated by potassium channels. There have been limited studies on the rs5210 polymorphism in T2DM patients, and none of them have been conducted in Saudi Arabia.

Aim

The aim of this study is to investigate at genotyping levels of rs5210 polymorphism in the KCNJ11 gene in older population with T2DM in the Saudi Population.

Methods

Based on the sample size design, this case-control study included 102 T2DM cases and 102 controls. Using the PCR-RFLP assay, 204 patients extracted DNA was genotyped for the rs5210 polymorphism. SPSS software was used for statistical analysis, including t-tests, HWE, genotyping, and multiple logistic regression analysis.

Results

The t-tests performed on T2DM cases and controls revealed a significant association in age, weight, BMI, FBG, Hb1Ac, SBP, DBP, HDLC, TC, and TG parameters (p < 0.05). HWE analysis found to be in consistent with rs5210 polymorphism. Allelic association was found in the rs5210 polymorphism (OR-1.64 [95 %CI: 1.08-2.49]; p = 0.01); however, no association (p > 0.05) was observed in the multivariate logistic regression assessment performed in this study.

Conclusion

These results indicate that the rs5210 polymorphism was primarily associated with allele frequencies, which could be attributable to the small sample size. Large sample size studies will be required to determine whether KCNJ11 gene polymorphisms may be required as a risk marker for T2DM in the Saudi population.

Genetic diversity of 'Very Important Pharmacogenes' in two South-Asian populations

OBJECTIVES

Reliable identification of population-specific variants is important for building the single nucleotide polymorphism (SNP) profile. In this study, genomic variation using allele frequency differences of pharmacologically important genes for Gujarati Indians in Houston (GIH) and Indian Telugu in the U.K. (ITU) from the 1000 Genomes Project vis-à-vis global population data was studied to understand its role in drug response.

METHODS

Joint genotyping approach was used to derive variants of GIH and ITU independently. SNPs of both these populations with significant allele frequency variation (minor allele frequency ≥ 0.05) with super-populations from the 1000 Genomes Project and gnomAD based on Chi-square distribution with p-value of ≤ 0.05 and Bonferroni's multiple adjustment tests were identified. Population stratification and fixation index analysis was carried out to understand genetic differentiation. Functional annotation of variants was carried out using SnpEff, VEP and CADD score.

RESULTS

Population stratification of VIP genes revealed four clusters viz., single cluster of GIH and ITU, one cluster each of East Asian, European, African populations and Admixed American was found to be admixed. A total of 13 SNPs belonging to ten pharmacogenes were identified to have significant allele frequency variation in both GIH and ITU populations as compared to one or more super-populations. These SNPs belong to VKORC1 (rs17708472, rs2359612, rs8050894) involved in Vitamin K cycle, cytochrome P450 isoforms CYP2C9 (rs1057910), CYP2B6 (rs3211371), CYP2A2 (rs4646425) and CYP2A4 (rs4646440); ATP-binding cassette (ABC) transporter ABCB1 (rs12720067), DPYD1 (rs12119882, rs56160474) involved in pyrimidine metabolism, methyltransferase COMT (rs9332377) and transcriptional factor NR1I2 (rs6785049). SNPs rs1544410 (VDR), rs2725264 (ABCG2), rs5215 and rs5219 (KCNJ11) share high fixation index (≥ 0.5) with either EAS/AFR populations. Missense variants rs1057910 (CYP2C9), rs1801028 (DRD2) and rs1138272 (GSTP1), rs116855232 (NUDT15); intronic variants rs1131341 (NQO1) and rs115349832 (DPYD) are identified to be 'deleterious'.

CONCLUSIONS

Analysis of SNPs pertaining to pharmacogenes in GIH and ITU populations using population structure, fixation index and allele frequency variation provides a premise for understanding the role of genetic diversity in drug response in Asian Indians.

Risk of type 2 diabetes mellitus and cardiovascular complications in KCNJ11, HHEX and SLC30A8 genetic polymorphisms carriers: A case-control study

BACKGROUND

Type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD) are two deadly diseases caused by the complex interaction of multiple genetic loci, lifestyle and environmental factors. Genome-wide association studies described hundreds of susceptibility loci for T2DM and T2DM-related CVD, but it remains uncertain due to geographic and ethnic variations. The objective of this study was to evaluate the associations of KCNJ11 rs5219, SLC30A8 rs13266634 and HHEX rs1111875 polymorphisms with T2DM and related CVD.

METHODS

Genotyping of all three polymorphisms was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method on 250 T2DM cases and 246 healthy controls. Both descriptive and inferential statistical methods were applied using MedCalc and IBM SPSS software programs for statistical analyses.

RESULTS

A significantly increased association of KCNJ11 rs5219 (p<0.05) with T2DM was found in dominant, recessive, heterozygote, homozygote, and allele model (aOR = 2.23, 2.03, 1.90, 3.09, and 1.80, respectively). For SLC30A8 rs13266634, only dominant, heterozygote, and allele model (aOR = 3.37, 3.59, and 1.79, respectively) showed significantly increased association with T2DM. SNP rs1111875 (HHEX) also revealed 2.08, 4.18, 5.93, and 2.08-times significant association in dominant, recessive, homozygote, and allele models. Besides, a significantly reduced correlation of KCNJ11 rs5219 was found with T2DM-related CVD in the recessive and allele model (aOR = 0.40 and 0.65, respectively). Again, a significant difference was observed between T2DM-related CVD and non-CVD patients in terms of gender distribution, fasting blood glucose (FBG), systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TC), and triglycerides (TG).

CONCLUSIONS

Our investigation indicates that KCNJ11 rs5219, SLC30A8 rs13266634 and HHEX rs1111875 polymorphisms are associated with T2DM. Moreover, KCNJ11 rs5219 polymorphism is correlated with the risk of T2DM-related CVD.

Diabetic kidney disease in type 2 diabetes: a review of pathogenic mechanisms, patient-related factors and therapeutic options

The global prevalence of diabetic kidney disease is rapidly accelerating due to an increasing number of people living with type 2 diabetes. It has become a significant global problem, increasing human and financial pressures on already overburdened healthcare systems. Interest in diabetic kidney disease has increased over the last decade and progress has been made in determining the pathogenic mechanisms and patient-related factors involved in the development and pathogenesis of this disease. A greater understanding of these factors will catalyse the development of novel treatments and influence current practice. This review summarises the latest evidence for the factors involved in the development and progression of diabetic kidney disease, which will inform better management strategies targeting such factors to improve therapeutic outcomes in patients living with diabetes.

Association of common genetic variants of KCNJ11 gene with the risk of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a multifactorial polygenic disease. Potassium inwardly-rectifying channel, subfamily J, member 11 (KCNJ11) gene mutations can result in susceptibility of T2DM. The aim of this study is to investigate the relationship between risk of T2DM and its complications (retinopathy & renal) and polymorphisms rs5210 and rs5215 of the KCNJ11 gene in a group of Iranian population. In this case-control study, 111 Iranian patients with T2DM and 82 control subjects were genotyped for each polymorphism by polymerase chain reaction (PCR) and Sanger Sequencing methods. Frequencies of genotypes of rs5210 polymorphism among subjects with and without diabetes mellitus were 53.15% vs. 51.22% for GG and 37.84% vs. 42.68% for AG (p = 0.7), respectively. Corresponding frequencies for rs5215 polymorphism among diabetics and non-diabetics were 13.51% vs. 13.41% for CC and 50.45% vs. 37.80% for CT (p = 0.2). G allele carriers (rs5210 polymorphism) and C allele carriers (rs5215 polymorphism) had the same frequency among diabetics and non-diabetics (p = 0.9 for G allele and p = 0.2 for C allele). Our results suggested that none of the polymorphisms of KCNJ11, rs5210 (p = 0.7) and rs5215 (p = 0.2), were significantly associated with T2DM. Only, the relationship between CT genotype of rs5215 and retinopathy (p = 0.01) showed a borderline significant association.

Association of Genetic Variants of KCNJ11 and KCNQ1 Genes with Risk of Type 2 Diabetes Mellitus (T2DM) in the Indian Population: A Case-Control Study

Type 2 diabetes mellitus (T2DM) is a polygenic metabolic disease described by hyperglycemia, which is caused by insulin resistance or reduced insulin secretion. The interaction between various genetic variants and environmental factors triggers T2DM. The aim of this study was to find risk associated with genetic variants rs5210 and rs2237895 of KCNJ11 and KCNQ1 genes, respectively, in the development of T2DM in the Indian population. A total number of 300 cases of T2DM and 100 control samples were studied to find the polymorphism in KCNJ11 and KCNQ1 through PCR-RFLP. The genotype and allele frequencies in T2DM cases were significantly different compared to the control population. KCNJ11 rs5210 and KCNQ1 rs2237895 variants were found to be significantly associated with risk of T2DM in dominant (KCNJ11: OR, 2.07; 95% CI, 1.30-3.27; p - 0.001; KCNQ1: OR, 2.33; 95% CI, 1.46-3.70; p - 0.0003) and codominant models (KCNJ11: OR, 1.76; 95% CI, 1.09-2.84; p - 0.020; KCNQ1: OR, 1.85; 95% CI, 1.16-2.95; p - 0.009). We also compared clinicopathological characteristics between cases and control and observed a significant difference in all the parameters except HDL, gender, and family history. In this study, clinicopathological data with a carrier of a variant allele of both KCNJ11 and KCNQ1 genes were also analysed, and a significant association was found between the carrier of a variant allele with gender and PPG in KCNJ11 and with triglyceride in KCNQ1. We confirm the significant association of KCNJ11 (rs5210) and KCNQ1 (rs2237895) gene polymorphism with T2DM, indicating the role of these variants in developing risk for T2DM in Indian population.

Genetic confirmation of T2DM meta-analysis variants studied in gestational diabetes mellitus in an Indian population

BACKGROUND

Meta-analysis is useful for combining the results of different studies statistically to confirm genuine associations in genetics. Based on earlier reports, we aimed to investigate the association between type 2 diabetes mellitus (T2DM) genetic variants identified in a previous meta-analysis in gestational diabetes mellitus (GDM) in an Indian woman.

MATERIAL AND METHODS

In this study, 137 pregnant women with GDM and 150 pregnant women were selected on the basis of their serum glucose levels. The six single nucleotide polymorphisms (SNPs) of different genes studied had known involvement in pancreatic β-cell function, particular pathways linked to T2DM, and other biological functions. Genomic DNA was isolated from the 287 women for polymerase chain reaction and restriction fragment length polymorphism analyses.

RESULTS

The rs7903146, rs13266634, rs2283228, rs5210 and rs179881 SNPs were found to be positively associated with GDM when calculated for genotype and allele frequencies (p < 0.05), but rs680 (ApaI) variant did not show statistically significant association (p = 0.31). The rs7903146, rs2283228, rs5210 and rs680 variants showed a strong association with oral glucose tolerance test values.

CONCLUSION

The SNPs studied in this GDM had the same role as those identified in a previous T2DM meta-analysis, and showed positive association in the Indian women. Meta-analyses should be implemented to assess the IGF2 gene in GDM subjects.

Potassium measurements and risk of type 2 diabetes: a dose-response meta-analysis of prospective cohort studies

Objective

To clarify the relationship between serum, dietary, and urinary potassium and the risk of type 2 diabetes mellitus (T2DM).

Materials and Methods

We searched PubMed and EMBASE through January 6, 2017 for studies reporting risk estimates on the association of potassium measurements and the risk of T2DM. The summary risk estimates were obtained through a random-effects model. Dose-response analysis was conducted.

Results

Eight studies involving 5,053 cases and 119,993 individuals were included. A trend toward significance was found in the highest versus lowest meta-analysis on serum potassium and T2DM risk (RR = 0.79; 95% CI 0.60-1.04); moreover, the RR per 1 mmol/L increase in serum potassium was 0.83 (95% CI 0.73-0.95). A non-significant association of dietary potassium and T2DM risk was detected (RR for the highest versus lowest category: 0.93; 95% CI 0.81-1.06; RR for every 1000mg increase per day: 1.00, 95% CI 0.96-1.05). A similar non-significant association was found for urinary potassium and T2DM risk (RR for the highest versus lowest category: 0.83; 95% CI 0.39-1.75; RR per 10 mmol increase: 1.00; 95% CI 0.95-1.05). Evidence of a linear association between serum, dietary, and urinary potassium and the risk of T2DM was found (all P_{non-linearity} > 0.05).

Conclusions

Low serum potassium increases the risk of T2DM in a linear dose-response manner; nevertheless, neither dietary potassium nor urinary potassium shows any association with the risk of T2DM. However, these findings should be interpreted with caution due to limited studies.

Utilizing Genetic Predisposition Score in Predicting Risk of Type 2 Diabetes Mellitus Incidence: A Community-based Cohort Study on Middle-aged Koreans

Contribution of genetic predisposition to risk prediction of type 2 diabetes mellitus (T2DM) was investigated using a prospective study in middle-aged adults in Korea. From a community cohort of 6,257 subjects with 8 yr' follow-up, genetic predisposition score with subsets of 3, 18, 36 selected single nucleotide polymorphisms (SNPs) (genetic predisposition score; GPS-3, GPS-18, GPS-36) in association with T2DM were determined, and their effect was evaluated using risk prediction models. Rs5215, rs10811661, and rs2237892 were in significant association with T2DM, and hazard ratios per risk allele score increase were 1.11 (95% confidence intervals: 1.06-1.17), 1.09 (1.01-1.05), 1.04 (1.02-1.07) with GPS-3, GPS-18, GPS-36, respectively. Changes in AUC upon addition of GPS were significant in simple and clinical models, but the significance disappeared in full clinical models with glycated hemoglobin (HbA1c). For net reclassification index (NRI), significant improvement observed in simple (range 5.1%-8.6%) and clinical (3.1%-4.4%) models were no longer significant in the full models. Influence of genetic predisposition in prediction ability of T2DM incidence was no longer significant when HbA1c was added in the models, confirming HbA1c as a strong predictor for T2DM risk. Also, the significant SNPs verified in our subjects warrant further research, e.g. gene-environmental interaction and epigenetic studies.

Replication of KCNJ11 (p.E23K) and ABCC8 (p.S1369A) Association in Russian Diabetes Mellitus 2 Type Cohort and Meta-Analysis

The genes ABCC8 and KCNJ11 have received intense focus in type 2 diabetes mellitus (T2DM) research over the past two decades. It has been hypothesized that the p.E23K (KCNJ11) mutation in the 11p15.1 region may play an important role in the development of T2DM. In 2009, Hamming et al. found that the p.1369A (ABCC8) variant may be a causal factor in the disease; therefore, in this study we performed a meta-analysis to evaluate the association between these single nucleotide polymorphisms (SNPs), including our original data on the Siberian population (1384 T2DM and 414 controls). We found rs5219 and rs757110 were not associated with T2DM in this population, and that there was linkage disequilibrium in Siberians (D’=0.766, r²= 0.5633). In addition, the haplotype rs757110[T]-rs5219[C] (p.23K/p.S1369) was associated with T2DM (OR = 1.52, 95% CI: 1.04-2.24). We included 44 original studies published by June 2014 in a meta-analysis of the p.E23K association with T2DM. The total OR was 1.14 (95% CI: 1.11-1.17) for p.E23K for a total sample size of 137,298. For p.S1369A, a meta-analysis was conducted on a total of 10 studies with a total sample size of 14,136 and pooled OR of 1.14 [95% CI (1.08-1.19); p = 2 x 10^-6]. Our calculations identified causal genetic variation within the ABCC8/KCNJ11 region for T2DM with an OR of approximately 1.15 in Caucasians and Asians. Moreover, the OR value was not dependent on the frequency of p.E23K or p.S1369A in the populations.

Genetic Determinants of Type 2 Diabetes in Asians

Type 2 diabetes (T2D) has become a major health problem throughout the world and the epidemic is particularly severe in Asian countries. Compared with European populations, Asians tend to develop diabetes at a younger age and at much higher incidence rates given the same amount of weight gain. Genome-wide association studies (GWAS) have identified over 70 loci associated with T2D. Although the majority of GWAS results were conducted in populations of European ancestry, recent GWAS in Asians have made important contributions to the identification of T2D susceptibility loci. These studies not only confirmed T2D susceptibility loci initially identified in European populations, but also identified novel susceptibility loci that provide new insights into the pathophysiology of diseases. In this article, we review GWAS results of T2D conducted in East and South Asians and compare them to those of European populations. Currently identified T2D genetic variants do not appear to explain the phenomenon that Asians are more susceptible to T2D than European populations, suggesting further studies in Asian populations are needed.

The E23K and A190A variations of the KCNJ11 gene are associated with early-onset type 2 diabetes and blood pressure in the Chinese population

Conflicting associations between define (KCNJ11) variations and susceptibility to late-onset (>40 years old) type 2 diabetes mellitus (T2DM) have been reported in different ethnic groups. We investigated whether the E23K (G→A, rs5219) or A190A (C→T, rs5218) variations in KCNJ11 are associated with early-onset T2DM and blood pressure in the Chinese population. Case-control study of 175 unrelated Chinese patients with early-onset T2DM (age of onset <40 years old) who receive (ins+, n = 57) or do not receive insulin (ins-, n = 118), and 182 non-diabetic control subjects. PCR-direct sequencing was performed to genotype E23K and A190A; the genotypic frequencies and associations with clinical characteristics were analyzed. The genotypic frequencies of E23K-GA+AA were higher and A190A-TT was lower in the early-onset T2DM group, especially the T2D-ins+ group, compared to the non-diabetic control group (p < 0.01 or 0.05, respectively). In non-diabetic subjects, E23K-AA carriers had significantly higher 2 h plasma glucose and lower 2 h insulin than E23K-GG carriers (both p < 0.05). A190A-TT or E23K-GG carriers had higher systolic blood pressure (SBP) than CC or AA carriers in the non-diabetic control and T2DM groups (both p < 0.05). In the T2DM ins+ group, E23K-AA carriers had lower onset age and duration of diabetes and higher BMI than GG carriers, and A190A-TT carriers had higher SBP than CC carriers (all p < 0.05). The E23K-GA or AA genotypes may increase the susceptibility to early-onset T2DM, while A190A-TT may protect against early-onset T2DM. On the other hand the A190A-TT or E23K-GG genotypes may increase the risk of hypertension in the Chinese population.

Population specific impact of genetic variants in KCNJ11 gene to type 2 diabetes: a case-control and meta-analysis study

BACKGROUND AND OBJECTIVES

Potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11) gene have a key role in insulin secretion and is of substantial interest as a candidate gene for type 2 diabetes (T2D). The current work was performed to delineate the genetic influence of KCNJ11 polymorphisms on risk of T2D in South Indian population through case-control association study along with systematic review and meta-analysis.

METHODS

A case-control study of 400 T2D cases and controls of South Indian origin were performed to analyze the association of KCNJ11 polymorphisms (rs5219, rs5215, rs41282930, rs1800467) and copy number variations (CNV) on the risk of T2D. In addition a systematic review and meta-analysis for KCNJ11 rs5219 was conducted in 3,831 cases and 3,543 controls from 5 published reports from South-Asian population by searching various databases. Odds ratio with 95% confidence interval (CI) was used to assess the association strength. Cochran's Q, I2 statistics were used to study heterogeneity between the eligible studies.

RESULTS

KCNJ11 rs5215, C-G-C-C haplotype and two loci analysis (rs5219 vs rs1800467) showed a significant association with T2D but CNV analysis did not show significant variation between T2D cases and control subjects. Lower age of disease onset (P = 0.04) and higher body mass index (BMI) (P = 0.04) were associated with rs5219 TT genotype in T2D patients. The meta-analysis of KCNJ11 rs5219 on South Asian population showed no association on susceptibility to T2D with an overall pooled OR = 0.98, 95% CI = 0.83-1.16. Stratification analysis showed East Asian population and global population were associated with T2D when compared to South Asians.

CONCLUSION

KCNJ11 rs5219 is not independently associated with T2D in South-Indian population and our meta-analysis suggests that KCNJ11 polymorphism (rs5219) is associated with risk of T2D in East Asian population and global population but this outcome could not be replicated in South Asian sub groups.

Association between E23K variant in KCNJ11 gene and new-onset diabetes after liver transplantation

New-onset diabetes after transplantation (NODAT) is an important complication after solid organ transplantation. NODAT is a polygenic disease and KCNJ11 E23K polymorphism is considered as a diabetes-susceptibility gene. The present study aimed to assess the association between KCNJ11 (rs5219) variants and the risk of developing NODAT after liver transplantation. This study was conducted on 120 liver transplant recipients who had received tacrolimus-based immunosuppressive drugs. The liver transplant recipients were divided into an new onset diabetes mellitus (NODM) and a non-NODM group. The NODAT group consisted of 60 patients who developed diabetes in the first 6 months after transplantation, while the non-NODAT group included 60 patients who remained euglycemic. The patients were genotyped using polymerase chain reaction-restriction fragment length polymorphism and the incidence of NODAT was compared between the two groups. Nongenetic risk factors including donor gender and cold ischemia time, and recipient (MELD score, presence of viral hepatitis, acute rejection and steroid pulse therapy) were also considered. The KCNJ11 KK variant was associated with an increased risk for NODAT with respective odds ratio of 6.03 (95 % confidence interval 2.37-15.4; P < 0.001]. Donor age and male sex, recipient age as well as fasting plasma glucose before transplantation were significantly different between NODAT and non-NODAT groups (P < 0.05). The prednisolone daily dosage was significantly higher in the NODAT group (P = 0.01). These patients received pulse of methyl prednisolone for treatment of acute rejection. This study showed that polymorphisms in KCNJ11 might predispose the patients treated by tacrolimus to development of NODAT after liver transplantation.

Quantitative assessment of the effect of KCNJ11 gene polymorphism on the risk of type 2 diabetes

To clarify the role of potassium inwardly-rectifying-channel, subfamily-J, member 11 (KCNJ11) variation in susceptibility to type 2 diabetes (T2D), we performed a systematic meta-analysis to investigate the association between the KCNJ11 E23K polymorphism (rs5219) and the T2D in different genetic models. Databases including PubMed, Medline, EMBASE, and ISI Web of Science were searched to identify relevant studies. A total of 48 published studies involving 56,349 T2D cases, 81,800 controls, and 483 family trios were included in this meta-analysis. Overall, the E23K polymorphism was significantly associated with increased T2D risk with per-allele odds ratio (OR) of 1.12 (95% CI: 1.09-1.16; P<10-5). The summary OR for T2D was 1.09 (95% CI: 1.03-1.14; P<10-5), and 1.26 (95% CI: 1.17-1.35; P<10-5), for heterozygous and homozygous, respectively. Similar results were also detected under dominant and recessive genetic models. When stratified by ethnicity, significantly increased risks were found for the polymorphism in Caucasians and East Asians. However, no such associations were detected among Indian and other ethnic populations. Significant associations were also observed in the stratified analyses according to different mean BMI of cases and sample size. Although significant between study heterogeneity was identified, meta-regression analysis suggested that the BMI of controls significantly correlated with the magnitude of the genetic effect. The current meta-analysis demonstrated that a modest but statistically significant effect of the 23K allele of rs5219 polymorphism in susceptibility to T2D. But the contribution of its genetic variants to the epidemic of T2D in Indian and other ethnic populations appears to be relatively low.

Mitochondrial DNA haplogroups and risk of new-onset diabetes among tacrolimus-treated renal transplanted patients

BACKGROUND AND AIMS

Tacrolimus (Tac) is an immunosuppressive drug widely used to avoid organ rejection. New-onset diabetes after transplantation (NODAT) is a major complication among transplanted patients who receive Tac. The increased risk for NODAT could be partly mediated by the effect of Tac on mitochondria from pancreatic beta-cells. Common and rare mitochondrial DNA variants have been linked to the risk of diabetes. Our aim was to determine whether mtDNA polymorphisms/haplogroups were associated with NODAT in Tac-treated kidney transplanted.

METHODS

Seven polymorphisms that define the common European haplogroups were determined in 115 NODAT and 197 no-NODAT patients.

RESULTS

Haplogroup H was significantly more frequent in the NODAT group (50% vs. 35%; p=0.01, OR=1.82). There was no difference between patients without and with (n=106) D2M prior to the transplant.

CONCLUSIONS

Mitochondrial haplogroup H was associated with the risk for NODAT among Tac-treated transplanted patients. The reported differences between the mtDNA variants could explain the increased NODAT-risk among H-patients.

Role of genetic polymorphisms of ion channels in the pathophysiology of coronary microvascular dysfunction and ischemic heart disease

Conventionally, ischemic heart disease (IHD) is equated with large vessel coronary disease. However, recent evidence has suggested a role of compromised microvascular regulation in the etiology of IHD. Because regulation of coronary blood flow likely involves activity of specific ion channels, and key factors involved in endothelium-dependent dilation, we proposed that genetic anomalies of ion channels or specific endothelial regulators may underlie coronary microvascular disease. We aimed to evaluate the clinical impact of single-nucleotide polymorphisms in genes encoding for ion channels expressed in the coronary vasculature and the possible correlation with IHD resulting from microvascular dysfunction. 242 consecutive patients who were candidates for coronary angiography were enrolled. A prospective, observational, single-center study was conducted, analyzing genetic polymorphisms relative to (1) NOS3 encoding for endothelial nitric oxide synthase (eNOS); (2) ATP2A2 encoding for the Ca²⁺/H⁺-ATPase pump (SERCA); (3) SCN5A encoding for the voltage-dependent Na⁺ channel (Nav1.5); (4) KCNJ8 and KCNJ11 encoding for the Kir6.1 and Kir6.2 subunits of K-ATP channels, respectively; and (5) KCN5A encoding for the voltage-gated K⁺ channel (Kv1.5). No significant associations between clinical IHD manifestations and polymorphisms for SERCA, Kir6.1, and Kv1.5 were observed (p > 0.05), whereas specific polymorphisms detected in eNOS, as well as in Kir6.2 and Nav1.5 were found to be correlated with IHD and microvascular dysfunction. Interestingly, genetic polymorphisms for ion channels seem to have an important clinical impact influencing the susceptibility for microvascular dysfunction and IHD, independent of the presence of classic cardiovascular risk factors.

Association of TRPC1 gene polymorphisms with type 2 diabetes and diabetic nephropathy in Han Chinese population

The recent genome-wide association studies reveal that chromosome 3q resides within the linkage region for diabetic nephropathy (DN) in type 1 and type 2 diabetes mellitus (T1D and T2D). The TRPC1 gene is on chromosome 3q22-24, and it has been demonstrated that TRPC1 expression is reduced in the kidney of diabetic animal models. Genetic association of TRPC1 polymorphism with T1D and DN has been reported in European Americans. However, there are no studies reporting the association of TRPC1 genetic polymorphism with T2D with and without DN in Chinese population. This study aimed to demonstrate the genetic role of TRPC1 in the development of T2D with and without DN in Chinese Han population. A genetic association study of TRPC1 was performed in T2D cases and in nondiabetic controls from Han population located in Northern Chinese areas. Six tag single nucleotide polymorphism (SNP) markers derived from HapMap data were genotyped. Among the six SNPs, only rs7638459 was suspected as risk factor of T2D without DN, fitting the log-additive model. The adjusted odds ratio (OR) for the CC genotyping was 2.39 (95% confidence interval (CI) = 1.00-5.68), compared with the TT genotyping. In addition, rs953239 was found to be a protective factor of getting DN in T2D, also fitting the log-additive model. When compared with the AA genotyping for SNP rs953239, the adjusted OR for CC genotyping was 0.63 (95% CI = 0.44-0.99). To summarize, this study shows that TRPC1 genetic polymorphisms are associated with T2D and DN in T2D in the Han Chinese population.

The association of genetic variants of type 2 diabetes with kidney function

Type 2 diabetes is highly prevalent and is the major cause of progressive chronic kidney disease in American Indians. Genome-wide association studies identified several loci associated with diabetes but their impact on susceptibility to diabetic complications is unknown. We studied the association of 18 type 2 diabetes genome-wide association single-nucleotide polymorphisms (SNPs) with estimated glomerular filtration rate (eGFR; MDRD equation) and urine albumin-to-creatinine ratio in 6958 Strong Heart Study family and cohort participants. Center-specific residuals of eGFR and log urine albumin-to-creatinine ratio, obtained from linear regression models adjusted for age, sex, and body mass index, were regressed onto SNP dosage using variance component models in family data and linear regression in unrelated individuals. Estimates were then combined across centers. Four diabetic loci were associated with eGFR and one locus with urine albumin-to-creatinine ratio. A SNP in the WFS1 gene (rs10010131) was associated with higher eGFR in younger individuals and with increased albuminuria. SNPs in the FTO, KCNJ11, and TCF7L2 genes were associated with lower eGFR, but not albuminuria, and were not significant in prospective analyses. Our findings suggest a shared genetic risk for type 2 diabetes and its kidney complications, and a potential role for WFS1 in early-onset diabetic nephropathy in American Indian populations.

Association between a common KCNJ11 polymorphism (rs5219) and new-onset posttransplant diabetes in patients treated with Tacrolimus

KCNJ11 polymorphisms have been linked to the risk of developing type 2 diabetes. Our aim was to define the contribution of KCNJ11 to new-onset diabetes after transplantation (NODAT) among patients treated with Tacrolimus (Tac). A total of 115 NODAT and 205 non-NODAT were genotyped for rs5219 (p.E23K). AA+AG genotypes were significantly associated with NODAT-risk (p=0.004; OR=2.10). The reported effect of this KCNJ11 polymorphism on insulin release by beta cells could explain this association.