Replication of 13 genome-wide association (GWA)-validated risk variants for type 2 diabetes in Pakistani populations

Genetic associations of TMEM154, PRC1 and ZFAND6 loci with type 2 diabetes in an endogamous business community of North India

BACKGROUND

More than 250 loci have been identified by genome-wide scans for type 2 diabetes in different populations. South Asians have a very different manifestation of the diseases and hence role of these loci need to be investigated among Indians with huge burden of cardio-metabolic disorders. Thus the present study aims to validate the recently identified GWAS loci in an endogamous caste population in North India.

METHODS

219 T2D cases and 184 controls were recruited from hospitals and genotyped for 15 GWAS loci of T2D. Regression models adjusted for covariates were run to examine the association for T2D and fasting glucose levels.

RESULTS

We validated three variants for T2D namely, rs11634397 at ZFAND6 (OR = 3.05, 95%CI = 1.02-9.19, p = 0.047) and rs8042680 at PRC1 (OR = 3.67, 95%CI = 1.13-11.93, p = 0.031) showing higher risk and rs6813195 at TMEM154 (OR = 0.28, 95%CI = 0.09-0.90, p = 0.033) showing protective effect. The combined risk of 9 directionally consistent variants was also found to be significantly associated with T2D (OR = 1.91, 95%CI = 1.18-3.08, p = 0.008). One variant rs10842994 at KLHDC5 was validated for 9.15mg/dl decreased fasting glucose levels (SE = -17.25-1.05, p = 0.027).

CONCLUSION

We confirm the role of ZFAND6, PRC1 and TMEM154 in the pathophysiology of type 2 diabetes among Indians. More efforts are needed with larger sample sizes to validate the diabetes GWAS loci in South Asian populations for wider applicability.

Gene Polymorphism of KLF14 rs972283 and Its Association with Type 2 Diabetes Mellitus in the Egyptian patients.. [DOI: 10.21203/rs.3.rs-2798448/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background: An extensive quest for genetic variables impacting the susceptibility for T2DM and other cardiometabolic disorders has been sparked by the global growth in the frequency of those widespread ailments. In Egypt, no previous studies examined the relation between KLF14 rs972283 SNP and the risk of developing T2DM. This study aims to ascertain the genetic influences of KLF14 rs972283 on T2DM in Egypt. Subjects and methods: This study included 50 diabetic patients and 50 healthy subjects. Each individual underwent a clinical assessment and total body examination, laboratory investigations including liver enzymes, FBS, HbA1C, and lipid profile. The DNA Purification Kit was used to separate genomic DNA from the whole blood. Gene polymorphism was detected via the PCR-REFLP method. Results: There was no association between KLF14 (rs972283) gene polymorphism and T2DM among studied people. The distribution of KLF14 rs972283 genotypes in diabetic cases was 9 patients with GG genotype (18%) and 26 with GA (52%) while 15 patients (30%) had homozygous mutant genotype AA. However, in the control group, 7 healthy cases had the GG genotype (14%), 31 (62%) had the GA genotypes, and 12 (24%) had the AA genotype. Concerning the allele frequency, the A allele in the KLF14 rs972283 polymorphism was more frequent in both diabetic and control cases (56% and 55%; respectively), but without significant difference (P=0.887). Conclusion: The present study shows for the first time that rs972283 SNP of the KLF14 gene was not associated with T2DM susceptibility in the Egyptian population. However, this study detects an association between KLF14 rs972283 (GG genotype) and a higher risk for elevated TG and LDL levels in control cases. This could indicate that the presence of the GG genotype even in control cases could be used to predict cardiovascular disease.

Biochemical Activation and Regulatory Functions of Trans-Regulatory KLF14 and Its Association with Genetic Polymorphisms

Krüpple-Like family of transcription factor-14 (KLF14) is a master trans-regulatory gene that has multiple biological regulatory functions and is involved in many pathological mechanisms. It controls the expressions of several other genes which are involved in multiple regulatory functions. KLF14 plays a significant role in lipid metabolism, glucose regulation and insulin sensitivity. Cell apoptosis, proliferation, and differentiation are regulated by the KLF14 gene, and up-regulation of KLF14 prevents cancer progression. KLF14 has been used as an epigenetic biomarker for the estimation of chronological age due to the presence of different age-related CpG sites on genes that become methylated with age. Different genome-wide association studies have identified several KLF14 variants in adipose tissues. These single nucleotide polymorphisms in KLF14 have been associated with dyslipidemia, insulin resistance, and glucose intolerance. Moreover, the prevalence of genetic polymorphism is different in different populations due to ethnic differences and epigenetic modifications. In addition, environmental and physiological factors such as diet, age, gender, and obesity are also responsible for genetic mutations in KLF14.

JAZF1: A metabolic actor subunit of the NuA4/TIP60 chromatin modifying complex

The multisubunit NuA4/TIP60 complex is a lysine acetyltransferase, chromatin modifying factor and gene co-activator involved in diverse biological processes. The past decade has seen a growing appreciation for its role as a metabolic effector and modulator. However, molecular insights are scarce and often contradictory, underscoring the need for further mechanistic investigation. A particularly exciting route emerged with the recent identification of a novel subunit, JAZF1, which has been extensively linked to metabolic homeostasis. This review summarizes the major findings implicating NuA4/TIP60 in metabolism, especially in light of JAZF1 as part of the complex.

Lower Dietary Intake of Plant Protein Is Associated with Genetic Risk of Diabetes-Related Traits in Urban Asian Indian Adults

The increasing prevalence of type 2 diabetes among South Asians is caused by a complex interplay between environmental and genetic factors. We aimed to examine the impact of dietary and genetic factors on metabolic traits in 1062 Asian Indians. Dietary assessment was performed using a validated semi-quantitative food frequency questionnaire. Seven single nucleotide polymorphisms (SNPs) from the Transcription factor 7-like 2 and fat mass and obesity-associated genes were used to construct two metabolic genetic risk scores (GRS): 7-SNP and 3-SNP GRSs. Both 7-SNP GRS and 3-SNP GRS were associated with a higher risk of T2D (p = 0.0000134 and 0.008, respectively). The 3-SNP GRS was associated with higher waist circumference (p = 0.010), fasting plasma glucose (FPG) (p = 0.002) and glycated haemoglobin (HbA1c) (p = 0.000066). There were significant interactions between 3-SNP GRS and protein intake (% of total energy intake) on FPG (Pinteraction = 0.011) and HbA1c (Pinteraction = 0.007), where among individuals with lower plant protein intake (<39 g/day) and those with >1 risk allele had higher FPG (p = 0.001) and HbA1c (p = 0.00006) than individuals with ≤1 risk allele. Our findings suggest that lower plant protein intake may be a contributor to the increased ethnic susceptibility to diabetes described in Asian Indians. Randomised clinical trials with increased plant protein in the diets of this population are needed to see whether the reduction of diabetes risk occurs in individuals with prediabetes.

Diabetes and Genetics: A Relationship Between Genetic Risk Alleles, Clinical Phenotypes and Therapeutic Approaches

Unveiling human genome through successful completion of Human Genome Project and International HapMap Projects with the advent of state of art technologies has shed light on diseases associated genetic determinants. Identification of mutational landscapes such as copy number variation, single nucleotide polymorphisms or variants in different genes and loci have revealed not only genetic risk factors responsible for diseases but also region(s) playing protective roles. Diabetes is a global health concern with two major types - type 1 diabetes (T1D) and type 2 diabetes (T2D). Great progress in understanding the underlying genetic predisposition to T1D and T2D have been made by candidate gene studies, genetic linkage studies, genome wide association studies with substantial number of samples. Genetic information has importance in predicting clinical outcomes. In this review, we focus on recent advancement regarding candidate gene(s) associated with these two traits along with their clinical parameters as well as therapeutic approaches perceived. Understanding genetic architecture of these disease traits relating clinical phenotypes would certainly facilitate population stratification in diagnosing and treating T1D/T2D considering the doses and toxicity of specific drugs.

The KLF14 Variant is Associated with Type 2 Diabetes and HbA1C Level

The purpose of this study was to scan variants in coding region of Krȕppel like factor14 (KLF14) locus and assess association related to type 2 diabetes (T2D) in Iranian population. We sequenced the coding region of KLF14 to scan variants in case-sibling study (92 individuals with T2D and 92 healthy older siblings). To confirm, we analyzed rs76603546 association with T2D in a larger unrelated case-control study by PCR-RFLP (475 cases and 512 controls). We analyzed the association of rs76603546 with HbA_1C, BMI, fat mass, waist circumference, fasting glucose, cholesterol and HOMA-IR (Homeostatic Model Assessment for Insulin Resistance) using one-way ANOVA analysis. Also, association of genotypes with T2D adjusted for confounding variables was analyzed using logistic regression. HaploReg v 4.1 was used to predict rs76603546 possible function. Sequencing results analysis revealed the association of C allele of rs76603546, synonymous variant C>T, [OR 2.10 (1.38-3.20), P value < 0.001] and CC genotype of rs76603546 [OR 4.3 (1.79-10.23), P value = 0.001] with susceptibility to T2D. PCR-Restriction Fragment Length Polymorphism (RFLP) results analysis confirmed the association of rs76603546 with T2D [C allele, OR 1.91 (1.59-2.29), P value = 0.002, CC genotype, OR 3.27 (2.26-4.73), P value = 0.002 and TC genotype, OR 1.74 (1.31-2.31), P value = 0.001]. The CC genotype of rs76603546 is associated with HbA_1C level (P value < 0.001) and BMI (P value = 0.02). After adjustment with confounding variables, we observed association of CC genotype with T2D [OR 2.542 (1.25-3.77), P value = 0.03]. Among over 220 SNPs, rs76603546 was associated with T2D, HbA_1C and BMI in our study.

Association of HLA-B Gene Polymorphisms with Type 2 Diabetes in Pashtun Ethnic Population of Khyber Pakhtunkhwa, Pakistan

Human leukocyte antigen (HLA) system is the most polymorphic and gene dense region of human DNA that has shown many disease associations. It has been further divided into HLA classes I, II, and III. Polymorphism in HLA class II genes has been reported to play an important role in the pathogenesis of type 1 diabetes (T1D). It also showed association with T2D in different ethnic populations. However, a little is known about the relationship of HLA class I gene polymorphism and T2D. This study has evaluated the association of HLA-B (class I gene) variants with T2D in Pashtun ethnic population of Khyber Pakhtunkhwa. In the first phase of the study, whole exome sequencing (WES) of 2 pooled DNA samples was carried out, and DNA pools used were constructed from 100 diabetic cases and 100 control subjects. WES results identified a total of n = 17 SNPs in HLA-B gene. In the next phase, first 5 out of n = 17 reported SNPs were genotyped using MassARRAY® system in order to validate WES results and to confirm association of selected SNPs with T2D. Minor allele frequencies (MAFs) and selected SNPs×T2D association were determined using chi-square test and logistic regression analysis. The frequency of minor C allele was significantly higher in the T2D group as compared to control group (45.0% vs. 13.0%) (p = 0.006) for rs2308655 in HLA-B gene. No significant difference in MAF distribution between cases and controls was observed for rs1051488, rs1131500, rs1050341, and rs1131285 (p > 0.05). Binary logistic regression analyses showed significant results for SNP rs2308655 (OR = 2.233, CI (95%) = 1.223-4.077, and p = 0.009), while no considerable association was observed for the other 4 SNPs. However, when adjusted for these variants, the association of rs2308655 further strengthened significantly (adjusted OR = 7.485, CI (95%) = 2.353-23.812, and p = 0.001), except for rs1131500, which has no additive effect. In conclusion, the finding of this study suggests rs2308655 variant in HLA-B gene as risk variant for T2D susceptibility in Pashtun population.

Pathophysiological Mechanisms Underlying Excess Risk for Diabetes and Cardiovascular Disease in South Asians: The Perfect Storm

BACKGROUND

South Asians are at a significantly increased risk of type 2 diabetes (T2D) and cardiovascular disease (CVD), are diagnosed at relatively younger ages, and exhibit more severe disease phenotypes as compared with other ethnic groups. The pathophysiological mechanisms underlying T2D and CVD risk in South Asians are multifactorial and intricately related.

METHODS

A narrative review of the pathophysiology of excess risk of T2D and CVD in South Asians.

RESULTS

T2D and CVD have shared risk factors that encompass biological factors (early life influences, impaired glucose metabolism, and adverse body composition) as well as behavioral and environmental risk factors (diet, sedentary behavior, tobacco use, and social determinants of health). Genetics and epigenetics also play a role in explaining the increased risk of T2D and CVD among South Asians. Additionally, South Asians harbor several lipid abnormalities including high concentration of small-dense low-density lipoprotein (LDL) particles, elevated triglycerides, low high-density lipoprotein (HDL)- cholesterol levels, dysfunctional HDL particles, and elevated lipoprotein(a) that predispose them to CVD.

CONCLUSION

In this comprehensive review, we have discussed risk factors that provide insights into the pathophysiology of excess risk of T2D and CVD in South Asians.

Association of the JAZF1 Variant in Adults With a Parental History of Type 2 Diabetes Mellitus In Pakistan

Background

Type 2 diabetes mellitus (T2DM) is a chronic multifactorial condition and quickly growing disease in Pakistan. Many genes together with Zinc finger protein 1 (JAZF1) have already been described earlier in the literature but the role of JAZF1 in this subset of the population is yet to define. This study was aimed at identifying JAZF1 polymorphism and the risk of developing T2DM in persons with a parental history of T2DM in the Pakistani population.

Methods

DNA samples from 75 non-diabetic Pakistani participants with a family history of T2DM and 75 controls were evaluated by using a polymerase chain reaction (PCR) and the restriction fragment length polymorphism method.

Results

The alleles AA and AG and the GG genotype of JAZF1 (rs864745) varied considerably in frequency distribution between cases and control (p<0.05). The GG was independently and significantly associated with cases who had a family history of T2DM [odds ratio (OR) 2.6 (95% confidence interval (Cl) 1.3-5.1); p=0.005] while the AA allele was significantly associated with controls without a family history of T2DM [odds ratio (OR) 0.39 (95% confidence interval (Cl) 0.2-0.7); p=0.0059] and the allele AG has no significance and was equally distributed among control and cases with p-value=1.000.

Conclusion

Genotype GG of the JAZF1 variant was found significantly associated with the risk of developing type 2 diabetes mellitus in the Pakistani subset of the population.

Different prevalence of T2DM risk alleles in Roma population in comparison with the majority Czech population

Background

The Czech governmental study suggests up to a 25% higher prevalence of type 2 diabetes mellitus (T2DM) in the Roma population than within the majority population. It is not known whether and to what extent these differences have a genetic background.

Methods

To analyze whether the frequencies of the alleles/genotypes of the FTO, TCF7L2, CDKN2A/2B, MAEA, TLE4, IGF2BP2, ARAP1, and KCNJ11 genes differ between the two major ethnic groups in the Czech Republic, we examined them in DNA samples from 302 Roma individuals and 298 Czech individuals.

Results

Compared to the majority population, Roma are more likely to carry risk alleles in the FTO (26% vs. 16% GG homozygotes, p < .01), IGF2BP2 (22% vs. 10% TT homozygotes, p < .0001), ARAP1 (98% vs. 95% of A allele carriers, p < .005), and CDKN2A/2B (81% vs. 66% of TT homozygotes, p < .001) genes; however, less frequently they are carriers of the TCF7L2 risk allele (34% vs. 48% of the T allele p < .0005). Finally, we found significant accumulation of T2DM‐associated alleles between the Roma population in comparison with the majority population (25.4% vs. 15.2% of the carriers of at least 12 risk alleles; p < .0001).

Conclusion

The increased prevalence of T2DM in the Roma population may have a background in different frequencies of the risk alleles of genes associated with T2DM development.

Transcription Factor KLF14 and Metabolic Syndrome

Metabolic syndrome (MetSyn) is a combination of metabolic abnormalities that lead to the development of cardiovascular disease (CVD) and Type 2 Diabetes (T2D). Although various criteria for defining MetSyn exist, common abnormalities include abdominal obesity, elevated serum triglyceride, insulin resistance, and blood glucose, decreased high-density lipoprotein cholesterol (HDL-C), and hypertension. MetSyn prevalence has been increasing with the rise of obesity worldwide, with significantly higher prevalence in women compared with men and in Hispanics compared with Whites. Affected individuals are at a higher risk of developing T2D (5-fold) and CVD (2-fold). Heritability estimates for individual components of MetSyn vary between 40 and 70%, suggesting a strong contribution of an individual's genetic makeup to disease pathology. The advent of next-generation sequencing technologies has enabled large-scale genome-wide association studies (GWAS) into the genetics underlying MetSyn pathogenesis. Several such studies have implicated the transcription factor KLF14, a member of the Krüpple-like factor family (KLF), in the development of metabolic diseases, including obesity, insulin resistance, and T2D. How KLF14 regulates these metabolic traits and increases the risk of developing T2D, atherosclerosis, and liver dysfunction is still unknown. There have been some debate and controversial results with regards to its expression profile and functionality in various tissues, and a systematic review of current knowledge on KLF14 is lacking. Here, we summarize the research progress made in understanding the function of KLF14 and describe common attributes of its biochemical, physiological, and pathophysiological roles. We also discuss the current challenges in understanding the role of KLF14 in metabolism and provide suggestions for future directions.

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.

Body Composition and Diabetes Risk in South Asians: Findings From the MASALA and MESA Studies

OBJECTIVE

South Asians have a higher prevalence of type 2 diabetes compared with other race/ethnic groups. Body composition is associated with the risk for type 2 diabetes. Differences in body composition between South Asians and other race/ethnic groups are one hypothesized mechanism to explain the disproportionate prevalence of type 2 diabetes in this population.

RESEARCH DESIGN AND METHODS

This study used data from the Mediators of Atherosclerosis in South Asians Living in America (MASALA) and the Multi-Ethnic Study of Atherosclerosis (MESA) cohorts to determine whether body composition mediated the elevated prevalence of impaired fasting glucose and type 2 diabetes in South Asians. Participants (n = 2,615) with complete body composition data were included. Ordinal logistic regression models were calculated to determine the odds for glycemic impairment in South Asians compared with the MESA cohort.

RESULTS

In multivariate models, South Asians had a significantly higher prevalence of glycemic impairment and type 2 diabetes compared with all four race/ethnic groups included in the MESA (P < 0.001 for all). In unadjusted and multivariate adjusted models, South Asians had higher odds for impaired fasting glucose and type 2 diabetes compared with all other race/ethnic groups (P < 0.001 for all). The addition of body composition measures did not significantly mitigate this relationship.

CONCLUSIONS

We did not identify strong evidence that accounting for body composition explains differences in the risk for type 2 diabetes. Future prospective studies of the MESA and MASALA cohorts are needed to understand how adipose tissue impacts the risk for type 2 diabetes and how to best assess this risk.

The Krüppel-Like Factors and Control of Energy Homeostasis

Nutrient handling by higher organisms is a complex process that is regulated at the transcriptional level. Studies over the past 15 years have highlighted the critical importance of a family of transcriptional regulators termed the Krüppel-like factors (KLFs) in metabolism. Within an organ, distinct KLFs direct networks of metabolic gene targets to achieve specialized functions. This regulation is often orchestrated in concert with recruitment of tissue-specific transcriptional regulators, particularly members of the nuclear receptor family. Upon nutrient entry into the intestine, gut, and liver, KLFs control a range of functions from bile synthesis to intestinal stem cell maintenance to effect nutrient acquisition. Subsequently, coordinated KLF activity across multiple organs distributes nutrients to sites of storage or liberates them for use in response to changes in nutrient status. Finally, in energy-consuming organs like cardiac and skeletal muscle, KLFs tune local metabolic programs to precisely match substrate uptake, flux, and use, particularly via mitochondrial function, with energetic demand; this is achieved in part via circulating mediators, including glucocorticoids and insulin. Here, we summarize current understanding of KLFs in regulation of nutrient absorption, interorgan circulation, and tissue-specific use.

Genetic, Functional, and Immunological Study of ZnT8 in Diabetes

Zinc level in the body is finely regulated to maintain cellular function. Dysregulation of zinc metabolism may induce a variety of diseases, e.g., diabetes. Zinc participates in insulin synthesis, storage, and secretion by functioning as a "cellular second messenger" in the insulin signaling pathway and glucose homeostasis. The highest zinc concentration is in the pancreas islets. Zinc accumulation in cell granules is manipulated by ZnT8, a zinc transporter expressed predominately in pancreatic α and β cells. A common ZnT8 gene (SLC30A8) polymorphism increases the risk of type 2 diabetes mellitus (T2DM), and rare mutations may present protective effects. In type 1 diabetes mellitus (T1DM), autoantibodies show specificity for binding two variants of ZnT8 (R or W at amino acid 325) dictated by a polymorphism in SLC30A8. In this review, we summarize the structure, feature, functions, and polymorphisms of ZnT8 along with its association with diabetes and explore future study directions.

Type 2 Diabetes-Associated Genetic Polymorphisms as Potential Disease Predictors

Diabetes is a major cause of mortality worldwide. There are several types of diabetes, with type 2 diabetes mellitus (T2DM) being the most common. Many factors, including environmental and genetic factors, are involved in the etiology of the disease. Numerous studies have reported the role of genetic polymorphisms in the initiation and development of T2DM. While genome-wide association studies have identified around more than 200 susceptibility loci, it remains unclear whether these loci are correlated with the pathophysiology of the disease. The present review aimed to elucidate the potential genetic mechanisms underlying T2DM. We found that some genetic polymorphisms were related to T2DM, either in the form of single-nucleotide polymorphisms or direct amino acid changes in proteins. These polymorphisms are potential predictors for the management of T2DM.

South Asian Cardiovascular Disease & Cancer Risk: Genetics & Pathophysiology

South Asians (SAs) are at heightened risk for cardiovascular disease as compared to other ethnic groups, facing premature and more severe coronary artery disease, and decreased insulin sensitivity. This disease burden can only be partially explained by conventional risk factors, suggesting the need for a specific cardiovascular risk profile for SAs. Current research, as explored through a comprehensive literature review, suggests the existence of population specific genetic risk factors such as lipoprotein(a), as well as population specific gene modulating factors. This review catalogues the available research on cardiovascular disease and genetics, anthropometry, and pathophysiology, and cancer genetics among SAs, with a geographical focus on the U.S. A tailored risk profile will hinge upon population customized classification and treatment guidelines, informed by continued research.

Association of 48 type 2 diabetes susceptibility loci with fasting plasma glucose and lipid levels in Chinese Hans

AIM

Dozens of susceptibility loci have been identified by type 2 diabetes (T2D) genome wide association study (GWAS) in Europeans. In our previous studies, we systematically evaluated the association of 48 susceptibility loci with T2D risk in Chinese Hans. Because dyslipidemia and hyperglycemia are implicated in the pathogenic process of T2D, we further evaluated whether these 48 single nucleotide polymorphisms (SNPs) were related to fasting plasma glucose (FPG) or lipid levels in Chinese Hans.

METHODS

The 48 SNPs were genotyped by using the Taqman OpenArray Genotyping System and iPLEX Sequenom MassARRAY platform. Multiple linear regression was used to assess the relationship between genetic variants and FPG and lipid levels among 3281 non-diabetic, healthy Chinese Hans.

RESULTS

After adjusting for age, gender, body mass index (BMI), smoking status and drinking status, the T allele of rs13266634 in the SLC30A8 gene was significantly associated with decreased glucose level (β = -0.0119, P = 8.05 × 10^-5), whereas the T allele of rs896854 in the TP53INP1 gene was associated with increased triglyceride (TG) level (β = 0.0342, P = 9.61 × 10^-4) and decreased high-density lipoprotein cholesterol (HDL-C) level (β = -0.015, P = 3.24 × 10^-3) after Bonferroni correction. We also conducted a meta-analysis consisted of 11 studies and confirmed that SNP rs896854 in the TP53INP1 gene was associated with T2D risk.

CONCLUSION

Our findings indicated that SNP rs13266634 in SLC30A8 was associated with glucose level and SNP rs896854 in TP53INP1 was associated with lipid level.

Quantitative Relationship Between Cumulative Risk Alleles Based on Genome-Wide Association Studies and Type 2 Diabetes Mellitus: A Systematic Review and Meta-analysis

Many epidemiological studies have assessed the genetic risk of having undiagnosed or of developing type 2 diabetes mellitus (T2DM) using several single nucleotide polymorphisms (SNPs) based on findings of genome-wide association studies (GWAS). However, the quantitative association of cumulative risk alleles (RAs) of such SNPs with T2DM risk has been unclear. The aim of this meta-analysis is to review the strength of the association between cumulative RAs and T2DM risk. Systematic literature searches were conducted for cross-sectional or longitudinal studies that examined odds ratios (ORs) for T2DM in relation to genetic profiles. Logarithm of the estimated OR (log OR) of T2DM for 1 increment in RAs carried (1-ΔRA) in each study was pooled using a random-effects model. There were 46 eligible studies that included 74,880 cases among 249,365 participants. In 32 studies with a cross-sectional design, the pooled OR for T2DM morbidity for 1-ΔRA was 1.16 (95% confidence interval [CI], 1.13–1.19). In 15 studies that had a longitudinal design, the OR for incident T2DM was 1.10 (95% CI, 1.08–1.13). There was large heterogeneity in the magnitude of log OR (P < 0.001 for both cross-sectional studies and longitudinal studies). The top 10 commonly used genes significantly explained the variance in the log OR (P = 0.04 for cross-sectional studies; P = 0.006 for longitudinal studies). The current meta-analysis indicated that carrying 1-ΔRA in T2DM-associated SNPs was associated with a modest risk of prevalent or incident T2DM, although the heterogeneity in the used genes among studies requires us to interpret the results with caution.

Linking Alzheimer's disease and type 2 diabetes: Novel shared susceptibility genes detected by cFDR approach

BACKGROUND

Both type 2 diabetes (T2D) and Alzheimer's disease (AD) occur commonly in the aging populations and T2D has been considered as an important risk factor for AD. The heritability of both diseases is estimated to be over 50%. However, common pleiotropic single-nucleotide polymorphisms (SNPs)/loci have not been well-defined. The aim of this study is to analyze two large public accessible GWAS datasets to identify novel common genetic loci for T2D and/or AD.

METHODS AND MATERIALS

The recently developed novel conditional false discovery rate (cFDR) approach was used to analyze the summary GWAS datasets from International Genomics of Alzheimer's Project (IGAP) and Diabetes Genetics Replication And Meta-analysis (DIAGRAM) to identify novel susceptibility genes for AD and T2D.

RESULTS

We identified 78 SNPs (including 58 novel SNPs) that were associated with AD in Europeans conditional on T2D (cFDR<0.05). 66 T2D SNPs (including 40 novel SNPs) were identified by conditioning on SNPs association with AD (cFDR<0.05). A conjunction-cFDR (ccFDR) analysis detected 8 pleiotropic SNPs with a significance threshold of ccFDR<0.05 for both AD and T2D, of which 5 SNPs (rs6982393, rs4734295, rs7812465, rs10510109, rs2421016) were novel findings. Furthermore, among the 8 SNPs annotated at 6 different genes, 3 corresponding genes TP53INP1, TOMM40 and C8orf38 were related to mitochondrial dysfunction, critically involved in oxidative stress, which potentially contribute to the etiology of both AD and T2D.

CONCLUSION

Our study provided evidence for shared genetic loci between T2D and AD in European subjects by using cFDR and ccFDR analyses. These results may provide novel insight into the etiology and potential therapeutic targets of T2D and/or AD.

Association of Common Genetic Variants in Mitogen-activated Protein Kinase Kinase Kinase Kinase 4 with Type 2 Diabetes Mellitus in a Chinese Han Population

Background:

A study has identified several novel susceptibility variants of the mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) gene for type 2 diabetes mellitus (T2DM) within the German population. Among the variants, five single nucleotide polymorphisms (SNPs) of MAP4K4 (rs1003376, rs11674694, rs2236935, rs2236936, and rs6543087) showed significant association with T2DM or diabetes-related quantitative traits. We aimed to evaluate whether common SNPs in the MAP4K4 gene were associated with T2DM in the Chinese population.

Methods:

Five candidate SNPs were genotyped in 996 patients newly diagnosed with T2DM and in 976 control subjects, using the SNPscan^™ method. All subjects were recruited from the Second Affiliated Hospital, Harbin Medical University from October 2010 to September 2013. We evaluated the T2DM risk conferred by individual SNPs and haplotypes using logistic analysis, and the association between the five SNPs and metabolic traits in the subgroups.

Results:

Of the five variants, SNP rs2236935T/C was significantly associated with T2DM in this study population (odds ratio = 1.293; 95% confidence interval: 1.034–1.619, P = 0.025). In addition, among the controls, rs1003376 was significantly associated with an increased body mass index (P = 0.045) and homeostatic model assessment-insulin resistance (P = 0.037).

Conclusions:

MAP4K4 gene is associated with T2DM in a Chinese Han population, and MAP4K4 gene variants may contribute to the risk toward the development of T2DM.

Cardiometabolic disease in South Asians: A global health concern in an expanding population

Cardiovascular disease (CVD) is one of the main causes of mortality and morbidity worldwide. As an emerging population, South Asians (SAs) bear a disproportionately high burden of CVD relative to underlying classical risk factors, partly attributable to a greater prevalence of insulin resistance and diabetes and distinct genetic and epigenetic influences. While the phenotypic distinctions between SAs and other ethnicities in CVD risk are becoming increasingly clear, the biology of these conditions remains an area of active investigation, with emerging studies involving metabolism, genetic variation and epigenetic modifiers (e.g., extracellular RNA). In this review, we describe the current literature on prevalence, prognosis and CVD risk in SAs, and provide a landscape of translational research in this field toward ameliorating CVD risk in SAs.

KCNQ1 rs2237895 polymorphism is associated with Gestational Diabetes in Pakistani Women

Background and Objective:

Genetic studies on gestational diabetes (GDM) are relatively scarce; moreover, limited data is available for KCNQ1 polymorphism in Pakistani pregnant women. We aimed to determine the frequency of KCNQ1 rs2237895 in GDM and normal pregnant controls and its association with GDM-related phenotypes.

Methods:

A total of 637 pregnant females (429 controls and 208 cases) in their second trimester were classified according to the International Association of the Diabetes and Pregnancy Study criteria in this study. Their blood samples were genotyped for KCNQ1 SNP rs2237895 using PCR-RFLP method and sequencing. Fasting and two hour-post glucose load blood levels, serum HbA1c, insulin, and anthropometric assessment was performed.: Pearson’s Chi Square test, Mann- Whitney U test, and regression analyses were performed. A p-value of <0.05 was considered significant.

Results:

The variant genotyped was in Hardy-Weinberg equilibrium (p>0.05). The rs2237895 showed an association with GDM (OR 2.281; 1.388-3.746: p <0.001) and remained significant after multiple adjustments for age and body mass index (OR 2.068; 1.430-2.997: p=0.005). The C allele showed positive association with insulin level, and HOMA-IR in study subjects.

Conclusions:

This study identifies that KCNQ1 rs2237895 polymorphisms might be associated with risk of GDM in Pakistani population and that it is related to higher glucose levels and insulin resistance. Further large scale studies are required to consolidate on the functional aspect of this polymorphism.

A replication study of 49 Type 2 diabetes risk variants in a Punjabi Pakistani population

AIM

The burden of Type 2 diabetes is alarmingly high in South Asia, a region that has many genetically diverse ethnic populations. Genome-wide association studies (GWAS) conducted largely in European populations have identified a number of loci predisposing to Type 2 diabetes risk, however, the relevance of such genetic loci in many South Asian sub-ethnicities remains elusive. The aim of this study was to replicate 49 single nucleotide polymorphisms (SNPs) previously identified through GWAS in Punjabis living in Pakistan.

METHODS

We examined the association of 49 SNPs in 853 Type 2 diabetes cases and 1945 controls using additive logistic regression models after adjusting for age and gender.

RESULTS

Of the 49 SNPs investigated, eight showed a nominal association (P < 0.05) that also remained significant after controlling for the false discovery rate. The most significant association was found for rs7903146 at the TCF7L2 locus. For a per unit increase in the risk score comprising of all the 49 SNPs, the odds ratio in association with Type 2 diabetes risk was 1.16 (95% CI 1.13-1.19, P < 2.0E-16).

CONCLUSION

These results suggest that some Type 2 diabetes susceptibility loci are shared between Europeans and Punjabis living in Pakistan.

Islet biology, the CDKN2A/B locus and type 2 diabetes risk

Type 2 diabetes, fuelled by the obesity epidemic, is an escalating worldwide cause of personal hardship and public cost. Diabetes incidence increases with age, and many studies link the classic senescence and ageing protein p16(INK4A) to diabetes pathophysiology via pancreatic islet biology. Genome-wide association studies (GWASs) have unequivocally linked the CDKN2A/B locus, which encodes p16 inhibitor of cyclin-dependent kinase (p16(INK4A)) and three other gene products, p14 alternate reading frame (p14(ARF)), p15(INK4B) and antisense non-coding RNA in the INK4 locus (ANRIL), with human diabetes risk. However, the mechanism by which the CDKN2A/B locus influences diabetes risk remains uncertain. Here, we weigh the evidence that CDKN2A/B polymorphisms impact metabolic health via islet biology vs effects in other tissues. Structured in a bedside-to-bench-to-bedside approach, we begin with a summary of the evidence that the CDKN2A/B locus impacts diabetes risk and a brief review of the basic biology of CDKN2A/B gene products. The main emphasis of this work is an in-depth look at the nuanced roles that CDKN2A/B gene products and related proteins play in the regulation of beta cell mass, proliferation and insulin secretory function, as well as roles in other metabolic tissues. We finish with a synthesis of basic biology and clinical observations, incorporating human physiology data. We conclude that it is likely that the CDKN2A/B locus influences diabetes risk through both islet and non-islet mechanisms.

Long noncoding RNA variations in cardiometabolic diseases

Cardiometabolic diseases are characterized as a combination of multiple risk factors for cardiovascular disease (CVD) and metabolic diseases including diabetes mellitus, dyslipidemia, hypertension and abdominal obesity. This cluster of abnormalities individually and interdependently leads to atherosclerosis and CVD morbidity and mortality. In the past decade, genome-wide association studies (GWASs) have identified a series of cardiometabolic disease-associated variants that can collectively explain a small proportion of the variability. Intriguingly, the susceptibility variants imputed from GWASs usually do not reside in the coding regions, suggesting a crucial role of the noncoding elements of the genome. In recent years, emerging evidence suggests that noncoding RNA (ncRNA) is functional for physiology and pathophysiology of human diseases. These include microRNAs and long noncoding RNAs (lncRNAs) that are now implicated in human diseases. The ncRNAs can interact with each other and with proteins, to interfere gene expressions, leading to the development of many human disorders. Although evidence suggests the functional role of lncRNAs in cardiometabolic traits, the molecular mechanisms of gene regulation underlying cardiometabolic diseases remain to be better defined. Here, we summarize the recent discoveries of lncRNA variations in the context of cardiometabolic diseases.

Association between IGF2BP2 Polymorphisms and Type 2 Diabetes Mellitus: A Case-Control Study and Meta-Analysis

Background: Genome-wide association studies (GWAS) found that IGF2BP2 rs4402960 and rs1470579 polymorphisms were associated with type 2 diabetes mellitus (T2DM) risk. Many studies have replicated this association, but yielded inconsistent results. Materials and Methods: A case-control study consisting of 461 T2DM patients and 434 health controls was conducted to detect the genetic susceptibility of IGF2BP2 in a northern Han Chinese population. A meta-analysis was to evaluate the association more precisely in Asians. Results: In the case-control study, the carriers of TT genotype at rs4402960 had a higher T2DM risk than the G carriers (TG + GG) (adjusted odd ratio (AOR) = 1.962, 95% confidence interval (95% CI) = 1.065–3.612, p = 0.031]; CC carriers at rs1470579 were more susceptible to T2DM than A carriers (CA + AA) (AOR = 2.014, 95% CI = 1.114–3.642, p = 0.021). The meta-analysis containing 36 studies demonstrated that the two polymorphisms were associated with T2DM under the allele comparison, genetic models of dominant and recessive in Asians (p < 0.05). The rs4402960 polymorphisms were significantly associated with the T2DM risk after stratification by diagnostic criterion, size of sample and average age and BMI of cases, while there’re no consistent results for rs1470579. Conclusions: Our data suggests that IGF2BP2 polymorphisms are associated with T2DM in Asian populations.

Blood-based biomarkers of age-associated epigenetic changes in human islets associate with insulin secretion and diabetes

Aging associates with impaired pancreatic islet function and increased type 2 diabetes (T2D) risk. Here we examine whether age-related epigenetic changes affect human islet function and if blood-based epigenetic biomarkers reflect these changes and associate with future T2D. We analyse DNA methylation genome-wide in islets from 87 non-diabetic donors, aged 26-74 years. Aging associates with increased DNA methylation of 241 sites. These sites cover loci previously associated with T2D, for example, KLF14. Blood-based epigenetic biomarkers reflect age-related methylation changes in 83 genes identified in human islets (for example, KLF14, FHL2, ZNF518B and FAM123C) and some associate with insulin secretion and T2D. DNA methylation correlates with islet expression of multiple genes, including FHL2, ZNF518B, GNPNAT1 and HLTF. Silencing these genes in β-cells alter insulin secretion. Together, we demonstrate that blood-based epigenetic biomarkers reflect age-related DNA methylation changes in human islets, and associate with insulin secretion in vivo and T2D.

Health and population effects of rare gene knockouts in adult humans with related parents

Examining complete gene knockouts within a viable organism can inform on gene function. We sequenced the exomes of 3222 British adults of Pakistani heritage with high parental relatedness, discovering 1111 rare-variant homozygous genotypes with predicted loss of function (knockouts) in 781 genes. We observed 13.7% fewer homozygous knockout genotypes than we expected, implying an average load of 1.6 recessive-lethal-equivalent loss-of-function (LOF) variants per adult. When genetic data were linked to the individuals' lifelong health records, we observed no significant relationship between gene knockouts and clinical consultation or prescription rate. In this data set, we identified a healthy PRDM9-knockout mother and performed phased genome sequencing on her, her child, and control individuals. Our results show that meiotic recombination sites are localized away from PRDM9-dependent hotspots. Thus, natural LOF variants inform on essential genetic loci and demonstrate PRDM9 redundancy in humans.

Polymorphisms in Four Genes (KCNQ1 rs151290, KLF14 rs972283, GCKR rs780094 and MTNR1B rs10830963) and Their Correlation with Type 2 Diabetes Mellitus in Han Chinese in Henan Province, China

Genetic variants at KCNQ1 rs151290, KLF14 rs972283, GCKR rs780094 and MTNR1B rs10830963 have been associated with type 2 diabetes mellitus (T2DM), but the results are contradictory in Chinese populations. The aim of the present study was to investigate the association of these four SNPs with T2DM in a large population of Han Chinese at Henan province, China. Seven-hundred-thirty-six patients with T2DM (cases) and Seven-hundred-sixty-eight healthy glucose-tolerant controls were genotyped for KCNQ1 rs151290, KLF14 rs972283, GCKR rs780094 and MTNR1B rs10830963. The association of genetic variants in these four genes with T2DM was analyzed using multivariate logistic regression. Genotypes and allele distributions of KCNQ1 rs151290 were significantly different between the cases and controls (p < 0.05). The AC and CC genotypes and the combined AC + CC genotype of rs151290 in KCNQ1 were associated with increases risk of T2DM before (OR = 1.482, 95% CI = 1.062–2.069; p = 0.021; OR = 1.544, 95% CI = 1.097–2.172, p = 0.013; and OR = 1.509, 95% CI = 1.097–2.077, p = 0.011, respectively) and after (OR = 1.539, 95% CI = 1.015–2.332, p = 0.042; OR = 1.641, 95% CI = 1.070–2.516, p = 0.023; and OR = 1.582, 95% CI = 1.061–2.358, p = 0.024; respectively) adjustment for sex, age, anthropometric measurements, biochemical indexes, smoking and alcohol consumption. Consistent with results of genotype analysis, the C allele of rs151290 in KCNQ1 was also associated with increased risk of T2DM (OR = 1.166, 95% CI = 1.004–1.355, p = 0.045). No associations between genetic variants of KLF14 rs972283, GCKR rs780094 or MTNR1B rs10830963 and T2DM were detected. The AC and CC genotypes and the C allele of rs151290 in KCNQ1 may be risk factors for T2DM in Han Chinese in Henan province.

Meta-analytic research on the relationship between cumulative risk alleles and risk of type 2 diabetes mellitus

BACKGROUND

Our aim is to examine the dose-response association between cumulative genetic risk and actual risk of type 2 diabetes mellitus (T2DM) and the influence of adjustment for covariates on T2DM risk through a comprehensive meta-analysis of observational studies.

METHODS

Electronic literature search using EMBASE and MEDLINE (from 2003 to 2014) was conducted for cross-sectional or longitudinal studies that presented the odds ratio (OR) for T2DM in each group with categories based on the total number of risk alleles (RAs) carried (RAtotal ) using at least two single-nucleotide polymorphisms. Spline regression model was used to determine the shape of the relationship between the difference from the referent group of each study in RAtotal (ΔRAtotal ) and the natural logarithms of ORs (log OR) for T2DM.

RESULTS

Sixty-five eligible studies that included 68 267 cases among 182 603 participants were analysed. In both crude and adjusted ORs, defined by adjusting the risk for at least two confounders among age, gender and body mass index, the slope of the log OR for T2DM became less steep as the ΔRAtotal increased. In the analysis limited to 14 cross-sectional and four longitudinal studies presenting both crude and adjusted ORs, regression curves of both ORs in relation to ΔRAtotal were almost identical.

CONCLUSION

Using only single-nucleotide polymorphisms for T2DM screening was of limited value. However, when genotypic T2DM risk was considered independently from risk in relation to covariates, it was suggested that genetic profiles might have a supplementary role related to conventional T2DM risk factors in identifying individuals at high risk of T2DM. Copyright © 2015 John Wiley & Sons, Ltd.

Association Between KCNQ1 Genetic Variants and Type 2 Diabetes in the Uyghur Population

OBJECTIVE

To investigate the association between KCNQ1 gene polymorphisms and type 2 diabetes (T2D) in an admixed ethnic minority, Uyghur population, living in the Northwest region of China.

MATERIALS AND METHODS

We genotyped three tagging single-nucleotide polymorphisms rs2283171, rs11023485, and rs2283208 of the KCNQ1 gene in 1006 T2D participants and 1004 controls and conducted association analysis.

RESULTS

The frequencies of the AG and GG genotypes and the G allele of rs2283171 were higher in the control group (51.4%, 22%, and 47.7%, respectively) than in the case group (49%, 17.6%, and 42.1%, respectively). The minor G allele decreased the risk of T2D with a per-allele odds ratio of 0.79 (95% CI: 0.70-0.90) for the additive genetic model in univariate analysis (p = 0.0001). After adjustment for the covariates of age, gender, smoking, alcohol use, systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), triglyceride (TG), and total cholesterol (TC), the diabetic protective effect of the rs2283171-G allele remained. No difference was observed in the frequency distributions of the rs11023485 and rs2283208 genotypes between the two groups.

CONCLUSION

We identified a novel association between rs2283171 of KCNQ1 and T2D in the Uyghur population. Further association and functional studies are required to identify the causal functional variant that is in linkage disequilibrium with this polymorphism.

Perhexiline activates KLF14 and reduces atherosclerosis by modulating ApoA-I production

Recent genome-wide association studies have revealed that variations near the gene locus encoding the transcription factor Krüppel-like factor 14 (KLF14) are strongly associated with HDL cholesterol (HDL-C) levels, metabolic syndrome, and coronary heart disease. However, the precise mechanisms by which KLF14 regulates lipid metabolism and affects atherosclerosis remain largely unexplored. Here, we report that KLF14 is dysregulated in the liver of 2 dyslipidemia mouse models. We evaluated the effects of both KLF14 overexpression and genetic inactivation and determined that KLF14 regulates plasma HDL-C levels and cholesterol efflux capacity by modulating hepatic ApoA-I production. Hepatic-specific Klf14 deletion in mice resulted in decreased circulating HDL-C levels. In an attempt to pharmacologically target KLF14 as an experimental therapeutic approach, we identified perhexiline, an approved therapeutic small molecule presently in clinical use to treat angina and heart failure, as a KLF14 activator. Indeed, in WT mice, treatment with perhexiline increased HDL-C levels and cholesterol efflux capacity via KLF14-mediated upregulation of ApoA-I expression. Moreover, perhexiline administration reduced atherosclerotic lesion development in apolipoprotein E-deficient mice. Together, these results provide comprehensive insight into the KLF14-dependent regulation of HDL-C and subsequent atherosclerosis and indicate that interventions that target the KLF14 pathway should be further explored for the treatment of atherosclerosis.

Gene-gene and gene-environment interactions in the etiology of type 2 diabetes mellitus in the population of Hyderabad, India

Fifteen SNPs from nine different genes were genotyped on 1379 individuals, 758 T2DM patients and 621 controls, from the city of Hyderabad, India, using Sequenom Massarray platform. These data were analyzed to examine the role of gene-gene and gene-environment interactions in the manifestation of T2DM. The multivariate analysis suggests that TCF7L2, CDKAL1, IGF2BP2, HHEX and PPARG genes are significantly associated with T2DM, albeit only the first two of the above 5 were associated in the univariate analysis. Significant gene-gene and gene-environment interactions were also observed with reference to TCF7L2, CAPN10 and CDKAL1 genes, highlighting their importance in the pathophysiology of T2DM. In the analysis for cumulative effect of risk alleles, SLC30A8 steps in as significant contributor to the disease by its presence in all combinations of risk alleles. A striking difference between risk allele categories, 1-4 and 5-6, was evident in showing protective and susceptible roles, respectively, while the latter was characterized by the presence of TCF7L2 and CDKAL1 variants. Overall, these two genes TCF7L2 and CDKAL1 showed strong association with T2DM, either individually or in interaction with the other genes. However, we need further studies on gene-gene and gene-environment interactions among heterogeneous Indian populations to obtain unequivocal conclusions that are applicable for the Indian population as a whole.

Data interpretation: deciphering the biological function of Type 2 diabetes associated risk loci

AIMS

Type 2 diabetes (T2D) is a complex multifactorial disorder with more than 40 loci associated with disease susceptibility. Most of these genome-wide significant loci reside in noncoding regions, it is important to decipher the potential regulatory function of these variants and to differentiate between true and tag signals. Nowadays, databases are being developed to study and predict the function of these associated variants, and RegulomeDB is one such database.

METHODS

We used RegulomeDB to analyze the potential function of the associated variants reported in five genome-wide association studies (GWAS) of T2D.

RESULTS

We investigated the 1,567 single nucleotide polymorphisms (SNPs) with 989 SNPs with a score of 1-6. Of those 989 SNPs, only 64 returned with RegulomeDB score <3 (evidence of regulatory function), and only four of these were GWAS significant SNPs (THADA/rs10203174, score = 1b; UBE2E2/rs7612463, score = 2a; ARAP1/rs1552224 and TP53INP1/rs8996852, score = 2b). But only 63 % of the annotated SNPs showed regulatory function that is an important limitation of the RegulomeDB as this database only provides information of few regulatory elements.

CONCLUSION

This study further supports that some of the noncoding GWAS variants are the true associations and not the tag ones. This study also proves the utility and importance of the RegulomeDB and other such databases. Although it is an extensive database of regulatory elements but has certain limitation due to utilization of only few types of regulatory elements and pathways.

Selective Expression of the MAPK Phosphatase Dusp9/MKP-4 in Mouse Plasmacytoid Dendritic Cells and Regulation of IFN-β Production

Plasmacytoid dendritic cells (pDCs) efficiently produce large amounts of type I IFN in response to TLR7 and TLR9 ligands, whereas conventional DCs (cDCs) predominantly secrete high levels of the cytokines IL-10 and IL-12. The molecular basis underlying this distinct phenotype is not well understood. In this study, we identified the MAPK phosphatase Dusp9/MKP-4 by transcriptome analysis as selectively expressed in pDCs, but not cDCs. We confirmed the constitutive expression of Dusp9 at the protein level in pDCs generated in vitro by culture with Flt3 ligand and ex vivo in sorted splenic pDCs. Dusp9 expression was low in B220(-) bone marrow precursors and was upregulated during pDC differentiation, concomitant with established pDC markers. Higher expression of Dusp9 in pDCs correlated with impaired phosphorylation of the MAPK ERK1/2 upon TLR9 stimulation. Notably, Dusp9 was not expressed at detectable levels in human pDCs, although these displayed similarly impaired activation of ERK1/2 MAPK compared with cDCs. Enforced retroviral expression of Dusp9 in mouse GM-CSF-induced cDCs increased the expression of TLR9-induced IL-12p40 and IFN-β, but not of IL-10. Conditional deletion of Dusp9 in pDCs was effectively achieved in Dusp9(flox/flox); CD11c-Cre mice at the mRNA and protein levels. However, the lack of Dusp9 in pDC did not restore ERK1/2 activation after TLR9 stimulation and only weakly affected IFN-β and IL-12p40 production. Taken together, our results suggest that expression of Dusp9 is sufficient to impair ERK1/2 activation and enhance IFN-β expression. However, despite selective expression in pDCs, Dusp9 is not essential for high-level IFN-β production by these cells.

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.

Type 2 diabetes and gut microbiome: at the intersection of known and unknown

The prevalence of metabolic syndrome is increasing rapidly across the globe. Though the prevalence of the disease is similar in population of upper middle income and high income countries, the age of affected population is lower in upper middle income countries. This is attributed to genetic as well as changing life style factors. The contributing factors for type 2 diabetes range from genetic/epigenetic disposal, intra uterine nutrition, dietary pattern to sedentary lifestyle. The role of the gut microbiota in metabolic disorders is increasingly gaining importance. Several studies have reported significant difference in the profile of the gut microbiota in Caucasian population considering obese and type 2 diabetic populations while limited number of studies are available on populations from the developing world. The metabolites from the gut microbes contribute to the gut barrier integrity and a compromised barrier leads to leakage of inflammatory mediators into systemic circulation and hence increases insulin resistance. Attempts have been made at correcting metabolic syndrome through dietary changes by altering the gut microbiota with some success. This report is an attempt to explain the hypothesis of compromised nutrition altering the gut microbiota, gut metabolites, gut barrier function, systemic inflammation and hence insulin response.

Functional genomics of the CDKN2A/B locus in cardiovascular and metabolic disease: what have we learned from GWASs?

Genome-wide association studies (GWASs) provide an unprecedented opportunity to examine, on a large scale, the association of common genetic variants with complex diseases like type 2 diabetes (T2D) and cardiovascular disease (CVD), thus allowing the identification of new potential disease loci. Using this approach, numerous studies have associated SNPs on chromosome 9p21.3 situated near the cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) locus with the risk for coronary artery disease (CAD) and T2D. However, identifying the function of the nearby gene products (CDKN2A/B and ANRIL) in the pathophysiology of these conditions requires functional genomic studies. We review the current knowledge, from studies using human and mouse models, describing the function of CDKN2A/B gene products, which may mechanistically link the 9p21.3 risk locus with CVD and diabetes.

The Uyghur population and genetic susceptibility to type 2 diabetes: potential role for variants in CDKAL1, JAZF1, and IGF1 genes

Substantial evidence suggests that type 2 diabetes mellitus (T2DM) is a multi-factorial disease with a strong genetic component. A list of genetic susceptibility loci in populations of European and Asian ancestry has been established in the literature. Little is known on the inter-ethnic contribution of such established functional polymorphic variants. We performed a case-control study to explore the genetic susceptibility of 16 selected T2DM-related SNPs in a cohort of 102 Uyghur objects (51 cases and 51 controls). Three of the 16 SNPs showed significant association with T2DM in the Uyghur population. There were significant differences between the T2DM and control groups in frequencies of the risk allelic distributions of rs7754840 (CDKAL1) (p=0.014), rs864745 (JAZF1) (p=0.032), and rs35767 (IGF1) (p=0.044). Carriers of rs7754840-C, rs35767-A, and rs864745-C risk alleles had a 2.32-fold [OR (95% CI): 1.19-4.54], 2.06-fold [OR (95% CI): 1.02-4.17], 0.48-fold [OR (95% CI): 0.24-0.94] increased risk for T2DM, respectively. The cumulative risk allelic scores of these 16 SNPs differed significantly between the T2DM patients and the controls [17.1±8.1 vs. 15.4±7.3; OR (95%CI): 1.27(1.07-1.50), p=0.007]. This is the first study to evaluate genomic variation at 16 SNPs in respective T2DM candidate genes for the Uyghur population compared with other ethnic groups. The SNP rs7754840 in CDKAL1, rs864745 in JAZF1, and rs35767 in IGF1 might serve as potential susceptibility loci for T2DM in Uyghurs. We suggest a broader capture and study of the world populations, including who that are hitherto understudied, are essential for a comprehensive understanding of the genetic/genomic basis of T2DM.

Cumulative effect and predictive value of genetic variants associated with type 2 diabetes in Han Chinese: a case-control study

Background

Genome-wide association studies (GWAS) have identified dozens of single nucleotide polymorphisms (SNPs) associated with type 2 diabetes risk. We have previously confirmed the associations of genetic variants in HHEX, CDKAL1, VEGFA and FTO with type 2 diabetes in Han Chinese. However, the cumulative effect and predictive value of these GWAS identified SNPs on the risk of type 2 diabetes in Han Chinese are largely unknown.

Methodology/Principal Findings

We conducted a two-stage case-control study consisting of 2,925 cases and 3,281controls to examine the association of 30 SNPs identified by GWAS with type 2 diabetes in Han Chinese. Significant associations were found for proxy SNPs at KCNQ1 [odds ratio (OR) = 1.41, P = 9.91 × 10–16 for rs2237897], CDKN2A/CDKN2B (OR = 1.30, P = 1.34 × 10–10 for rs10811661), CENTD2 (OR = 1.28, P = 9.88 × 10-4 for rs1552224) and SLC30A8 (OR = 1.19, P = 1.43 × 10-5 for rs13266634). We further evaluated the cumulative effect on type 2 diabetes of these 4 SNPs, in combination with 5 SNPs at HHEX, CDKAL1, VEGFA and FTO reported previously. Individuals carrying 12 or more risk alleles had a nearly 4-fold increased risk for developing type 2 diabetes compared with those carrying less than 6 risk alleles [adjusted OR = 3.68, 95% confidence interval (CI): 2.76–4.91]. Adding the genetic factors to clinical factors slightly improved the prediction of type 2 diabetes, with the area under the receiver operating characteristic curve increasing from 0.76 to 0.78. However, the difference was statistically significant (P < 0.0001).

Conclusions/Significance

We confirmed associations of SNPs in KCNQ1, CDKN2A/CDKN2B, CENTD2 and SLC30A8 with type 2 diabetes in Han Chinese. The utilization of genetic information may improve the accuracy of risk prediction in combination with clinical characteristics for type 2 diabetes.

Diabetes and associated complications in the South Asian population

The rising prevalence of diabetes in South Asians has significant health and economic implications. South Asians are predisposed to the development of diabetes due to biologic causes which are exacerbated by lifestyle and environmental factors. Furthermore, they experience significant morbidity and mortality from complications of diabetes, most notably coronary artery disease, cerebrovascular disease, and chronic kidney disease. Therefore, understanding the pathophysiology and genetics of diabetes risk factors and its associated complications in South Asians is paramount to curbing the diabetes epidemic. With this understanding, the appropriate screening, preventative and therapeutic strategies can be implemented and further developed. In this review, we discuss in detail the biologic and lifestyle factors that predispose South Asians to diabetes and review the epidemiology and pathophysiology of microvascular and macrovascular complications of diabetes in South Asians. We also review the ongoing and completed diabetes prevention and management studies in South Asians.

Does genetic heterogeneity account for the divergent risk of type 2 diabetes in South Asian and white European populations?

AIMS/HYPOTHESIS

South Asians are up to four times more likely to develop type 2 diabetes than white Europeans. It is postulated that the higher prevalence results from greater genetic risk. To evaluate this hypothesis, we: (1) systematically reviewed the literature for single nucleotide polymorphisms (SNPs) predisposing to type 2 diabetes in South Asians; (2) compared risk estimates, risk alleles and risk allele frequencies of predisposing SNPs between South Asians and white Europeans; and (3) tested the association of novel SNPs discovered from South Asians in white Europeans.

METHODS

MEDLINE, Embase, the Cumulative Index to Nursing and Allied Health Literature (CINAHL) and the Cochrane registry were searched for studies of genetic variants associated with type 2 diabetes in South Asians. Meta-analysis estimates for common and novel bi-allelic SNPs in South Asians were compared with white Europeans from the DIAbetes Genetics Replication And Meta-analysis (DIAGRAM) consortium. The population burden from predisposing SNPs was assessed using a genotype score.

RESULTS

Twenty-four SNPs from 21 loci were associated with type 2 diabetes in South Asians after meta-analysis. The majority of SNPs increase odds of the disorder by 15-35% per risk allele. No substantial differences appear to exist in risk estimates between South Asians and white Europeans from SNPs common to both groups, and the population burden also does not differ. Eight of the 24 are novel SNPs discovered from South Asian genome-wide association studies, some of which show nominal associations with type 2 diabetes in white Europeans.

CONCLUSIONS/INTERPRETATION

Based on current literature there is no strong evidence to indicate that South Asians possess a greater genetic risk of type 2 diabetes than white Europeans.

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.

Evaluation of common type 2 diabetes risk variants in a South Asian population of Sri Lankan descent

INTRODUCTION

Most studies seeking common variant associations with type 2 diabetes (T2D) have focused on individuals of European ancestry. These discoveries need to be evaluated in other major ancestral groups, to understand ethnic differences in predisposition, and establish whether these contribute to variation in T2D prevalence and presentation. This study aims to establish whether common variants conferring T2D-risk in Europeans contribute to T2D-susceptibility in the South Asian population of Sri Lanka.

METHODOLOGY

Lead single nucleotide polymorphism (SNPs) at 37 T2D-risk loci attaining genome-wide significance in Europeans were genotyped in 878 T2D cases and 1523 normoglycaemic controls from Sri Lanka. Association testing was performed by logistic regression adjusting for age and sex and by the Cochran-Mantel-Haenszel test after stratifying according to self-identified ethnolinguistic subgroup. A weighted genetic risk score was generated to examine the combined effect of these SNPs on T2D-risk in the Sri Lankan population.

RESULTS

Of the 36 SNPs passing quality control, sixteen showed nominal (p<0.05) association in Sri Lankan samples, fifteen of those directionally-consistent with the original signal. Overall, these association findings were robust to analyses that accounted for membership of ethnolinguistic subgroups. Overall, the odds ratios for 31 of the 36 SNPs were directionally-consistent with those observed in Europeans (p = 3.2×10(-6)). Allelic odds ratios and risk allele frequencies in Sri Lankan subjects were not systematically different to those reported in Europeans. Genetic risk score and risk of T2D were strongly related in Sri Lankans (per allele OR 1.10 [95%CI 1.08-1.13], p = 1.2×10(-17)).

CONCLUSION

Our data indicate that most T2D-risk variants identified in Europeans have similar effects in South Asians from Sri Lanka, and that systematic difference in common variant associations are unlikely to explain inter-ethnic differences in prevalence or presentation of T2D.