Replication of genome-wide association studies of type 2 diabetes susceptibility in Japan

FTO gene variants (rs9939609, rs8050136 and rs17817449) and type 2 diabetes mellitus risk: A Meta-Analysis

BACKGROUND AND AIMS

There is tremendous increase in type 2 diabetes mellitus (T2DM) worldwide. The impact of FTO gene polymorphisms on the risk of T2DM is not yet clear because of the controversial results of studies. This meta-analysis aimed to better clarify the association between three FTO gene polymorphisms SNPs (rs9939609, rs8050136 and rs17817449) and T2DM in a larger combined population worldwide.

MATERIAL AND METHODS

A comprehensive search on the PubMed, Science Direct, and Web of Science databases was conducted to identify investigations in relationship between different FTO gene polymorphisms (rs9939609, rs8050136 and rs17817449) and T2DM globally. Published papers from January 2007 to May 2023 were collected. Inclusion criteria are limited to human case-control studies published in English and peer-reviewed, which provided data on the genotype distributions of FTO gene polymorphisms and T2DM risk. Odds ratios (OR) and 95% confidence intervals (CI) were calculated to express the results of the meta-analysis. Potential sources of bias and heterogeneity using Egger's regression analysis were also assessed.

RESULTS

Of 234695 identified articles, forty-eight studies were selected including 36,051 patients with T2DM and 51,266 control subjects. Overall, we found a significant increased risk of T2DM susceptibility and rs9939609 FTO gene polymorphism in the Allele contrast (A vs. T: OR = 1,30, 95% CI = 1.14; 1.48, P < 0,05, I2 = 0,94), Recessive model (AA vs. AT + TT: OR = 1,54, 95% CI = 1.19; 2.00, P < 0,05, I2 = 0,94), Dominant model (AA + AT vs. TT: OR = 1,26, 95% CI = 1.10; 1.45, P < 0,05, I2 = 0,89), homozygote model (AA vs. TT: OR = 1,60, 95% CI = 1.26; 2.03, P < 0,05, I2 = 0,90), and heterozygote model (AA vs. AT: OR = 1,43, 95% CI = 1.09; 1.88, P = 0,008, I2 = 0,93). we also found a significantly increased risk of T2DM susceptibility and rs8050136 FTO gene polymorphism under all models. For rs17817449 we did not find any association between with T2DM.

CONCLUSION

The present meta-analysis confirms that rs9939609 and rs8050136 in the FTO gene are significantly associated with T2DM, while rs17817449 does not show any association.

Zinc intake, SLC30A8 rs3802177 polymorphism, and colorectal cancer risk in a Korean population: a case-control study

PURPOSE

Zinc is an essential micronutrient involving in multiple enzymatic reactions of human metabolism and biological functions affecting the cancer development. However, the relationship between dietary zinc intake and colorectal cancer (CRC) risk has been unclear. Herein, our study investigated the relationship between dietary zinc intake and CRC risk, and examined how the SLC30A8 rs3802177 genetic variant affects this association.

METHODS

A total of 1431 CRC cases and 2704 controls were selected to investigate the relationship between dietary zinc intake and CRC risk. After excluding individuals without genotype data, 1097 CRC cases and 1559 controls were used to evaluate the interaction between dietary zinc intake and the rs3802177 polymorphism in CRC risk. The odds ratios (ORs) and 95% confidence intervals (CIs) were measured using unconditional logistic regression models.

RESULTS

Higher dietary zinc intake was inversely associated with the risk of CRC in the total population [adjusted OR (aOR) = 0.80, 95% CI 0.66-0.96, p for trend = 0.018]. In the codominant model, G+ carriers of the SLC30A8 rs3802177 with higher consumption of zinc were observed to have a significantly lower risk of CRC in all participants (p for interaction = 0.020). In females, GG carriers with higher zinc intake showed a stronger protective effect against the development of CRC (p for interaction = 0.008).

CONCLUSIONS

In summary, our findings suggest an inverse association between dietary zinc intake and CRC risk, and this relationship may be modified by SLC30A8 rs3802177 polymorphism.

N6-methyladenosine RNA modification: an emerging molecule in type 2 diabetes metabolism

Type 2 diabetes (T2D) is a metabolic disease with an increasing rate of incidence worldwide. Despite the considerable progress in the prevention and intervention, T2D and its complications cannot be reversed easily after diagnosis, thereby necessitating an in-depth investigation of the pathophysiology. In recent years, the role of epigenetics has been increasingly demonstrated in the disease, of which N6-methyladenosine (m6A) is one of the most common post-transcriptional modifications. Interestingly, patients with T2D show a low m6A abundance. Thus, a comprehensive analysis and understanding of this phenomenon would improve our understanding of the pathophysiology, as well as the search for new biomarkers and therapeutic approaches for T2D. In this review, we systematically introduced the metabolic roles of m6A modification in organs, the metabolic signaling pathways involved, and the effects of clinical drugs on T2D.

Gene-environment interactions in the associations of PFAS exposure with insulin sensitivity and beta-cell function in a Faroese cohort followed from birth to adulthood

BACKGROUND

Exposure to perfluoroalkyl substances (PFAS) has been associated with changes in insulin sensitivity and pancreatic beta-cell function in humans. Genetic predisposition to diabetes may modify these associations; however, this hypothesis has not been yet studied.

OBJECTIVES

To evaluate genetic heterogeneity as a modifier in the PFAS association with insulin sensitivity and pancreatic beta-cell function, using a targeted gene-environment (GxE) approach.

METHODS

We studied 85 single-nucleotide polymorphisms (SNPs) associated with type 2 diabetes, in 665 Faroese adults born in 1986-1987. Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were measured in cord whole blood at birth and in participants' serum from age 28 years. We calculated the Matsuda-insulin sensitivity index (ISI) and the insulinogenic index (IGI) based on a 2 h-oral glucose tolerance test performed at age 28. Effect modification was evaluated in linear regression models adjusted for cross-product terms (PFAS*SNP) and important covariates.

RESULTS

Prenatal and adult PFOS exposures were significantly associated with decreased insulin sensitivity and increased beta-cell function. PFOA associations were in the same direction but attenuated compared to PFOS. A total of 58 SNPs were associated with at least one PFAS exposure variable and/or Matsuda-ISI or IGI in the Faroese population and were subsequently tested as modifiers in the PFAS-clinical outcome associations. Eighteen SNPs showed interaction p-values (PGxE) < 0.05 in at least one PFAS-clinical outcome association, five of which passed False Discovery Rate (FDR) correction (PGxE-FDR<0.20). SNPs for which we found stronger evidence for GxE interactions included ABCA1 rs3890182, FTO rs9939609, FTO rs3751812, PPARG rs170036314 and SLC12A3 rs2289116 and were more clearly shown to modify the PFAS associations with insulin sensitivity, rather than with beta-cell function.

DISCUSSION

Findings from this study suggest that PFAS-associated changes in insulin sensitivity could vary between individuals as a result of genetic predisposition and warrant replication in independent larger populations.

Insulin-like Growth Factor-2 Binding Protein-2 Gene Polymorphisms in Iraqi Patients with Type 2 Diabetes Mellitus

Background: Diabetes mellitus type2 (T2DM) represent a hyperglycemia causing metabolic disease which exists in the peripheral tissues due to incomplete pancreatic insulin secretion or insulin resistance. IGF2BP2 is a protein that is involved in embryogenesis and pancreatic development. Genetic association researches had suggested that the single nucleotide polymorphisms (SNP) spanning IGF2BP2 gene are associated with the progression as well as development of the T2DM. Aim: This study aims to evaluate the association of IGF2BP2 gene polymorphisms (rs4402960 & rs1470579) with T2DM in a sample of Iraqi individuals. Methods: A case-control study has been conducted on 800 participants, they were divided to two equal groups, which are a healthy control group (400) and type 2 diabetic patients (400). Fast blood sugar (FBS), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and HbA1c] measured suitable for both participant groups. IGF2BP2 gene has been genotyped for polymorphisms; rs4402960 and rs1470579 by using the PCR-RFLP technique. Results: There is significant changes in the biochemical parameters in patients group when compared to the control group.The SNP rs4402960 show minor allele frequency of T allele considerably different between the two participating groups (p 0.0013) with 33.6 % in T2DM group. Homo-variant TT shows a significant p <0.0001) odd ratio (4.5) as codominant type. Similarly, dominant and recessive models exert significant (0.02 & <0.0001 respectively) adjusted odd ratio (1.45 & 4.14 respectively). The rs1470579 SNP show a significant (0.024) risk (1.28) of C allele in the patients group than in A allele. The CC genotype in codominant and recessive models show significant (0.03) odd ratio differences (2.03 & 1.96 respectively. The rs1470579 SNP exerts significant differences as codominant model in biochemical features of BMI, FBG, Tgs, VLDL-C, insulin and HOMA-IR. The study power of rs4402960 is 69.5% and rs1470579 is 34.1%. Conclusion: This study confirmed the association of rs4402960 as codominant, dominant and recessive with T2DM significantly. However, rs1470579 is associate as recessive model with T2DM in Iraqi population. 

Replication of gene polymorphisms associated with periodontitis-related traits in an elderly cohort: the Washington Heights/Inwood Community Aging Project Ancillary Study of Oral Health

AIM

We sought to replicate findings from published genome-wide association studies (GWAS), linking specific candidate gene loci with periodontitis-related clinical/microbial traits.

MATERIALS AND METHODS

In the published GWAS, a total of 2196 single nucleotide polymorphisms associated with periodontitis-related traits at a p ≤ 5 × 10^-6 and mapped to 136 gene loci. The replication cohort included 1124 individuals, 65-98 years old (67% female, 45% Hispanic, 30% Black, 23% White) with available genome-wide genotypes and full-mouth periodontal status. Microbial profiles using checkerboard DNA-DNA hybridization and 16SrRNA sequencing were available from 912 and 739 participants, respectively.

RESULTS

Using gene-specific p-values after linkage disequilibrium pruning, the following gene/phenotype associations replicated successfully: CLEC19A with edentulism and %teeth with pocket depth (PD) ≥4 mm; IL37, HPVC1, TRPS1, ABHD12B, LDLRAD4 (C180rF1), TGM3, and GRK5 with %teeth with PD ≥4 mm; DAB2IP with presence of PD ≥6 mm; KIAA1715(LNPK), ROBO2, RAB28, LINC01017, NELL1, LDLRAD4(C18orF1), and CRYBB2P1 with %teeth with clinical attachment level (CAL) ≥3 mm; RUNX2 and LAMA2 with %teeth with CAL ≥5 mm; and KIAA1715(LNPK) with high colonization by Aggregatibacter actinomycetemcomitans. In addition, CLEC19A, IQSEC1, and EMR1 associated with microbial abundance based on checkerboard data, LBP and NCR2 with abundance based on sequencing data, and NCR2 with microbial diversity based on sequencing data.

CONCLUSIONS

Several gene loci identified in published GWAS as associated with periodontitis-related phenotypes replicated successfully in an elderly cohort.

Contribution of genetic variant identified in HHEX gene in the overweight Saudi patients confirmed with type 2 diabetes mellitus

Background

The rs7932837 polymorphism in the Hematopoietically expressed homeobox (HHEX) gene was discovered through genome-wide association studies and is a promising candidate for type 2 diabetes mellitus (T2DM), which is one of the risk factors for obesity and other complications. T2DM has been identified as a heterogeneous and multifactorial disease characterized by insulin resistance and secretion.

Aim

The aim of this study was to investigate the rs7932837 polymorphism in the HHEX gene in overweight patients diagnosed with T2DM in the Saudi Population.

Methods

In this case-control study, one hundred T2DM cases and 100 controls were selected based on inclusion and exclusion criteria. Genotyping was performed with polymerase chair reaction-restriction fragment length polymorphism analysis and statistical analysis was performed between T2DM cases and controls for clinical characteristics, genotype and allele frequencies and multiple logistic regression analysis.

Results

In this study, T2DM cases were compared with healthy control subjects. Clinical characteristic analysis revealed the statistical analysis between age, weight, BMI, FBG, HDL-c, TC, TG and family history (p < 0.05). HWE analysis was in the accordance (p < 0.05). The rs7932837 polymorphism in the recessive model showed the positive association (AA + AG vs AA: 2.22 [1.25–3.96] & p = 0.006) and none of the genotypes or alleles were in the statistical association. Multiple logistic regression analysis revealed positive association with age, BMI and FBG (p < 0.05).

Conclusion

This study concludes as rs7932837 polymorphism in the HHEX gene showed positive association with recessive model and future studies recommend to carry out with large number of sample size with additional polymorphisms in HHEX gene.

Insulin-like Growth Factor 2 mRNA-Binding Protein 2-a Potential Link Between Type 2 Diabetes Mellitus and Cancer

CONTEXT

Type 2 diabetes mellitus (T2DM) and cancer share a variety of risk factors and pathophysiological features. It is becoming increasingly accepted that the 2 diseases are related, and that T2DM increases the risk of certain malignancies.

OBJECTIVE

This review summarizes recent advancements in the elucidation of functions of insulin-like growth factor 2 (IGF-2) messenger RNA (mRNA)-binding protein 2 (IGF2BP2) in T2DM and cancer.

METHODS

A PubMed review of the literature was conducted, and search terms included IGF2BP2, IMP2, or p62 in combination with cancer or T2DM. Additional sources were identified through manual searches of reference lists. The increased risk of multiple malignancies and cancer-associated mortality in patients with T2DM is believed to be driven by insulin resistance, hyperinsulinemia, hyperglycemia, chronic inflammation, and dysregulation of adipokines and sex hormones. Furthermore, IGF-2 is oncogenic, and its loss-of-function splice variant is protective against T2DM, which highlights the pivotal role of this growth factor in the pathogenesis of these 2 diseases. IGF-2 mRNA-binding proteins, particularly IGF2BP2, are also involved in T2DM and cancer, and single-nucleotide variations (formerly single-nucleotide polymorphisms) of IGF2BP2 are associated with both diseases. Deletion of the IGF2BP2 gene in mice improves their glucose tolerance and insulin sensitivity, and mice with transgenic p62, a splice variant of IGF2BP2, are prone to diet-induced fatty liver disease and hepatocellular carcinoma, suggesting the biological significance of IGF2BP2 in T2DM and cancer.

CONCLUSION

Accumulating evidence has revealed that IGF2BP2 mediates the pathogenesis of T2DM and cancer by regulating glucose metabolism, insulin sensitivity, and tumorigenesis. This review provides insight into the potential involvement of this RNA binding protein in the link between T2DM and cancer.

The fat mass and obesity-associated (FTO) gene allele rs9939609 and glucose tolerance, hepatic and total insulin sensitivity, in adults with obesity

The objective of the study was to assess associations of the rs9939609 FTO allele to glucose tolerance, hepatic and total insulin sensitivity (IS) in individuals with obesity. From a low-dose hyperinsulinemic euglycemic clamp with glucose-tracer, hepatic IS was assessed by rates of basal and suppressed glucose appearance (Ra), a measure of endogenous glucose production (EGP), and the hepatic insulin resistance index (HIR). Total IS was assessed by rates of glucose infusion (GIR), disappearance (Rd), and metabolic clearance (MCR). From a meal test we assessed IS by the Matsuda index and glucose tolerance by glucose and insulin measurements in the fasted state and postprandially for 2.5 h. The meal test was performed in 97 healthy individuals with BMI ≥35 in similar-sized risk-allele groups (n = 32 T/T, 31 A/T, and 34 A/A), and 79 of them performed the clamp. We analyzed outcomes separately for males and females, and adjusted glucose Ra, Rd, MCR, GIR, and HIR for fat mass. We did not find genotype effects on EGP. Among males, genotype A/A was associated with a significantly lower glucose Rd, MCR, and Matsuda index score relative to genotype T/T. Glucose tolerance was significantly lower in males with genotype A/T vs. T/T and A/A. For females, there were no genotype effects on hepatic or total IS, or on glucose tolerance. Independently of genotypes, females displayed a significantly better hepatic and total IS, and better glucose tolerance than males. We conclude that in subjects with similar obesity we did not register any FTO risk-allele effect on hepatic IS. A FTO risk-allele effect on total IS was registered in males only, findings which need to be reproduced in further studies. Results confirm marked differences in IS between the biological sexes and extend present knowledge by demonstrating a lower endogenous glucose production in females vs. males in uniformly obese individuals.

Potential Role of Insulin Growth-Factor-Binding Protein 2 as Therapeutic Target for Obesity-Related Insulin Resistance

Evidence from observational and in vitro studies suggests that insulin growth-factor-binding protein type 2 (IGFBP2) is a promising protein in non-communicable diseases, such as obesity, insulin resistance, metabolic syndrome, or type 2 diabetes. Accordingly, great efforts have been carried out to explore the role of IGFBP2 in obesity state and insulin-related diseases, which it is typically found decreased. However, the physiological pathways have not been explored yet, and the relevance of IGFBP2 as an important pathway integrator of metabolic disorders is still unknown. Here, we review and discuss the molecular structure of IGFBP2 as the first element of regulating the expression of IGFBP2. We highlight an update of the association between low serum IGFBP2 and an increased risk of obesity, type 2 diabetes, metabolic syndrome, and low insulin sensitivity. We hypothesize mechanisms of IGFBP2 on the development of obesity and insulin resistance in an insulin-independent manner, which meant that could be evaluated as a therapeutic target. Finally, we cover the most interesting lifestyle modifications that regulate IGFBP2, since lifestyle factors (diet and/or physical activity) are associated with important variations in serum IGFBP2.

Evidence of association between single-nucleotide polymorphisms in lipid metabolism-related genes and type 2 diabetes mellitus in a Chinese population

Background: Type 2 diabetes mellitus (T2DM) is a complex chronic metabolic disorder triggered by insulin resistance in peripheral tissues. Evidence has shown that lipid metabolism and related genetic factors lead to insulin resistance. Hence, it is meaningful to investigate the association between single-nucleotide polymorphisms (SNPs) in lipid metabolism-related genes and T2DM. Methods: A total of 1,194 subjects with T2DM and 1,274 Non-diabetic subjects (NDM) were enrolled. Five SNPs in three genes (rs864745 in JAZF1, rs35767 in IGF1, and rs4376068, rs4402960, and rs6769511 in IGF2BP2) that contribute to insulin resistance involving lipid metabolism were genotyped using the MassArray method in a Chinese population. Results: The allele and genotypes of rs6769511 in IGF2BP2 were associated with T2DM (P=0.009 and P=0.002, respectively). In inheritance model analysis, compared with the T/T-C/T genotype, the C/C genotype of rs6769511 in IGF2BP2 was a risk factor for the development of T2DM (P<0.001, odds ratio [OR] =1.76; 95% confidence interval [CI]: 1.29-2.42). Haplotype analysis revealed associations of the rs4376068-rs4402960-rs6769511 haplotypes in IGF2BP2 with the development of T2DM (P=0.015). Additionally, rs4376068C-rs4402960T-rs6769511C was a risk haplotype for T2DM (OR=1.179; 95% CI: 1.033-1.346). Conclusion: The rs6769511 in IGF2BP2 was associated with T2DM susceptibility, and the rs4376068-rs4402960-rs6769511 haplotypes in IGF2BP2 was associated with the development of T2DM in a Chinese population.

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.

Relationship between IGF2BP2 and IGFBP3 polymorphisms and susceptibility to non-small-cell lung cancer: a case-control study in Eastern Chinese Han population

Background

IGF2BP2 and IGFBP3 polymorphisms may be associated with cancer risk.

Methods

With an aim to determine the association of variations in IGF2BP2 and IGFBP3 genes with risk of non-small-cell lung cancer (NSCLC), IGF2BP2 rs1470579 A>C, rs4402960 G>T and IGFBP3 rs2270628 C>T, rs3110697 G>A, and rs6953668 G>A polymorphisms were selected and genotyped in 521 NSCLC patients and 1,030 controls.

Results

We found that there was no difference in IGF2BP2 and IGFBP3 genotype distribution among the NSCLC patients and controls. The stratified analyses suggested that IGF2BP2 rs1470579 A>C polymorphism decreased the risk of NSCLC in some subgroups (female subgroup: CC vs AA: adjusted P=0.032 and CC vs AC/AA: adjusted P=0.028; <60 years subgroup: CC vs AA: adjusted P=0.012 and CC vs AC/AA: adjusted P=0.013; and never drinking subgroup: CC vs AA: adjusted P=0.046 and CC vs AC/AA: adjusted P=0.031). The stratified analyses also found that IGF2BP2 rs4402960 G>T polymorphism decreased the risk of NSCLC in some subgroups (female subgroup: TT vs GG: adjusted P=0.031 and TT vs GT/GG: adjusted P=0.026; <60 subgroup: TT vs GG: adjusted P=0.037 and TT vs GT/GG: adjusted P=0.038; and never drinking subgroup: TT vs GT/GG: adjusted P=0.046). Haplotype analysis indicated A_rs1470579C_rs2270628G_rs3110697G_rs4402960A_rs6953668 haplotype decreased susceptibility of NSCLC (P=0.007).

Conclusion

Our study suggests that IGF2BP2 rs1470579 A>C, rs4402960 G>T single-nucleotide polymorphisms are candidates for decreased susceptibility to NSCLC among female, <60 years, and never drinking subgroups. In the future, more case–control studies with functional analysis are needed to confirm these preliminary findings.

CDKN2A/B T2D Genome-Wide Association Study Risk SNPs Impact Locus Gene Expression and Proliferation in Human Islets

Genome-wide association studies link the CDKN2A/B locus with type 2 diabetes (T2D) risk, but mechanisms increasing risk remain unknown. The CDKN2A/B locus encodes cell cycle inhibitors p14, p15, and p16; MTAP; and ANRIL, a long noncoding RNA. The goal of this study was to determine whether CDKN2A/B T2D risk SNPs impact locus gene expression, insulin secretion, or β-cell proliferation in human islets. Islets from donors without diabetes (n = 95) were tested for SNP genotype (rs10811661, rs2383208, rs564398, and rs10757283), gene expression (p14, p15, p16, MTAP, ANRIL, PCNA, KI67, and CCND2), insulin secretion (n = 61), and β-cell proliferation (n = 47). Intriguingly, locus genes were coregulated in islets in two physically overlapping cassettes: p14-p16-ANRIL, which increased with age, and MTAP-p15, which did not. Risk alleles at rs10811661 and rs2383208 were differentially associated with expression of ANRIL, but not p14, p15, p16, or MTAP, in age-dependent fashion, such that younger homozygous risk donors had higher ANRIL expression, equivalent to older donor levels. We identified several risk SNP combinations that may impact locus gene expression, suggesting possible mechanisms by which SNPs impact locus biology. Risk allele carriers at ANRIL coding SNP rs564398 had reduced β-cell proliferation index. In conclusion, CDKN2A/B locus SNPs may impact T2D risk by modulating islet gene expression and β-cell proliferation.

Maturity-onset diabetes of the young as a model for elucidating the multifactorial origin of type 2 diabetes mellitus

Maturity‐onset diabetes of the young (MODY) is a form of diabetes classically characterized as having autosomal dominant inheritance, onset before the age of 25 years in at least one family member and partly preserved pancreatic β‐cell function. The 14 responsible genes are reported to be MODY type 1~14, of which MODY 2 and 3 might be the most common forms. Although MODY is currently classified as diabetes of a single gene defect, it has become clear that mutations in rare MODYs, such as MODY 5 and MODY 6, have small mutagenic effects and low penetrance. In addition, as there are differences in the clinical phenotypes caused by the same mutation even in the same family, other phenotypic modifying factors are thought to exist; MODY could well have characteristics of type 2 diabetes mellitus, which is of multifactorial origin. Here, we outline the effects of genetic and environmental factors on the known phenotypes of MODY, focusing mainly on the examples of MODY 5 and 6, which have low penetrance, as suggestive models for elucidating the multifactorial origin of type 2 diabetes mellitus.

The relationship between IGF2BP2 and PPARG polymorphisms and susceptibility to esophageal squamous-cell carcinomas in the eastern Chinese Han population

The aim of this case–control study was to assess whether PPARG and IGF2BP2 polymorphisms confer susceptibility to esophageal squamous-cell carcinoma (ESCC). A total of 507 patients pathologically confirmed for ESCC and 1,496 age-, sex-, and residence-matched healthy individuals were enrolled. The PPARG rs1801282 C>G and rs3856806 C>T and IGF2BP2 rs1470579 A>C and rs4402960 G>T polymorphisms were selected and genotyped by SNPscan genotyping assays. Multivariable logistic analysis suggested that the PPARG rs3856806 C>T polymorphism might increase the risk of ESCC. In different stratified analyses, there were significant associations between PPARG rs3856806 C>T and risk of ESCC in female, never-smoking, drinking, and never-drinking subgroups. In addition, we also found that PPARG rs1801282 C>G increased ESCC risk in the never-smoking subgroup. There was significant difference in C_rs1470579G_rs4402960C_rs1801282C_rs3856806-haplotype distribution among ESCC cases and control subjects. In conclusion, our findings highlight that PPARG rs1801282 C>G and rs3856806 C>T polymorphisms are candidates for susceptibility to ESCC in the eastern Chinese Han population. The C_rs1470579G_rs4402960C_rs1801282C_rs3856806 haplotype is associated with susceptibility to ESCC.

Association of polymorphic markers of genes FTO, KCNJ11, CDKAL1, SLC30A8, and CDKN2B with type 2 diabetes mellitus in the Russian population

Background

The association of type 2 diabetes mellitus (T2DM) with the KCNJ11, CDKAL1, SLC30A8, CDKN2B, and FTO genes in the Russian population has not been well studied. In this study, we analysed the population frequencies of polymorphic markers of these genes.

Methods

The study included 862 patients with T2DM and 443 control subjects of Russian origin. All subjects were genotyped for 10 single nucleotide polymorphisms (SNPs) of the genes using real-time PCR (TaqMan assays). HOMA-IR and HOMA-β were used to measure insulin resistance and β-cell secretory function, respectively.

Results

The analysis of the frequency distribution of polymorphic markers for genes KCNJ11, CDKAL1, SLC30A8 and CDKN2B showed statistically significant associations with T2DM in the Russian population. The association between the FTO gene and T2DM was not statistically significant. The polymorphic markers rs5219 of the KCNJ11 gene, rs13266634 of the SLC30A8 gene, rs10811661 of the CDKN2B gene and rs9465871, rs7756992 and rs10946398 of the CDKAL1 gene showed a significant association with impaired glucose metabolism or impaired β-cell function.

Conclusion

In the Russian population, genes, which affect insulin synthesis and secretion in the β-cells of the pancreas, play a central role in the development of T2DM.

FTO Genotype and Type 2 Diabetes Mellitus: Spatial Analysis and Meta-Analysis of 62 Case-Control Studies from Different Regions

Type 2 diabetes mellitus (T2DM) is a global health problem that results from the interaction of environmental factors with genetic variants. Although a number of studies have suggested that genetic polymorphisms in the fat mass and obesity-associated (FTO) gene are associated with T2DM risk, the results have been inconsistent. To investigate whether FTO polymorphisms associate with T2DM risk and whether this association is region-related, we performed this spatial analysis and meta-analysis. More than 60,000 T2DM patients and 90,000 controls from 62 case-control studies were included in this study. Odds ratios (ORs), 95% confidence intervals (CIs) and Moran's I statistic were used to estimate the association between FTO rs9939609, rs8050136, rs1421085, and rs17817499, and T2DM risk in different regions. rs9939609 (OR = 1.15, 95% CI 1.11-1.19) and rs8050136 (OR = 1.14, 95% CI 1.10-1.18) conferred a predisposition to T2DM. After adjustment for body mass index (BMI), the association remained statistically significant for rs9939609 (OR = 1.11, 95% CI 1.05-1.17) and rs8050136 (OR = 1.08, 95% CI 1.03-1.12). In the subgroup analysis of rs9939609 and rs8050136, similar results were observed in East Asia, while no association was found in North America. In South Asia, an association for rs9939609 was revealed but not for rs8050136. In addition, no relationship was found with rs1421085 or rs17817499 regardless of adjustment for BMI. Moran's I statistic showed that significant positive spatial autocorrelations existed in rs9939609 and rs8050136. Studies on rs9939609 and rs8050136 focused on East Asia and South Asia, whereas studies on rs1421085 and rs17817499 were distributed in North America and North Africa. Our data suggest that the associations between FTO rs9939609, rs8050136 and T2DM are region-related, and the two single-nucleotide polymorphisms contribute to an increased risk of T2DM. Future studies should investigate this issue in more regions.

Replication of genome-wide association signals in Asian Indians with early-onset type 2 diabetes

AIMS

To evaluate the association of 87 genetic variants previously associated with type 2 diabetes mellitus (T2DM) in genome-wide association studies of populations of European ancestry in an Asian Indian population with early-onset type 2 diabetes mellitus (EOT2DM).

METHODS

The study groups comprised of 877 type 2 diabetes individuals, 436 individuals with EOT2DM (age at diagnosis below 35 years), 441 individuals with older T2DM (diagnosis at 35 years or greater) and controls with normal glucose tolerance (NGT) (n = 400 younger than 35 years; n = 438 older than 35 years). The participants were genotyped for 87 SNPs from 44 genes and 27 intergenic loci. Associations were tested using logistic regression.

RESULTS

All the variants in TCF7L2 and CDKN2A/2B showed study-wide significance (p < 1.4 × 10^-4) with T2DM, but only rs7903146, rs12243326, rs12255372 of TCF7L2 and rs7020996 of CDKN2A/2B showed study-wide significance (p < 1.4 × 10^-4) with EOT2DM in this population. In addition, an intergenic SNP on chromosome 1 (rs10493685) was also shown to be study-wide significant (p = 7.1 × 10^-6). Several additional SNPs previously associated with T2DM reached borderline significance in this study, but may have been limited by relatively low sample numbers. Various other SNPs of T2DM were not associated with EOT2DM.

CONCLUSIONS

Some of the variants in TCF7L2 and CDKN2A/2B associated with T2DM are associated with EOT2DM as well. An intergenic SNP on chromosome 1p31 showed association only with early-onset T2DM in this Asian Indian population. The lack of association with many other SNPs of T2DM may be a reflection of the lack of power of the study, sample size, differences in the frequencies of genetic polymorphisms in different ethnic groups, effect sizes, as well as ancestral differences in pattern of LD between the genetic variants involved in early- and late-onset T2DM.

FTO Gene Polymorphism Is Associated with Type 2 Diabetes through Its Effect on Increasing the Maximum BMI in Japanese Men

Aim

Several studies have demonstrated that polymorphisms within the fat-mass and obesity-associated gene (FTO) are associated with type 2 diabetes (T2D). However, whether the effects of the FTO locus on T2D susceptibility are independent of fat-mass increases remains controversial. To investigate this issue, we examined the association of FTO variants with T2D and various aspects of BMI history during adult life in a Japanese population.

Methods

We genotyped SNPs within FTO (rs1121980 and rs1558902) in 760 Japanese patients with T2D who had reached a lifetime maximum BMI (BMI_max) before or at the time of diagnosis and 693 control individuals with information regarding their BMI_max.

Results

The BMI_max showed the strongest association with T2D risk among the BMIs evaluated in this study. In the sex-combined analysis, FTO SNPs were not associated with any of the BMI variables or with T2D, but in sex-stratified analyses, both SNPs were significantly associated with the BMI_max and rs1558902 was associated with T2D in men. The association of the SNPs with T2D remained significant after adjustments for the current BMI and age, whereas the T2D association of the SNP was no longer significant after adjustments for BMI_max and age.

Conclusions

These results suggest that the effects of FTO polymorphisms on T2D susceptibility in Japanese men are mediated through their effect on increasing the BMI_max before or at the time of diagnosis.

Association of SLC30A8 gene polymorphism with type 2 diabetes, evidence from 46 studies: a meta-analysis

The solute carrier family 30 member 8 (SLC30A8) gene may be involved in the development of type 2 diabetes mellitus (T2DM) through disrupting β-cell function. The aim of this study was to assess the association between SLC30A8 rs13266634 polymorphism and susceptibility to T2DM. We searched all reports regarding the association between SLC30A8 rs13266634 polymorphism and T2DM risk through Pubmed, Embase, and the Cochrane Library for English language reports and Chongqing VIP database, Wanfang data, CBMDisc, and CNKI for Chinese language studies. Allelic and genotype comparisons between cases and controls were evaluated, and odds ratios with 95 % confidence intervals were used to assess the strength of their association. A random effects model was selected. Publication bias was estimated using Begg's test. Forty-six studies were included in the analysis with a total of 71,890 cases and 96,753 controls. This meta-analysis suggests that SLC30A8 (rs13266634) polymorphism was associated with T2DM risk. Although previous meta-analyses have shown that this association was only found in Asian and European groups, and not in African populations, our analysis revealed the deleterious effect of SLC30A8 rs13266634 on T2DM in an African population when stratified by ethnicity under additive model even with a small number of studies.

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.

Candidate gene analysis supports a role for polymorphisms at TCF7L2 as risk factors for type 2 diabetes in Sudan

Background

Genetic susceptibility to type 2 diabetes (T2D) is multifactorial. A growing number of genes have been identified as risk factors for T2D across multiple ethnicities in trans-ancestry meta-analysis of large-scale genome-wide association studies. Few studies have looked at these genes in Sub-Saharan African populations. This study was undertaken to look for associations between T2D and single nucleotide polymorphisms (SNPs) in a number of the top candidate genes in a selected Sudanese population.

Methods

A total 240 T2D cases and 128 unrelated healthy control subjects were included in this study. Age, sex, weight and height were recorded, blood pressure and biochemical profiles of glucose and lipids were analysed. Single nucleotide polymorphism (SNP) genotyping was performed using the Sequenom MassARRAY® system. Fourteen SNPs were selected across 7 genes: CAPN10 (rs2975760 and rs5030952), PPARG (rs17036314 and rs1801282), IGF2BP2 (rs4402960 and rs1470579), CDKAL1 (rs9465871), HHEX (rs1111875), TCF7L2 (rs7903146, rs11196205 and rs12255372), and KCNJ11 (rs5215, rs1800467 and rs5219). Allelic and haplotype association analyses were performed under additive models in PLINK. P ≤ 0.007 (=0.05/7 genes) was the P-value required to achieve correction for multiple testing.

Results

A significant genetic association between the SNPs rs7903146 (odds ratio 1.69, 95 % confidence interval 1.21–2.38, P = 0.002) and rs12255372 (odds ratio 1.70, 95 % confidence interval 1.20–2.41, P = 0.003) at TCF7L2 and T2D was found in Sudanese population. These associations were retained after adjusting for age, sex and BMI (e.g. rs7903146: odds ratio 1.70, P_{adj:age/sex/BMI} = 0.005). The strongest haplotype association (odds ratio 2.24; P_{adj:age/sex/BMI} = 0.0003) comprised the two point haplotype T_C across rs7903146 and rs11196205. Stepwise logistic regression demonstrated that SNP rs7903146 added significant main effects to rs11196205 or rs12255372, whereas the reverse was not true, indicating that the main effect for association with T2D in this population is most strongly tagged by SNP rs7903146. Adjusted analyses also provided support for protection from T2D associated with minor alleles at SNPs rs2975760 at CAPN10 (odds ratio 0.44, 95 % confidence interval 0.20-0.97, P_{adj:age/sex/BMI} = 0.042) and rs1111876 at HHEX (odds ratio 0.60, 95 % confidence interval 0.39- 0.93, P_{adj:age/sex/BMI} = 0.022).

Conclusions

Multiethnic associations between T2D and SNPs at TCF7L2, CAPN10 and HHEX extend to Sub-Saharan Africa, specifically Sudan.

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.

Association between SLC30A8 rs13266634 Polymorphism and Type 2 Diabetes Risk: A Meta-Analysis

BACKGROUND

Accumulating but inconsistent data about the role of rs13266634 variant of SLC30A8 in type 2 diabetes have been reported, partly due to small sample sizes and non-identical ethnicity.

MATERIAL AND METHODS

We searched PubMed and Cochrane Library to identify eligible studies and extract data of baseline characteristics, genotype count, odds ratio (OR), and 95% confidence interval (CI). Both adjusted OR with 95% CI and genotype counts were employed to assess the association. Genotype data were further pooled to provide estimates under different genetic models and the most appropriate model was determined. Sensitivity and cumulative analysis were conducted to assure the strength of results.

RESULTS

Fifty-five datasets of 39 studies (including 38 of 24 with genotype count) were included. Significant associations were found in allelic contrasts using adjusted ORs and raw genotype count, respectively, overall in Asian and European populations (overall: OR=1.147/1.157, 95% CI 1.114-1.181/1.135-1.180; Asian: OR=1.186/1.165, 95% CI 1.150-1.222/1.132-1.198; European: OR=1.100/1.151, 95% CI 1.049-1.153/1.120-1.183; All p=0.00), but not in African populations (African: OR=1.255/1.111, 95% CI 0.964-1.634/0.908-1.360, p=0.091/0.305). Further analysis with genotype count under different genetic models all showed that individuals with CC genotype had 33.0% and 16.5% higher risk of type 2 diabetes than those carrying TT and CT genotypes, respectively, under the most likely codominant model. Cumulative analysis indicated gradually improved precision of estimation after studies accumulated.

CONCLUSIONS

Our results suggest that rs13266634 may be an important genetic factor of type 2 diabetes risk among Asian and European but not African populations.

Can data science inform environmental justice and community risk screening for type 2 diabetes?

Background

Having the ability to scan the entire country for potential “hotspots” with increased risk of developing chronic diseases due to various environmental, demographic, and genetic susceptibility factors may inform risk management decisions and enable better environmental public health policies.

Objectives

Develop an approach for community-level risk screening focused on identifying potential genetic susceptibility hotpots.

Methods

Our approach combines analyses of phenotype-genotype data, genetic prevalence of single nucleotide polymorphisms, and census/geographic information to estimate census tract-level population attributable risks among various ethnicities and total population for the state of California.

Results

We estimate that the rs13266634 single nucleotide polymorphism, a type 2 diabetes susceptibility genotype, has a genetic prevalence of 56.3%, 47.4% and 37.0% in Mexican Mestizo, Caucasian, and Asian populations. Looking at the top quintile for total population attributable risk, 16 California counties have greater than 25% of their population living in hotspots of genetic susceptibility for developing type 2 diabetes due to this single genotypic susceptibility factor.

Conclusions

This study identified counties in California where large portions of the population may bear additional type 2 diabetes risk due to increased genetic prevalence of a susceptibility genotype. This type of screening can easily be extended to include information on environmental contaminants of interest and other related diseases, and potentially enables the rapid identification of potential environmental justice communities. Other potential uses of this approach include problem formulation in support of risk assessments, land use planning, and prioritization of site cleanup and remediation actions.

Significance of a common variant in the CDKAL1 gene with susceptibility to type 2 diabetes mellitus in Iranian population

Background:

Type 2 diabetes mellitus (T2DM) is a worldwide problem that threatens the public health and economies of all countries. A multifactorial etiology and interaction between environmental factors and genetic components are responsible for triggering and progression of T2DM. Recently, rs7754840 single nucleotide polymorphism (SNP) in the CDKAL1 gene was reported to be associated with T2DM in various populations. However, due to inconsistent results in various populations about the association of rs7754840 with T2DM, and lack of information in the Iranian population, we have evaluated its association with T2DM in a subset of the Iranian population from Isfahan province, central part of Iran.

Materials and Methods:

The study included 140 patients and 140 controls selected based on the World Health Organization guidelines. Genomic DNA was extracted from blood samples and the rs7754840 SNP was genotyped using a polymerase chain reaction-restriction fragment length polymorphism assay with specific primers and restriction enzyme (Ac1I).

Results:

The frequency of the C allele in the cases was higher than that in the controls (72.9% vs. 65%; P = 0.045). Using logistic regression analysis, we found a significant risk association of CC genotype with T2DM susceptibility (OR = 2.319, 95% CI = 1.436-3.744, P = 0.001). Furthermore, compared with the CC genotype, individuals with the GC genotype had a lower risk (protective association) of developing T2DM (OR = 0.332, 95% CI = 0.202-0.547, P < 0.001).

Conclusions:

We confirmed that there is a significant risk association between rs7754840 polymorphism and development of T2DM in a subset of the Iranian population from Isfahan province.

Contribution of CDKAL1 rs7756992 and IGF2BP2 rs4402960 polymorphisms in type 2 diabetes, diabetic complications, obesity risk and hypertension in the Tunisian population

BACKGROUND

The insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) and the cyclin-dependent kinase 5 regulatory subunit-associated protein 1-like 1 (CDKAL1) identified through genome-wide association (GWA) studies have been shown to be associated with Type 2 diabetes in various ethnic groups. In this study, we investigated the association of the rs7756992 of CDKAL1 and the rs4402960 of IGF2BP2 with Type 2 diabetes, diabetic complications (nephropathy, retinopathy and cardiovascular disease), obesity and hypertension in a Tunisian population.

METHODS

A case-control association study including 200 Type 2 diabetes Tunisian patients (World Health Organization criteria) and 208 controls (age ≥40; fasting plasma glucose <6.1 mmol/L; without first degree family history of diabetes) has been performed. Other parameters such as diabetic nephropathy, diabetic retinopathy, cardiovascular disease, overweight/obesity and hypertension have been also collected. Genotyping was performed using TaqMan technology.

RESULTS

A significant association between the rs4402960 and Type 2 diabetes (OR = 1.86, 95% CI = 1.34-2.58, P < 10(-4) ) has been found. Overweight/obese subjects bearing the T-allele have an increased risk to develop Type 2 diabetes (OR = 2.06, 95% CI = 1.40-3.03, P < 10(-4) ). Furthermore, the rs7756992 was found to be associated with the reduced risk of diabetic nephropathy in patients with diabetes (OR = 0.44, 95% CI = 0.27-0.73, P = 0.001).

CONCLUSIONS

The present study confirms that the rs4402960 of IGF2BP2 gene is a strong candidate for Type 2 diabetes susceptibility and overweight/obesity risk in the Tunisian population. Interestingly, our data suggest that the rs7756992 of CDKAL1 gene have a protective effect against diabetic nephropathy.

The Chromosome 9p21 CVD- and T2D-Associated Regions in a Norwegian Population (The HUNT2 Survey)

Background. Two adjacent regions upstream CDKN2B on chromosome 9p21 have been associated with type 2 diabetes (T2D) and progression of cardiovascular disease (CVD). The precise location and number of risk variants have not been completely delineated and a possible synergistic relationship between the adjacent regions is not fully addressed. By a population based cross-sectional case-control design, we genotyped 18 SNPs upstream of CDKN2B tagging 138 kb in and around two LD-blocks associated with CVD and T2D and investigated associations with T2D, angina pectoris (AP), myocardial infarction (MI), coronary heart disease (CHD; AP or AMI), and stroke using 5,564 subjects from HUNT2. Results. Single point and haplotype analysis showed evidence for only one common T2D risk haplotype (rs10757282∣rs10811661: OR = 1.19, P = 2.0 × 10(-3)) in the region. We confirmed the strong association between SNPs in the 60 kb CVD region with AP, MI, and CHD (P < 0.01). Conditioning on the lead SNPs in the region, we observed two suggestive independent single SNP association signals for MI, rs2065501  (P = 0.03) and rs3217986  (P = 0.04). Conclusions. We confirmed the association of known variants within the 9p21 interval with T2D and CHD. Our results further suggest that additional CHD susceptibility variants exist in this region.

T2DM GWAS in the Lebanese population confirms the role of TCF7L2 and CDKAL1 in disease susceptibility

Genome-wide association studies (GWAS) of multiple populations with distinctive genetic and lifestyle backgrounds are crucial to the understanding of Type 2 Diabetes Mellitus (T2DM) pathophysiology. We report a GWAS on the genetic basis of T2DM in a 3,286 Lebanese participants. More than 5,000,000 SNPs were directly genotyped or imputed using the 1000 Genomes Project reference panels. We identify genome-wide significant variants in two loci CDKAL1 and TCF7L2, independent of sex, age and BMI, with leading variants rs7766070 (OR = 1.39, P = 4.77 × 10(-9)) and rs34872471 (OR = 1.35, P = 1.01 × 10(-8)) respectively. The current study is the first GWAS to find genomic regions implicated in T2DM in the Lebanese population. The results support a central role of CDKAL1 and TCF7L2 in T2DM susceptibility in Southwest Asian populations and provide a plausible component for understanding molecular mechanisms involved in the disease.

The effect of IGF2BP2 gene polymorphisms on pioglitazone response in Chinese type 2 diabetes patients

BACKGROUND

Genome-wide association studies identified that insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) genetic polymorphisms are related to type 2 diabetes mellitus (T2DM) in several populations. This study aimed to investigate whether the IGF2BP2 gene rs1470579 and rs4402960 polymorphisms were associated with T2DM and pioglitazone efficacy in Chinese T2DM patients.

METHODS

A total of 281 T2DM patients and 111 healthy volunteers were enrolled to identify the IGF2BP2 gene rs1470579 and rs4402960 polymorphisms; 86 patients were randomly selected and given a 12-week pioglitazone treatment (30 mg/day). Fasting plasma glucose, postprandial plasma glucose (PPG), glycated hemoglobin, serum triglycerides (TG), total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol (HDL-C) were determined before and after pioglitazone treatment.

RESULTS

The results showed that the IGF2BP2 gene rs1470579 and rs4402960 polymorphisms were associated with T2DM in a Chinese population (OR = 2.002, 95% CI 1.170-3.426, p < 0.05; OR = 1.879, 95% CI 1.110-3.182, p < 0.05). The effect of pioglitazone on PPG (p < 0.05), TG (p < 0.01) and HDL-C (p < 0.05) was lower in patients with the rs1470579 AC+CC genotypes than in AA genotype carriers. Its effect on PPG level was also lower in patients with the GT+TT genotypes of rs4402960 than in patients with the GG genotype (p < 0.05).

CONCLUSIONS

The IGF2BP2 gene rs1470579 and rs4402960 polymorphisms were associated with T2DM and therapeutic efficacy of pioglitazone in this Chinese population.

Association of genetic variants of the incretin-related genes with quantitative traits and occurrence of type 2 diabetes in Japanese

Background

None of the high frequency variants of the incretin-related genes has been found by genome-wide association study (GWAS) for association with occurrence of type 2 diabetes in Japanese. However, low frequency and rare and/or high frequency variants affecting glucose metabolic traits remain to be investigated.

Method

We screened all exons of the incretin-related genes (GCG, GLP1R, DPP4, PCSK1, GIP, and GIPR) in 96 patients with type 2 diabetes and investigated for association of genetic variants of these genes with quantitative metabolic traits upon test meal with 38 young healthy volunteers and with the occurrence of type 2 diabetes in Japanese subjects comprising 1303 patients with type 2 diabetes and 1014 controls.

Result

Two mutations of GIPR, p.Thr3Alafsx21 and Arg183Gln, were found only in patients with type 2 diabetes, and both of them were treated with insulin. Of ten tagSNPs, we found that risk allele C of SNP393 (rs6235) of PCSK1 was nominally associated with higher fasting insulin and HOMA-R (P = 0.034 and P = 0.030), but not with proinsulin level, incretin level or BMI. The variant showed significant association with occurrence of type 2 diabetes after adjustment for age, sex, and BMI (P = 0.0043).

Conclusion

Rare variants of GIPR may contribute to the development of type 2 diabetes, possibly through insulin secretory defects. Furthermore, the genetic variant of PCSK1 might influence glucose homeostasis by altered insulin resistance independently of BMI, incretin level or proinsulin conversion, and may be associated with the occurrence of type 2 diabetes in Japanese.

Association analysis of IGF2BP2, KCNJ11, and CDKAL1 polymorphisms with type 2 diabetes mellitus in a Moroccan population: a case-control study and meta-analysis

Associations with type 2 diabetes mellitus have been identified for variants CDKAL1 rs7756992, KCNJ11 rs5219, and IGF2BP2 rs4402960 in different populations. In a case-control study of 250 unrelated Moroccan diabetic patients and 250 healthy controls, we used TaqMan allelic discrimination assays to genotype the three SNPs and meta-analysis to investigate the association between the polymorphisms and diabetes in Arab populations. The results showed a significant diabetes association only with the variant rs4402960 of the IGF2BP2 gene under additive 2 (GG vs. TT; p = 0.009) and recessive (TT vs. GG+GT; p = 0.003) models. Meta-analysis indicated significant association between the IGF2BP2 rs4402960 and CDKAL1 rs7756992 polymorphisms and increased risk of diabetes in Arab populations. According to our results, the case-control study and meta-analysis revealed a significant association between the IGF2BP2 rs4402960 variant and type 2 diabetes in Moroccan and Arab populations.

Maternal high-fat diet induces insulin resistance and deterioration of pancreatic β-cell function in adult offspring with sex differences in mice

Intrauterine environment may influence the health of postnatal offspring. There have been many studies on the effects of maternal high-fat diet (HFD) on diabetes and glucose metabolism in offspring. Here, we investigated the effects in male and female offspring. C57/BL6J mice were bred and fed either control diet (CD) or HFD from conception to weaning, and offspring were fed CD or HFD from 6 to 20 wk. At 20 wk, maternal HFD induced glucose intolerance and insulin resistance in offspring. Additionally, liver triacylglycerol content, adipose tissue mass, and inflammation increased in maternal HFD. In contrast, extending previous observations, insulin secretion at glucose tolerance test, islet area, insulin content, and PDX-1 mRNA levels in isolated islets were lower in maternal HFD in males, whereas they were higher in females. Oxidative stress in islets increased in maternal HFD in males, whereas there were no differences in females. Plasma estradiol levels were lower in males than in females and decreased in offspring fed HFD and also decreased by maternal HFD, suggesting that females may be protected from insulin deficiency by inhibiting oxidative stress. In conclusion, maternal HFD induced insulin resistance and deterioration of pancreatic β-cell function, with marked sex differences in adult offspring accompanied by adipose tissue inflammation and liver steatosis. Additionally, our results demonstrate that potential mechanisms underlying sex differences in pancreatic β-cell function may be related partially to increases in oxidative stress in male islets and decreased plasma estradiol levels in males.

High cardiorespiratory fitness can reduce glycated hemoglobin levels regardless of polygenic risk for Type 2 diabetes mellitus in nondiabetic Japanese men

High cardiorespiratory fitness (CRF) is associated with a reduced risk of Type 2 diabetes mellitus (T2DM) and improved β-cell function; genetic factors also determine these risks. This cross-sectional study investigated whether CRF modifies the association of polygenic risk of T2DM with glucose metabolism in nondiabetic Japanese men. Fasting plasma glucose, insulin, and glycated hemoglobin (HbA1c) levels were measured in 174 Japanese men (age: 20-79 yr). β-Cell function and insulin resistance were evaluated by calculating HOMA-β and HOMA-IR, respectively. CRF was assessed by measuring maximal oxygen uptake (V̇o2max). Subjects were divided into the low and high CRF groups within each age group according to the median V̇o2max. Eleven single nucleotide polymorphisms (SNPs) associated with T2DM were analyzed and used to calculate genetic risk score (GRS); subjects were divided into the low, middle, and high GRS groups. The high GRS group had higher HbA1c levels than the low GRS group in both the low and high CRF groups (P < 0.05). Furthermore, the individuals with a high GRS had a lower HOMA-β than those with a low GRS regardless of CRF (P < 0.05). In multiple linear regression analysis, although GRS was a significant predictor of HbA1c (β = 0.153, P = 0.025), V̇o2max was also associated with HbA1c (β = -0.240, P = 0.041) independent of GRS. These results suggest that CRF is associated with HbA1c levels independent of GRS derived from T2DM-related SNPs; however, it does not modify the association of GRS with increased HbA1c or impaired β-cell function.

The construction of risk prediction models using GWAS data and its application to a type 2 diabetes prospective cohort

Recent genome-wide association studies (GWAS) have identified several novel single nucleotide polymorphisms (SNPs) associated with type 2 diabetes (T2D). Various models using clinical and/or genetic risk factors have been developed for T2D risk prediction. However, analysis considering algorithms for genetic risk factor detection and regression methods for model construction in combination with interactions of risk factors has not been investigated. Here, using genotype data of 7,360 Japanese individuals, we investigated risk prediction models, considering the algorithms, regression methods and interactions. The best model identified was based on a Bayes factor approach and the lasso method. Using nine SNPs and clinical factors, this method achieved an area under a receiver operating characteristic curve (AUC) of 0.8057 on an independent test set. With the addition of a pair of interaction factors, the model was further improved (p-value 0.0011, AUC 0.8085). Application of our model to prospective cohort data showed significantly better outcome in disease-free survival, according to the log-rank trend test comparing Kaplan-Meier survival curves (p--value 2:09 x 10(-11)). While the major contribution was from clinical factors rather than the genetic factors, consideration of genetic risk factors contributed to an observable, though small, increase in predictive ability. This is the first report to apply risk prediction models constructed from GWAS data to a T2D prospective cohort. Our study shows our model to be effective in prospective prediction and has the potential to contribute to practical clinical use in T2D.

Zinc and its transporters, pancreatic β-cells, and insulin metabolism

Zinc is an essential trace metal for life. Two families of zinc transporters, SLC30A (ZNT) and SLC39A (ZIP) are required for maintaining cellular zinc homeostasis. ZNTs function to decrease cytoplasmic zinc concentrations whereas ZIPs do the opposite. Expression of zinc transporters can be tissue/cell-type specific or ubiquitous. Zinc transporters that are limited in tissue/cell distributions usually perform specialized tasks to satisfy biological processes in a given cell. For example, ZNT8 is mainly expressed in β-cells and functions to deliver zinc into granules for insulin maturation and secretion. Many other zinc transporters are also expressed in β-cells. Defects in these zinc transporters have been associated with abnormalities in insulin synthesis, maturation, and secretion and subsequent glucose metabolism. This review focuses on the specific roles of zinc and its transporters in insulin metabolism and describes the current knowledge of the function of zinc transporters in β-cell health in animal knockout mouse models with respect to diabetes development in humans.

CDKAL1 gene rs7756992 A/G polymorphism and type 2 diabetes mellitus: a meta-analysis of 62,567 subjects

The Cyclin-dependent kinase 5 regulatory subunit-associated protein 1-like (CDKAL1) gene rs7756992 A/G polymorphism has been suggested to be associated with type 2 diabetes mellitus (T2DM), but the individual studies results are still controversial. To explore the association of CDKAL1 gene rs7756992 A/G polymorphism with T2DM, a meta-analysis involving 62,567 subjects from 21 separate studies was conducted. In the whole population, a significant association was found between CDKAL1 gene rs7756992 A/G polymorphism and T2DM under allelic (OR: 1.180, 95% CI: 1.130–1.230, P = 1.60 × 10⁻¹⁴), recessive (OR: 1.510, 95% CI: 1.380–1.660, P = 8.41 × 10⁻¹⁸), dominant (OR: 1.175, 95% CI: 1.109–1.246, P = 6.30 × 10⁻⁸), homozygous (OR: 1.400, 95% CI: 1.282–1.530, P = 8.02 × 10⁻¹⁴), and heterozygous genetic models (OR: 1.101, 95% CI: 1.040–1.166, P = 0.001). CDKAL1 gene rs7756992 A/G polymorphism was significantly associated with T2DM. The person with G allele of CDKAL1 gene rs7756992 A/G polymorphism might be predisposed to T2DM.

Association between type 2 diabetes and rs10811661 polymorphism upstream of CDKN2A/B: a meta-analysis

To assess the association between type 2 diabetes and rs10811661 polymorphism, upstream of CDKN2A/B, a literature-based search was conducted to collect data. The pooled OR (odds ratio) and 95 % confidence intervals (CI) were used to assess the strength of association between rs10811661 polymorphism and type 2 diabetes. OR with 95 % CI were performed for allele contrasts, additive genetic model, dominant genetic model and recessive genetic model, respectively. The effect model was used if there was heterogeneity between studies. Funnel plots were used to predict publication bias. 17 studies with 29,990 cases and 40,977 controls were enrolled in this meta-analysis. Significant association was found in all of the four genetic models: allele contrast (OR = 1.21, 95 % CI 1.18-1.24), additive genetic model (OR = 1.51, 95 % CI 1.40-1.63), dominant genetic model (OR = 1.37, 95 % CI 1.28-1.47) and recessive genetic model (OR = 1.25, 95 % CI 1.21-1.29). The meta-analysis indicated that rs10811661 polymorphism was significantly associated with the risk of type 2 diabetes.

The SLC30 family of zinc transporters - a review of current understanding of their biological and pathophysiological roles

Two families of zinc (Zn(2 +)) transporters are involved in zinc homeostasis in the body, SLC30 (ZnT, zinc transporter) and SLC39 (ZIP, Zinc(Zn(2+))-Iron(Fe(2+)) Permease). The two zinc transporter family members function in opposite directions to maintain cellular zinc homeostasis. ZnT proteins contribute to the cytoplasmic zinc balance by exporting zinc out to the extracellular space or by sequestrating cytoplasmic zinc into intracellular compartments when cellular zinc levels are elevated. In contrast, ZIP proteins function to increase cytoplasmic zinc concentrations when cellular zinc is depleted. Since the cloning of the first zinc transporter (ZnT1) in 1995, there have been many advances in zinc transporter research including discovery of new members of zinc transporters, identification of gene expression patterns and regulations, recognition of protein distribution patterns in tissues and cells, and understanding of their physiological and pathological roles in humans and animal models. Ten members of the ZnT family have been identified so far. Here we give a review of these advances and discuss the pathological implications and future preventive or therapeutic applications of ZnTs.

The relationship between five widely-evaluated variants in CDKN2A/B and CDKAL1 genes and the risk of type 2 diabetes: a meta-analysis

The genes encoding two cyclin-dependent kinases-inhibitor-2A/B (CDKN2A/B) and 5 regulatory subunit-associated protein-like 1 (CDKAL1) have been investigated extensively in associations with type 2 diabetes; the results, however, are often irreproducible. We therefore sought to evaluate these associations by performing a meta-analysis on five widely-evaluated variants from the two genes. There were 38 studies (patients/controls: 51,940/52,234) for rs10811661, 16 studies (20,029/24,419) for rs564398 in CDKN2A/B gene, and 27 studies (28,383/47,635) for rs7756992, 26 studies (28,816/31,713) for rs7754840, 21 studies (29,260/38,400) for rs10946398 in CDKAL1 gene. Overall risk estimates for type 2 diabetes conferred by rs10811661-T, rs564398-A, rs7754840-C, rs7756992-G, and rs10946398-C alleles were 1.17 (95% CI: 1.10-1.23; P<0.0005; I(2)=83.9%), 1.1 (95% CI: 1.0-1.21; P=0.051; I(2)=88.3%), 1.24 (95% CI: 1.18-1.3; P<0.0005; I(2)=74.3%), 1.2 (95% CI: 1.11-1.3; P<0.0005; I(2)=92.0%), and 1.19 (95% CI: 1.1-1.29; P<0.0005; I(2)=90.8%), respectively. There was evident publication bias for rs564398 and rs7754840. Subgroup analyses by ethnicity showed remarkable divergences in risk estimate for rs564398 between Asians (odds ratio [OR]=1.01; 95% CI: 0.86-1.19; P=0.868) and Caucasians (OR=1.19; 95% CI: 1.03-1.35; P=0.012) (P<0.05). For all variants examined, the results of studies in retrospective design or with population-based controls were comparative with that of overall studies. In meta-regression analyses, age was found to exert a significant influence on the association between rs10811661 and type 2 diabetes (P=0.003), as well as between rs7754840 and gender (P=0.034). Taken together, our findings provide evidence for a significant contribution of CDKN2A/B gene rs10811661 and CDKAL1 gene rs7756992 and rs10946398 to type 2 diabetes.

Individualized therapy for type 2 diabetes: clinical implications of pharmacogenetic data

Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance, abnormally elevated hepatic glucose production, and reduced glucose-stimulated insulin secretion. Treatment with antihyperglycemic agents is initially successful in type 2 diabetes, but it is often associated with a high secondary failure rate, and the addition of insulin is eventually necessary for many patients, in order to restore acceptable glycemic control and to reduce the risk of development and progression of disease complications. Notably, even patients who appear to have similar requirements of antidiabetic regimens show great variability in drug disposition, glycemic response, tolerability, and incidence of adverse effects during treatment. Pharmacogenomics is a promising area of investigation and involves the search for genetic polymorphisms that may explain the interindividual variability in antidiabetic therapy response. The initial positive results portend that genomic efforts will be able to shed important light on variability in pharmacologic traits. In this review, we summarize the current understanding of genetic polymorphisms that may affect the responses of subjects with T2DM to antidiabetic treatment. These genes belong to three major classes: genes involved in drug metabolism and transporters that influence pharmacokinetics (including the cytochrome P450 [CYP] superfamily, the organic anion transporting polypeptide [OATP] family, and the polyspecific organic cation transporter [OCT] family); genes encoding drug targets and receptors (including peroxisome proliferator-activated receptor gamma [PPARG], the adenosine triphosphate [ATP]-sensitive potassium channel [K(ATP)], and incretin receptors); and genes involved in the causal pathway of T2DM that are able to modify the effects of drugs (including adipokines, transcription factor 7-like 2 (T cell specific, HMG-box) [TCF7L2], insulin receptor substrate 1 [IRS1], nitric oxide synthase 1 (neuronal) adaptor protein [NOS1AP], and solute carrier family 30 (zinc transporter), member 8 [SLC30A8]). In addition to these three major classes, we also review the available evidence on novel genes (CDK5 regulatory subunit associated protein 1-like 1 [CDKAL1], insulin-like growth factor 2 mRNA binding protein 2 [IGF2BP2], potassium voltage-gated channel, KQT-like subfamily, member 1 [KCNQ1], paired box 4 [PAX4] and neuronal differentiation 1 [NEUROD1] transcription factors, ataxia telangiectasia mutated [ATM], and serine racemase [SRR]) that have recently been proposed as possible modulators of therapeutic response in subjects with T2DM.

Rs4074134 near BDNF gene is associated with type 2 diabetes mellitus in Chinese Han population independently of body mass index

Obesity and family history are the most important predictors for type 2 diabetes mellitus(T2DM) in the Chinese Han population. However, it is not known whether the genetic loci related to obesity are associated with the risk of developing T2DM in this population. The present case-control study evaluated the associations between five genetic loci for obesity and the pathogenesis of T2DM. The study included 1117 Chinese Han patients with T2DM, 1629 patients with pre-diabetes (impaired fasting glucose and impaired glucose tolerance, IFG/IGT) and 1113 control subjects residing in Beijing. Five genetic loci including rs2815752 near NEGR1, rs10938397 near GNPDA2, rs4074134 near BDNF, rs17782313 near MC4R and rs1084753 near KCTD15 were genotyped. The results showed an association between rs4074134-BDNF minor allele and T2DM irrespective of age, gender and body mass index (BMI) (OR = 0.87; 95%CI: 0.77–0.99, P = 0.04). This SNP was also associated with pre-diabetes (OR = 0.87; 95%CI: 0.77–0.97, P = 0.01) independently of age, gender and BMI. No associations were found between diabetes or pre-diabetes and any of the other SNP loci studied. Genotype–phenotype association analysis (adjusting for age and gender) showed rs4074134-BDNF to be associated with BMI, waist circumference, fasting and postprandial plasma glucose, fasting serum insulin, and HOMA-IR in subjects without T2DM. However, fasting and postprandial plasma glucose were the only significant factors after adjusting for BMI. These results suggest that the common variation of BDNF (rs4074134) is associated with T2DM independently of obesity in Chinese Han population. This variant also has an effect on plasma glucose concentration, BMI and insulin sensitivity.

Association of glucokinase regulatory protein polymorphism with type 2 diabetes and fasting plasma glucose: a meta-analysis

Glucokinase regulatory protein (GCKR) which binds to glucokinase (GCK) in the nucleus and inhibits its activity in the presence of fructose-6-phosphate is critical for glucose metabolism. In the past few years, a number of case-control studies have been carried out to investigate the relationship between the GCKR polymorphism and type 2 diabetes (T2D) since it was first identified to be associated with fasting plasma glucose levels, insulin resistance through genome-wide association approach. After that, a number of studies reported that the rs780094 polymorphism in GCKR has been implicated in T2D risk. However, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of 19 studies involving a total of 298,977 subjects for GCKR rs780094 to evaluate its effect on genetic susceptibility for T2D. In a combined analysis, the summary per-allele odds ratio for T2D of the rs780094 polymorphism was 1.11 (95 % CI: 1.07-1.14, P < 10(-5)). Significant results were also observed using dominant (OR = 1.18, 95 % CI: 1.05-1.34, P < 10(-5)) or recessive genetic model (OR = 1.20, 95 % CI: 1.12-1.28, P < 10(-5)). Significant results were found in Asians and Caucasians when stratified by ethnicity. Besides, the polymorphism was found to be significantly associated with increased fasting plasma glucose level. There was strong evidence of heterogeneity, which largely disappeared after stratification by ethnicity. This meta-analysis suggests that the rs780094 polymorphism in GCKR is associated with elevated T2D risk, but these associations vary in different ethnic populations.