Transcription factor 7-like 2 (TCF7L2) polymorphism and hyperglycemia in an adult Italian population-based cohort

Associations of common variants in the SLC16A11, TCF7L2, and ABCA1 genes with pediatric-onset type 2 diabetes and related glycemic traits in families: A case-control and case-parent trio study

BACKGROUND

There is evidence of associations of single-nucleotide polymorphisms (SNPs) with type 2 diabetes (T2D) and related glycemic traits in adults, but there is a little information about such associations in youths.

OBJECTIVE

The aim of this study was to evaluate the associations of SNPs in the TCF7L2, SLC16A11, and ABCA1 genes with T2D and related glycemic traits in Mexican children and adolescents.

SUBJECTS

A total of 99 families with children with T2D (n = 327) and 83 families with children without the disease (n = 212).

METHODS

The associations between SNPs of TCF7L2 (rs7903146 and rs12255372), SLC16A11 (rs13342232), and ABCA1 (rs9282541) with T2D were analyzed. We also evaluated the effects of SNPs on quantitatively related glycemic traits after adjusting for age, sex, and the presence of overweight or obesity.

RESULTS

The G allele of SLC16A1 /rs13342232 was associated with T2D in adults (adjusted odds ratio [ORadj] = 1.89; 95% confidence interval [CI]: 1.18; 3.06) and children (ORadj = 1.94; 95% CI: 1.25; 3.00). In addition, the combined analysis of case-control and case-parent trio was also significant (OR = 1.43; 95% CI: 1.12; 1.74). After adjusting for known confounding factors, we found a significant association between TCF7L2/rs122555372 and C-peptide (β = -0.76, P = .005) in patients with diabetes and between fasting glucose (β = 2.05, P = .039) and homeostatic model assessment of β-cell function (β = -32.14, P = .025) levels in individuals without diabetes.

CONCLUSIONS

The results suggest that SLC16A1 /rs13342232 might be involved in the risk of pediatric-onset T2D in Mexican families. Moreover, TCF7L2/rs122555372 was associated with pancreatic reserve in patients with T2D and with fasting glucose and β-cell function in individuals without diabetes.

The Protective Effect of Transcription Factor 7-Like 2 Risk Allele rs7903146 against Elevated Fasting Plasma Triglyceride in Type 2 Diabetes: A Meta-Analysis

BACKGROUND

The results from published studies regarding association of transcription factor 7-like 2 (TCF7L2) variant rs7903146 with dyslipidemia have been conflicting and inconclusive.

METHODS

We carried out a meta-analysis that aimed to investigate the association of the rs7903146 variant with plasma lipid levels using electronic database and published studies. Data was extracted by a standard algorithm. Dominant, recessive, homozygote, and heterozygote comparison models were utilized.

RESULTS

24 studies incorporating 52,785 subjects were included in this meta-analysis. Overall, the minor allele (T) was associated with lower risk for hypertriglyceridemia in subjects with type 2 diabetes (dominant model: SMD = -0.04, 95% CI (-0.08, 0.00), P = 0.048, P heterogeneity = 0.47; recessive model: SMD = -0.10, 95% CI (-0.18, -0.02), P = 0.01, P heterogeneity = 0.56). No association was found between minor (T) allele and plasma TC, LDL-c, or HDL-c levels in subjects with type 2 diabetes or metabolic syndrome (MetS) and no association was found between minor (T) allele and plasma TG levels in nondiabetic subjects.

CONCLUSIONS

Our meta-analysis indicated the association between TCF7L2 rs7903146 polymorphism and low plasma triglyceride (TG) level in subjects with type 2 diabetes. No association was found between rs7903146 variant and plasma lipids in nondiabetic subjects.

TCF7L2 gene polymorphisms and type 2 diabetes: association with diabetic retinopathy and cardiovascular autonomic neuropathy

Type 2 diabetes (T2DM) is a complex disease resulting from the contribution of both environmental and genetic factors. Recently, the list of genes implicated in the susceptibility to T2DM has substantially grown, also as a consequence of the great development of the genome-wide association studies in the last decade. Common polymorphisms in TCF7L2 gene have shown to have a strong effect with respect to many other involved genes. The aims of our study were to confirm the role of TCF7L2 in the susceptibility to T2DM in the Italian population and to investigate whether TCF7L2 genotypes also contribute to the clinical phenotypes variability and to diabetic complications development. Three TCF7L2 polymorphisms (rs7903146, rs7901695 and rs12255372) have been analyzed by allelic discrimination assays in a cohort of 154 Italian patients with T2DM and 171 healthy controls. A case-control association study and a genotype-phenotype correlation study have been carried out. Consistent with previous studies, all three SNPs showed a strong association with susceptibility to T2DM, both at genotypic (P = 0.003, P = 0.004 and P = 0.012) and at allelic level (P = 0.0004, P = 0.0004 and P = 0.003). Moreover, we observed associations between TCF7L2 variants and the following diabetic complications: diabetic retinopathy, cardiovascular disease and coronary artery disease. We also found a strong correlation between the rs7903146 and the presence of cardiovascular autonomic neuropathy (P = 0.02 with a high OR = 8.28). In conclusion, our study, in addition to confirming the involvement of TCF7L2 gene in the T2DM susceptibility, has shown that TCF7L2 genetic variability also contributes to the development of diabetic complications such as retinopathy and cardiovascular autonomic neuropathy.

Sterol regulatory element-binding factor 2 (SREBF-2) predicts 7-year NAFLD incidence and severity of liver disease and lipoprotein and glucose dysmetabolism

We prospectively assessed the impact of a sterol regulatory element-binding factor-2 (SREBF-2) polymorphism on the risk of developing nonalcoholic fatty liver disease (NAFLD) and on liver histology and lipoprotein and glucose metabolism in biopsy-proven NAFLD. In a population-based study, we followed 175 nonobese, nondiabetic participants without NAFLD or metabolic syndrome at baseline, characterized for the SREBF-2 rs133291 C/T polymorphism, dietary habits, physical activity, adipokines, C-reactive protein (CRP), and endothelial adhesion molecules. A comparable cohort of NAFLD patients underwent liver biopsy, an oral glucose tolerance test with minimal model analysis to yield glucose homeostasis parameters, and an oral fat tolerance test with measurement of plasma lipoproteins, adipokines, and cytokeratin-18 fragments. After 7 years, 27% of subjects developed NAFLD and 5% developed diabetes. SREBF-2 predicted incident NAFLD and diabetes and CRP and endothelial adhesion molecule changes. In biopsy-proven NAFLD patients, SREBF-2 predicted nonalcoholic steatohepatitis (odds ratio 2.92 [95% CI 2.08-4.18], P = 0.002) and the severity of tissue insulin resistance, β-cell dysfunction, and oral fat intolerance (characterized by higher postprandial lipemia, cholesterol enrichment of triglyceride-rich lipoproteins and oxidized LDLs, HDL cholesterol fall, adipokine imbalance, and postprandial apoptosis activation). An SREBF-2 polymorphism predisposes individuals to NAFLD and associated cardiometabolic abnormalities and affects liver histology and glucose and lipid metabolism in biopsy-proven NAFLD.

Deletion of CDKAL1 affects high-fat diet-induced fat accumulation and glucose-stimulated insulin secretion in mice, indicating relevance to diabetes

Background/Objective

The CDKAL1 gene is among the best-replicated susceptibility loci for type 2 diabetes, originally identified by genome-wide association studies in humans. To clarify a physiological importance of CDKAL1, we examined effects of a global Cdkal1-null mutation in mice and also evaluated the influence of a CDKAL1 risk allele on body mass index (BMI) in Japanese subjects.

Methods

In Cdkal1-deficient (Cdkal1^−/−) mice, we performed oral glucose tolerance test, insulin tolerance test, and perfusion experiments with and without high-fat feeding. Based on the findings in mice, we tested genetic association of CDKAL1 variants with BMI, as a measure of adiposity, and type 2 diabetes in Japanese.

Principal Findings

On a standard diet, Cdkal1^−/− mice were modestly lighter in weight than wild-type littermates without major alterations in glucose metabolism. On a high fat diet, Cdkal1^−/− mice showed significant reduction in fat accumulation (17% reduction in %intraabdominal fat, P = 0.023 vs. wild-type littermates) with less impaired insulin sensitivity at an early stage. High fat feeding did not potentiate insulin secretion in Cdkal1^−/− mice (1.0-fold), contrary to the results in wild-type littermates (1.6-fold, P<0.01). Inversely, at a later stage, Cdkal1^−/− mice showed more prominent impairment of insulin sensitivity and glucose tolerance. mRNA expression analysis indicated that Scd1 might function as a critical mediator of the altered metabolism in Cdkal1^−/− mice. In accordance with the findings in mice, a nominally significant (P<0.05) association between CDKAL1 rs4712523 and BMI was replicated in 2 Japanese general populations comprising 5,695 and 12,569 samples; the risk allele for type 2 diabetes was also associated with decreased BMI.

Conclusions

Cdkal1 gene deletion is accompanied by modestly impaired insulin secretion and longitudinal fluctuations in insulin sensitivity during high-fat feeding in mice. CDKAL1 may affect such compensatory mechanisms regulating glucose homeostasis through interaction with diet.

Cell type-specific binding patterns reveal that TCF7L2 can be tethered to the genome by association with GATA3

Background

The TCF7L2 transcription factor is linked to a variety of human diseases, including type 2 diabetes and cancer. One mechanism by which TCF7L2 could influence expression of genes involved in diverse diseases is by binding to distinct regulatory regions in different tissues. To test this hypothesis, we performed ChIP-seq for TCF7L2 in six human cell lines.

Results

We identified 116,000 non-redundant TCF7L2 binding sites, with only 1,864 sites common to the six cell lines. Using ChIP-seq, we showed that many genomic regions that are marked by both H3K4me1 and H3K27Ac are also bound by TCF7L2, suggesting that TCF7L2 plays a critical role in enhancer activity. Bioinformatic analysis of the cell type-specific TCF7L2 binding sites revealed enrichment for multiple transcription factors, including HNF4alpha and FOXA2 motifs in HepG2 cells and the GATA3 motif in MCF7 cells. ChIP-seq analysis revealed that TCF7L2 co-localizes with HNF4alpha and FOXA2 in HepG2 cells and with GATA3 in MCF7 cells. Interestingly, in MCF7 cells the TCF7L2 motif is enriched in most TCF7L2 sites but is not enriched in the sites bound by both GATA3 and TCF7L2. This analysis suggested that GATA3 might tether TCF7L2 to the genome at these sites. To test this hypothesis, we depleted GATA3 in MCF7 cells and showed that TCF7L2 binding was lost at a subset of sites. RNA-seq analysis suggested that TCF7L2 represses transcription when tethered to the genome via GATA3.

Conclusions

Our studies demonstrate a novel relationship between GATA3 and TCF7L2, and reveal important insights into TCF7L2-mediated gene regulation.

T2D risk haplotypes of the TCF7L2 gene in the Czech population sample: the association with free fatty acids composition

The association of transcription factor 7-like 2 (TCF7L2) gene variants with the pathogenesis of T2D, gestational diabetes and polycystic ovary syndrome (PCOS) was examined. The study involved 1460 individuals: 347 T2D patients (D); 261 gestational diabetics (G); 147 offspring of T2D (O); 329 women with PCOS, and 376 controls (C). The SNPs: rs7901695; rs7903146; rs12255372 in the TCF7L2 gene were genotyped. Anthropometric and biochemical parameters, oGTT derived indices were assessed. In addition, free fatty acids (FFAs) were evaluated in 183 non-diabetic women. The CTT haplotype showed the strongest association with T2D with OR 1.57, p=0.0003. The frequency of the CTT/CTT haplotype was decreasing in following order: D 10.6, O 9.5, G 6.1, C 5.3 and PCOS 4.9 [%]. Among CTT carriers, significantly decreased levels of oGTT-stimulated insulin and C-peptide as well as proportions of fasting PUFAs were observed. The carriership of CTG/TCG was associated with gestational diabetes, OR 2.59, p=0.036. The association of TCF7L2 haplotypes with T2D and gestational diabetes but not with PCOS was confirmed. Novel association of TCF7L2 with FFAs composition was found.

The rs553668 polymorphism of the ADRA2A gene predicts the worsening of fasting glucose values in a cohort of subjects without diabetes. A population-based study

AIMS

Single-nucleotide polymorphisms in the human ADRA2A gene have been associated with increased risk of Type 2 diabetes. The associations between the rs553668 polymorphism and fasting glucose concentrations both cross-sectionally and longitudinally after 6-year follow-up were evaluated in an adult Caucasian population-based cohort.

METHODS

From a cohort of 1658 individuals, after excluding patients with diabetes, those who died and those whose blood samples were not available for genotyping, data of 1345 individuals were analysed.

RESULTS

Subjects homozygous for the A allele showed significantly increased baseline fasting glucose values and a significant worsening of fasting glucose (β = 0.48; 95% CI 0.10-0.86) and insulin secretion (β =-20.75; -32.67 to -8.82 for homeostasis model assessment for β-cell function) at follow-up by using generalized estimating equations. Incidence of impaired fasting glucose and diabetes was almost twofold higher in subjects homozygous for the A allele (respectively: incident impaired fasting glucose 7.6-8.2, 16.1%, incident diabetes 1.7-2.3, 3.2% in GG, AG, AA carriers).

CONCLUSIONS

Our results suggested that the rs553668 polymorphism is associated with glucose worsening in subjects without diabetes at baseline.

Association of transcription factor 7-like 2 (TCF7L2) gene polymorphism with posttransplant diabetes mellitus in kidney transplant patients medicated with tacrolimus

New onset posttransplant diabetes mellitus (PTDM) has a high incidence after kidney transplantation in patients medicated with tacrolimus. PTDM can adversely affect patient and graft survival. The pathophysiology of PTDM closely mimics type 2 diabetes mellitus (T2DM). One of the possible genetic factors predisposing individuals to PTDM might be a polymorphism in the transcription factor 7-like 2 gene (TCF7L2). This polymorphism has previously been associated with increased risk of T2DM in the general population. Therefore, the present study aimed to evaluate TCF7L2 polymorphisms in PTDM in kidney transplant patients medicated with tacrolimus. Non-diabetic kidney transplant patients medicated with tacrolimus (n = 234) were genotyped for the presence of TCF7L2 gene variants (rs12255372 and rs7903146) using TaqMan probes. Of the 234 patients, 66 patients had developed PTDM and 168 had not. Frequencies of the studied single nucleotide polymorphisms (SNPs) did not differ significantly between the study groups. Moreover, haplotype analyses failed to detect any associations between TCF7L2 haplotypes and PTDM. However, in late-onset PTDM (developed later that 2 weeks from transplantation), frequencies of the rs7903146 TT genotype and T minor allele were significantly increased compared to non-PTDM controls (17.9% vs. 5.9%, p = 0.017, OR: 4.13, 95% CI: 1.19-14.33 for TT genotype, 39.3% vs. 25.9%, p = 0.038 for T allele). If the application of TCF7L2 rs7903146 SNPs as a marker for PTDM is confirmed by further independent studies, replacing tacrolimus with other immunosuppressants could be warranted in patients at high risk of PTDM, as diagnosed by TCF7L2 genotyping.

Genetic predisposition to long-term nondiabetic deteriorations in glucose homeostasis: Ten-year follow-up of the GLACIER study

OBJECTIVE

To assess whether recently discovered genetic loci associated with hyperglycemia also predict long-term changes in glycemic traits.

RESEARCH DESIGN AND METHODS

Sixteen fasting glucose-raising loci were genotyped in middle-aged adults from the Gene x Lifestyle interactions And Complex traits Involved in Elevated disease Risk (GLACIER) Study, a population-based prospective cohort study from northern Sweden. Genotypes were tested for association with baseline fasting and 2-h postchallenge glycemia (N = 16,330), and for changes in these glycemic traits during a 10-year follow-up period (N = 4,059).

RESULTS

Cross-sectional directionally consistent replication with fasting glucose concentrations was achieved for 12 of 16 variants; 10 variants were also associated with impaired fasting glucose (IFG) and 7 were independently associated with 2-h postchallenge glucose concentrations. In prospective analyses, the effect alleles at four loci (GCK rs4607517, ADRA2A rs10885122, DGKB-TMEM195 rs2191349, and G6PC2 rs560887) were nominally associated with worsening fasting glucose concentrations during 10-years of follow-up. MTNR1B rs10830963, which was predictive of elevated fasting glucose concentrations in cross-sectional analyses, was associated with a protective effect on postchallenge glucose concentrations during follow-up; however, this was only when baseline fasting and 2-h glucoses were adjusted for. An additive effect of multiple risk alleles on glycemic traits was observed: a weighted genetic risk score (80th vs. 20th centiles) was associated with a 0.16 mmol/l (P = 2.4 × 10⁻⁶) greater elevation in fasting glucose and a 64% (95% CI: 33-201%) higher risk of developing IFG during 10 years of follow-up.

CONCLUSIONS

Our findings imply that genetic profiling might facilitate the early detection of persons who are genetically susceptible to deteriorating glucose control; studies of incident type 2 diabetes and discrete cardiovascular end points will help establish whether the magnitude of these changes is clinically relevant.