Impact of transcription factor 7-like 2 (TCF7L2) on pancreatic islet function and morphology in mice and men

Clinical Impact of the TCF7L2 Gene rs7903146 Type 2 Diabetes Mellitus Risk Polymorphism in Women with Gestational Diabetes Mellitus: Impaired Glycemic Control and Increased Need of Insulin Therapy

Background The single nucleotide polymorphism in TCF7L2 rs7903146 is associated with an increased risk of type 2 diabetes mellitus and gestational diabetes mellitus. Mechanisms by which this mutation acts, and its impact on the clinical course of the diseases remain unclear. Here we investigated the clinical impact of the T risk allele in women with gestational diabetes mellitus.

Methods We genotyped the C/T polymorphism in 164 Caucasian women with GDM (German n=114; Greek n=50). The impact of the T allele on the results of the 75g oral-glucose-tolerance-test, and on the required therapy (diet/lifestyle or insulin) was investigated.

Results During oral-glucose-tolerance-test, women harboring the T allele displayed significantly higher glucose values at 60 min (p=0.034) and were more likely to require insulin therapy even after adjusting for confounders, such as BMI and age.

Conclusion These results provide evidence that the T risk allele in TCF7L2 rs7903146 is associated with failure in early postprandial glycemic control and requirement of insulin therapy in women with gestational diabetes mellitus, even after adjusting for confounding factors such BMI and age.

Association between the UBE2Z rs46522 and TCF7L2 rs7903146 polymorphisms with type 2 diabetes in south western Iran

BACKGROUND

Transcription factor 7-like 2 Protein (TCF7L2) has a strong role in the pathogenesis of type 2 diabetes mellitus (T2DM). Association between rs7903146 and T2D risk reported in some of populations. Also many loci such as UBE2Z rs46522 are affecting by TCF7L2 transcription factor have been found associated with T2D. The present study aimed to evaluate association of the SNPs with risk of T2D among our population.

METHODS

This case-control study was conducted on 150 T2D patients and 150 healthy people (as a control group) in south western Iran. Genotyping was performed by PCR-RFLP.

RESULTS

The frequency of genotypes showed no remarkable difference between T2DM patients and control group. The odds ratios of rs7903146 (C/T) polymorphism for CC and TC genotypes were 1.9 (95% CI, 0.85 to 4.24; P=0.12) and 0.81 (95% CI, 0.47 to 1.38; P=0.43) compared with the TT genotype, respectively. The odds ratios of rs46522 (C/T) polymorphism for TT and TC genotypes were 1.75 (95% CI, 0.86 to 3.59; P=0.13) and 1.38 (95% CI, 0.81to 2.35; P=0.24) compared with the CC genotype, respectively.

CONCLUSION

Our study indicates no association of T2D in south western Iran with the rs7903146 and rs46522 variants.

Glucose tolerance and free fatty acid metabolism in adults with variations in TCF7L2 rs7903146

OBJECTIVE

TCF7L2 variant rs7903146 is associated with increased risk for type 2 diabetes. We investigated the effect of TCF7L2 variant rs7903146 and glucose tolerance on free fatty acid (FFA) metabolism.

RESEARCH DESIGN AND METHODS

We recruited 120 individuals, half homozygous for the major CC allele and half homozygous for the minor TT allele at rs7903146; each underwent a 2-h, 75g oral glucose tolerance test (OGTT). Plasma glucose, insulin and free fatty acid concentrations were measured on blood collected before and during the OGTT.

RESULTS

Total FFA concentrations and percent FA species during OGTT were not different in CC and TT carriers when males and females were considered together. However, monounsaturated fatty acid (MUFA) concentrations and percentages were greater in TT than CC females during the OGTT. TT carriers with high HOMA-IR had significantly greater fasting FFA concentrations, lower disposition index (DI) and greater AUC of glucose than high HOMA-IR CC carriers, whereas no such differences were observed in the low HOMA-IR group. We found that fasting (826±25 vs. 634±22μmol/L, P<0.0001) and OGTT plasma FFA concentrations were greater in IGT than NGT subjects, and the difference remained after adjusting for sex, age, BMI, and genotype. Finally, IGT subjects had greater MUFA concentrations and percentages than NGT subjects during OGTT.

CONCLUSIONS

Despite similar fasting insulin and glucose, fasting plasma FFA are greater in IGT than NGT adults. Insulin resistance and sex influence plasma FFA responses amongst carriers of the minor T allele of TCF7L2 rs7903146.

Clinical and non-targeted metabolomic profiling of homozygous carriers of Transcription Factor 7-like 2 variant rs7903146

An important role of the type 2 diabetes risk variant rs7903146 in TCF7L2 in metabolic actions of various tissues, in particular of the liver, has recently been demonstrated by functional animal studies. Accordingly, the TT diabetes risk allele may lead to currently unknown alterations in human. Our study revealed no differences in the kinetics of glucose, insulin, C-peptide and non-esterified fatty acids during an OGTT in homozygous participants from a German diabetes risk cohort (n = 1832) carrying either the rs7903146 CC (n = 15) or the TT (n = 15) genotype. However, beta-cell function was impaired for TT carriers. Covering more than 4000 metabolite ions the plasma metabolome did not reveal any differences between genotypes. Our study argues against a relevant impact of TCF7L2 rs7903146 on the systemic level in humans, but confirms the role in the pathogenesis of type 2 diabetes in humans as a mechanism impairing insulin secretion.

Malondialdehyde regulates glucose-stimulated insulin secretion in murine islets via TCF7L2-dependent Wnt signaling pathway

Evidence showed strong relations between malondialdehyde (MDA) levels and different pathological stages of diabetes. Here, an explicit system with freshly isolated islets and precisely controlled MDA gradient was employed to investigate the physiological effect of MDA on GSIS. Promoter analysis, pathway mapping, Q-PCR profiling, and siRNA verification were performed to clarify the intracellular signaling pathways. MDA at a moderately high level (5 and 10μM) promoted GSIS and accompanied with ATP/ADP ratio, cytosolic Ca(2+) level, and key regulators (GK, GLUT2, PDX1, and UCP2) changes in islets. Both upstream (PI3K and p-AKT) and downstream (TCF7L2 and TCF7) factors of Wnt pathway showed greatest changes. Knockdown of TCF7L2 blocked the MDA-induced GSIS elevation. These results indicated that MDA acted as a signaling messenger and regulated islet GSIS mainly through Wnt pathway. Therefore, the elevated MDA level and up-regulated Wnt signaling pathway could be an etiological factor in the development of hyperinsulinemia and type 2 diabetes.