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Nutrigenetic studies analyzing gene–diet interactions of the TCF7L2-rs7903146 C > T polymorphism on type-2 diabetes (T2D) have shown controversial results. A reason contributing to this may be the additional modulation by obesity. Moreover, TCF7L2-rs7903146 is one of the most influential variants in T2D-genetic risk scores (GRS). Therefore, to increase the predictive value (PV) of GRS it is necessary to first see whether the included polymorphisms have heterogeneous effects. We comprehensively investigated gene-obesity interactions between the TCF7L2-rs7903146 C > T polymorphism on T2D (prevalence and incidence) and analyzed other T2D-polymorphisms in a sub-sample. We studied 7018 PREDIMED participants at baseline and longitudinally (8.7 years maximum follow-up). Obesity significantly interacted with the TCF7L2-rs7903146 on T2D prevalence, associations being greater in non-obese subjects. Accordingly, we prospectively observed in non-T2D subjects (n = 3607) that its association with T2D incidence was stronger in non-obese (HR: 1.81; 95% CI: 1.13–2.92, p = 0.013 for TT versus CC) than in obese subjects (HR: 1.01; 95% CI: 0.61–1.66; p = 0.979; p-interaction = 0.048). Accordingly, TCF7L2-PV was higher in non-obese subjects. Additionally, we created obesity-specific GRS with ten T2D-polymorphisms and demonstrated for the first time their higher strata-specific PV. In conclusion, we provide strong evidence supporting the need for considering obesity when analyzing the TCF7L2 effects and propose the use of obesity-specific GRS for T2D.

Aims/hypothesis Non-alcoholic fatty liver disease (NAFLD) associated with type 2 diabetes may more easily progress towards severe forms of non-alcoholic steatohepatitis (NASH) and cirrhosis. Although the Wnt effector transcription factor 7-like 2 (TCF7L2) is closely associated with type 2 diabetes risk, the role of TCF7L2 in NAFLD development remains unclear. Here, we investigated how changes in TCF7L2 expression in the liver affects hepatic lipid metabolism based on the major risk factors of NAFLD development. Methods Tcf7l2 was selectively ablated in the liver of C57BL/6N mice by inducing the albumin ( Alb ) promoter to recombine Tcf7l2 alleles floxed at exon 5 (liver-specific Tcf7l2 -knockout [KO] mice: Alb-Cre;Tcf7l2 f/f ). Alb-Cre;Tcf7l2 f/f and their wild-type ( Tcf7l2 f/f ) littermates were fed a high-fat diet (HFD) or a high-carbohydrate diet (HCD) for 22 weeks to reproduce NAFLD/NASH. Mice were refed a standard chow diet or an HCD to stimulate de novo lipogenesis (DNL) or fed an HFD to provide exogenous fatty acids. We analysed glucose and insulin sensitivity, metabolic respiration, mRNA expression profiles, hepatic triglyceride (TG), hepatic DNL, selected hepatic metabolites, selected plasma metabolites and liver histology. Results Alb-Cre;Tcf7l2 f/f essentially exhibited increased lipogenic genes, but there were no changes in hepatic lipid content in mice fed a normal chow diet. However, following 22 weeks of diet-induced NAFLD/NASH conditions, liver steatosis was exacerbated owing to preferential metabolism of carbohydrate over fat. Indeed, hepatic Tcf7l2 deficiency enhanced liver lipid content in a manner that was dependent on the duration and amount of exposure to carbohydrates, owing to cell-autonomous increases in hepatic DNL. Mechanistically, TCF7L2 regulated the transcriptional activity of Mlxipl (also known as ChREBP ) by modulating O -GlcNAcylation and protein content of carbohydrate response element binding protein (ChREBP), and targeted Srebf1 (also called SREBP1 ) via miRNA (miR)-33-5p in hepatocytes. Eventually, restoring TCF7L2 expression at the physiological level in the liver of Alb-Cre;Tcf7l2 f/f mice alleviated liver steatosis without altering body composition under both acute and chronic HCD conditions. Conclusions/interpretation In mice, loss of hepatic Tcf7l2 contributes to liver steatosis by inducing preferential metabolism of carbohydrates via DNL activation. Therefore, TCF7L2 could be a promising regulator of the NAFLD associated with high-carbohydrate diets and diabetes since TCF7L2 deficiency may lead to development of NAFLD by promoting utilisation of excess glucose pools through activating DNL. Data availability RNA-sequencing data have been deposited into the NCBI GEO under the accession number GSE162449 ( www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE162449 ). Graphical abstract

Diabetes mellitus is a major health concern worldwide; lifestyle and rising urbanization are the key contributing factors. The genetic factors implicated in type 2 diabetes include the transcription factor 7-like 2 ( TCF7L2 ) gene on chromosome 10q25.3, which has been greatly linked with diabetes, but the mechanisms and therapeutic effect on this gene are yet to be clearly defined. The objective of the research was to discover and screen natural phytochemicals of Moringa oleifera , especially carvacrol, as promising TCF7L2 inhibitors through combined in-silico methods. We have used a computational pipeline that includes ADMET profiling, molecular docking, molecular, dynamics (MD) simulations, and density functional theory (DFT) analysis. The ADMET analysis demonstrated that carvacrol has desirable pharmacokinetics, such as high gastrointestinal absorption, drug-likeness, and low-predicted oral toxicity. Molecular docking studies showed that carvacrol has a high binding affinity with the TCF7L2 protein with a binding energy of -5.5 kcal/mol. The conformational stability of the carvacrol-TCF7L2 complex was further validated through an extended 200 ns MD simulation, where the protein backbone RMSD stabilized after ~ 40 ns within ~ 0.25–0.35 nm (2.5–3.5 A), while the ligand RMSD remained consistently low at ~ 0.01–0.02 nm (0.1–0.2 A), supported by a persistent hydrogen-bond network throughout the trajectory. The chemical stability and reactivity of the compound were confirmed by DFT calculations. These findings indicate that carvacrol has potential as a lead compound against TCF7L2 in the treatment of type 2 diabetes. These results are in support of the therapeutic relevance of carvacrol, though experiments are necessary to prove its efficacy and safety in biological systems.

Context:Increased prevalence of type 2 diabetes mellitus and prediabetes worldwide is attributed in part to an unhealthy diet.Objective:To evaluate whether 12 weeks of high monounsaturated fatty acid (MUFA) or fiber-rich weight-maintenance diet lowers hepatic fat and improves glucose tolerance in people with prediabetes.Design:Subjects underwent a [6, 6-2H2]–labeled 75-g oral glucose tolerance test to estimate hepatic insulin sensitivity and liver fat fraction (LFF) using magnetic resonance spectroscopy before and after intervention.Setting:Mayo Clinic Clinical Research Trials Unit.Participants:43 subjects with prediabetes.Intervention:Subjects were randomized into three isocaloric weight-maintaining diets containing MUFA (olive oil), extra fiber, and standard US food (control-habitual diet).Outcome Measures:LFF, glucose tolerance, and indices of insulin action and secretion.Results:Body weight was maintained constant in all groups during the intervention. Glucose and hormonal concentrations were similar in all groups before, and unchanged after, 12 weeks of intervention. LFF was significantly lower after intervention in the MUFA group (P < 0.0003) but remained unchanged in the fiber (P = 0.25) and control groups (P = 0.45). After 12 weeks, LFF was significantly lower in the MUFA than in the control group (P = 0.01), but fiber and control groups did not differ (P = 0.41). Indices of insulin action and secretion were not significantly different between the MUFA and control groups after intervention (P ≥ 0.11), but within-group comparison showed higher hepatic (P = 0.01) and total insulin sensitivity (P < 0.04) with MUFA.Conclusions:Twelve weeks of a MUFA diet decreases hepatic fat and improves both hepatic and total insulin sensitivity.We studied people with prediabetes and found that a 12-week diet supplemented with olive oil lowered liver fat measured with MRS and improved hepatic insulin sensitivity in the absence of weight loss.

Background/Aims: The long non-coding RNA colorectal neoplasia differentially expressed (CRNDE) contributes to the proliferation and migration of tumors. However, its molecular mechanism underlying gastric cancer remains unknown. In the present study, we investigated whether CRNDE was involved in the development of colorectal cancer via the binding of microRNA (miR)-217 with transcription factor 7-like 2 (TCF7L2) to enhance the Wnt signaling pathway. Methods: Quantitative polymerase chain reaction was used to detect CRNDE, miR-217 and TCF7L2 in colorectal cancer tissues and cells. The CCK-8 assay, wound healing assay, and Transwell assay were used to detect cell proliferation, migration and invasion, respectively. Western blotting and luciferase activity assays were used to identify CRNDE and TCF7L2 as one of the direct targets of miR-217. The activity of the Wnt/β-catenin signaling pathway was analyzed by the TOPflash assay, and the subcellular localization of β-catenin and TCF7L2 was analyzed by western blotting and confocal microscopy. Results: In this study, we found that high expression of CRNDE is negatively correlated with low expression of miR-217 in colorectal cancer tissue and colorectal cancer cells. The dual luciferase reporter analysis showed that miR-217 is bound to CRNDE and TCF7L2 and negatively regulate their expression. CRNDE down-regulation inhibited the cell proliferation, migration and invasion in vitro and in vivo and the inhibitions were both completely blocked after miR-217 inhibition or TCF7L2 overexpression. Finally, TOPflash analysis showed that the activity of Wnt/β-catenin signaling is inhibited by CRNDE down-regulation and rescued by TCF7L2 over-expression. Consistently immunostaining and western blotting analysis showed that the expression of b-catenin and TCF7L2 in the nucleus was significantly decreased by CRNDE down-regulation and was rescued by TCF7L2 over-expression. Conclusions: The present study suggest that CRNDE involves in the cell proliferation, migration and invasion of colorectal cancer cells via increasing the expression of TCF7L2 and activity of Wnt/β-catenin signaling through binding miR-217 competitively.

In treating patients with castration resistant prostate cancer (CRPC), enzalutamide, the second-generation androgen receptor (AR) antagonist, is an accepted standard of care. However, clinical benefits are limited to a median time of 4.8 months because resistance inevitably emerges. To determine the mechanism of treatment resistance, we carried out a RNA sequence analysis and found increased expression levels of neuroendocrine markers in the enzalutamide-resistant LNCaP human prostate cancer (CaP) cell line when compared to the parental cell line. Subsequent studies demonstrated that Transcription Factor-4 (TCF4), a transcription factor implicated in WNT signaling, mediated neuroendocrine differentiation (NED) in response to enzalutamide treatment and was elevated in the enzalutamide-resistant LNCaP. In addition, we observed that PTHrP mediated enzalutamide resistance in tissue culture and inducible TCF4 overexpression resulted in enzalutamide-resistance in a mouse xenograft model. Finally, small molecule inhibitors of TCF4 or PTHrP partially reversed enzalutamide resistance in CaP cells. When tissues obtained from men who died of metastatic CaP were examined, a positive correlation was found between the expression levels of TCF4 and PTHrP. Taken together, the current results indicate that TCF4 induces enzalutamide resistance via NED in CaP.

Aims/hypothesis Common genetic variations of the transcription factor 7-like 2 gene (encoded by TCF7L2 ), one of the T cell factor/lymphoid enhancer-binding factor transcription factors for the converging wingless-type MMTV integration site family (Wnt)/β-catenin signalling pathway, are known to be associated with type 2 diabetes. Individuals with at-risk alleles of TCF7L2 exhibit impaired insulin secretion. Although previous studies using animal models have revealed the existence of a relationship between the Wnt/β-catenin signalling pathway and glucose homeostasis, it remains unclear whether TCF7L2 in the pancreatic beta cells might be causally involved in insulin secretion in vivo. In this study, we investigated the role of TCF7L2 expressed in the pancreatic beta cells in glucose homeostasis. Methods Three independent groups of genetically engineered mice (DN mice) were generated, in which expression of the dominant-negative form of Tcf7l2 was driven under a rat insulin promoter. Phenotypes of both adult and newborn mice were evaluated. The levels of genes and proteins expressed in isolated islets were determined by reverse transcription-quantitative PCR and western blot analysis, respectively. Results Adult DN mice showed impaired glucose tolerance and decreased insulin secretion in both oral and intraperitoneal glucose tolerance tests. Marked reduction of the beta cell area and whole-pancreas insulin content was observed in both the adult and newborn DN mice. Islets from the DN mice showed decreased gene expressions of Ccnd1 , Ccnd2 , Irs1 , Irs2 , Ins1 , Ins2 and Mafa , consistent with the deleterious effects of the dominant-negative form of Tcf7l2 on beta cell proliferation and insulin production. Conclusions/interpretation TCF7L2 expressed in the pancreatic beta cells plays a crucial role in glucose metabolism through regulation of the beta cell mass.

Aims/hypothesis Individuals carrying type 2 diabetes risk alleles in TCF7L2 display decreased beta cell levels of T cell factor 7 like-2 (TCF7L2) immunoreactivity, and impaired insulin secretion and beta cell sensitivity to glucagon-like peptide 1 (GLP-1). Here, we sought to determine whether selective deletion of Tcf7l2 in mouse pancreas impairs insulin release and glucose homeostasis. Methods Pancreas-specific Tcf7l2 -null ( pTcf7l2 ) mice were generated by crossing mice carrying conditional knockout alleles of Tcf7l2 ( Tcf7l2 -flox) with mice expressing Cre recombinase under the control of the Pdx1 promoter ( Pdx1 . Cre ). Gene expression was assessed by real-time quantitative PCR and beta cell mass by optical projection tomography. Glucose tolerance, insulin secretion from isolated islets, and plasma insulin, glucagon and GLP-1 content were assessed by standard protocols. Results From 12 weeks of age, pTcf7l2 mice displayed decreased oral glucose tolerance vs control littermates; from 20 weeks they had glucose intolerance upon administration of glucose by the intraperitoneal route. pTcf7l2 islets displayed impaired insulin secretion in response to 17 (vs 3.0) mmol/l glucose (54.6 ± 4.6%, p  < 0.01) or to 17 mmol/l glucose plus 100 nmol/l GLP-1 (44.3 ± 4.9%, p  < 0.01) compared with control islets. Glp1r (42 ± 0.08%, p  < 0.01) and Ins2 (15.4 ± 4.6%, p  < 0.01) expression was significantly lower in pTcf7l2 islets than in controls. Maintained on a high-fat (but not on a normal) diet, pTcf7l2 mice displayed decreased expansion of pancreatic beta cell volume vs control littermates. No differences were observed in plasma insulin, proinsulin, glucagon or GLP-1 concentrations. Conclusions/interpretation Selective deletion of Tcf7l2 in the pancreas replicates key aspects of the altered glucose homeostasis in human carriers of TCF7L2 risk alleles, indicating the direct role of this factor in controlling beta cell function.

Sequencing of primary colorectal tumors has identified a gene fusion in approximately 3% of colorectal cancer patients of the VTI1A and TCF7L2 genes, encoding a VTI1A-TCF4 fusion protein containing a truncated TCF4. As dysregulation of the Wnt signaling pathway is associated with colorectal cancer development and progression, the functional properties and transcriptional regulation of the VTI1A-TCF4 fusion protein may also play a role in these processes. Functional characteristics of the VTI1A-TCF4 fusion protein in Wnt signaling were analyzed in NCI-H508 and LS174T colon cancer cell lines. The NCI-H508 cell line, containing the VTI1A-TCF7L2 fusion gene, showed no active Wnt signaling, and overexpression of the VTI1A-TCF4 fusion protein in LS174T cells along with a Wnt signaling luciferase reporter plasmid showed inhibition of activity. The transcriptional regulation of the VTI1A-TCF4 fusion gene was investigated in LS174T cells where the activity of the VTI1A promoter was compared to that of the TCF7L2 promoter, and the transcription factor CDX2 was analyzed for gene regulatory activity of the VTI1A promoter through luciferase reporter gene assay using colon cancer cell lines as a model. Transfection of LS174T cells showed that the VTI1A promoter is highly active compared to the TCF7L2 promoter, and that CDX2 activates transcription of VTI1A. These results suggest that the VTI1A-TCF4 fusion protein is a dominant negative regulator of the Wnt signaling pathway, and that transcription of VTI1A is activated by CDX2.

Tcf7l2 mediates Wnt/β-Catenin signalling during development and is implicated in cancer and type-2 diabetes. The mechanisms by which Tcf7l2 and Wnt/β-Catenin signalling elicit such a diversity of biological outcomes are poorly understood. Here, we study the function of zebrafish tcf7l2 alternative splice variants and show that only variants that include exon five or an analogous human tcf7l2 variant can effectively provide compensatory repressor function to restore eye formation in embryos lacking tcf7l1a/tcf7l1b function. Knockdown of exon five specific tcf7l2 variants in tcf7l1a mutants also compromises eye formation, and these variants can effectively repress Wnt pathway activity in reporter assays using Wnt target gene promoters. We show that the repressive activities of exon5-coded variants are likely explained by their interaction with Tle co-repressors. Furthermore, phosphorylated residues in Tcf7l2 coded exon5 facilitate repressor activity. Our studies suggest that developmentally regulated splicing of tcf7l2 can influence the transcriptional output of the Wnt pathway.