Association of HNF4α gene polymorphisms with susceptibility to type 2 diabetes

Genetic variants in promoter regions associated with type 2 diabetes mellitus: A large-scale meta-analysis and subgroup analysis

BACKGROUND

Promoter plays important roles in regulating transcription of genes. Association studies of genetic variants in promoter region with type 2 diabetes (T2D) risk have been reported, but most were limited to small number of individual genetic variants and insufficient sample sizes. In addition, the effect of study populations and demographic characteristics were often neglected.

METHODS

In this study, we conducted a large-scale meta-analysis and subgroup analysis of T2D associated genetic variants in the promoter regions to evaluate their contribution to the susceptibility in T2D. Alleles and genotypes from cohort or case-controlled studies were extracted for future study. Total 41 742 cases and 50 493 controls for three loci were involved in 70 articles.

RESULTS

Seventy case-controlled studies of three genes with 41 742 cases and 50 493 controls were included. Meta-analysis showed only rs266729 and rs17300539 of ADIPOQ, and rs1884613, rs2144908, and rs4810424 of HNF4A were significantly associated with T2D risk. Subgroup analysis showed that both rs266729 and rs17300539 of ADIPOQ were associated with the risk of T2D in Caucasian population, but only rs266729 of ADIPOQ in Asian population and rs2144908 in other population including multinational North American. For diagnostic criteria, rs266729 of ADIPOQ and rs2144908 of HNF4A were associated with T2D risk when WHO/ADA diagnostic criteria were used. For genotyping methods, both rs266729 of ADIPOQ and rs2144908 of HNF4A were associated with T2D risk when other than Taqman and Sequencing methods were used.

CONCLUSIONS

T2D was significantly associated with promoter rs266729, rs17300539, rs1884613, rs2144908, and rs4810424, and the association of T2D risk were affected by study population, diagnostic criteria, and genotype methods.

Genetic associations between Transcription Factor 7 Like 2 rs7903146 polymorphism and type 2 diabetes mellitus: a meta-analysis of 115,809 subjects

BACKGROUND

Some genetic association studies tried to investigate potential associations of Transcription Factor 7 Like 2 (TCF7L2) rs7903146 polymorphism with type 2 diabetes mellitus (T2DM). However, the results of these studies were not consistent. Thus, we performed the present meta-analysis to explore associations between TCF7L2 rs7903146 polymorphism and T2DM in a larger pooled population.

METHODS

Systematic literature research of PubMed, Web of Science and Embase was performed to identify eligible studies for pooled analyses. I² statistics were employed to assess between-study heterogeneities. If I² was greater than 50%, random-effect models (REMs) would be used to pool the data. Otherwise, fixed-effect models (FEMs) would be applied for synthetic analyses.

RESULTS

Totally 68 studies with 115,809 subjects were included for analyses. The pooled analyses showed that TCF7L2 rs7903146 (dominant model: p < 0.0001; recessive model: p < 0.0001; over-dominant model: p < 0.0001; allele model: p < 0.0001) polymorphism was significantly associated with susceptibility to T2DM in overall population. Further subgroup analyses revealed similar significant findings in both Asians and Caucasians.

CONCLUSIONS

In conclusion, our findings supported that TCF7L2 rs7903146 polymorphism could be used to identify individuals at high risk of developing T2DM in Asians and Caucasians.

Microbiota regulate intestinal epithelial gene expression by suppressing the transcription factor Hepatocyte nuclear factor 4 alpha

Microbiota influence diverse aspects of intestinal physiology and disease in part by controlling tissue-specific transcription of host genes. However, host genomic mechanisms mediating microbial control of intestinal gene expression are poorly understood. Hepatocyte nuclear factor 4 (HNF4) is the most ancient family of nuclear receptor transcription factors with important roles in human metabolic and inflammatory bowel diseases, but a role in host response to microbes is unknown. Using an unbiased screening strategy, we found that zebrafish Hnf4a specifically binds and activates a microbiota-suppressed intestinal epithelial transcriptional enhancer. Genetic analysis revealed that zebrafish hnf4a activates nearly half of the genes that are suppressed by microbiota, suggesting microbiota negatively regulate Hnf4a. In support, analysis of genomic architecture in mouse intestinal epithelial cells disclosed that microbiota colonization leads to activation or inactivation of hundreds of enhancers along with drastic genome-wide reduction of HNF4A and HNF4G occupancy. Interspecies meta-analysis suggested interactions between HNF4A and microbiota promote gene expression patterns associated with human inflammatory bowel diseases. These results indicate a critical and conserved role for HNF4A in maintaining intestinal homeostasis in response to microbiota.