Association and interaction analyses of genetic variants in ADIPOQ, ENPP1, GHSR, PPARγ and TCF7L2 genes for diabetic nephropathy in a Taiwanese population with type 2 diabetes

Background. Diabetic nephropathy (DN) is a common microvascular complication of diabetes. In this study, we aimed to explore both primary effects of single-locus and multilocus interactions to test the hypothesis that the type 2 diabetes (T2D) genes may contribute to the aetiology of DN in T2D independently and/or through complex interactions in a Taiwanese population with T2D. Methods. We genotyped six single nucleotide polymorphisms (SNPs) for five common T2D genes including adiponectin, C1Q and collagen domain containing (ADIPOQ), ectonucleotide pyrophosphatase/ phosphodiesterase 1 (ENPP1), growth hormone secretagogue receptor (GRSR), peroxisome proliferator-activated receptor gamma (PPAR gamma) and transcription factor 7-like 2 (TCF7L2). There were 216 T2D patients diagnosed with DN and 178 age-similar T2D without DN (control) subjects. To investigate gene-gene interactions, we employed both generalized multifactor dimensionality reduction (GMDR) method and logistic regression models. Results. Single-locus analyses showed significant main effects of ENPP1 (P = 0.0032; adjusted OR = 1.85; 95% CI = 1.17-2.92) on the risk of DN in T2D. Furthermore, a potential gene-gene interaction involving ENPP1 and GHSR was suggested in the best two-locus GMDR model (P = 0.021). The significant three-locus GMDR model (P < 0.001) was also identified among ADIPOQ, GHSR and TCF7L2. Analyses using logistic regression models confirmed the gene-gene interactions. Conclusions. The results suggest that the SNPs from the T2D-related genes may contribute to the risk of DN in T2D independently and/or in an interactive manner in Taiwanese T2D patients.