Objective: Common variants in PPARG, KCNJ11, TCF7L2, SLC30A8, HHEX, CDKN2A, IGF2BP2, and CDKAL1 genes have been shown to be associated with type 2 diabetes in European populations by genome-wide association studies. We have studied the association of common variants in these eight genes with type 2 diabetes and related traits in Indians by combining the data from two independent case-control studies.
Research design and methods: We genotyped eight single nucleotide polymorphisms (PPARG-rs1801282, KCNJ11-rs5219, TCF7L2-rs7903146, SLC30A8-rs13266634, HHEX-rs1111875, CDKN2A-rs10811661, IGF2BP2-rs4402960, and CDKAL1-rs10946398) in 5,164 unrelated Indians of Indo-European ethnicity, including 2,486 type 2 diabetic patients and 2,678 ethnically matched control subjects.
Results: We confirmed the association of all eight loci with type 2 diabetes with odds ratio (OR) ranging from 1.18 to 1.89 (P = 1.6 x 10(-3) to 4.6 x 10(-34)). The strongest association with the highest effect size was observed for TCF7L2 (OR 1.89 [95% CI 1.71-2.09], P = 4.6 x 10(-34)). We also found significant association of PPARG and TCF7L2 with homeostasis model assessment of beta-cell function (P = 6.9 x 10(-8) and 3 x 10(-4), respectively), which looked consistent with recessive and under-dominant models, respectively.
Conclusions: Our study replicates the association of well-established common variants with type 2 diabetes in Indians and shows larger effect size for most of them than those reported in Europeans.