Association of genetic variants for susceptibility to obesity with type 2 diabetes in Japanese individuals

In populations of East Asian descent, we performed a replication study of loci previously identified in populations of European descent as being associated with obesity measures such as BMI and type 2 diabetes. We genotyped 14 single nucleotide polymorphisms (SNPs) from 13 candidate loci that had previously been identified by genome-wide association meta-analyses for obesity measures in Europeans. Genotyping was done in 18,264 participants from two general Japanese populations. For SNPs showing an obesity association in Japanese individuals, we further examined diabetes associations in up to 6,781 cases and 7,307 controls from a subset of the original, as well as from additional populations. Significant obesity associations (p < 0.1 two-tailed, concordant direction with previous reports) were replicated for 11 SNPs from the following ten loci in Japanese participants: SEC16B, TMEM18, GNPDA2, BDNF, MTCH2, BCDIN3D-FAIM2, SH2B1-ATP2A1, FTO, MC4R and KCTD15. The strongest effect was observed at TMEM18 rs4854344 (p = 7.1 x 10(-7) for BMI). Among the 11 SNPs showing significant obesity association, six were also associated with diabetes (OR 1.05-1.17; p = 0.04-2.4 x 10(-7)) after adjustment for BMI in the Japanese. When meta-analysed with data from the previous reports, the BMI-adjusted diabetes association was found to be highly significant for the FTO locus in East Asians (OR 1.13; 95% CI 1.09-1.18; p = 7.8 x 10(-10)) with substantial inter-ethnic heterogeneity (p = 0.003). We confirmed that ten candidate loci are associated with obesity measures in the general Japanese populations. Six (of ten) loci exert diabetogenic effects in the Japanese, although relatively modest in size, and independently of increased adiposity.