Genetic variation in GIPR influences the glucose and insulin responses to an oral glucose challenge

Abstract

Glucose levels 2 h after an oral glucose challenge are a clinical measure of glucose tolerance used in the diagnosis of type 2 diabetes. We report a meta-analysis of nine genome-wide association studies (n = 15,234 nondiabetic individuals) and a follow-up of 29 independent loci (n = 6,958-30,620). We identify variants at the GIPR locus associated with 2-h glucose level (rs10423928, Β (s.e.m.) = 0.09 (0.01) mmol/l per A allele, P = 2.0 × 10 15). The GIPR A-allele carriers also showed decreased insulin secretion (n = 22,492; insulinogenic index, P = 1.0 × 10 17; ratio of insulin to glucose area under the curve, P = 1.3 × 10 16) and diminished incretin effect (n = 804; P = 4.3 × 10 4). We also identified variants at ADCY5 (rs2877716, P = 4.2 × 10 16), VPS13C (rs17271305, P = 4.1 × 10 8), GCKR (rs1260326, P = 7.1 × 10 11) and TCF7L2 (rs7903146, P = 4.2 × 10 10) associated with 2-h glucose. Of the three newly implicated loci (GIPR, ADCY5 and VPS13C), only ADCY5 was found to be associated with type 2 diabetes in collaborating studies (n = 35,869 cases, 89,798 controls, OR = 1.12, 95% CI 1.09-1.15, P = 4.8 × 10 18).