Association of TCF7L2 and GCG Gene Variants with Insulin Secretion, Insulin Resistance, and Obesity in New-onset Diabetes

This cohort study was designed to evaluate the association of transcription factor 7-like 2 (TCF7L2) and proglucagon gene (GCG) variants with disordered glucose metabolism and the incidence of type 2 diabetes mellitus (T2DM) in a rural adult Chinese population. A total of 7,751 non-T2DM participants ≥18 years old genotyped at baseline were recruited. The same questionnaire interview and physical and blood biochemical examinations were performed at both baseline and follow-up. During a median 6 years of follow-up, T2DM developed in 227 participants. After adjustment for potential contributory factors, nominally significant associations were seen between TT genotype and the recessive model of TCF7L2 rs7903146 and increased risk of T2DM [hazard ratio (HR)=4.068, 95% confidence interval (CI): 1.270-13.026; HR=4.051, 95% CI: 1.268-12.946, respectively]. The TT genotype of rs7903146 was also significantly associated with higher fasting plasma insulin level and the homeostasis model assessment of insulin resistance in case of new-onset diabetes. In addition, the TCF7L2 rs290487 TT genotype was associated with abdominal obesity and the GCG rs12104705 CC genotype was associated with both general obesity and abdominal obesity in case of new-onset diabetes.