Allelic variation in exon 18 of the sulfonylurea receptor 1 (SUR1) gene, insulin secretion and insulin sensitivity in nondiabetic relatives of type 2 diabetic subjects.
Résumé
BACKGROUND: We have previously observed associations of the T-allele of the exon 18 variant (ACC --> ACT; Thr759Thr) of the sulfonylurea receptor 1 (SUR1) gene with type 2 diabetes mellitus (T2DM). Here we assess beta-cell function and insulin sensitivity in carriers of different genotypes at this locus. METHODS: Pre-hepatic insulin secretion rates (ISR) derived by deconvolution of circulating C-peptide levels, and glucose clearance were assessed during graded infusions of intravenous glucose in CC-homozygous (n=6) and CT-heterozygous (n=6) nondiabetic relatives of CT-heterozygous type 2 diabetic subjects. RESULTS: Average ISR over the duration of the study, adjusted for sex, age, BMI and prevailing glucose levels, were lower in CT-heterozygous subjects as compared with CC-homozygous subjects (3.91 +/- 0.40 vs. 4.84 +/- 0.28 pmol/kg x min(-1); p=0.048). The correlation curves relating ISR to glucose levels were significantly different in the two groups (analyses of covariance p=0.029). Glucose clearance was similar in both groups. CONCLUSIONS: Insulin secretion rates, but not insulin sensitivity, assessed during graded infusion of glucose were mildly decreased in nondiabetic relatives of type 2 diabetic subjects, who carry the at risk T-allele of exon 18 variant of the SUR1 gene. These results suggest that the at-risk allele might have a small effect on pancreatic B-cell function and contribute to the development of T2DM in these families.