The TRIB3 Q84R polymorphism and risk of early-onset type 2 diabetes

CONTEXT: The prevalence of type 2 diabetes (T2D), particularly among young adults, has been rising steadily during the past 2 decades. T2D, especially in its early-onset subtype, is under genetic control. TRIB3 inhibits insulin-stimulated Akt phosphorylation and subsequent insulin action. A TRIB3 gain-of-function polymorphism, Q84R (rs2295490), impairs insulin signaling. OBJECTIVE: The objective of the study was to verify the association of TRIB3 Q84R with: 1) T2D, either subtyped or not according to age at diagnosis (early-onset, <45 yr, or >or= 45 yr); 2) insulin secretion and sensitivity in nondiabetic individuals; or 3) in vitro insulin secretion from isolated human islets. DESIGN: Four different case-control samples comprising a total of 5,469 whites were examined. Insulinogenic and insulin sensitivity indexes and their interplay (disposition index) were assessed in 645 nondiabetic individuals at oral glucose tolerance test, glucose (16.7 mmol/liter)-induced in vitro insulin secretion was assessed in islets isolated from 54 nondiabetic donors. RESULTS: In the whole sample, the R84 variant was nominally associated with T2D (odds ratio 1.17, 95% confidence interval 1.00-1.36, P = 0.04). When stratifying according to age of diabetes onset, R84 carriers had an increased risk of early-onset T2D (odds ratio 1.32, 95% confidence interval 1.10-1.58, P = 0.002). Among 645 nondiabetic subjects, R84 carriers had higher glucose levels (P = 0.005) and lower insulinogenic (P = 0.03) and disposition index (P = 0.02) during the oral glucose tolerance test. R84 islets were more likely to display relatively low glucose-stimulated insulin release (P = 0.04). CONCLUSIONS: The TRIB3 R84 variant is associated with early-onset T2D in whites. Alteration in the insulin secretion/insulin sensitivity interplay appears to underlie this association.