Sex-specific interactions between the IRS1 polymorphism and intakes of carbohydrates and fat on incident type 2 diabetes.

Background: The minor T allele of rs2943641 near the gene encoding for insulin receptor substrate I (IRS1) has been associated with decreased risk of type 2 diabetes (T2D) and adiposity in genome-wide association studies. Dietary intake can influence the regulation of IRS1, and studies have indicated sex-specific associations between IRS1 and adiposity. Objective: The objective was to examine the interaction between IRS1 rs2943641 and macronutrient intakes on incident T2D and percentage body fat in the Malta6 Diet and Cancer cohort. Design: The study included 15,227 women and 9614 men aged 4574 y without prevalent diabetes. Dietary data were collected with a modified diet history method. During 12 y of follow-up, 1567 incident T2D cases were identified. Results: The T allele was associated with lower incidence of T2D (P-trend = 0.003) and, in men, with higher percentage body fat (P-trend = 0.00002). We observed 3-way interactions between sex, rs2943641, and carbohydrate intake (P = 0.01) as well as between sex, rs2943641, and fat intake (P = 0.01) on incident T2D. Among women, the T allele was associated with decreased risk only in the lower tertiles of carbohydrate intake (P-trend = 0.01, P-interaction = 0.01). In contrast, among men, the T allele was associated with decreased risk in the lowest tertile of fat intake (P-trend = 0.0l, P-interaction = 0.02). No interaction was observed between macronutfient intakes and rs2943641 on percentage body fat. Conclusions: Our results indicate that IRS1 rs2943641 interacts with carbohydrate and fat intakes on incident T2D in a sex-specific fashion. A protective association between the rs2943641 T allele and T2D was restricted to women with low carbohydrate intake and to men with low fat intake. [ABSTRACT FROM AUTHOR]