IRS1 and Insulin resistance: We chose the Gly972Arg and Ala513Pro variants of the IRS-1 gene for investigation, because these specific allelic variants are located near the Tyr-Met-X-Met (YMXM) motifs around Tyr987 and Tyr612 and because these variants have been reported to influence insulin resistance, hyperinsulinemia and fatty-acid composition of muscles with a non-sporadic prevalence [7,10,14].