IRS1 and Insulin resistance: In 2009, a novel genetic variant rs2943641, which is located adjacent to the insulin receptor substrate 1 gene (IRS1), was shown to have a significant association with insulin resistance and hyperinsulinemia and further studies also showed that this variant is implicated in reduced basal IRS1 protein level and decreased IRS1-associated phosphatidylinositol-3-OH kinase activity in human skeletal muscle biopsies [21].