Unlike previously reported T2D risk loci, which predominantly associate with impaired beta cell function, the C allele of rs2943641 was associated with insulin resistance and hyperinsulinemia in 14,358 French, Danish and Finnish participants from population-based cohorts; this allele was also associated with reduced basal levels of IRS1 protein and decreased insulin induction of IRS1-associated phosphatidylinositol-3-OH kinase activity in human skeletal muscle biopsies.
Chronic hyperglycemia, independent of plasma lipid levels, is sufficient for the loss of beta-cell differentiation and secretory function in the db/db mouse model of diabetes.
Of these, the gene encoding insulin receptor substrate-1 (IRS-1), the protein product of which has been previously reported to be decreased, missing, altered, or defective in persons with type 2 diabetes mellitus, was evaluated by real time quantitative PCR to corroborate the array data.
Furthermore, S1043Y and C1095Y are not common IRS-1 polymorphisms as they were detected only in 1/136 choromosomes from NIDDM patients (allele frequency in NIDDM patients = 0.0007) and in 0/120 chromosomes from control subjects.
Chronic hyperglycemia, independent of plasma lipid levels, is sufficient for the loss of beta-cell differentiation and secretory function in the db/db mouse model of diabetes.
Analysis of the phenotypes showed that patients with NIDDM who had IRS-1 variants did not differ in their degree of insulin resistance compared with patients without known IRS-1 polymorphisms.