In vivo hyperglycemia/hyperinsulinemia in rats for 48 hours similarly resulted in activation of PKC-ζ and increased phosphorylation of IRS-1 Ser318 and Akt Thr34.
In obesity and type 2 diabetes, selective downregulation of Irs2 and its downstream actions to cause reduced insulin actions was associated with increased insulin actions through Irs1 in variety tissues.
Additionally, TBF treatment significantly reduced phosphorylation of insulin receptor substrate 1 (IRS-1) at serine 307 and increased insulin-stimulated Akt/eNOS activation in the SHRs.
We characterised expression of IR-related molecules, IRS-1 phosphorylation and downstream signalling in a panel of 5 colon cancer cell lines at different insulin exposures: 15 min (100 nM), approximating to acute stimulation; 48 h (100 nM), used to demonstrate adaptive changes; and 12 weeks (20 nM; chronic insulin exposure, CIE), approximating to chronic hyperinsulinaemia.
We show that Igf1r/Irs1 double mutants do not differ phenotypically from Irs1 single mutants and exhibit hyperinsulinemia, while maintaining normal β cell mass and glucose tolerance.
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.
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.
Allelic variants of genes encoding components of the insulin pathway, including insulin (INS), insulin receptor (INSR), and insulin receptor substrate-1 and insulin receptor substrate-2 (IRS1 and IRS2) have been associated with hyperinsulinemia and insulin resistance and may, therefore, predict susceptibility to colorectal neoplasia.
Insulin increasedinsulin receptor substrate 1 (IRS-1) tyrosine phosphorylation, IRS-1-associated phosphatidylinositol (PI) 3-kinase activity, and phosphorylation of Akt Ser473 and AS160, a newly described Akt substrate that plays a role in GLUT4 exocytosis, approximately 2.3 fold before treatment.
We conclude the following: 1) physiological hyperinsulinemia induces sustained activation of insulin-signaling molecules in human skeletal muscle; 2) the more distal insulin-signaling components (Akt, GSK-3) are activated much more rapidly than the proximal signaling molecules (IRTK as well as insulin receptor substrate 1 and phosphatidylinositol 3-kinase [Wojtaszewski et al., Diabetes 46:1775-1781, 1997]); and 3) prior exercise increases insulin stimulation of both glucose uptake and glycogen synthase activity in the absence of an upregulation of signaling events in human skeletal muscle.