Insulin signaling pathways in chronic diseases

Insulin is an important physiological anabolic agent known, for enhancing the synthesis and storage of lipids, carbohydrates, and protein, and preventing their breakdown and liberation into circulation. It plays an important role in cell nutrient uptake, usage, and storage. Insulin resistance is the main characteristic of type 2 diabetes; it is a condition where cells fail to adequately respond to insulin. It is caused by different alterations, including a decrease in the number of insulin receptors and their catalytic activity, increased Ser/Thr phosphorylation, an increase in Tyr phosphatase activity, mainly PTP-1B, which causes receptor and IRS dephosphorylation, a decrease in PI3K and Akt kinases activity, and defects in GLUT-4 expression and function.