p38 Mitogen-Activated Protein Kinase: A Critical Node Linking Insulin Resistance and Cardiovascular Diseases in Type 2 Diabetes Mellitus

Type 2 diabetes is associated with insulin resistance, endothelial dysfunction and accelerated atherosclerotic diseases. Though underlying mechanisms remain to be unraveled, p38 mitogen-activated protein kinase (MAPK) appears to play important roles in their pathogenesis. As a member of the MAPK family, it regulates the activities of many transcription factors and proteins/enzymes and thus has a wide-spectrum of biological effects. Patients with insulin resistance and/or type 2 diabetes have high levels of plasma free fatty acids, inflammatory cytokines, and/or glucose, and overactivation of the cardiovascular renin-angiotensin system, all are capable of activating p38 MAPK. p38 MAPK plays a central role in hepatic glucose and lipid metabolism, leading to increased hepatic glucose production and decreased hepatic lipogenesis. The roles of p38 MAPK in insulin-mediated glucose uptake in skeletal muscle and adipose tissue remain controversial. p38 MAPK also mediates inflammatory processes and cell apoptosis. Recent evidence suggests that p38 MAPK may be the key node linking cardiovascular insulin resistance, endothelial dysfunction and the pathogenesis of atherosclerotic diseases through its influences on monocytes/macrophages, vascular endothelial cells, and vascular smooth muscle cells in type 2 diabetes. In addition, p38 MAPK also contributes significantly to cardiac injury during ischemiareperfusion. Keywords: p38 MAPK, gluconeogenesis, lipogenesis, insulin resistance, diabetes, cardiovascular complications