Diabetes: ERK5 and Vascular Inflammation

点击翻译按钮获取中文摘要

Project Summary Rationale: Diabetes is epidemic in our society. Type-2 Diabetes Mellitus (T2DM) is a progressive pathology characterized by insulin resistance and hyperinsulinemia. Cardiovascular pathologies that are the sequelae of this disorder are the leading cause of morbidity and mortality in our Veteran population. Atherosclerosis is a major consequence of diabetes and one particular characteristic of atherosclerois is inflammation. Studies suggest that chronic insulin resistance and hyperinsulinemia contribute to atherogenesis by augmenting the effects of the inflammatory cytokines, thereby increasing the secretion of additonal inflammatory cytokines and expression of cellular adhesion molecules (CAMs). Tumor Necrosis Factor-alpha (TNF¿) activity has been shown to be linked to insulin resistance. Pathways that mediate the effects of TNF¿ may also regulate intracellular insulin signaling and thus correlated to atherogenesis. TNF¿ is known to increase the expression of vascular cell adhesion molecule-1 (VCAM-1). In contrast, insulin's role in atherogenesis is debated. Some contend that insulin stimulates the increase of nitric oxide (NO). Others argue that hyperinsulinemia increases the proliferaton of vascular cells and the inflammatory response. The question we asked here is, "does insulin dampen or augment the effects of TNF¿ on VCAM-1 expression and what mechanisms are attributed to these effects"? In vitro and in vivo animal model experiments have examined some of the signaling pathways that mediate CAM expression, but there is a significant gap in our understanding between identifying pathways and their molecular interactions or "cross talk" within cells and tissues in the presence of hyperinsulinemia and inflammatory cytokines. Significance: We are interested in determining the molecular mechanisms that regulate insulin and TNF¿ stimulation of VCAM-1 expression and thereby help define novel drug targets. These findings may provide healthcare strategies that will allay vascular inflammation and atherosclerosis in Veterans. We hypothesize - that in the state of metabolic insulin resistance hyperinsulinemia exaggerates the effects of TNF¿-associated inflammation via increased expression of VCAM-1. These effects are mediated in part by multiple signal pathways, in which ERK5 plays an important role in VCAM-1 expression, NF¿B activation and vascular inflammation. Goals of Research: To further our knowledge of vascular inflammation we plan to use the findings from the current proposal to advance our understanding of the molecular mechanisms of vascular inflammation by characterizing the roles of key players in insulin and TNF¿-stimulated VCAM-1 expression. Specific Aims: (1) Determine the role of kinase pathway crosstalk in hyperinsulinemia and TNF¿-stimulated increases in VCAM-1 expression. (2) Determine the role of ERK5 in hyperinsulinemia and TNF¿ stimulated increases in VCAM-1 expression. (3) Determine the role that hyprerinsulinemia plays in VCAM-1 expression in carotids of diabetic rats.