Mechanisms of Vascular Dysfunction in Acute Insulin Resistance

Boston University Medical Campus, Boston MA

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Abstract

Patients with syndromes of insulin resistance, including obesity, the Metabolic Syndrome, and Type[unreadable] 2 diabetes mellitus, have markedly increased risk for atherosclerosis. A growing body of work has shown[unreadable] that insulin contributes to the maintenance of vascular cell homeostasis and that local insulin resistance[unreadable] has pathological effects including loss of the bioactivity of endothelium-derived nitric oxide (NO) and[unreadable] conversion to a pro-inflammatory phenotype that may promote vascular remodeling and atherosclerosis.[unreadable] Insulin-mediated activation of nitric oxide synthase depends on Akt/PI3 kinase and the availability of[unreadable] mitochondria-derived reactive oxygen species. Recent studies suggest that these signaling mechanisms[unreadable] also depend on the activity of AMP-dependent protein kinase (AMP kinase). Our preliminary data indicate[unreadable] that a period of strict bed rest or short-term lipid infusion produces acute insulin resistance in healthy[unreadable] subjects that is associated with a marked impairment of vasodilator function. Use of this methodology[unreadable] provides a unique opportunity to investigate the vascular consequences of insulin resistance without the[unreadable] confounding factors present in patients with more advanced disease. This project will investigate[unreadable] potential mechanisms accounting for vascular dysfunction in these states of acute insulin resistance in[unreadable] humans. In Aim 1, we will test the hypothesis that activation of AMP kinase will blunt the adverse effects[unreadable] of insulin resistance on vascular function by measuring basal and stimulated AMP kinase activity in[unreadable] leukocytes and muscle and by determining whether vascular dysfunction is prevented by pretreatment[unreadable] with metformin, which activates AMP kinase and increases insulin sensitivity.. In Aim 2, we will[unreadable] investigate the contribution of mitochondrial dysfunction to vascular dysfunction in insulin resistance by[unreadable] measuring systemic markers of oxidative stress and mitochondrial membrane potential and ROS[unreadable] production in leukocytes. In addition, we will determine whether the mitochondria-directed antioxidants[unreadable] lipoic acid and acetyl-L-carnitine blunt vascular dysfunction and insulin resistance. In Aim 3, we will test[unreadable] the hypothesis that activation of NFicB contributes to the development of vascular dysfunction in acute[unreadable] insulin resistance by measuring circulating adhesion molecules, pro-inflammatory cytokines, and[unreadable] adipokines. In addition, we will determine whether vascular dysfunction can be prevented by treatment[unreadable] with sulfasalazine, which inhibits activation of NFkappaB. We suggest that these translational studies will[unreadable] provide new insights into the mechanisms of vascular dysfunction in patients with insulin resistance that[unreadable] will be relevant to the prevention and management of vascular disease in the setting of obesity, the[unreadable] metabolic syndrome, and Type 2 diabetes mellitus.