The rising incidence of obesity is implicated in increased health risks including cardiovascular disease and diabetes. However, the Diabetes Prevention Program has demonstrated that early treatment of insulin resistance can reduce progression to overt diabetes. Since insulin resistance is also an independent risk factor for cardiovascular disease, early treatment would provide additional benefit. Chromium picolinate is a dietary supplement that has been shown to improve insulin sensitivity in patients with type 2 diabetes mellitus. Since prevention of diabetes may be preferable to treatment, this proposal will concentrate on the effect of chromium supplementation in obese (BMI greater than 30) subjects with insulin resistance, but without overt diabetes. We have preliminary data demonstrating that chromium supplements improve insulin sensitivity in patients with both HIV disease and polycystic ovarian syndrome.
Specific Aim 1 of this proposal will examine the safety and efficacy of supplemental chromium picolinate in the treatment of insulin resistance in obesity-related insulin resistance. Quantitative improvements in insulin-mediated glucose disposal will be determined in a placebo-controlled study of chromium supplementation with 1000ug (19.2 umol) of chromium as chromium picolinate, over a 2-month course of therapy of subjects with glucose intolerance (defined with an oral glucose tolerance test, OGTT). Both safety (liver and renal function and oxidative stress) and efficacy (improved glucose disposal with a hyperinsulineminc, euglycemic clamp and insulin secretion, OGTT) will be evaluated. In vitro studies have demonstrated that chromium (as chromodulin) enhances the activity of the insulin receptor.
Specific Aim 2 will assess the mechanism by which chromium supplementation improves insulin action. Specifically, this aim will access changes in plasma free fatty acids, the ability of insulin to suppress lipolysis in adipose tissue, and insulin signaling in adipose tissue including the phosphorylation of insulin receptor substrate 1 and activity of downstream enzymes such as glycogen synthase kinase 3B. Thus, this research will document the therapeutic benefit of chromium supplementation for insulin resistance/glucose intolerance and will also provide a mechanistic framework to explain how chromium supplementation enhances insulin action. ? ?
