The purpose of the proposed studies is to better understand the regulatory mechanisms which are involved in modulating the function of lipid transfer protein (LTP). This enzyme facilitates the net mass transfer of neutral lipids among lipoprotein particles, and hence has an important role in shaping plasma lipoproteins. The focus of this proposal is to examine the role of insulin in the control and regulation of LTP activity and production. The studies proposed here will be conducted in a unique human population that is comprised of morbidly obese patients with or without NIDDM. These patients are referred to the Department of Surgery for gastric bypass surgery for weight loss. The effects of insulin on LTP activity and production will be examined in vivo and in vitro. In the in vivo studies, LTP activity and levels will be determined in insulin responsive and insulin resistant (NIDDM & IGT) morbidly obese patients, and in lean normoglycemic controls under conditions which result in higher plasma insulin levels. This includes alimentary lipemia, an oral glucose tolerance test, and a hyperinsulinemic, euglycemic clamp. The effects of insulin on LTP will also be considered under conditions which result in improvement in insulin sensitivity such as dietary weight loss and gastric by-pass surgery. The in vitro experiments will examine the effects of insulin and other modulators on LTP production at the transcriptional, translational and post translational levels, in liver slices and isolated adipocytes from insulin responsive lean and morbidly obese patients with and without NIDDM. In addition, in vivo and in vitro studies will be done with a group of morbidly obese patients with NIDDM, who will be exercise trained in order to improve their sensitivity to insulin. Tissues will be obtained from these patients after training and during gastric bypass surgery. These studies will provide new and needed information on the regulation of LTP. They are feasible because of the availability of human tissues, the methodologies needed for the studies, and the expertise to do the experiments. By understanding the regulation of LTP, a better understanding of its role in early atherogenesis may be achieved. The objectives of these studies are within the overall objectives of the ongoing studies of this laboratory, which are aimed at a better understanding of the causes of the increased incidence of heart disease in NIDDM.
