REGULATION OF FFA METABOLISM IN NORMAL AND DIABETIC MAN

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This research will continue in the area of regulation of lipolysis and free fatty acid oxidation in humans. An extremely precise and accurate high performance liquid chromatographic method for the determination of plasma palmitate concentration and specific activity has been developed and its accuracy validated. The proposed studies will systematically investigate the hormonal and substrate factors which regulate lipolysis and free fatty acid oxidation, using the "pancreatic clamp" technique. While extensive in vitro information on this subject is available, the hormone and substrate factors which regulate the mobilization and oxidation of free fatty acids remain to be determined. The proposal will focus initially on the dose-response relationship between insulin availability and free fatty acid mobilization and oxidation during infusion of insulin at rates which will achieve circulating plasma concentrations between 5 and 50 Mu/ml. On the basis of the results from these experiments, an insulin infusion rate will be selected for subsequent studies to independently assess the effects of graded hyperglycemia and incremental increases, within the physiologic range, of epinephrine, growth hormone, glucagon and cortisol in normal subjects and insulin- dependent diabetics. Specifically, these studies will 1) determine whether the sensitivity and/or responsiveness of lipolysis and free fatty acid oxidation is reduced in poorly controlled insulin- dependent diabetes; 2) determine whether hyperglycemia per se inhibits lipolysis and/or free fatty acid oxidation in normal and diabetic man; 3) determine whether the sensitivity and responsiveness of lipolysis and free fatty acid oxidation to epinephrine is normal or increased in poorly controlled diabetes; 4) determine whether growth hormone excess increases lipolysis and free fatty acid oxidation in normal and diabetic man; 5) determine whether glucagon stimulates lipolysis and free fatty acid oxidation in normal and diabetic man; and 6) determine whether hypercortisolemia increases lipolysis in normal subjects and patients with poorly controlled diabetes. These studies will provide new insights into the control of free fatty acid metabolism in vivo and will lead to additional studies of the effect of substrate and hormonal interactions in the regulation of fuel metabolism in man.