Sympathetic Control of Liver Metabolism in Exercise and Obesity

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PROJECT SUMMARY The prevalence of obesity and its complications, including diabetes and non-alcoholic fatty liver disease (NAFLD) are a significant health care crisis. These complication impact liver metabolism by dysregulating gluconeogenesis, lipid synthesis, mitochondrial function, and fat oxidation. NAFLD is improved by lifestyle interventions. Ironically, physical activity, exercise, and aerobic capacity affect many of these pathways similarly, but profoundly lower liver fat independent of weight loss. Hence, aerobic exercise is commonly prescribed therapy for NAFLD. One route by which obesity or exercise influence regulation of liver metabolism may be by signals through the sympathetic nervous system. The overarching goal of this 5-year research career development plan is to facilitate my transition from a technically focused researcher to a fully independent academic scientist investigating the in vivo physiology of disease. This will be accomplished by training in disciplines of physiology, neurophysiology, and exercise that will be used to identify mechanisms by which hepatic sympathetic nervous signaling controls liver metabolic flux during obesity and interventions. Elevated basal sympathetic signaling is thought to occur through the α1b adrenergic receptor (AR), which is highly expressed in mouse liver (including hepatocytes) and has been suggested to stimulate hepatic glucose production, breakdown of glycogen, gluconeogenesis, tricarboxylic acid (TCA) cycle and ketogenesis. This project focuses on understanding how hepatic α1b-AR contributes to dysregulated hepatic gluconeogenesis and fat oxidation during obesity and NAFLD (Aim 1), and the degree to which liver α1b-AR mediates beneficial effects of acute (Aim 2) or chronic exercise (Aim 3) as treatments of NAFLD. Using targeted metabolomics and stable isotope infusions, I will quantitatively evaluate how AR signaling regulates liver metabolism. The findings will advance our knowledge of how metabolism is altered by complications of obesity and provide a novel training platform for the recipient.