Project Summary It is estimated that around 40% of the adult population of the United States is obese and thus at increased risk for several chronic illnesses. Current weight loss strategies for obese people are often ineffective and come with serious neurological side effects. This proposal aims to determine whether new strategies to treat and prevent obesity can be developed from current insights into biological aging. The transcription factor C/EBP-β regulates the expression of genes involved in fat catabolism and fat stores mobilization. Preliminary observations suggest that pro-longevity interventions, such as mTORC1 inhibition, prevent diet-induced obesity in mice and activate C/EBP-β. The nucleoside-analogue reverse-transcriptase inhibitor (NRTI) adefovir dipivoxil (ADV) also prevents diet-induced obesity and activates C/EBP-β, though independently of mTORC1 inhibition. Building on these premises, Aim 1 tests the hypothesis that activation of hepatic C/EBP-β leads to increased energy expenditure and fat catabolism, with net negative effects on weight and fat stores. Using transgenics and pharmacological approaches, we will determine the role of hepatic C/EBP-β in lipid metabolism and homeostasis in the face of obesogenic challenges and morbid obesity. State-of-the-art techniques will be applied to measure the impact of different isoforms of C/EBP-β on energy balance, glucose homeostasis, and endocrine regulation of glucose and lipid metabolism. Aim 2 sets out to determine whether mitohormetic stresses can increase lipid metabolism through activation of C/EBP-β. Using ADV and other mitochondrial stressors, we will measure activation of mitohormetic pathways and their connection with increased hepatic oxidation of fatty acids and energy expenditure. This proposal will be carried out in an institution with strong research programs in both aging and obesity/diabetes biology. The candidate will receive state of the art training in techniques and analytical tools necessary to the completion of both aims, including indirect calorimetry, insulin and glucose tolerance testing, and big data analysis. The candidate will also acquire an in-depth background in energy and nutrient homeostasis. Altogether, the experiments and training proposed will allow the candidate to build an independent and successful research program applying insights from geroscience to understand and investigate nutrient homeostasis, energy balance, and related metabolic disorders.