Obesity and type 2 diabetes mellitus (T2DM) are two devastating diseases that are growing in prevalence to epidemic proportions. Both are associated with significant levels of morbidity and mortality; they are leading causes of non-alcoholic fatty liver disease, blindness, kidney failure and non-traumatic amputations, and these patients are also at increased risk for cardiovascular disease. Additionally, obesity and T2DM cause significant emotional strain on the patient and their loved ones, and account for hundreds of billions of dollars in health care expenditures each year. Two hallmarks of obesity are dyslipidemia and insulin resistance (IR), which strongly predispose to the development of T2DM. However, the biochemical and molecular mechanisms that cause decreased insulin action and the metabolic disturbances seen in obesity remain incompletely understood. Recent work has implicated increased inflammation, specifically elevated macrophage numbers and activity. In this project, we aim to determine the role of not only macrophages, but other cells of innate immunity, e.g. dendritic cells, in the molecular pathogenesis of obesity. We will be concentrating on changes in the liver, since the liver is a critical modulator of systemic carbohydrate and lipid metabolism, is a primary target of insulin, has its own extensive, resident immune system, and becomes engorged with fat in the setting of obesity (i.e. non-alcoholic fatty liver disease). To study the effects of immune cells on liver metabolism, we will be utilizing a co-culture system which allows us to maintain primary hepatocytes in close proximity to, but preventing direct contact with, mononuclear cells. We will investigate the effects of liver macrophages (Kupffer cells) and dendritic cells on hepatocyte lipid metabolism and insulin action and determine the mechanisms of these effects. Current treatment regimens for T2DM aim to lower serum glucose levels but do not address the concomitant inflammation. This research will help elucidate the pathophsyiologic steps leading to the development of IR and T2DM. Better mechanistic knowledge will allow the development of new treatments, which may not only reduce the severity of disease but also prevent the development of IR and T2DM in obese individuals. Therapy aimed at preventing the onset or reversing the cause of T2DM would most likely decrease morbidity and mortality and improve patients' quality of life. PUBLIC HEALTH RELEVANCE: The prevalence of obesity and type II diabetes (diabesity), and attendant metabolic abnormalities including dyslipidemia, insulin resistance, and steatosis has reached near epidemic proportions in western societies. The recent identification of inflammation as a contributory mechanism to these metabolic abnormalities has opened up new opportunities for increasing our understanding of the pathogenesis of diabesity and the development of treatments. The completion of the work program detailed in this proposal has the potential to influence both of these areas.