Increasing evidence supports important roles for subacute inflammation in the pathogenesis of insulin resistance and type 2 diabetes. Epidemiological studies associate obesity and insulin resistance with a broad range of adipose-derived inflammatory markers, and biochemical and physiological studies suggest that adipose tissue-derived cytokines and chemokines may act as mediators. Recent discoveries also link macrophages in adipose tissue (ATMs) to the development of obesity-induced inflammation and the pathogenesis of insulin resistance. Given the similarities between acute inflammatory processes in host defense and the chronic inflammation seen in obesity, I have asked whether we might use the rich knowledge base for acute inflammation to learn more about obesity-induced insulin resistance. The generation of pro- and anti-inflammatory lipid mediators is a broad area of acute inflammation that has been incompletely studied and underappreciated in obesity research. A wide variety of endogenous lipids either promote (e.g. eicosanoids, prostaglandins) or help to resolve (e.g. resolvins, lipoxins) acute inflammatory responses. I hypothesize that lipid mediators in adipose tissue may also have roles in the pathogenesis of obesity-induced insulin resistance. To test this, I plan to analyze bioactive lipids in intact adipose tissue and component cell types of special interest: adipocytes and two populations of ATMs, those that are lipid-rich (foam cells) or lipid-poor (typical). We have recruited the assistance of a world leader in lipidomic analyses to assist us and help guide my studies. The methods we plan to use include FACS-based purification of homogenous ATM subtypes, and gas and liquid chromatography-based mass spectrometry (LC-UV MS/MS and GC-MS) coupled with a computer-based automated system equipped with databases and novel searching algorithms for mediator profiling. Once mediators are identified, I will test their activities on cultured 3T3-L1 adipocytes (e.g. insulin-signaling and insulin-stimulated glucose uptake) and both cultured RAW cells and isolated macrophages (e.g. NF-?? and target gene activation). ? ? PUBLIC HEALTH REVELANCE: The studies outlined in this proposal provide a non-biased approach to identifying lipid mediators potentially involved in the development of insulin resistance. My approach should not only identify potential mediators but also new mechanisms for cross-talk between adipocytes and macrophages that may contribute to the development of obesity-induced insulin resistance. ? ? ? ?
