This application addresses two hypotheses (1) that impaired AMPK activation predisposes adipose tissue of obese humans to inflammation and oxidative stress, which in turn can result in systemic insulin resistance and (2) that bariatric surgery reverses these and other abnormalities, at least in part by restoring AMPK activity. To test these hypotheses, it is our strategy to develop existing strengths in studying adipose tissue, AMPK and a closely related molecule SIRT1 at Boston University Medical Center (BUMC) and to integrate them with strengths in the clinical investigation of humans undergoing bariatric surgery at Eastern Carolina University (ECU). Our central hypothesis emanated from investigations by the BUMC group which demonstrated that AMPK in adipose tissue is activated by lipolysis and that inhibition of its activation by various means (in cultured 3T3L1 cells) leads to increases in oxidative stress and adhesion of mononuclear cells. This in turn led to a small study in markedly obese patients undergoing bariatric surgery that revealed AMPK activity is lower and the expression of inflammatory markers and chemokine receptors higher in adipose tissue of patients who were insulin resistant (70 percent of total). The proposed investigations are intended to confirm and extend these findings and to determine whether the observed abnormalities are reversed by bariatric surgery. In addition we will initiate studies with adipocytes taken from the two patient groups before and after surgery and appropriate controls, to determine how they are distinguished by such characteristics as lipolysis, oxidative and ER stress, gene expression, lipid droplet proteins and mitochondrial function. We will also determine in preliminary studies how in the adipocytes these parameters respond to AMPK and SIRT1 activators, and to incretins. Success in these endeavors will create the scientific and clinical infrastructure for a subsequent multi-investigator grant to study AMPK and SIRT1 in the setting of bariatric surgery in a joint effort by the two institutions

Public Health Relevance

The metabolic syndrome, sometimes referred to as obesity-induced insulin resistance (01R), is a major public health problem that predisposes patients to type 2 diabetes, atherosclerotic cardiovascular disease, hypertension and even certain cancers. An understanding of why it occurs in most, but not all, obese people and how it is reversed by bariatric surgery could have significant implications for its prevention and treatment.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Resource-Related Research Projects (R24)
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Special Emphasis Panel (ZDK1-GRB-N (J1))
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Laughlin, Maren R
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Boston Medical Center
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Xu, X Julia; Pories, Walter J; Dohm, Lynis G et al. (2013) What distinguishes adipose tissue of severely obese humans who are insulin sensitive and resistant? Curr Opin Lipidol 24:49-56