Novel Mechanisms Underlying the Inflammatory Effects of Leptin and Low Dose Endotoxin

Obesity over the last several has become a major health concern in our country as well as the world. Obesity is also one of the risk factors which lead to several inflammatory complications such as diabetes, artherosclerosis, etc. Two leading factors involved in the causes of inflammatory complications include leptin and low dose endotoxin lipopolysaccharide (LPS). However, the mechanism underlying the involvement of these two mediators is not clearly understood. The purpose of this study is to understand the mechanism underlying inflammatory complications caused by leptin and low dose endotoxin most recently coined metabolic endotoxemia. Interleukin-Receptor Associated Kinase 1 (IRAK-1) is an intracellular signaling component shown to activate NFκB which leads to the induction of proinflammatory mediators. Deletion of IRAK-1 in mice has beneficial effects in alleviating inflammatory complications and human variations in IRAK-1 gene are correlated with higher risks for inflammatory diseases. Therefore, we hypothesized that IRAK-1 is critically involved for the induction of proinflammatory mediators induced by leptin and low dose LPS. IL-6 mRNA levels were measured in THP-1 (human monocytic cells) and wild type and IRAK-deficient bone marrow derived macrophages (BMDM) challenged with different combinations of leptin and LPS. Data shows that leptin alone will not induce inflammatory mediators. However, increased induction of IL-6 was observed in a synergistic manner involving