Intracellular Nicotinamide Phosphoribosyltransferase Protects against Hepatocyte Apoptosis and Is Down-Regulated in Nonalcoholic Fatty Liver Disease

Context: Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in Western and non-Western countries, but its pathogenesis is not fully understood. Objective: Based on the role of nicotinamide phosphoribosyltransferase (NAMPT) in fat and glucose metabolism and cell survival, we hypothesized a role for NAMPT/visfatin in the pathogenesis of NAFLD-related disease. Design and Setting: We conducted clinical studies at a referral medical center in well-characterized NAFLD patients (n = 58) and healthy controls (n = 27). In addition we performed experimental in vitro studies in hepatocytes. Main Outcome Measures: We examined 1) the hepatic and systemic expression of NAMPT/visfatin in patients with NAFLD and control subjects, 2) the hepatic regulation of NAMPT/visfatin, and 3) the effect of NAMPT/visfatin on hepatocyte apoptosis. Results: Our main findings were as follows. 1) Patients with NAFLD had decreased NAMPT/visfatin expression both systemically in serum and within the hepatic tissue, wi...