The Effect of Bariatric Surgery on Hepatic Metabolism in Non-Alcoholic Fatty Liver Disease

Bariatric surgery is one of the few currently available treatment options for non-alcoholic fatty liver disease (NAFLD). In most cases, NAFLD is entirely ameliorated after the surgery but in some individuals, the disease may persist or even progress. The mechanisms underlying the bariatric surgery-mediated resolution of NAFLD and the heterogeneity in the response remain poorly understood. In this study, the investigators will examine the metabolic effects of bariatric surgery-induced resolution of NAFLD. To this end, study subjects who have previously undergone bariatric surgery and metabolic studies will be invited for a follow-up visit for physical examination, evaluation of body composition with bioelectrical impedance and quantification of liver stiffness using non-invasive transient elastography and magnetic resonance elastography (MRE). Body fat composition will be evaluated by magnetic resonance imaging (MRI) and hepatic lipid content will be measured with magnetic resonance spectroscopy (MRS). In addition, 1H nuclear magnetic resonance (NMR) metabolomic analyses will be carried out from plasma samples collected both before and after bariatric surgery. Insulin resistance will be assessed using the HOMA-IR index and the genotypes in disease-modifying genes including PNPLA3, TM6SF2, MBOAT7, MARC1 and HSD17B13 will be assessed. Liver biopsies were obtained at the time of bariatric surgery and, in individuals with a clinical indication, a follow-up liver biopsy will be obtained.