The Effect of Physical Activity on the Liver and the Heart's Metabolism of Fatty Acids in Obese With and Without NAFLD

Non-alcoholic fatty liver disease (NAFLD) covers a spectrum from reversible hepatic steatosis to inflammation and fibrosis termed steatohepatitis (NASH) and cirrhosis. New evidence indicates that NAFLD is associated with development of heart failure, abnormal ventricular glucose and fatty acid (FA) utilisation and cardiosteatosis. The mechanisms behind cardiac involvement and the progression from NAFLD to NASH are poorly understood but must include altered cardiac and intrahepatic lipid handling. In collaboration with renowned research groups from Oxford, Mayo Clinic and Copenhagen investigators plan comprehensive kinetic studies of heart and liver FA uptake and oxidation, ventricular function and substrate utilisation, and hepatic triglyceride (TG) secretion in order to assess mechanisms governing cardiac and hepatic lipid and glucose trafficking in subjects with NAFLD and NASH and the relationship with heart function. In addition, the investigators will assess skeletal muscle and adipose tissue enzyme activities, gene expression and protein concentrations in these subjects to define mechanisms involved in the cross-talk between heart, liver, muscle and adipose tissues. Investigators will address these questions using innovative tracer techniques (11Cpalmitate, 11C acetate, 18FDG glucose PET tracers and TG tracers) in combination with hepatic vein catherisation to study cardiac and liver substrate trafficking, as well as NMR spectroscopy, echocardiography, muscle and fat biopsies in combination with state-of-the art muscle and adipose tissue enzyme kinetics, gene- and protein expression. Effects of acute exercise will be assessed. The overarching goals are to define abnormalities and differences between NAFLD and NASH in hepatic lipid (FA and TG) metabolism and to assess the effect of exercise on both hepatic, cardiac and adipose and skeletal muscle lipid and substrate utilisation.