Non-alcoholic fatty liver disease (NAFLD) is the leading cause of liver disease in the United States. It spans a clinical spectrum from fatty liver to superimposed inflammation called NASH (non-alcoholic steatohepatitis). NASH predisposes to irreversible cirrhosis and hepatocellular carcinoma, which highlights the need to identify underlying mechanisms. In NAFLD, defective mitochondria liberate excess reactive oxygen species (ROS). Mitochondrial ROS is of interest, because it is implicated in insulin resistance and inflammation, two key features of NAFLD. The mechanism for mitochondrial dysfunction is unknown;hence, understanding its mechanistic basis may mitigate NAFLD. Our preliminary data indicate that LRP130 is an important regulator of mitochondrial function and ROS. In NAFLD, we observed that LRP130 is attenuated in a disease specific manner. Notably, depletion of LRP130 in mouse liver induced insulin resistance and inflammation. Mechanistically, LRP130 regulates the entire mitochondrial genome. Notably, LRP130 profoundly influences respiratory chain formation, respiration and superoxide formation. We hypothesize that LRP130 is a molecular link between defective mitochondria in liver and progression of NAFLD. We propose three Aims to query our hypothesis: (1) Evaluate the role of LRP130 in mitochondrial function and superoxide formation. The impact of LRP130 on mitochondrial bioenergetics will be evaluated using loss- and gain-of-function models in cells and mice. We will evaluate respiratory chain supercomplexes using blue native gel electrophoresis. Mitochondrial function will be measured by oxygen consumption, complex activity, membrane potential and superoxide measurements. (2) Evaluate the role of LRP130 in non-alcoholic fatty liver disease. Fatty liver will be induced by challenging mice with a high fat diet. Mice deficient for LRP130 in liver will be evaluated for insulin sensitivity and inflammation using a complement of assays: hyperinsulinemic-euglycemic clamp, immunodetection of insulin signaling, histological evaluation of inflammation and cytokine profiling. Parallel studies will be conducted with a liver specific LRP130 transgenic model. (3) Evaluate transcriptional and inflammatory control of LRP130. We hypothesize that cytokines attenuate transcription of LRP130, and may link cytokines to defective mitochondria and excess superoxide. We will use genetic studies, reporter assays and chromatin immunoprecipitation to test this hypothesis. Therapeutic manipulation of ROS in NAFLD is impeded by an insufficient understanding of basic mechanisms. Our novel findings on LRP130 will advance new paradigms on the role of mitochondria in NAFLD.
Obesity predisposes to heart disease, diabetes and fatty liver disease. Accumulation of fat in the liver may accelerate the development of heart disease and diabetes;hence, altering liver fat may be of therapeutic benefit. This proposal will investigate the role of a gene called LRP130 in fatty liver disease, and may provide new ways to treat diabetes and heart disease.
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