LRH-1 and non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is an increasingly recognized health problem in the Western world, which affects up to 25% of the Western world population. For decades it was well recognized that choline enriched diet reduces and vice versa choline deficient diet results in fatty liver. However, the molecular mechanisms of these "lipotropic" effects of choline, remained largely obscure. Choline is mainly converted to phosphatidylcholine (PC) in the organism. Preliminary studies in the lab of Dr. Moore show that unusual PCs can act as activators of human and murine liver receptor homolog 1 (LRH-1), a nuclear receptor that is critically involved in several key pathways of bile acid, lipid, and glucose metabolism. Therefore, we hypothesize, that PC alleviates NAFLD by (i) altering central pathways of hepatic lipid homeostasis such as lipid, glucose and bile acid metabolism and (ii) that these effects may be at least in part mediated via LRH-1 signalling. To test this hypothesis, we will treat standard chow- fed and dietary-induced obese mice with fatty liver with various types of PC. Morphological changes, biochemical and molecular effects on bile acid, lipid and glucose metabolism will be studied with up-to-date technologies. The molecular basis for these effects will be studied at the genomic level by studying nuclear receptor DNA binding, and at the transcriptomic level using gene arrays. Furthermore, we will perform bioinformatic integration of these genomic and molecular studies with the results of gene arrays at the systems biology level to better understand physiologic regulation. To test in particular the hypothesis that the metabolic effects are mediated via LRH-1 signaling, we will again perform in vivo experiments using hepato-specific LRH-1 knockout mice treated with various types of PCs. Additional in vitro experiments using siRNA technology will test for LRH-1 specifity of transcriptional effects. Luciferase assays will be performed to test activation of LRH-1 by various phospholipids and to exclude activation of other nuclear receptors by these phospholipids. In addition, interaction of the transcription factor (i.e. LRH-1) with DNA will be investigated by either ChIP or the novel DamIP method. Taken together, these studies aim to investigate the molecular mechanisms of PC and LRH-1 agonists, which would not only be important for understanding and treating fatty liver disease, but would greatly impact on the full spectrum of disorders associated with the metabolic syndrome, e.g. diabetes mellitus and atherosclerosis.