Wilson Disease: Regulation of Steatosis by Methionine Metabolism

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DESCRIPTION (provided by applicant): This proposal describes a 5 year training program for the development of an academic career in Hepatology, oriented to basic science research. The principal investigator has scientific background on Wilson Disease and now will expand upon her scientific skills through a unique integration of resources. This program will promote the understanding of the molecular mechanisms relating copper overload to steatosis in Wilson Disease, with the ultimate objective to explore new therapies for this rare disease based on the modification of these aberrant underlying processes. Dr. CH Halsted and Dr. JC Rutledge will mentor the principal investigator's scientific and career development. They are recognized leaders in the fields of methionine and lipid metabolism and they have trained numerous postdoctoral fellows and graduate students. The research will focus on the inhibitory effect exerted by copper accumulation on the enzyme S-adenosylhomocysteine (SAH) hydrolase. Preliminary data demonstrate that SAH hydrolase inhibition is followed by significant reduction of the hepatic S-adenosylmethionine (SAM):SAH ratio, a marker of methylation status, and later time-dependent homocysteine increase. The proposed experiments will entail the use of a copper chelator to reduce hepatic copper concentration and improve SAH hydrolase activity, thereby demonstrating the direct effect of copper on this enzyme, and further inhibition of SAH hydrolase both in vivo (with DZA) and in vitro (with shRNA carried by lentivirus) and provision of methyl groups as supplemental betaine, a compound known to correct aberrant methionine metabolism. An assortment of biochemical, molecular, and cellular techniques, including epigenetic methods will be used to study methionine and lipid metabolism. The specific aims include: 1) Establishing relationships among copper accumulation, hepatic steatosis, and aberrant methionine metabolism, 2) Determining if the methyl donor betaine can improve lipid metabolism in tx-j mice and in primary hepatocytes from the same animal model, and 3) Determining if steatosis in Wilson disease is mediated by epigenetic regulation of expressions of genes relevant to lipid synthesis. This will be the first detailed analysis of the mechanisms of hepatic steatosis based on the metabolism of methionine in this rare disease. The University of California Davis provides an ideal setting for training physician- scientists by incorporating expertise from diverse resources into customized programs. Such an environment maximizes the potential for the principal investigator to establish a scientific niche from which an academic career can be constructed. The successful outcome of the proposed experiments will promote an understanding of the metabolic processes underlying the pathogenesis of steatosis in Wilson disease, an orphan disease (included in the NIDDK action plan for Liver Disease Research) whose genetic background is well-established but whose metabolic etiopathogenesis is unclear. The study will also provide insights into the role of copper and methionine metabolism in more common diseases, such as non-alcoholic fatty liver disease.