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Fatty Liver Disease and Multi-System Complications | EK28


Bioactive lipid metabolism in Human NAFLD progression: role of fatty acid omega hydroxylase genes (CYP4) in inflammation and hepatic encephalopathy.


Mar 22, 2021 12:00am ‐ Mar 22, 2021 12:00am

Description

Bioactive lipid metabolism in Human NAFLD progression: role of fatty acid omega hydroxylase genes (CYP4) in inflammation and hepatic encephalopathy. Bioactive lipid metabolism in Human NAFLD progression: role of fatty acid omega hydroxylase genes (CYP4) in inflammation and hepatic encephalopathy. Charles Leahy1, Paula Rote2, Elizabeth Olah1, Nicholas Osborne1, Byoung J. Song3, Yanqiao Zhang 1, and James. P. Hardwick1 1. Northeast Ohio Medical University, Department of Integrative Medical Sciences, Liver Focus group, 4209 State Route 44, Rootstown, Ohio 44272, 2. Internal Medicine University of Minnesota Health care system, Minneapolis, MN 55455, 3. Laboratory of Membrane Biochemistry and Biophysics; Section of Molecular Pharmacology and Toxicology, NIAAA, 5625 Fishers Lane, Room 3N-01, MSC 9410, Bethesda, MD 20892 The Human fatty acid Omega hydroxylase gene family (CYP4) members function in the metabolism of saturated and unsaturated fatty acids as well as bioactive eicosanoids. Different subfamily members metabolize short-chain (CYP4B1), medium-chain (CYP4A), long-chain (CYP4F), and very-long-chain fatty acids (CYP4F). Members of the CYP4A and CYP4F subfamily also metabolize the bioactive eicosanoid lipids, arachidonic acid, prostaglandins, and leukotrienes. We hypothesize that the differential regulation of CYP4 members participates in the initiation and progression of nonalcoholic fatty liver disease (NAFLD). In this study, we analyzed the regulation, expression, and activity of CYP4s that participate in the metabolism of bioactive eicosanoids in the fourteen human livers from patients with steatosis (NAFLD), non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma (HCC). We show that arachidonic metabolism by CYP4A11 and CYP4A22 produces 20-HETE, which promotes progression from steatosis to HCC. This arachidonic metabolite likely causes vasoconstriction of hepatic sinusoid and dysfunction of the sinusoid's endothelial cells, leading to hepatic hypertension and sinusoid fluid leakage. We also measured the pro-inflammatory eicosanoid Leukotriene B4 (LTB4) levels, which decreased with the progression of NAFLD to HCC. The reduction in LTB4 levels was due to metabolism by CYP4F3a and newly identified CYP4F2b that are over-expressed in cirrhosis and hepatocellular carcinoma. We also analyzed the prostaglandin (PG) omega hydroxylase expression, CYP4F8, and show that its regulation and expression decrease from NASH to HCC. These results suggest that PGE2 increases from NASH to HCC, thus promoting cell proliferation, angiogenesis, metastasis, and immune evasion. Our results also indicate that over-expression of CYP4A11 and increased levels of 20-HETE in cirrhosis and HCC can be pivotal in the initiation of hepatic encephalopathy and ascites. Furthermore, the reduced pro-inflammatory LTB4 and possible elevated PGE2 in cirrhosis and HCC may be instrumental in tumor immune evasion.

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