Hepatoprotective mechanism of freshwater clam extract alleviates non-alcoholic fatty liver disease: elucidated in vitro and in vivo models

Freshwater clams (Corbicula fluminea) have long been used as a folk remedy in Chinese tradition. Their hot-water extract has been commercialized as a functional drink for liver protection. The objective of this study was to develop a product of the residual clam meat (FCR) and assess its functional compounds. The ethanol extract of FCR, designated FCRE, was identified to comprise phytosterols, polyunsaturated fatty acids (PUFAs) and carotenoids. FCRE significantly reduced lipid accumulation and cell death in HepG2 cells via decreased fatty acid synthase (FAS) activity and increased activities of carnitine palmitoyltransferase (CPT) and acyl-CoA oxidase (ACO), indicative of suppressed lipogenesis and increased β-oxidation of fatty acids. In tilapia fed with high-fat diet (HFD), FCRE mitigated nonalcoholic steatohepatitis (NASH), which was evidenced by decreased levels of plasma aspartate transaminase (AST) and alanine transaminase (ALT), in addition to reduced total cholesterol and accumulation of triacylglycerols, particularly those of saturated and monounsaturated fatty acids. FCRE also suppressed stearoyl-CoA desaturase-1 (SCD-1) index, increased the PUFAs’ n3/n6 ratio, and reduced prostaglandin E2 (PGE2) and inflammatory infiltrates in tilapia liver. Tilapia fed with HFD for 2 weeks displayed NASH symptoms, while mice took 10 weeks to display NASH symptoms. No previous study has been reported on the potential use of tilapia as an NASH model for pre-screening hepatoprotective-functional foods.