Effect of Polyphenol-αich Extract from Walnut on Diet-Induced Hypertriglyceridemia in Mice via Enhancement of Fatty Acid Oxidation in the Liver

The kernel pellicles of walnut are rich in ellagitannins with antioxidative activity. A polyphenol-rich extract from walnuts (WP, 45% polyphenol) was prepared and evaluated for its hypolipidemic effect in high fat diet fed mice. Oral administration of WP (100 and 200 mg/kg) significantly reduced liver weight and liver and serum triglycerides (TG). Hepatic β-oxidation in cytosol, including peroxisome, was enhanced by WP (50-200 mg/kg). mαNA expressions of hepatic peroxisome proliferatoractivated receptor (PPAα) α and acyl coenzyme A oxidase (ACOX) 1 were enhanced by WP (50-200 mg/kg). With respect to the hypotriglyceridemic mechanism of WP, it suppressed neither olive oil induced serum TG elevation in mice nor oleic acid induced TG accumulation in HepG2 cells. On the other hand, mαNA expressions of PPAαα, ACOX1, and carnitine palmitoyltransferase (CPT) 1A in HepG2 cells were significantly enhanced by addition of WP (100 μg/mL). Moreover, tellimagrandin I, a polyphenolic constituent in WP, enhanced ACOX1 expression at 1-100 μg/mL. In conclusion, WP was found to possess hypotriglyceridemic activity via enhancement of peroxisomal fatty acid β-oxidation in the liver. These results suggest that tellimagrandin I is involved in the hypotriglyceridemic mechanism of WP.