Walnut Polyphenols Inhibit Pancreatic Lipase Activity in Vitro and Have Hypolipidemic Effect on High-Fat Diet- Induced Obese Mice

This study was aimed at the chemical composition and inhibitory effects of walnut polyphenols (WP) in vitro lipase activity and on obesity in obese mice models. More than 20 individual phenolics such as gallotannins, ellagitannins, flavonoids and phenolic acids were identified in WP. Studying the interactions between porcine pancreatic lipase (PL) and WP were based on fluorescence quenching and an enzymatic assay. The addition of WP to lipase caused a reduction of protein fluorescence intensity at 310 K. In addtion, we found that the effect of WP on PL was dependent on reaction medium and substrate used and the half maximal inhibitory concentration of WP was determined to be 163 μg/mL. At the beginning of the experiment, mice were divided into 3 groups, one of them served as normal control group (NCG), the second as hyperlipidemia control group (HCG), the last as walnut polyphenol-treated group (WTG). After 8 weeks of treatment, we investigated the effects of WP on weight gain, food intake and biochemical indexes in obese mice. The results showed that WP could significantly decrease body weight in obese mice (-13.52%, P < 0.05). However, there was no remarkable difference in food intake among three groups (1760.2–1823.3 g). In addition, WP could significantly decrease the TG, TC and LDL-cholesterol (LDL-C) concentrations and increase the HDL-cholesterol (HDL-C) concentration when compared to the HCG (-36.12%, 31.27%, -73.3%, and +59.72%, respectively, P < 0.01). The levels of hepatic TG and TC were significantly decrease in WTG when compared to the HCG (-27.72% and -48.43%, respectively, P < 0.01). In conclusion, these results suggest that WP could be a potentially therapeutic alternative in the treatment of obesity caused by a high-fat diet.