Aqueous extracts of purple sweet potato attenuate weight gain in high fat-fed mice

Purple sweet potato is a widely consumed food around the world has been reported to possess antioxidant, antimutagenic and memory-enhancing effects. However, antiobesity effect of PSP is not clear. The objective of this study was to determine the effects of Purple Sweet Potato Extracts (PSPE) on serum and fecal lipid profiles, body weight gain, body fat percentage and hepatic lipogenesis. Mice were administered a standard chow diet, a 45% high-fat diet, or a high-fat diet with various doses of PSPE. Mice that were fed a high-fat diet containing PSPE were found to have lower increases in body and adipose tissue weights and lessened occurrences of hepatic steatosis than mice that were fed a high-fat diet without PSPE. The decreased adiposity induced by PSPE accounted for lower serum levels of leptin and a higher adiponectin/leptin ratio. PSPE administration also resulted in a significant decrease in serum and hepatic triglyceride and cholesterol levels and a significant increase in fecal triglyceride and cholesterol levels when compared to the high-fat group. To identify the mechanism by which PSPE induced its antiobesity effect, the expression of lipogenesis-related genes that were induced in high fat-fed mice was investigated. PSPE suppressed the expression of Sterol Regulatory Element-Binding Protein (SREBP)-l, Acyl-CoA Synthase (ACS), Glycerol-3-Phosphate Acyltransferase (GPAT), HMG-CoA Reductase (HMGR) and Fatty Acid Synthase (FAS) in liver tissue in mice provided the high-fat diet. These findings suggest that the antiobesity effect of PSPE in high fat-fed mice occurs through its modulation of lipogenesis in the liver and inhibition of dietary lipid absorption.