Anti-obesity effect of dietary polyphenols from unripe apple in rats

Abstract

Generally, apple thinning is employed to enable the growth of larger fruit. The thinned out unripe apples contain high amounts of polyphenols. Anti-obesity effect of dietary polyphenols from unripe apple (UP) was examined in rats in this study as a potential utilization of unripe apples. UP (0.17 %) was given to Sprague-Dawley (SD) rats under a pair-feeding condition for 62 days. Dietary UP suppressed the increase in white adipose tissue mass, and plasma and liver triglyceride (TG) levels. Increases of plasma insulin and their levels were also significantly inhibited by dietary UP. Gene expression of hepatic fatty acid β-oxidation enzymes increased in rats fed UP. Moreover, dietary UP increased the gene expression of hepatic peroxisome proliferator-activated receptor α. In addition to these actions, UP inhibited digestive enzyme activities of carbohydrate and fat, and micellar solubility of TG, cholesterol and bile acid in vitro. The inhibition of absorption of glucose and hydrolyzed fat by UP was observed using the everted sac method. Thus, UP may exert an anti-obesity effect through modulation of fatty acid metabolism in liver and inhibition of absorption of carbohydrate and fat. Therefore, unripe apple containing high levels of polyphenols may be useful as a prophylactic for obesity.