Abstract
Large amounts of procyanidins, made up of catechin oligomers, are consumed on a daily basis via various plant-based diets. Recent studies show that tea polyphenol (TP) exerts anti-obesity effect; however, the biological functions of procyanidins have not yet been established. In this study, we examined the high dose effects of procyanidins from apple polyphenol (AP), hop polyphenol (HP), and tea polyphenol (TP) on obesity using normal Sprague-Dawley rats on a high fat (HF) diet. We measured adipose tissue mass and tissue lipid parameters in rats on polyphenol-free low fat (LF) (7%) or HF (27.8%) diets with or without 1% of each polyphenol for 9 weeks. Dietary AP, HP, and TP suppressed the increase in white adipose tissue. Dietary TP increased the level of fatty acids excreted into feces; however, this was not observed in the AP- or HP-fed group. Each dietary polyphenol tended to reduce fatty acid synthesis and promote fatty acid β-oxidation as compared with a HF diet alone. Moreover, each dietary polyphenol tended to increase the level of peroxisome proliferator-activated receptor alpha (PPARα) in the liver and decreased the levels of PPARγ in brown and white adipose tissues. Therefore, we speculate that procyanidins from AP or HP may reduce the increase in white adipose tissue induced by an HF diet through a combination of the agonist-like action of PPARα and antagonist-like action of PPARγ. On the other hand, TP may exert an anti-obesity effect via the combined effect of PPARα and PPARγ described above as well as the promotion of fatty acid excretion into feces.
