Inhibition of Adipogenesis by Oligonol through Akt-mTOR Inhibition in 3T3-L1 Adipocytes

Polyphenols have recently become an important focus of study in obesity research. Oligonol is an oligomerized polyphenol, typically comprised of catechin-type polyphenols from a variety of fruits, which has been found to exhibit better bioavailability and bioreactivity than natural polyphenol compounds. Here, we demonstrated that Oligonol inhibits 3T3-L1 adipocyte differentiation by reducing adipogenic gene expression. During adipogenesis, Oligonol downregulated the mRNA levels of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding proteins α (C/EBPα), and δ (C/EBPδ) in a dose-dependent manner and the expression of genes involved in lipid biosynthesis. The antiadipogenic effect of Oligonol appears to originate from its ability to inhibit the Akt and mammalian target of rapamycin (mTOR) signaling pathway by diminishing the phosphorylation of ribosomal protein S6 kinase (p70S6K), a downstream target of mTOR and forkhead box protein O1 (Foxo1). These results suggest that Oligonol may be a potent regulator of obesity by repressing major adipogenic genes through inhibition of the Akt signaling pathway, which induces the inhibition of lipid accumulation, ultimately inhibiting adipogenesis.