Cudratricusxanthone A Inhibits Lipid Accumulation and Expression of Inducible Nitric Oxide Synthase in 3T3-L1 Preadipocytes

Cudratricusxanthone A (CTXA) is a natural bioactive compound extracted from the roots of Cudrania tricuspidata Bureau and has been shown to possess anti-inflammatory, anti-proliferative, and hepatoprotective activities. However, at present, anti-adipogenic and anti-inflammatory effects of CTXA on adipocytes remain unclear. In this study, we investigated the effects of CTXA on lipid accumulation and expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, two known inflammatory enzymes, in 3T3-L1 preadipocytes. Strikingly, CTXA at 10 µM markedly inhibited lipid accumulation and reduced triglyceride (TG) content during 3T3-L1 preadipocyte differentiation with no cytotoxicity. On mechanistic levels, CTXA at 10 µM suppressed not only expression levels of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), and perilipin A, but also phosphorylation levels of signal transducer and activator of transcription-3 (STAT-3) and STAT-5 during 3T3-L1 preadipocyte differentiation. In addition, CTXA at 10 µM up-regulated phosphorylation levels of cAMP-activated protein kinase (AMPK) while down-regulating expression and phosphorylation levels of acetyl-CoA carboxylase (ACC) during 3T3-L1 preadipocyte differentiation. Moreover, CTXA at 10 µM greatly attenuated tumor necrosis factor (TNF)-α-induced expression of iNOS, but not COX-2, in 3T3-L1 preadipocytes. These results collectively demonstrate that CTXA has strong anti-adipogenic and anti-inflammatory effects on 3T3-L1 cells through control of the expression and phosphorylation levels of C/EBP-α, PPAR-γ, FAS, ACC, perilipin A, STAT-3/5, AMPK, and iNOS.