Ethanolic extract of Sargassum serratifolium inhibits adipogenesis in 3T3-L1 preadipocytes by cell cycle arrest

The brown alga, Sargassum serratifolium C. Agardh, has been reported to have high levels of meroterpenoids having anti-inflammatory, antioxidant, and anti-diabetic activities. This study investigated the effect of ethanolic extract of S. serratifolium (ESS) on the inhibition of adipogenesis and lipid accumulation in 3T3-L1 preadipocytes. ESS suppressed the accumulation of lipid droplets and triglycerides (TG), while enhancing the lipolysis of intracellular TG. We found that ESS induced cell cycle arrest at the G1/S phase via suppressing protein expression of cyclin-dependent kinases (CDK) 2, CDK4, CDK6, and cyclin E. Moreover, ESS reduced the expression of CCAAT/enhancer-binding protein (C/EBP) beta during the early stage of adipogenesis, leading to suppressed expression of both messenger RNA (mRNA) and protein of C/EBP alpha and peroxisome proliferator-activated receptor gamma. As a result, ESS reduced mRNA and protein levels of lipogenic transcription factors such as retinoid X receptor, and sterol regulatory element-binding protein 1c and their target genes, such as fatty acid synthase and stearoyl-CoA desaturase (SCD) 1. Overall, ESS inhibited adipocyte differentiation in early stage and lipid accumulation during adipogenesis through downregulation of adipogenic and lipogenic transcription factors, providing the anti-obesity mechanism of ESS.