Potential antiobesity and antihepatic steatosis effects of a Capsosiphon fulvescens (maesaengi) ethanol extract: in vitro and in vivo studies

Obesity and non-alcoholic fatty liver disease (MASLD) are closely linked metabolic disorders, yet safe and multi-targeted interventions remain limited. Capsosiphon fulvescens (CF), an edible green alga rich in bioactive constituents, has been suggested to possess metabolic regulatory properties; however, its anti-obesity and anti-steatotic activities remain insufficiently defined. This study investigated the anti-obesity and anti-steatotic activities of Capsosiphon fulvescens ethanol extract (CFE) and its effects on lipid metabolism using both in vitro and diet-induced obesity models. Lipid accumulation and intracellular triglyceride levels were assessed in 3T3-L1 adipocytes and HepG2 hepatocytes by Oil Red O staining and enzymatic assays, along with the evaluation of lipid-metabolism-related gene expression. Male C57BL/6J mice were fed a normal diet, high-fat diet (HFD), or HFD supplemented with CFE (150 or 300 mg kg-1 day-1, orally) for 12 weeks. CFE markedly reduced lipid droplet formation and triglyceride content in both cell models relative to MDI- or oleic acid-treated controls. In addition, CFE modulated the expression of genes involved in adipogenesis, lipogenesis, lipolysis, and fatty acid oxidation. In HFD-fed mice, chronic CFE administration attenuated body weight gain, reduced hepatic and visceral fat accumulation, and improved hepatic steatosis. Collectively, these findings suggest that CFE attenuates lipid accumulation and is associated with transcriptional modulation of lipid metabolism-related genes.