Siphonaxanthin, a Carotenoid From Green Algae, Inhibits Lipogenesis in Hepatocytes via the Suppression of Liver X Receptor Activity

Nonalcoholic fatty liver disease (NAFLD) has shown an increasing morbidity in recent years. Here, we demonstrated that siphonaxanthin (SPX), a rare marine carotenoid, exhibits a strong inhibitory effect on aggravated hepatic lipogenesis in vitro and would be a promising candidate in the prevention and alleviation of NAFLD in the future. In this study, we conducted a preliminary assessment of the effect of SPX on hepatic lipogenesis by using the HepG2 cell line, derived from human liver cancer, as a model of the liver. SPX significantly suppressed the excess accumulation of triacylglycerol induced by liver X receptor (LXR) agonist by downregulating a nuclear transcription factor named sterol regulatory element-binding protein-1c and a set of related genes. Moreover, fatty acid translocase (CD36) and fatty acid-binding protein-1, which regulates fatty acid uptake, also exhibited significant decrease in transcriptional levels. Furthermore, we found that SPX blocked LXR activation and would be a promising candidate for antagonist of LXR.