Serine prevented high-fat diet-induced oxidative stress by activating AMPK and epigenetically modulating the expression of glutathione synthesis-related genes

Abstract

Serine deficiency has been observed in patients with nonalcoholic fatty liver disease (NAFLD). Whether serine supplementation has any beneficial effects on the prevention of NAFLD remains unknown. The present study was conducted to investigate the effects of serine supplementation on hepatic oxidative stress and steatosis and its related mechanisms. Forty male C57BL/6J mice (9week-old) were randomly assigned into four groups (n=10) and fed: i) a low-fat diet; ii) a low-fat diet supplemented with 1% (wt:vol) serine; iii) a high-fat (HF) diet; and iv) a HF diet supplemented with 1% serine, respectively. Palmitic acid (PA)-treated primary hepatocytes separated from adult mice were also used to study the effects of serine on oxidative stress. The results showed that serine supplementation increased glucose tolerance and insulin sensitivity, and protected mice from hepatic lipid accumulation, but did not significantly decreased HF diet-induced weight gain. In addition, serine supplementation protected glutathione (GSH) antioxidant system and prevented hypermethylation in the promoters of glutathione synthesis-related genes, while decreasing reactive oxygen species (ROS) in mice fed a HF diet. Moreover, we found that serine supplementation increased phosphorylation and S-glutathionylation of AMP-activated protein kinase α subunit (AMPKα), and decreased ROS, malondialdehyde and triglyceride contents in PA-treated primary hepatocytes. However, while AMPK activity or GSH synthesis was inhibited, the abovementioned effects of serine on PA-treated primary hepatocytes were not observed. Our results suggest that serine supplementation could prevent HF diet-induced oxidative stress and steatosis by epigenetically modulating the expression of glutathione synthesis-related genes and through AMPK activation.