PI3K/Akt pathway activation was involved in acute ethanol-induced fatty liver in mice

Abstract

Accumulating evidences support the important roles of sterol regulatory element-binding protein-1 (SREBP-1) activation in ethanol-induced fatty liver, but the underlying mechanisms for its activation are not fully understood. Recent studies have demonstrated that phosphatidylinositol 3 kinase (PI3K)/Akt pathway activation could enhance SREBP-1 activity. The current study was designed to investigate the potential roles of PI3K/Akt pathway in acute ethanol-induced fatty liver in mice. In the first experiment, mice were treated with ethanol (2.5 or 5g/kg bw) or isocaloric/isovolumetric maltose–dextrin solution, and sacrificed at several time points after ethanol exposure. As expected, ethanol dose-dependently increased the hepatic triglyceride (TG) levels and the protein levels of the mature form of SREBP-1 (n-SREBP-1). The phosphorylation of Akt and glycogen synthase kinase-3β (GSK-3β) was significantly increased in mice treated with ethanol (5g/kg bw), while the protein levels of PI3K-p85 were significantly reduced. To confirm the roles of PI3K/Akt pathway, mice were then pretreated with wortmannin (0.7 or 1.4mg/kg bw), a specific PI3K/Akt pathway inhibitor, before exposure to ethanol. Interestingly, a dual effect of wortmannin was observed. Low dose of wortmannin significantly reduced the hepatic TG levels, while high dose of wortmannin aggravated ethanol-induced fatty liver. The ratio of LC3II/LC3I of wortmannin (1.4mg/kg bw) group mice was significantly increased, while the p62 protein level was significantly decreased compared to those of ethanol group, which indicated that wortmannin (1.4mg/kg bw) might suppress the lipid degradation by autophagy. These results supported the hypothesis that PI3K/Akt activation might be involved in acute ethanol-induced fatty liver, and PI3K/Akt inhibitors might have therapeutic potential for the treatment of ethanol-induced fatty liver.