Magnesium isoglycyrrhizinate attenuates acute alcohol-induced hepatic steatosis in a zebrafish model by regulating lipid metabolism and ER stress.

BACKGROUND

Alcoholism is a well-known risk factor for liver injury and is one of the major causes of hepatic steatosis worldwide. Although many drugs have been reported to have protective effects against acute alcohol-induced hepatotoxicity, there is limited available treatment for alcoholic liver disease (ALD), indicating an urgent need for effective therapeutic options. Herein, we first reported the protective effects of magnesium isoglycyrrhizinate (MgIG) on acute alcohol-induced hepatic steatosis and its related mechanisms in a zebrafish model.

METHODS

Alcohol was administered directly to embryo medium at 5 days post-fertilization (dpf) for up to 32 h. MgIG was given to the larvae 2 h before the administration of alcohol and then cotreated with alcohol starting at 5 dpf. Oil red O staining was used to determine the incidence of steatosis, and pathological features of the liver were assessed by hematoxylin-eosin staining. Biological indexes, total cholesterol (TC) and triacylglycerol (TG) were detected in the livers of zebrafish larvae. Morphological changes in the livers of zebrafish larvae were observed using liver-specific EGFP transgenic zebrafish (Tg(lfabp10a:eGFP)). The expression levels of critical molecules related to endoplasmic reticulum (ER) stress and lipid metabolism were detected by qRT-PCR, whole-mount in situ hybridization and western blotting.

RESULTS

Alcohol-treated larvae developed hepatomegaly and steatosis after 32 h of exposure. We found that MgIG improved hepatomegaly and reduced the incidence of steatosis in a dose-dependent manner by oil red O staining and diminished deposits of alcohol-induced fat droplets by histologic analysis. Moreover, MgIG significantly decreased the levels of TC and TG in the livers of zebrafish larvae. Furthermore, the expression levels of critical genes involved in ER stress (atf6, irela, bip, chop) and the key enzymes regulating lipid metabolism (acc1, fasn, hmgcs1 and hmgcra) were significantly higher in the alcohol-treated group than in the control group. However, in the MgIG plus alcohol-treated group, the expression of these genes was markedly decreased compared with that in the alcohol-treated group. Whole-mount in situ hybridization and western blotting also showed that MgIG had an effect on the expression levels of critical genes and proteins involved in lipid metabolism and ER stress. Our results revealed that MgIG could markedly regulate these genes and protect the liver from ER stress and lipid metabolism disorders.

CONCLUSIONS

Our study is the first to demonstrate that MgIG could protect the liver from acute alcohol stimulation by ameliorating the disorder of lipid metabolism and regulating ER stress in zebrafish larvae.