OBJECTIVE  To explore the therapeutic effects of exercise combined with orlistat on high-fat diet-induced non-alcoholic steatohepatitis(NASH) in mice.

METHODS  Forty male C57BL/6J mice were randomly divided into five groups(n=8 per group) based on body weight: the normal group, the model group, the exercise group, the drug-administered group, and the combination therapy group. The body weight of each mouse was measured and recorded three times a week. After the final administration, the mice were fasted for 12 hours. Subsequently, fasting blood glucose levels were measured, following which all mice were euthanized. The body length, liver weight, and epididymal fat mass of the mice in each group were measured. Serum insulin levels, serum liver function indicators including aspartate aminotransferase(AST), alanine aminotransferase(ALT), total cholesterol(TC), triglycerides(TG), high-density lipoprotein(HDL), and low-density lipoprotein(LDL), as well as the expression levels of serum inflammatory factors such as tumor necrosis factor-α(TNF-α), interleukin-6(IL-6), and interleukin-1β(IL-1β) were assessed. Additionally, Lee's index and the insulin resistance index were calculated. Hepatic histopathology was evaluated through HE and Oil Red O staining to assess lipid accumulation and inflammation infiltration. Western blotting and Immunofluorescence were used to detect the expression of proteins involved in liver lipid metabolism, including FASN, ACC, CPT1α, and PPARα.

RESULTS  Compared to the model group, the body weight, liver weight, obesity index, epididymal fat weight, liver function indices(AST, ALT, TC, TG, LDL, HDL) , levels of the inflammatory cytokines(TNF-α, IL-6, IL-1β), fasting blood glucose, insulin levels, and the insulin resistance index were significantly increased in the the exercise group, the drug-administered group, and the combination therapy group. The degree of hepatic steatosis, inflammation, NAS score, and lipid droplet deposition were also significantly increased. The levels of lipid synthesis proteins FASN and ACC were significantly increased, and the levels of lipid oxidizing proteins PPARα and CPT1α were significantly decreased. Compared to the model group, the weight, liver weight, obesity index, epididymal fat weight, liver function indexes(AST, ALT, TC, TG, LDL, HDL), levels of inflammatory cytokines(TNF-α, IL-6, IL-1β), fasting blood glucose, insulin levels and the insulin resistance index decreased significantly in the exercise group, administration group and combination treatment group. The degree of hepatic steatosis, inflammation, NAS score, and lipid droplet deposition was significantly improved. The levels of lipid synthesis proteins FASN and ACC were significantly decreased, while the levels of lipid oxidation proteins PPARα and CPT1α were significantly increased. The combination therapy group demonstrated the best outcomes across all indicators.

CONCLUSION  The combination of exercise and orlistat exhibits a favorable therapeutic effect on NASH mice, significantly improving liver function and insulin resistance, inhibiting hepatic lipid deposition and inflammation. This effect is associated with the activation of the AMPK-related pathway, leading to a reduction in the levels of lipogenic proteins such as FASN and ACC, as well as an increase in the content of lipid-oxidizing proteins like PPARα and CPT1α.