Exercise training ameliorates carbon tetrachloride-induced liver fibrosis and anxiety-like behaviors.

Chronic liver diseases and cirrhosis are associated with mood disorders. Regular exercise has various beneficial effects on multiple organs, including the liver and brain. However, the therapeutic effect of exercise on liver fibrosis concomitant with mood disorders, such as anxiety, has not been evaluated. In this study, the effects of exercise training on liver fibrosis-related anxiety-like behaviors were evaluated. Male C57/BL6 mice were divided into four groups: vehicle-sedentary, vehicle-exercise, carbon tetrachloride (CCl4)-sedentary, and CCl4-exercise. Liver fibrosis was induced by CCl4 administration for 8 weeks, exercise was applied in the form of voluntary wheel running. After intervention, anxiety-like behavior was assessed using the elevated plus maze. CCl4 increased liver and serum fibrotic markers, as measured by blood analysis, histochemistry, and qRT-PCR, and these changes were attenuated by exercise training. CCl4 induced anxiety-like behavior, which was ameliorated by exercise training. In the hippocampus, CCl4-induced changes in mRNA and protein levels of factors related to anxiety, including BDNF and nNOS, were reversed by exercise. These results suggested that hepatic fibrosis-related anxiety-like behaviors are induced by excess hippocampal nNOS, and the beneficial effects of exercise were mediated by increases in BDNF and reductions in nNOS. The percentage of fibrotic area was negatively correlated with anti-anxiety behavior and positively associated with hippocampal nNOS protein levels. Liver fibrosis-related anxiety-like behaviors could be alleviated through the regulation of hippocampal BDNF and nNOS via exercise training. These results support the therapeutic value of exercise by targeting the mechanisms underlying liver fibrosis and associated anxiety.