Background and aims

Exercise remains a key component of nonalcoholic fatty liver disease (NAFLD) treatment. However, mechanisms underpinning the improvements in NAFLD seen with exercise are unclear. Exercise improved liver fat and serum biomarkers of liver fibrosis in the NASHFit trial. We investigated exercise's mechanism of benefit by conducting a post hoc analysis of these data to determine the relationship between serum fibroblast growth factor (FGF) 21, which is implicated in NAFLD development, and exercise.

Methods

In the 20 wk NASHFit trial, patients with nonalcoholic steatohepatitis (NASH) were randomized to receive moderate-intensity aerobic exercise training or standard clinical care. Mediterranean-informed dietary counseling was provided to each group. Change in serum FGF21 was measured after an overnight fast.

Results

There was a significant improvement in serum FGF21 with exercise training compared to standard clinical care (p = 0.037) with serum FGF21 reducing by 22% (-243.4 +/-349 ng/mL) with exercise vs. a 34% increase (+88.4 ng/mL +/-350.3 ng/mL) with standard clinical care. There was a large inverse association between change in serum FGF21 and change in cardiorespiratory fitness (VO₂peak) (r = -0.62, 95% CI -0.88 to -0.05, p = 0.031), and on multivariable analysis, change in VO₂peak remained independently associated with change in FGF21 (β = -44.5, 95% CI -83.8 to -5.11, p = 0.031).

Conclusions

Serum FGF21 is markedly decreased in response to aerobic exercise training, offering a novel mechanism to explain the observed reduction in liver fat and improvement in serum biomarkers of liver fibrosis in patients with NASH who do exercise.