High-Intensity Interval Training Attenuates Hepatic Fibrosis by Remodeling Lactate Metabolism in MASLD.

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) has emerged as a global metabolic disorder. As a non-pharmacological intervention, the effects of high-intensity interval training (HIIT) on MASLD and its molecular mechanisms remain poorly understood. This study aimed to investigate whether HIIT could ameliorate high-fat diet (HFD)-induced liver fibrosis by recalibrating the intrahepatic lactate metabolic axis. Methods: An HFD-induced murine MASLD model combined with HIIT intervention was utilized to evaluate the therapeutic efficacy and underlying mechanisms. Hepatosomatic indices, histological architecture and fibrosis severity were examined. Lactate concentrations within the systemic circulation and hepatic parenchyma, alongside comprehensive lipid profiles, were measured. The expressions of genes and proteins involved in hepatic lactate metabolism were delineated via qPCR and Western blotting. Results: The 8-week HIIT intervention effectively improved liver lipid accumulation, hepatocellular injury, and oxidative stress caused by a high-fat diet. Fibrotic expansion and suppressed hepatic stellate cell activation were restricted markedly, as evidenced by the downregulation of collagen type I alpha 1 chain and alpha-smooth muscle actin(α-SMA). HIIT reversed the HFD-induced accumulation of lactate in both systemic circulation and liver tissues, which was found to positively correlate with hepatic α-SMA. Mechanistically, HIIT regulated the expression of the lactate metabolism-related proteins lactate dehydrogenase A and monocarboxylate transporter 1, while selectively enhancing the expression of the gluconeogenic enzymes. Conclusions: Our findings indicate that HIIT effectively ameliorated MASLD and associated hepatic fibrosis by remodeling the hepatic lactate metabolic axis, specifically through the suppression of lactate production and the enhancement of its clearance. These results indicate that targeting lactate homeostasis might be a promising therapeutic strategy for MASLD.