Duration-Dependent Aerobic Exercise Attenuates HFD-Induced MASLD in Association with Improved Hepatic Iron Homeostasis and Reduced Ferroptosis-Related Alterations.

Background/Objectives: Aerobic exercise is widely recognized as an effective non-pharmacological strategy for metabolic dysfunction-associated steatotic liver disease (MASLD). However, the effects of different aerobic exercise loads on MASLD-associated hepatic iron dyshomeostasis and ferroptosis, as well as the underlying mechanisms, remain unclear. This study aimed to compare the effects of different aerobic exercise loads on HFD-induced MASLD and to explore whether exercise-induced improvements in hepatic lipid accumulation are associated with changes in iron homeostasis and ferroptosis-related markers. Methods: Forty male Sprague-Dawley rats were randomly assigned to a normal-fat diet group (NFD, n = 8) or a high-fat diet group (HFD, n = 32). After 8 weeks of HFD feeding, HFD-fed rats were further allocated to four groups: HFD control, low-load aerobic exercise (LEH), moderate-load aerobic exercise (MEH), and high-load aerobic exercise (HEH) (n = 8 per group). The exercise intervention lasted for 8 weeks. At the end of the intervention, blood and liver samples were collected to assess metabolic parameters, hepatic steatosis, iron homeostasis, oxidative stress, ferroptosis-related markers, and the IL-6/JAK2/STAT3-hepcidin pathway. Results: All three exercise regimens partially improved hepatic lipid metabolic abnormalities, iron accumulation, and oxidative stress-related liver injury in MASLD rats. These effects were accompanied by suppression of the IL-6/JAK2/STAT3-hepcidin pathway, increased hepatic FPN1 mRNA expression and decreased DMT1 mRNA expression, increased GPX4 expression, reduced PTGS2 expression, and improved antioxidant capacity. MEH and HEH generally produced larger changes than LEH, with HEH showing the most consistent overall response across the measured outcomes. Conclusions: Aerobic exercise attenuated HFD-induced MASLD in association with improved hepatic iron handling and a lower burden of ferroptosis-related molecular alterations. Because ferroptosis-specific rescue experiments and pathway inhibitors were not used, these findings are associative. Within the tested conditions, the 90-min protocol produced the most consistent response, but further dose-response studies are required before translation to humans.