Hepatic lipid peroxidation, protein carbonylation, and membrane fluidity across an acute maximal treadmill-running test and three treadmill-training periods

Aerobic exercise induces systemic physiological responses that extend beyond contractile tissues, yet hepatic oxidative and membrane-related profiles after acute and repeated running exercise remain incompletely characterized. This study examined hepatic lipid peroxidation, protein carbonyl content, and plasma and mitochondrial membrane fluidity after acute maximal exercise and after different durations of treadmill-running exposure. Fifty male Sprague-Dawley rats were included in 5 prespecified experimental groups: a baseline non-exercised control group (CON), an acute maximal exercise group (AME), and treadmill-running groups trained for 1 week (1WT), 4 weeks (4WT), or 12 weeks (12WT). Hepatic malondialdehyde and 4-hydroxyalkenals (MDA + 4-HDA) concentration, protein carbonyl content, and plasma and mitochondrial membrane fluidity were assessed, and group differences were analyzed using one-way ANOVA complemented by effect size estimates. MDA + 4-HDA concentration differed significantly among experimental conditions ( p < 0.0001; η² = 0.543), with higher values in the longer training groups, increasing from 0.197 ± 0.026 nmol/mg protein in CON to 0.305 ± 0.043 nmol/mg protein in 12WT. Protein carbonyl content did not differ significantly among groups ( p = 0.188), although values were numerically higher in AME and 1WT than in CON. No statistically significant overall group difference was detected for plasma membrane fluidity ( p = 0.885), whereas mitochondrial membrane fluidity showed numerically lower values in all exercise groups compared with CON, although the overall group difference was not statistically significant ( p = 0.349). These findings indicate that hepatic oxidative and membrane-related profiles differed across treadmill-running conditions. However, because age- and time-matched sedentary controls were not included, differences between the baseline reference and the trained groups cannot be attributed exclusively to exercise exposure or training duration. Hepatic MDA + 4-HDA concentrations showed the clearest differences across conditions, whereas no statistically significant overall group differences were detected for protein carbonyl content or plasma and mitochondrial membrane fluidity.