Effects of Fixed-Speed Treadmill Exercise on Oxidative Stress and Sirtuin Biomarkers in Young and D-Galactose-Treated Rats: A Biochemical Study with Exploratory Hippocampal Observations

Exercise is proposed to influence oxidative stress and mitochondrial-biogenesis pathways relevant to brain aging, but how exercise intensity relates to these markers alongside hippocampal structure remains unclear. This study examined treadmill exercise at three fixed speeds (15, 20, 30 m/min), corresponding to literature-derived, non-individually validated nominal intensity classifications (~40–50%, 55–65%, 70–75% VO2max), on biochemical markers (PGC-1α, MDA, SIRT2, BDNF, irisin) and, as a secondary outcome, hippocampal histology, in young rats and in rats with D-galactose-induced accelerated aging. Sixty-four male Wistar Albino rats (3 months old, 220–350 g) were assigned to control and low-, moderate-, and high-intensity exercise groups within each model category (n = 8/group); after six weeks, serum was collected for biochemical analyses and brain tissue was collected for exploratory histological evaluation. In young rats, MDA and SIRT2 differed significantly among groups (p < 0.05); PGC-1α, BDNF, and irisin did not. In D-galactose-treated rats, none of the five markers differed significantly; MDA and SIRT2 showed large effect sizes (ε2 = 0.207 and 0.199) despite non-significant p-values; given the small sample size, this should be read as an imprecise estimate consistent with a range of true effects, including no effect, rather than as evidence of a masked effect. Qualitative, single-rater H&E staining suggested greater dentate gyrus granule-cell density in exercised D-galactose-treated rats versus controls; without neuronal, neurogenesis, or glial markers, this remains a preliminary, hypothesis-generating impression rather than confirmed evidence of neurogenesis. Overall, treadmill exercise was associated with significant changes in oxidative-stress and sirtuin markers across nominal exercise intensities in young rats, the study’s primary contribution; the histological observation requires confirmation with quantitative stereology, specific immunomarkers, and behavioral testing before mechanistic claims can be made.