Purpose: This study aimed to examine the effects of swimming exercise pretreatment on a streptozotocin (STZ)-induced sporadic Alzheimer's disease (AD) rat model and provide an initial understanding of related molecular mechanisms.
Methods: Male 2.5-month-old Sprague-Dawley rats were divided into the following four groups: (a) control, (b) swim + vehicle, (c) STZ without swim, and (d) swim + STZ. The Barnes maze task and novel object recognition test were used to measure hippocampus-dependent spatial learning and working memory, respectively. Immunofluorescence staining, Western blot analysis, enzyme-linked immunosorbent assay (ELISA) analysis, and related assay kits were used to assess synaptic proteins, inflammatory cytokines, total antioxidant capacity, antioxidant enzymes, amyloid-beta production, and tau hyperphosphorylation.
Results: Behavioral tests revealed that exercise pretreatment could significantly inhibit STZ-induced cognitive dysfunction (P < 0.05). STZ animals displayed significant loss of presynaptic/postsynaptic markers in the hippocampal CA1 that was reversed by exercise pretreatment (P < 0.05). STZ rats also displayed increased reactive gliosis, release of proinflammatory cytokines, and oxidative damage, effects attenuated by preexercise (P < 0.05, between-treatment changes). Likewise, preexercise significantly induced protein expression (P < 0.001) and DNA-binding activity (P = 0.015) of Nrf2 and downstream antioxidant gene expression in the hippocampal CA1 region (P < 0.05). STZ rats had increased levels of amyloid-beta (1-42) and tau hyperphosphorylation that were significantly ameliorated by exercise (P < 0.05). Histological studies showed that exercise imparted substantial neuroprotection (P < 0.001), suppressing neuronal apoptosis-like cell death in the hippocampal CA1 compared with the STZ control group (P < 0.001).
Conclusions: Exercise pretraining exerts multifactorial benefits on AD that support its use as a promising new therapeutic option for prevention of neurodegeneration in the elderly and/or AD population.