Abstract: BACKGROUND: Prolonged exhaustive exercise can easily cause ischemia and hypoxia in rats, leading to brain tissue damage. Pueraria lobata flavonoids can exert a series of roles, including cardiovascular and cerebrovascular protections, improvement of brain damage and anti-oxidation. However, whether supplementation of Pueraria lobata flavonoids prior to exercise can protect the brain tissue is still unclear.
OBJECTIVE: To observe the effect of total flavonoids in Pueraria lobata on histopathological changes and expressions of β-catenin and glycogen synthase kinase 3β in rats undergoing exercises.
METHODS: Fifty Sprague-Dawley male rats were randomly divided into five groups: a quiet control group, an exercise control group, and low-, medium-and high-dose groups of total flavonoids in Pueraria lobata. Except the quiet control group, the remaining groups were trained for 6 weeks, while the last training reached exhaustion on the 6th weekend. In the low-, middle- and high-dose groups, all the rats were given 50, 100, 200 mg/kg total flavonoids in Pueraria lobata by gavage at 20 minutes before the experiment once a day until the end of the experiment. In all the groups, hematoxylin-eosin staining was used to observe the histopathological changes of the brain, and immunohistochemistry, PCR and western blot were used to determine the expressions of β-catenin and glycogen synthase kinase 3β. 
RESULTS AND CONCLUSION: Under the light microscope, in the exercise control group, some nerve cells in the cerebral cortex and hippocampus became swollen and contracted, and there were edema, hyperemia and bleeding in the meninges or ependymal membranes. The low-dose group appeared to have some mild symptoms, such as edema, congestion and hemorrhage. However, the pathological changes in the brain tissue of rats in the middle- and high-dose groups were not significantly different from those in the quiet control group. Immunohistochemical staining showed that the expression levels of β-catenin and glycogen synthase kinase 3β in the brain tissue of the exercise control group were higher than those in the quiet control group (P < 0.01). In the middle- and high-dose group, the expression levels of β-catenin and glycogen synthase kinase 3β in the brain tissue were lower than those of the exercise control group (P < 0.01). The mRNA and protein expressions of β-catenin and glycogen synthase kinase 3β in the brain tissue of the exercise control group were higher than those in the quiet control group (P < 0.05 or P < 0.01). The expressions of β-catenin and glycogen synthase kinase 3β mRNA and protein in the middle- and high-dose groups were lower than those in the exercise control group (P < 0.05 or P < 0.01). To conclude, exhaustive exercise could give rise to damage in the rat brain tissue, and upregulate the expressions of β-catenin and glycogen synthase kinase 3β, whereas the total flavonoids in Pueraria lobata may effectively reduce damage to the rat brain tissue by regulating the expressions of β-catenin and glycogen synthase kinase 3β, thereby protecting the brain tissue.

Key words: total flavonoids in Pueraria lobata, exhaustive exercise, brain tissue, β-catenin, glycogen synthase kinase 3β, pathway, rat