[Regulatory effect of curcumin on renal apoptosis and its mechanism in overtraining rats].

Objective: To study the effects and mechanisms of curcumin alleviating oxidative stress induced by overtraining and inhibiting renal apoptosis in rats.

Methods: Male Wistar rats of 7 weeks old were divided into control group (C group, 12), overtraining group (OM group, 11), curcumin + overtraining group (COM group, 14). Group C did not undergo any exercise intervention. Rats in OM group and COM group underwent 8-week incremental load swimming training. During the training, the COM group was treated with curcumin at the dose of 200 mg/(kg·d) in the volume as 5 ml/kg by intragastric administration, and the other groups was treated with an equal volume of 0.5% carboxymethylcellulose. Twenty-four hours after the last training, renal histopathological changes were observed by light microscopy, related biochemical indicators in blood and renal tissue were detected.

Results: The results showed that after 8 weeks of incremental load swimming training, the renal tissue structure of group C was normal under light microscope; histopathological changes were observed in OM group; COM group was significantly relieved compared with OM group. Compared with group C, serum levels of corticosterone (Cor), creatinine (Cr) and blood urea nitrogen (BUN) in OM group were increased (<0.01), serum level of testosterone (T) was lower (<0.01); the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) was not changed significantly (>0.05), while the expression of heme oxygenase-1 (HO-1) was decreased (<0.05), total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity were decreased (<0.01), malondialdehyde (MDA) concentration was increased (<0.01); the renal apoptosis was increased (<0.01), the expression of anti-apoptotic B cell lymphoma-2 protein (Bcl-2) was decreased (<0.01), and the expression of proapoptotic Bcl-2 associated X protein (Bax) was increased (<0.01). Compared with the OM group, Cor level was decreased (<0.01) in the COM group, T level was increased (<0.01), Cr and BUN levels were lower (<0.05); the expression of Nrf2 and HO-1 were increased (<0.05), T-AOC and SOD activity were increased (<0.01), MDA concentration was decreased (<0.05); the renal apoptosis was decreased (<0.05), the expression of Bcl-2 was increased (<0.05), and the expression of Bax was decreased (<0.01). The trend of testosterone/corticosterone ratio between groups was consistent with testosterone change, and the change trend of Bcl-2/Bax ratio was consistent with the change of Bcl-2.

Conclusions: The 8-week incremental load swimming training triggered excessive training in rats, aggravated oxidative stress and accelerated renal apoptosis, leading to pathological changes and dysfunction of kidney. Curcumin can up-regulate expression of Nrf2 and HO-1, effectively alleviates oxidative stress induced by overtraining, thereby increasing Bcl-2 expression, decreasing Bax expression, inhibiting renal apoptosis and protecting renal tissue structure and function properly.