Treadmill exercise ameliorates apoptotic cell death in the retinas of diabetic rats

Apoptotic neuronal cell death in the retina is a hallmark of diabetic retinopathy. Exercise has been recommended for the alleviation of symptoms in patients with diabetes. In the present study, the effect of treadmill exercise on apoptosis in the retinas of diabetic rats was investigated. Diabetes was induced by intraperitoneal injection of streptozotocin. The rats in the exercise groups ran on a treadmill for 30 min/day, 5 times a week, over the course of 6 weeks. In this study, the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, immunohistochemistry staining of caspase-3 and western blot analysis for Bax, Bcl-2 and phosphorylated protein kinase B (p-Akt) in the retinas of diabetic rats were performed. The results demonstrated that the number of TUNEL-and caspase-3-positive cells was increased in the retinas of diabetic rats, whereas treadmill exercise decreased these numbers. In addition, the expression of the pro-apoptotic protein Bax and the anti-apoptotic protein Bcl-2 was enhanced in the retinas of diabetic rats. Treadmill exercise suppressed Bax and enhanced Bcl-2 levels. The expression of the cell survival factor, p-Akt, was decreased in the retinas of diabetic rats and treadmill exercise increased the expression of p-Akt. The results of the present study demonstrated that treadmill exercise ameliorated diabetes-induced apoptosis in retinal cells by enhancing p-Akt levels in the retina. Treadmill exercise represents an effective strategy to delay or prevent the onset of ocular complications in diabetic patients.