Abstract

Type 2 diabetes (T2D) is a chronic metabolic disorder known to impair male reproductive function through mechanisms involving insulin resistance, hyperglycemia, and oxidative stress. This study aimed to investigate the potential of red rice bran extract (RBE), a dietary antioxidant, alone or in combination with metformin (Met), in alleviating reproductive dysfunction in a T2D rat model. Male Wistar rats were divided into five groups: non-diabetic control, untreated diabetic, RBE-treated diabetic, Met-treated diabetic, and RBE+Met-treated diabetic. Diabetes was induced by a high-fat diet followed by a low-dose streptozotocin injection. After confirmation of diabetes, treatments were administered orally once daily for 12 weeks. Reproductive and oxidative stress markers were evaluated, including serum testosterone, sperm quality, Johnsen score (a histological index of spermatogenesis), antioxidant enzyme activities, and testicular histology. Diabetic rats showed significant reductions in testosterone levels, sperm parameters, Johnsen score, and testicular morphology, along with elevated malondialdehyde and reduced superoxide dismutase and glutathione levels. Treatment with RBE and/or Met improved sperm concentration, Johnsen score, and testicular architecture, and attenuated oxidative stress. However, sperm motility and testosterone levels did not return to control levels. These findings suggest that RBE may serve as a natural adjunctive therapy for diabetes-induced male reproductive impairment and warrant further investigation.

Key words: rice bran extract, oxidative stress, diabetes, testicular dysfunction, metformin