Sesamin: A promising protective agent against diabetes-associated cognitive decline in rats

Hippocampal oxidative stress and apoptosis of CA1 neurons play significant roles in the pathophysiology of diabetes-associated cognitive decline (DACD). The present study was aimed to elucidate the putative effects of sesamin, a major lignan of sesame seed, against DACD, and possible involvement of anti-oxidative and anti-apoptotic mechanisms. Fifty adult male Wistar rats were randomly divided into control, control-sesamin (30 mg/kg/day), diabetic, diabetic-sesamin (30 mg/kg/day), and diabetic-insulin (6 IU/rat/day) groups. Diabetic rats were treated with sesamin (P.O.) or insulin (S.C.) for eight consecutive weeks. Cognitive performance was evaluated in a Morris Water Maze (MWM) test; in addition, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) concentrations were assayed in the hippocampus using assay kits. Moreover, hematoxylin-eosin (HE), TUNEL, and immunohistochemistry (IHC) stainings were conducted to evaluate histological changes, the apoptosis status and expression of pro- and anti-apoptotic proteins in the hippocampal CA1 neurons, respectively. The results showed that diabetes reduced the spatial cognitive ability in MWM, which was accompanied by decrease in SOD, CAT, and GPx activities and increase in MDA level in the hippocampus. Additionally, diabetes resulted in neuronal loss, enhanced apoptotic index, elevated the expression of pro-apoptotic Bax protein, and decreased the expression of anti-apoptotic Bcl-2 protein in the hippocampal CA1 neurons. Interestingly, sesamin treatment improved all the above-mentioned deficits of diabetes at a comparable level with insulin therapy. The results suggest that sesamin could be a promising potential therapeutic agent against DACD, possibly through its intertwined anti-hyperglycemic, anti-oxidative, and anti-apoptotic properties.