Spatial memory in sedentary and trained diabetic rats: Molecular mechanisms

ABSTRACT Diabetes mellitus is a chronic disease that has been associated with memory loss, neurological disorders, and Alzheimer's disease. Some studies show the importance of physical exercise to prevent and minimize various neurological disorders. It is believed that the positive effects of exercise on brain functions are mediated by brain insulin and insulin‐like growth factor‐1 (IGF‐1) signaling. In this study, we investigate the role of swimming exercise training on hippocampus proteins related to insulin/IGF‐1 signaling pathway in Type 1 diabetic rats and its effects on spatial memory. Wistar rats were divided into four groups namely sedentary control, trained control, sedentary diabetic (SD), and trained diabetic (TD). Diabetes was induced by Alloxan (ALX) (32 mg/kg b.w.). The training program consisted in swimming 5 days/week, 1 h/day, per 6 weeks, supporting an overload corresponding to 90% of the anaerobic threshold. We employed ALX‐induced diabetic rats to explore learning and memory abilities using Morris water maze test. At the end of the training period, the rats were sacrificed 48 h after their last exercise bout when blood samples were collected for serum glucose, insulin, and IGF‐1 determinations. Hippocampus was extracted to determinate protein expression (IR, IGF‐1R, and APP) and phosphorylation (AKT‐1, AKT‐2, Tau, and β‐amyloide proteins) by Western Blot analysis. All dependent variables were analyzed by two‐way analysis of variance with significance level of 5%. Diabetes resulted in hyperglycemia and hypoinsulinemia in both SD and TD groups (P