Vitamin D Improves Learning and Memory Impairment in Streptozotocin-Induced Diabetic Mice

Diabetes mellitus (DM) is associated with memory and learning deficits. Evidence has been provided that vitamin D is involved in brain function. The aim of the present study was to determine the potential effect of vitamin D on acquisition and retention of memory and learning in streptozotocin (STZ)-induced diabetic mice.

Experiments were performed in four groups of mice (each group; n = 7). Male mice were induced to diabetes by single dose (60 mg/kg, i.p.) injection of freshly prepared STZ dissolved in cold normal saline. Treatment with vitamin D (5µg/kg daily, i.p. dissolved in tween80) was begun at three days after diabetes induction. Passive avoidance (PA) learning method was used four weeks later. Retrieval test was carried out 24 h after training.

Our results demonstrate significant impairment in acquisition and retrieval processes of PA learning in STZ- induced diabetic mice. Treatment with vitamin D improved learning and memory compared to the control group, both in acquisition and retrieval stages and reversed learning deficits in diabetic mice. In acquisition test, there were significant differences in the initial latency among the DM+Vit. D treated and control groups (P < 0.05). There was a significant difference in step-through latency between diabetic group treated with vitamin D compared to diabetic non-treated groups (P < 0.05).

It is possible that the effects of Vitamin D on cognitive deficits in STZ-induced diabetic mice could be mediated through calcium homeostasis modulation. These findings suggest a potential role for vitamin D in the treatment of diabetes-associated cognition deficits. The positive effect of vitamin D on the avoidance task may be attributed to its neuronal protective roles metabolic regulating roles of prolonged vitamin D administration.