Effects of Insulin and Ascorbic Acid on Inhibition of the Apoptosis in Hippocampus of Stz-Induced Diabetic Rats

Purpose: The aim of this study was to investigate effects of insulin and ascorbic acid on rate of Caspase – 3 activity and DNA Laddering in hippocampus of STZ-induced diabetic rats.Materials and Methods: Thirty male Wistar rats in five groups, 6 in each group: one control group (group C) and four diabetic groups [diabetic control (group D), treatment with insulin (group I), with ascorbic acid (group AA) and with insulin plus ascorbic acid (group I+AA)] were used in this study. Diabetes was induced by injection of 60 mg/kg STZ IP. After six weeks, rats in group I were treated with insulin (4-6 U/kg/day Sc.), rats in group AA treated with ascorbic acid (200 mg/kg/day, IP) and rats in group I+AA treated with equal dosage of both insulin and ascorbic acid for two weeks. Rats in group D were treated with saline and considered as the diabetic control group. Two weeks after treatment, animals were anesthetized and hippocampus was dissected from hemispheres. Caspase-3 activity was assessed by Fluorometry, and finally, DNA fragmentation due to apoptosis was determined by DNA laddering Assay.Results: Caspase-3 activity in group D significantly increased compared to group C (6.7 fold), whereas it decreased after treatment with insulin, ascorbic acid or both (2.6, 4.2 and 5.1 fold, respectively). DNA laddering was observed in group D, but not in three treated groups.Conclusions: From this survey it was concluded that treatment of STZ-induced diabetic rats with insulin and/or L-ascorbic acid could possibly inhibit apoptosis in hippocampal tissues using decrease of Caspase -3 activity and prevention of DNA Laddering.