Effects of insulin and ascorbic acid on inhibition of the apoptosis in hippocampus of STZ-lnduced diabetic rats

ABSTRACT

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. 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. 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