THE EFFECT OF NICOTINIC ACID ON GLUCOSE TOLERANCE AND LIPID PROFILE IN NORMAL AND STREPTOZOTOCIN INDUCED DIABETIC RATS
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This study was carried out to investigate the effects of nicotinic acid (NA) on lipid profile, glucose and insulin levels in normal and streptozotocin (514 inclt icrd diabetic rats.6 groups of albino rats ( each consists of 10 rats) were used in this study. Group (1) & (2) were done to detect the effects of NA in normal rats .Group (1) served as control group without any medication Group (2) received daily intraperitoneal (II') injection of NA . After 4 weeks, rats were fasted overnight' and blood samples were collected by intracardiac puncture and the following parameters were estimated : Fasting blood glucose. insulin, cholesterol triglycerides , HDL and LDL . Our results showed that NA resulted in a significant decrease in levels of glucose, insulin , cholesterol, triglycerides and LDL but caused a significant increase in HDL level . Groups (3) & (4) were planned to study the protective effect of NA added to diet on development of STZ diabetic rats. The rats of group (3) were given a normal diet while group (4) were given a diet supplemented with NA for 4 weeks , then both groups were given a single IP injection of STZ for 4 weeks . Blood samples were collected by the same method used with groups (1)& (2) and the same parameters were estimated. We found that addition of NA in diet caused a significant reduction in fasting blood glucose, cholesterol, triglycerides and LDL while caused a significant increase in serum insulin and HDL levels. Groups (5) &(6) were carded out to study the possible curative effect of NA in 522 induced diabetic rats. Rats of group (5) were given a single IP injection of STZ while rats of group (6) were given a single IP injection of STZ then received daily IP injection of NA. After 4 weeks . blood samples were collected by the same method mentioned previously and sera were estimated for the same parameters as we did with the former 4 groups . We found marked significant reduction in fasting blood glucose, cholesterol triglycerides and LDL with marked significant increase in serum insulin and HDL in group(6) compared to group (5) . In conclusion: NA administration resulted in a significant increase in HDL and a significant decrease in levels of fasting blood glucose, cholesterol, triglycerides and LDL in normal and STZ induced diabetic rats . The cause of glucose decreasing effect may be inhibition of gluconeogensis and improving insulin sensitivity. As regards insulin level, NA showed controversy effect. It caused a decrease in insulin level in normal rats while in b/Z induced diabetic rats it increased insulin Level. The mechanism in diabetic rats may be the protective effect of NA in the form of returning of )3-cell of pancreas to its normal morphology. In normal rats this effect negligible and overcome by insulin lowering effect of decreased PTA occurred after NA administration. It could be concluded that NA proves efficiency in diabetic prevention and management.