Diabetic neuropathy is the most common complication of diabetes. We investigate the effect of alpha-lipoic acid and insulin alone and in combination on changes in the phospholipids composition in the sciatic nerve of experimental diabetic neuropathy. A total of 120 male rats were used in this study. The experimental induction of diabetes in rats was induced by a single intraperetinoel (i.p) injection of 50 mg / kg of streptozotocin (STZ) freshly dissolved in citrate buffer, PH 4.5. After eight weeks of diabetes induction all rats were divided into six main equal groups, 20 animals each. Group I (control group): received no drugs, Group II (diabetic group), Group III (normal α-Lipoic acid-treated group), Group IV (diabetic alpha-Lipoic acid -treated group), Group V (diabetic insulin- treated group), Group VI (diabetic alpha-Lipoic acid and insulin-treated group). Eight weeks after diabetes induction therapeutic treatment with alpha-lipoic acid (54 mg/kg body weight i.p daily) and insulin (2U s.c daily) were given either alone or in combination and continued for six weeks. Equivalent volumes of saline were given subcutaneously to the rats in the other diabetic and non diabetic control groups. Blood samples and sciatic nerve tissues were collected at 4 and 6 weeks from the onset of treatment for determination of serum glucose and total cholesterol, total phospholipids and membrane phospholipids composition of sciatic nerve. The obtained results revealed that, diabetic neuropathy in rats resulted in marked increase in serum glucose level, sciatic nerve total cholesterol and phosphatidylglycerol contents. Treatment with α-lipoic acid significantly decreased serum glucose, phosphatidylglycerol and sphingomyelin contents with increase in total cholesterol content in sciatic nerve. Insulin treatment significantly increased total phospholipids and markedly decrease phospholipids composition of rat sciatic nerve including phosphatidylethanolamine, phosphatidylcholine, phosphatidylglycerol and sphingomyelin contents. Meanwhile, treatment with α-lipoic acid and insulin combination significantly decreased total phospholipids concentration and phospholipids composition in rat sciatic nerve including phosphatidylcholine, phosphatidylglycerol and sphingomyelin contents. These results indicate that, alterations in the amounts of phospholipids composition in sciatic nerve could be related to the physiological changes of early diabetic neuropathy. These results suggest that, administration of α-lipoic acid combined with insulin prevent hyperglycemia-induced changes in phospholipids composition suggesting its therapeutic potential in complications of diabetes and dibetes neuropathy.
Key words: diabetic neuropathy, sciatic nerve, phospholipids composition, alpha-Lipoic acid
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