Lipoic acid restores antioxidant system in tissues of hyperinsulinaemic rats

Feeding rats with high fructose induces insulin resistance, hyperinsulinaemia, elevation of blood glucose level and impaired glucose tolerance. Oxidative stress plays a vital role in pathology associated with insulin resistance. The present study was to investigate the effects of alpha-lipoic acid (LA) on the oxidant-antioxidant balance in liver and kidney of high fructose-fed rats.

Male Wistar rats (170-180 g) were divided into six groups. The control group received diet containing starch; the fructose group was given a high fructose diet (>60% of total calories); the third and fourth groups were given fructose diet and administered with two different doses of lipoic acid as low dose (35 mg/kg body weight) and high dose (70 mg/kg bw) intraperitoneally using olive oil as vehicle; the fifth group received control diet and was administered with lipoic acid (70 mg/kg bw); the sixth group received the control diet and olive oil. The rats were maintained in their respective dietary regimen for 20 days. Lipid peroxidation indices and antioxidant status in liver and kidney were quantitated.

The rats fed fructose showed increased levels of lipid hydroperoxides, thiobarbituric acid reactive substances (TBARS), conjugated dienes, and impaired antioxidant defence potential as evidenced by a decrease in the levels of non-enzymatic and enzymatic antioxidants. Treatment with LA to the fructose-fed rats mitigated these alterations and LA was effective uniformly at both the closes. Increased lipid peroxidation and inadequate antioxidant system are observed in the high dose fructose-fed rats.

LA administration restored the antioxidant potential and lowered lipid peroxidation. These findings strengthen the utility of LA in the management of insulin resistance and associated pathology.