Lipoic acid decreases lipid peroxidation and protein glycosylation and increases (Na++K+)- and Ca++-ATPase activities in high glucose-treated human erythrocytes

Lipoic acid supplementation has been found to be beneficial in preventing n eurovascular abnormalities in diabetic neuropathy. Insufficient (Na+ + K+)- ATPase activity has been suggested as a contributing factor in the developm ent of diabetic neuropathy. This study was undertaken to test the hypothesi s that lipoic acid reduces lipid peroxidation and glycosylation and can inc rease the (Na+ + K+)- and Ca++-ATPase activities in high glucose-exposed re d blood cells (RBC). Washed normal human RBC were treated with normal (6 mM ) and high glucose concentrations (45 mM) with 0-0.2 mM lipoic acid (mixtur e of S and R sterioisomers) in a shaking water bath at 37 degreesC for 24 h . There was a significant stimulation of glucose consumption by RBC in the presence of lipoic acid both in normal and high glucose-treated RBC. Lipoic acid significantly lowered the level of glycated hemoglobin (GHb) and lipi d peroxidation in RBC exposed to high glucose concentrations. High glucose treatment significantly lowered the activities of (Na+ + K+)- and Ca++-ATPa ses of RBC membranes. Lipoic acid addition significantly blocked the reduct ion in activities of (Na+ + K+)- and Ca++ -ATPases in high glucose- treated RBC. There were no differences in lipid peroxidation, GHb and(Na+ + K+)- a nd Ca++-ATPase activity levels in normal glucose-treated RBC with and witho ut lipoic acid. Thus, Lipoic acid can lower lipid peroxidation and protein glycosylation, and increase (Na+ + K+)- and Ca++-ATPase activities in high- glucose exposed RBC, which provides a potential mechanism by which lipoic a cid may delay or inhibit the development of neuropathy in diabetes. (C) 200 0 Elsevier Science Inc.