High Dosage Vitamin E Effect on Oxidative Status and Serum Lipids Distribution in Streptozotocin-Induced Diabetic Rats

This study was performed to determine whether vitamin E supplementation in streptozotocin-induced diabetic rats treated by insulin could reduce serum oxidation markers (malondialdehyde:MDA, Schiff bases, anti-protein-MDA adduct antibodies) and modulate lipid changes. After 10 weeks, diabetes induced in rats a significant increase in Schiff bases (P < 0.006) and anti-protein-MDA adduct antibodies (P < 0.01). These alterations were accompanied by a significant rise in serum free fatty acids (225%), triglycerides (35%), and phospholipids (30%) and changes in fatty acid distribution in these fractions and in cholesterol esters. Vitamin E supplementation in diabetic rats reduced Schiff bases and antiprotein-MDA adduct antibodies and tended to restore the fatty acid profile close to control rats without decreasing quantitatively serum lipids enhanced by diabetes. Concerning fatty acids, vitamin E chiefly reduced stearic acid (C18:0) in free fatty acids, cholesterol esters, and phospholipids and cancelled the decrease in low molecular triglycerides observed in diabetic rats. Furthermore, vitamin E maintained the ratio of monounsaturated and polyunsaturated fatty acids, particularly with respect to oleic acid (C18:1), dihomo-γ-linolenic acid (C20:3 n-6), eicosapentaenoic (C20:5 n-3), and docosapentaenoic acid (C22:5 n-3), in serum phospholipids. These changes observed in vitamin E supplemented rats, compared to vitamin E-untreated diabetic rats, could favor prevention of accelerated atherogenesis. Particularly, the decrease of serum peroxides and enhancement in phospholipid fatty acids (C20:3 n-6, C20:5 n-3, and C22:5 n-3) could induce the preferential formation of prostaglandins (PGE₁, PGI₂, PGI₃) which are protective in cardiovascular diseases.