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Hyperglycemia-induced oxidative stress in diabetic conditions promotes alterations of function and other properties of the erythrocyte membrane. In this study, we examined the effects of palm vitamin E (200 mg/kg) on oxidative stress and the physical and morphological characteristics of erythrocyte membranes in streptozotocin-induced diabetic rats. Forty male rats were randomly divided into 4 groups as follows: Group 1, control group; Group 2, normal plus palm vitamin E treatment; Group 3, untreated diabetic group; and Group 4, diabetic plus palm vitamin E treatment. After 4 weeks of treatments, we determined complete blood count, erythrocyte osmotic fragility, erythrocyte morphology, levels of erythrocyte malondialdehyde and protein carbonyl, levels of erythrocyte glutathione and oxidized glutathione, and total plasma antioxidant capacity. The results of osmotic fragility were significantly higher in the diabetic group compared to the control and diabetic with palm vitamin E. There were significant morphological changes in the erythrocytes of the diabetic group compared to the control group. We also found a significant decrease in the hemoglobin concentration, hematocrit percentage, and erythrocyte distribution width in the diabetic group. Erythrocyte malondialdehyde and protein carbonyl levels were significantly higher in the diabetic group compared to the control group. Decreased levels of reduced glutathione and increased level of oxidized glutathione were observed in the diabetic group compared to the control and diabetic with palm vitamin E groups. Plasma total antioxidant capacity was significantly lower in the diabetic group than in the control group, whereas plasma total antioxidants in the diabetic with palm vitamin E group were significantly increased compared to the untreated diabetic group. In conclusion, 4 weeks of daily supplementation with 200 mg/kg palm vitamin E could reduce the levels of oxidative stress markers by inhibiting lipid peroxidation and protein oxidation in streptozotocin-induced diabetic rats.

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BACKGROUND: Tocotrienol-rich fraction (TRF) from palm oil has been shown to exhibit potent antioxidative properties in various pathological conditions. This study aimed to determine the antioxidative properties of TRF on the plasma and erythrocyte membrane lipids composition in streptozotocin-induced diabetic rats.METHODS: Male Sprague-Dawley rats (n=40) were divided randomly into four groups of 10, which were a normal group, a normal group with TRF, a diabetic group, and a diabetic group with TRF. Following four weeks of treatment, lipids compositions in the plasma and erythrocyte membrane were investigated.RESULTS: TRF significantly reduced the plasma total cholesterol, to that in the diabetic group. In addition, supplementation of TRF was able to reduce the very low density lipoprotein cholesterol (VLDL-C), triglycerides levels in treated diabetic rat although no significant different was observed when compared with untreated diabetic rats alone. Furthermore, TRF supplementation showed increased the levels of phosphatidylinositol, phosphatidylserine, and total phospholipid levels in diabetic rats. However, the linoleic acid (18:2) levels were reduced in diabetic rats compared to the control group, and the eicosadienoic acid (20:2) levels were significantly increased by TRF supplementation in diabetic rats.CONCLUSION: Supplementation with 200 mg/kg TRF improves dyslipidemia and that TRF, therefore, might have protective effects against oxidative damage of phospholipids. This study also showed the antioxidative properties of TRF on the erythrocyte membrane lipids composition, in particular, its protective effects against peroxidation of unsaturated fatty acids.KEYWORDS: antioxidative property, cholesterol, fatty acids, phospholipids, tocotrienol-rich fraction