Dietary vitamin C and E modulates antioxidant levels in blood, brain, liver, muscle, and testes in diabetic aged rats

Abstract

While tissue dysfunction is a well-recognized consequence of diabetes mellitus in aged people, the underlying mechanisms are poorly understood. Daily (VCE) supplementation of vitamins C and E can be beneficial to diabetic aged animals in reducing free radical production. The aim of this study was to investigate whether dietary VCE supplementation modulates oxidative stress and antioxidant redox systems in streptozotocin (STZ)-induced aged diabetic rats. Thirty aged rats (18 - 20 months) were randomly divided into three groups. The first group acted as a control and the second group was diabetic. VCE-supplemented feed was given to aged, diabetic rats, constituting the third group. Diabetes was induced using a single dose of intraperitoneal STZ. On the 21(st) day after STZ dosage, blood and tissue samples were taken from all animals. Glutathione peroxidase activity in liver, erythrocytes, muscle, and testes; catalase activity in plasma and erythrocytes; reduced glutathione levels in plasma; vitamin E concentration in plasma, liver, and muscle; b-carotene concentration in brain; and high-density lipoprotein (HDL)-cholesterol levels in plasma were lower in the diabetic group than in the control group. Lipid peroxidation (LP) levels in plasma, liver, brain, and muscle, and alanine aminotransferase (ALT), aspartate aminotransferase (AST), triacyglycerols, and total and low-density lipoprotein (LDL)-cholesterol values in plasma were higher in the diabetic group than in the control group. The LP, enzyme, vitamin, and lipid profile values levels were mostly restored by VCE treatment. Liver and testis weights did not change by diabetic status and VCE supplementation, although body weight was lower in the diabetic group than in the control group. In conclusion, brain, liver, and testes tissues seem most sensitive in aged diabetic rats to oxidative stress. We observed that VCE supplementation relieves oxidative stress in the blood and tissues of diabetic aged rats by modulating the antioxidant system and lipid profile.