α-Tocopherol status and expression of α-tocopherol transfer protein in type 2 diabetic Goto-Kakizaki rats

Vitamin E, a critical fat-soluble vitamin antioxidant, is expressed on cell membranes and prevents propagation of lipid peroxidation. α-Tocopherol transfer protein (α-TTP) is a cytosolic protein located in the hepatocytes that acts as the principal regulator of the circulating α-tocopherol levels. Type 2 diabetes is a metabolic disorder characterized by hyperglycemia, caused by insulin resistance. Lipid peroxidation promotes the clinical progression and development of complications in type 2 diabetes. Results of animal and human experiments on the vitamin E status in diabetes are conflicting. The present study was conducted with the objective of investigating the vitamin E status and α-TTP expression in Goto-Kakizaki (GK) rats, a model of type 2 diabetes. In diabetic GK rats, increases of the α-tocopherol levels in the plasma and liver were observed as compared with the levels in the controls. No alternation in the CuZn-superoxide dismutase (SOD) or Mn-SOD gene expression was found in the liver of GK rats as compared with that in the controls. The GK rats showed an increase of the hepatic expression of the α-TTP gene as compared with the level in the controls. It can be suggested that the increased hepatic α-TTP gene expression levels may influence plasma α-tocopherol levels in the diabetic animals. Hence, investigation of the regulatory factors of α-TTP expression may provide important clues to highlighting the antioxidant mechanisms of vitamin E.