The transport of vitamin E in plasma and its correlation to plasma lipoproteins in non-insulin-dependent diabetes mellitus

Abstract

It is known that plasma low density lipoproteins (LDL) contain a great amount of vitamin E and that LDL enter cells via the specific receptor-mediated mechanism. In this study, we aimed to investigate the transport of alpha-tocopherol from plasma to tissues in subjects with non-insulin-dependent diabetes mellitus (NIDDM) with poor glycaemic control; and the relationships between alpha-tocopherol and plasma lipid and lipoprotein levels. alpha-Tocopherol determination was carried out by colorimetric assay according to the modified micromethod of Fabianek et al. The mean plasma alpha-tocopherol and (LDL + VLDL)-alpha-tocopherol levels increased significantly in the diabetic group as compared to control (P less than 0.05 and P less than 0.02), whereas the high density lipoprotein (HDL)-alpha-tocopherol level was significantly lower in the diabetic group than that in the controls (P less than 0.05). Correlations between plasma alpha-tocopherol levels showed close positive relationships (r = 0.87, r = 0.75 and r = 0.78, respectively, P less than 0.001). A strong positive correlation was also observed between alpha-tocopherol and the cholesterol content, either in the HDL or in the (LDL + VLDL) fractions (r = 0.75 and r = 0.77; P less than 0.001). These findings indicate that there is a direct positive relationship between lipid and alpha-tocopherol concentrations. The increased level of alpha-tocopherol in the LDL + VLDL fraction and decreased level in HDL in these patients could be attributed to the impairment of the cholesterol uptake of the cells by the receptor mediated mechanism.