Alterations in plasma vitamin E distribution in type 2 diabetic patients with elevated plasma phospholipid transfer protein activity

Mouse studies indicated that plasma phospholipid transfer protein (PLTP) determines the plasma distribution of vitamin E, a potent lipophilic antioxidant. Vitamin E distribution, antioxidant status, and titer of anti-oxidized LDLs (oxLDL) autoantibodies were evaluated in plasma from control subjects (n = 31) and type 2 diabetic patients (n = 31) with elevated plasma PLTP concentration. Unlike diabetic and control HDLs, which displayed similar vitamin E contents, diabetic VLDLs and diabetic LDLs contained fewer vitamin E molecules than normal counterparts. Plasma PLTP concentration in diabetic plasmas correlated negatively with vitamin E in VLDL+LDL, but positively with vitamin E in HDL, with an even stronger correlation with the VLDL+LDL-to-HDL vitamin E ratio. Circulating levels of oxLDL were significantly higher in diabetic plasmas than in control plasmas. Whereas the titer of IgG autoantibodies to modified LDL did not differ significantly between diabetic patients and control subjects, diabetic plasmas showed significantly lower levels of potentially protective IgM autoantibodies. The present observations support a pathophysiological role of PLTP in decreasing the vitamin E content of apolipoprotein B-containing lipoproteins, but not of HDL in plasma of type 2 diabetic patients, contributing to a greater potential for LDL oxidation.