Influence of apolipoprotein E genotype on blood redox status of Alzheimer's disease patients.

The blood redox status of probable Alzheimer's Disease (AD) patients and control subjects with distinct Apo E genotypes was investigated. It was assessed by measuring the levels of hydroperoxides (MDA) in plasma and erythrocytes, the levels of the antioxidant defense system (enzymatic and non-enzymatic) in plasma, erythrocytes, platelets and leukocytes, the activities of catechol-O-methyltransferase (COMT) in erythrocytes and monoamine oxidase-B (MAO-B) in platelets and also the activity of the mitochondrial respiratory chain in leukocytes. No significant differences were found between the Apo E genotype and MDA, uric acid, vitamin E and reduced-glutathione (GSH) levels in plasma; MDA, vitamin E, GSH, superoxide-dismutase (SOD), glutathione-peroxidase (GSH-Px) and COMT levels in erythrocytes; vitamin E levels in the platelets of AD patients and control subjects. However, the uric acid levels in plasma and the COMT levels in erythrocytes of AD patients and control subjects with the epsilon4 allele were significantly lower than those observed in control subjects without the epsilon4 allele. Moreover, the duraquinol oxidation level in leukocytes of AD patients with the epsilon4 allele was significantly higher than that in AD patients without the epsilon4 allele and control subjects with and without the epsilon4 allele. The meaning of these results is discussed in terms of involvement of oxidative stress in the etiopathogenesis of AD.

Effects of apolipoprotein E genotype on blood lipid composition and membrane platelet fluidity in Alzheimer's disease.

The blood lipid composition (plasma, platelets and leukocytes), platelet membrane fluidity, apolipoproteins A and B in the plasma of AD patients and control subjects with distinct Apo E genotypes were investigated. No significant differences were found between the Apo E genotype and the cholesterol, phospholipids, triglycerides and Apo B levels in the plasma; cholesterol and phospholipids levels in platelet and leukocyte membranes; and platelet membrane fluidity of AD and control groups. However, the phospholipid levels in the leukocyte membranes of the control subgroup with the genotypes epsilon3/epsilon3 and epsilon3/epsilon4 and the AD subgroups with the genotypes epsilon2/epsilon3 and epsilon3/epsilon3, epsilon3/epsilon4 and epsilon4/epsilon4 were significantly lower than those observed in the control subgroup with the genotype epsilon2/epsilon3. Moreover, the cholesterol and phospholipid levels in the platelet membranes of the AD subgroup with the epsilon2 allele were significantly higher than those in the AD subgroup without the epsilon2 allele and the control subgroups with and without the epsilon2 allele. A strong correlation was found between cholesterol and phospholipids levels in the platelet membranes of the AD and control subgroups without the epsilon2 allele, but the residual cholesterol level in the platelet membranes of the AD subgroup was twice that observed in the control subgroup. Furthermore, the Apo A levels in the plasma of the AD subgroup with the epsilon3 allele were significantly lower than those observed in the AD subgroup without the epsilon3 allele and the control subgroup with the epsilon3 allele. The results are discussed in terms of involvement of lipid metabolism in the etiopathogenesis of AD.

Apolipoprotein E genotype has no effect on the free intracellular Ca2+ concentration of platelets from Alzheimer's disease patients.

The free intracellular Ca2+ concentration [Ca2+]i of platelets was investigated in Alzheimer's disease (AD) patients and age-matched control subjects with distinct Apo E genotypes. No significant differences were found between the Apo E genotype and the [Ca2+]i levels of platelets (basal and alpha-thrombin stimulated) from AD patients and age-matched control subjects, suggesting that [Ca2+]i homeostasis of platelets from AD patients is independent of the Apo E genotype. The results are discussed in terms of involvement of Apo E and [Ca2+]i changes in the etiopathogenesis of AD.

Influence of vitamin E succinate on retinal cell survival.

In this study, we analyzed the influence of vitamin E succinate (5-80 microM), supplemented in the culture medium, on the survival of cultured retinal cells. The release of lactate dehydrogenase (LDH) was decreased in the presence of low concentrations (10-20 microM) of vitamin E succinate, whereas high concentrations (80 microM) induced a significant increase (about 2-fold) in the release of LDH, indicating a reduction of plasma membrane integrity. Supplementing with vitamin E succinate (80 microM) greatly enhanced its cellular content, as compared to vitamin E acetate (80 microM), and the membrane order of the retinal cells, as evaluated by the fluorescence anisotropy (r) of TMA-DPH (1-(4-(trimethylammonium)-phenyl)-6-phenylhexa-1,3,5-triene), was not altered. Furthermore, vitamin E succinate was more potent than vitamin E acetate in reducing thiobarbituric acid reactive substances (TBARS) formation upon ascorbate-Fe2+-induced oxidative stress (TBARS formation after cell oxidation decreased by about 15-fold or 1.6 fold, respectively, in the presence of 20 microM vitamin E succinate or 20 microM vitamin E acetate). A decrease in MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reduction induced by supplementing with vitamin E succinate (80 microM), to 35.99 +/- 1.96% as compared to the control, but not by vitamin E acetate (80 microM), suggests that vitamin E succinate may affect the mitochondrial activity. Vitamin E succinate also reduced significantly the ATP:ADP ratio in a dose-dependent manner, indicating that vitamin E succinate-mediated cytotoxic effects involve a decrement of mitochondrial function.

Thyroid-function assessment by use of enzyme immunoassays.

We used an enzyme immunoassay to determine the normal reference intervals for thyroxin, triiodothyronine, and thyrotropin in groups of children, ranging from newborns to 15-year-olds. Results compared well with those by radioimmunoassay. There were no substantial differences between plasma and serum samples for thyroxin and triiodothyronine, but thyrotropin concentrations differed significantly (p less than 0.05, n = 20 each).