Validation of an immunoassay for measurement of plasma total homocysteine.

Hyperhomocysteinemia is an evolving cardiovascular risk factor. It is imperative that a simple, precise, and accurate assay be available in the clinical laboratory. The aim of this study was to evaluate an automated fluorescence polarization immunoassay for homocysteine. The assay had excellent precision at normal and high levels (intra-assay and interassay coefficients of variation < 5%). The method was linear from 0.24 to 50 mumol/L and displayed good correlation with a high-performance liquid chromatography (HPLC) method. There was no significant interference detectable in icteric and hyperlipidemic samples, but hemolysis resulted in a significant negative bias. While homocysteine levels were not increased in smokers, patients with renal failure had significantly higher levels compared with control subjects. This automated assay requires no sample preparation, displays excellent precision, shows good correlation with HPLC, and, thus, is favored over HPLC for use in the clinical laboratory. The main indications for measuring plasma homocysteine levels will be in the early diagnosis of cobalamin deficiency, patients with cardiovascular disease and few or no established risk factors, and patients with unexplained venous thromboembolic disease.

Comparison of the effect of alpha-lipoic acid and alpha-tocopherol supplementation on measures of oxidative stress.

In vitro studies have shown that alpha-lipoic acid (LA) is an antioxidant. There is a paucity of studies on LA supplementation in humans. Therefore, the aim of this study was to assess the effect of oral supplementation with LA alone and in combination with alpha-tocopherol (AT) on measures of oxidative stress. A total of 31 healthy adults were supplemented for 2 months either with LA (600 mg/d, n = 16), or with AT (400 IU/d, n = 15) alone, and then with the combination of both for 2 additional months. At baseline, after 2 and 4 months of supplementation, urine for F2-isoprostanes, plasma for protein carbonyl measurement and low-density lipoprotein (LDL) oxidative susceptibility was collected. Plasma oxidizability was assessed after incubation with 100 mM 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH) for 4 h at 37 degrees C. LDL was subjected to copper- and AAPH-catalyzed oxidation at 37 degrees C over 5 h and the lag time was computed. LA significantly increased the lag time of LDL lipid peroxide formation for both copper-catalyzed and AAPH-induced LDL oxidalion (p < .05), decreased urinary F2-isoprostanes levels (p < .05), and plasma carbonyl levels after AAPH oxidation (p < .001). AT prolonged LDL lag time of lipid peroxide formation (p < .01 ) and conjugated dienes (p < .01) after copper-catalyzed LDL oxidation, decreased urinary F2-isoprostanes (p < .001), but had no effect on plasma carbonyls. The addition of LA to AT did not produce an additional significant improvement in the measures of oxidative stress. In conclusion, LA supplementation functions as an antioxidant, because it decreases plasma- and LDL-oxidation and urinary isoprostanes.

Diet, antioxidant status, and smoking habits in French men.

The aim of this study was to assess the association between smoking, food consumption, and antioxidant vitamin intake and plasma indexes of oxidative stress and antioxidant defenses in French adults. Food and nutrient intakes of 459 healthy men aged 23-57 y were estimated by the diet history method and analyzed by smoking status. Plasma alpha-tocopherol, ascorbic acid, and carotenoids were measured as antioxidants and malondialdehyde, protein Schiff bases, and autoantibodies against malondialdehyde-protein adducts as oxidative stress indexes. Smokers ate less fruit and vegetables than nonsmokers, leading to lower vitamin E, vitamin C, and carotene intakes, even after adjustment for age, education, and marital status. Unlike vitamin E, plasma ascorbic acid and beta-carotene concentrations were reduced in smokers compared with nonsmokers and were inversely related to cigarette consumption. This difference remained significant after adjustment for alcohol and dietary intakes. Among the measured oxidative stress indexes, only Schiff base concentration was positively related to the number of cigarettes smoked. In our sample of French men, smoking had an adverse effect on antioxidant status; vitamin intakes were reduced in smokers and plasma antioxidant indexes were altered independently of dietary intakes. As in other countries, in France smokers require particular attention in terms of public health intervention.

Low and very low density lipoprotein composition and resistance to copper-induced oxidation are not notably modified in smokers.

To study whether tobacco use was associated with oxidative phenomena affecting lipoproteins, we estimated susceptibility of LDL and VLDL to an in vitro copper-mediated oxidation, and measured serum autoantibody titers against oxidized LDL in 45 middle-age healthy nonsmokers, 35 smokers and 37 ex-smokers of both sexes, taking into account the detailed lipid composition of the lipoproteins. VLDL from female smokers had higher triglyceride, phospholipid, apolipoprotein E and alpha-tocopherol content and showed a higher rate of copper-induced oxidation in comparison with those from nonsmokers (P < or = 0.05) whereas the relative composition of these particles in saturated, mono- or poly-unsaturated fatty acids was not modified by tobacco consumption. After adjustment for triglyceride content, no statistically significant difference in oxidation rate was observed. Lipid, alpha-tocopherol and protein composition of LDL did not appear to be influenced by smoking; in accordance with these observations, no difference in indices of in vitro oxidizability of LDL was noticed between the different groups. Autoantibody titers against oxLDL were similar in smokers and nonsmokers. We conclude that, in supposed healthy individuals, smoking does not seem to be associated with notable variations in composition of VLDL and LDL or with an increase of oxidizability of these atherogenic lipoproteins.