Plasma lipid hydroperoxides measurement by an automated xylenol orange method

Protein oxidation parameters in type 2 diabetic patients with good and poor glycaemic control

AIM

In order to examine the influence of oxidative stress on protein oxidation, type 2 diabetic patients without clinical evidence of complications, either in good or poor glycaemic control, were studied.

METHODS

Plasma protein carbonyl (PCO), total thiol (T-SH), and advanced oxidation protein products (AOPP) levels as markers of protein oxidation, and lipid hydroperoxide (LHP) levels as markers of lipid peroxidation were determined. Glycated haemoglobin (HbA1c) levels were used as an index of glycaemic control. The subjects were divided into two groups according to their HbA1c level at inclusion as follows: good HbA1c<=7%, and poor HbA1c > 7%.

RESULTS

Plasma PCO and AOPP levels of diabetic patients with poor glycaemic control were increased significantly compared with those of the diabetic patients with good glycaemic control. The decreased plasma T-SH level in the diabetic patients with poor glycaemic control was not statistically significant. On the other hand, plasma LHP levels were increased significantly in the diabetic patients with poor GC compared with those of the diabetic patients with good glycaemic control.

CONCLUSION

This study supports the hypothesis that poor glycaemic control is an important factor in generation of increased protein oxidation in type 2 diabetic patients clinically free of complications. Increase in plasma PCO, AOPP, and LHP levels in the diabetic patients with poor glycaemic control may contribute to the development of diabetic complications.

Oxygen radical absorbance capacity (ORAC) and exercise-induced oxidative stress in trotters

Strenuous exercise is a potent inducer of oxidative stress, which has been suggested to be associated with disturbances in muscle homeostasis, fatigue and injury. There is no comprehensive or uniform view of the antioxidant status in horses. We have previously shown that moderate exercise induces protein oxidation in trotters. The aim of this study was to measure the antioxidative capacity of the horse in relation to different antioxidant components and oxidative stress markers after a single bout of moderate exercise to elucidate the mechanisms of antioxidant protection in horses. Eight clinically normal and regularly trained standard-bred trotters were treadmill-exercised for 53 min at moderate intensity. Blood samples were collected prior to and immediately after exercise and at 4 and 24 h of recovery. Muscle biopsies from the middle gluteal muscle were taken before exercise and after 4 h of recovery. Acute induction of oxygen radical absorbance capacity (ORAC) did not prevent exercise-induced oxidative stress, which was demonstrated by increased lipid hydroperoxides (LPO). Pre-exercise ORAC levels were, however, a determinant of total glutathione content of the blood after 4 and 24 h of recovery. Furthermore, baseline ORAC level correlated negatively with 4-h recovery LPO levels. Our results imply that horses are susceptible to oxidative stress, but a stronger antioxidant capacity may improve coping with exercise-induced oxidative stress.

Determination of pyrrolized phospholipids in oxidized phospholipid vesicles and lipoproteins

The Ehrlich reaction was optimized to determine pyrrolized phospholipids produced as a consequence of oxidative stress. The procedure consisted of the treatment of the modified phospholipids with p-(dimethylamino)benzaldehyde at a controlled acidity temperature and the spectrophotometric determination of adducts produced. The extinction coefficient of Ehrlich adducts was calculated by using 1-[1-(2-hydroxyethyl)-1H-pyrrol-2-yl]propan-1-ol (compound 1) as standard and was 56,500 M(-1)cm(-1). The response was linear and reproducible within the range of 0.051-7.65 microM of compound 1. When the assay was applied to determination of pyrrole content in ethanolamine incubated in the presence of 0.25-1mM of 4,5(E)-epoxy-2(E)-heptenal, the complete conversion of the aldehyde into the pyrrole ring was observed and the results obtained were similar to those found when compound 1 was determined by gas chromatography. When phosphatidylethanolamine was incubated in the presence of 0.5-40 mM of 4,5(E)-epoxy-2(E)-heptenal, the phospholipid was pyrrolized similarly to ethanolamine, although there was not a quantitative conversion and the amount of pyrroles produced depended on the pH of the media. Pyrrolized phospholipids were also produced when phosphatidylethanolamine multilamellar vesicles where oxidized in the presence of either Fe(3+)/ascorbic acid or ABAP (2,2'-azobis(2-methylpropionamide) dihydrochloride) and when high-density lipoproteins were incubated in the presence of Cu(2+), thereby confirming that phospholipid pyrrolization is a common consequence of oxidative stress and that Ehrlich adducts may be valid for determining this pyrrolization.

Longitudinal study of oxidative status in 312 cystic fibrosis patients in stable state and during bronchial exacerbation

In cystic fibrosis (CF), there is an imbalance in the oxidant/antioxidant system, leading to oxidative damage. The aim of this study was to assess antioxidant-scavenger deficiencies and lipid peroxide variations in three clinical situations (stable status, acute exacerbation, and after intravenous antibiotic treatment). The objective was also to correlate oxidative stress with age, nutritional status, and respiratory function. The study included prospectively 312 consecutive patients and 53 controls. Antioxidants (vitamin A, vitamin E, carotenoids, and glutathione) and oxidative markers (malondialdehyde and lipid peroxides) were measured in plasma. Regression analyses were performed. Antioxidant levels were lower in CF patients than in controls. These levels decreased during acute exacerbation and increased after antibiotic treatment. Carotenoid levels were not modified by infection or age. Only vitamin A and carotenoid levels were positively correlated to body mass index. Antioxidant levels were correlated to forced expiratory volume at 1 sec. Lipid peroxidation markers were lower in patients than in controls. Their levels decreased during infection, and increased after antibiotic treatment. Impaired lung function was correlated with elevated malondialdehyde levels. In conclusion, this study demonstrates antioxidant deficiency in a very large cohort of CF patients. Carotenoid and vitamin E deficiencies occur early in the course of the disease. Antioxidants decrease with bronchial infection. By contrast, nutritional disorders did not modify antioxidant levels during acute exacerbations. Thus, pulmonary disorders rather than nutritional disorders seem to be essential in the imbalance of the oxidant/antioxidant system. Results concerning glutathione and oxidative-marker levels highlighted the fact that their plasma values do not reflect oxidative stress in the respiratory tract.