OXIDATIVE CHANGES OF LIPIDS, PROTEINS AND ANTIOXIDANTS IN YOGURT DURING THE SHELF LIFE

Background: Oxidation processes in milk and yogurt during the shelf life can result in an alteration of protein and lipid constituents. Therefore, the antioxidant properties of yogurt in standard conditions of preservation were evaluated. Results: Total phenols, free radical scavenger activity, degree of lipid peroxidation and protein oxidation were determined in plain and skim yogurts with or without fruit puree. After production, plain, skim, plain berries and skim berries yogurts were compared during the shelf life up to 9 weeks. All types of yogurts revealed a basal antioxidant activity that was higher when a fruit puree was present but gradually decreased during the shelf life. However, after five-eight weeks, antioxidant activity increased again. Both in plain and berries yogurts lipid peroxidation increased until the seventh week of shelf life and after decreased, while protein oxidation of all yogurts was similar either in the absence or presence of berries and increased during shelf life. Conclusion: During the shelf life, a different behavior between lipid and protein oxidation takes place and the presence of berries determines a protection only against lipid peroxidation

Mitochondrial Thioredoxin System as a Modulator of Cyclophilin D Redox State

The mitochondrial thioredoxin system (NADPH, thioredoxin reductase, thioredoxin) is a major redox regulator. Here we have investigated the redox correlation between this system and the mitochondrial enzyme cyclophilin D. The peptidyl prolyl cis-trans isomerase activity of cyclophilin D was stimulated by the thioredoxin system, while it was decreased by cyclosporin A and the thioredoxin reductase inhibitor auranofin. The redox state of cyclophilin D, thioredoxin 1 and 2 and peroxiredoxin 3 was measured in isolated rat heart mitochondria and in tumor cell lines (CEM-R and HeLa) by redox Western blot analysis upon inhibition of thioredoxin reductase with auranofin, arsenic trioxide, 1-chloro-2,4-dinitrobenzene or after treatment with hydrogen peroxide. A concomitant oxidation of thioredoxin, peroxiredoxin and cyclophilin D was observed, suggesting a redox communication between the thioredoxin system and cyclophilin. This correlation was further confirmed by i) co-immunoprecipitation assay of cyclophilin D with thioredoxin 2 and peroxiredoxin 3, ii) molecular modeling and iii) depleting thioredoxin reductase by siRNA. We conclude that the mitochondrial thioredoxin system controls the redox state of cyclophilin D which, in turn, may act as a regulator of several processes including ROS production and pro-apoptotic factors release

Enzymatic assay of serum phosphohexose isomerase in prostatic hypertrophy and cancer

The authors have reinvestigated the phosphohexose isomerase (PHI) serum activity in 60 patients with prostatic hypertrophy and cancer with the enzymatic procedure of Noltman, more accurate and sensitive than the colorimetric method used by Bodansky and other authors. The PHI activity varied from 20 mU to 30 mU in normal subjects, while in patients with prostatic hypertrophy it varied from 60 mU to 80 mU. In prostatic carcinoma it was constantly above 110 mU. In normal subjects and in prostatic cancer, the enzymatic assay values were lower than those reported by Bodansky. In all cases the diagnosis was confirmed by bioptic inspection. An important fact was that extremely high values (not included in the mean) have been found in some patients with widely diffused metastasis. Considering also the few intermediate values which cannot be easily included in the reported groups (between 30 and 50 mU in 1 normal subject, and 2 prostatic hypertrophies; between 70 and 90 mU in 2 prostatic hypertrophies and 3 cancers), the present investigation shows that the enzymatic assay of PHI may be clinically very interesting. It provides selective values for the diagnosis not only between prostatic hypertrophy and cancer but also in cases of hypertrophy with single suspected nests, and, above all, in cancer metastatized. The method is much more worthy, about 90%, than those of serum phosphatases, which reach, by Cavazzana, 75% at least