Total Antioxidant Capacity in beta-thalassemia: A systematic review and meta-analysis of case-control studies.

Total Antioxidant Capacity (TAC), a biomarker measuring the antioxidant potential of body fluids, including redox synergistic interactions, is influenced by the presence of products of catabolism such as bilirubin (BR) and uric acid (UA). Hyperuricaemia and increased BR levels were observed in thalassemia. In order to evaluate the differences in TAC values between thalassemic patients and healthy subjects, we performed a systematic review and meta-analysis of case-control studies. After the exclusion of data deemed unsuitable for meta-analysis inclusion and a study imputed of bias by Trim-and-fill analysis, mean difference (MD) and confidence intervals 95% (CI 95%) were calculated by the random effect model for beta-thalassemia major (BTM) (1351 subjects: 770 thalassemic and 581 controls, from 15 studies) and Trait (BTT) or Hemoglobin E (BTE) (475 subjects: 165 thalassemic and 310 controls, from 5 studies). Despite the differences in clinical symptoms and severity, similar decreased levels of TAC were found in BTM [MD -0.22 (-0.35 -0.09) p<0.001] and BTT or BTE [MD -0.22 (-0.44 -0.01) p<0.05]. In conclusion, UA and BR interference on TAC suggests that corrected TAC and in particular the UA-independent TAC, considering the prominent influence of UA, might be the better approach to evaluate body antioxidant status.

Camellia sinensis in asymptomatic hyperuricemia: A meta-analysis of tea or tea extract effects on uric acid levels.

Flavanols of Camellia sinensis exhibit uric acid (UA) lowering effect, through the modulation of both xanthine oxidase and urate excretion. In order to investigate the potential benefit of Camellia Sinenis products in asymptomatic hyperuricemia, a meta-analysis of long-term Randomized Controlled Trials (RCT) with tea or tea extract has been conducted. From 20 human intervention studies selected only 5 RCT (13 interventions) were suitable for meta-analysis (n = 472). The current "normal" range set for hyperuricemia fails to identify patients with potential metabolic disorders. Therefore on the basis of the literature data, we fixed cut-off limits for UA baseline levels of 4.5 mg/dl for women, 6.1 mg/dl for men, and 5.5 mg/dl for studies involving mixed populations. Statistically significant effects were not found, but subgroup analysis revealed that the Pooled Estimate effect was different in subjects with baseline levels under [MD (95% CI): 0.1078 (-0.0528 to 0.2684)] and over the cut-off [MD (95% CI): -0.0239 (0.3311 to 0.2833)]. However, due to the low number of RCT and to the lack of data on bioavailability, it is difficult to draw any firm conclusion and more studies are needed to establish if tea flavanols could be useful in asymptomatic hyperuricemia treatment.

Relationship between the Peroxidation of Leukocytes Index Ratio and the Improvement of Postprandial Metabolic Stress by a Functional Food.

For the first time, we investigated the relationship between postprandial dysmetabolism and the Peroxidation of Leukocytes Index Ratio (PLIR), a test that measures the resistance of leukocytes to exogenous oxidative stress and their functional capacity of oxidative burst upon activation. Following a blind, placebo controlled, randomized, crossover design, ten healthy subjects ingested, in two different occasions, a high fat and high carbohydrates meal with Snello cookie (HFHCM-S) or with control cookies (HFHCM-C). Snello cookie, a functional food covered by dark chocolate and containing glucomannan, inulin, fructooligosaccharides, and Bacillus coagulans strain GanedenBC30, significantly improved postprandial metabolic stress (insulin, glucose, and triglycerides) and reduced the postprandial increase of uric acid. HFHCM-S improved PLIR of lymphocytes, but not of monocytes and granulocytes. Both meals increased granulocytes' count and reduced the lipoperoxidation induced by both exogenous free radicals and reactive oxygen species (ROS) produced by oxidative burst. Our results suggest that the healthy status of the subjects could be a limitation of this pilot study for PLIR evaluation on cells that produce ROS by oxidative burst. In conclusion, the relationship between PLIR and postprandial dysmetabolism requires further investigations.

The Peroxidation of Leukocytes Index Ratio Reveals the Prooxidant Effect of Green Tea Extract.

Despite tea increased plasma nonenzymatic antioxidant capacity, the European Food Safety Administration (EFSA) denied claims related to tea and its protection from oxidative damage. Furthermore, the Supplement Information Expert Committee (DSI EC) expressed some doubts on the safety of green tea extract (GTE). We performed a pilot study in order to evaluate the effect of a single dose of two capsules of a GTE supplement (200 mg × 2) on the peroxidation of leukocytes index ratio (PLIR) in relation to uric acid (UA) and ferric reducing antioxidant potential (FRAP), as well as the sample size to reach statistical significance. GTE induced a prooxidant effect on leukocytes, whereas FRAP did not change, in agreement with the EFSA and the DSI EC conclusions. Besides, our results confirm the primary role of UA in the antioxidant defences. The ratio based calculation of the PLIR reduced the sample size to reach statistical significance, compared to the resistance to an exogenous oxidative stress and to the functional capacity of oxidative burst. Therefore, PLIR could be a sensitive marker of redox status.

Effects of red wine on postprandial stress: potential implication in non-alcoholic fatty liver disease development.

INTRODUCTION: Red wine consumption is considered to be protective against oxidative stress. Diet strongly influences non-alcoholic fatty liver disease, which is associated with oxidative stress and is considered the hepatic manifestation of the metabolic syndrome. METHODS: We reviewed the available evidence that investigated the effects of red wine on the postprandial-induced metabolic and oxidative stress in humans. RESULTS: After red wine consumption with meal, despite the improvement in non-enzymatic antioxidant capacity and lipoperoxidation markers, the influence of confounding factors such as uric acid should be taken into account. Both uric acid and triglycerides increases, induced by ethanol, could cause liver damage. On the other hand, further researches are required in order to understand the meaning of the induction of antioxidant enzymes by red wine and red wine polyphenols in the context of non-alcoholic fatty liver disease. CONCLUSION: In conclusion, inconsistent and contrasting findings exist regarding the potential benefits of red wine consumption against postprandial stress.

The effect of sample storage on the Peroxidation of Leukocytes Index Ratio (PLIR) measure.

Delays in processing are frequent because of problems associated with transporting the samples to the laboratory. Thus, we aimed to evaluate the effect of sample storage on the Peroxidation of Leukocytes Index Ratio (PLIR). Differences between PLIR values of lymphocytes (PLIR-L), monocytes (PLIR-M) and granulocytes (PLIR-G) were observed in fresh samples. Sample storage affected the evaluation of PLIR. In particular, PLIR-L was lower in stored samples compared to fresh samples. In conclusion, our results suggest that fresh samples are recommended for assessing the PLIR.

Interference of flavonoids with fluorescent intracellular probes: methodological implications in the evaluation of the oxidative burst by flow cytometry.

The evaluation of oxidative burst is particularly relevant in many pathological and subclinical conditions. Flow cytometry provides quick and accurate measures of the reactive oxygen species production by leukocytes in most situations. However, spurious results, related to probes' efflux may be observed in several instances. Many factors affect the evaluation of the oxidative burst with fluorescent probes that require intracellular deacetylation and could be substrate of the multidrug resistance proteins (MDR). After discussing the implications of the efflux of fluorophores in the normalization strategies in flow cytometry assays, we have pointed out the possible interference of flavonoids with fluorescet probes' staining and signal. We have also reviewed the results from human intervention studies regarding the evaluation of oxidative burst with these probes. In vitro, at concentrations close to post-ingestion circulating levels, some flavonoids and their metabolites could interfere with probes' staining and fluorescence signal through different mechanisms, such as the inhibition of esterases, the modulation of the MDR-mediate efflux of probe and the inhibition of the oxidation of probe. These effects may explain the contrasting results obtained by human intervention studies. Finally, also inflammatory state or the use of drugs substrate of MDR proteins could affect the evaluation of the oxidative burst with intracellular probes.

Serum depletion, multidrug resistance and fluorescent probes: methodological implications in free radicals evaluation.

Intracellular probes used for oxidative burst evaluation could be a substrate of the multidrug resistance proteins (MDR), which may cause misinterpretation of experimental data. We aimed to study the effect of the culture condition and of the MDR-interfering antioxidant quercetin on free radical measurement in serum depleted HCT-8 cells and chick embryo hepatocytes. Serum depletion and/or quercetin affected the traffic of 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF) and calcein. The comparative results obtained with 2',7'-dichlorofluorescein (DCF) and with the plasma-membrane probe C11-BODIPY 581/591 [4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid], suggest caution in the use of intracellular probes to evaluate oxidative stress in vitro.

Effects of peroxyl radicals on contractility of rabbit aorta and guinea pig atria.

BACKGROUND: High-fat meals may lead to hypotension, oxidative stress and increases of lipopolysaccharide (LPS). Contrasting results have been reported after treatment of isolated tissues with hydrogen peroxide and LPS, whereas the effects of peroxyl radicals, involved in the propagation reaction of lipoperoxidation, have not been investigated previously. AIM: In the present study, we aimed to evaluate the effects of peroxyl radicals on the contractile responses in isolated rabbit aorta and guinea pig atria. METHODS AND RESULTS: We treated isolated guinea pig atria, rabbit aorta strips and rings with 2,2'-Azobis (2- amidinopropane) dihydrochloride (AAPH). AAPH did not affect isoprenaline-induced contraction in guinea pig atria, whilst it dose-dependently reduced the contractile responses induced in rabbit aorta strips by cumulative doses of adrenaline (ADR) and induced an endothelium-independent relaxation of noradrenaline (NA)-contracted aorta rings. The effects of KCl-induced and BaCl2-induced contractions were small. Furthermore, alkalinization with NH4Cl of NA-contracted aorta rings significantly reduced the vasodilatatory activity of AAPH. CONCLUSION: The present study suggests that peroxyl radicals induce acute functional alterations on vascular contraction through intracellular pH regulation. This finding could be related to the documented after meal increase in oxidative burst and endotoxin and the related hypotension.