Identification of (poly)phenol treatments that modulate the release of pro-inflammatory cytokines by human lymphocytes.

Diets rich in fruits and vegetables (FV), which contain (poly)phenols, protect against age-related inflammation and chronic diseases. T-lymphocytes contribute to systemic cytokine production and are modulated by FV intake. Little is known about the relative potency of different (poly)phenols in modulating cytokine release by lymphocytes. We compared thirty-one (poly)phenols and six (poly)phenol mixtures for effects on pro-inflammatory cytokine release by Jurkat T-lymphocytes. Test compounds were incubated with Jurkat cells for 48 h at 1 and 30 µm, with or without phorbol ester treatment at 24 h to induce cytokine release. Three test compounds that reduced cytokine release were further incubated with primary lymphocytes at 0·2 and 1 µm for 24 h, with lipopolysaccharide added at 5 h. Cytokine release was measured, and generation of H2O2 by test compounds was determined to assess any potential correlations with cytokine release. A number of (poly)phenols significantly altered cytokine release from Jurkat cells (P<0·05), but H2O2 generation did not correlate with cytokine release. Resveratrol, isorhamnetin, curcumin, vanillic acid and specific (poly)phenol mixtures reduced pro-inflammatory cytokine release from T-lymphocytes, and there was evidence for interaction between (poly)phenols to further modulate cytokine release. The release of interferon-γ induced protein 10 by primary lymphocytes was significantly reduced following treatment with 1 µm isorhamnetin (P<0·05). These results suggest that (poly)phenols derived from onions, turmeric, red grapes, green tea and açai berries may help reduce the release of pro-inflammatory mediators in people at risk of chronic inflammation.

Variable duration of decaffeinated green tea extract ingestion on exercise metabolism.

PURPOSE: The aim of this study was to investigate if the duration of decaffeinated green tea extract (dGTE) ingestion plays a role in augmenting fat oxidation rates during moderate-intensity exercise. METHODS: In a crossover, placebo-controlled design, 19 healthy males (mean ± SD; age = 21 ± 2 yr, weight = 75.0 ± 7.0 kg, body mass index = 23.2 ± 2.2 kg·m, maximal oxygen consumption [V˙O2max] = 55.4 ± 4.6 mL·kg·min) ingested dGTE and placebo (PLA) for 28 d, separated by a 28-d washout period. On the first day (dGTE 1 or PLA 1) and after 7 d (dGTE 7 or PLA 7) and 28 d (dGTE 28 or PLA 28), participants completed a 30-min cycle exercise bout (50% Wmax), 2 h after ingestion. Indirect calorimetry was used to calculate rates of whole-body fat and carbohydrate oxidation during exercise. Blood samples were collected at rest and during exercise for analysis of plasma fatty acids, glycerol, and epigallocatechin gallate. RESULTS: The ingestion of dGTE did not significantly change whole-body fat oxidation rates during exercise on day 1, 7, or 28 compared with PLA. There were also no changes in plasma concentrations of fatty acids and glycerol at rest and during exercise as a result of dGTE ingestion at any time point compared with PLA. Plasma epigallocatechin gallate concentrations, immediately before the exercise bout, in the three dGTE trials were elevated compared with PLA but not different between 1, 7, and 28 d. CONCLUSION: In contrast to previous reports, we found that the duration of dGTE ingestion had no effect on whole-body fat oxidation rates or fat metabolism-related blood metabolites during exercise in physically active healthy males.

No effect of 1 or 7 d of green tea extract ingestion on fat oxidation during exercise.

PURPOSE: The aim of this study was to investigate the effects of 1 and 7 d of green tea extract (GTE) ingestion on whole body fat oxidation during moderate-intensity exercise. METHODS: Thirty-one men completed two exercise trials (60-min cycle, 50% Wmax). After the baseline trial (day 0), subjects were randomly assigned to one of three conditions involving a week supplementation of the following: 1) 7 d of placebo, 2) 6 d of placebo followed by 1 d of GTE (GTE1), and 3) 7 d of GTE ingestion (GTE7). The morning after the supplementation week, subjects consumed an additional supplement and completed a second exercise trial (day 8). V˙O2 and V˙CO2 measurements were taken during exercise to calculate whole body fat oxidation rates. Blood samples, for analysis of plasma fatty acids (FA), glycerol, and epigallocatechin gallate, were collected at rest and during exercise. RESULTS: On day 8, the plasma kinetics and maximal plasma concentrations of epigallocatechin gallate were similar in the GTE1 and GTE7 group (206 ± 28 and 216 ± 25 ng·mL, respectively). One day of GTE ingestion did not affect markers of lipolysis during the exercise bout. Seven days of GTE ingestion significantly increased plasma glycerol during exercise (P = 0.045) and plasma FA during exercise (P = 0.020) as well as at rest (P = 0.046). However, fat oxidation did not change in any of the groups. CONCLUSIONS: There was no effect of 1 d of GTE ingestion on markers of lipolysis or fat oxidation during exercise. Seven days of GTE ingestion increased lipolysis, indicated by increased plasma FA and glycerol concentrations, but did not result in significant changes in fat oxidation.

Metabolic conversion of dietary flavonoids alters their anti-inflammatory and antioxidant properties.

The notion that dietary flavonoids exert beneficial health effects in humans is often based on in vitro studies using the glycoside or aglycone forms of these flavonoids. However, flavonoids are extensively metabolized in humans, resulting in the formation of glucuronide, methyl, and sulfate derivatives, which may have different properties than their parent compounds. The goal of this study was to investigate whether different chemical modifications of the same flavonoid molecule affect its biological and antioxidant activities. Hence, we studied the anti-inflammatory effects of several major human metabolites of quercetin and (-)-epigallocatechin-3-O-gallate (EGCG) by assessing their inhibitory effects on tumor necrosis factor α (TNFα)-induced protein expression of cellular adhesion molecules in human aortic endothelial cells (HAEC). HAEC were incubated with 1-30 µM quercetin, 3'- or 4'-O-methyl-quercetin, quercetin-3-O-glucuronide, and quercetin-3'-O-sulfate or 20-100 µM EGCG, 4''-O-methyl-EGCG, and 4',4''-di-O-methyl-EGCG, prior to coincubation with 100 U/ml of TNFα. 3'-O-Methyl-quercetin, 4'-O-methyl-quercetin, and their parent aglycone compound, quercetin, all effectively inhibited expression of intercellular adhesion molecule-1 (ICAM-1) with IC(50) values (concentration required for 50% inhibition) of 8.0, 5.0, and 4.4 µM, respectively; E-selectin expression was suppressed to a somewhat lesser but still significant degree by all three compounds, whereas vascular cell adhesion molecule-1 (VCAM-1) was not affected. In contrast, quercetin-3-O-glucuronide (20-100 µM), quercetin-3'-O-sulfate (10-30 µM), and phenolic acid metabolites of quercetin (20-100 µM) did not inhibit adhesion molecule expression. 4',4''-Di-O-methyl-EGCG selectively inhibited ICAM-1 expression with an IC(50) value of 94 µM, whereas EGCG (20-60 µM) and 4''-O-methyl-EGCG (20-100 µM) had no effect. The inhibitory effects of 3'-O-methyl-quercetin and 4',4''-di-O-methyl-EGCG on adhesion molecule expression were not related either to inhibition of NF-κB activation or to their antioxidant reducing capacity. Our data indicate that flavonoid metabolites have different biological and antioxidant properties than their parent compounds, and suggest that data from in vitro studies using nonmetabolites of flavonoids are of limited relevance in vivo.

Consumption of flavonoid-rich foods and increased plasma antioxidant capacity in humans: cause, consequence, or epiphenomenon?

Increased fruit and vegetable consumption is associated with a decreased incidence of cardiovascular diseases, cancer, and other chronic diseases. The beneficial health effects of fruits and vegetables have been attributed, in part, to antioxidant flavonoids present in these foods. Large, transient increases in the total antioxidant capacity of plasma have often been observed after the consumption of flavonoid-rich foods by humans. These observations led to the hypothesis that dietary flavonoids play a significant role as antioxidants in vivo, thereby reducing chronic disease risk. This notion, however, has been challenged recently by studies on the bioavailability of flavonoids, which indicate that they reach only very low concentrations in human plasma after the consumption of flavonoid-rich foods. In addition, most flavonoids are extensively metabolized in vivo, which can affect their antioxidant capacity. Furthermore, fruits and vegetables contain many macro- and micronutrients, in addition to flavonoids, that may directly or through their metabolism affect the total antioxidant capacity of plasma. In this article, we critically review the published research in this field with the goal to assess the contribution of dietary flavonoids to the total antioxidant capacity of plasma in humans. We conclude that the large increase in plasma total antioxidant capacity observed after the consumption of flavonoid-rich foods is not caused by the flavonoids themselves, but is likely the consequence of increased uric acid levels.

Dietary flavonoids attenuate tumor necrosis factor alpha-induced adhesion molecule expression in human aortic endothelial cells. Structure-function relationships and activity after first pass metabolism.

Flavonoids have been suggested to exert human health benefits by anti-oxidant and anti-inflammatory mechanisms. In this study, we investigated whether and by what mechanisms dietary flavonoids inhibit expression of cellular adhesion molecules, which is relevant to inflammation and atherosclerosis. We found that the capacity of flavonoids to inhibit tumor necrosis factor alpha-induced adhesion molecule expression in human aortic endothelial cells was dependent on specific structural features of the flavonoids. The 5,7-dihydroxyl substitution of a flavonoid A-ring and 2,3-double bond and 4-keto group of the C-ring were the main structural requirements for inhibition of adhesion molecule expression. In striking contrast, hydroxyl substitutions of the B- and C-rings but not the A-ring were essential for antioxidant activity. Hence, only hydroxyl flavones, such as apigenin and chrysin, and flavonols, such as galangin, kaempferol, and quercetin, were able to inhibit endothelial adhesion molecule expression, whereas flavone, chromone, the flavanone, naringenin, and the flavanol, (-)-epicatechin, were ineffectual. At low concentrations, the active flavonoids significantly attenuated expression of E-selectin and intercellular adhesion molecule 1 but not vascular cell adhesion molecule 1. In addition, exposure of apigenin and kaempferol to cultured hepatocytes, mimicking first pass metabolism, greatly diminished the inhibitory effect of flavonoids on endothelial intercellular adhesion molecule 1 expression. We conclude that the effect of dietary flavonoids on endothelial adhesion molecule expression depends on their molecular structure, concentration, and metabolic transformation but not their antioxidant activity.

Regular consumption of a flavanol-rich chocolate can improve oxidant stress in young soccer players.

The consumption of a diet rich in certain flavonoids, including the flavanol sub-class, has been associated with a reduced risk for vascular disease. We evaluated the effects of the regular consumption (14 d) of a flavanol-containing milk chocolate (FCMC) or cocoa butter chocolate (CBC) on variables related to vascular disease risk, oxidative stress and physical activity. Twenty-eight free-living, young (18-20 years old) male soccer players consumed daily 105 g of FCMC (168 mg of flavanols) or CBC (< 5 mg of flavanols), as part of their normal diet. The consumption of FCMC was significantly associated with a decrease in diastolic blood pressure (- 5 mm Hg), mean blood pressure (- 5 mm Hg), plasma cholesterol (-11%), LDL-cholesterol (-15%), malondialdehyde (- 12%), urate (- 11%) and lactate dehydrogenase (LDH) activity (- 11%), and an increase in vitamin E/cholesterol (+ 12%). No relevant changes in these variables were associated with CBC consumption. No changes in the plasma levels of (-)-epicatechin were observed following analysis of fasting blood samples. In conclusion, FCMC consumption was associated with changes in several variables often associated with cardiovascular health and oxidant stress. The presence of significant quantities of flavanols in FCMC is likely to have been one of the contributing factors to these results.

The increase in human plasma antioxidant capacity after apple consumption is due to the metabolic effect of fructose on urate, not apple-derived antioxidant flavonoids.

Regular fruit consumption lowers the risk of cardiovascular diseases and certain cancers, which has been attributed in part to fruit-derived antioxidant flavonoids. However, flavonoids are poorly absorbed by humans, and the increase in plasma antioxidant capacity observed after consumption of flavonoid-rich foods often greatly exceeds the increase in plasma flavonoids. In the present study, six healthy subjects consumed five Red Delicious apples (1037 +/- 38 g), plain bagels (263.1 +/- 0.9 g) and water matching the carbohydrate content and mass of the apples, and fructose (63.9 +/- 2.9 g) in water matching the fructose content and mass of the apples. The antioxidant capacity of plasma was measured before and up to 6 h after food consumption as ferric reducing antioxidant potential (FRAP), without or with ascorbate oxidase treatment (FRAPAO) to estimate the contribution of ascorbate. Baseline plasma FRAP and FRAPAO were 445 +/- 35 and 363 +/- 35 microM trolox equivalents, respectively. Apple consumption caused an acute, transient increase in both plasma FRAP and FRAPAO, with increases after 1 h of 54.6 +/- 8.7 and 61.3 = 17.2 microM trolox equivalents, respectively. This increase in plasma antioxidant capacity was paralleled by a large increase in plasma urate, a metabolic antioxidant, from 271 +/- 39 microM at baseline to 367 +/- 43 microM after 1 h. In contrast, FRAP and FRAPAO time-dependently decreased after bagel consumption, together with urate. Consumption of fructose mimicked the effects of apples with respect to increased FRAP, FRAPAO, and urate, but not ascorbate. Taken together, our data show that the increase in plasma antioxidant capacity in humans after apple consumption is due mainly to the well-known metabolic effect of fructose on urate, not apple-derived antioxidant flavonoids.

Relevance of apple polyphenols as antioxidants in human plasma: contrasting in vitro and in vivo effects.

Apples are a major source of flavonoids in the Western diet, and flavonoid-rich foods may help protect against chronic diseases by antioxidant mechanisms. In the present study we investigated: (1) the antioxidant capacity of representative apple polyphenols and their contribution to the total antioxidant capacity of apple extracts; (2) the effects of adding apple extract to human plasma in vitro on oxidation of endogenous antioxidants and lipids; and (3) the effects of apple consumption by humans on ex vivo oxidation of plasma antioxidants and lipids. We found that the apple-contained flavonols and flavanols, quercetin, rutin, (-)-epicatechin, and (+)-catechin, had a higher antioxidant capacity than the dihydrochalcones, phloridzin and phloretin, and the hydroxycinnamate, chlorogenic acid. However, together these apple polyphenols contributed less than 20% to the total antioxidant capacity of aqueous apple extracts. When human plasma was exposed to a constant flux of aqueous peroxyl radicals, endogenous ascorbate (70.0 +/- 10.3 microM) was oxidized within 45 min of incubation, while endogenous urate (375 +/- 40 microM) and alpha-tocopherol (24.7 +/- 1.2 microM) were oxidized after ascorbate. Addition of 7.1 or 14.3 micrograms/ml total phenols of apple extract did not protect ascorbate from oxidation, but increased the half-life (t1/2) of urate from 136 +/- 15 to 192 +/- 16 and 208 +/- 23 min, respectively (p < 0.05 each), and t1/2 of alpha-tocopherol from 141 +/- 18 to 164 +/- 8 min (p = ns) and 188 +/- 8 min (p < 0.05). Lipid peroxidation started after ascorbate depletion, and addition of apple extract increased the lag time preceding detectable lipid peroxidation from 36.3 +/- 3.7 to 50.9 +/- 2.7 min (p < 0.05) and 70.4 +/- 4.2 min (p < 0.001). However, when six healthy volunteers ate five apples and plasma was obtained up to 4 h after apple consumption, no significant increases in the resistance to oxidation of endogenous urate, alpha-tocopherol, and lipids were found. Thus, despite the high antioxidant capacity of individual apple polyphenols and apple extracts and the significant antioxidant effects of apple extract added to human plasma in vitro, ingestion of large amounts of apples by humans does not appear to result in equivalent in vivo antioxidant effects of apple polyphenols.

Assessing the antioxidant capacity in the hydrophilic and lipophilic domains: study of a sample of Argentine wines.

The antioxidant capacity of different types of red and white wines was assessed by different assays. Two assays were used to evaluate the antioxidant capacity in aqueous phase: (1) inhibition of the generation of 2,2'-azinodi(3-etilbencenotiazolin-6-sulfonate) (ABTS)-derived radical; and (2) protection of vitamin E in human plasma. The results indicated that red wines were not all equally effective, and a comparison could be made among different types. The ABTS assay showed that Cabernet Sauvignon wines had the highest antioxidant capacity followed by Malbec wines. Red wines showed a protective capacity of 70-90% in preventing SH-groups oxidation, and, in addition, they were also effective in preventing the oxidative damage in lipid domains (30-97% protection to liposomes, 20-70% to vitamin E). The antioxidant capacity of the white wines was significantly lower, as evaluated by all the assays. Significant correlations were found for phenolics and catechin content with the antioxidant capacity of the studied wines.