Consumption of green tea favorably affects oxidative stress markers in weight-trained men

The effects of green tea extract supplementation on body composition, obesity-related hormones and oxidative stress markers: a grade-assessed systematic review and dose-response meta-analysis of randomised controlled trials

Research indicates that green tea extract (GTE) supplementation is beneficial for a range of conditions, including several forms of cancer, CVD and liver diseases; nevertheless, the existing evidence addressing its effects on body composition, oxidative stress and obesity-related hormones is inconclusive. This systematic review and meta-analysis aimed to investigate the effects of GTE supplementation on body composition (body mass (BM), body fat percentage (BFP), fat mass (FM), BMI, waist circumference (WC)), obesity-related hormones (leptin, adiponectin and ghrelin) and oxidative stress (malondialdehyde (MDA) and total antioxidant capacity (TAC)) markers. We searched proper databases, including PubMed/Medline, Scopus and Web of Science, up to July 2022 to recognise published randomised controlled trials (RCT) that investigated the effects of GTE supplementation on the markers mentioned above. A random effects model was used to carry out a meta-analysis. The heterogeneity among the studies was assessed using the I2 index. Among the initial 11 286 studies identified from an electronic database search, fifty-nine studies involving 3802 participants were eligible to be included in this meta-analysis. Pooled effect sizes indicated that BM, BFP, BMI and MDA significantly reduced following GTE supplementation. In addition, GTE supplementation increased adiponectin and TAC, with no effects on FM, leptin and ghrelin. Certainty of evidence across outcomes ranged from low to high. Our results suggest that GTE supplementation can attenuate oxidative stress, BM, BMI and BFP, which are thought to negatively affect human health. Moreover, GTE as a nutraceutical dietary supplement can increase TAC and adiponectin.

Polyphenol Supplementation and Antioxidant Status in Athletes: A Narrative Review

Antioxidants in sports exercise training remain a debated research topic. Plant-derived polyphenol supplements are frequently used by athletes to reduce the negative effects of exercise-induced oxidative stress, accelerate the recovery of muscular function, and enhance performance. These processes can be efficiently modulated by antioxidant supplementation. The existing literature has failed to provide unequivocal evidence that dietary polyphenols should be promoted specifically among athletes. This narrative review summarizes the current knowledge regarding polyphenols' bioavailability, their role in exercise-induced oxidative stress, antioxidant status, and supplementation strategies in athletes. Overall, we draw attention to the paucity of available evidence suggesting that most antioxidant substances are beneficial to athletes. Additional research is necessary to reveal more fully their impact on exercise-induced oxidative stress and athletes' antioxidant status, as well as optimal dosing methods.

Effects of Functional Phenolics Dietary Supplementation on Athletes' Performance and Recovery: A Review

In recent years, many efforts have been made to identify micronutrients or nutritional strategies capable of preventing, or at least, attenuating, exercise-induced muscle damage and oxidative stress, and improving athlete performance. The reason is that most exercises induce various changes in mitochondria and cellular cytosol that lead to the generation of reactive species and free radicals whose accumulation can be harmful to human health. Among them, supplementation with phenolic compounds seems to be a promising approach since their chemical structure, composed of catechol, pyrogallol, and methoxy groups, gives them remarkable health-promoting properties, such as the ability to suppress inflammatory processes, counteract oxidative damage, boost the immune system, and thus, reduce muscle soreness and accelerate recovery. Phenolic compounds have also already been shown to be effective in improving temporal performance and reducing psychological stress and fatigue. Therefore, the aim of this review is to summarize and discuss the current knowledge on the effects of dietary phenolics on physical performance and recovery in athletes and sports practitioners. Overall, the reports show that phenolics exert important benefits on exercise-induced muscle damage as well as play a biological/physiological role in improving physical performance.

An Overview on How Exercise with Green Tea Consumption Can Prevent the Production of Reactive Oxygen Species and Improve Sports Performance

Free radicals are reactive products that have multiple effects on the human body. Endogenous and exogenous antioxidants manage the overproduction of free radicals. However, an imbalance between free radicals and antioxidant factors causes oxidative stress. Exercise and physical activity are factors that increase oxidative stress and disrupts the body’s homeostasis. Intensity and duration of training, training characteristics, and fitness level can have positive or negative effects on oxidative stress. Green tea consumption is recommended for the prevention of a variety of diseases, health maintenance, and weight loss. The effectiveness of green tea is primarily due to the presence of catechins and polyphenols, specifically (–)-epigallocatechin-3-gallate, which has antioxidant and anti-inflammatory properties based on clinical and animal studies. This review investigates the effect of green tea exercise and their interactive effects on free radicals and sports improvement.

Effect of Green Tea Supplementation on Antioxidant Status in Adults: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

It is well-established that green tea supplementation has antioxidant properties. However, whether green tea supplementation leads to oxidative stress reduction remains unclear, as clinical investigations on this subject have yielded inconsistent outcomes. Consequently, we aimed to determine the effects of green tea supplementation on oxidative stress in adults. A systematic search of English language publications up to 21 August 2021 was carried out in PubMed, Scopus, Embase, and ISI Web of Science, utilizing pertinent keywords. These searches included randomized controlled trials (RCTs) evaluating the relationship between green tea supplementation, malondialdehyde (MDA), and total antioxidant capacity (TAC) in adults. A random-effects model was used to estimate the weighted mean difference (WMD) and 95% confidence intervals (95% CI). Meta-regression and non-linear dose-response analyses were performed to investigate the association between the dosage of green tea (mg/day) and the duration of the intervention (weeks) with pooled effect size. Sixteen RCTs with seventeen arms including 760 participants met the inclusion criteria. Our results indicated that green tea supplementation had significant effects on TAC (weighted mean difference [WMD]: 0.20 mmol/L; 95% CI: 0.09, 0.30, p < 0.001) and significant heterogeneity between studies (I² = 98.6%, p < 0.001), which was largely related to gender and body mass index (BMI). Subgroup analysis in TAC identified a significant relationship except with low dose supplementation and obese individuals. No relationship between MDA and green tea supplementation was observed in any subgroups; however, meta-regression analysis revealed a linear inverse association between the dosage and significant change in MDA (r = −2117.18, p = 0.017). Our outcomes suggest that green tea supplementation improves TAC and affects MDA based on the dose of the intervention in adults. Future RCTs with longer durations are needed to expand our findings.

The Combined Effects of 6 Weeks of Jump Rope Interval Exercise and Dark Chocolate Consumption on Antioxidant Markers in Obese Adolescent Boys

Research has shown that both dark chocolate and exercise training may have favorable effects on antioxidant function in obese cohorts. However, their combined effect has not been established. We assessed the influences of six weeks of dark chocolate consumption combined with jump rope exercise on antioxidant markers in adolescent boys with obesity. Fifty adolescent boys with obesity (age = 15 ± 1 years) were randomly assigned into one of four groups; jump rope exercise + white chocolate consumption (JW; n = 13), jump rope exercise + dark chocolate consumption (JD; n = 13), dark chocolate consumption (DC; n = 12), or control (C; n = 12). Two participants dropped out of the study. Participants in JW and JD groups performed jump rope exercise three times per week for six weeks. Participants in the DC and JD groups consumed 30 g of dark chocolate containing 83% of cocoa during the same period. Serum concentrations of superoxide dismutase (SOD), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and thiobarbituric acid reactive substances (TBARS) were evaluated prior to and after the interventions. All 3 intervention groups noted significant (p < 0.01) increases in serum concentrations of TAC, SOD, and GPx from baseline to post-test. In contrast, all intervention groups showed significantly reduced serum concentrations of TBARS from pre- to post-test (p ≤ 0.01). Bonferroni post hoc analysis revealed that post-test serum concentrations of TAC in the JD group were significantly greater than C (p < 0.001), DC (p = 0.010), and JW (p < 0.001) groups. In addition, post-test serum concentrations of SOD in the JD group were significantly greater than C group (p = 0.001). Post-test serum concentrations of GPx in the JD group were significantly greater than C (p < 0.001), DC (p = 0.021), and JW (p = 0.032) groups. The post-test serum concentrations of TBARS in the JD group was significantly lower than C (p < 0.001). No other significant between-group differences were observed. The current study provides evidence that dark chocolate consumption in combination with jump rope exercise is more efficient in improving antioxidant capacity than dark chocolate consumption or jump rope exercise alone among obese adolescent boys.

Regular, but not acute, green tea supplementation increases total antioxidant status and reduces exercise-induced oxidative stress: a systematic review

This systematic review aims to investigate the effects of green tea supplementation on exercise-induced oxidative stress. Four electronic databases were searched from inception to December 2020: SPORTDiscuss, PubMed, Scopus, and Web of Science. The search strategy was established in the following manner: (green tea) (Title/Abstract) AND (exercise OR training) (Title/Abstract) AND (oxidative stress OR antioxidant OR oxidation) (Title). After the application of inclusion and exclusion criteria 11, randomized or non-randomized control trials were included, 6 with a parallel design and 5 with a crossover design. Study methodological quality was assessed with the PEDro scale, and all studies were considered of moderate quality. Overall, acute green tea ingestion does not appear to influence antioxidant status or reduce exercise-induced oxidative stress. In contrast, green tea supplementation before exercise, for periods of more than 1 week, in a dose range of 400 to 800 mg of catechins per day, appears to be efficacious to increase total antioxidant status and protect cells against exercise-induced oxidative stress. Future investigations should focus on beginning green tea supplementation more than 7 days before exercise and completing it 2 or 3 days after while monitoring the change of markers of oxidative stress up to 48-72 h after exercise.

Galangin and Kaempferol Alleviate the Indomethacin-Caused Cytotoxicity and Barrier Loss in Rat Intestinal Epithelial (IEC-6) Cells Via Mediating JNK/Src Activation

Nonsteroidal anti-inflammatory drugs (NSAIDs) like indomethacin and others are widely used in clinics, but they have the potential to cause severe gastrointestinal damage including intestinal barrier dysfunction. Thus, two flavonols galangin and kaempferol with or without heat treatment (100 °C, 30 min) were assessed for their effect on indomethacin-damaged rat intestine epithelial (IEC-6) cells. In total, the cell exposure of 300 μmol/L indomethacin for 24 h caused cell toxicity efficiently, resulting in decreased cell viability, enhanced lactate dehydrogenase (LDH) release or reactive oxygen species (ROS) production, and obvious barrier loss. Meanwhile, pretreatment of the cells with these flavonols for 24 and 48 h before the indomethacin exposure could alleviate cytotoxicity and especially barrier loss, resulting in increased cell viability and transepithelial resistance, decreased LDH release, ROS production, and paracellular permeability, together with the promoted expression of three tight junction proteins zonula occluden-1, occludin, and claudin-1. Moreover, the intracellular Ca2+ concentration and expression levels of p-JNK and p-Src arisen from the indomethacin damage were also reduced by the flavonols, suggesting an inhibited calcium-mediated JNK/Src activation. Consistently, galangin showed higher activity than kaempferol to the cells, while the heated flavonols were less efficient than the unheated counterparts. It is thus highlighted that the two flavonols could alleviate indomethacin cytotoxicity and combat against the indomethacin-induced barrier loss in IEC-6 cells, but heat treatment of the flavonols would weaken the two beneficial functions.

Effects of Dietary Strategies on Exercise-Induced Oxidative Stress: A Narrative Review of Human Studies

Exhaustive exercise can induce excessive generation of reactive oxygen species (ROS), which may enhance oxidative stress levels. Although physiological levels are crucial for optimal cell signaling and exercise adaptations, higher concentrations have been demonstrated to damage macromolecules and thus facilitate detrimental effects. Besides single dosages of antioxidants, whole diets rich in antioxidants are gaining more attention due to their practicality and multicomponent ingredients. The purpose of this narrative review is to summarize the current state of research on this topic and present recent advances regarding the antioxidant effects of whole dietary strategies on exercise-induced oxidative stress in humans. The following electronic databases were searched from inception to February 2021: PubMed, Scope and Web of Science. Twenty-eight studies were included in this narrative review and demonstrated the scavenging effects of exercise-induced ROS generation, oxidative stress markers, inflammatory markers and antioxidant capacity, with only one study not confirming such positive effects. Although the literature is still scarce about the effects of whole dietary strategies on exercise-induced oxidative stress, the majority of the studies demonstrated favorable effects. Nevertheless, the protocols are still very heterogeneous and further systematically designed studies are needed to strengthen the evidence.

Acute effect of green tea catechins on uric acid metabolism after alcohol ingestion in Japanese men

INTRODUCTION/OBJECTIVES

Alcohol consumption is associated with hyperuricemia and gout. Previous studies have indicated a role for green tea catechins in uric acid (UA) metabolism. This study aimed to elucidate the acute effect of green tea catechins in terms of enhancing urinary excretion of UA and xanthine/hypoxanthine (Xa/HX; UA precursors) after alcohol ingestion.

METHODS

In a randomized crossover study, ten healthy Japanese subjects consumed test meals, including a Japanese distilled spirit (Shōchū) with water (SW) or Shōchū with catechin-rich green tea (SC), each containing 20 g of alcohol. The SC contained 617 mg of catechin in total. Serum and urine UA and Xa/HX concentrations were measured. Blood samples were collected after 2.5 h, and urine samples were collected between 0 and 5 h after consuming the test meal.

RESULTS

Urine UA and Xa/HX excretions were significantly higher in the SC group than in the SW group (UA: SW, 0.45 ± 0.08; SC, 0.52 ± 0.09; Xa/HX: SW, 0.08 ± 0.04; SC, 0.16 ± 0.05 mg/kg/h). UA clearance (C_UA) and fractional UA excretion (FE_UA) tended to increase more in the SC group than in the SW group (C_UA: SW, 7.76 ± 2.14; SC, 8.75 ± 2.23 mL/min/1.73 m²; FE_UA: SW, 6.08 ± 1.36; SC, 6.64 ± 1.42%). No significant differences in serum UA and Xa/HX concentrations were observed between two groups.

CONCLUSIONS

It was concluded that green tea catechins can enhance the excretion of UA and Xa/HX, even though alcohol is ingested.

TRIAL REGISTRATION NUMBER

UMIN000040076. Retrospectively registered 7 April 2020. https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000045687 Key Points • Green tea catechins enhance the excretion of uric acid and xanthine/hypoxanthine, even when alcohol is ingested simultaneously. • In case of non-adherence of limiting alcohol intake, catechin-rich green tea may be an effective dietary component to continue dietary therapy.

Exercise-induced muscle damage: mechanism, assessment and nutritional factors to accelerate recovery

There have been a multitude of reviews written on exercise-induced muscle damage (EIMD) and recovery. EIMD is a complex area of study as there are a host of factors such as sex, age, nutrition, fitness level, genetics and familiarity with exercise task, which influence the magnitude of performance decrement and the time course of recovery following EIMD. In addition, many reviews on recovery from exercise have ranged from the impact of nutritional strategies and recovery modalities, to complex mechanistic examination of various immune and endocrine signaling molecules. No one review can adequately address this broad array of study. Thus, in this present review, we aim to examine EIMD emanating from both endurance exercise and resistance exercise training in recreational and competitive athletes and shed light on nutritional strategies that can enhance and accelerate recovery following EIMD. In addition, the evaluation of EIMD and recovery from exercise is often complicated and conclusions often depend of the specific mode of assessment. As such, the focus of this review is also directed at the available techniques used to assess EIMD.

Effects of Short-Term Green Tea Extract Supplementation on VO2 Max and Inflammatory and Antioxidant Responses of Healthy Young Men in a Hot Environment

Background:

Nowadays, the use of green tea supplements has increased. Studies have shown that green tea can have positive effects on anti-inflammatory and antioxidative factors, as well as improve aerobic performance capacity. Therefore, in this study, we investigate the effects of this supplement on inflammatory factors, total antioxidant capacity responses, and maximum oxygen uptake (VO₂ Max) of healthy young men in summer.

Methods:

This study is a double-blind randomized controlled trial (RCT) in which 15 young men (age 25.06 ± 2.1) were randomly assigned into the green tea (GT) and placebo groups. Subjects performed maximum aerobic exercises (shuttle run 20 m) in separate workouts (14 days) in summer. They consumed 640 mg green tea extracts or maltodextrin 90 min before exercise in a double-blind design. Blood samples were collected before and after the exercise and then evaluated in the biochemistry laboratory. In this study, one way analysis of variance (ANOVA) tests were used for the statistical analysis.

Results:

The results of this study show that green tea supplement significantly slowed down the increasing tumor necrosis factor alpha (TNF-α) (GT: 15.03 ± 4.31 [pg/ml], placebo: 31.38 ± 7.18 [pg/ml], [P = 0.000]); increased the total antioxidant capacity (GT: 1.04 ± 0.06 [mm], placebo group: 0.72 ± 0.04 [mm], [P = 0.001 VO₂]); and Max (GT: 44.43 ± 3.06 [ml/kg/min], placebo group: 34.88 ± 1.30 [ml/kg/min], [P = 0.001]) in the supplement group than placebo. In addition, no significant differences in interleukin 1 beta (IL-1β) was observed between thee groups (GT: 26.86 ± 5.05 [pg/ml], placebo group: 23.47 ± 3.16 [pg/ml], [P = 0.251]).

Conclusions:

The consumption of green tea supplements 90 min before aerobic exercise may decrease inflammation and oxidative stress factors and improve VO₂ Max in summer.

Impacts of Green Tea on Joint and Skeletal Muscle Health: Prospects of Translational Nutrition

Osteoarthritis and sarcopenia are two major joint and skeletal muscle diseases prevalent during aging. Osteoarthritis is a multifactorial progressive degenerative and inflammatory disorder of articular cartilage. Cartilage protection and pain management are the two most important strategies in the management of osteoarthritis. Sarcopenia, a condition of loss of muscle mass and strength, is associated with impaired neuromuscular innervation, the transition of skeletal muscle fiber type, and reduced muscle regenerative capacity. Management of sarcopenia requires addressing both skeletal muscle quantity and quality. Emerging evidence suggests that green tea catechins play an important role in maintaining healthy joints and skeletal muscle. This review covers (i) the prevalence and etiology of osteoarthritis and sarcopenia, such as excessive inflammation and oxidative stress, mitochondrial dysfunction, and reduced autophagy; (ii) the effects of green tea catechins on joint health by downregulating inflammatory signaling mediators, upregulating anabolic mediators, and modulating miRNAs expression, resulting in reduced chondrocyte death, collagen degradation, and cartilage protection; (iii) the effects of green tea catechins on skeletal muscle health via maintaining a dynamic balance between protein synthesis and degradation and boosting the synthesis of mitochondrial energy metabolism, resulting in favorable muscle homeostasis and mitigation of muscle atrophy with aging; and (iv) the current study limitations and future research directions.

Effects of resistance training and turmeric supplementation on reactive species marker stress in diabetic rats

Background

Type 1 diabetes mellitus (T1DM) is a metabolic disease characterized by hyperglycemia and excessive generation of reactive oxygen species caused by autoimmune destruction of beta-cells in the pancreas. Among the antioxidant compounds, Curcuma longa (CL) has potential antioxidant effects and may improve hyperglycemia in uncontrolled T1DM/TD1, as well as prevent its complications (higher costs for the maintenance of health per patient, functional disability, cardiovascular disease, and metabolic damage). In addition to the use of compounds to attenuate the effects triggered by diabetes, physical exercise is also essential for glycemic control and the maintenance of skeletal muscles. Our objective is to evaluate the effects of CL supplementation associated with moderate- to high-intensity resistance training on the parameters of body weight recovery, glycemic control, reactive species markers, and tissue damage in rats with T1DM/TD1.

Methods

Forty male 3-month-old Wistar rats (200–250 g) with alloxan-induced T1DM were divided into 4 groups (n = 7–10): sedentary diabetics (DC); diabetic rats that underwent a 4-week resistance training protocol (TD); CL-supplemented diabetic rats (200 mg/kg body weight, 3x a week) (SD); and supplemented diabetic rats under the same conditions as above and submitted to training (TSD). Body weight, blood glucose, and the following biochemical markers were analyzed: lipid profile, aspartate aminotransferase (AST), alanine aminotransferase (ALT), uric acid, creatine kinase (CK), lactate dehydrogenase (LDH), and thiobarbituric acid reactive substances (TBARS).

Results

Compared to the DC group, the TD group showed body weight gain (↑7.99%, p = 0.0153) and attenuated glycemia (↓23.14%, p = 0.0008) and total cholesterol (↓31.72%, p ≤ 0.0041) associated with diminished reactive species markers in pancreatic (↓45.53%, p < 0.0001) and cardiac tissues (↓51.85%, p < 0.0001). In addition, compared to DC, TSD promoted body weight recovery (↑15.44%, p ≤ 0.0001); attenuated glycemia (↓42.40%, p ≤ 0.0001), triglycerides (↓39.96%, p ≤ 0.001), and total cholesterol (↓28.61%, p ≤ 0.05); and attenuated the reactive species markers in the serum (↓26.92%, p ≤ 0.01), pancreas (↓46.22%, p ≤ 0.0001), cardiac (↓55.33%, p ≤ 0.001), and skeletal muscle (↓42.27%, p ≤ 0.001) tissues caused by T1DM.

Conclusion

Resistance training associated (and/or not) with the use of Curcuma longa attenuated weight loss, the hypoglycemic and hypolipidemic effects, reactive species markers, and T1DM-induced tissue injury.

Black tea and curcumin synergistically mitigate the hepatotoxicity and nephropathic changes induced by chronic exposure to aflatoxin-B1 in Sprague-Dawley rats

The study aimed to clarify the characteristics of black tea (BTE) and/or curcumin (CMN) against aflatoxin-B1 (AFB1). Forty eight adult male Sprague-Dawley rats were divided into eight groups. G1 was non-treated control. G2, G3, and G4 were olive oil, BTE, and CMN, respectively. G5 was olive oil-dissolved AFB1 (25 µg/kg b.w). G6, G7, and G8 were AFB1 along with BTE (2%), CMN (200 mg/kg b.w.), and BTE plus CMN, respectively. All treatments were orally given for consecutive 90 days. After treatment period, rats were sacrificed. Serobiochemical analysis and histopathology showed hepatorenal dysfunction in response to AFB1. Glutathione-antioxidants were significantly decreased versus increased lipid peroxides (p < .05-.001). AFB1 significantly increased the expression of the antitumor p53, but decreased that of antiapoptotic Bcl2 in liver or kidney tissue, either (p < .05). BTE or CMN ameliorated those changes induced by AFB1 in both liver and kidney with highly pronounced improvement when combined BTE/CMN was used. PRACTICAL APPLICATIONS: Black tea (BTE) and curcumin (CMN) were known for their antioxidant effects, and several studies reported their independent effects against different toxicities including aflatoxicosis. The current study clarifies the ameliorative characteristics of both agents; BTE and/or CMN, against the toxicity resulted from the chronic exposure to aflatoxin-B1 (AFB1) (25 µg/kg b.w. for consecutive 90 days). The dose of either agents, BTE or CMN, was 200 mg/kg b.w. along with AFB1. The pathologic changes, serobiochemical parameters, oxidative stress, histological changes, and the molecular disruption, induced by AFB1 in both liver and kidney were obviously and significantly ameliorated after BTE and/or CMN treatments in variable potencies where both agents showed the most effective antitoxic capacities.

Trans-resveratrol supplement lowers lipid peroxidation responses of exercise in male Wistar rats

Physical exercise increases free radicals production; antioxidant supplementation may improve the muscle fiber's ability to scavenge ROS and protect muscles against exercise-induced oxidative damage. This study was designed to examine the effects of all-trans resveratrol supplementation as an antioxidant to mediate anti-oxidation and lipid per-oxidation responses to exercise in male Wistar rats. Sixty-four male Wistar rats were randomly divided into four equal number (n = 16) including training + supplement (TS), training (T), supplement (S) and control (C) group. The rats in TS and S groups received a dose of 10 mg/kg resveratrol per day via gavage. The training groups ran on a rodent treadmill 5 times per week at the speed of 10 m/min for 10 min; the speed gradually increased to 30 m/min for 60 minutes at the end of 12^th week. The acute phase of exercise protocol included a speed of 25 m/min set to an inclination of 10° to the exhaustion point. Superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) activity, non-enzymatic antioxidants bilirubin, uric acid, lipid peroxidation levels (MDA) and the total antioxidant capacity (TAC) were measured after the exercise termination. The data were analyzed by using one-way ANOVA. The result showed that endurance training caused a significant increase in MDA level [4.5 ± 0.75 (C group) vs. 5.9 ± 0.41 nmol/l (T group)] whereas it decreased the total antioxidant capacity [8.5 ± 1.35 (C group) vs. 7.1 ± 0.55 mmol/l (T group)] (p = 0.001). In addition, GPx and CAT decreased but not significantly (p > 0.05). The training and t-resveratrol supplementation had no significant effect on the acute response of all variables except MDA [4.3 ± 1.4 (C group) vs. 4.0 ± 0.90 nmol/l (TS group)] (p = 0.001) and TAC [8.5 ± 0.90 (C group) vs. 6.6 ± 0.80 mmol/l (TS group)] (p = 0.004). It was concluded that resveratrol supplementation may prevent exercise-induced oxidative stress by preventing lipid peroxidation.

Gallic acid protects against the COPD-linked lung inflammation and emphysema in mice

OBJECTIVE AND DESIGN

Gallic acid (GA) a naturally occurring phenolic compound, known to possess antioxidant/anti-inflammatory activities. The aim of the present work was to investigate the beneficial effects of GA against COPD-linked lung inflammation/emphysema by utilizing elastase (ET) and cigarette smoke (CS)-induced mice model.

MATERIALS

Male BALB/c mice were treated with ET (1U/mouse) or exposed to CS (9 cigarettes/day for 4 days). GA administration was started 7 days (daily) prior to ET/CS exposure. Broncho-alveolar lavage was analyzed for inflammatory cells and pro-inflammatory cytokines. Lung homogenate was assessed for MPO activity/GSH/MDA/protein carbonyls. Further, Lung tissue was subjected to semi-quantitative RT-PCR, immunoblotting, and histological analysis.

RESULTS

GA suppressed the ET-induced neutrophil infiltration, elevated MPO activity and production of pro-inflammatory cytokines (IL-6/TNF-α/IL-1β) at 24 h. Reduced inflammation was accompanied with normalization of redox balance as reflected by ROS/GSH/MDA/protein carbonyl levels. Further, GA suppressed phosphorylation of p65NF-κB and IκBα along with down-regulation of IL-1β/TNF-α/KC/MIP-2/GCSF genes. Furthermore, GA offered protection against ET-induced airspace enlargement and ameliorated MMP-2/MMP-9. Finally, GA suppressed the CS-induced influx of neutrophils and macrophages and blunted gene expression of TNF-α/MIP-2/KC.

CONCLUSION

Overall, our data show that GA effectively modulates pulmonary inflammation and emphysema associated with COPD pathogenesis in mice.

Epigallocatechin-3-gallate Alleviates Cognitive Deficits in APP/PS1 Mice

Alzheimer's disease (AD) shows cognitive impairments in clinic, which is multifactorial with different etiopathogenic mechanisms such as Aβ deposition, neuroinflammation and neuronal dystrophy involved. Therefore, multi-targets drugs with neuroprotective, anti-amyloidogenic and anti-inflammatory properties will be effective in AD treatment. Epigallocatechin-3-gallate (EGCG) possesses a broad spectrum of pharmacological activities in the prevention and treatment of multiple neurodegenerative diseases. In the present study, we showed that oral administration of EGCG (50 mg/kg) for 4 months significantly attenuated the cognitive deficits in APP/PS1 transgenic mice, which served as AD model. Moreover, EGCG induced an improvement in dendritic integrity and expression levels of synaptic proteins in the brain of APP/PS1 mice. And EGCG exerted obvious anti-inflammatory effects, which was manifested by alleviating microglia activation, decreasing pro-inflammatory cytokine (IL-1β) and increasing anti-inflammatory cytokines (IL-10, IL-13). Furthermore, β-amyloid (Aβ) plaques were markedly reduced in the hippocampus of 6-month old APP/PS1 mice after EGCG treatment. In conclusion, these findings indicate that EGCG improves AD-like cognitive impairments through neuroprotective, anti-amyloidogenic and anti-inflammatory effects, thus is a promising therapeutic candidate for AD.

Effects of Timing of Acute and Consecutive Catechin Ingestion on Postprandial Glucose Metabolism in Mice and Humans

We examined the effects of the timing of acute and consecutive epigallocatechin gallate (EGCG) and catechin-rich green tea ingestion on postprandial glucose in mice and human adults. In mouse experiments, we compared the effects of EGCG administration early (morning) and late (evening) in the active period on postprandial glucose. In human experiments, participants were randomly assigned to the morning-placebo (MP, n = 10), morning-green tea (MGT, n = 10), evening-placebo (EP, n = 9), and evening-green tea (EGT, n = 9) groups, and consumed either catechin-rich green tea or a placebo beverage for 1 week. At baseline and after 1 week, participants consumed their designated beverages with breakfast (MP and MGT) or supper (EP and EGT). Venous blood samples were collected in the fasted state and 30, 60, 120, and 180 min after each meal. Consecutive administration of EGCG in the evening, but not in the morning, reduced postprandial glucose at 30 (p = 0.006) and 60 (p = 0.037) min in the evening trials in mice. In humans, ingestion of catechin-rich green tea in the evening decreased postprandial glucose (three-factor analysis of variance, p < 0.05). Thus, catechin intake in the evening more effectively suppressed elevation of postprandial glucose.

Oxidative Stress Parameters and Its Associations With Arterial Stiffness in Competitive Powerlifting Athletes After 12-Week Supervised Strength Training

Jürgenson, J, Serg, M, Kampus, P, Kals, J, Zagura, M, Viru, M, Zilmer, K, Zilmer, M, Eha, J, and Unt, E. Oxidative stress parameters and its associations with arterial stiffness in competitive powerlifting athletes after 12-week supervised strength training. J Strength Cond Res 33(7): 1816-1822, 2019-Available studies have not revealed a clear understanding of the impact of intensive strength training on arterial stiffness and oxidative stress (OxS) parameters, which may have a significant impact on further cardiovascular health of an athlete. The purpose of this study was to evaluate the effect of a 12-week supervised strength training program (SSTP) on oxidative stress indices and its relationship with arterial stiffness in powerlifting athletes. A total of 19 men (28 ± 6 years) exercised for 12 weeks (4 days per week with intensity 60-90% assessed from 1 repetition maximum, 90-120 minutes per session). Oxidative stress parameters and arterial stiffness (SphygmoCor 7.1) were measured before and after SSTP. The study results showed that total peroxide concentration increased and total antioxidant capacity decreased significantly after SSTP. There were no significant changes in carotid-femoral pulse wave velocity (cfPWV) or in the augmentation index. Correlation analysis revealed that the magnitude of the increase of cfPWV was significantly related to the increase of OxS. The current study demonstrated that a 12-week SSTP in powerlifting athletes produced significant changes in OxS indices, which were positively related to increased aortic stiffness. This novel finding may have significant implications about the effect of OxS on cardiovascular health after high-intensity strength training. Furthermore, strength and conditioningcoaches may have to consider the long-term exercise-induced changes in OxS on an individual level, where increased OxS leads to impaired arterial stiffness and cardiovascular health.

Resistance Exercise Selectively Mobilizes Monocyte Subsets: Role of Polyphenols

PURPOSE

To examine the impact of polyphenol supplementation on the recruitment, mobilization, and activation of monocyte subsets after resistance exercise.

METHODS

Thirty-eight recreationally active males (22.1 ± 3.1 yr; 173.9 ± 7.9 cm; 77.8 ± 14.5 kg) were assigned to 28 d of polyphenol blend (PPB) supplementation, placebo (PL), or control (CON). Blood samples were obtained before (PRE) postresistance exercise, immediately (IP) postresistance exercise, 1 h (1H) postresistance exercise, 5 h (5H) postresistance exercise, 24 h (24H) postresistance exercise, and 48 h (48H) postresistance exercise (PPB/PL) or rest (CON). Fine-needle biopsies were obtained from the vastus lateralis at PRE, 1H, 5H, and 48H. Circulating concentrations of macrophage chemoattractant protein-1 (MCP-1) and fractalkine, as well as intramuscular MCP-1 were analyzed via multiplex assay. Changes in the proportions and expression of CD11b on monocyte subsets were assessed via flow cytometry.

RESULTS

Circulating MCP-1 increased in PPB and PL at IP with further increases at 5H. Intramuscular MCP-1 was increased at 1H, 5H, and 48H in all groups. Classical monocyte proportions were reduced in PPB and PL at IP, and increased at 1H. Nonclassical monocytes were increased in PPB and PL at IP, whereas intermediate monocytes were increased at IP, and reduced at 1H. Intermediate monocytes were increased in PPB at 24H and 48H. CD11b expression was reduced on PPB compared with PL and CON at PRE on intermediate and nonclassical monocytes.

CONCLUSIONS

Resistance exercise may elicit selective mobilization of intermediate monocytes at 24H and 48H, which may be mediated by tissue damage. Additionally, polyphenol supplementation may suppress CD11b expression on monocyte subsets at rest.

Melatonin protects in vitro matured porcine oocytes from toxicity of Aflatoxin B1

Aflatoxin B1 (AFB1) is a major food and feed contaminant that threaten public health. Previous studies indicate that AFB1 exposure disrupted oocyte maturation. However, an effective and feasible method is unavailable for protecting oocytes against toxicity of AFB1. In the present study, using in vitro matured porcine oocytes and parthenogenetic embryos as model, we confirmed that AFB1 exposure during in vitro oocyte maturation (IVM) significantly impaired both nuclear and cytoplasmic maturation in a dose- and time-dependent manner. The different concentrations of melatonin were also tested for their protective effects on oocytes against the AFB1-induced toxicity. Our results showed that supplementation of a relative high concentration of melatonin (10^-3 mol/L) during IVM efficiently reversed the impaired development rate and blastocyst quality, to the levels comparable to those of the control group. Further analysis indicated that melatonin application efficiently alleviated reactive oxygen species accumulation and initiation of apoptosis induced by AFB1 exposure. In addition, disrupted GSH/GPX system, as well as inhibited mitochondrial DNA (mtDNA) replication and mitochondrial biogenesis in AFB1-treated oocytes, can be notably reversed by melatonin application. Furthermore, cumulus cells may be important in mediating the toxicity of AFB1 to oocytes, and the metabolism of AFB1 in cumulus cells can be depressed by melatonin. To the best of our knowledge, this is the first report to confirm that melatonin application can efficiently protect oocytes from AFB1-induced toxicity. Our study provides a promising and practical strategy for alleviating or reversing AFB1-induced female reproductive toxicity in both clinical treatment and domestic reproductive management.

Polyphenol supplementation alters intramuscular apoptotic signaling following acute resistance exercise

The purpose of this study was to examine the effects of 28‐days of supplementation with an aqueous proprietary polyphenol blend (PPB) sourced from Camellia sinensis on intramuscular apoptotic signaling following an acute lower‐body resistance exercise protocol and subsequent recovery. Untrained males (n = 38, 21.8 ± 2.7 years, 173.4 ± 7.9 cm, 77.6 ± 14.6 kg) were randomized to PPB (n = 14), placebo (PL; n = 14) or control (CON; n = 10). Participants completed a lower‐body resistance exercise protocol comprised of the squat, leg press, and leg extension exercises. Skeletal muscle microbiopsies were obtained from the vastus lateralis preexercise (PRE), 1‐h (1HR), 5‐h (5HR), and 48‐h (48HR) post‐resistance exercise. Apoptotic signaling pathways were quantified using multiplex signaling assay kits to quantify total proteins (Caspase 3, 8, 9) and markers of phosphorylation status (JNK, FADD, p53, BAD, Bcl‐2). Changes in markers of muscle damage and intramuscular signaling were analyzed via separate repeated measures analysis of variance (ANOVA). Change in Bcl‐2 phosphorylation at 1H was significantly greater in PL compared to CON (P = 0.001). BAD phosphorylation was significantly elevated at 5H in PL compared to PPB (P = 0.015) and CON (P = 0.006). The change in JNK phosphorylation was significantly greater in PPB (P = 0.009), and PL (P = 0.017) compared to CON at 1H, while the change for PL was elevated compared to CON at 5H (P = 0.002). A main effect was observed (P < 0.05) at 1H, 5H, and 48H for p53 and Caspase 8, with Caspase 3 and Caspase 9 elevated at 48H. These data indicate that chronic supplementation with PPB alters apoptotic signaling in skeletal muscle following acute muscle‐damaging resistance exercise.

Nutritional and Supplementation Strategies to Prevent and Attenuate Exercise-Induced Muscle Damage: a Brief Review

Exercise-induced muscle damage (EIMD) is typically caused by unaccustomed exercise and results in pain, soreness, inflammation, and reduced muscle function. These negative outcomes may cause discomfort and impair subsequent athletic performance or training quality, particularly in individuals who have limited time to recover between training sessions or competitions. In recent years, a multitude of techniques including massage, cryotherapy, and stretching have been employed to combat the signs and symptoms of EIMD, with mixed results. Likewise, many varied nutritional and supplementation interventions intended to treat EIMD-related outcomes have gained prominence in the literature. To date, several review articles have been published that explore the many recovery strategies purported to minimize indirect markers of muscle damage. However, these articles are very limited from a nutritional standpoint. Thus, the purpose of this review is to briefly and comprehensively summarize many of these strategies that have been shown to positively influence the recovery process after damaging exercise. These strategies have been organized into the following sections based on nutrient source: fruits and fruit-derived supplements, vegetables and plant-derived supplements, herbs and herbal supplements, amino acid and protein supplements, vitamin supplements, and other supplements.

Single Dose Administration of Taheebo Polyphenol Enhances Endurance Capacity in Mice

Endurance capacity is important for maintenance of quality of life as well as performance of endurance athletes. In order to improve endurance, intake of nutritional supplements as well as exercise training is also important. Indeed, polyphenolic extracts from plants are known to improve endurance capacity via increase of fatty acid utilization, mitochondrial biogenesis or inhibition of oxidative stress. Taheebo, the extract obtained from inner bark of Tabebuia avellanedae has been reported to have beneficial effects for treatment of inflammation, oxidative stress and obesity. Here, we investigated the effects and mechanisms of polyphenol fraction of taheebo (taheebo polyphenol; TP) on endurance capacity of mice. Single dose administration of TP significantly increased running time until exhaustion. Acute TP administration increased blood glucose and muscle glycogen levels (p < 0.05) through alteration on expression level of genes involved with glycogen metabolism and gluconeogenesis. Furthermore, TP administration decreased exercise-induced increase of protein carbonyls in skeletal muscle. These results suggest that TP administration improve endurance capacity via up-regulation of skeletal muscle glycogen levels and maintenance of blood glucose by acceleration of gluconeogenesis as well as inhibition of exercise-induced oxidative stress. Single administration of TP also increased phosphorylation of AMP-activated protein kinase (AMPK) and gene expression level of sirtuin 1 (SIRT1) but did not change the marker of mitochondrial biogenesis.

Green Tea Extract Preserves Neuromuscular Activation and Muscle Damage Markers in Athletes Under Cumulative Fatigue

A main implication of cumulative fatigue is the muscle damage that impairs neuromuscular function and training adaptations. These negative effects may limit performance when athletes exercise in consecutive days. In this regard, antioxidant supplementation has gain popularity among athletes. Green tea supplementation has been advocated as a strategy to improve exercise recovery due to the activity of its catechins with high antioxidant and anti-inflammatory potential. Here we performed a triple blinded placebo control experiment to determine the effect of green tea extract (GTE) from Camellia sinensis on muscle damage, oxidative stress, and neuromuscular activity in athletes submitted to consecutive sessions of exercise and fatigue. Sixteen trained amateur male athletes were randomly assigned to a GTE supplemented (500 mg/day) or placebo group during 15 days. Effects of supplementation were tested during repeated trials of submaximal cycling at 60% of peak power output performed after a protocol for cumulative fatigue of knee extensors. Muscle damage and oxidative stress showed lower magnitudes in response to fatigue after GTE supplementation. Placebo group showed impaired neuromuscular activity and higher muscle damage and oxidative stress compared to the GTE group during the cycling trials under fatigue. In summary, GTE supplementation showed positive effects on neuromuscular function in response to a condition of cumulative fatigue. It suggests GTE supplementation may have potential to serve as a strategy to improve performance and recovery in conditions of cumulative exercise.

Inhibitory activity of a green and black tea blend on Streptococcus mutans

Through the years, tea consumption has been associated with good health, and some publications are related to oral health. The bioactive components of green tea are thought to be able to influence the process of caries formation through inhibition of proliferation of the streptococcal agent, interference with the process of bacterial adhesion to tooth enamel, and inhibition of glucosyl transferase and amylase; however, little is known about black tea and oral health. The aim of the present in-vitro study was to determine the inhibitory activity of a novel, patent-pending and proprietary blend of green and black tea aqueous extracts on Streptococcus mutans, a bacterium widely associated with plaque development and tooth decay. A minimum inhibitory concentration (MIC) of 12.5 mg/mL and a minimum bactericidal concentration (MBC) of 12.5 mg/mL was established against S. mutans, meaning that at concentrations of 12.5 mg/mL and higher, the proprietary tea blend is effective against the growth of S. mutans. This MIC concentration is lower than the ones reported in the literature for alcoholic black tea and green tea extracts tested separately. As a promising natural ingredient for oral health, this finding is a good indicator for the use of this proprietary blend of black and green tea water extracts.

Impact of Polyphenol Supplementation on Acute and Chronic Response to Resistance Training

Beyer, KS, Stout, JR, Fukuda, DH, Jajtner, AR, Townsend, JR, Church, DD, Wang, R, Riffe, JJ, Muddle, TWD, Herrlinger, KA, and Hoffman, JR. Impact of polyphenol supplementation on acute and chronic response to resistance training. J Strength Cond Res 31(11): 2945–2954, 2017—This study investigated the effect of a proprietary polyphenol blend (PPB) on acute and chronic adaptations to resistance exercise. Forty untrained men were assigned to control, PPB, or placebo. Participants in PPB or placebo groups completed a 4-week supplementation period (phase I), an acute high-volume exercise bout (phase II), and a 6-week resistance training program (phase III); whereas control completed only testing during phase II. Blood draws were completed during phases I and II. Maximal strength in squat, leg press, and leg extension were assessed before and after phase III. The exercise protocol during phase II consisted of squat, leg press, and leg extension exercises using 70% of the participant's strength. The resistance training program consisted of full-body exercises performed 3 d·wk⁻¹. After phase I, PPB (1.56 ± 0.48 mM) had greater total antioxidant capacity than placebo (1.00 ± 0.90 mM). Changes in strength from phase III were similar between PPB and placebo. Polyphenol blend supplementation may be an effective strategy to increase antioxidant capacity without limiting strength gains from training.

The safety of green tea and green tea extract consumption in adults - Results of a systematic review

A systematic review of published toxicology and human intervention studies was performed to characterize potential hazards associated with consumption of green tea and its preparations. A review of toxicological evidence from laboratory studies revealed the liver as the target organ and hepatotoxicity as the critical effect, which was strongly associated with certain dosing conditions (e.g. bolus dose via gavage, fasting), and positively correlated with total catechin and epigallocatechingallate (EGCG) content. A review of adverse event (AE) data from 159 human intervention studies yielded findings consistent with toxicological evidence in that a limited range of concentrated, catechin-rich green tea preparations resulted in hepatic AEs in a dose-dependent manner when ingested in large bolus doses, but not when consumed as brewed tea or extracts in beverages or as part of food. Toxico- and pharmacokinetic evidence further suggests internal dose of catechins is a key determinant in the occurrence and severity of hepatotoxicity. A safe intake level of 338 mg EGCG/day for adults was derived from toxicological and human safety data for tea preparations ingested as a solid bolus dose. An Observed Safe Level (OSL) of 704 mg EGCG/day might be considered for tea preparations in beverage form based on human AE data.

Gallic Acid and Gallates in Human Health and Disease: Do Mitochondria Hold the Key to Success?

Gallic acid and gallate esters are widely used as dietary supplements or additives with clinical significances. Over the last few decades, a large number of publications have been reported stating the antioxidative, antiapoptotic, cardioprotective, neuroprotective, and anticancer properties of gallic acid and gallates, and mostly demonstrated their antioxidative or prooxidative properties influencing the reactive oxygen species (ROS) signaling networks. However, very little focus has been paid to clinical trials, and this restricted their use as a prescribed preventative supplement. Since mitochondria are the principal organelles responsible for ROS generation, we reviewed the existing literature of mitochondria-specific effects of gallates including ROS production, respiration, mitochondrial biogenesis, apoptosis, and the physico-chemical parameters affecting the outcome of gallate supplementation to various health scenarios such as cardiovascular diseases, neurodegeneration, hepatic ailments, or cancers. The major signaling pathways and the molecules targeted by gallic acid and its derivatives have also been discussed with emphasis on mitochondria as the target site. This review provides a better understanding of the effect of gallic acid and gallate esters on mitochondrial functions and in designing effective preventative measures against the onset of various diseases.

The effect of polyphenols on cytokine and granulocyte response to resistance exercise

This study examined the effect of resistance exercise on the production, recruitment, percentage, and adhesion characteristics of granulocytes with and without polyphenol (PPB) supplementation. Thirty‐eight untrained men were randomized into three groups: PPB (n = 13, 21.8 ± 2.5 years, 171.2 ± 5.5 cm, 71.2 ± 8.2 kg), placebo (PL; n = 15, 21.6 ± 2.5 years, 176.5 ± 4.9 cm, 84.0 ± 15.7 kg), or control (CON; n = 10, 23.3 ± 4.3 years, 173.7 ± 12.6 cm, 77.3 ± 16.3 kg). Blood samples were obtained pre (PRE), immediately (IP), 1 h (1H), 5 h (5H), 24 h (24H), 48 h (48H), and 96 h (96H) postresistance exercise (PPB/PL) or rest (CON). Fine‐needle biopsies were obtained from the vastus lateralis at PRE, 1H, 5H, and 48H. Plasma concentrations and intramuscular content of interleukin‐8 (IL‐8), granulocyte (G‐CSF), and granulocyte–macrophage colony stimulating factor (GM‐CSF) were analyzed via multiplex assays. Changes in relative number of circulating granulocytes and adhesion receptor (CD11b) were assessed using flow cytometry. Intramuscular IL‐8 was significantly elevated at 1H, 5H, and 48H (P < 0.001). Area under the curve analysis indicated a greater intramuscular IL‐8 content in PL than PPB (P = 0.011). Across groups, circulating G‐CSF was elevated from PRE at IP (P < 0.001), 1H (P = 0.011), and 5H (P = 0.025), while GM‐CSF was elevated at IP (P < 0.001) and 1H (P = 0.007). Relative number of granulocytes was elevated at 1H (P < 0.001), 5H (P < 0.001), and 24H (P = 0.005, P = 0.006) in PPB and PL, respectively. Across groups, granulocyte CD11b expression was upregulated from PRE to IP (P < 0.001) and 1H (P = 0.015). Results indicated an increase in circulating CD11b on granulocytes, and IL‐8 within the muscle following intense resistance exercise. Polyphenol supplementation may attenuate the IL‐8 response, however, did not affect granulocyte percentage and adhesion molecule expression in peripheral blood following resistance exercise.

The Effect of Dietary Supplements Containing Green Tea, Capsaicin and Ginger Extracts on Weight Loss and Metabolic Profiles in Overweight Women: A Randomized Double-Blind Placebo-Controlled Clinical Trial

BACKGROUND

This study was conducted to determine the effects of dietary supplements containing green tea, capsaicin and ginger extracts on weight loss and metabolic profiles among overweight women.

METHODS

This randomized double-blind placebo-controlled clinical trial was implemented among 50 overweight women. Participants were randomly divided into 2 groups. Group A received dietary supplements containing 125 mg green tea, 25 mg capsaicin and 50 mg ginger extracts (n = 25) group B received placebos (n = 25) twice with lunch and twice with dinner daily for 8 weeks.

RESULTS

Compared with placebo, taking dietary supplements containing green tea, capsaicin and ginger resulted in a significant decrease in weight (-1.8 ± 1.5 vs. +0.4 ± 1.2 kg, respectively, p < 0.001) and body mass index (BMI; -0.7 ± 0.5 vs. +0.1 ± 0.5 kg/m2, respectively, p < 0.001). In addition, subjects who received green tea, capsaicin and ginger co-supplements had significantly decreased serum insulin concentrations (-2.6 ± 3.9 vs. -0.6 ± 2.0 µIU/mL, p = 0.02), homeostatic model of assessment for insulin resistance (-0.5 ± 0.8 vs. -0.05 ± 0.6, p = 0.01), and increased quantitative insulin sensitivity check index (+0.01 ± 0.01 vs. +0.001 ± 0.01, p = 0.008) and plasma glutathione (GSH) levels (+73.8 ± 120.6 vs. -28.3 ± 193.4 µmol/L, p = 0.03) compared with the placebo.

CONCLUSIONS

Our study indicated that taking green tea, capsaicin and ginger co-supplements for 8 weeks among overweight women had beneficial effects on weight, BMI, markers of insulin metabolism and plasma GSH levels.

Antioxidants from black and green tea: from dietary modulation of oxidative stress to pharmacological mechanisms

The consumption of tea (Camellia sinensis) has been correlated with a low incidence of chronic pathologies, such as cardiovascular disease and cancer, in which oxidative stress plays a critical role. Tea catechins and theaflavins are, respectively, the bioactive phytochemicals responsible for the antioxidant activity of green tea (GT) and black tea (BT). In addition to their redox properties, tea catechins and theaflavins could have also pharmacological activities, such as the ability to lower glucose, lipid and uric acid (UA) levels. These activities are mediated by pharmacological mechanisms such as enzymatic inhibition and interaction with transporters. Epigallocatechin gallate is the most active compound at inhibiting the enzymes involved in cholesterol and UA metabolism (hydroxy-3-methyl-glutaryl-CoA reductase and xanthine oxidase respectively) and affecting glucose transporters. The structural features of catechins that significantly contribute to their pharmacological effect are the presence/absence of the galloyl moiety and the number and positions of the hydroxyl groups on the rings. Although the inhibitory effects on α-glucosidase, maltase, amylase and lipase, multidrug resistance 1, organic anion transporters and proton-coupled folate transport occur at higher concentrations than those apparent in the circulation, these effects could be relevant in the gut. In conclusion, despite the urgent need for further research in humans, the regular consumption of moderate quantities of GT and BT can effectively modulate their antioxidant capacity, mainly in people subjected to oxidative stress, and could improve the metabolism of glucose, lipid and UA.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Chemical constituents from a Gynostemma laxum and their antioxidant and neuroprotective activities

Background

A few bioactivities of constituents from Gynostemma laxum, which has been collected in Vietnam, have been reported until now. There is no report about the effects of constituents from G. laxum although the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated heme oxygenase-1 (HO-1) antioxidant defense system is involved in neuroprotection in the brain. Therefore, we investigated whether quercetin (2), benzoic acid (10) and their analogues (1, 3–9 and 11) from G. laxum have the antioxidant and neuroprotective activities and also their underlying mechanism.

Methods

To examine their neuroprotective and antioxidant activities, oxytosis, total oxidant scavenging capacity (TOSC), 2,7-dichlorofluorescein (DCFDA), dihydroethidium (DHE), antioxidant response element (ARE)-luciferase reporter gene assays, Western blot analysis, real time-PCR, immunocytochemistry and in silico 3D molecular docking simulation were performed.

Results

The study of constituents using chromatographic techniques and spectroscopic analysis showed that G. laxum contained an abundance of quercetin (2), benzoic acid (10) and their analogues (1, 3–9 and 11). Our data demonstrated that quercetin (2) and its analogue (4) among the constituents from G. laxum showed the strongest neuroprotective effect against oxytosis triggered by the excessive amount of glutamate. Compounds 2, 4, 6 and 11 exhibited reactive oxygen species (ROS) inhibitory and ARE transcriptional activities in immortalized hippocampal HT22 cell line. Among them, compound 4, a second active compound, induced Nrf2/HO-1 activation. They were also fit stable onto the Tramtrack and Bric-à-Brac (BTB) domain of Kelch-like ECH-associated protein 1 (Keap1), a known Nrf2 inhibitor protein, based on the results of docking and interaction energies. Overall, these data suggest that –OH and –OCH₃ groups of quercetin and its analogues are responsible for their neuroprotective effect.

Conclusions

In summary, the major constituents of G. laxum had strong antioxidant and neuroprotective activities so that they could consider as a natural antioxidant supplement. Furthermore, G. laxum might be used beneficially in reducing oxidative complications with the further deep investigation in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s13020-017-0136-y) contains supplementary material, which is available to authorized users.

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.

Green Tea and Bone Marrow Transplantation: From Antioxidant Activity to Enzymatic and Multidrug-resistance Modulation

Epigallocatechin-3-gallate (EGCG), the main flavonoid of green tea (GT), could play an active role in the prevention of oxidative-stress-related diseases, such as hematologic malignancies. Some effects of EGCG are not imputable to antioxidant activity, but involve modulation of antioxidant enzymes and uric acid (UA) levels. The latter is the major factor responsible of the plasma non-enzymatic antioxidant capacity (NEAC). However, hyperuricemia is a frequent clinical feature caused by tumor lysis syndrome or cyclosporine side effects, both before and after bone marrow transplantation (BMT). Besides this, food-drug interactions could be associated with GT consumption and could have clinical implications. The molecular mechanisms involved in the redox and drug metabolizing/transporting pathways were discussed, with particular reference to the potential role of GT and EGCG in BMT. Moreover, on reviewing data on NEAC, isoprostanes, uric acid, and various enzymes from human studies on GT, its extract, or EGCG, an increase in NEAC, without effect on isoprostanes, and contrasting results on UA and enzymes were observed. Currently, few and contrasting available evidences suggest caution for GT consumption in BMT patients and more studies are needed to better understand the potential impact of EGCG on oxidative stress and metabolizing/transporting systems.

Bioactive nutrients - Time for tolerable upper intake levels to address safety

There is increasing interest by consumers, researchers, and regulators into the roles that certain bioactive compounds, derived from plants and other natural sources, can play in health maintenance and promotion, and even prolonging a productive quality of life. Research has rapidly emerged suggesting that a wide range of compounds and mixtures in and from plants (such as fruits and vegetables, tea and cocoa) and animals (such as fish and probiotics) may exert substantial health benefits. There is interest in exploring the possibility of establishing recommended intakes or dietary guidance for certain bioactive substances to help educate consumers. A key aspect of establishing dietary guidance is the assessment of safety/toxicity of these substances. Toxicologists need to be involved in both the development of the safety framework and in the evaluation of the science to establish maximum intake/upper limits.

Potential neuroprotective properties of epigallocatechin-3-gallate (EGCG)

Neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) enforce an overwhelming social and economic burden on society. They are primarily characterized through the accumulation of modified proteins, which further trigger biological responses such as inflammation, oxidative stress, excitotoxicity and modulation of signalling pathways. In a hope for cure, these diseases have been studied extensively over the last decade to successfully develop symptom-oriented therapies. However, so far no definite cure has been found. Therefore, there is a need to identify a class of drug capable of reversing neural damage and preventing further neural death. This review therefore assesses the reliability of the neuroprotective benefits of epigallocatechin-gallate (EGCG) by shedding light on their biological, pharmacological, antioxidant and metal chelation properties, with emphasis on their ability to invoke a range of cellular mechanisms in the brain. It also discusses the possible use of nanotechnology to enhance the neuroprotective benefits of EGCG.

Green tea consumption is associated with reduced incident CHD and improved CHD-related biomarkers in the Dongfeng-Tongji cohort

Prospective studies on the association of green tea with risk of coronary heart disease (CHD) incidence were scarce. This study examined whether green tea can reduce CHD incidence and have a beneficial effect on CHD-related risk markers in middle-aged and older Chinese population. We included 19 471 participants who were free of CHD, stroke or cancer at baseline from September 2008 to June 2010, and were followed until October 2013. Cox proportional hazard models were used to examine the hazard ratios (HR) of CHD incidence in relation to green tea consumption. Linear regression models were used to evaluate the effect of green tea on 5-year changes of CHD-related biomarkers. Compared with non-green tea consumers, the multivariable-adjusted HR for CHD was 0.89 (95% CI, 0.81-0.98) in green tea consumers. Particularly, the reduced risk of CHD incidence with green tea consumption was more evident among participants who were male, more than 60 years old, overweight, or with diabetes mellitus. In addition, green tea consumption improved multiple CHD-related risk markers including total cholesterol, HDL-cholesterol, triglycerides, mean platelet volume, and uric acid. In conclusion, green tea consumption was associated with a reduced risk of CHD incidence in the middle-aged and older Chinese populations, and the association might be partly due to altered CHD-related biomarkers.

Supplementation with a polyphenolic blend improves post-exercise strength recovery and muscle soreness

Background

Exercise can initiate a cascade of inflammatory and oxidative stress–related events leading to delayed onset muscle soreness. Polyphenols possess antioxidant and anti-inflammatory properties.

Objective

The current study examined the effects of a proprietary polyphenolic blend (PB), containing catechins and theaflavins, on exercise performance and recovery following an eccentric exercise challenge.

Design

Male participants (18–35 years of age) received placebo or PB at a low dose (PB-L, 1,000 mg/d) or high dose (PB-H, 2,000 mg/d) for 13 weeks. During the 13th week of supplementation, participants completed an eccentric exercise (40 min downhill treadmill run) followed by a strength assessment (peak torque on isokinetic leg extensions) pre-exercise, and 24, 48, and 96 h post-exercise. Muscle soreness (subjective questionnaire), markers of muscle stress (cortisol and creatine phosphokinase [CK]), and antioxidant capacity (ferric reducing ability of plasma [FRAP]) were also assessed.

Results

PB-H attenuated the decrease in peak torque observed in the placebo group from pre-exercise to 48 h (p=0.012) and 96 h (p=0.003) post-exercise. At 48 h post-exercise, PB-H reduced whole body and hamstring soreness (p=0.029) versus placebo. Chronic consumption of PB improved serum FRAP (p=0.039). As expected, serum cortisol and CK increased from pre- to post-exercise in all groups; however, by 96 h, cortisol and CK levels returned to pre-exercise levels following PB supplementation. At 96 h, the change in cortisol from pre- to post-exercise was significantly greater in placebo versus PB-H (p=0.039).

Conclusion

These findings show that chronic consumption of PB improved antioxidant status, reduced markers of muscle stress, and promoted strength recovery post-exercise.

Consumption of açai (Euterpe oleraceaMart.) functional beverage reduces muscle stress and improves effort tolerance in elite athletes: a randomized controlled intervention study

The study analyzed the effect of an açai (Euterpe oleracea Mart.) functional beverage (AB) on muscle and oxidative stress markers, cardiorespiratory responses, perceived exertion, and time-to-exhaustion during maximal treadmill running. The beverage was developed as an ergogenic aid for athletes and contained 27.6 mg of anthocyanins per dose. Fourteen athletes performed 3 exercise tests: a ramp-incremental maximal exercise test and 2 maximal exercise bouts performed in 2 conditions (AB and without AB (control)) at 90% maximal oxygen uptake.Blood was collected at baseline and after maximal exercise in both conditions to determine biomarkers. AB increased time to exhaustion during short-term high-intensity exercise (mean difference: 69 s, 95% confidence interval = –296 s to 159 s, t = 2.2, p = 0.045), attenuating the metabolic stress induced by exercise (p < 0.05). AB also reduced perceived exertion and enhanced cardiorespiratory responses (p < 0.05). The AB may be a useful and practical ergogenic aid to enhance performance during high-intensity training.