Administration Of Green Tea Catechins Research Articles

The effect of long-term administration of green tea catechins on aging-related cardiac diastolic dysfunction and decline of troponin I

Aging is an independent risk factor for cardiovascular diseases. Cardiac diastolic dysfunction (CDD), ultimately leading to heart failure with preserved ejection fraction, is prevalent among older individuals. Although therapeutics have made great progress, preventive strategies remain unmet medical needs. Green tea catechins have been shown to be effective in improving aging-related cardiovascular and cerebral disorders in animal models and patients. However, little attention has been paid to whether long-term administration of epigallocatechin gallate (EGCG), the major bioactive ingredient of green tea catechins, could prevent the onset and progression of CDD. In this study, 12-month-old female mice were orally administered 50, 100, and 200 mg EGCG mixed with drinking water for 6 months. Aged mice (18 months old) exhibited the major features of heart failure with preserved ejection fraction, including CDD with preserved ejection fraction, cardiac fibrosis, increased cardiomyocyte apoptosis, and mitochondrial damages, as well as elevated A/B-type natriuretic peptide. Cardiac troponin I (cTnI) expression was also reduced. Long-term administration of 100 or 200 mg EGCG prevented aging-related CDD and exercise capacity decline, along with alleviating myocardial apoptosis and mitochondria damage. The transcription and protein expression of cTnI were increased, which might be achieved by inhibiting the expression and activity of histone deacetylase 1 and reducing its binding level near cTnI's promoter, thereby elevating acetylated histone 3 and acetylated lysine 9 on histone H3 in the aged mice. We provide a novel insight that long-term administration of EGCG is a potentially effective strategy in preventing aging-related CDD and cTnI expression decline.

Effects of green tea catechins on spatial learning abilities of wistar rats

Introduction: Green tea has drawn much attention because of the increase in the number of studies describing its potential health benefits which are attributed to Epigallocatechin-3-gallate (EGCG). Recent studies have also shown that in addition to antioxidant effects, green tea catechins modulates cell cycle signaling, generates non amylodogenic APP, enhances activity in dorsolateral prefrontal cortex etc. Materials and Method: The study was done in 18 male albino Wistar rats and divided in three groups of six. The spatial learning ability of rats were assessed by their behavior in 8 arm radial maze. Results: Statistical analysis was done using SPSS version 22 and data analyzed using Independence sample T test, Paired T test and ANOVA. The maze study showed an improvement in spatial learning ability of rats after green tea consumption in group1 and 2 as the time taken by the animal to complete the maze was found to be decreased. Conclusion: Administration of green tea catechins improves the spatial learning abilities of rats with an improved performance in radial maze tasks. The neuroprotective effect of green tea catechins may be due to their antioxidant property and hence can be used an effective tool in delaying cognitive impairment in elderly. Keywords: Green tea, EGCG, Radial maze, Cognition

Safety assessment of green tea based beverages and dried green tea extracts as nutritional supplements

The safety of green tea infusions and green tea extract (GTE)-based products is reviewed regarding catechins. Epigallocatechin 3-gallate (EGCG), the major catechin present in green tea, is suspected of being responsible for liver toxicity reported in humans consuming food supplements. Intake of EGCG with green tea infusions and GTE-based beverages is up to about 450mg EGCG/person/day in Europe and higher in Asia. Consumption of green tea is not associated with liver damage in humans, and green tea infusion and GTE-based beverages are considered safe in the range of historical uses. In animal studies, EGCG’s potency for liver effects is highly dependent on conditions of administration. Use of NOAELs from bolus administration to derive a tolerable upper intake level applying the margin of safety concept results in acceptable EGCG-doses lower than those from one cup of green tea. NOAELs from toxicity studies applying EGCG with diet/split of the daily dose are a better point of departure for risk characterization. In clinical intervention studies, liver effects were not observed after intakes below 600mg EGCG/person/day. Thus, a tolerable upper intake level of 300mg EGCG/person/day is proposed for food supplements; this gives a twofold safety margin to clinical studies that did not report liver effects and a margin of safety of 100 to the NOAELs in animal studies with dietary administration of green tea catechins.

Effects of green tea catechins with or without caffeine on glycemic control in adults: a meta-analysis of randomized controlled trials

The effect of green tea catechins (GTCs) with or without caffeine on glycemic control is controversial. We aimed to identify and quantify the effects of GTCs or GTC-caffeine mixtures on glucose metabolism in adults. A comprehensive literature search was conducted to identify relevant trials of GTCs with or without caffeine on markers of glycemic control [fasting blood glucose (FBG), fasting blood insulin (FBI), glycated hemoglobin (Hb A1c), and homeostatic model assessment of insulin resistance (HOMA-IR)]. Weighted mean differences were calculated for net changes by using fixed-effects models. Prespecified subgroup analyses were performed to explore the influence of covariates on net changes in FBG and FBI concentrations. Twenty-two eligible randomized controlled trials with 1584 subjects were identified. Pooled analyses showed that FBG (-1.48 mg/dL; 95% CI: -2.57, -0.40 mg/dL) decreased significantly with GTCs with or without caffeine, whereas FBI (0.04 μU/mL; 95% CI: -0.36, 0.45 μU/mL), Hb A1c (-0.04%; 95% CI: -0.15, 0.08%), and HOMA-IR (-0.05; 95% CI: -0.37, 0.26) did not. Subgroup analyses indicated that the glucose-lowering effect was apparent when the duration of follow-up was over a median of 12 wk. Overall, no significant heterogeneity was detected for FBG, FBI, Hb A1c, or HOMA-IR. The meta-analysis showed that the administration of GTCs with or without caffeine resulted in a significant reduction in FBG. The limited data available on GTCs did not support a positive effect on FBI, Hb A1c, or HOMA-IR. Thus, more large and well-designed trials are needed in the future. This trial was registered at http://www.crd.york.ac.uk/prospero as CRD42012002139.

Tu1174 Attenuated Progression of Gastric Dysplasia by Administration of Green Tea Catechins in INS-GAS Mice

Backgrounds: Green tea catechins (GTCs) have been shown to provide anti-carcinogenic effects in several laboratory studies. Although the effect of green tea consumption on the risk of gastric cancer has been studied in epidemiological studies, the results remain controversial. The anti-carcinogenic mechanisms of GTCs have not been fully evaluated in rodent models of gastric cancer. Previous reports indicate that transgenic INS-GASmice are hypergastrinemic and induced corpus gastritis and eventually developed gastric cancer at over 20 months old. Aim: The aim of our study was to investigate the molecular effects of GTCs on gastritis and premalignant lesions in INS-GAS mice. Methods: Thirty eight, male INSGAS mice on a FVB background were used in this study. Mice were divided into two groups: A GTCs group and control. Mice in the GTCs group were allowed free access to drinking water containing 2000ppm of GTCs from the age of 9 weeks. Mice were euthanized at the age of 13 or 37 weeks. Histological scores (inflammation and dysplasia) were graded on a blinded basis by pathologist on a scale from 0 to 4. The mRNA expressions of IFN-gamma and TNF-alpha in the corpus of stomachs were evaluated using quantitative PCR. Statistical analysis was performed using a Mann-Whitney U test. Results: Body weights in mice supplemented with GTCs were significantly lower than that of controls at both 13 and 37 weeks of age (p < 0.05). Treated and control mice developed minimal to mild corpus gastritis, although dysplasia was evident. The histological score of dysplasia in mice supplemented with GTCs was significantly lower than that in controls at 37 weeks of age (p < 0.05). GTCs supplementation did not affect the inflammation score. The mRNA level of IFN-gamma in mice administrated GTCs was significantly lower than that of controls at 13 weeks of age (p < 0.05), although it did not reach statistical significance at 34 weeks of age (p = 0.056). GTCs supplementation did not alter TNF-alpha mRNA expression levels between both groups. Conclusions: Administration of GTCs attenuated progression of gastric dysplasia in INS-GAS male mice. These results demonstrated that IFN-gamma dependent mechanisms may be involved in the protective role of GTCs in development of gastritis and premalignant lesions in this rodent model.

Tu1175 The Protective Influence of Vitamin D in Hepatocellular Carcinoma

Backgrounds: Green tea catechins (GTCs) have been shown to provide anti-carcinogenic effects in several laboratory studies. Although the effect of green tea consumption on the risk of gastric cancer has been studied in epidemiological studies, the results remain controversial. The anti-carcinogenic mechanisms of GTCs have not been fully evaluated in rodent models of gastric cancer. Previous reports indicate that transgenic INS-GASmice are hypergastrinemic and induced corpus gastritis and eventually developed gastric cancer at over 20 months old. Aim: The aim of our study was to investigate the molecular effects of GTCs on gastritis and premalignant lesions in INS-GAS mice. Methods: Thirty eight, male INSGAS mice on a FVB background were used in this study. Mice were divided into two groups: A GTCs group and control. Mice in the GTCs group were allowed free access to drinking water containing 2000ppm of GTCs from the age of 9 weeks. Mice were euthanized at the age of 13 or 37 weeks. Histological scores (inflammation and dysplasia) were graded on a blinded basis by pathologist on a scale from 0 to 4. The mRNA expressions of IFN-gamma and TNF-alpha in the corpus of stomachs were evaluated using quantitative PCR. Statistical analysis was performed using a Mann-Whitney U test. Results: Body weights in mice supplemented with GTCs were significantly lower than that of controls at both 13 and 37 weeks of age (p < 0.05). Treated and control mice developed minimal to mild corpus gastritis, although dysplasia was evident. The histological score of dysplasia in mice supplemented with GTCs was significantly lower than that in controls at 37 weeks of age (p < 0.05). GTCs supplementation did not affect the inflammation score. The mRNA level of IFN-gamma in mice administrated GTCs was significantly lower than that of controls at 13 weeks of age (p < 0.05), although it did not reach statistical significance at 34 weeks of age (p = 0.056). GTCs supplementation did not alter TNF-alpha mRNA expression levels between both groups. Conclusions: Administration of GTCs attenuated progression of gastric dysplasia in INS-GAS male mice. These results demonstrated that IFN-gamma dependent mechanisms may be involved in the protective role of GTCs in development of gastritis and premalignant lesions in this rodent model.

Evaluation of oxidative stress and antioxidative action of green tea catechins in patients treated with tamoxifen: a randomized open-label, crossover study

The relation between oxidative stress and tamoxifen is not completely clear, since some studies attribute a possible antioxidant action, while others describe several pro-oxidative effects. The aim of this study was to evaluate oxidative stress in patients treated with tamoxifen and the effect of administration of green tea catechins on this parameter. Tests aimed at evaluating the derivatives of reactive oxygen metabolites (d-Roms test) and the antioxidant reserve (BAP test) were adopted to estimate oxidative stress. Subjects treated with tamoxifen received Categ [Sofar] (green tea extract with 200 mg of catechins, 2 tablets twice a day for 3 weeks), according to a crossover design. High or very high antioxidant stress levels were found in all the 46 patients treated with tamoxifen, while in a control group of 18 patients treated with aromatase inhibitors or who had no longer been treated with tamoxifen for 1 year or more, high or very high oxidative stress levels were found in 66.7% of cases (p < 0.0001). The antioxidant reserve was low in 52% of patients treated with tamoxifen versus 40% of the patients in the control group, but the difference was not statistically significant (p = n.s.). The levels of oxidative stress and antioxidant reserve did not change significantly in a subgroup where the patients took Categ for 3 weeks followed by 3 weeks washout (group A), while there was a statistical significant reduction in the levels of oxidative stress (p < 0.05) and an increase in the antioxidant reserve (p < 0.01) in the subgroup where 3 weeks of no treatment were followed by 3 weeks of treatment with Categ (group B). In conclusion, our study confirms a pro-oxidant effect of tamoxifen. The supplementation with green tea catechins gave discordant results. A high number of variables might intervene in the delicate oxidative–reductive equilibrium of human beings and, despite progress achieved in the last few years, there are several aspects concerning the oxidative–reductive equilibrium that still have to be explained.

Effect of green tea catechins with or without caffeine on anthropometric measures: a systematic review and meta-analysis

Green tea catechins (GTCs) with or without caffeine have been studied in randomized controlled trials (RCTs) for their effect on anthropometric measures and have yielded conflicting results. The objective was to perform a systematic review and meta-analysis of RCTs of GTCs on anthropometric variables, including body mass index (BMI), body weight, waist circumference (WC), and waist-to-hip ratio (WHR). A systematic literature search of MEDLINE, EMBASE, CENTRAL, and the Natural Medicines Comprehensive Database was conducted through April 2009. RCTs that evaluated GTCs with or without caffeine and that reported BMI, body weight, WC, or WHR were included. The weighted mean difference of change from baseline (with 95% CIs) was calculated by using a random-effects model. Fifteen studies (n = 1243 patients) met the inclusion criteria. On meta-analysis, GTCs with caffeine decreased BMI (-0.55; 95% CI: -0.65, -0.40), body weight (-1.38 kg; 95% CI: -1.70, -1.06), and WC (-1.93 cm; 95% CI: -2.82, -1.04) but not WHR compared with caffeine alone. GTC ingestion with caffeine also significantly decreased body weight (-0.44 kg; 95% CI: -0.72, -0.15) when compared with a caffeine-free control. Studies that evaluated GTCs without concomitant caffeine administration did not show benefits on any of the assessed anthropometric endpoints. The administration of GTCs with caffeine is associated with statistically significant reductions in BMI, body weight, and WC; however, the clinical significance of these reductions is modest at best. Current data do not suggest that GTCs alone positively alter anthropometric measurements.

Long-term administration of green tea catechins prevents age-related spatial learning and memory decline in C57BL/6 J mice by regulating hippocampal cyclic amp-response element binding protein signaling cascade

Flavonoid-rich foods have been shown to be effective at reversing age-related deficits in learning and memory in both animals and humans. However, little investigation of the preventative effects of flavonoids on the naturally aged animals was reported. In our study, 14-month-old female C57BL/6 J mice were orally administered 0.025%, 0.05% and 0.1% green tea catechins (GTC, w/v) in drinking water for 6 months; we found that a supplementation with 0.05% or 0.1% GTC prevented age-related spatial learning and memory decline of mice in the Morris water maze. Better performance of GTC-treated mice was associated with increased levels of cAMP-response element binding protein (CREB) phosphorylation in the hippocampus. The expressions of brain-derived neurotrophic factor (BDNF) and Bcl-2, two target genes of CREB which can exhibit long-term regulatory roles in synaptic plasticity and synaptic structure, were also increased. We also found that long-term 0.05% or 0.1% GTC administration prevented age-related reductions of two representative post-synaptic density proteins PSD95 and Ca 2+/calmodulin-dependent protein kinase II, suggesting that synaptic structural changes may be involved. These results demonstrated that long-term 0.05% or 0.1% green tea catechin administration may prevent age-related spatial learning and memory decline of female C57BL/6 J mice by regulating hippocampal CREB signaling cascade.

Green tea catechins prevent cognitive deficits caused by Aβ 1–40 in rats

Amyloid β peptide (Aβ)-induced oxidative stress is involved in the pathogenesis of Alzheimer's disease (AD). In contrast, green tea catechins confer potent antioxidative defense to brain neurons. Therefore, we examined whether long-term administration of green tea catechins [Polyphenon E (PE): 63% of epigallocatechin-3-gallate, 11% of epicatechin, 6% of (−)-epigallocatechin and 6% of (−)-epicatechin-gallate] prevents cognitive impairment in an animal model of AD, rats infused with Aβ 1–40 into the cerebral ventricle. Five-week-old male Wistar rats fed with an MF diet were randomly divided into two groups: 0.0% PE (rats administered with water only) and 0.5% PE (rats administered with 5 g/L of PE). Twenty weeks after the PE administration, the 0.0% PE group was divided into the Vehicle group (rats infused with the solvent used for dissolving Aβ) and the Aβ 1–40-infused rat group (Aβ group), whereas the 0.5% PE group was divided into the PE+Vehicle group (PE-preadministered vehicle-infused rats) and the PE+Aβ group (PE-preadministered Aβ-infused rats). Aβ 1–40 or vehicle was infused into the cerebral ventricle using a mini osmotic pump. Behavioral changes in the rats were assessed by an eight-arm radial maze. PE administration for 26 weeks significantly decreased the Aβ-induced increase in the number of reference and working memory errors, with a concomitant reduction of hippocampal lipid peroxide (LPO; 40%) and cortico-hippocampal reactive oxygen species (ROS; 42% and 50%, respectively). Significantly reduced levels of LPO in the plasma (24%) and hippocampus (25%) as well as those of ROS in the hippocampus (23%) and cortex (41%) were found in the PE+Vehicle group as compared with the Vehicle group. Furthermore, rats with preadministered PE had higher ferric-reducing antioxidation power of plasma as compared with the Vehicle group. Our results suggest that long-term administration of green tea catechins provides effective prophylactic benefits against Aβ-induced cognitive impairment by increasing antioxidative defenses.

Long-Term Administration of Green Tea Catechins Improves Spatial Cognition Learning Ability in Rats

Green tea catechins confer potent biological properties including antioxidation and free-radical scavenging. We investigated the effect of long-term oral administration of green tea catechins (Polyphenon E, PE: EGCG 63%; EC 11%; EGC 6%; ECG 6%) mixed with water on the spatial cognition learning ability of young rats. The learning ability of rats administered PE (0%, 0.1%, 0.5%) for 26 wk was assessed in the partially baited 8-arm radial maze. Relative to controls, those administered PE had improved reference and working memory-related learning ability. They also had lower plasma concentrations of lipid peroxides and greater plasma ferric-reducing antioxidation power than controls. Furthermore, rats administered PE had lower hippocampus reactive oxygen species concentrations than controls. We suggest that this improvement in spatial cognitive learning ability is due to the antioxidative activity of green tea catechins.

Chemoprevention of Human Prostate Cancer by Oral Administration of Green Tea Catechins in Volunteers with High-Grade Prostate Intraepithelial Neoplasia: A Preliminary Report from a One-Year Proof-of-Principle Study

Green tea catechins (GTCs) proved to be effective in inhibiting cancer growth in several experimental models. Recent studies showed that 30% of men with high-grade prostate intraepithelial neoplasia (HG-PIN) would develop prostate cancer (CaP) within 1 year after repeated biopsy. This prompted us to do a proof-of-principle clinical trial to assess the safety and efficacy of GTCs for the chemoprevention of CaP in HG-PIN volunteers. The purity and content of GTCs preparations were assessed by high-performance liquid chromatography [(-)-epigallocathechin, 5.5%; (-)-epicatechin, 12.24%; (-)-epigallocatechin-3-gallate, 51.88%; (-)-epicatechin-3-gallate, 6.12%; total GTCs, 75.7%; caffeine, <1%]. Sixty volunteers with HG-PIN, who were made aware of the study details, agreed to sign an informed consent form and were enrolled in this double-blind, placebo-controlled study. Daily treatment consisted of three GTCs capsules, 200 mg each (total 600 mg/d). After 1 year, only one tumor was diagnosed among the 30 GTCs-treated men (incidence, approximately 3%), whereas nine cancers were found among the 30 placebo-treated men (incidence, 30%). Total prostate-specific antigen did not change significantly between the two arms, but GTCs-treated men showed values constantly lower with respect to placebo-treated ones. International Prostate Symptom Score and quality of life scores of GTCs-treated men with coexistent benign prostate hyperplasia improved, reaching statistical significance in the case of International Prostate Symptom Scores. No significant side effects or adverse effects were documented. To our knowledge, this is the first study showing that GTCs are safe and very effective for treating premalignant lesions before CaP develops. As a secondary observation, administration of GTCs also reduced lower urinary tract symptoms, suggesting that these compounds might also be of help for treating the symptoms of benign prostate hyperplasia.