Green Tea Extract Intake Research Articles

Effects of maternal high-fat diet and green tea extract Intake on autophagy in the liver of adult rat offspring

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Effect of Green Tea Extract Ingestion on Fat Oxidation during Exercise in the Menstrual Cycle: A Pilot Study.

In women, fat oxidation during exercise changes with the menstrual cycle. This study aimed to investigate the effect of green tea extract (GTE) ingestion on fat oxidation during exercise depending on the menstrual cycle phase. Ten women with regular menstrual cycles participated in this randomized, double-blind, crossover study. GTE or placebo was administered during the menstrual cycle’s follicular phase (FP) and luteal phase (LP). Participants cycled for 30 min at 50% maximal workload, and a respiratory gas analysis was performed. Serum estradiol, progesterone, free fatty acid, plasma noradrenaline, blood glucose, and lactate concentrations were assessed before, during, and after the exercise. Fat oxidation, carbohydrate oxidation, and the respiratory exchange ratio (RER) were calculated using respiratory gas. Fat oxidation during the exercise was significantly higher in the FP than in the LP with the placebo (p < 0.05) but did not differ between the phases with GTE. Carbohydrate oxidation, serum-free fatty acid, plasma noradrenaline, blood glucose, and lactate concentrations were not significantly different between the phases in either trial. Our results suggest that GTE ingestion improves the decrease in fat oxidation in the LP.

Ingestion Of Green Tea Extract In The Luteal Phase Improves Fat Oxidation During Exercise

Ingestion Of Green Tea Extract In The Luteal Phase Improves Fat Oxidation During Exercise

The Effect of Green Tea Extract Supplementation and Different Catechol-O-Methyltransferase Genotypes on Plasma Catechins Concentrations in Women Who Are Post-menopause

ObjectivesTo determine if oral intake of green tea extract (GTE) capsules increases plasma concentrations of green tea catechins, and if genotypes impact changes in plasma concentrations of catechins. MethodsThis study was a secondary analysis of the Minnesota Green Tea Trial (MGTT), a randomized, double-blind, placebo-controlled trial. Participants were healthy postmenopausal women receiving GTE capsules with 843.0 mg epigallocatechin gallate (EGCG) or placebo daily for 12 months. In a subset of the participants (n = 178) plasma concentrations of green tea catechins were analyzed at baseline and month 12. Absolute changes in concentrations of plasma catechins including EGCG, epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC) were compared between treatment groups, and between COMT genotypes among those in the GTE group. Findings were stratified by potential confounding factors. ResultsParticipants were mainly white non-Hispanic with a mean ± SD age of 60.13 ± 5.14 years and BMI of 24.97 ± 3.76 kg/m2. Absolute changes from baseline in plasma concentrations of EGCG (46.32 vs. 0.00 nM), ECG (18.39 vs. 0.00 nM), and EC (15.56 vs 0.06 nM) were significantly higher in the GTE than the placebo group, respectively (all Ps < 0.001). After adjusting for age and dietary intakes of fiber and vitamin C, absolute changes from baseline in plasma concentrations of EGCG were significantly greater in the high-activity COMT genotype (G/G) compared to those with the low-activity COMT genotypes (A/A or A/G) in the GTE group (P = 0.048). There was a statistically significant interaction between treatment and total vitamin C intake at baseline for absolute change from baseline of plasma EC (Pint = 0.008). Participants in the GTE group with vitamin C intake above median values at baseline experienced significantly greater positive increases in plasma concentration of EC compared to those in the placebo group. ConclusionsConcentrations of plasma EGCG, ECG, and EC were significantly increased after GTE supplementation for 12 months. COMT genotype may modify circulating EGCG concentrations; the entailed mechanism remains to be investigated. Funding SourcesNIH (Grant R01 CA127236).

Effects of epigallocatechin gallate-enriched green tea extract capsules in uterine myomas: results of an observational study.

The daily ingestion of green tea extract (GTE) capsules in women with oligo- or asymptomatic uterine myomas was monitored over 6months with regard to their quality of life, myoma-associated complaints and side effects. The participants were interviewed and examined at the beginning of the study (T1) and then again after 6months (T3). Quality of life was assessed using a SF-12 questionnaire while their myoma-associated complaints were ascertained by using a self-developed myoma symptom questionnaire. Changes in the size of the myomas were evaluated by vaginal sonography. Side effects after 3months (T2) and 6months were documented by systematic interviews. Overall; 25 participants (median 45years) have been enrolled. The analysis of the SF-12 questionnaire showed a significant improvement of the physical cumulative score of the SF-12 during the 6month GTE capsule ingestion (T1: mean value (M) = 52.731; 95% confidence interval (KI95%): 49.791-55.671; T3: M = 55.862; KI95%%: 55.038-56.685; p = 0.019). However, the mental cumulative score of the SF-12 did not change significantly (p = 0.674). No significant correlation could be established between the capsule ingestion and changes in the symptom questionnaire, the laboratory parameters nor the myoma size. No relevant adverse side effects were reported. Women who took GTE capsules showed a significant improvement in their physical cumulative score on the SF-12, but not in the global QoL score. Myoma size or other objective parameters did not change.

Maternal green tea extract intake during lactation attenuates hepatic lipid accumulation in adult male rats exposed to a continuous high-fat diet from the foetal period.

BackgroundMaternal lipid intake in the early postnatal period has a long-term effect on the possibility of fatty liver formation in children; besides, the importance of lipid consumption during lactation for children’s health has been suggested. Green tea extract (GTE) contains abundant catechins, and it has been reported to improve lipid metabolism and prevent fatty liver.ObjectiveThe aim of this study was to examine the effects of maternal GTE intake during lactation on hepatic lipid accumulation in adult male rats exposed to a continuous high-fat (HF) diet from the foetal period.MethodsPregnant Wistar rats received diets containing 13% (control-fat, CON) or 45% (high-fat, HF) fat. CON-fed mothers received the same diet during lactation, whereas HF-fed mothers received either HF diet alone or HF diet supplemented with 0.24% GTE. At weaning, male offspring were divided into three groups, i.e. CON/CON/CON, HF/HF/HF (HF-offspring) or HF/HF+GTE/HF (GTE-offspring), and were fed until 51 weeks.ResultsA significant hepatic triglyceride (Tg) accumulation was observed in the HF-offspring when compared with the other offspring. This is presumed to be caused by the promotion of Tg synthesis derived from exogenous fatty acid due to a significant increase in diacylglycerol O-acyltransferase 1 and a decrease in Tg expenditure caused by decreasing microsomal triglyceride transfer protein (MTTP) and long-chain acyl-CoA dehydrogenase. On the other hand, attenuated hepatic Tg accumulation was observed in the GTE-offspring. The levels of the hepatic lipid metabolism-related enzymes were improved to the same level as the CON-offspring, and particularly, MTTP was significantly increased as compared with the HF-offspring.ConclusionThis study indicates the potential protective effects of maternal GTE intake during lactation on HF diet-induced hepatic lipid accumulation in adult male rat offspring and the possible underlying mechanisms.

The effects of green tea on acne vulgaris: A systematic review and meta-analysis of randomized clinical trials.

Green tea extract (GTE) has been studied for the treatment of acne based on its anti-inflammatory/antioxidant properties. This systematic review and meta-analysis aimed to examine the effects of GTE on acne. Electronic databases, including PubMed, Embase, and the Cochrane Library were systematically searched up to August 2019. The effect size of acne lesion counts is presented as mean differences and 95% confidence intervals (CIs). Five randomized-controlled studies were included in the meta-analysis (N; experimental = 125, control = 122). GTE significantly reduced the number of inflammatory lesions (-9.38; 95% CI: -14.13 to -4.63). In subgroup analysis, topical GTE application significantly reduced the inflammatory lesion counts (-11.39; 95% CI: -15.91 to -6.86) whereas oral GTE intake showed minimal effect (-1.40; 95% CI: -2.50 to -0.30). Although GTE did not significantly reduce the number of non-inflammatory lesions (-21.65; 95% CI: -47.52 to 4.22), when stratified by the route of admission, non-inflammatory acne lesions were significantly reduced by topical GTE application (-32.44; 95% CI: -39.27 to -25.62) but not with oral GTE administration (0.20; 95% CI: 0.00 to 0.40). This systematic review and meta-analysis suggest that topical GTE application is beneficial for the treatment of acne without causing significant adverse events while oral GTE intake has limited effects. Further high-quality clinical trials are warranted.

Green tea extract to prevent colorectal adenomas in men and women: Results of the MIRACLE trial.

1551 Background: Prevention of colorectal adenomas (CA) can reduce colorectal cancers (CRC). Epidemiological and experimental data suggest that the green tea catechin epigallocatechingallate has an antineoplastic effect in the large bowel. MIRACLE is the largest trial so far to examine the effect of three-year daily intake of green tea extract (GTE) on the incidence of metachronous CA in a Caucasian population. Methods: Prospective, parallel group, double-blinded, placebo-controlled, randomized multicenter trial (40 German centers, recruitment 11/2011-6/2015). Patients (n = 1001, age 50-80y), polypectomy ≤ 6 months and tolerating GTE well (one-month run-in) were randomized to receive decaffeinated GTE standardized to EGCG (150 mg bid, capsules) or placebo (P) for 3 years. Primary endpoint: Incidence of metachronous CA at the 3-year follow-up colonoscopy. Secondary endpoints: Occurrence, number, localization, size, histological subtype of CA, frequency of CRC, biomarker and safety. Strata: study center, low-dose aspirin (≤100 mg/d). Results: Clinical parameters were well balanced. CA incidence at the 3-year follow-up colonoscopy was analyzed in the modified ITT set (modITT; n = 309 patients (GTE), n = 323 (placebo), timely follow up colonoscopy) and the per protocol set (PP, modITT set without major protocol violations). Incidence of CA was 55.7 % (P) and 51.1% (GTE), (modITT, adj. RR 0.905, one sided, p = 0.081), respectively 54.3 % (P) and 48.3% (GTE) (PP, adj. RR 0.883, one sided, p = 0.058). These differences did not reach statistical significance. In the preplanned exploratory analysis regarding gender incidence of CA in females was 47.9% (P) and 47.6% (GTE) in the modITT-set (adj. RR 0.989; 95%-CI: 0.753,1.299; p = 0.935), respectively 45.4% (P) and 46.9% (GTE) in the PP-set (adj. RR 1.014; 95%-CI: 0.748, 1.373; p = 0.930). In contrast, in the male population incidence of CA in the follow-up colonoscopy was 60.4% (P) and 52.9% (GTE) in the modITT-set (adj. RR 0.846; 95% CI 0.717, 0.999); p = 0.048), respectively 59.1% (P) and 49.1% (GTE) in the PP-set (RR 0.803, 95% CI: 0.666, 0.969; p = 0.022). Thus, GTE intake was associated with a significant, 12.4 relative and 7.5% absolute reduction of metachronous CA in the male modITT population. There were no differences with respect to safety between the groups. Conclusions: GTE reduced the incidence of metachronous CA. However, a significant effect was only observed in the in the male population whereas there was no effect in the female population. Clinical trial information: NCT 01360320.

Effect of green tea extract on lipid profile in patients with type 2 diabetes mellitus: A systematic review and meta-analysis

BackgroundPrevious studies have indicated controversial results regarding the efficacy of green tea extract (GTE) in improving the lipid profile of type 2 diabetes mellitus (T2DM) patients. We aimed to conduct a systematic review and meta-analysis to pool data from randomized controlled trials (RCTs). MethodsA systematic search was performed in Web of Science, PubMed, and Scopus databases, without any language and time restriction until August 2019, to retrieve the RCTs which examined the effects of GTE on serum concentrations of high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglyceride (TG) or total cholesterol (TC) in T2DM patients. Meta-analyses were carried out using a random effects model. I2 index was used to evaluate the heterogeneity. ResultsInitial search yielded 780 publications. Of these, seven studies were eligible. The supplementary intake of GTE improved lipid profile by reducing serum TG concentrations in patients with T2DM. Meanwhile, subgroup analyses based on duration of interventions (≤8 and > 8 weeks) and intervention dosage (≤800 and > 800 mg/day) showed that the GTE supplementation longer than 8 weeks and in doses >800 mg/day resulted in a significant decrease in serum TG concentrations. Furthermore, intervention longer than 8 weeks with doses lower than 800 mg/day resulted in a significant reduction in serum TC concentrations. ConclusionIn conclusion, present systematic review and meta-analysis revealed that the supplementary intake of GTE may improve lipid profile by reducing serum concentrations of TG in patients with T2DM. Furthermore, the results of our stratified analyses suggested that long-term GTE intervention may reduce serum concentrations of TG and TC.

Green tea catechins adsorbed on the murine pharyngeal mucosa reduce influenza A virus infection

Abstract Green tea consumption reduces influenza incidence in human populations. However, where and how green tea exerts its anti-viral activities remain unclear. Here, we examined the adsorption of green tea catechins on the pharyngeal mucosa at 3–60 min after ingestion of green tea extract (GTE) and the role this adsorption plays in preventing influenza A virus (IAV) infection in BALB/c mice. Green tea catechins were adsorbed on the pharyngeal mucosa for up to 60 min after GTE ingestion. The anti-IAV activity of GTE was dose dependent (p

Green tea (Camellia sinensis) for the prevention of cancer.

This review is an update of a previously published review in the Cochrane Database of Systematic Reviews (2009, Issue 3).Tea is one of the most commonly consumed beverages worldwide. Teas from the plant Camellia sinensis can be grouped into green, black and oolong tea, and drinking habits vary cross-culturally. C sinensis contains polyphenols, one subgroup being catechins. Catechins are powerful antioxidants, and laboratory studies have suggested that these compounds may inhibit cancer cell proliferation. Some experimental and nonexperimental epidemiological studies have suggested that green tea may have cancer-preventative effects. To assess possible associations between green tea consumption and the risk of cancer incidence and mortality as primary outcomes, and safety data and quality of life as secondary outcomes. We searched eligible studies up to January 2019 in CENTRAL, MEDLINE, Embase, ClinicalTrials.gov, and reference lists of previous reviews and included studies. We included all epidemiological studies, experimental (i.e. randomised controlled trials (RCTs)) and nonexperimental (non-randomised studies, i.e. observational studies with both cohort and case-control design) that investigated the association of green tea consumption with cancer risk or quality of life, or both. Two or more review authors independently applied the study criteria, extracted data and assessed methodological quality of studies. We summarised the results according to diagnosis of cancer type. In this review update, we included in total 142 completed studies (11 experimental and 131 nonexperimental) and two ongoing studies. This is an additional 10 experimental and 85 nonexperimental studies from those included in the previous version of the review. Eleven experimental studies allocated a total of 1795 participants to either green tea extract or placebo, all demonstrating an overall high methodological quality based on 'Risk of bias' assessment. For incident prostate cancer, the summary risk ratio (RR) in the green tea-supplemented participants was 0.50 (95% confidence interval (CI) 0.18 to 1.36), based on three studies and involving 201 participants (low-certainty evidence). The summary RR for gynaecological cancer was 1.50 (95% CI 0.41 to 5.48; 2 studies, 1157 participants; low-certainty evidence). No evidence of effect of non-melanoma skin cancer emerged (summary RR 1.00, 95% CI 0.06 to 15.92; 1 study, 1075 participants; low-certainty evidence). In addition, adverse effects of green tea extract intake were reported, including gastrointestinal disorders, elevation of liver enzymes, and, more rarely, insomnia, raised blood pressure and skin/subcutaneous reactions. Consumption of green tea extracts induced a slight improvement in quality of life, compared with placebo, based on three experimental studies. In nonexperimental studies, we included over 1,100,000 participants from 46 cohort studies and 85 case-control studies, which were on average of intermediate to high methodological quality based on Newcastle-Ottawa Scale 'Risk of bias' assessment. When comparing the highest intake of green tea with the lowest, we found a lower overall cancer incidence (summary RR 0.83, 95% CI 0.65 to 1.07), based on three studies, involving 52,479 participants (low-certainty evidence). Conversely, we found no association between green tea consumption and cancer-related mortality (summary RR 0.99, 95% CI 0.91 to 1.07), based on eight studies and 504,366 participants (low-certainty evidence). For most of the site-specific cancers we observed a decreased RR in the highest category of green tea consumption compared with the lowest one. After stratifying the analysis according to study design, we found strongly conflicting results for some cancer sites: oesophageal, prostate and urinary tract cancer, and leukaemia showed an increased RR in cohort studies and a decreased RR or no difference in case-control studies. Overall, findings from experimental and nonexperimental epidemiological studies yielded inconsistent results, thus providing limited evidence for the beneficial effect of green tea consumption on the overall risk of cancer or on specific cancer sites. Some evidence of a beneficial effect of green tea at some cancer sites emerged from the RCTs and from case-control studies, but their methodological limitations, such as the low number and size of the studies, and the inconsistencies with the results of cohort studies, limit the interpretability of the RR estimates. The studies also indicated the occurrence of several side effects associated with high intakes of green tea. In addition, the majority of included studies were carried out in Asian populations characterised by a high intake of green tea, thus limiting the generalisability of the findings to other populations. Well conducted and adequately powered RCTs would be needed to draw conclusions on the possible beneficial effects of green tea consumption on cancer risk.

Effect of Acute Ingestion of Green Tea Extract and Lemon Juice on Oxidative Stress and Lipid Profile in Pigs Fed a High-Fat Diet.

Green tea and its catechins have been shown to ameliorate high fat diet-induced oxidative stress and hyperlipidemia. However, low bioavailability of catechins limits their therapeutic potential. Lemon juice (LJ) has been suggested to enhance the bioavailability of catechins in vitro. This study investigated the antioxidative and hypolipidemic efficacy of a single dose of green tea extract (GTE) or GTE plus LJ (GTE + LJ) in high-fat diet fed pigs. Sixteen pigs ingested a single dose of GTE (190 mg/kg/day) or GTE + LJ (0.75 mL/kg/day) mixed with low-fat (LF; 5% fat) or high-fat (HF; 22% fat) diets and blood samples were collected for 24 h. Plasma catechin level peaked at two hours, and gradually returned to baseline after six hours following the intake. The addition of LJ significantly increased plasma catechin level. The diet containing GTE did not lower plasma cholesterol and triacylglycerol (TG) concentrations, superoxide dismutase (SOD) and catalase activity, or malondialdehyde concentration in 24 h in HF-fed pigs. Addition of a single dose of LJ, however, significantly decreased plasma TG level in LF groups but did not cause further changes on any other markers compared to the GTE alone. Our findings indicate limited effect of a single meal containing GTE on plasma antioxidant enzymes, lipid profile, and lipid peroxidation in pigs and no significant synergistic/additive action of adding LJ to GTE within 24 h in pigs. A study with a longer treatment period is warranted to further understand the potential role of GTE in reducing HF diet-induced oxidative stress and the possible synergistic role of LJ.

Aerobic Training and Green Tea Extract Protect against N-methyl-N-nitrosourea-induced Prostate Cancer.

Aerobic training and green tea extract can be used to reduce the risk of prostate cancer. The goal of this study was to evaluate the effects of 8-wk aerobic exercise training and administration of green tea extract on the level of nuclear factor kappa B (NF-kB), cyclooxygenase-2 (COX-2) and p53 tumor suppressor protein (p53) in prostate of rats which were stimulated by N-methyl-N-nitrosourea to induce the prostate cancer. Sixty adult male Wistar rats were assigned into six groups including healthy control, cancer control (CCt), cancer training (CTr: 45 min·d at low to moderate intensity, five times per week, 8 wk), cancer extract (CEx: 1.34 mL of green tea extract, three times per week, 8 wk), cancer training+ cancer extract (CTr + CEx) and sham groups. Rats were sacrificed 48 h after the last intervention session, and the prostate tissue was isolated to measure the levels of NF-kB, COX-2, and p53. The NF-kB level in CCt group was increased significantly compared to the healthy control (P = 0.02). In the CTr group, NF-kB level was decreased significantly compared to the CCt and CEx groups (P = 0.001 and 0.05, respectively). In addition, the levels of P53 protein were reduced in CTr, CEx, and CTr + CEx groups compared to CCt group (P = 0.001, 0.02 and 0.004, respectively). No significant changes were found in the level of COX-2 between groups. These results suggest that a long-term exercise training combined with the intake of green tea extract may reduce levels of NF-kB and p53 in rats with prostate cancer. Given the importance of recognizing complementary therapies in this regard, future studies are warranted.

Undesirable impact on structure and stability of insulin on addition of (+)-catechin hydrate with sugar

Insulin (In) based formulation has been used over decades for the cure of In-dependent diabetic patients, however, more attempts are still required to improve the remedial use of In. In this regard, the use of green tea has become widespread nowadays. However, it is unknown that (+)-catechin hydrate (CAT), a major component of green tea which enhances anti-diabetic activity of In, will or will not enhance the structure and stability of In if ingested with sugars. Interestingly, by using biophysical techniques, present study reveals the fact that the use of sugar during the intake of green tea extract may produce unwanted effects on In which may further lead to some disorders associated with In stability and also create obstacle in successful implications of In formulations.

Maternal green tea polyphenol intake during lactation attenuates kidney injury in high-fat-diet-fed male offspring programmed by maternal protein restriction in rats

Maternal malnutrition is known to increase the risk of obesity in offspring. We investigated whether green tea extract (GTE) intake during lactation affects obesity-related fibrosis and inflammation in the kidney of high-fat-diet-fed adult offspring of protein-restricted-diet-fed dams during pregnancy and lactation. Pregnant Wistar rats received diets containing 20% (normal-protein, NP) or 8% (low-protein, LP) casein, and they received 0%-, 0.12%- or 0.24%-GTE-containing LP diets (LP/LP, LP/LGT and LP/HGT, respectively) during lactation. At weaning, the pups that received a diet providing 13% (normal-fat, NF) or 45% (high-fat, HF) energy from fat were divided into five groups: NP/NP/NF, LP/LP/NF, LP/LP/HF, LP/LGT/HF and LP/HGT/HF. At week 45, the degree of fibrosis; macrophage infiltration; protein expression levels of TGF-β; and mRNA levels of TNF-α, DNMT, UHRF1 and histone lysine methyltransferase (G9a) in the kidneys of male offspring were examined. The area of fibrosis and TGF-βlevels increased in the LP/LP/HF group. Conversely, the fibrotic areas and TGF-β levels in the LP/HGT/HF group decreased (33% and 31%, respectively) compared with those in the LP/LP/HF group. The number of macrophages and mRNA levels of TNF-α in the LP/HGT/HF group decreased (34% and 29%, respectively) compared with those in the LP/LP/HF group. DNMT1, UHRF1 and G9a mRNA levels in the LP/HGT/HF group decreased compared with those in the LP/LP/HF group. In conclusion, GTE intake during lactation attenuated tubulointerstitial fibrosis and macrophage infiltration by down-regulating epigenetic modulators such as DNMT1, UHRF1 and G9a in the kidney of HF-diet-fed adult offspring programmed by maternal protein restriction.

Effect of subchronic intake of green tea extract on liver of albino rat histomorphometric, ultrastructural and biochemical study.

There are conflicting reports on the effect of green tea extract (GTE) on the liver of animals. Some studies failed to show any adverse hepatic effects following administration of GTE to mice, rats, and dogs. Others reported severe hepatic necrosis, resulting in death in female Swiss-Webster mice following its administration. The aim of the study was to examine the subchronic toxicity of GTE on the liver of the adult male albino rats. Forty male adult Wistar albino rats were used in the study. The rats were divided into four groups; group I (control), group II (low-dose green tea), group III (medium-dose green tea) and group IV (high-dose green tea). Histological, biochemical and histomorphometric analyses were done. Mild hepatic affections were observed in group II. The affections were severe in groups III and IV. The central veins and hepatic sinusoids were congested. The hepatocytes were degenerated. Hypertrophy of the hepatic arteries, dilation of the bile ducts and cellular infiltration were clearly observed in the last two groups. Mild degenerative changes were observed in the hepatocytes in rat's group II; the cytoplasm was rarefied and vacuolated. Some mitochondria were ruptured. The blood sinusoids were congested. The rough endoplasmic retinaculum was fragmented in group III. More degenerative changes were observed in group IV; the hepatic architectures were lost with disruption of cell membranes. Most of the cell organelles were degenerated and most of mitochondria were ballooned. As compared to that of the control groups: the total serum protein values in groups II, III and IV showed a statistically significant decrease (12%, 20% and 21%, respectively), the mean area per cent of collagen fibres in groups III and IV increased 5 and 7 folds. Subchronic administration of GTE resulted in structural and functional affection of the rats' liver. The dose of 250 mg/kg/day seemed to be safe, while the doses of 500 mg/kg/day and 1000 mg/kg/day had deleterious effect being more evident in the latter dose.

Long-Term Intake of Green Tea Extract Causes Mal-Conformation of Trabecular Bone Microarchitecture in Growing Rats.

The purpose of this study was to examine the effects of green tea extract (GTE) intake on bone structural and physiological properties, such as bone mass, trabecular bone microarchitecture, cortical bone geometry, and bone mechanical strength, in growing rats. Four-week-old male Wistar rats were divided into the following four groups: standard diet feeding for 85days (S-CON) or 170days (L-CON), and GTE diet feeding for 85days (S-GTE) or 170days (L-GTE). At the end of the experiment, in addition to measurement of circulating bone formation/resorption markers, bone mass, trabecular bone microarchitecture, and cortical bone geometry were analyzed in the left femur, and bone mechanical strength of the right femur was measured. There was no difference in all bone parameters between the S-CON and S-GTE groups. On the other hand, the L-GTE group showed the decrease in some trabecular bone mass/microarchitecture parameters and no change in cortical bone mass/geometry parameters compared with the L-CON group, and consequently the reduction in bone weight corrected by body weight. There was no difference in bone formation/resorption markers and bone mechanical strength between the S-CON and S-GTE groups and also between the L-CON and L-GTE groups. However, serum leptin levels were significantly lower in the L-GTE group than in the L-CON group. Thus, the long-term GTE intake had negative effects on bone, especially trabecular bone loss and microarchitecture mal-conformation, in growing rats.

The Combined Effect of Short Term Green Tea Extract and a Single Bout of Cycle Ergometer on Glycerol and Free Fat Acid of Trained Males

: It seems that shortly after green tea extract (GTE) ingestion, fat oxidation increases as well as exercise training. The purpose of this study was to investigate the combined effect of short term GTE and a single bout of cycle ergometer upon post-exercise fat oxidation. Sixteen healthy volunteer males were recruited to participate in the study. They were divided to two groups; experimental group (n = 8) and placebo group (n = 8), respectively. They consumed three GTE or placebo capsules a day before and one capsule 90 minutes before a cycling protocol. Blood samples were collected from all participants before and after the protocol. Based on the current results, fat oxidation in the experimental group increased markedly during post-exercise period compared to the placebo group. Plasma glycerol levels of the experimental group were significantly higher after GTE consumption during the post-exercise period compared to placebo. Compared to placebo, plasma free acids of the experimental group increased significantly after GTE consumption as well as acute GTE. Therefore, it seems that acute GTE ingestion could increase fat oxidation after post exercise conditions.

Effect of Green Tea Extract on Exercise-Induced Oxidative Stress in Obese Men: A Randomized, Double-Blind, Placebo-Controlled, Crossover Study

Background: Green tea contains polyphenol catechins that has been shown to be beneficial to health owing to its antioxidant properties. Objectives: This study investigated the effects of a 14-day ingestion of green tea extract (GTE) on biomarkers of oxidative stress in obese men undergoing resistance exercise (RE). Methods: In a randomized, double-blind, placebo (PL)-controlled, crossover study, ten obese men (age 37.12 ± 5.66 y; height 177 ± 7.7 cm; BMI 32.53 ± 2.52) performed two RE protocols consisting of 3 sets of 6 exercises to exhaustion at 75% of one repetition maximum (1RM) and 2 minute rests between sets, after 14 days of 500 mg of GTE (two capsules per day) or 500 mg PL (two capsules per day) supplementation. Blood samples were collected before (PRE) and immediately after (POST) RE and analyzed for oxidative biomarkers including lipid peroxidation (8-iso PGF2α) and oxidative DNA damage (8-OHdG). Results: Our results showed that a 14-day GTE supplementation did not change lipid peroxidation (P > 0.05); also, no significant alterations for 8-iso PGF2α between GTE and PL treatments after RE were observed (P > 0.05). However, 14-day GTE supplementation significantly reduced oxidative DNA damage as measured by 8-OHdG after RE compared to PL (P < 0.05). Conclusions: The results of this study demonstrated that 14-day supplementation of GTE significantly prevented oxidative DNA damage induced by RE in untrained obese men. However, the potential effects of GTE on oxidative stress after RE in obese people warrants further investigation.

An Appraisal of Drug-Drug Interactions with Green Tea (Camellia sinensis)

This review summarizes published in vitro, animal, and clinical studies investigating the effects of green tea (Camellia sinensis) extract and associated catechins on drug-metabolizing enzymes and drug transporters. In vitro studies suggest that green tea extract and its main catechin, (-)-epigallocatechin-3-gallate, to varying degrees, inhibit the activity of CYP1A1, CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2D6, and CYP3A4. UGT1A1 and UGT1A4 isoforms were also inhibited by (-)-epigallocatechin-3-gallate. Animal studies suggest green tea extract and/or (-)-epigallocatechin-3-gallate significantly increase the bioavailability of diltazem, verapamil, tamoxifen simvastatin, 5-fluorouracil, and nicardipine. Conversely, green tea extract and/or (-)-epigallocatechin-3-gallate reduce the bioavailability of quetiapine, sunitinib, clozapine, and nadolol. Of the few clinical studies available for review, it appears neither green tea extract nor (-)-epigallocatechin-3-gallate inhibit any major cytochrome P450 enzyme. Regarding drug transporters, in vitro studies indicate P-glycoprotein, organic anion transporting polypeptide 1A1, organic anion transporting polypeptide 1B1, organic anion transporting polypeptide 1B3, organic anion transporting polypeptide 2B1, organic cation transporter 1, organic cation transporter 2, multidrug and toxin extrusion 1, and multidrug and toxin extrusion 2-K are potentially inhibited by green tea extract. A clinical study indicates the organic anion transporting polypeptide 1A1 transporter is inhibited by (-)-epigallocatechin-3-gallate while P-glycoprotein is unaffected. In conclusion, the ingestion of green tea extract or its associated catechins is not expected to result in clinically significant influences on major cytochrome P450 or uridine 5'-diphospho-glucuronosyltransferase enzyme substrates or drugs serving as substrates of P-glycoprotein. However, some caution is advised in the consumption of significant amounts of green tea beverages or green tea extract in patients prescribed known substrates of organic anion transporting polypeptide, particularly those with a narrow therapeutic index.