Beneficial effects of green tea: a literature review

The relationship between phenolic compounds from diet and microbiota: impact on human health

The human intestinal tract is home to a complex microbial community called microbiota.

Synthesis, characterization, and adsorption properties of ionic liquid-modified hypercrosslinked polystyrene resins

Ionic liquid modified hypercrosslinked polymeric resins were synthesized and their adsorptive characteristics for catechin were studied.

Quercetin-rich onion peel extract suppresses adipogenesis by down-regulating adipogenic transcription factors and gene expression in 3T3-L1 adipocytes

BACKGROUND

Onion peel contains a high amount of quercetin, which has been reported to have anti-cholesterol, antithrombotic and insulin-sensitizing properties. This study aimed to elucidate the anti-adipogenic effects of quercetin-rich onion peel extract (OPE) and to compare it with commercially available quercetin using 3T3-L1 preadipocytes.

RESULTS

Without affecting cell viability, both OPE and quercetin averted adipogenesis, as characterized by dose-dependent decreases in intracellular triglyceride content and glycerol 3-phosphate dehydrogenase activity, but the effect was more pronounced with OPE than with quercetin. The mRNA expression levels of key adipogenic genes such as PPARγ, C/EBPα, FABP4, aP2 and LPL were decreased in a dose-dependent manner by both OPE and quercetin.

CONCLUSION

The results indicate that OPE treatment significantly prevents intracellular lipid accumulation via hyperactivation of genes regulating lipolysis as compared with quercetin alone.

Green tea consumption affects cognitive dysfunction in the elderly: a pilot study

Green tea is known to have various health benefits for humans. However, the effect of green tea consumption on cognitive dysfunction remains to be clinically verified. We conducted a clinical study to investigate the effects of green tea consumption on cognitive dysfunction. Twelve elderly nursing home residents with cognitive dysfunction (Mini-Mental State Examination Japanese version (MMSE-J) score: <28) participated in the study (2 men, 10 women; mean age, 88 years). The participants consumed green tea powder 2 g/day for 3 months. After three months of green tea consumption, the participants’ MMSE-J scores were significantly improved (before, 15.3 ± 7.7; after, 17.0 ± 8.2; p = 0.03). This result suggests that green tea consumption may be effective in improving cognitive function or reducing the progression of cognitive dysfunction; however, long-term large-scale controlled studies are needed to further clarify the effect.

The Effect of Ginkgo biloba and Camellia sinensis Extracts on Psychological State and Glycemic Control in Patients with Type 2 Diabetes Mellitus

Interest in finding natural antioxidants for use in food or medical materials to prevent free radical imbalance has increased considerably over the past years. The aim of this research was to evaluate changes in glycemic control and psychological state of patients with type 2 diabetes mellitus (T2DM) after use of antioxidant plant preparations. Fifty-six patients with T2DM were randomly allocated to receive standardized Ginkgo biloba L. leaves dry extract, green tea dry extract, or placebo capsules. Diabetes glycemic control measured as glycated hemoglobin (HbA1c) level, antioxidant state and psychological data were evaluated at baseline, after 9 and 18 months of using either antioxidant preparations or placebo. The level of perceived stress lowered significantly after 9 months ( p=0.038) and 18 months ( p=0.030), and the psychological aspect of quality of life significantly improved after 18 months ( p=0.019) of use of G. biloba extract. No significant differences were detected after using green tea extract. In patients using placebo, significant lowering of HbA1c level was observed after 18 months ( p=0.017). In conclusion, antioxidant G. biloba leaf extract exhibited a mild effect on psychological state and a trend of improving glycemic control in patients with type 2 diabetes mellitus.

Phytochemicals perturb membranes and promiscuously alter protein function

A wide variety of phytochemicals are consumed for their perceived health benefits. Many of these phytochemicals have been found to alter numerous cell functions, but the mechanisms underlying their biological activity tend to be poorly understood. Phenolic phytochemicals are particularly promiscuous modifiers of membrane protein function, suggesting that some of their actions may be due to a common, membrane bilayer-mediated mechanism. To test whether bilayer perturbation may underlie this diversity of actions, we examined five bioactive phenols reported to have medicinal value: capsaicin from chili peppers, curcumin from turmeric, EGCG from green tea, genistein from soybeans, and resveratrol from grapes. We find that each of these widely consumed phytochemicals alters lipid bilayer properties and the function of diverse membrane proteins. Molecular dynamics simulations show that these phytochemicals modify bilayer properties by localizing to the bilayer/solution interface. Bilayer-modifying propensity was verified using a gramicidin-based assay, and indiscriminate modulation of membrane protein function was demonstrated using four proteins: membrane-anchored metalloproteases, mechanosensitive ion channels, and voltage-dependent potassium and sodium channels. Each protein exhibited similar responses to multiple phytochemicals, consistent with a common, bilayer-mediated mechanism. Our results suggest that many effects of amphiphilic phytochemicals are due to cell membrane perturbations, rather than specific protein binding.

Concentrated green tea extract induces severe acute hepatitis in a 63-year-old woman--a case report with pharmaceutical analysis

ETNOPHARMACOLOGICAL RELEVANCE: The popularity of concentrated green tea extracts as dietary supplements for a wide range of applications is increasing due to their health-promoting effects attributed to the high amounts of catechins they contain. The most important of the green tea catechins is (-)-epigallocatechin-3-O-gallate (EGCG). While their beneficiary effects have been studied extensively, a small number of adverse events have been reported in the medical literature. Here we present a typical reversible course of severe hepatitis after green tea consumption.

MATERIALS AND METHODS

The case study describes in a 63-year old woman during treatment with green tea-capsules upon recommendation of a cancer support group.

RESULTS

The histological finding was consistent with drug induced hepatitis, and other possible causes of hepatitis were excluded. According to the CIOMS/RUCAM score the causality was assessed as "probable". After discontinuation of medication, followed by extracorporal albumin dialysis, rapid and sustained recovery occurred. Pharmaceutically analysis (HPLC) of the green tea capsules did not give evidence for contaminants but revealed the two typical compounds of green tea, namely (-)-epigallocatechin-3-O-gallate (EGCG, 93.2%) and epicatechin (EC, 6.8%) at a very high dose level.

CONCLUSION

The present case highlights the fact that such concentrated herbal extracts from green tea may not be free of adverse effects under certain circumstances. There is still a lack of a uniform European Union-wide surveillance system for adverse drug reactions of herbal products. Therefore this case underlines the importance of public awareness in the potential risks in use of herbal products.

Antioxidant effects of Camellia sinensis L. extract in patients with type 2 diabetes

The prevalence of diabetes mellitus (DM) has dramatically increased in the past decade. Furthermore, increasing evidence from research shows that oxidative stress (OS) plays a crucial role in the pathogenesis of diabetes and in its complications. A search for ways to reduce oxidative damage has become the focus of interest for the majority of scientists. In this study, we determined the radical scavenging activity of single green tea constituents by using an on-line high performance liquid chromatography (HPLC)-2,2-diphenyl-1-picrylhydrazyl (DPPH) method and evaluated the antioxidant effects on type 2 diabetic patients by performing a double-blind, placebo-controlled study. Epigallocatechin gallate was identified as the most potent antioxidant, contributing approximately 50% of the total antioxidant capacity of green tea extract. We also found a statistically significant decrement of lipid peroxidation markers in patients treated with green tea extract after 9 months or after 18 months of follow-up. Overall, these findings are attractive for diabetic patients, helping them to keep a high level of performance and well-being, which ultimately may delay the time of disability and reduce mortality.

Pro-oxidative and antioxidative controls and signaling modification of polyphenolic phytochemicals: contribution to health promotion and disease prevention?

Polyphenolic phytochemicals (PPs) have been extensively studied as potential nutriceuticals for maintenance of health and treatment of cancer, inflammation, and neurodegeneration. However, the reported beneficial outcomes are inconsistent. The biological activities of PPs have been attributed to their pro-oxidative and antioxidative actions and effects on signaling mechanisms and epigenomic modifications. These diversified properties were described or postulated on the basis of a variety of experimental studies using cell culture and animal models, even though most have not been replicated and results are not validated. This review attempts to give an overview of biological properties of PPs, based on the coherent results from relevant studies, and evaluate critically the experimental conditions and possible artifacts. Complicated molecular mechanisms and multitargeting genomic interactions of PPs are discussed, with a view that reasonable mechanistic propositions are usually obtained from well-designed in vivo studies.

Double-blinded, randomized, placebo-controlled study to evaluate the effectiveness of green tea in preventing acute gastrointestinal complications due to radiotherapy

BACKGROUND

Radiation-induced discomfort is frequently observed during pelvic radiotherapy. This study was performed to determine the effect of a green tea tablet to reduce the incidence of radiation-induced diarrhea and vomiting in patients with abdomen and pelvic malignancy.

MATERIALS AND METHODS

This randomized controlled clinical trial recruited 42 patients with abdomen and pelvic malignancy considered for treatment with 50 Gy radiotherapy, randomly assigned to the green tea tablet 450 mg (n = 21) or placebo group (n = 21) for 5 weeks. Acute gastrointesinal complications (Diarrhea and vomiting) were weekly assessed using Common Toxicity Criteria of the National Cancer Institute version 3.0 and functional living index emesis, respectively. Two-sample t-tests, Pearson's Chi-square, Mann-Whitney U-test, and Friedman were used for analysis.

RESULTS

There was a significant difference in frequency of reported diarrhea between two groups of study at the end of study (P < 0.002). About 81% of patients in green tea group reported no history of diarrhea at week 5. The treatment group have reported no history of severe diarrhea during radiotherapy. There was no significant difference between two groups of study in frequency of vomiting throughout the study, but 9.5% of cases in placebo group showed severe vomiting.

CONCLUSION

Green tea contains a high concentration of catechins could be effective in decreasing the frequency and severity of radiotherapy induced diarrhea. Green tea (450 mg/day) could be considered to be a safe for prevention diarrhea and vomiting in patients undergoing pelvic or abdomen radiotherapy.

ABCG5 gene responses to treadmill running with or without administration of Pistachio atlantica in female rats

OBJECTIVE(S)

ABC transporters comprise a large family of transmembrane proteins that use the energy provided by ATP hydrolysis to translocate a variety of substrates across biological membranes. All members of the human ABCG subfamily, except for ABCG2, are cholesterol-transporter. The aim of this study was to determine the liver, the small intestine and kidney ABCG5 relative gene expression in response to treadmill-running training in female rats.

MATERIALS AND METHODS

Twenty Wistar rats (6-8 weeks old and 125-135 g weight) were used. Animals were randomly assigned to saline-control (SC), saline-training (ST), and Baneh-control (BC), and Baneh-training (BT) groups. Training groups did the exercise on a motor-driven treadmill at 25 m/min (0% grade) for 60 min/day for eight weeks (5 days/week). Rats were fed orally, with Baneh extraction and saline for six weeks. The two-way ANOVA was employed for statistical analysis. ABCG5 relative gene expression was detected by Real-time PCR method.

RESULTS

The current findings indicate that the Baneh-treated tissues had significantly lower levels of ABCG5 gene expression in the liver, small intestine, and kidneys (P< 0.001, P< 0.003, P< 0.001, respectively), when compared with saline-treated tissues. However, a higher level of gene expression was observed in exercise groups. A lower level of HDL-c but not triglyceride (TG) and total cholesterol (TC) levels were found in Baneh-treated animals at rest.

CONCLUSION

Exercise training increases ABCG5 relative gene expression in the liver, small intestine and kidney tissues; therefore exercise training may adjust the reduction of ABCG5 relative gene expression in Baneh-training group.

Green tea decoction improves glucose tolerance and reduces weight gain of rats fed normal and high-fat diet

Green tea containing polyphenols exerts antidiabetic and antiobesity effects, but the mechanisms involved are not fully understood. In this study, we first analyzed and compared polyphenol compounds [epigallocatechin gallate (EGCG), epigallocatechin (EGC)] in decoction of green tea leaves versus usual green tea extracts. Second, the effects of acute (30 min) or chronic (6 weeks) oral administration of green tea decoction (GTD) on intestinal glucose absorption were studied in vitro in Ussing chamber, ex vivo using isolated jejunal loops and in vivo through glucose tolerance tests. Finally, we explore in rat model fed normal or high-fat diet the effects of GTD on body weight, blood parameters and on the relative expression of glucose transporters SGLT-1, GLUT2 and GLUT4. GTD cooked for 15 min contained the highest amounts of phenolic compounds. In fasted rats, acute administration of GTD inhibited SGLT-1 activity, increased GLUT2 activity and improved glucose tolerance. Similarly to GTD, acute administration of synthetic phenolic compounds (2/3 EGCG+1/3 EGC) inhibited SGLT-1 activity. Chronic administration of GTD in rat fed high-fat diet reduced body weight gain, circulating triglycerides and cholesterol and improved glucose tolerance. GTD-treated rats for 6 weeks display significantly reduced SGLT-1 and increased GLUT2 mRNA levels in the jejunum mucosa. Moreover, adipose tissue GLUT4 mRNA levels were increased. These results indicate that GTD, a traditional beverage rich in EGCG and EGC reduces intestinal SGLT-1/GLUT2 ratio, a hallmark of regulation of glucose absorption in enterocyte, and enhances adipose GLUT4 providing new insights in its possible role in the control of glucose homeostasis.

Effects of fermented rooibos (Aspalathus linearis) on adipocyte differentiation

Rooibos (Aspalathus linearis) contains a rich complement of polyphenols, including flavonoids, considered to be largely responsible for its health promoting effects, including combatting obesity. The purpose of this study was to examine the effect of fermented rooibos hot water soluble solids on in vitro adipocyte differentiation by using differentiating 3T3-L1 adipocytes. Hot water soluble solids were obtained when preparing an infusion of fermented rooibos at "cup-of-tea" strength. The major phenolic compounds (>5 mg/g) were isoorientin, orientin, quercetin-3-O-robinobioside and enolic phenylpyruvic acid-2-O-β-D-glucoside. Treatment of 3T3-L1 adipocytes with 10 μg/ml and 100 μg/ml of the rooibos soluble solids inhibited intracellular lipid accumulation by 22% (p<0.01) and 15% (p<0.05), respectively. Inhibition of adipogenesis was accompanied by decreased messenger RNA (mRNA) expression of PPARγ, PPARα, SREBF1 and FASN. Western blot analysis exhibited decreased PPARα, SREBF1 and AMPK protein expression. Impeded glycerol release into the culture medium was observed after rooibos treatment. None of the concentrations of rooibos hot water soluble solids was cytotoxic, in terms of ATP content. Interestingly, the higher concentration of hot water soluble solids increased ATP concentrations which were associated with increased basal glucose uptake. Decreased leptin secretion was observed after rooibos treatment. Our data show that hot water soluble solids from fermented rooibos inhibit adipogenesis and affect adipocyte metabolism, suggesting its potential in preventing obesity.

Green tea and one of its constituents, Epigallocatechine-3-gallate, are potent inhibitors of human 11β-hydroxysteroid dehydrogenase type 1

The microsomal enzyme 11β-hydroxysteroid deydrogenase type 1 (11β-HSD1) catalyzes the interconversion of glucocorticoid receptor-inert cortisone to receptor- active cortisol, thereby acting as an intracellular switch for regulating the access of glucocorticoid hormones to the glucocorticoid receptor. There is strong evidence for an important aetiological role of 11β-HSD1 in various metabolic disorders including insulin resistance, diabetes type 2, hypertension, dyslipidemia and obesity. Hence, modulation of 11β-HSD1 activity with selective inhibitors is being pursued as a new therapeutic approach for the treatment of the metabolic syndrome. Since tea has been associated with health benefits for thousands of years, we sought to elucidate the active principle in tea with regard to diabetes type 2 prevention. Several teas and tea specific polyphenolic compounds were tested for their possible inhibition of cortisone reduction with human liver microsomes and purified human 11β-HSD1. Indeed we found that tea extracts inhibited 11β-HSD1 mediated cortisone reduction, where green tea exhibited the highest inhibitory potency with an IC50 value of 3.749 mg dried tea leaves per ml. Consequently, major polyphenolic compounds from green tea, in particular catechins were tested with the same systems. (-)-Epigallocatechin gallate (EGCG) revealed the highest inhibition of 11β-HSD1 activity (reduction: IC50 = 57.99 µM; oxidation: IC50 = 131.2 µM). Detailed kinetic studies indicate a direct competition mode of EGCG, with substrate and/or cofactor binding. Inhibition constants of EGCG on cortisone reduction were Ki = 22.68 µM for microsomes and Ki = 18.74 µM for purified 11β-HSD1. In silicio docking studies support the view that EGCG binds directly to the active site of 11β-HSD1 by forming a hydrogen bond with Lys187 of the catalytic triade. Our study is the first to provide evidence that the health benefits of green tea and its polyphenolic compounds may be attributed to an inhibition of the cortisol producing enzyme 11β-HSD1.

Assessment of Bioautography and Spot Screening of TLC of Green Tea (Camellia) Plant Extracts as Antibacterial and Antioxidant Agents

This study was carried out as a prerequisite to evaluate the therapeutic potential of Camellia varieties. The crude extracts of six different plants of green tea Camellia assamica and Camellia sinensis were tested against three Gram-positive and four Gram-negative bacteria using agar disk diffusion method at 50 mg/ml concentration. 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and diphenyl-(2,4,6-trinitrophenyl)iminoazanium free radical scavenging methods were performed to evaluate the antioxidant potential. Phytochemical constituents and trace metals were detected through thin layer chromatography and Inductively Coupled Plasma Atomic Emission Spectrophotometer, respectively. The maximum inhibition of Staphylococcus aureus was recorded by dimethyl sulphoxide extracts of green tea varieties. The measured zone of inhibition of dimethyl sulphoxide extracts by Qimen was (10.00±0.0 mm), Japanese (10.00±0.0 mm), Turkish (10.00±0.0 mm), Indonesian (8.33±1.0 mm), P3 clone (10.00±0.0 mm) and Sri Lankan (10.00±0.0 mm). Maximum scavenging potential activity was found with ethanol, methanol and dimethyl sulphoxide extracts. Spot screening of TLC-developed plates indicated that the presence of active biological compounds such as flavonoids, proteins, phenols, alkaloids and glycosides also exhibited strong activity against tested bacterial strains. This study reveals the potential biological activities of Camellia assamica and Camellia sinensis having massive phytochemical constituents and trace elements.

Anticancer effects and molecular mechanisms of epigallocatechin-3-gallate

Epigallocatechin-3-gallate (EGCG) is a type of catechin found in green tea. EGCG exhibits a variety of activities, including anti-inflammatory, antidiabetes, antiobesity, and antitumor. In this review, we focus on the antitumor effects of EGCG. EGCG inhibits carcinogen activity, tumorigenesis, proliferation, and angiogenesis, and induces cell death. These effects are associated with modulation of reactive oxygen species (ROS) production. Although EGCG has a dual function of antioxidant and pro-oxidant potential, EGCG-mediated modulation of ROS production is reported to be responsible for its anticancer effects. The EGCG-mediated inhibition of nuclear factor-κB signaling is also associated with inhibition of migration, angiogenesis, and cell viability. Activation of mitogen-activated protein kinases activity upregulates the anticancer effect of EGCG on migration, invasion, and apoptosis. In addition, EGCG could also induce epigenetic modification by inhibition of DNA methyltransferase activity and regulation of acetylation on histone, leading to an upregulation of apoptosis. Although EGCG promotes strong anticancer effects by multiple mechanisms, further studies are needed to define the use of EGCG in clinical treatment.

The effects of green tea consumption on metabolic and anthropometric indices in patients with Type 2 diabetes

BACKGROUND

This study aims at investigating the possible effects of different daily doses of green tea (GT) intake for eight weeks on certain anthropometric, metabolic, and oxidative stress biomarkers of diabetic patients.

MATERIALS AND METHODS

This randomized clinical trial included 63 patients with type 2 diabetes (30 males and 33 females). After a two-week run-in period without green tea, they were randomly assigned into one of the three groups, with a different daily intake of green tea; four cups of green tea per day (n = 24), two cups of green tea per day (n = 25), and the control group (n = 14) with no green tea intake for two months. At baseline and after the intervention, blood tests, dietary, and anthropometric variables were assessed. The patients were instructed to maintain their usual dietary intake and normal physical activity.

RESULTS

Consumption of four cups of GT per day caused a significant decrease in body weight (73.2 to 71.9) (P < 0.001), body mass index (27.4 to 26.9) (P < 0.001), waist circumference (95.8 to 91.5) (P < 0.001), and systolic blood pressure (126.2 to 118.6) (P < 0.05) in this group. No significant change was seen in the other groups and between group comparisons. The metabolic and oxidative stress parameters did not show any significant differences within and between groups.

CONCLUSION

Drinking four cups of green tea led to a significant reduction in weight and systolic blood pressure.

A hypothesis on the relationship between tea drinking and sexual activity

As a major beverage in the world, the health benefits of drinking tea have been reported in numerous studies. The effects of green tea are mainly attributed to its polyphenol content, although caffeine, accounting for 2%-4%, appears to be related to the adaptation of mental energy by increasing alertness, attention and cognitive function, as well as elevating mood. L-Theanine, a unique amino acid in tea, has neuroprotective and mood effects. In addition, some studies on functional neuroanatomy and cerebral control of sexual function have demonstrated that the thalamus and hypothalamus play a role in emotional changes, memory and sexual behavior patterns. Our recent epidemiology research has unexpectedly found that tea drinking was positively related with sexual orgasm and sexual satisfaction in female hypertensive patients. We therefore hypothesize that long-term regular consumption of tea may play a role in sexual activity.

Dietary strategies to recover from exercise-induced muscle damage

Exhaustive or unaccustomed intense exercise can cause exercise-induced muscle damage (EIMD) and its undesirable consequences may decrease the ability to exercise and to adhere to a training programme. This review briefly summarises the muscle damage process, focusing predominantly on oxidative stress and inflammation as contributing factors, and describes how nutrition may be positively used to recover from EIMD. The combined intake of carbohydrates and proteins and the use of antioxidants and/or anti-inflammatory nutrients within physiological ranges are interventions that may assist the recovery process. Although the works studying food instead of nutritional supplements are very scarce, their results seem to indicate that food might be a favourable option as a recovery strategy. To date, the only tested foods were milk, cherries, blueberries and pomegranate with promising results. Other potential solutions are foods rich in protein, carbohydrates, antioxidants and/or anti-inflammatory nutrients.

Characterization of binding interactions of (-)-epigallocatechin-3-gallate from green tea and lipase

Understanding the interaction of (-)-epigallocatechin-3-gallate (EGCG) and lipase is important for understanding EGCG's inhibition of lipase. In this paper, the interaction of EGCG and porcine lipase was characterized by fluorescence spectroscopy, circular dichroism (CD), isothermal titration calorimetry, and molecular docking. EGCG might act as a noncompetitive pancreatic lipase inhibiter. EGCG bound to lipase with affinity of K(a) = 2.70 × 10⁴ L mol⁻¹. Thermodynamic features suggested that the interaction process was spontaneous, with hydrogen bonds and electrostatic force perhaps primarily responsible for the interaction, with 1:1 interaction of lipase and EGCG. CD studies indicated conformation change of lipase on binding to EGCG. Furthermore, docking results supported experimental findings and revealed hydrogen-bonding interaction with Val21, Glu188, and Glu220. This noncovalent bonding between EGCG and lipase alters the molecular conformation of lipase, which decreases the enzyme catalytic activity. This study will help further understand the antiobesity mechanisms of green tea.

Inhibition of microsomal cortisol production by (-)-epigallocatechin-3-gallate through a redox shift in the endoplasmic reticulum--a potential new target for treating obesity-related diseases

Conversion of cortisone to cortisol by 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) in the endoplasmic reticulum (ER) of the target cells is a major determinant of glucocorticoid action, and plays an important role in the development of obesity-related diseases. Inhibition of 11βHSD1 activity is, therefore, considered as a promising novel strategy for the treatment of metabolic syndrome and diabetes. Tea flavanols and their major representative, epigallocatechin gallate are known as antiobesity and antidiabetic agents. Their impacts on blood glucose level, hepatic glucose production, and insulin responsiveness resemble those observed on inhibition or depletion of 11βHSD1. We aimed to study the effect of epigallocatechin gallate on 11βHSD1 activity in ER-derived rat liver microsomes by measuring cortisone and cortisol with HPLC. Cortisol production was efficiently suppressed in a concentration dependent manner in intact microsomal vesicles. However, this effect was abolished by membrane permeabilization; and the three proteins involved in the overall process (11βHSD1, hexose 6-phosphate dehydrogenase, and glucose 6-phosphate transporter) were not or only mildly affected. Further investigation revealed the oxidation of luminal NADPH to NADP⁺, which attenuates cortisone reduction and favors cortisol oxidation in this compartment. Such a redox shift in the ER lumen might contribute to the beneficial health effects of tea flavanols and should be regarded as a promising strategy for the development of novel selective 11βHSD1 inhibitors to treat obesity-related diseases.

Green tea extract with polyethylene glycol-3350 reduces body weight and improves glucose tolerance in db/db and high-fat diet mice

Green tea extract (GTE) is regarded to be effective against obesity and type 2 diabetes, but definitive evidences have not been proven. Based on the assumption that the gallated catechins (GCs) in GTE attenuate intestinal glucose and lipid absorption, while enhancing insulin resistance when GCs are present in the circulation through inhibiting cellular glucose uptake in various tissues, this study attempted to block the intestinal absorption of GCs and prolong their residence time in the lumen. We then observed whether GTE containing the nonabsorbable GCs could ameliorate body weight (BW) gain and glucose intolerance in db/db and high-fat diet mice. Inhibition of the intestinal absorption of GCs was accomplished by co-administering the nontoxic polymer polyethylene glycol-3350 (PEG). C57BLKS/J db/db and high-fat diet C57BL/6 mice were treated for 4 weeks with drugs as follows: GTE, PEG, GTE+PEG, voglibose, or pioglitazone. GTE mixed with meals did not have any ameliorating effects on BW gain and glucose intolerance. However, the administration of GTE plus PEG significantly reduced BW gain, insulin resistance, and glucose intolerance, without affecting food intake and appetite. The effect was comparable to the effects of an α-glucosidase inhibitor and a peroxisome proliferator-activated receptor-γ/α agonist. These results indicate that prolonging the action of GCs of GTE in the intestinal lumen and blocking their entry into the circulation may allow GTE to be used as a prevention and treatment for both obesity and obesity-induced type 2 diabetes.

Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials

BACKGROUND

The results of studies investigating the effect of green tea on glucose control and insulin sensitivity in humans are inconsistent.

OBJECTIVE

We aimed to quantitatively evaluate the effect of green tea on glucose control and insulin sensitivity.

DESIGN

We performed a strategic literature search of PubMed, EMBASE, and the Cochrane Library (updated to January 2013) for randomized controlled trials that evaluated the effects of green tea and green tea extract on glucose control and insulin sensitivity. Study quality was assessed by using the Jadad scale. Weighted mean differences were calculated for net changes in glycemic measures by using fixed-effects or random-effects models. We conducted prespecified subgroup and sensitivity analyses to explore potential heterogeneity. Meta-regression analyses were conducted to investigate dose effects of green tea on fasting glucose and insulin concentrations.

RESULTS

Seventeen trials comprising a total of 1133 subjects were included in the current meta-analysis. Green tea consumption significantly reduced the fasting glucose and hemoglobin A1c (Hb A1c) concentrations by -0.09 mmol/L (95% CI: -0.15, -0.03 mmol/L; P < 0.01) and -0.30% (95% CI: -0.37, -0.22%; P < 0.01), respectively. Further stratified analyses from high Jadad score studies showed that green tea significantly reduced fasting insulin concentrations (-1.16 μIU/mL; 95% CI: -1.91, -0.40 μIU/mL; P = 0.03).

CONCLUSIONS

This meta-analysis suggested that green tea had favorable effects, ie, decreased fasting glucose and Hb A1c concentrations. Subgroup analyses showed a significant reduction in fasting insulin concentrations in trials with high Jadad scores.

Effectiveness of green tea mouthwash in postoperative pain control following surgical removal of impacted third molars: double blind randomized clinical trial

Background

Pain following surgical removal of impacted molars has remained an important concern among practitioners. Various protocols have been proposed to reduce postoperative pain. However, each one has special side effects and limitations. As green tea possesses anti-inflammatory and antibacterial properties, the aim of the current study was to evaluate the effectiveness of green tea mouthwash in controlling postoperative pain.

Materials and methods

In a study with split-mouth and double blind design, 44 patients in need of bilateral removal of impacted third molars underwent randomized surgical extraction; following one surgery patients rinsed with a green tea mouthwash from the first to seventh postoperative day and after other extraction rinsed with placebo mouthwash in the same duration. Both patients and surgeon were blinded to the type of mouthwash. The predictor variable was type of mouthwash and primary outcome variable was postoperative pain measured by visual analogue scale (VAS) during first week after surgery. In addition, number of analgesics patients used after surgery recorded. To measure the effect of green tea mouthwash, repeated measures test with confidence interval of 95% was performed.

Results

Total of 43 patients with mean age of 24 years underwent total of 86 surgeries. VAS value had no statistically difference prior rinsing among groups (P-value > 0.05). However, the mean value of VAS following rinsing with green tea was statistically lower than placebo in postoperative days of 3–7 (P-value < 0.05). In addition, while rinsing with green tea, patients took significantly lower number of analgesics after surgery (P-value < 0.05). No side effects reported.

Conclusion

Green tea mouthwash could be an appropriate and safe choice to control postoperative pain after third molar surgery.

Phenolic promiscuity in the cell nucleus--epigallocatechingallate (EGCG) and theaflavin-3,3'-digallate from green and black tea bind to model cell nuclear structures including histone proteins, double stranded DNA and telomeric quadruplex DNA

Flavanols from tea have been reported to accumulate in the cell nucleus in considerable concentrations. The nature of this phenomenon, which could provide novel approaches in understanding the well-known beneficial health effects of tea phenols, is investigated in this contribution. The interaction between epigallocatechin gallate (EGCG) from green tea and a selection of theaflavins from black tea with selected cell nuclear structures such as model histone proteins, double stranded DNA and quadruplex DNA was investigated using mass spectrometry, Circular Dichroism spectroscopy and fluorescent assays. The selected polyphenols were shown to display affinity to all of the selected cell nuclear structures, thereby demonstrating a degree of unexpected molecular promiscuity. Most interestingly theaflavin-digallate was shown to display the highest affinity to quadruplex DNA reported for any naturally occurring molecule reported so far. This finding has immediate implications in rationalising the chemopreventive effect of the tea beverage against cancer and possibly the role of tea phenolics as "life span essentials".

Beneficial effects of Gosha-jinki-gan and green tea extract in rats with chemical cystitis

The aim of this study was to characterize pharmacological effects of gosha-jinki-gan (GJG) and green tea extract (GTE), on urodynamic parameters, bladder receptors, and urinary cytokines in rats with cyclophosphamide (CYP)-induced cystitis. Urodynamic parameters in CYP-treated rats were measured using the cystometric method. Muscarinic and purinergic receptors in rat tissues were measured by radioreceptor assays. Urinary cytokine levels were measured with ELISA kits. GJG and GTE were orally administered to rats once a day for 7 days. The GJG treatment significantly ameliorated changes in urodynamic parameters in CYP-treated rats. Similar treatment with GTE slightly attenuated changes in urodynamic parameters. The maximal number of binding sites for [³H]NMS and [³H]αβ-MeATP in the bladder was significantly lower in CYP-treated rats than in sham rats. Such a reduction in receptor density was significantly attenuated by the GJG treatment. GTE treatment also significantly attenuated the down-regulation of muscarinic receptors, but not P2X receptors in bladders of rats with CYP-induced cystitis. The elevation in urinary cytokine levels in CYP-treated rats was effectively attenuated by GJG treatment. The elevation in cytokine levels in CYP-treated rats was alleviated by GTE treatment. In conclusion, GJG may be a pharmacologically useful plant extract for cystitis.

Effect of Dietary Cocoa Tea (Camellia ptilophylla) Supplementation on High-Fat Diet-Induced Obesity, Hepatic Steatosis, and Hyperlipidemia in Mice

Recent studies suggested that green tea has the potential to protect against diet-induced obesity. The presence of caffeine within green tea has caused limitations. Cocoa tea (Camellia ptilophylla) is a naturally decaffeinated tea plant. To determine whether cocoa tea supplementation results in an improvement in high-fat diet-induced obesity, hyperlipidemia and hepatic steatosis, and whether such effects would be comparable to those of green tea extract, we studied six groups (n = 10) of C57BL/6 mice that were fed with (1) normal chow (N); (2) high-fat diet (21% butterfat + 0.15% cholesterol, wt/wt) (HF); (3) a high-fat diet supplemented with 2% green tea extract (HFLG); (4) a high-fat diet supplemented with 4% green tea extract (HFHG); (5) a high-fat diet supplemented with 2% cocoa tea extract (HFLC); and (6) a high-fat diet supplemented with 4% cocoa tea extract (HFHC). From the results, 2% and 4% dietary cocoa tea supplementation caused a dose-dependent decrease in (a) body weight, (b) fat pad mass, (c) liver weight, (d) total liver lipid, (e) liver triglyceride and cholesterol, and (f) plasma lipids (triglyceride and cholesterol). These data indicate that dietary cocoa tea, being naturally decaffeinated, has a beneficial effect on high-fat diet-induced obesity, hepatomegaly, hepatic steatosis, and elevated plasma lipid levels in mice, which are comparable to green tea. The present findings have provided the proof of concept that dietary cocoa tea might be of therapeutic value and could therefore provide a safer and cost effective option for patients with diet-induced metabolic syndrome.

The relationship between the structure and biological actions of green tea catechins

Catechins and their gallate esters are a class of polyphenolic compounds. The catechin subclass known as flavan-3-ols have recently attracted much attention with regards to their beneficial effect on human health. Their biological actions are dependent on the structure of the compounds and vary according to cell type. They are best known as powerful antioxidants; however depending on the doses they also exhibit prooxidant effects. The anti- or prooxidant effects of green tea catechins have been implicated in the modulation of several cellular functions often associated with strong chemoprotective properties. This review summarises the benefit catechins to human health, the main molecular pathways modulated by catechins. The relationship between the structure and activity of the catechins needs to be studied further. In the future, the structure of catechins could be modified so as to synthesise novel compounds with more specific beneficial properties and higher bioavailability.

The effects of ErhBMP-2-/EGCG-coated BCP bone substitute on dehiscence around dental implants in dogs

OBJECTIVES

The purpose was to evaluate the effect of Escherichia coli-derived recombinant human bone morphogenetic protein-2 (ErhBMP-2)-/epigallocatechin-3-gallate (EGCG)-coated biphasic calcium phosphate (BCP) and titanium barrier membrane on dehiscence defects in dogs.

MATERIALS AND METHODS

In five mongrel dogs, the dehiscence bony defects around dental implants were surgically created and in total three implants were placed at edentulous ridge of which teeth had been extracted 12 weeks before. For the control group, BCP was applied to the dehiscence defect. For experimental groups, ErhBMP-2-coated BCP and ErhBMP-2-/EGCG-coated BCP were applied. The newly designed titanium barrier membrane was used to apply all the defects. The defects were evaluated histologically and histometrically after 12 weeks. The comparative statistics of the groups were obtained through Kruskal-Wallis test.

RESULTS

In bone-to-implant contact (BIC), bone density (BD), bone regeneration height (BRH), and bone mineralization apposition rate (BMAR), differences among groups were not found. ErhBMP-2/EGCG group appeared to have higher value. In fluorescence analysis, bone remodeling around graft material was more active in the ErhBMP-2/EGCG group.

CONCLUSION

Within the limit of this study, it is reasonable to assume that BMP-2-/EGCG-coated biphasic BCP and the newly designed titanium membrane were more beneficial in dehiscence defect healing with increased bone remodeling.

Effects of green tea consumption on human fecal microbiota with special reference to Bifidobacterium species

Green tea is one of the most popular beverages in the world. Its beneficial health effects and components have been extensively reviewed. However, little is known about the influence of green tea consumption on the human intestinal microbiota (HIM), which plays a crucial role in human health. Ten volunteers who did not usually consume green tea, drank it for 10 days and then stopped drinking it for 7 days. Their fecal samples were collected at three time points: before beginning the 10-day green-tea regime, at the conclusion of that 10 days, and 7 days after stopping the regime. Their fecal samples were analyzed by terminal restriction fragment length polymorphism with specific primer-restriction enzyme systems for HIM and by using a real-time PCR method for the Bifidobacterium species. Although the HIM of each subject was relatively stable, the proportion of Bifidobacterium species played an important role in the classification of their fecal microbiota. Although there were inter-individual differences in the Bifidobacterium species, an overall tendency for the proportion of bifidobacteria to increase because of green tea consumption was noted. However, little change was observed in the composition of Bifidobacterium species in each sample. This suggests that the change in proportion was induced, not by an inter-species transition, but by an intra-species increase and/or decrease. In conclusion, green tea consumption might act as a prebiotic and improve the colon environment by increasing the proportion of the Bifidobacterium species.

Influence of the green tea leaf extract on neurotoxicity of aluminium chloride in rats

Aluminium may have an important role in the aetiology/pathogenesis/precipitation of Alzheimer's disease. Because green tea (Camellia sinensis L.) reportedly has health-promoting effects in the central nervous system, we evaluated the effects of green tea leaf extract (GTLE) on aluminium chloride (AlCl3 ) neurotoxicity in rats. All solutions were injected into the cornu ammonis region 1 hippocampal region. We measured the performance of active avoidance (AA) tasks, various enzyme activities and total glutathione content (TGC) in the forebrain cortex (FbC), striatum, basal forebrain (BFb), hippocampus, brain stem and cerebellum. AlCl3 markedly reduced AA performance and activities of cytochrome c oxidase (COX) and acetylcholinesterase (AChE) in all regions. It decreased TGC in the FbC, striatum, BFb, hippocampus, brain stem and cerebellum, and increased superoxide dismutase activity in the FbC, cerebellum and BFb. GTLE pretreatment completely reversed the damaging effects of AlCl3 on AA and superoxide dismutase activity, markedly corrected COX and AChE activities, and moderately improved TGC. GTLE alone increased COX and AChE activities in almost all regions. GTLE reduces AlCl3 neurotoxicity probably via antioxidative effects and improves mitochondrial and cholinergic synaptic functions through the actions of (-)-epigallocatechin gallate and (-)-epicatechin, compounds most abundantly found in GTLE. Our results suggest that green tea might be beneficial in Alzheimer's disease.

Factors associated with low bone density among women with major depressive disorder

OBJECTIVE

Previous studies have suggested that depression might be associated with low bone mineral density (BMD) in women with depression. The aim of this study was to investigate the association between the BMD of women with major depressive disorder and correlated factors.

METHOD

This prospective cross-sectional study explored the association between bone density and major depressive disorder in women. One hundred women diagnosed with major depressive disorder were enrolled. The diagnoses were made by board-certificated psychiatrists using the Mini International Neuropsychiatric Interview (MINI). The Beck Depression Inventory (BDI) was administered. The bone density of the hip was measured with dual X-ray densitometry (DEXA) using a Hologic Delphi QDR-2000 densitometer.

RESULTS

We found age, family history of osteoporosis, consumption of coffee, and consumption of tea to be associated with low BMD in single-variate analysis. Depression was also related to BMD, in that the worse the depression, the lower the BMD. Multi-variate analysis by linear regression revealed an equation of BMD = 0.91 - 0.004 x (severity of depression) + 0.07 x (tea consumption)--0.06 x (family history of osteoporosis)--0.04 x age.

CONCLUSION

These results suggest that depression is associated with lower BMD, and the associated factors should be considered in depressive women. The findings of this research may be useful for improving the care of women with major depressive disorder in terms of developing appropriate and effective care plans.

Guaraná (Paullinia cupana Kunth) effects on LDL oxidation in elderly people: an in vitro and in vivo study

Background

Previous experimental investigations have suggested that guaraná (Paullinia cupana Kunth, supplied by EMBRAPA Oriental) consumption is associated with a lower prevalence of cardiovascular metabolic diseases and has positive effects on lipid metabolism, mainly related to low density lipoprotein (LDL) levels. As LDL oxidation is an important initial event in the development of atherosclerosis, we performed in vitro and in vivo studies to observe the potential effects of guaraná on LDL and serum oxidation.

Methods

The in vivo protocol was performed using blood samples from 42 healthy elderly subjects who habitually ingested guaraná (GI) or never ingested guaraná (NG). The formation of conjugated dienes (CDs) was analyzed from serum samples. The in vitro protocols were performed using LDL obtained from 3 healthy, non-fasted, normolipidemic voluntary donors who did not habitually ingest guaraná in their diets. The LDL samples were exposed to 5 different guaraná concentrations (0.05, 0.1, 0.5, 1, and 5 μg/mL).

Results

GI subjects demonstrated lower LDL oxidation than did NG subjects (reduction of 27%, p < 0.0014), independent of other variables. In the GI group the total polyphenols was positively associated with LDL levels. Also, guaraná demonstrated a high antioxidant activity in vitro, mainly at concentrations of 1 and 5 μg/mL, demonstrated by suppression of CDs and TBARS productions, tryptophan destruction and high TRAP activity.

Conclusions

Guaraná, similar to other foods rich in caffeine and catechins such as green tea, has some effect on LDL oxidation that could partially explain the protective effects of this food in cardiometabolic diseases.

Inhibitory activity of green tea (Camellia sinensis) extract on some clinically isolated cariogenic and periodontopathic bacteria

OBJECTIVE

To determine the in vitro inhibitory activity of green tea extract on some clinically isolated cariogenic and periodontopathic bacteria.

MATERIALS AND METHODS

Twenty strains of each of Streptococcusmutans, Aggregatibacteractinomycetemcomitans, Porphyromonasgingivalis, and Prevotellaintermedia were isolated from carious teeth and periodontal pockets of patients with dental caries and periodontal diseases. Green tea extract was prepared by aqueous extraction method and diluted from 50 to 1.56 mg/ml. Standard techniques of agar disk diffusion and broth microdilution assays were applied for qualitative and quantitative determinations of antibacterial activity of green tea extract on each isolates.

RESULTS

All clinical isolates of S. mutans (100%) were sensitive to green tea extract at concentrations 6.25, 12.5, 25, and 50 mg/ml producing inhibition zones ranging from 10 to 38 mm. All periodontopathic isolates (A. actinomycetemcomitans, n = 20, P. intermedia, n = 20, and P. gingivalis, n = 20) (100%) tested were sensitive to 12.5, 25, and 50 mg/ml of this extract. The minimal inhibitory concentration of green tea extract for S. mutans was 3.28 ± 0.7 mg/ml and for A. actinomycetemcomitans 6.25, for P. gingivalis and P. intermedia 12.5 mg/ml.

CONCLUSIONS

Our findings showed that green tea extract exhibited strong antibacterial activity on S. mutans,A. actinomycetemcomitans,P. gingivalis and P. intermedia and therefore may be used in mouthwashes or dentifrices for prevention of dental caries and periodontal diseases.

Green tea for weight loss and weight maintenance in overweight or obese adults

BACKGROUND

Preparations of green tea are used as aids in weight loss and weight maintenance. Catechins and caffeine, both contained in green tea, are each believed to have a role in increasing energy metabolism, which may lead to weight loss. A number of randomised controlled trials (RCTs) evaluating the role of green tea in weight loss have been published; however, the efficacy of green tea preparations in weight loss remains unclear.

OBJECTIVES

To assess the efficacy and safety of green tea preparations for weight loss and weight maintenance in overweight or obese adults.

SEARCH METHODS

We searched the following databases from inception to specified date as well as reference lists of relevant articles: The Cochrane Library (Issue 12, 2011), MEDLINE (December 2011), EMBASE (December 2011), CINAHL (January 2012), AMED (January 2012), Biological Abstracts (January 2012), IBIDS (August 2010), Obesity+ (January 2012), IPA (January 2012) and Web of Science (December 2011). Current Controlled Trials with links to other databases of ongoing trials was also searched.

SELECTION CRITERIA

RCTs of at least 12 weeks' duration comparing green tea preparations to a control in overweight or obese adults.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data, assessed studies for risk of bias and quality, with differences resolved by consensus. Heterogeneity of included studies was assessed visually using forest plots and quantified using the I(2) statistic. We synthesised data using meta-analysis and descriptive analysis as appropriate; subgroup and sensitivity analyses were conducted. Adverse effects reported in studies were recorded.

MAIN RESULTS

Due to the level of heterogeneity among studies, studies were divided into two groups; those conducted in Japan and those conducted outside Japan. Study length ranged between 12 and 13 weeks. Meta-analysis of six studies conducted outside Japan showed a mean difference (MD) in weight loss of -0.04 kg (95% CI -0.5 to 0.4; P = 0.88; I(2) = 18%; 532 participants). The eight studies conducted in Japan were not similar enough to allow pooling of results and MD in weight loss ranged from -0.2 kg to -3.5 kg (1030 participants) in favour of green tea preparations. Meta-analysis of studies measuring change in body mass index (BMI) conducted outside Japan showed a MD in BMI of -0.2 kg/m(2) (95% CI -0.5 to 0.1; P = 0.21; I(2) = 38%; 222 participants). Differences among the eight studies conducted in Japan did not allow pooling of results and showed a reduction in BMI ranging from no effect to -1.3 kg/m(2) (1030 participants), in favour of green tea preparations over control. Meta-analysis of five studies conducted outside Japan and measuring waist circumference reported a MD of -0.2 cm (95% CI -1.4 to 0.9; P = 0.70; I(2) = 58%; 404 participants). Differences among the eight studies conducted in Japan did not allow pooling of results and showed effects on waist circumference ranging from a gain of 1 cm to a loss of 3.3 cm (1030 participants). Meta-analysis for three weight loss studies, conducted outside Japan, with waist-to-hip ratio data (144 participants) yielded no significant change (MD 0; 95% CI -0.02 to 0.01). Analysis of two studies conducted to determine if green tea could help to maintain weight after a period of weight loss (184 participants) showed a change in weight loss of 0.6 to -1.6 kg, a change in BMI from 0.2 to -0.5 kg/m(2) and a change in waist circumference from 0.3 to -1.7 cm. In the eight studies that recorded adverse events, four reported adverse events that were mild to moderate, with the exception of two (green tea preparations group) that required hospitalisation (reported as not associated with the intervention). Nine studies reported on compliance/adherence, one study assessed attitude towards eating as part of the health-related quality of life outcome. No studies reported on patient satisfaction, morbidity or cost.

AUTHORS' CONCLUSIONS

Green tea preparations appear to induce a small, statistically non-significant weight loss in overweight or obese adults. Because the amount of weight loss is small, it is not likely to be clinically important. Green tea had no significant effect on the maintenance of weight loss. Of those studies recording information on adverse events, only two identified an adverse event requiring hospitalisation. The remaining adverse events were judged to be mild to moderate.

The microbiota is essential for the generation of black tea theaflavins-derived metabolites

Background

Theaflavins including theaflavin (TF), theaflavin-3-gallate (TF3G), theaflavin-3′-gallate (TF3′G), and theaflavin-3,3′-digallate (TFDG), are the most important bioactive polyphenols in black tea. Because of their poor systemic bioavailability, it is still unclear how these compounds can exert their biological functions. The objective of this study is to identify the microbial metabolites of theaflavins in mice and in humans.

Methods and Findings

In the present study, we gavaged specific pathogen free (SPF) mice and germ free (GF) mice with 200 mg/kg TFDG and identified TF, TF3G, TF3′G, and gallic acid as the major fecal metabolites of TFDG in SPF mice. These metabolites were absent in TFDG- gavaged GF mice. The microbial bioconversion of TFDG, TF3G, and TF3′G was also investigated in vitro using fecal slurries collected from three healthy human subjects. Our results indicate that TFDG is metabolized to TF, TF3G, TF3′G, gallic acid, and pyrogallol by human microbiota. Moreover, both TF3G and TF3′G are metabolized to TF, gallic acid, and pyrogallol by human microbiota. Importantly, we observed interindividual differences on the metabolism rate of gallic acid to pyrogallol among the three human subjects. In addition, we demonstrated that Lactobacillus plantarum 299v and Bacillus subtilis have the capacity to metabolize TFDG.

Conclusions

The microbiota is important for the metabolism of theaflavins in both mice and humans. The in vivo functional impact of microbiota-generated theaflavins-derived metabolites is worthwhile of further study.