Effects of green tea catechin extract on serum lipids in postmenopausal women: a randomized, placebo-controlled clinical trial

Tea consumption is associated with a reduced risk of coronary heart disease in female but not male populations in Guangzhou, China

BACKGROUND/OBJECTIVES

The association between tea consumption and risk of coronary heart disease (CHD) remains controversial. This study aimed to determine whether tea consumption has an effect on CHD risk in Chinese adults.

SUBJECTS/METHODS

In this hospital-based case-control study, 267 cases of CHD and 235 non-CHD controls were enrolled. Blood samples from all cases were examined. Cardiac function indices (left ventricular ejection fraction, left ventricular end-diastolic dimension, lactate dehydrogenase, and creatine kinase of the muscle or brain type), blood lipid index (high-density lipoprotein cholesterol), and blood coagulation function indices (fibrinogen and activated partial thromboplastin time) were recorded. Tea consumption of study participants was assessed by a specifically designed questionnaire. The baseline characteristics of the study populations were recorded, and CHD-related biomarkers were detected. Differences in baseline characteristics of the study participants were examined using t-tests for continuous variables and chi-squared tests for categorical variables. Unconditional logistic regression was used to measure the association between tea and CHD.

RESULTS

There were significant differences in cardiac function indices, blood lipid index, and blood coagulation indices between CHD cases and controls (P < 0.05). We found tea consumption reduced CHD risk in female participants (adjusted odds ratio (OR) = 0.484, 95% CI: 0.242–0.968, P = 0.0403). Regarding the type of tea consumed, the risk of CHD was reduced in women who drank partially fermented tea (adjusted OR = 0.210, 95% CI: 0.084–0.522, P = 0.0008). Analytic results for the amount of tea consumed per unit time showed CHD risk was reduced in women who consumed 1–2 cups of tea per day (adjusted OR = 0.291, 95% CI: 0.131–0.643, P = 0.0023). A tea-drinking frequency of > 6 days/week was beneficial for CHD prevention (adjusted OR = 0.183, 95% CI: 0.049–0.679, P = 0.0112). When analyzed according to the duration of tea consumption, the risk of CHD was reduced in participants who had been drinking tea for 10–20 years (adjusted OR = 0.360, 95% CI: 0.137–0.946, P = 0.0382).

CONCLUSIONS

Tea consumption is associated with a reduced risk of CHD in female but not male populations in Guangzhou.

Phenolic Profiles and Antioxidant Activities of 30 Tea Infusions from Green, Black, Oolong, White, Yellow and Dark Teas

Tea is among the most consumed drink worldwide, and its strong antioxidant activity is considered as the main contributor to several health benefits, such as cardiovascular protection and anticancer effect. In this study, the antioxidant activities of 30 tea infusions, which were obtained by the mimic of drinking tea of the public, from green, black, oolong, white, yellow and dark teas, were evaluated using ferric-reducing antioxidant power (FRAP) and Trolox equivalent antioxidant capacity (TEAC) assays, ranging from 504.80 ± 17.44 to 4647.47 ± 57.87 µmol Fe²⁺/g dry weight (DW) and 166.29 ± 24.48 to 2532.41 ± 50.18 µmol Trolox/g DW, respectively. Moreover, their total phenolic contents (TPC) were detected by Folin-Ciocalteu assay and were in the range of 24.77 ± 2.02 to 252.65 ± 4.74 mg gallic acid equivalent (GAE)/g DW. Generally, Dianqing Tea, Lushan Yunwu Tea, and Xihu Longjing Tea showed the strongest antioxidant activities among 30 teas. Furthermore, the phenolic compounds in tea infusions were identified and quantified, with catechins most commonly detected, especially in green tea infusions, which were main contributors to their antioxidant activities. Besides tea polyphenols, considerable content of caffeine also presented in 30 tea infusions.

Key actors in cancer therapy: epigenetic modifiers

Epigenetic reprogramming plays a crucial role in the tumorigenicity and maintenance of tumor-specific gene expression that especially occurs through DNA methylation and/or histone modifications. It has well-defined mechanisms. It is known that alterations in the DNA methylation pattern and/or the loss of specific histone acetylation/methylation markers are related to several hallmarks of cancer, such as drug resistance, stemness, epithelial-mesenchymal transition, and metastasis. It has also recently been highlighted that epigenetic alterations are critical for the regulation of the stemlike properties of cancer cells (tumor-initiating cells; cancer stem cells). Cancer stem cells are thought to be responsible for the recurrence of cancer which makes the patient return to the clinic with metastatic tumor tissue. Hence, the dysregulation of epigenetic machinery represents potential new therapeutic targets. Therefore, compounds with epigenetic activities have become crucial for developing new therapy regimens (e.g., antimetastatic agents) in the fight against cancer. Here, we review the epigenetic modifiers that have already been used in the clinic and/or in clinical trials, related preclinical studies in cancer therapy, and the smart combination strategies that target cancer stem cells along with the other cancer cells. The emerging role of epitranscriptome (RNA epigenetic) in cancer therapy has also been included in this review as a new avenue and potential target for the better management of cancer-beneficial epigenetic machinery.

Effects and Mechanisms of Tea and Its Bioactive Compounds for the Prevention and Treatment of Cardiovascular Diseases: An Updated Review

Cardiovascular diseases (CVDs) are critical global public health issues with high morbidity and mortality. Epidemiological studies have revealed that regular tea drinking is inversely associated with the risk of CVDs. Additionally, substantial in vitro and in vivo experimental studies have shown that tea and its bioactive compounds are effective in protecting against CVDs. The relevant mechanisms include reducing blood lipid, alleviating ischemia/reperfusion injury, inhibiting oxidative stress, enhancing endothelial function, attenuating inflammation, and protecting cardiomyocyte function. Moreover, some clinical trials also proved the protective role of tea against CVDs. In order to provide a better understanding of the relationship between tea and CVDs, this review summarizes the effects of tea and its bioactive compounds against CVDs and discusses potential mechanisms of action based on evidence from epidemiological, experimental, and clinical studies.

Clinical Advances in Immunonutrition and Atherosclerosis: A Review

Atherosclerosis is a chronic low-grade inflammatory disease that affects large and medium-sized arteries and is considered to be a major underlying cause of cardiovascular disease (CVD). The high risk of mortality by atherosclerosis has led to the development of new strategies for disease prevention and management, including immunonutrition. Plant-based dietary patterns, functional foods, dietary supplements, and bioactive compounds such as the Mediterranean Diet, berries, polyunsaturated fatty acids, ω-3 and ω-6, vitamins E, A, C, and D, coenzyme Q10, as well as phytochemicals including isoflavones, stilbenes, and sterols have been associated with improvement in atheroma plaque at an inflammatory level. However, many of these correlations have been obtained in vitro and in experimental animals' models. On one hand, the present review focuses on the evidence obtained from epidemiological, dietary intervention and supplementation studies in humans supporting the role of immunonutrient supplementation and its effect on anti-inflammatory response in atherosclerotic disease. On the other hand, this review also analyzes the possible molecular mechanisms underlying the protective action of these supplements, which may lead a novel therapeutic approach to prevent or attenuate diet-related disease, such as atherosclerosis.

Epigallocatechin gallate (EGCG) alters body fat and lean mass through sex-dependent metabolic mechanisms in Drosophila melanogaster

There is increasing interest in the potential role of epigallocatechin gallate (EGCG) in changing body composition to lower body fat with increased lean mass. In this study, we examined the sex-dependent effect of EGCG on body composition, locomotion, feeding behaviour, sugar levels, and transcription levels of key regulators in lipid, carbohydrate, and energy metabolisms in Drosophila melanogaster. EGCG had no effects on body weights in both females and males, but decreased fat accumulation in females compared to the control, accompanied by a reduction in food intake. EGCG treatments increased lean mass and locomotor activity, and downregulated transcription levels of brummer (bmm), adipokinetic hormone (akh), and Drosophila insulin-like peptide 2 (dilp2), and upregulated spargel (srl) in males. In addition, EGCG decreased sugar levels in both females and males. In conclusion, EGCG promotes lean phenotype in D. melanogaster via sex-specific metabolic regulations.

Cynanchum wilfordii Etanolic Extract Controls Blood Cholesterol: A Double-blind, Randomized, Placebo-Controlled, Parallel Trial

We evaluated the effects of Cynanchum wilfordii (CW) ethanolic extract on blood cholesterol levels in adults with high low-density lipoprotein cholesterol (LDL-C) levels. In a double-blind, randomized, placebo-controlled, parallel trial, 84 subjects were recruited. Participants were randomly divided into two groups with a low-dose (300 mg/d) or high-dose (600 mg/d) of CW. Levels of very low-density lipoprotein (p = 0.022) and triglycerides (p = 0.022) were significantly lower in the low-dose CW group than in the placebo group after 8 weeks. In a subgroup of participants with LDL-C≥ 150 mg/dL (n = 33), there was a significant decrease in total cholesterol (low-dose, p = 0.012; high-dose, p = 0.021), apolipoprotein B (low-dose, p = 0.022; high-dose, p = 0.016), and cholesteryl ester transfer protein (low-dose, p = 0.037; high-dose, p = 0.016) after 8 weeks of CW. The correlation between changes in total cholesterol and baseline LDL-C levels was significant in the groups that received both doses of CW (low-dose, p = 0.010; high-dose, p = 0.015). These results show that the CW ethanolic extract can regulate blood cholesterol in subjects with LDL-C≥ 150 mg/dL.

The in Vivo Antioxidant Effects of (-)-Epigallocatechin-3-Gallate Consumption in Healthy Postmenopausal Women Measured by Urinary Excretion of Secondary Lipid Peroxidation Products

The present study was carried out to determine whether the consumption of epigallocatechin (EGCG), the major bioactive green tea catechin, exerts a positive effect on lowering in vivo lipid peroxidation, a measure of oxidative stress, in healthy postmenopausal women. Urinary excretion of secondary lipid peroxidation products, a measure of in vivo lipid peroxidation, was determined in 40 participants randomly assigned to consume a green tea catechin extract (843.0 ± 44.0 mg EGCG/d) or placebo capsules for 12 months. Urine samples were analyzed for individual polar and nonpolar lipophilic aldehydes and related carbonyl compounds by high-performance liquid chromatography (HPLC) at the beginning and at the end of the 12-month intervention period. Results show that two nonpolar aldehydes, nonanal and decatrienal, were both 48% lower (p < 0.005) following consumption of EGCG. These results indicate that a modest degree of in vivo antioxidant activity exists with long-term EGCG consumption, which could slightly limit oxidative damage associated with lipid peroxidation and the onset and progression of chronic diseases.

Effects of green tea extract on overweight and obese women with high levels of low density-lipoprotein-cholesterol (LDL-C): a randomised, double-blind, and cross-over placebo-controlled clinical trial

Background

This study aims to examine the effects of green tea extract (GTE) supplement on overweight and obese women with high levels of low density lipoprotein-cholesterol (LDL-C).

Methods

The randomized, double-blind, crossover and placebo-controlled clinical trial was conducted from August 2012 to December 2013. Seventy-three out of 90 subjects aged between 18 and 65 years, with body mass index (BMI) ≥ 27 kg/m² and LDL-C ≥ 130 mg/dl were included in the analysis. The subjects were randomly divided into Groups A and B. Group A received GTE supplement treatment for the first 6 weeks, while Group B received placebo daily. After 6 weeks of treatment and 14 days of washout period, Group A switched to placebo and Group B switched to GTE treatment for 6 weeks. The reduction of LDL-C level between treatments was assessed as the outcome. Additionally, anthropometric measurements, plasma lipoproteins and hormone peptides of both groups were measure at the beginning of weeks 6, 8, and 14 after treatment.

Results

Subjects treated with GTE (n = 73) for 6 weeks showed significant differences, with 4.8% (p = 0.048) reduction in LDL-C and 25.7% (p = 0.046) increase in leptin. However, there was no statistical difference in the levels of total cholesterol, triglyceride and high density lipoprotein between the GTE and placebo groups after treatments.

Conclusions

This study shows that green tea extract effectively increases leptin and reduces LDL in overweight and obese women after 6 weeks of treatment even though there were no significant changes in other biochemical markers related to overweight.

Trial registration

This clinical trial is registered with ClinicalTrials.gov: NCT02116517 on 17 April 2014. Retrospectively registered. The first patient enrolled in October 2012 and the study was completed December 2013.

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2355-x) contains supplementary material, which is available to authorized users.

Ginsenosides, catechins, quercetin and gut microbiota: Current evidence of challenging interactions

Recent studies have shown the role of gut microbiota in favoring the absorption of herbal products and the transformation of their active principles into metabolites endowed with biological activity. This review focuses on the evidence supporting the changes occurring, after metabolic reactions by specific bacteria that colonize the human gut, to ginseng-derived ginsenosides, green tea-derived catechins, and quercetin, this latter being a flavonoid aglycon bound to sugars and abundant in some vegetables and roots. Furthermore, the results of several studies demonstrating the potential beneficial effects of the active metabolites generated by these biotransformations on ginsenosides, catechins and quercetin will be reported.

The contribution of cholesterol and epigenetic changes to the pathophysiology of breast cancer

Breast cancer​ is one of the most commonly diagnosed cancers in women. Accumulating evidence suggests that cholesterol plays an important role in the development of breast cancer. Even though the mechanistic link between these two factors is not well understood, one possibility is that dysregulated cholesterol metabolism may affect lipid raft and membrane fluidity and can promote tumor development. Current studies have shown oxysterol 27-hydroxycholesterol (27-HC) as a critical regulator of cholesterol and breast cancer pathogenesis. This is supported by the significantly higher expression of CYP27A1 (cytochrome P450, family 27, subfamily A, polypeptide 1) in breast cancers. This enzyme is responsible for 27-HC synthesis from cholesterol. It has been shown that 27-HC can not only increase the proliferation of estrogen receptor (ER)-positive breast cancer cells but also stimulate tumor growth and metastasis in several breast cancer models. This phenomenon is surprising since 27-HC and other oxysterols generally reduce intracellular cholesterol levels by activating the liver X receptors (LXRs). Resolving this paradox will elucidate molecular pathways by which cholesterol, ER, and LXR are connected to breast cancer. These findings will also provide the rationale for evaluating pharmaceutical approaches that manipulate cholesterol or 27-HC synthesis in order to mitigate the impact of cholesterol on breast cancer pathophysiology. In addition to cholesterol, epigenetic changes including non-coding RNAs, and microRNAs, DNA methylation, and histone modifications, have all been shown to control tumorigenesis. The purpose of this review is to discuss the link between altered cholesterol metabolism and epigenetic modification during breast cancer progression.

Comparative studies on the hypolipidemic, antioxidant and hepatoprotective activities of catechin-enriched green and oolong tea in a double-blind clinical trial

This study aimed to compare the beneficial effect of catechin-enriched green tea and oolong tea on mildly hypercholesterolemic subjects. Sixty mildly hypercholesterolemic subjects (180-220 mg dL^-1) were enrolled and divided into three groups as catechin-enriched green tea (CEGT), catechin-enriched oolong tea (CEOT) or placebo. The subjects were instructed to drink 2 × 300 mL of CEGT (780.6 mg of catechin), CEOT (640.4 mg of catechin) or placebo beverage for 12 weeks. Drinking CEGT and CEOT significantly decreased (p < 0.05) the body weight, fat, and BMI, lipid peroxidation as well as lipid profile (TC, LDL-c, HDL-c, and TG). Also, intervention with CEGT and CEOT significantly improved (p < 0.05) the oxidative indices (TEAC and GSH) and antioxidant enzymes (SOD, CAT, GPx, and GR). Moreover, ultrasound examination endorsed the hepatoprotective activity of CEGT and CEOT by reverting mild fatty liver to the normal hepatic condition because of antioxidant and hypolipidemic activities. To summarize, both CEGT and CEOT showed similar antioxidant and hepatoprotective activities. However, CEOT displayed superior lipid-lowering activity compared to CEGT or placebo, and hence it could be used to amend the wellness condition of mildly hypercholesterolemic subjects.

Tea Consumption and Longitudinal Change in High-Density Lipoprotein Cholesterol Concentration in Chinese Adults

Background

The relation between tea consumption and age‐related changes in high‐density lipoprotein cholesterol (HDL‐C) concentrations remains unclear, and longitudinal human data are limited. The aim of current study was to examine the relation between tea intake and longitudinal change in HDL‐C concentrations.

Methods and Results

Baseline (2006) tea consumption was assessed via a questionnaire, and plasma HDL‐C concentrations were measured in 2006, 2008, 2010, and 2012 among 80 182 individuals (49±12 years of age) who did not have cardiovascular diseases or cancer, or did not use cholesterol‐lowering agents both at baseline (2006) and during the follow‐up period (2006–2012). The associations between baseline tea consumption and rate of change in HDL‐C concentrations were examined using generalized estimating equation models. Tea consumption was inversely associated with a decreased rate of HDL‐C concentrations (P‐trend <0.0001) in the fully adjusted model. The adjusted mean difference in the HDL‐C decreased rate was 0.010 (95% confidence interval, 0.008, 0.012) mmol/L per year for tea consumers versus nonconsumers (never or less than once/month group). Interactions between tea consumption and age, sex, lifestyle scores, and metabolic syndrome (all P‐interaction <0.0001) were identified. The associations between greater tea consumption and slower decrease in HDL‐C concentrations were more pronounced in men, individuals aged 60 or older, individuals with a lower lifestyle score, and individuals with metabolic syndrome (all P‐trend <0.0001).

Conclusions

Tea consumption was associated with slower age‐related decreases in HDL‐C concentrations during 6 years of follow‐up.

Clinical Trial Registration

URL: http://www.chictr.org. Unique identifier: ChiCTR‐TNRC‐11001489.

GPCR6A Is a Molecular Target for the Natural Products Gallate and EGCG in Green Tea

SCOPE

The molecular mechanisms whereby gallates in green tea exert metabolic effects are poorly understood.

METHODS AND RESULTS

We found that GPRC6A, a multi-ligand-sensing G-protein-coupled receptor that regulates energy metabolism, sex hormone production, and prostate cancer progression, is a target for gallates. Sodium gallate (SG), gallic acid (GA) > ethyl gallate (EG) > octyl gallate (OG) dose dependently activated ERK in HEK-293 cells transfected with GPRC6A but not in non-transfected controls. SG also stimulated insulin secretion in β-cells isolated from wild-type mice similar to the endogenous GPRC6A ligands, osteocalcin (Ocn) and testosterone (T). Side-chain additions to create OG resulted in loss of GPRC6A agonist activity. Another component of green tea, epigallocatechin 3-gallate (EGCG), dose-dependently inhibited Ocn activation of GPRC6A in HEK-293 cells transfected with GPRC6A and blocked the effect of Ocn in stimulating glucose production in CH10T1/2 cells. Using structural models of the venus fly trap (VFT) and 7-transmembrane (7-TM) domains of GPRC6A, calculations suggest that l-amino acids and GA bind to the VFT, whereas EGCG is calculated to bind to sites in both the VFT and 7-TM.

CONCLUSION

GA and EGCG have offsetting agonist and antagonist effects on GPRC6A that may account for the variable metabolic effect of green tea consumption.

Impact of green tea extract on serum lipid of postmenopausal women: A randomized controlled trial

Background

This study aimed to evaluate the impact of green tea extract on serum lipid level in postmenopausal women.

Method

In this randomized controlled trial 100 postmenopausal women with an abnormality in at least one lipid profile were recruited and randomly assigned to one of the two groups: green tea extract (n = 50) and control group (n = 50). The intervention group received two capsules (400 mg) of green tea extract two times daily; the control group received a placebo for 4 weeks. The serum level of the lipid profile (total cholesterol, low density lipoprotein (LDL), high density lipoprotein (HDL), triglyceride, and fasting blood sugar) was measured at baseline and 4 weeks after intervention.

Results

In total, 79 women completed the study. The mean total cholesterol in the green tea group was significantly decreased after 4 weeks of intervention (mean difference −18.1 vs. −5 mg/dL in the green tea and placebo groups, p < 0.04). The triglyceride and LDL also decreased significantly in the green tea group compared to the control group (p = 0.002 and p = 0.04 respectively). The level of HDL and fasting blood sugar did not change within the group and between groups.

Conclusion

Green tea extract is cost-effective way to decrease lipid profile in postmenopausal women without major side effects. Using this herb is recommended in women who have slight lipid profile abnormalities.

Flavonoids and Their Metabolites: Prevention in Cardiovascular Diseases and Diabetes

The occurrence of atherosclerosis and diabetes is expanding rapidly worldwide. These two metabolic disorders often co-occur, and are part of what is often referred to as the metabolic syndrome. In order to determine future therapies, we propose that molecular mechanisms should be investigated. Once the aetiology of the metabolic syndrome is clear, a nutritional intervention should be assessed. Here we focus on the protective effects of some dietary flavonoids, and their metabolites. Further studies may also pave the way for development of novel drug candidates.

Effects of green tea on lipid metabolism in overweight or obese people: A meta-analysis of randomized controlled trials

SCOPE

The effects of green tea on lipid metabolism were inconsistent. The objective of this meta-analysis was to evaluate the effects of green tea on lipid metabolism in overweight or obese people.

METHODS AND RESULTS

We searched randomized controlled trials (RCTs) comparing green tea with a control on lipid metabolism on PUBMED and WEB OF SCIENCE (January 1990 to September 2016), COCHRANE and EMBASE (updated to October 2016), and the Chinese databases CNKI, WanFang and CBMD. Twenty-one articles studying 1704 overweight or obese subjects were selected for this meta-analysis. The pooled results demonstrated that green tea significantly decreased plasma total cholesterol (TC) and low-density lipoprotein cholesterol (LDL) levels in overweight or obese people. The weighted mean difference was -3.38 mg/dl for TC (95% CI: -6.42,  -0.33 mg/dL) and -5.29 mg/dL for LDL (95% CI: -7.92, -2.6 6 mg/dL), respectively. Green tea intake, however, showed no effect on plasma triglyceride (TG) and high-density lipoprotein cholesterol(HDL) levels in overweight or obese people with a relatively high heterogeneity.

CONCLUSION

The meta-analysis shows that drinking green tea can lower plasma TC and LDL levels significantly. Nevertheless, green tea's effect on plasma TG and HDL must be further evaluated by additional high-quality and large-scale RCTs.

A Systematic Review and Meta-Analysis of the Effects of Flavanol-Containing Tea, Cocoa and Apple Products on Body Composition and Blood Lipids: Exploring the Factors Responsible for Variability in Their Efficacy

Several randomized controlled trials (RCTs) and meta-analyses support the benefits of flavanols on cardiometabolic health, but the factors affecting variability in the responses to these compounds have not been properly assessed. The objectives of this meta-analysis were to systematically collect the RCTs-based-evidence of the effects of flavanol-containing tea, cocoa and apple products on selected biomarkers of cardiometabolic risk and to explore the influence of various factors on the variability in the responses to the consumption of these products. A total of 120 RCTs were selected. Despite a high heterogeneity, the intake of the flavanol-containing products was associated using a random model with changes (reported as standardized difference in means (SDM)) in body mass index (−0.15, p < 0.001), waist circumference (−0.29, p < 0.001), total-cholesterol (−0.21, p < 0.001), LDL-cholesterol (−0.23, p < 0.001), and triacylglycerides (−0.11, p = 0.027), and with an increase of HDL-cholesterol (0.15, p = 0.005). Through subgroup analyses, we showed the influence of baseline-BMI, sex, source/form of administration, medication and country of investigation on some of the outcome measures and suggest that flavanols may be more effective in specific subgroups such as those with a BMI ≥ 25.0 kg/m², non-medicated individuals or by specifically using tea products. This meta-analysis provides the first robust evidence of the effects induced by the consumption of flavanol-containing tea, cocoa and apple products on weight and lipid biomarkers and shows the influence of various factors that can affect their bioefficacy in humans. Of note, some of these effects are quantitatively comparable to those produced by drugs, life-style changes or other natural products. Further, RCTs in well-characterized populations are required to fully comprehend the factors affecting inter-individual responses to flavanol and thereby improve flavanols efficacy in the prevention of cardiometabolic disorders.

The role of nutraceuticals in the prevention of cardiovascular disease

Cardiovascular disease (CVD) ranks among the most common health-related and economic issues worldwide. Dietary factors are important contributors to cardiovascular risk, either directly, or through their effects on other cardiovascular risk factors including hypertension, dyslipidemia and diabetes mellitus. Nutraceuticals are natural nutritional compounds, which have been shown to be efficacious in preventative medicine or in the treatment of disease. Several foods and dietary supplements have been shown to protect against the development of CVD. The aim of this review is to present an update on the most recent evidence relating to the use of nutraceuticals in the context of the prevention and treatment of CVD.

Healthy properties of green and white teas: an update

Green tea has been consumed for centuries in Japan, China and Morocco.