Article

Effect of Black Tea Consumption on Intracellular Cytokines, Regulatory T Cells and Metabolic Biomarkers in Type 2 Diabetes Patients

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Abstract

The present study was undertaken to evaluate the effects of black tea intake on inflammatory cytokines and metabolic biomarkers in Type 2 diabetes mellitus (T2DM). Thirty patients with T2DM were randomly assigned either to a High Intake (HI) group, consuming three cups (600 mL) of black tea per day; and a Low Intake (LI) group, administered 1 cup (200 mL) per day, each during a 12-week period. Intracellular cytokine expression, regulatory T cells (Treg), glycemic and lipid profiles were measured at baseline and following the tea intake period. Tea consumption correlated with major effects measured in peripheral blood of subjects that included significantly reduced glycated hemoglobin (HbA1c) levels, along with increased regulatory T cells CD3+ CD4+ CD25+ FOXP3, CD3+ CD4+ IL-10+ cells (an immunosuppressive phenotype), reduced (pro-inflammatory) CD3+ CD4+ IL-17+ cells and reduced Th1-associated CD3+ CD4+ IFN-Υ+ cells. Tea consumption was also observed to abolish the significance of an inverse correlation between total serum cholesterol and representation of CD4+ IL-4+ T cells, which may reflect protection against atopy-related oxidative stress. Outcomes of this study describe both advantages and limitations to consumption of black tea as an aid to sustained health maintenance by persons at-risk for TD2M and related obesity-associated metabolic syndromes. Copyright © 2015 John Wiley & Sons, Ltd.

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... Effects of black tea against hyperglycemia and dyslipidemia had been demonstrated in different experimental settings (Mahmoud et al., 2016;Naveed et al., 2018;Neyestani et al., 2010;Ramadan et al., 2009;Ramlagan et al., 2017). An inhibition of inflammatory pathways in diabetic conditions by black tea is indicated by an increase of IL-10 and IL-17, and a decrease of IFN-γ and Creactive protein, respectively (Mahmoud et al., 2016;Naveed et al., 2018;Neyestani et al., 2010). ...
... Effects of black tea against hyperglycemia and dyslipidemia had been demonstrated in different experimental settings (Mahmoud et al., 2016;Naveed et al., 2018;Neyestani et al., 2010;Ramadan et al., 2009;Ramlagan et al., 2017). An inhibition of inflammatory pathways in diabetic conditions by black tea is indicated by an increase of IL-10 and IL-17, and a decrease of IFN-γ and Creactive protein, respectively (Mahmoud et al., 2016;Naveed et al., 2018;Neyestani et al., 2010). In accordance to anti-diabetic effects of black tea, theaflavins showed anti-hyperglycemic (e.g., decline in glucose, increase in insulin sensitivity, scavenger activity for RCS) (Imran et al., 2018;Lo et al., 2006;Miyata et al., 2013) and anti-dyslipidemic effects (e.g., decrease in cholesterol, LDL and triacylglycerols; increase in HDL) (Imran et al., 2018). ...
... In our study, BTE treatment also caused a reduction of weight gain which corresponded to a significant decline in levels of triglycerides and LDL, paralleled by an increase in FFAs. In previous studies, positive effects against dyslipidemia by BTE had been demonstrated by a decrease in cholesterol, LDL and triglycerides and/or increase in HDL or theaflavins (Imran et al., 2018;Mahmoud et al., 2016;Miyata et al., 2013;Naveed et al., 2018;Ramadan et al., 2009). Metformin is a widely used T2D drug which significantly decreased fasted blood glucose levels in ZDF rats and improved glucose tolerance. ...
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Effects of a theaflavin-enriched black tea extract (BTE) against type 2 diabetes (T2D) were analyzed using the obese ZDF model. ZDF rats were hyperglycemic, dyslipidemic and express pro-inflammatory markers. BTE was well tolerated and caused an elevation of fasted and fed glucose as well as lower glucose tolerance in contrast to hypoglycemic effects by metformin. However, the BTE group showed decreased levels of LDL and triacylglycerols which corresponded to an increase in free fatty acids. Positive effects against dyslipidemia of BTE corresponded to a significant decrease in weight gain. The impact on inflammatory pathways was analyzed by expression analysis of inflammatory mediators in whole blood and epididymal adipose tissue using TaqMan PCR and ELISA. Whole blood analysis revealed a significant down-regulation of ICAM-1 and TNF-α, whereas IL-4, IL-6, IL-10, IL-13 and IFN-γ were elevated to higher levels as compared to ibuprofen. In adipose tissue, BTE treatment induced an upregulation of COX-2 and IL-6. Thus, BTE treatment showed strong effects against systemic inflammation and caused a reduction of weight gain with positive effects against dyslipidemia. The complexity of signaling pathways leading to complications in diabetes suggest a treatment of BTE in combination with antidiabetic therapeutics as promising strategy against T2D.
... Focused meta-analytical evidence on tea drinking in relation to inflammation and related markers is lacking. Four trials conducted some research in this field [43,[54][55][56]. With regard to black tea a 12week trial showed that three cups (600 ml) daily increased regulatory T-cells and reduced pro-inflammatory cells amongst patients with type 2 diabetes [55]. ...
... Four trials conducted some research in this field [43,[54][55][56]. With regard to black tea a 12week trial showed that three cups (600 ml) daily increased regulatory T-cells and reduced pro-inflammatory cells amongst patients with type 2 diabetes [55]. A large Mauritian trial found that CRP levels reduced by 53.4% in men and 41.1% in women at high risk of ischemic heart disease drinking 3 cups of black tea daily over 12-weeks [56]. ...
... The number of studies looking at tea in relation to inflammation was small but indicated a positive effect. Some findings suggest that certain populations may benefit such as those with type 2 diabetes [55] or ischemic heart disease [56]. Further studies on healthy populations are needed to better understand how tea drinking could affect inflammation. ...
... In addition, tea beverages have a huge market all over the world because of the positive effects of tea on human health. For example, black tea can reduce complications in diabetics [14], tea polyphenols in tea can be used to reduce sebum production in the skin and treat acne vulgaris [15] and have anti-inflammatory properties [16], black and green tea can be used to prevent and treat high cholesterol [17]. So we add tea leaves to our dataset, which is taken from our tea base and contains 4 types of disease states: tea leaf health, tea white star disease, tea whorlspot disease, and tea anthracnose. ...
... The edges in the figure are entitled values to represent the loss. For example, the weight of the dashed line between the pixel point and the S point represents the loss of classifying the (2) Apple scab serious (3) Apple frogeye spot (4) Cedar apple rust general (5) Cedar apple rust serious (6) Cherry healthy (7) Cherry powdery mildew general (8) Cherry powdery mildew serious (9) Corn healthy (10) Cercospora zeae-maydis Tehon and Daniels general (11) Cercospora zeae-maydis Tehon and Daniels serious (12) Puccinia polysora general (13) Puccinia polysora serious (14) Corn curvularia leaf spot fungus general (15) pixel as background, and the weight of the dashed line between the pixel point and the T point represents the loss of classifying the pixel as foreground. GrabCut algorithm builds a Gaussian Mixture Model (GMM) for foreground and background separately. ...
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In this paper, a lightweight convolutional neural network is proposed for the classification of plant diseases, containing 63 classes of states for 11 plant species. The different context of experimental data and data in the real environment, insufficient accuracy of the model classification, and oversized model are three main problems of deep learning techniques applied to agricultural production. In this paper, we mainly focus on these three problems. First, the GrabCut algorithm is adopted to unify the background of the experimental data and the real data to black, allowing the trained model to have the same good effect when applied in practice. Then, we propose a new coordinate attention block to improve the classification accuracy of convolutional neural networks and empirically demonstrate the effectiveness of our approach with several state-of-the-art CNN models. Finally, channel pruning is applied to the trained model, which reduces the model size and computational effort by 85.19%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document} and 92.15%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\%$$\end{document} respectively with little change in the model accuracy, making it better suited for agricultural platforms with lower memory and computational capacity.
... Black Tea: Mahmoud et al. tested the effects of black tea ingestion on the secretion of inflammatory cytokines and metabolic biomarkers in 30 patients with T2DM [12] . The results indicated that treatment with black tea at 200 or 600 ml per day, for 12 weeks, resulted in significantly decreased glycosylated hemoglobin levels and decreased total serum cholesterol levels and the markers of oxidative stress. ...
... The results indicated that treatment with black tea at 200 or 600 ml per day, for 12 weeks, resulted in significantly decreased glycosylated hemoglobin levels and decreased total serum cholesterol levels and the markers of oxidative stress. Furthermore, the supplementation of black tea could inhibit the inflammatory response including an increase in regulatory T cell secretion and a decrease in the production of proinflammatory cells [12] . ...
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Natural products have played and continue to play a great role in the management of different diseases. Natural products are usually believed to be safer, cheaper, easily available and sometimes more efficacious than purely synthetic drugs. Diabetes mellitus is a major health problem in the world. There is no cure for diabetes. With the increase in a number of newer drugs for diabetes, there is the possibility of a wide range of side effects that vary from one drug to another. It is, therefore, essential to practice effective methods of the treatment and management of diabetes. Hence, the need to explore antidiabetic drugs of natural origin with minimal side effects is highly essential. This review provides a scientific perspective on the usage and research of natural traditional remedies in the management of diabetes. The aim of the present review is to provide a comprehensive and concise overview of the previously reported clinical trials of antioxidative natural products in the management of diabetes. Keywords: Diabetes, Natural products, Hyperglycemia, Diabetic complications
... Further, recent in vitro, in vivo, and clinical trials further supported the effects of tea on the prevention and treatment of diabetes mellitus and its complications [20,21]. In addition, tea is a potential hypoglycemic substance with low cost, good patient compliance, and fewer side effects compared with many synthetic hypoglycemic drugs [22]. In order to provide an updated understanding of tea targeting diabetes mellitus and its complications, we searched related literature of epidemiological, experimental, and clinical studies based on PubMed and Web of Science databases and reviewed and discussed the protective effects of tea against diabetes mellitus and its complications, highlighting the related molecular mechanisms. ...
... Further, it was reported that postprandial blood sugar could be decreased in people drinking black tea [39]. A clinical trial conducted in Kuwait also revealed that drinking black tea for one year could significantly reduce HbA1c level and pro-inflammatory CD3 + CD4 + IL-17 + cells, and eliminate serum total cholesterol, thereby preventing diabetes mellitus and its complications [22]. Moreover, another trial demonstrated that black tea could protect against diabetes mellitus and diabetic cardiovascular disease through its anti-inflammatory and antioxidant properties [58]. ...
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Diabetes mellitus has become a serious and growing public health concern. It has high morbidity and mortality because of its complications, such as diabetic nephropathy, diabetic cardiovascular complication, diabetic neuropathy, diabetic retinopathy, and diabetic hepatopathy. Epidemiological studies revealed that the consumption of tea was inversely associated with the risk of diabetes mellitus and its complications. Experimental studies demonstrated that tea had protective effects against diabetes mellitus and its complications via several possible mechanisms, including enhancing insulin action, ameliorating insulin resistance, activating insulin signaling pathway, protecting islet β-cells, scavenging free radicals, and decreasing inflammation. Moreover, clinical trials also confirmed that tea intervention is effective in patients with diabetes mellitus and its complications. Therefore, in order to highlight the importance of tea in the prevention and management of diabetes mellitus and its complications, this article summarizes and discusses the effects of tea against diabetes mellitus and its complications based on the findings from epidemiological, experimental, and clinical studies, with the special attention paid to the mechanisms of action.
... The control group was asked to stay on 150 mL/day of black tea throughout the inter- vention period (Neyestani, et al., 2010). Likewise, the administra- tion of 3 cups/day (600 mL, high intake) or one cup/day (200 mL, low intake) of black tea to 36 patients with T2D (18 men and 18 women) for 12 weeks showed certain improvements related to the disease in the high-intake-patients (Mahmoud, et al., 2016). Thus, in the tea-group it was observed reduced HbA1c and total serum cholesterol levels, along with increased regulatory T cells CD3 þ CD4 þ CD25 þ FOXP3, CD3 þ CD4 þ IL-10 þ cells (an immunosup- pressive phenotype), reduced (pro-inflammatory) CD3 þ CD4 þ IL- 17 þ cells and reduced Th1-associated CD3 þ CD4 þ IFN-gþ cells. ...
... Thus, in the tea-group it was observed reduced HbA1c and total serum cholesterol levels, along with increased regulatory T cells CD3 þ CD4 þ CD25 þ FOXP3, CD3 þ CD4 þ IL-10 þ cells (an immunosup- pressive phenotype), reduced (pro-inflammatory) CD3 þ CD4 þ IL- 17 þ cells and reduced Th1-associated CD3 þ CD4 þ IFN-gþ cells. The preparation of tea was as follows: one tea bag as (2.5 g) of dry black tea as sold was infused in 200 mL of water brought to a boil, then steeped for 3 min (Mahmoud, et al., 2016). Finally, an study with oolong tea demonstrated that the consumption of 1500 mL oolong tea [five tea bags (15 g of tea leaf) were added to 1500 mL of boiling water and steeped for 10 min] taken five times per day independent of daily water intake for 30 days diminished the glycaemia and plasma fructosamine levels (Hosoda, et al., 2003). ...
Article
Prevention of diabetes through the diet has recently received an increasing interest, and polyphenolic compounds, such as flavanols, have become important potential chemopreventive natural agents due to their proved benefits on health, with low toxicity and cost. Tea, red wine and cocoa are good sources of flavanols and these highly consumed foods might contribute to prevent diabetes. In this regard, there is increasing evidence for a protective effect of tea, red wine and cocoa consumption against this disorder. This review summarizes the available epidemiological and interventional human studies providing evidence for and against this effect. Overall observational data suggest a benefit, but results are still equivocal and likely confounded by lifestyle and background dietary factors. The weight of data indicate favourable effects on diabetes risk factors for tea, red wine and cocoa intake, and a number of plausible mechanisms have been elucidated in human studies. However, despite the growing evidence it remains uncertain whether tea, red wine and cocoa consumption should be recommended to the general population or to patients as a strategy to reduce the risk of diabetes.
... The hypoglycemic and antioxidative effects of DT are well known properties of several of its components (Gayathri and Kannabiran, 2008;Gul-e-Rana et al., 2013;Ahmed et al., 2011;Velayutham et al., 2012;Tripathi and Chandra, 2009;Belguith-Hadriche et al., 2010;Chevassus et al., 2010;Chalise et al., 2010). These factors also suggest that the herbal constituents of DT, shown in Table 2, combine additively with compounds in Camellia sinensis which authors of the present report have previously demonstrated to mediate anti-inflammatory and immunoregulatory effects (Mahmoud et al., 2016). ...
... Specifically, Metformin, gliclazide and repaglinide have immunomodulatory effects, which may have biased the data outcomes with respect to effect of DT on representation of Tregs and cells expressing inflammatory cytokines (Son et al., 2014;Drzewoski and Zurawska-Klis, 2006;Yamazaki et al., 2014;Tung et al., 2011;Gumieniczek et al., 2005). A further confounder that must be taken into account in order to clearly interpret the data is the anti-inflammatory and immunomodulatory effect of phytochemical components of black tea, as previously described by the authors (Mahmoud et al., 2016), which was used as "placebo" control material. Indeed, the present study was designed as a follow-on investigation to the above-mentioned 2016 black tea study. ...
Article
Ethnopharmacological relevance: Diabetea tea (TM) (DT) is an anti-diabetic alternative medicine in some Asian countries. The main constituent of DT is black tea originating from Camellia sinensis that is supplemented by 12 other medicinal plants. Black tea contains a large amount of the flavonoids catechins especially epigallocatechin gallate (EGCG) which has anti-inflammatory and antioxidative capacity. This study was undertaken to evaluate the possible effects of DT intake on inflammatory cytokines, regulatory T cells (Tregs) and metabolic biomarkers in T2DM. Materials and methods: The study included 50 patients with T2DM. The patients had received 3 cups (600ml) of DT extract or placebo (PL) extract per day during a period of 12 weeks. Intracellular cytokine expression in peripheral blood mononuclear cell (PBMC) as well as the glycemic and lipid profiles were measured at baseline and after the treatment period. The active constituents of the medicinal plants included in DT were investigated by gas chromatography-mass spectrometry (GC/MS). Results: Ingestion of DT suppressed CD4+ T cell expression of IL-1β and Il-8 (p<0.05) and up-regulated the expression of IL-10 and the Treg/IL-17 ratio (p<0.05) which was not shown in PL. A significant decrease in HbA1C and LDL was observed at the end of the study period (p<0.05) in DT. The GC/MS analyses of DT indicated the presence of lupeol, β-Amyrin and β-sitosterol. Also analyses of individual herbs showed the presence of higher levels of lupeol and β-Amyrin in Nuga Ficus bengalensis and β-sitosterol in the Attikka Ficus racemosa, indicating that the active ingredients of DT are concentrated in these two herbs. Conclusion: The present study provides evidence that DT has hypoglycemic and antihyperlipidemic properties. Interestingly, DT has anti-inflammatory effects. These properties are attributed to the flavonoids, triterpenes and phytosterol contents of the tea. We suggest that DT protects against diabetes complications in the long term.
... Since ancient times, drinking tea has been an important part of human diet as a loyal partner. Tea has a long history of cultivation and drinking, which is the second beverage after water (Mahmoud et al. 2016). According to the processing technology, degree of fermentation and enzymatic changes, tea can be divided into: green tea (unfermented), white tea (slightly fermented), yellow tea (lightly fermented), oolong tea (semi-fermented), black tea (completely fermented) and dark tea (post-fermented) (Fang et al. 2019). ...
Article
Depression is a global public health issue with high morbidity and mortality, which tends to cause fatigue, inability to concentrate, insomnia, and loss of appetite, especially represented by major depressive disorder (MDD). Pathologically, depression is associated with hyperactivity of hypothalamic–pituitaryadrenal (HPA) axis, inflammation, loss of monoaminergic system, and disturbance of gut microbiota. Epidemiological studies have shown that regular tea drinking can reduce the risk of depression. Tea bioactive compounds (L-theanine, catechin, tea pigment and GABA) can regulate depression by inhibiting hyperactive HPA axis, reducing the inflammatory response, restoring the monoaminergic system, inhibiting monoamine oxidase levels, increasing the enrichment of intestinal flora and promoting microbial-gut-brain axis activity. This review discusses the composition, structure, bioavailability and safety of bioactive components from tea, and focuses on exploring the possible pathways of tea bioactive compounds in the regulation of depression. In addition, the low bioavailability of natural bioactive compounds from tea limits the efficacy on depression. Emerging technologies (such as metabolomics, proteomics, and genomics) and nano-encapsulation can be utilized to improve the stability and bioavailability of tea active ingredients, and reduce the potential biotoxicity. The review provides a theoretical basis of utilization of tea active compounds for formulating the prevention and treatment of depression.
... The presence of catechin in tea improves endothelial functioning by activating PI3K signal cells, endothelial nitric oxide synthase (eNOS) enzyme and formation of Nitric oxide . Furthermore, Mahmoud et al. (2016) have observed that tea and tea extracts provide protective effects against cytokine-induced cell injuries to insulinproducing cells. ...
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The current investigation was undertaken to develop Ready to Use (RTU) and Ready to Reconstitute (RTR) health beverage supplemented with functional ingredients. It was developed using double toned milk and replacing part of double toned milk with whey at 20, 30 & 40 %, the addition of Stevia:sugar blend (25:75, 50:50 & 100:00), the addition of almond oil or walnut oil at 2, 3 & 4 % and tea decoction at 10, 15 & 20 % later subjected to sensory evaluation. Finally, based on sensory scores, replacement of double toned milk with 30 % whey, addition 100:0 Stevia:sugar blend, 2 % almond oil or walnut oil and 15 % tea decoction was optimised. The optimised health beverage was concentrated to 31 % total solids and spray dried (inlet 180±10 and outlet 80±10 °C temperatures) to obtain ready to reconstitute health beverage powder which was packed in plastic pouches and stored at ambient temperature for further studies. The effect of reconstitution on the sensory characteristics was determined for different ratios. Among all ratios, 1:8 reconstituted health beverage was awarded the highest sensory score, which was comparable to control.
... The traditional medicines targeted at T2DM, such as sulfonylureas, biguanides and thiazolidinediones, are used to ameliorate IR and exhibit a strong hypoglycemic effect in the insulin conduction pathway. 5 However, this is not a good choice for controlling the blood Glc of T2DM patients because these drugs have a single target and route of action and the long-term use of them can cause a series of adverse reactions, although with a clear mechanism of action and strong efficacy. Therefore, the search for natural foods with no toxic side effects and good glycemic effect to replace these drugs is an urgent problem to be solved in the clinical intervention treatment of T2DM. ...
Article
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Background: Dark tea, one of the six major teas, has many biological activities, which originates from their active substrates, such as polyphenols, polysaccharide and so on. The hypoglycemic effect is one of its most prominent activities, but less is known about their evaluation and potential role in hypoglycemic mechanism. Results: In the current study, we separately analyzed the phytochemical composition, glycosidase inhibition and free radical scavenging activities, hypoglycemic activity in the type 2 diabetes mellitus (T2DM) mice, and the alleviation of insulin resistance (IR) in the HepG2 cells of four dark tea aqueous extracts (DTAEs). The results showed that the phytochemical composition of DTAEs was significantly different, and they all had good glycosidase inhibition and free radical scavenging activities, in vivo hypoglycemic activity and alleviation of IR, and could activate the PI3K-Akt-PPARs cascade signaling pathway to regulate glucose (Glc) and lipid metabolism, change the key enzyme activities related to Glc metabolism and antioxidant, and reduce oxidative stress and inflammatory factor levels. Among them, LBT (Liubao brick tea) and PET (Pu-erh tea) possessed better glycosidase inhibitory activity, in vivo hypoglycemic activity and improve insulin resistance activity, while QBT (Qingzhuan brick tea) and FBT (Fuzhuan brick tea) had better free radical scavenging activity, which may be explained by their distinct phytochemical compositions such as tea protein, polysaccharide, polyphenols, catechins, and tea pigments and some elements. Conclusion: Dark tea is a highly attractive candidate for developing antidiabetic food, LBT and PET may be good natural sources of agricultural products with anti-diabetic effect. This article is protected by copyright. All rights reserved.
... Our data indicated the potential effect of tea consumption against DR. Tea is regarded as a potential hypoglycemic substance with low cost, good patient compliance, and fewer side effects compared with many synthetic drugs [41]. Thus, tea consumption has good potential to be applied for clinical and public prevention against DR. ...
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Aim: To investigate the association between variables related to tea consumption (duration, frequency, and type) and the risk of diabetic retinopathy. Methods: A rural community-based, cross-sectional survey was conducted in Weitang Town, Suzhou, China. People aged 60 years or above were invited to complete the survey. All eligible patients underwent detailed eye examination. Diabetic retinopathy (DR) was diagnosed and graded based on the retinal fundus imaging. Diabetes was defined as fasting glucose concentrations of ≥7.0 mmol/L or self-reported diagnosis of diabetes. Information about tea consumption such as duration, type, and frequency, together with demographics and lifestyle characteristics, were collected using a face-to-face questionnaire interview. The association between tea consumption and the risk of DR was determined by univariate and multivariate logistic regression analyses. Results: Among the 5,281 participants, 614 had diabetes mellitus (prevalence of 11.63%). The prevalence rate of DR was 10.38% in the diabetic population and 1.04% in the general population. Compared with non-tea consumers, the crude OR values for DR in subjects with long-term and short-term tea consumption were 0.34 (95%CI = 0.14-0.82, p = 0.016) and 1.64 (95%CI = 0.74-3.64, p = 0.221), respectively. When adjusted for age, gender, and other confounders, consumption of tea for ≥20 years was associated with reduced odds of DR (OR = 0.29, 95%CI = 0.09-0.97, p = 0.044). Thus, long-term tea consumption was significantly associated with a lower risk of DR. There was no statistical significance between frequency or type of tea consumption with DR (p > 0.05). Conclusion: Elderly diabetic Chinese residents who consumed tea for more than twenty years had a lower risk of DR compared to non-tea consumers. The long-term tea consumption may be an independent protective factor for DR. However, further studies are warranted to examine the association.
... Tea has shown promising efficacy in managing T2DM in several clinical trials, in terms of improving insulin resistance and postprandial hyperglycemia of humans. Consumption of black tea significantly reduced glycated hemoglobin (HbA1c) level and helped to decrease the risk of suffering from TD2M in subjects [150]. In addition, regular intake of green tea could benefit high-fat dietinduced T2DM [151]. ...
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Tea is widely consumed all over the world. Generally, tea is divided into six categories: White, green, yellow, oolong, black, and dark teas, based on the fermentation degree. Tea contains abundant phytochemicals, such as polyphenols, pigments, polysaccharides, alkaloids, free amino acids, and saponins. However, the bioavailability of tea phytochemicals is relatively low. Thus, some novel technologies like nanotechnology have been developed to improve the bioavailability of tea bioactive components and consequently enhance the bioactivity. So far, many studies have demonstrated that tea shows various health functions, such as antioxidant, anti-inflammatory, immuno-regulatory, anticancer, cardiovascular-protective, anti-diabetic, anti-obesity, and hepato-protective effects. Moreover, it is also considered that drinking tea is safe to humans, since reports about the severe adverse effects of tea consumption are rare. In order to provide a better understanding of tea and its health potential, this review summarizes and discusses recent literature on the bioactive components, bioavailability, health functions, and safety issues of tea, with special attention paid to the related molecular mechanisms of tea health functions.
... As for tea types, the diabetes-related research on rats (35) has suggested potential benefits of green and black teas in insulin and glucose metabolism. Mahmoud's cohort work discovered that administrating 3 cups/day of black tea can ameliorate the progression of type 2 diabetes in adults (36) . The Singapore Chinese study had a suggestive 14% (RR: 0.86; 95% CI: 0.74, 1.00) reduction in risk of diabetes within participants drinking black tea >1 cup/day compared with non-consumers, but there was no association observed concerning green tea (13) . ...
Article
The aim of this study is to explore the influence of tea consumption on diabetes mellitus in Chinese population. This multicenter, cross-sectional study was conducted in eight sites from south, east, north, west and middle regions in China by enrolling 12,017 subjects aged 20–70. Sociodemographic and general information were collected by standardized questionnaire. Standard procedure was used to measure anthropometric characteristics and obtain blood samples. The diagnosis of diabetes was determined using a standard 75-g oral glucose tolerance test. In the final analysis, 10,825 participants were included, and multiple logistic models and interaction effect analysis were applied for assessing the association between tea-drinking with diabetes. Compared with non-tea drinkers, the multivariable-adjusted odds ratios for newly-diagnosed diabetes were 0.80(0.67, 0.97), 0.88(0.71, 1.09) and 0.86(0.67, 1.11) for daily tea-drinkers, occasional tea-drinkers and seldom tea-drinkers, respectively. Furthermore, drinking tea daily was related to decreased risk of diabetes in female by 32%, elderly (>45y) by 24% and obese (BMI>30kg/m2) by 34%. Moreover, drinking dark tea was associated with reduced risk of diabetes by 45% [OR: 0.55 (0.42, 0.72), P < 0.01]. The results imply that drinking tea daily was negatively related to risk of diabetes in female, elderly and obese people. In addition, drinking dark tea was associated with decreased risk of T2DM.
... The beneficial effects of green tea in many diseases such as CVD are related to its anti-inflammatory effects. 31,32 Green tea components can increase production of the anti-inflammatory cytokines such as IL-10, regulate synthesis and signaling of IL-6, decrease the pro-inflammatory cytokines such as IL-1β and TNF-α and decrease production of destructive matrix metalloproteinases through TNF-α induced phosphorylation of mitogen-activated protein kinases (MAPKs). Evidence suggest that the green tea catechins can downregulate several inflammatory cytokines and chemokines like IL-1α, IL-6, IL-8, CRP and interferon gamma (INF-γ). ...
... Moreover, a randomized acute crossover intervention study conducted in healthy volunteers showed the ability of coffee polyphenols to improve postprandial hyperglycemia, increasing glucagon-like peptide 1 secretion and decreasing oxidative stress [166]. Type 2 diabetic patients drinking three cups (600 mL) of black tea per day for 12 weeks reported a significant reduction in glycated hemoglobin level, together with an amelioration of the immune function relevant to prevention and management of type 2 diabetes [167]. The effect of tea seems to be related to its polyphenol contents, and in particular to epigallocatechin-3-gallate, which may act on glucose intestinal and cellular uptake and on oxidative stress [168]. ...
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Phytotherapy has long been a source of medicinal products and over the years there have been many attempts to use herbal medicines for the treatment of diabetes. Several medicinal plants and their preparations have been demonstrated to act at key points of glucidic metabolism. The most common mechanisms of action found include the inhibition of α-glucosidase and of AGE formation, the increase of GLUT-4 and PPARs expression and antioxidant activity. Despite the large amount of literature available, the actual clinical effectiveness of medicinal plants in controlling diabetes-related symptoms remains controversial and there is a crucial need for stronger evidence-based data. In this review, an overview of the medicinal plants, which use in the management of diabetes is supported by authoritative monographs, is provided. References to some species which are currently under increasing clinical investigation are also reported.
... results indicated that treatment with black tea at 200 or 600 ml per day, for 12 weeks, resulted in significantly decreased glycosylated hemoglobin levels and decreased total serum cholesterol levels and the markers of oxidative stress. Furthermore, the supplementation of black tea could inhibit the inflammatory response including an increase in regulatory T cell secretion and a decrease in the production of proinflammatory cells [99]. ...
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Diabetic cardiomyopathy (DCM) is a common and severe complication of diabetes and results in high mortality. It is therefore imperative to develop novel therapeutics for the prevention or inhibition of the progression of DCM. Oxidative stress is a key mechanism by which diabetes induces DCM. Hence, targeting of oxidative stress-related processes in DCM could be a promising therapeutic strategy. To date, a number of studies have shown beneficial effects of several natural products on the attenuation of DCM via an antioxidative mechanism of action. The aim of the present review is to provide a comprehensive and concise overview of the previously reported antioxidant natural products in the inhibition of DCM progression. Clinical trials of the antioxidative natural products in the management of DCM are included. In addition, discussion and perspectives are further provided in the present review.
... Since the completion of this meta-analysis, additional RCTs investigating the effects of tea or cocoa products containing flavanols on lipid and anthropometric variables have been added to the existing literature [111,[169][170][171][172][173][174][175][176][177][178][179][180][181][182][183]. The heterogeneity of these trials remains high with population samples including mixed sexes and ages, obese, overweight, healthy, hyperlipidemic and/or diabetic subjects, etc. ...
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... In several studies, their effects on prevention and treatment of different diseases have been reported (Kafash-Farkhad et al., 2013;Bahmani et al., 2014g;Saki et al., 2014a;Asadbeigi et al., 2014;Asadi et al., 2013;Shirzad et al., 2009;Bahmani et al., 2014a;Asadi-Samani et al., 2014;Bahmani et al., 2014c;Bahmani et al., 2014e;Asadi-Samani et al., 2016;Mahmoud et al., 2016;Ki et al., 2016;Talat et al., 2015). They are a rich source of natural compounds for preparation of safe and effective medications which can be used to treat inflammatory diseases. ...
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Searching for new natural drugs that are capable of targeting Th1 and Th17 may lead to development of more effective treatments for inflammatory and autoimmune diseases. Most of the natural drugs can be derived from plants that are used in traditional medicine and folk medicine. The aim of this systematic review is to identify and introduce plants or plant derivatives that are effective on inflammatory diseases by inhibiting Th1 and Th17 responses. To achieve this purpose, the search terms herb, herbal medicine, herbal drug, medicinal plant, phytochemical, traditional Chinese medicine, Ayurvedic medicine, natural compound, inflammation, inflammatory diseases, Th1, Th17, T helper 1 or T helper 17 were used separately in Title/Keywords/Abstract in Web of Science and PubMed databases. In articles investigating the effect of the medicinal plants and their derivatives in inhibiting Th1 and Th17 cells, the effects of eight extracts of the medicinal plants, 21 plant-based compounds and some of their derivatives, and eight drugs derived from the medicinal plants' compounds in inhibiting Th1 and Th17 cells were reviewed. The results showed that medicinal plants and their derivates are able to suppress Th17 and Th1 T cell functions as well as cytokine secretion and differentiation. The results can be used to produce herbal drugs that suppress Th, especially Th17, responses. Copyright © 2017 John Wiley & Sons, Ltd.
... Tea and tea extracts may have protective effects against cytokine-induced injuries in β cells and insulin-producing cells. There was study showing that three cups (600 mL with 7.5 g) of black tea intake reduced pro-inflammatory cytokines as TNF-α in human, while the expressions of the anti-inflammatory cytokines such as IL-4, IL-5 and IL-10 were increased [67]. An in vitro study showed that black tea infusion (150 mL with 2.5 g) suppressed expression of the inflammatory cytokines TNF-α, IL-1β and IL-6, while it increased IFN-γ, suggesting black tea had a selective pro-inflammatory cytokine that can also reduce IL-1β and IFN-γ in insulinoma cell and inducible NO synthase (iNOS) gene expression suppressive effect [68]. ...
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... The major contribution of the health-promoting effects of green tea is associated with its polyphenol content (Sano et al., 2001). Enhancement of immune system function (Khan et al., 2016), antibacterial activity (Di Vito et al., 2015), antineoplastic (Fujiki et al., 2015;Pedro et al., 2016), anti-inflammatory (Dona et al., 2003), antioxidative (Osada et al., 2001), antihyperlipidemic potentials (Raederstorff et al., 2003;Mahmoud et al., 2016), and protective effect over cardiovascular disease (Sueoka et al., 2001) are some of the health benefits of consuming green tea. Also green tea has been considered as a thermogenic plant for weight loss (Stohs and Badmaev, 2016). ...
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Despite epidemiological evidence that tea consumption is associated with the reduced risk of coronary heart disease, experimental studies designed to show that tea affects oxidative stress or blood cholesterol concentration have been unsuccessful. We assessed the effects of black tea consumption on lipid and lipoprotein concentrations in mildly hypercholesterolemic adults. Tea and other beverages were included in a carefully controlled weight-maintaining diet. Five servings/d of tea were compared with a placebo beverage in a blinded randomized crossover study (7 men and 8 women, consuming a controlled diet for 3 wk/treatment). The caffeine-free placebo was prepared to match the tea in color and taste. In a third period, caffeine was added to the placebo in an amount equal to that in the tea. Five servings/d of tea reduced total cholesterol 6.5%, LDL cholesterol 11.1%, apolipoprotein B 5% and lipoprotein(a) 16.4% compared with the placebo with added caffeine. Compared with the placebo without added caffeine, total cholesterol was reduced 3.8% and LDL cholesterol was reduced 7.5% whereas apolipoprotein B, Lp(a), HDL cholesterol, apolipoprotein A-I and triglycerides were unchanged. Plasma oxidized LDL, F2-isoprostanes, urinary 8-hydroxy-2'-deoxyguanosine, ex vivo ferric ion reducing capacity and thiobarbituric acid reactive substances in LDL were not affected by tea consumption compared with either placebo. Thus, inclusion of tea in a diet moderately low in fat reduces total and LDL cholesterol by significant amounts and may, therefore, reduce the risk of coronary heart disease. Tea consumption did not affect antioxidant status in this study.
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Our review aims to examine the cellular and molecular mechanisms of cardiovascular protection of green tea polyphenols, particularly epigallocatechin gallate (EGCG), which focuses on the anti-oxidative and anti-inflammatory effects. EGCG is the major and the most active component in green tea. Studies have shown that EGCG protects cellular damage by inhibiting DNA damage and oxidation of LDL. One of the protective properties of EGCG is its ability to scavenge free radicals. EGCG can also reduce the inflammatory response associated with local tissue injuries such as the hepatocellular necrosis in acute liver injury induced by carbon tetrachloride. The protective effect of EGCG is due to its ability to decrease lipid peroxidation, oxidative stress and the production of nitric oxide (NO) radicals by inhibiting the expression of iNOS. EGCG also ameliorates the overproduction of pro-inflammatory cytokines and mediators, reduces the activity of NF-kappaB and AP-1 and the subsequent formation of peroxynitrite with NO and reactive oxygen species. Thus, EGCG effectively mitigates cellular damage by lowering the inflammatory reaction and reducing the lipid peroxidation and NO generated radicals leading to the oxidative stress. Green tea is proposed to be a dietary supplement in the prevention of cardiovascular diseases in which oxidative stress and proinflammation are the principal causes.
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Theaflavins (TF) and thearubigins (TR) are the most exclusive polyphenols of black tea. Even though few previous reports showed the anticancer effects of TF through apoptosis, the potential effect of TR has not been appraised. This study investigated the induction of apoptosis in human skin cancer cells after treatment of TF and TR. We report that both TF and TR could exert inhibition of A431 (human epidermoid carcinoma) and A375 (human malignant melanoma) cell proliferation without adversely affecting normal human epidermal keratinocyte cells. Growth inhibition of A375 cells occurred through apoptosis, as evident from cell cycle arrest at G(0)/G(1) phase, increase in early apoptotic cells, externalization of phosphatidylserine and DNA fragmentation. In our pursuit to dissect the molecular mechanism of TF- and TR-induced apoptosis in A375 cells, we investigated whether cell death is being mediated by mitochondria. In our system, Bax translocation to mitochondria persuaded depolarization of mitochondrial membrane potential, cytochrome c release in cytosol and induced activation of caspase-9, caspase-3 and poly (ADP-ribose) polymerase cleavage. Our intricate investigations on apoptosis also explained that TF and TR augmented Bax:Bcl2 ratio, up-regulated the expression of p53 as well as p21 and inhibited phosphorylation of the cell survival protein Akt. Furthermore, TF and TR elicited intracellular reactive oxygen species generation in A375 cells. These observations raise speculations that TF as well as TR might exert chemopreventive effect through cell cycle arrest and induction of apoptogenic signals via mitochondrial death cascade in human skin cancer cells.
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In the present study, we investigated the effects of sour cherry seed extract (SCSE) on a variety of systemic processes that contribute to general health and viability of human subjects. The experiments were conducted according to a double-blind protocol in which six healthy individuals were administered 250-mg/day SCSE for 14 days, while four were treated with placebo. Peripheral blood was collected before and after the treatment period. Samples were analyzed for levels of selected cells, enzymes, or metabolites. Subjects that received SCSE showed increases in the values of mean cell volume, serum transferrin, mean peroxidase index, and representation of peripheral blood lymphocytes. On the other hand, decreases were observed in circulating neutrophils and ferritin levels. Changes observed in the present study do not fit into a clear pattern that might yield additional in-depth understanding of SCSE-mediated alterations in physiologic responses. The most encouraging result of the present study is the absence of any indication of toxicity by subjects consuming the extract. Copyright © 2015 John Wiley & Sons, Ltd.
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Sour cherry seed extract (SCE) was evaluated for its capacity to inhibit lipopolysaccharide-treated human peripheral blood T cells expressing tumor necrosis factor-alpha, and the chemokine interleukin-8. Both proteins are diagnostic biomarkers for inflammatory pathologies. Peripheral blood leukocytes from 11 rheumatoid arthritis (RA) patients and 8 healthy control subjects were co-cultured for 24 h in lipopolysaccharide and the extract, then evaluated by flow cytometry for T cell activation and by enzyme-linked immunoassay for lymphocyte-associated heme oxygenase-1 (HO-1) expression. There was a dose-dependent decrease in expression of the immunophenotypes: CD3+TNF-α +, and CD3+IL8 + in cultures from RA patients to a greater extent than in cells from healthy participants. These results suggest that the extract may have a modulatory roll in RA and other inflammatory disorders via the induction of HO-1, thus abating oxidative stress and strengthening regulation of pro-inflammatory signaling pathways.
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Epigallocatechin-3-gallate (EGCG) is the most biologically active catechin in green tea. EGCG has been shown to have therapeutic effects in autoinflammatory diseases and obesity. Obesity is currently regarded-partly-as an inflammatory condition because of the inflammatory cytokines and higher Th1 cell differentiation detected in obese animal models and human cohort studies. In this work, the effects of EGCG on diet-induced obesity (DIO) mice and obese collagen-induced arthritis (CIA) mice were investigated. EGCG reduced the body weight and fat infiltration in liver tissue while improving serum lipid profiles in DIO mice. EGCG also induced a higher Treg/Th17 cell ratio in CD4(+) T-cell differentiation by decreasing the ratio of STAT3/STAT5 expression in DIO mice. EGCG was also effective in obese CIA mice. Reducing Th17 cells and increasing regulatory T (Treg) cells by affecting the STAT protein ratio were important effects of EGCG that might result in improved arthritic scores and levels of several inflammatory indicators. Thus, EGCG has an anti-inflammatory effect by suppressing STAT3 proteins and Th17-cell differentiation. EGCG thus shows promise for treating autoimmune conditions related to STAT3 or Th17 cells, such as metabolic syndrome, inflammatory arthritis, and some neoplastic diseases.
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As a typical matricellular protein, Thrombospondin (TSP)-1, binds to the structural matrix and regulates cellular behavior by modulating growth factor and cytokine signaling. Obesity and diabetes are associated with marked upregulation of TSP-1 in adipose tissue. We hypothesized that endogenous TSP-1 may play an important role in the pathogenesis of diet-induced obesity and metabolic dysfunction. Accordingly, we examined the effects of TSP-1 gene disruption on weight gain, adiposity and adipose tissue inflammation in mice receiving a high-fat diet (HFD - 60% fat, 20% carbohydrate), or a high-carbohydrate low-fat diet (HCLFD - 10% fat, 70% carbohydrate). HFD mice had significantly higher TSP-1 expression in perigonadal adipose tissue; TSP-1 was predominantly localized in the adipose interstitium. TSP-1 loss attenuated weight gain and fat accumulation in HFD and HCLFD groups. When compared with corresponding wildtype animals, TSP-1 null mice had decreased insulin levels, but exhibited elevated free fatty acid (FFA) and triglyceride levels suggesting impaired fatty acid uptake. TSP-1 loss did not affect adipocyte size and had no effect on adipose vascular density. However, TSP-1 null mice exhibited attenuated Tumor Necrosis Factor (TNF)- mRNA expression and reduced macrophage infiltration suggesting a role for TSP-1 in mediating obesity-associated inflammation. In vitro, TSP-1 enhanced proliferation of 3T3-L1 preadipocytes, but did not modulate inflammatory cytokine and chemokine synthesis. In conclusion, TSP-1 upregulation contributes to weight gain, adipose growth and to the pathogenesis of metabolic dysfunction. The effects of TSP-1 may involve stimulation of adipocyte proliferation, activation of inflammatory signaling and facilitated fatty acid uptake by adipocytes.
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Dyslipidemia and inflammation are well known causal risk factors the development of atherosclerosis. The interplay between lipid metabolism and inflammation at multiple levels in metabolic active tissues may exacerbate the development of atherosclerosis, and will be discussed in this review. Cholesterol, fatty acids and modified lipids can directly activate inflammatory pathways. In addition, circulating (modified) lipoproteins modulate the activity of leukocytes. Vice versa, proinflammatory signaling (i.e. cytokines) in pre-clinical models directly affects lipid metabolism. Whereas the main lipid-lowering drugs all have potent anti-inflammatory actions, the lipid-modulating actions of anti-inflammatory agents appear to be less straightforward. The latter have mainly been evaluated in pre-clinical models and in patients with chronic inflammatory diseases, which will be discussed. The clinical trials that are currently conducted to evaluate the efficacy of anti-inflammatory agents in the treatment of cardiovascular diseases may additionally reveal potential (beneficial) effects of these therapeutics on lipid metabolism in the general population at risk for CVD.
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The present study evaluates a hypothesis that sour cherry (Prunus cerasus) seed extracts (SCE) modulate CD3+ T lymphocyte activity in ways predictive of potential for uses of SCE in management of inflammatory diseases. Peripheral blood mononuclear cells (PBMC) from 12 type 2 diabetes (T2DM) patients and eight healthy control subjects were cultured 24 h with 100 ng/ml lipopolysaccharide (LPS) to increase inflammatory signaling and co-incubated with 0.5-100 µg/ml SCE. Cultures were evaluated by two-color flow cytometry for percent representation of CD3+ IL8+ and CD3 + TNF-α + cells which express interleukin-8 (IL-8), and tumor necrosis factor-, (TNF-α+) respectively, and by enzyme-linked immunoassay for lymphocyte-associated heme oxygenase-1 (HO-1, known to be induced by SCE). SCE dosage ranges of 0.5-100 µg/ml in cell cultures significantly suppressed LPS-increased CD3 + TNF-α + and CD3 + IL8+ representation from all participants (p < 0.05), with greater pharmacological effect noted in suppression of CD3 + TNF-α + noted in cells from T2DM patients versus healthy control subjects. These effects correlated with increased HO-1 expression in SCE-treated PBMC from all subjects (p < 0.05). Since TNF-α and IL-8 are diagnostic/prognostic biomarkers for many inflammatory syndromes, the capacity of SCE to down-regulate representation of cells that express them suggests potential for therapeutic use of SCE in T2DM and other diseases. Copyright © 2012 John Wiley & Sons, Ltd.
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We investigated in vitroinhibition of mammalian carbohydrate-degrading enzymes by green tea extract and the component catechins, and further evaluated their inhibitory activities in cell cultures. The extract showed good inhibition toward rat intestinal maltase and rabbit glycogen phosphorylase (GP) b, with IC50 values of 45 and 7.4 μg/ml, respectively. The polyphenol components, catechin 3-gallate (CG), gallocatechin 3-gallate (GCG), epicatechin 3-gallate (ECG), and epigallocatechin 3-gallate (EGCG), were good inhibitors of maltase, with IC50 values of 62, 67, 40, and 16 μM, respectively, and EGCG also showed good inhibition toward maltase expressed on Caco-2 cells, with an IC50 value of 27 μM. The ungallated catechins, such as catechin, gallocatechin (GC), epicatechin (EC), and epigallocatechin (EGC), showed no significant inhibition toward GP b, whereas the gallated catechins CG, GCG, ECG, and EGCG inhibited the enzyme, with IC50 values of 35, 6.3, 27, and 34 μM. From multiple inhibition studies by Dixon plots, GCG appears to bind a new allostelic site, the indole inhibitor site. These gallated catechins also inhibited glucagon-stimulated glucose production dose-dependently, with IC50 values ranging from 33 to 55 μM. Dietary supplementation with these gallated catechins or the green tea extract containing them, which inhibits both α-glucosidases and GP in vitro and in cell culture, would contribute to the protection or improvement of type 2 diabetes.
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A(−)-epicatechin (EC) and (−)-epigallocatechin (EGC) mixture and a mixture of their gallates (ECG and EGCG, respectively) markedly lowered lymphatic cholesterol absorption in rats with a cannulated thoracic duct. A mixture of ECG and EGCG was more effective in reducing cholesterol absorption than the EC and EGC mixture. These catechins also tended to decrease lymphatic absorption of triacylglycerols, although not so pronounced as in cholesterol absorption. An in vitro study on micellar solubility of cholesterol showed that these catechin mixtures precipitated cholesterol solubilized in mixed bile salt micelles in a dose-dependent manner. A mixture of ECG and EGCG more effectively precipitated micellar cholesterol than a mixture of EC and EGC. When purified EC, EGC, ECG and EGCG were used, EGCG was more effective in precipitating micellar cholesterol than ECG. The effect of EC and EGC was comparable and weaker than their gallate esters. The bile acid concentration in the micelles was not affected by these catechins. A positive correlation was observed between the amount of coprecipitated EGCG and cholesterol. These results clearly show that tea catechins, in particular their gallate esters, effectively reduce cholesterol absorption from the intestine by reducing solubility of cholesterol in mixed micelles. The observation accounts for the hypocholesterolemic effect of tea catechins.
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Regulatory T cells (Treg) are critical in maintaining immune tolerance and suppressing autoimmunity. The transcription factor Foxp3 serves as a master switch that controls the development and function of Treg. Foxp3 expression is epigenetically regulated by DNA methylation, and DNA methyltransferase (DNMT) inhibitors can induce Foxp3 expression in naive CD4(+) T cells. We showed that EGCG, a major green tea polyphenol, could act as a dietary DNMT inhibitor, and induced Foxp3 and IL-10 expression in CD4(+) Jurkat T cells at physiologically relevant concentrations in vitro. We further showed that mice treated with EGCG in vivo had significantly increased Treg frequencies and numbers in spleen and lymph nodes and had inhibited T cell response. Induction of Foxp3 expression correlated with a concomitant reduction in DNMT expression and a decrease in global DNA methylation. Our data suggested that EGCG can induce Foxp3 expression and increase Treg frequency via a novel epigenetic mechanism. While the DNMT inhibitory effects of EGCG was not as potent as pharmacologic agents such as 5-aza-2'-deoxycytidine, the ability of dietary agents to target similar mechanisms offers opportunities for potentially sustained and longer-term exposures with lower toxicity. Our work provides the foundation for future studies to further examine and evaluate dietary strategies to modulate immune function.
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In the present study, the efficacy of black tea (BT) and green tea (GT) was studied in relation to serum and hepatic oxidative abnormalities in hypercholesterolemic rats. Hypercholesterolemia was induced in male Wistar rats (8 week old) by feeding them with a high-cholesterol diet (HCD) for 35 days. The experimental rats were given BT and GT as a supplement (7 g/L) via drinking water. Increased hepatic and serum lipid profile along with abnormalities in oxidative marker, with a concomitant increase in the body weight, food intake, and food efficiency, were seen in hypercholesterolemic rats. Following the supplementation of BT and GT to rats fed with HCD, significantly lower levels of serum and hepatic cholesterol, triglycerides, serum low-density lipoprotein cholesterol, and increased high-density lipoprotein cholesterol levels were observed, when compared with hypercholesterolemic group. Further, significantly lower levels in the serum and hepatic lipid peroxidation, body weight gain, and food efficiency were observed in BT and GT group when compared with control and HCD fed group. However, no such significant changes were observed in the food intake upon supplementation with BT and GT. These results suggest that supplementation of BT and GT may protect against the serum and hepatic abnormalities in hypercholesterolemic rats.
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Cholesterol promotes Th2 immunity and allergic inflammation in rodents; whether this occurs in humans is unclear. Reports of both direct and inverse associations between serum cholesterol and atopy in different populations suggest that race and/or other demographic variables may modify these relationships. Aims OF THE STUDY: To determine the relationships between levels of three serum cholesterol measures [total cholesterol (TC), high density lipoprotein-cholesterol (HDL-C), and non-HDL-C] and atopy in a sample representative of the US population. Cross-sectional study of 6854 participants aged > or =6 years from the 2005-2006 National Health and Nutrition Examination Survey. In the overall population, adjusted odds ratios (AORs) per two-standard deviation increase in TC and non-HDL-C for biochemical atopy (defined as > or =1 allergen-specific IgE to 19 allergens) were 1.17 [95% confidence interval (CI), 1.00-1.38] and 1.19 (95% CI, 1.03-1.39), respectively. Interactions by race were noted for the two relationships (interaction P = 0.004 and P = 0.009, respectively) with non-Hispanic Whites (NHWs) having direct relationships [TC: AOR 1.27 (95% CI, 1.03-1.57); non-HDL-C: AOR 1.27 (95% CI, 1.03-1.56)] and non-Hispanic Blacks (NHBs) inverse relationships [TC: AOR 0.77 (95% CI, 0.62-0.95); non-HDL-C: AOR 0.86 (95% CI, 0.69-1.08)]. The adjusted HDL-C-atopy relationship was nonsignificant for NHWs and inverse for NHBs [AOR 0.77 (95% CI, 0.61-0.96)]. Relationships were independent of body mass index and serum C-reactive protein and unmodified by corticosteroid or statin usage. Results were similar using current hay fever/allergy as the atopy outcome. There are marked inter-racial differences in the relationship between serum cholesterol and atopy in the US population.
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Craig ME, Hattersley A, Donaghue KC. Definition, epidemiology and classification of diabetes in children and adolescents.
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The effects of black tea extract (BTE) and some of its pure phenolics on human peripheral blood mononuclear cell (PBMC) cytokine secretion were examined in vitro. The main steps of the study included chromatographic analysis of BTE and commercial green tea extract, Polyphenon 60, determination of the total antioxidant capacity of both the extracts and their phenolics, and finally evaluation of their effects on PBMCs. Four major peaks in the chromatogram of BTE belonged to caffeine, gallic acid, epigallocatechin and epigallocatechin gallate, and the latter showed the highest antioxidant capacity. While pure phenolics at the concentration of 20 mM did not significantly affect PBMC cytokine secretion, BTE and Polyphenon 60 suppressed interleukin-1 beta, tumor necrosis factor-alpha and interleukin-6. Interestingly, the secretion of interferon-gamma after 24 h was slightly, but significantly, boosted by the extracts. BTE has selective pro-inflammatory cytokine-suppressing effects on human PBMCs.
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Tea is grown in about 30 countries but is consumed worldwide, although at greatly varying levels. It is the most widely consumed beverage aside from water with a per capita worldwide consumption of approximately 0.12 liter per year. Tea is manufactured in three basic forms. Green tea is prepared in such a way as to preclude the oxidation of green leaf polyphenols. During black tea production oxidation is promoted so that most of these substances are oxidized. Oolong tea is a partially oxidized product. Of the approximately 2.5 million metric tons of dried tea manufactured, only 20% is green tea and less than 2% is oolong tea. Green tea is consumed primarily in China, Japan, and a few countries in North Africa and the Middle East. Fresh tea leaf is unusually rich in the flavanol group of polyphenols known as catechins which may constitute up to 30% of the dry leaf weight. Other polyphenols include flavanols and their glycosides, and depsides such as chlorogenic acid, coumarylquinic acid, and one unique to tea, theogallin (3-galloylquinic acid). Caffeine is present at an average level of 3% along with very small amounts of the other common methylxanthines, theobromine and theophylline. The amino acid theanine (5-N-ethylglutamine) is also unique to tea. Tea accumulates aluminum and manganese. In addition to the normal complement of plant cell enzymes, tea leaf contains an active polyphenol oxidase which catalyzes the aerobic oxidation of the catechins when the leaf cell structure is disrupted during black tea manufacture. The various quinones produced by the enzymatic oxidations undergo condensation reactions which result in a series of compounds, including bisflavanols, theaflavins, epitheaflavic acids, and thearubigens, which impart the characteristic taste and color properties of black tea. Most of these compounds readily form complexes with caffeine. There is no tannic acid in tea. Thearubigens constitute the largest mass of the extractable matter in black tea but their composition is not well known. Proanthocyanidins make up part of the complex. Tea peroxidase may be involved in their generation. The catechin quinones also initiate the formation of many of the hundreds of volatile compounds found in the black tea aroma fraction. Green tea composition is very similar to that of the fresh leaf except for a few enzymatically catalyzed changes which occur extremely rapidly following plucking. New volatile substances are produced during the drying stage. Oolong tea is intermediate in composition between green and black teas.
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Alpha-glucosidase inhibitors are antihyperglycemic agents that lower blood glucose by delaying the digestion and absorption of complex carbohydrates. They are competitive inhibitors of the enzymes in the brush border of enterocytes that cleave eligosaccharides to monosaccharides. Their major action is to reduce the rise of postprandial plasma glucose. In non-insulin-dependent diabetes mellitus patients, these inhibitors decrease postprandial plasma glucose by 40 to 50 mg/dL and hemoglobin A1C by 0.5% to 1.0%.
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Epidemiologic studies suggest an inverse association of tea consumption with cardiovascular disease. The antioxidant effects of flavonoids in tea (including preventing oxidative damage to LDL) are among the potential mechanisms that could underlie the protective effects. Other possible mechanisms include attenuating the inflammatory process in atherosclerosis, reducing thrombosis, promoting normal endothelial function, and blocking expression of cellular adhesion molecules. Cocoa and chocolate can also be rich sources of flavonoids. Flavanols and procyanidins isolated from cocoa exhibit strong antioxidant properties in-vitro. In acute feeding studies, flavanol-rich cocoa and chocolate increased plasma antioxidant capacity and reduced platelet reactivity. Based on limited data, approximately 150 mg of flavonoids is needed to trigger a rapid antioxidant effect and changes in prostacyclin. Some dose-response evidence demonstrates an antioxidant effect with approximately 500 mg flavonoids. Brewed tea typically contains approximately 172 mg total flavonoids per 235 ml (brewed for 2 min); hence, consumption of 1 and 3.5 cups of tea would be expected to elicit acute and chronic physiologic effects, respectively. Chocolate is more variable with some products containing essentially no flavonoids (0.09 mg procyanidin/g), whereas others are high in flavonoids (4 mg procyanidin/g). Thus, approximate estimates of flavonoid rich chocolate needed to exert acute and chronic effects are 38 and 125 g, respectively. Collectively, the antioxidant effects of flavonoid-rich foods may reduce cardiovascular disease risk.
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The most widely known health benefits of tea relate to the polyphenols as the principal active ingredients in protection against oxidative damage and in antibacterial, antiviral, anticarcinogenic, and antimutagenic activities, but polyphenols in tea may also increase insulin activity. The objective of this study was to determine the insulin-enhancing properties of tea and its components. Tea, as normally consumed, was shown to increase insulin activity >15-fold in vitro in an epididymal fat cell assay. Black, green, and oolong teas but not herbal teas, which are not teas in the traditional sense because they do not contain leaves of Camellia senensis, were all shown to increase insulin activity. High-performance liquid chromatography fractionation of tea extracts utilizing a Waters SymmetryPrep C18 column showed that the majority of the insulin-potentiating activity for green and oolong teas was due to epigallocatechin gallate. For black tea, the activity was present in several regions of the chromatogram corresponding to, in addition to epigallocatechin gallate, tannins, theaflavins, and other undefined compounds. Several known compounds found in tea were shown to enhance insulin with the greatest activity due to epigallocatechin gallate followed by epicatechin gallate, tannins, and theaflavins. Caffeine, catechin, and epicatechin displayed insignificant insulin-enhancing activities. Addition of lemon to the tea did not affect the insulin-potentiating activity. Addition of 5 g of 2% milk per cup decreased the insulin-potentiating activity one-third, and addition of 50 g of milk per cup decreased the insulin-potentiating activity approximately 90%. Nondairy creamers and soy milk also decreased the insulin-enhancing activity. These data demonstrate that tea contains in vitro insulin-enhancing activity and the predominant active ingredient is epigallocatechin gallate.
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Polyphenolic components of green tea, such as epigallocatechin-3-gallate (EGCG), have potent anti-inflammatory properties. We previously showed that EGCG inhibits tumor necrosis factor-alpha (TNF-alpha)-mediated activation of the nuclear factor-kappa B (NF-kappa B) pathway, partly through inhibition of I kappa B kinase (IKK). The NF-kappa B pathway may also be activated in response to interleukin-1 beta (IL-1 beta) stimulation through a distinct signal transduction pathway. We therefore hypothesized that EGCG inhibits IL-1 beta-mediated activation of the NF-kappa B pathway. Because the gene expression of interleukin-8 (IL-8), the major human neutrophil chemoattractant, is dependent on activation of NF-kappa B, IL-8 gene expression in human lung epithelial (A549) cells treated with human IL-1 beta was used as a model of IL-1 beta signal transduction. The EGCG markedly inhibited IL-1 beta-mediated IL-1 beta receptor-associated kinase (IRAK) degradation and the signaling events downstream from IRAK degradation: IKK activation, I kappa B alpha degradation, and NF-kappa B activation. In addition, EGCG inhibited phosphorylation of the p65 subunit of NF-kappa B. The functional consequence of this inhibition was evident by inhibition of IL-8 gene expression. Therefore, the green tea polyphenol EGCG is a potent inhibitor of IL-1 beta signal transduction in vitro. The proximal mechanisms of this effect involve inhibition of IRAK-dependent signaling and phosphorylation of p65.
The IFCC has established a working group on HbA1c standardization, which developed a reference system to act as basis for global standardization of all glycohemoglobin/HbA1c assays. The reference system is based on HbA1c, defined as beta-N-1-deoxy fructosyl haemoglobin as component. Two reference methods specifically measure the glycated N-terminal residue of the beta chain of haemoglobin. The assay principle is peptide mapping after proteolytic cleavage of the molecule followed by measurement of the ratio of the glycated and non-glycated ss-N-terminal hexapeptides by HPLC/MS or HPLC/CE. An international network of 12 reference laboratories is in place. An overall CV below 2% is achieved in comparison studies, which guarantees a reliable value assignment to secondary reference materials. For implementation of the system, the relationship between IFCC and the existing Designated Comparison Methods in the US (NGSP), Sweden (MonoS) and Japan was calculated in seven method comparisons. In all cases, the correlation was exactly the same, making recalculation of the various systems to one IFCC reference system possible. IFCC values will be a reference range of 3-4% HbA1c with a target value of optimal treatment of 5% and change of therapy proposed at values >6%. The last item of the IFCC WG on HbA1c standardization is the adjustment of all the commercial methods to this new reference system. Three method comparison studies with all the major manufacturer methods were performed. This allowed us to first anchor all commercial methods to the IFCC reference system and thereafter recalculate the results to the new IFCC system. Secondary reference materials and a transfer protocol are provided to enable manufacturers to adjust their routine tests to the new reference system. The IFCC reference system for HbA1c will make it possible to improve the performance of routine HbA1c assays. The goal of this improved analytical performance is a within and between run CV of 2%. If this can be achieved, then the HbA1c results can be incorporated into the diagnostic strategies for detecting diabetes mellitus.
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In diabetes (type 1 and type 2), increased flux of free fatty acids and glucose is associated with increased mitochondrial reactive oxygen species (ROS) production and, as a consequence, increased oxidative stress. ROS have been shown to activate various cellular stress-sensitive pathways, which can interfere with cellular signaling pathways. Exposure of different cell lines to micromolar concentrations of hydrogen peroxide leads to the activation of stress kinases such as c-Jun N-terminal kinase, p38, I kappaB kinase, and extracellular receptor kinase 1/2. This activation is accompanied by a down-regulation of the cellular response to insulin, leading to a reduced ability of insulin to promote glucose uptake, and glycogen and protein synthesis. The mechanisms leading to this down-regulation in oxidized cells are complicated, involving increased serine/threonine phosphorylation of insulin receptor substrate-1 (IRS1), impaired insulin-stimulated redistribution of IRS1 and phosphatidylinositol-kinase between cytosol and low-density microsomal fraction, followed by a reduced protein kinase-B phosphorylation and GLUT4 translocation to the plasma membrane. In addition, prolonged exposure to ROS affects transcription of glucose transporters: whereas the level of GLUT1 is increased, GLUT4 level is reduced. As can be expected, administration of antioxidants such as lipoic acid in oxidized cells, in animal models of diabetes, and in type 2 diabetes shows improved insulin sensitivity. Thus, oxidative stress is presently accepted as a likely causative factor in the development of insulin resistance.
Article
Tea polyphenols have been shown to protect against carbon tetrachloride (CCl4)-induced liver injury, liver fibrosis, hepatic ischemia-reperfusion injury. In this study, we examined the effect of tea polyphenols on lipopolysaccharide (LPS)-induced liver injury, and explored its mechanisms. Sprague-Dawley rats received tea polyphenols (100 mg.kg-1.d-1) or vehicle (water) intragastrically by gavage for 14 days, followed by LPS (5 mg/kg) or saline injection intraperitoneally. Liver injury was assessed by biochemical assay and pathological analysis. Serum tumor necrosis factor-alpha (TNF-alpha) levels and liver malondialdehyde (MDA) contents were determined. Inducible nitric oxide synthase (iNOS) protein and TNF-alpha, iNOS and endothelial nitric oxide synthase (eNOS) mRNA expressions in the liver were detected by immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. Administration of LPS resulted in liver injury in rats, evidenced by elevated activities of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), hepatocellular necrosis, and neutrophil infiltration in the liver. These responses were associated with increased serum TNF-alpha levels, induced iNOS protein, expressions of TNF-alpha, iNOS mRNA in the liver and elevated lipid peroxidation at 90 minutes or 6 hours after LPS injection. Pretreatment with tea polyphenols attenuated LPS-induced liver injury, and blunted the rises of serum TNF-alpha levels and lipid peroxidation and the induction of expressions of TNF-alpha, iNOS in the liver. Tea polyphenols prevent LPS-induced liver injury, and the mechanisms may involve the reduction of serum TNF-alpha levels and lipid peroxidation and the suppression of TNF-alpha, iNOS expressions in the liver.
Article
In vitro studies suggest that extracts of black, green, and mulberry teas could interfere with carbohydrate and triacylglycerol absorption via their ability to inhibit alpha-amylase, alpha-glucosidase, sodium-glucose transporters, and pancreatic lipase. We measured breath hydrogen and 13CO2 to investigate the ability of an extract of black, green, and mulberry tea leaves to induce malabsorption of carbohydrate and triacylglycerol in healthy volunteers. In a crossover design, healthy adult volunteers randomly ingested test meals with a placebo beverage or a preparation containing an extract of black (0.1 g), green (0.1 g), and mulberry (1.0 g) teas. One test meal contained 50 g carbohydrate as white rice, 10 g butter, and 0.2 g [13C]triolein, and the beverages contained 10 g sucrose. The calorie content of the second test meal consisted entirely of lipid (30 g olive oil and 0.2 g [13C]triolein). Breath-hydrogen and 13CO2 concentrations were assessed hourly for 8 h, and symptoms were rated on a linear scale. With the carbohydrate-containing meal, the tea extract resulted in a highly significant increase in breath-hydrogen concentrations, which indicated appreciable carbohydrate malabsorption. A comparison of hydrogen excretion after the carbohydrate-containing meal with that after the nonabsorbable disaccharide lactulose suggested that the tea extract induced malabsorption of 25% of the carbohydrate. The tea extract did not cause triacylglycerol malabsorption or any significant increase in symptoms. This study provides the basis for additional experiments to determine whether the tea extract has clinical utility for the treatment of obesity or diabetes.
Article
Epigallocatechin-3-gallate (EGCG) is a major form of tea catechin and has a variety of biological activities. In the present study, we investigated the effect of EGCG on the secretion of TNF-alpha, IL-6 and IL-8, as well as its possible mechanism of action by using the human mast cell line (HMC-1). EGCG was treated before the activation of HMC-1 cells with phorbol 12-myristate 13-acetate (PMA) plus calcium ionophore (A23187). To investigate the effect of EGCG on PMA+A23187-stimulated HMC-1 cells, ELISA, Western blot analysis, electrophorectic mobility shift assay and luciferase assay were used in this study. EGCG (100 microM) inhibited PMA+A23187-induced TNF-alpha, IL-6 and IL-8 expression and production. EGCG inhibited the intracellular Ca(2+) level. EGCG attenuated PMA+A23187-induced NF-kappaB and extracellular signal-regulated kinase (ERK1/2) activation, but not that of c-Jun N-terminal kinase or p38 mitogen-activated protein kinase. EGCG inhibited the production of TNF-alpha, IL-6 and IL-8 through the inhibition of the intracellular Ca(2+) level, and of ERK1/2 and NF-kappaB activation. These results indicate that EGCG may be helpful in regulating mast-cell-mediated allergic inflammatory response.
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Patients with type 2 diabetes mellitus and/or the metabolic syndrome have considerable cardiovascular risk. Treatment with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) and with antihypertensive and some antihyperglycemic agents reduces this risk, but residual macrovascular morbidity and mortality persist, even in patients assigned to intensive multifactorial intervention programs. Therapeutic strategies that target inflammation and lipid abnormalities not well addressed by statins may offer additional opportunities for improving the prognosis of these patients. Inflammation, a key mechanism of atherogenesis, appears to have particular relevance to diabetic vascular complications, as well as in the development of diabetes itself. Oxidative stress and hyperglycemia also figure among the pathogenic factors that promote cardiovascular complications in patients with the metabolic syndrome and/or diabetes and may augment the ongoing inflammation. Peroxisome proliferator-activated receptor (PPAR)-alpha and PPAR-gamma, members of the nuclear receptor family, form ligand-activated transcription factors that regulate key important metabolic pathways. PPARs have become therapeutic targets through the use of the fibrate class of antidyslipidemic drugs (PPAR-alpha) and the insulin-sensitizing thiazolidinediones (PPAR-gamma). The activation of these PPARs may also suppress inflammation and atherosclerosis. Recent clinical trials (Fenofibrate Intervention and Event Lowering in Diabetes [FIELD], Prospective Pioglitazone Clinical Trial in Macrovascular Events [PROactive]) have considered the impact of these PPAR agonists on cardiovascular disease, with mixed effects that require careful analysis, especially given ongoing trials and additional PPAR agonists in development.
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Epigallocatechin-3-gallate inhibits secretion of TNF-alpha, IL-6 and IL-8 through the attenuation of ERK and NF-kappaB in HMC-1 cells
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BLACK TEA AFFECTS CYTOKINES IN DIABETES Copyright © 2015 John Wiley & Sons, Ltd. Phytother. Res. (2015)
Epigallocatechin-3-gallate inhibits secretion of TNF-alpha, IL-6 and IL-8 through the attenuation of ERK and NF-kappaB in HMC-1 cells
  • Hin
Inhibition of prostate carcinogenesis in TRAMP mice by oral infusion of green tea polyphenols
  • Gupta