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Fang Y, Wang J, Cao Y, Liu W, Duan L, Hu J, Peng J. The Antiobesity Effects and Potential Mechanisms of Theaflavins. J Med Food 2024; 27:1-11. [PMID: 38060708 DOI: 10.1089/jmf.2023.k.0180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2024] Open
Abstract
Theaflavins are the characteristic polyphenols in black tea which can be enzymatically synthesized. In this review, the effects and molecular mechanisms of theaflavins on obesity and its comorbidities, including dyslipidemia, insulin resistance, hepatic steatosis, and atherosclerosis, were summarized. Theaflavins ameliorate obesity potentially via reducing food intake, inhibiting pancreatic lipase to reduce lipid absorption, activating the adenosine monophosphate-activated protein kinase (AMPK), and regulating the gut microbiota. As to the comorbidities, theaflavins ameliorate hypercholesterolemia by inhibiting micelle formation to reduce cholesterol absorption. Theaflavins improve insulin sensitivity by increasing the signaling of protein kinase B, eliminating glucose toxicity, and inhibiting inflammation. Theaflavins ameliorate hepatic steatosis via activating AMPK. Theaflavins reduce atherosclerosis by upregulating nuclear factor erythropoietin-2-related factor 2 signaling and inhibiting plasminogen activator inhibitor 1. In randomized controlled trails, black tea extracts containing theaflavins reduced body weight in overweight people and improved glucose tolerance in healthy adults. The amelioration on the hyperlipidemia and the prevention of coronary artery disease by black tea extracts were supported by meta-analysis.
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Affiliation(s)
- Yi Fang
- Department of Nephropathy, The Seventh People's Hospital affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
- Institute of Liver diseases, Shuguang Hospital affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Jun Wang
- Institute of Liver diseases, Shuguang Hospital affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yu Cao
- Department of Nephropathy, The Seventh People's Hospital affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Wenrui Liu
- Department of Nephropathy, The Seventh People's Hospital affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Lianxiang Duan
- Department of Nephropathy, The Seventh People's Hospital affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Jing Hu
- Department of Nephropathy, The Seventh People's Hospital affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Jinghua Peng
- Institute of Liver diseases, Shuguang Hospital affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
- Key Laboratory of Liver and Kidney Diseases (Shanghai University of Traditional Chinese Medicine), Ministry of Education of China, Shanghai, China
- Shanghai Key Laboratory of Traditional Chinese Clinical Medicine, Shanghai, China
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Sidhu D, Vasundhara M, Dey P. The intestinal-level metabolic benefits of green tea catechins: Mechanistic insights from pre-clinical and clinical studies. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2024; 123:155207. [PMID: 38000106 DOI: 10.1016/j.phymed.2023.155207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 10/11/2023] [Accepted: 11/08/2023] [Indexed: 11/26/2023]
Abstract
BACKGROUND The intestinal-level host-microbiota interaction has been implicated in the pathogenesis of chronic diseases. The current review is intended to provide a comprehensive insight into deciphering whether intestinal-level bioactivities mediate the overall metabolic health benefits of green tea catechins. PURPOSE We have comprehensively discussed pre-clinical and clinical evidences of intestinal-level changes in metabolism, microbiota, and metabolome due to catechin-rich green tea treatments, ultimately limiting metabolic diseases. Exclusive emphasis has been given to purified catechins and green tea, and discussions on extraintestinal mechanisms of metabolic health benefits were avoided. METHODS A literature search for relevant pre-clinical and clinical studies was performed in various online databases (e.g., PubMed) using specific keywords (e.g., catechin, intestine, microbiota). Out of all the referred literature, ∼15% belonged to 2021-2023, ∼51% were from 2011-2020, and ∼32% from 2000-2010. RESULT The metabolic health benefits of green tea catechins are indeed influenced by the intestinal-level bioactivities, including reduction of mucosal inflammation and oxidative stress, attenuation of gut barrier dysfunction, decrease in intestinal lipid absorption and metabolism, favorable modulation of mucosal nuclear receptor signaling, alterations of the luminal global metabolome, and mitigation of the gut dysbiosis. The results from the recent clinical studies support the pre-clinical evidences. The challenges and pitfalls of the currently available knowledge on catechin bioactivities have been discussed, and constructive directions to harness the translational benefits of green tea through future interventions have been provided. CONCLUSION The metabolism, metabolome, and microbiota at the intestinal epithelia play critical roles in catechin metabolism, pharmacokinetics, bioavailability, and bioactivities. Especially the reciprocal interaction between the catechins and the gut microbiota dictates the metabolic benefits of catechins.
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Affiliation(s)
- Dwinder Sidhu
- Department of Biotechnology, Thapar Institute of Engineering & Technology, Patiala 147004, India
| | - M Vasundhara
- Department of Biotechnology, Thapar Institute of Engineering & Technology, Patiala 147004, India.
| | - Priyankar Dey
- Department of Biotechnology, Thapar Institute of Engineering & Technology, Patiala 147004, India.
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Wang K, Wu J, Chen S, Zhao H, He P, Tu Y, Li B. Transcriptome analysis provides insights into the anti-diabetic mechanism of theaflavins in high-fat diet and streptozotocin-induced mice. Food Funct 2022; 13:2033-2043. [DOI: 10.1039/d1fo03856g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Black tea exhibits potential to improve hyperglycemia and insulin resistance, and theaflavins (TFs) are one of its characteristic components. The aim of this study was to explore the anti-diabetic mechanism...
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Deineka L, Zhakiyanova A, Amrenova Y, Blinova I. Tea Antioxidants. BIO WEB OF CONFERENCES 2021. [DOI: 10.1051/bioconf/20213002003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In thе paper, antioxidant activity (AOA) of tea infusions as a function of infusion time and type or brand of teas as well as a concentration of caffeine were measured. The main components of green tea infusions are identified as epigallocatechin gallate (EGCG), epicatechin gallate (ECG), and caffeine. It has been shown that the antioxidant activity depends on the time of infusion and the degree of tea grinding. while there is a linear dependence between AOA and concentration of caffeine in tea. Thus the only method to reduce content of caffeine in the infusion is a preliminary withdrawal of caffeine from the plant material
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The Intrinsic Virtues of EGCG, an Extremely Good Cell Guardian, on Prevention and Treatment of Diabesity Complications. Molecules 2020; 25:molecules25133061. [PMID: 32635492 PMCID: PMC7411588 DOI: 10.3390/molecules25133061] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 07/01/2020] [Accepted: 07/02/2020] [Indexed: 12/19/2022] Open
Abstract
The pandemic proportion of diabesity—a combination of obesity and diabetes—sets a worldwide health issue. Experimental and clinical studies have progressively reinforced the pioneering epidemiological observation of an inverse relationship between consumption of polyphenol-rich nutraceutical agents and mortality from cardiovascular and metabolic diseases. With chemical identification of epigallocatechin-3-gallate (EGCG) as the most abundant catechin of green tea, a number of cellular and molecular mechanisms underlying the activities of this unique catechin have been proposed. Favorable effects of EGCG have been initially attributed to its scavenging effects on free radicals, inhibition of ROS-generating mechanisms and upregulation of antioxidant enzymes. Biologic actions of EGCG are concentration-dependent and under certain conditions EGCG may exert pro-oxidant activities, including generation of free radicals. The discovery of 67-kDa laminin as potential EGCG membrane target has broaden the likelihood that EGCG may function not only because of its highly reactive nature, but also via receptor-mediated activation of multiple signaling pathways involved in cell proliferation, angiogenesis and apoptosis. Finally, by acting as epigenetic modulator of DNA methylation and chromatin remodeling, EGCG may alter gene expression and modify miRNA activities. Despite unceasing research providing detailed insights, ECGC composite activities are still not completely understood. This review summarizes the most recent evidence on molecular mechanisms by which EGCG may activate signal transduction pathways, regulate transcription factors or promote epigenetic changes that may contribute to prevent pathologic processes involved in diabesity and its cardiovascular complications.
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Kutan Fenercioglu A, Saler T, Genc E, Altuntaş Y. The Relationship of Oxidative and Metabolic Parameters With Hemoglobin A1c in Type 2 Diabetes Mellitus. ANKARA MEDICAL JOURNAL 2019. [DOI: 10.17098/amj.651971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Pharmacological values and therapeutic properties of black tea (Camellia sinensis): A comprehensive overview. Biomed Pharmacother 2018; 100:521-531. [PMID: 29482046 DOI: 10.1016/j.biopha.2018.02.048] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Revised: 02/10/2018] [Accepted: 02/13/2018] [Indexed: 01/06/2023] Open
Abstract
Medicinal plants are essential parts of traditional medicine due to their phytochemical constituents having pharmacological values and therapeutic applications. Black tea have thousands of various biological compounds such as flavonoids (Thearubigins (TRs) and theaflavins (TFs) and catechins), amino acids (L.theanine), vitamins (A, C, K), phenolic acids (caffeic acid (CA), gallic acid (GA), chlorogenic acids (CGA) and cauramic acid), lipids, proteins, volatile compounds carbohydrates, β-carotene and fluoride that illustrated many promising pharmacological effects regarded as growth promoter, cardioprotector, potent cholesterol-lowering effect, antioxidant and antimicrobial, etc inhuman. Although there is an exponential growth in molecular evidence of cholesterol-lowering and antioxidant effect in human, there is still a lack of information of the pharmacological effects of black tea. To fill this information gap, therefore, this review article underscores broadening the new insight pertaining to black tea that could be used as safe food additive. This article also illuminates the interesting role of black tea as an herbal medicine that is the future demand to get rid of synthetic health promoters in the human health practice. Moreover, this information would be useful in terms of the low-cost practice of natural medicines with no residual effects, and a natural protection of the human being. In addition, further studies at a molecular level are needed to reveal its mechanism of action particularly for the hypocholesterolemic effect of black tea to overcome the heart-related diseases, fewer side effects and being a natural safeguard of human health.
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Hua F, Zhou P, Wu HY, Chu GX, Xie ZW, Bao GH. Inhibition of α-glucosidase and α-amylase by flavonoid glycosides from Lu'an GuaPian tea: molecular docking and interaction mechanism. Food Funct 2018; 9:4173-4183. [DOI: 10.1039/c8fo00562a] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Inhibition of α-glucosidase and α-amylase by flavonoid glycosides from Lu'an GuaPian tea.
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Affiliation(s)
- Fang Hua
- Natural Products Laboratory
- International Joint Laboratory of Tea Chemistry and Health Effects
- State Key Laboratory of Tea Plant Biology and Utilization
- Anhui Agricultural University
- Hefei
| | - Peng Zhou
- Department of Integrated Traditional Chinese and Western Medicine
- Anhui University of Chinese Medicine
- Research Institute of Integrated Traditional Chinese and Western Medicine
- Anhui Academy of Chinese Medicine
- Hefei 230038
| | - Hao-Yue Wu
- Natural Products Laboratory
- International Joint Laboratory of Tea Chemistry and Health Effects
- State Key Laboratory of Tea Plant Biology and Utilization
- Anhui Agricultural University
- Hefei
| | - Gang-Xiu Chu
- Natural Products Laboratory
- International Joint Laboratory of Tea Chemistry and Health Effects
- State Key Laboratory of Tea Plant Biology and Utilization
- Anhui Agricultural University
- Hefei
| | - Zhong-Wen Xie
- Natural Products Laboratory
- International Joint Laboratory of Tea Chemistry and Health Effects
- State Key Laboratory of Tea Plant Biology and Utilization
- Anhui Agricultural University
- Hefei
| | - Guan-Hu Bao
- Natural Products Laboratory
- International Joint Laboratory of Tea Chemistry and Health Effects
- State Key Laboratory of Tea Plant Biology and Utilization
- Anhui Agricultural University
- Hefei
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Ameliorative role of ethyl-acetate fraction of methanolic leaf extract of Camellia sinensis (green tea) on streptozotocin-induced diabetes linked testicular hypofunction in albino rat: A dose-dependent biochemical and genomic transection study. ACTA ACUST UNITED AC 2017; 14:/j/jcim.ahead-of-print/jcim-2016-0084/jcim-2016-0084.xml. [DOI: 10.1515/jcim-2016-0084] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 04/11/2017] [Indexed: 01/23/2023]
Abstract
AbstractBackgroundThe present investigation focuses the diabetes-induced testicular hypofunction and its possible correction by the effective dose of ethyl-acetate fraction of methanolic extract ofMethodsThe androgenic, spermiological, oxidative stress and apoptosis sensors along with testicular genomic sensors were evaluated in a dose-dependent fashion (50 mg or 100 mg or 200 mg/kg body weight). Activities of hepatic transaminases for toxicity assessment were also measured.ResultsIncreased level of fasting blood glucose, testicular cholesterol, seminal vesicular fructose along with a low count, motility and viability of epididymal sperm, low activities of testicular Δ5, 3β-hydroxy steroid dehydrogenase (HSD), 17β-HSD, testicular antioxidant enzymes (catalase and superoxide dismutase) and low plasma level of testosterone were noted in diabetic rat in respect to the control. After oral administration of said fraction to diabetic rat, levels of above sensors were resettled toward the control. A significant decrease in the number of different generations of germ cells at the stage VII of spermatogenesis in diabetic rat was noted which were recovered significantly toward the control in the fraction-treated diabetic group. It was supported by the correction in gene expression of testicular Δ5, 3β- HSD, 17β- HSD, Bcl-2 and Bax in the fraction-treated diabetic group.ConclusionsThe threshold dose of ethyl-acetate fraction of methanolic extract of
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Protective effects of tea, red wine and cocoa in diabetes. Evidences from human studies. Food Chem Toxicol 2017; 109:302-314. [PMID: 28893620 DOI: 10.1016/j.fct.2017.09.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 09/05/2017] [Accepted: 09/06/2017] [Indexed: 12/14/2022]
Abstract
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.
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Yin JY, Duan SY, Liu FC, Yao QK, Tu S, Xu Y, Pan CW. Blood Pressure Is Associated with Tea Consumption: A Cross-sectional Study in a Rural, Elderly Population of Jiangsu China. J Nutr Health Aging 2017; 21:1151-1159. [PMID: 29188874 DOI: 10.1007/s12603-016-0829-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVES Tea has long been hypothesized to possess hypotensive effects. However, there is uncertainty regarding the association of tea consumption with arterial blood pressure (BP). We aimed to examine the association between tea consumption and BP components including systolic BP (SBP) and diastolic BP (DBP). DESIGN Community-based, cross-sectional study of Suzhou City, Jiangsu Province, China. SETTING Tea consumption has protective influence on BP and presence of hypertension. PARTICIPANTS 4579 older adults aged 60 years or older from the Weitang Geriatric Diseases study. MEASUREMENTS Detailed information regarding tea consumption was collected using a pre-designed questionnaire. BP components were measured at least 3 times with a minimum 5-minute interval, by well-trained research nurses. METHODS Data of 4579 older adults (response rate: 82%) aged 60 years or older from the Weitang Geriatric Diseases study were included in the analysis and we estimated the relationship of tea consumption and BP using linear regression models and the association between tea consumption and risk of hypertension using logistic regression models. RESULTS In linear regression models, higher tea consumption frequency was found to be associated with lower systolic BP values, after adjusting for the effect of age, sex, education level, lifestyle-related factors, and cardiometabolic confounding factors in overall (coefficient =-1.49, P=0.0003), normotensive (coefficient =-0.91, P=0.017) and participants without anti-hypertensive treatment (coefficient =-1.26, P=0.027). Significant inverse association between diastolic BP and frequency of tea consumption was also observed in the overall subjects (coefficient =-0.74, P=0.003). In multivariate logistic analyses, habitual tea drinking was inversely associated with presence of hypertension [odds ratio (OR)=0.79, P=0.011] , and there was a progressive reduction in risk associated with higher frequency of tea consumption (P for trend=0.011). CONCLUSION Habitual tea consumption was found to be associated with lower values of components of BP and a reduced likelihood of having hypertension in older adults. Given the widespread consumption of tea throughout China and the world, together with the major cardiovascular disease risk, our findings have important implications for human health.
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Affiliation(s)
- J-Y Yin
- Chen-Wei Pan, MD, PhD, School of Public Health, Medical College of Soochow University, 199 Ren Ai Road, Suzhou, China 215123. Tel: +86 0512 65883907 /
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Lifestyle and health determinants of cardiovascular disease among Greek older adults living in Eastern Aegean Islands: An adventure within the MEDIS study. Hellenic J Cardiol 2016; 57:407-414. [DOI: 10.1016/j.hjc.2016.11.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 09/29/2016] [Indexed: 11/19/2022] Open
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Mohabbulla Mohib M, Fazla Rabby S, Paran TZ, Mehedee Hasan M, Ahmed I, Hasan N, Abu Taher Sagor M, Mohiuddin S. Protective role of green tea on diabetic nephropathy—A review. ACTA ACUST UNITED AC 2016. [DOI: 10.1080/23312025.2016.1248166] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Md. Mohabbulla Mohib
- Department of Pharmaceutical Sciences, North South University, Dhaka 1229, Bangladesh
| | - S.M. Fazla Rabby
- Department of Pharmaceutical Sciences, North South University, Dhaka 1229, Bangladesh
| | - Tasfiq Zaman Paran
- Department of Pharmaceutical Sciences, North South University, Dhaka 1229, Bangladesh
| | - Md. Mehedee Hasan
- Department of Pharmacy, State University of Bangladesh, Dhaka 1205, Bangladesh
| | - Iqbal Ahmed
- Department of Pharmaceutical Sciences, North South University, Dhaka 1229, Bangladesh
| | - Nahid Hasan
- Department of Pharmaceutical Sciences, North South University, Dhaka 1229, Bangladesh
| | - Md. Abu Taher Sagor
- Department of Pharmaceutical Sciences, North South University, Dhaka 1229, Bangladesh
| | - Sarif Mohiuddin
- Department of Anatomy, Pioneer Dental College and Hospital, Dhaka 1229, Bangladesh
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Dal S, Sigrist S. The Protective Effect of Antioxidants Consumption on Diabetes and Vascular Complications. Diseases 2016; 4:E24. [PMID: 28933404 PMCID: PMC5456287 DOI: 10.3390/diseases4030024] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 06/20/2016] [Accepted: 06/23/2016] [Indexed: 12/14/2022] Open
Abstract
Obesity and diabetes is generally accompanied by a chronic state of oxidative stress, disequilibrium in the redox balance, implicated in the development and progression of complications such as micro- and macro-angiopathies. Disorders in the inner layer of blood vessels, the endothelium, play an early and critical role in the development of these complications. Blunted endothelium-dependent relaxation and/or contractions are quietly associated to oxidative stress. Thus, preserving endothelial function and oxidative stress seems to be an optimization strategy in the prevention of vascular complications associated with diabetes. Diet is a major lifestyle factor that can greatly influence the incidence and the progression of type 2 diabetes and cardiovascular complications. The notion that foods not only provide basic nutrition but can also prevent diseases and ensure good health and longevity is now attained greater prominence. Some dietary and lifestyle modifications associated to antioxidative supply could be an effective prophylactic means to fight against oxidative stress in diabesity and complications. A significant benefit of phytochemicals (polyphenols in wine, grape, teas), vitamins (ascorbate, tocopherol), minerals (selenium, magnesium), and fruits and vegetables in foods is thought to be capable of scavenging free radicals, lowering the incidence of chronic diseases. In this review, we discuss the role of oxidative stress in diabetes and complications, highlight the endothelial dysfunction, and examine the impact of antioxidant foods, plants, fruits, and vegetables, currently used medication with antioxidant properties, in relation to the development and progression of diabetes and cardiovascular complications.
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Affiliation(s)
- Stéphanie Dal
- DIATHEC EA 7294 UMR Centre Européen d'Etude du Diabète (CeeD), Université de Strasbourg (UdS), boulevard René Leriche, Strasbourg 67200, France.
| | - Séverine Sigrist
- DIATHEC EA 7294 UMR Centre Européen d'Etude du Diabète (CeeD), Université de Strasbourg (UdS), boulevard René Leriche, Strasbourg 67200, France.
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Decaffeinated green tea extract rich in epigallocatechin-3-gallate improves insulin resistance and metabolic profiles in normolipidic diet—but not high-fat diet-fed mice. J Nutr Biochem 2015; 26:893-902. [DOI: 10.1016/j.jnutbio.2015.03.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 02/12/2015] [Accepted: 03/02/2015] [Indexed: 01/04/2023]
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Lochocka K, Bajerska J, Glapa A, Fidler-Witon E, Nowak JK, Szczapa T, Grebowiec P, Lisowska A, Walkowiak J. Green tea extract decreases starch digestion and absorption from a test meal in humans: a randomized, placebo-controlled crossover study. Sci Rep 2015. [PMID: 26226166 PMCID: PMC4520190 DOI: 10.1038/srep12015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Green tea is known worldwide for its beneficial effects on human health. However, objective data evaluating this influence in humans is scarce. The aim of the study was to assess the impact of green tea extract (GTE) on starch digestion and absorption. The study comprised of 28 healthy volunteers, aged 19 to 28 years. In all subjects, a starch 13C breath test was performed twice. Subjects randomly ingested naturally 13C-abundant cornflakes during the GTE test (GTE 4 g) or placebo test. The cumulative percentage dose recovery (CPDR) was significantly lower for the GTE test than for the placebo test (median [interquartile range]: 11.4% [5.5–15.5] vs. 16.1% [12.7–19.5]; p = 0.003). Likewise, CPDR expressed per hour was considerably lower in each point of the measurement. In conclusion, a single dose of green tea extract taken with a test meal decreases starch digestion and absorption.
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Affiliation(s)
- Klaudia Lochocka
- Department of Pediatric Gastroenterology and Metabolic Diseases, Poznan University of Medical Sciences, Poznan, Poland
| | - Joanna Bajerska
- Department of Human Nutrition and Hygiene, Poznan University of Life Sciences, Poznan, Poland
| | - Aleksandra Glapa
- Department of Pediatric Gastroenterology and Metabolic Diseases, Poznan University of Medical Sciences, Poznan, Poland
| | - Ewa Fidler-Witon
- Department of Pediatric Gastroenterology and Metabolic Diseases, Poznan University of Medical Sciences, Poznan, Poland
| | - Jan K Nowak
- Department of Pediatric Gastroenterology and Metabolic Diseases, Poznan University of Medical Sciences, Poznan, Poland
| | - Tomasz Szczapa
- Department of Neonatology, Poznan University of Medical Sciences, Poznan, Poland
| | - Philip Grebowiec
- Department of Pediatric Gastroenterology and Metabolic Diseases, Poznan University of Medical Sciences, Poznan, Poland
| | - Aleksandra Lisowska
- Department of Pediatric Gastroenterology and Metabolic Diseases, Poznan University of Medical Sciences, Poznan, Poland
| | - Jaroslaw Walkowiak
- Department of Pediatric Gastroenterology and Metabolic Diseases, Poznan University of Medical Sciences, Poznan, Poland
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Keske MA, Ng HLH, Premilovac D, Rattigan S, Kim JA, Munir K, Yang P, Quon MJ. Vascular and metabolic actions of the green tea polyphenol epigallocatechin gallate. Curr Med Chem 2015; 22:59-69. [PMID: 25312214 PMCID: PMC4909506 DOI: 10.2174/0929867321666141012174553] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 08/05/2014] [Accepted: 08/05/2014] [Indexed: 01/04/2023]
Abstract
Epidemiological studies demonstrate robust correlations between green tea consumption and reduced risk of type 2 diabetes and its cardiovascular complications. However, underlying molecular, cellular, and physiological mechanisms remain incompletely understood. Health promoting actions of green tea are often attributed to epigallocatechin gallate (EGCG), the most abundant polyphenol in green tea. Insulin resistance and endothelial dysfunction play key roles in the pathogenesis of type 2 diabetes and its cardiovascular complications. Metabolic insulin resistance results from impaired insulin-mediated glucose disposal in skeletal muscle and adipose tissue, and blunted insulin-mediated suppression of hepatic glucose output that is often associated with endothelial/vascular dysfunction. This endothelial dysfunction is itself caused, in part, by impaired insulin signaling in vascular endothelium resulting in reduced insulin-stimulated production of NO in arteries, and arterioles that regulate nutritive capillaries. In this review, we discuss the considerable body of literature supporting insulin-mimetic actions of EGCG that oppose endothelial dysfunction and ameliorate metabolic insulin resistance in skeletal muscle and liver. We conclude that EGCG is a promising therapeutic to combat cardiovascular complications associated with the metabolic diseases characterized by reciprocal relationships between insulin resistance and endothelial dysfunction that include obesity, metabolic syndrome and type 2 diabetes. There is a strong rationale for well-powered randomized placebo controlled intervention trials to be carried out in insulin resistant and diabetic populations.
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Affiliation(s)
| | | | | | | | | | | | | | - Michael J Quon
- Menzies Research Institute Tasmania, University of Tasmania, Hobart, Tasmania, 7000, Australia.
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Preventive role of green tea catechins from obesity and related disorders especially hypercholesterolemia and hyperglycemia. J Transl Med 2015; 13:79. [PMID: 25888764 PMCID: PMC4351924 DOI: 10.1186/s12967-015-0436-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 02/12/2015] [Indexed: 12/03/2022] Open
Abstract
Background During the last few years, scientific investigations have proposed diet based regimens to prevent several health ailments including obesity, hypercholesterolemia and diabetes. In this regard, a promising tool is the use of functional foods/nutraceuticals. Present research project was an attempt to explore nutraceutical worth of locally grown green tea variety (Qi-Men) against lifestyle related disorders. Methods Functional drinks (T2 and T3) were prepared by adding catechins and epigallocatechin gallate (EGCG) @ 550 mg/500 mL and compared with control (T1). These functional drinks were tested in experimental rats modeling (Sprague Dawley). Based on diets, four studies were conducted i.e. trial-I (normal diet), trial-II (high cholesterol diet), trial-III (high sucrose diet), trial-IV (high cholesterol + high sucrose diet). Rats were monitored daily for their feed and drink intake while body weight was measured on weekly basis. After period of 56 days rats were sacrificed and evaluated their serum lipid (cholesterol, LDL and HDL), glucose and insulin levels. Results Results for feed consumption by rats revealed that highest feed intake was recorded in group provided control drink than other groups. However, non significant differences were noted among all groups for drink consumption. Functional drinks resulted in significant reduction in body weight with maximum lowering noted in trial-II and III i.e. 10.73 to 8.49% and 10.12 to 10.49%, respectively. Likewise, cholesterol and LDL were substantially reduced with 14.42% decrease observed in trial-IV and 30.43% in trial-II, respectively. Furthermore, serum glucose and insulin levels were also lowered significantly in the trial-III and IV while in trial-I and II differences were non-significant. In contrast to lipid profile, experimental drink containing EGCG reduced the trait better than catechins based functional drink. Conclusions The drinks supplemented with catechins and EGCG are effective against obesity, hypercholesterolemia and hyperglycemia.
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Deng YT, Lin-Shiau SY, Shyur LF, Lin JK. Pu-erh tea polysaccharides decrease blood sugar by inhibition of α-glucosidase activity in vitro and in mice. Food Funct 2015; 6:1539-46. [DOI: 10.1039/c4fo01025f] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In this report we describe a group of carbohydrates found in pu-erh tea polysaccharide (PTPS) that can decrease blood sugar by inhibiting alpha-glucosidase.
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Affiliation(s)
- Yea-Tyz Deng
- Institute of Biochemistry and Molecular Biology
- College of Medicine
- National Taiwan University
- Taipei
- Taiwan
| | - Shoei-Yn Lin-Shiau
- Institute of Oral medicine
- College of Oral Medicine
- Chung Shan Medical University
- Taichung
- Taiwan
| | - Lie-Fen Shyur
- Agricultural Biotechnology Research Center
- Academia Sinica
- Taipei
- Taiwan
| | - Jen-Kun Lin
- Institute of Biochemistry and Molecular Biology
- College of Medicine
- National Taiwan University
- Taipei
- Taiwan
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A simple HPLC-UVD method for detection of etofenprox in green tea using sample hydration. Food Sci Biotechnol 2014. [DOI: 10.1007/s10068-014-0285-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Grosso G, Stepaniak U, Micek A, Topor-Mądry R, Pikhart H, Szafraniec K, Pająk A. Association of daily coffee and tea consumption and metabolic syndrome: results from the Polish arm of the HAPIEE study. Eur J Nutr 2014; 54:1129-37. [PMID: 25367317 PMCID: PMC4575379 DOI: 10.1007/s00394-014-0789-6] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 09/30/2014] [Indexed: 01/11/2023]
Abstract
Purpose The aim of this study was to evaluate whether daily consumption of coffee and tea was associated with components and prevalence of metabolic syndrome (MetS) in the Polish arm of the Health, Alcohol and Psychosocial factors In Eastern Europe cohort study. Methods A cross-sectional population-based survey including 8,821 adults (51.4 % female) was conducted in Krakow, Poland. Coffee and tea consumption was evaluated using food frequency questionnaires. MetS was defined according to the International Diabetes Federation definition. Linear and logistic regression models were performed to estimate odds ratios and confidence intervals. Results Among high coffee and tea consumers (3 or more cups/day), high prevalence of female gender, young age, medium–high educational and occupational level, high total energy intake, and smoking habit were found. High coffee drinkers had lower BMI, waist circumference, systolic and diastolic blood pressure, triglycerides, and higher HDL cholesterol than those drinking less than 1 cup/day. In contrast, high tea consumers had lower BMI, waist circumference, but not diastolic blood pressure, which was higher than low drinkers. After adjusting for potential confounding factors, both higher coffee and tea consumption were negatively associated with MetS (OR 0.75, 95 % CI 0.66, 0.86 and OR 0.79, 95 % CI 0.67, 0.92, respectively). Among specific components of MetS, high coffee consumption was negatively associated with waist circumference, hypertension, and triglycerides, whereas tea consumption with central obesity and fasting plasma glucose in women, but not in men. Conclusions Coffee and tea consumption was negatively associated with MetS and some of its components.
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Affiliation(s)
- Giuseppe Grosso
- Department of Clinical and Molecular Biomedicine, Section of Pharmacology and Biochemistry, University of Catania, V.le A. Doria 6, 95125, Catania, Italy. .,Department of Epidemiology and Population Studies, Jagiellonian University Medical College, Kraków, Poland.
| | - Urszula Stepaniak
- Department of Epidemiology and Population Studies, Jagiellonian University Medical College, Kraków, Poland
| | - Agnieszka Micek
- Department of Epidemiology and Population Studies, Jagiellonian University Medical College, Kraków, Poland
| | - Roman Topor-Mądry
- Department of Epidemiology and Population Studies, Jagiellonian University Medical College, Kraków, Poland
| | - Hynek Pikhart
- Department of Epidemiology and Public Health, University College London, London, UK
| | - Krystyna Szafraniec
- Department of Epidemiology and Population Studies, Jagiellonian University Medical College, Kraków, Poland
| | - Andrzej Pająk
- Department of Epidemiology and Population Studies, Jagiellonian University Medical College, Kraków, Poland
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Manrique C, Lastra G, Sowers JR. New insights into insulin action and resistance in the vasculature. Ann N Y Acad Sci 2014; 1311:138-50. [PMID: 24650277 DOI: 10.1111/nyas.12395] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Two-thirds of adults in the United States are overweight or obese, and another 26 million have type 2 diabetes. Decreased insulin sensitivity in cardiovascular tissue is an underlying abnormality in these individuals. Insulin metabolic signaling increases endothelial cell nitric oxide (NO) production. Impaired vascular insulin sensitivity is an early defect leading to impaired vascular relaxation. In overweight and obese persons, as well as in those with hypertension, systemic and vascular insulin resistance often occur in conjunction with activation of the cardiovascular tissue renin-angiotensin-aldosterone system (RAAS). Activated angiotensin II type 1 receptor and mineralocorticoid receptor signaling promote the development of vascular insulin resistance and impaired endothelial NO-mediated relaxation. Research in this area has implicated excessive serine phosphorylation and proteasomal degradation of the docking protein insulin receptor substrate and enhanced signaling through hybrid insulin/insulin-like growth factor receptor as important mechanisms underlying RAAS impediment of downstream vascular insulin metabolic signaling. This review will present recent evidence supporting the notion that RAAS signaling represents a potential pathway for the development of vascular insulin resistance and impaired endothelial-mediated vasodilation.
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Affiliation(s)
- Camila Manrique
- Division of Endocrinology, Department of Internal Medicine, University of Missouri, Columbia, Missouri; Harry S. Truman Veteran's Hospital, Columbia, Missouri
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Jang HJ, Ridgeway SD, Kim JA. Effects of the green tea polyphenol epigallocatechin-3-gallate on high-fat diet-induced insulin resistance and endothelial dysfunction. Am J Physiol Endocrinol Metab 2013; 305:E1444-51. [PMID: 24148349 PMCID: PMC3882381 DOI: 10.1152/ajpendo.00434.2013] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Insulin resistance, a hallmark of metabolic disorders, is a risk factor for diabetes and cardiovascular disease. Impairment of insulin responsiveness in vascular endothelium contributes to insulin resistance. The reciprocal relationship between insulin resistance and endothelial dysfunction augments the pathophysiology of metabolism and cardiovascular functions. The most abundant green tea polyphenol, epigallocatechin-3-gallate (EGCG), has been shown to have vasodilator action in vessels by activation of endothelial nitric oxide synthase (eNOS). However, it is not known whether EGCG has a beneficial effect in high-fat diet (HFD)-induced endothelial dysfunction. Male C57BL/6J mice were fed either a normal chow diet (NCD) or HFD with or without EGCG supplement (50 mg·kg(-1)·day(-1)) for 10 wk. Mice fed a HFD with EGCG supplement gained less body weight and showed improved insulin sensitivity. In vehicle-treated HFD mice, endothelial function was impaired in response to insulin but not to acetylcholine, whereas the EGCG-treated HFD group showed improved insulin-stimulated vasodilation. Interestingly, EGCG intake reduced macrophage infiltration into aortic tissues in HFD mice. Treatment with EGCG restored the insulin-stimulated phosphorylation of eNOS, insulin receptor substrate-1 (IRS-1), and protein kinase B (Akt), which was inhibited by palmitate (200 μM, 5 h) in primary bovine aortic endothelial cells. From these results, we conclude that supplementation of EGCG improves glucose tolerance, insulin sensitivity, and endothelial function. The results suggest that EGCG may have beneficial health effects in glucose metabolism and endothelial function through modulating HFD-induced inflammatory response.
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Affiliation(s)
- Hyun-Ju Jang
- Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Alabama at Birmingham, Birmingham, Alabama
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Wang X, Tian J, Jiang J, Li L, Ying X, Tian H, Nie M. Effects of green tea or green tea extract on insulin sensitivity and glycaemic control in populations at risk of type 2 diabetes mellitus: a systematic review and meta-analysis of randomised controlled trials. J Hum Nutr Diet 2013; 27:501-12. [PMID: 24206044 DOI: 10.1111/jhn.12181] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND Although the regular consumption of green tea or green tea extract has been considered to improve insulin sensitivity, the reported results are inconsistent. Therefore, we conducted a meta-analysis to evaluate the effect of green tea or green tea extract on insulin sensitivity and glycaemic control in populations at risk of type 2 diabetes mellitus (T2DM). METHODS Electronic databases, including PUBMED, The Cochrane Library, EMBASE, ISI Web of Knowledge, Chinese Biomedical Literature Database and Chinese Scientific Journals Fulltext Database, were systematically searched to identify randomised controlled trials (RCTs) up to December 2011, supplemented by the Clinicaltrials.gov websites and the reference lists of identified studies. Two reviewers independently selected trials, extracted data, and evaluated the methodological qualities and evidence levels. RESULTS Seven RCTs involving 510 participants were identified. There was no statistically significant difference between green tea or green tea extract group and placebo group with regard to fasting plasma glucose [standardised mean difference (SMD) 0.04; 95% confidence interval (CI) -0.15 to 0.24], fasting serum insulin (SMD -0.09; 95% CI -0.30 to 0.11), 2-h plasma glucose in the oral glucose tolerance test (OGTT-2 h) (SMD -0.14; 95% CI -0.63 to 0.34), haemoglobin A₁c (SMD 0.10; 95% CI -0.13 to 0.33) and homeostasis model of insulin resistance (HOMA(IR)) index (SMD -0.06; 95% CI -0.35 to 0.23) in participants at risk of T2DM. CONCLUSIONS The consumption of green tea did not decrease the levels of fasting plasma glucose, fasting serum insulin, OGTT-2 h glucose, haemoglobin A₁c and HOMA(IR) in populations at risk of T2DM. Larger, longer-term and high-quality RCTs are needed to further definitely determine the effect of green tea or green tea extract on insulin sensitivity and glycaemic control in populations at risk of T2DM.
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Affiliation(s)
- X Wang
- Key Laboratory of Endocrinology, Ministry of Health, Department of Endocrinology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
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Tang W, Li S, Liu Y, Huang MT, Ho CT. Anti-diabetic activity of chemically profiled green tea and black tea extracts in a type 2 diabetes mice model via different mechanisms. J Funct Foods 2013. [DOI: 10.1016/j.jff.2013.08.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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Gao J, Xu P, Wang Y, Wang Y, Hochstetter D. Combined effects of green tea extracts, green tea polyphenols or epigallocatechin gallate with acarbose on inhibition against α-amylase and α-glucosidase in vitro. Molecules 2013; 18:11614-23. [PMID: 24051476 PMCID: PMC6270344 DOI: 10.3390/molecules180911614] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 09/13/2013] [Accepted: 09/16/2013] [Indexed: 11/16/2022] Open
Abstract
Green tea, green tea polyphenols and epigallocatechin gallate (EGCG) are confirmed to have beneficial effects in the treatment of diabetes mellitus, and a possible mechanism can be ascribed to their inhibitory effect against α-amylase and α-glucosidase in the digestive tract. In this paper, we first investigated the combined inhibitory effect of green tea extracts, green tea polyphenols or EGCG with acarbose on α-amylase and α-glucosidase in vitro. Our results indicated that the interaction between green tea extracts (green tea polyphenols or EGCG) and acarbose was complicated. The combination of green tea extracts, green tea polyphenols or EGCG with acarbose had a synergistic effect on α-amylase and α-glucosidase at low concentrations and the combined effect turned out to be antagonistic at high concentrations according to the Combination Index (CI) values. These findings not only provided some significant quantitative values, but also provide some valuable implications for the combined use of acarbose and GTE (GTP or EGCG) in the treatment of diabetes mellitus.
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Affiliation(s)
- Junjie Gao
- Department of Tea Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, Zhejiang, China; E-Mails: (J.G.); (Y.W.); (D.H.)
| | - Ping Xu
- Department of Tea Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, Zhejiang, China; E-Mails: (J.G.); (Y.W.); (D.H.)
- Key Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Chinese Ministry of Agriculture, Hangzhou 310029, Zhejiang, China
- Author to whom correspondence should be addressed; E-Mail: ; Tel./Fax: +86-571-8898-2217
| | - Yuefei Wang
- Department of Tea Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, Zhejiang, China; E-Mails: (J.G.); (Y.W.); (D.H.)
- Key Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Chinese Ministry of Agriculture, Hangzhou 310029, Zhejiang, China
| | - Yiqi Wang
- College of Pharmacy, Zhejiang Chinese Medical University, Hangzhou 310053, Zhejiang, China; E-Mail:
| | - Danielle Hochstetter
- Department of Tea Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, Zhejiang, China; E-Mails: (J.G.); (Y.W.); (D.H.)
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Ruxton CHS, Mason P. Is black tea consumption associated with a lower risk of cardiovascular disease and type 2 diabetes? NUTR BULL 2011. [DOI: 10.1111/j.1467-3010.2011.01937.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Pullikotil P, Chen H, Muniyappa R, Greenberg CC, Yang S, Reiter CEN, Lee JW, Chung JH, Quon MJ. Epigallocatechin gallate induces expression of heme oxygenase-1 in endothelial cells via p38 MAPK and Nrf-2 that suppresses proinflammatory actions of TNF-α. J Nutr Biochem 2011; 23:1134-45. [PMID: 22137262 DOI: 10.1016/j.jnutbio.2011.06.007] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 06/09/2011] [Accepted: 06/16/2011] [Indexed: 12/11/2022]
Abstract
Epigallocatechin gallate (EGCG), the major polyphenol in green tea, acutely stimulates production of nitric oxide (NO) from vascular endothelium to reduce hypertension and improve endothelial dysfunction in spontaneously hypertensive rats. Herein, we explored additional mechanisms whereby EGCG may mediate beneficial cardiovascular actions. When compared with vehicle-treated controls, EGCG treatment (2.5 μM, 8 h) of human aortic endothelial cells (HAEC) caused a ~three-fold increase in heme oxygenase-1 (HO-1) mRNA and protein with comparable increases in HO-1 activity. This was unaffected by pretreatment of cells with wortmannin, LY294002, PD98059 or L-NAME (PI 3-kinase, MEK and NO synthase inhibitors, respectively). Pretreatment of HAEC with SB203580 (p38 MAPK inhibitor) or siRNA knockdown of p38 MAPK completely blocked EGCG-stimulated induction of HO-1. EGCG treatment also inhibited tumor-necrosis-factor-α-stimulated expression of vascular cell adhesion molecule (VCAM)-1 and decreased adhesion of monocytes to HAEC. siRNA knockdown of HO-1, p38 MAPK or Nrf-2 blocked these inhibitory actions of EGCG. In HAEC transiently transfected with a human HO-1 promoter luciferase reporter (or an isolated Nrf-2 responsive region), luciferase activity increased in response to EGCG. This was inhibitable by SB203580 pretreatment. EGCG-stimulated expression of HO-1 and Nrf-2 was blocked by siRNA knockdown of Nrf-2 or p38 MAPK. Finally, liver from mice chronically treated with EGCG had increased HO-1 and decreased VCAM-1 expression. Thus, in vascular endothelium, EGCG requires p38 MAPK to increase expression of Nrf-2 that drives expression of HO-1, resulting in increased HO-1 activity. Increased HO-1 expression may underlie anti-inflammatory actions of EGCG in vascular endothelium that may help mediate beneficial cardiovascular actions of green tea.
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Affiliation(s)
- Philomena Pullikotil
- Diabetes Unit, National Center for Complementary and Alternative Medicine, Bethesda, MD 20892, USA
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Hodgson JM, Croft KD. Tea flavonoids and cardiovascular health. Mol Aspects Med 2010; 31:495-502. [PMID: 20837049 DOI: 10.1016/j.mam.2010.09.004] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 09/02/2010] [Accepted: 09/02/2010] [Indexed: 12/21/2022]
Abstract
The two main types of tea are green and black. Both green and black teas are rich dietary sources of flavonoids. Available evidence suggests that regular tea consumption may reduce the risk of cardiovascular disease. The cardiovascular health benefits of drinking tea are thought to be largely due to flavonoids. Tea intake and intake of flavonoids found in tea have been associated with reduced risk of cardiovascular disease in cross-sectional and prospective population studies. Isolated flavonoids found in tea have also been consistently shown to inhibit the development of atherosclerosis in animal models. A number of possible pathways and mechanisms have been investigated. There is now consistent data indicating that tea and tea flavonoids can enhance nitric oxide status and improve endothelial function, which may be at least partly responsible for benefits on cardiovascular health. There is also evidence, although limited, to suggest benefits of green tea (flavonoids) on body weight and body fatness. Data supporting reduced oxidative damage, inflammation, platelet activation, blood pressure, and risk of type 2 diabetes with tea (flavonoids) remains inadequate to draw any conclusions.
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Affiliation(s)
- Jonathan M Hodgson
- School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia, Australia.
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Role of (-)-epigallocatechin-3-gallate in cell viability, lipogenesis, and retinol-binding protein 4 expression in adipocytes. Naunyn Schmiedebergs Arch Pharmacol 2010; 382:303-10. [PMID: 20711765 DOI: 10.1007/s00210-010-0547-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 07/31/2010] [Indexed: 10/19/2022]
Abstract
(-)-Epigallocatechin-3-gallate (EGCG), a bioactive compound of green tea, is known to combat obesity by reducing the viability and lipid accumulation of adipocytes. In this study, we evaluated the mechanism and clinical relevance on those actions of EGCG. We measured the viability of 3T3-L1 preadipocytes and adipocytes by the 3-(4, 5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide assay. Lipid accumulation was measured by Oil Red O staining. Intracellular accumulation of reactive oxygen species (ROS) was determined using a flow cytometer. Cellular glucose uptake was determined with 2-deoxy-[(3)H]-glucose. The protein levels of peroxisome proliferator-activated receptor (PPAR)-γ and adiponectin in 3T3-L1 adipocytes, as well as the protein level and secretion of plasma retinol-binding protein (RBP4) in human adipocytes, were measured by western blot. EGCG at concentrations higher than 10 μM induced ROS generation and decreased the viability and lipid accumulation of adipocytes. It also decreased the expression of PPAR-γ and adiponectin. At concentrations readily achievable in human plasma via green tea intake (≤10 μM), EGCG inhibited cellular glucose uptake and enhanced the expression and secretion of RBP4 in adipocytes. Pharmacological doses of EGCG showed cytotoxic effects in preadipocytes and adipocytes. EGCG-mediated glucose uptake inhibition in adipocytes may be clinically relevant and is probably linked to the increase in the expression and secretion of RBP4. Because secreted RBP4 from adipocytes inhibits muscular glucose uptake and enhance hepatic glucose output, the systemic effect of EGCG associated with its effect on RBP4 secretion should be further determined, as it may negatively regulate whole-body insulin sensitivity, contrary to general belief.
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Impact of dietary polyphenols on carbohydrate metabolism. Int J Mol Sci 2010; 11:1365-402. [PMID: 20480025 PMCID: PMC2871121 DOI: 10.3390/ijms11041365] [Citation(s) in RCA: 670] [Impact Index Per Article: 47.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 03/24/2010] [Accepted: 03/25/2010] [Indexed: 12/12/2022] Open
Abstract
Polyphenols, including flavonoids, phenolic acids, proanthocyanidins and resveratrol, are a large and heterogeneous group of phytochemicals in plant-based foods, such as tea, coffee, wine, cocoa, cereal grains, soy, fruits and berries. Growing evidence indicates that various dietary polyphenols may influence carbohydrate metabolism at many levels. In animal models and a limited number of human studies carried out so far, polyphenols and foods or beverages rich in polyphenols have attenuated postprandial glycemic responses and fasting hyperglycemia, and improved acute insulin secretion and insulin sensitivity. The possible mechanisms include inhibition of carbohydrate digestion and glucose absorption in the intestine, stimulation of insulin secretion from the pancreatic β–cells, modulation of glucose release from the liver, activation of insulin receptors and glucose uptake in the insulin-sensitive tissues, and modulation of intracellular signalling pathways and gene expression. The positive effects of polyphenols on glucose homeostasis observed in a large number of in vitro and animal models are supported by epidemiological evidence on polyphenol-rich diets. To confirm the implications of polyphenol consumption for prevention of insulin resistance, metabolic syndrome and eventually type 2 diabetes, human trials with well-defined diets, controlled study designs and clinically relevant end-points together with holistic approaches e.g., systems biology profiling technologies are needed.
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Fenercioglu AK, Saler T, Genc E, Sabuncu H, Altuntas Y. The effects of polyphenol-containing antioxidants on oxidative stress and lipid peroxidation in Type 2 diabetes mellitus without complications. J Endocrinol Invest 2010; 33:118-24. [PMID: 19834314 DOI: 10.1007/bf03346565] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND The hyperglycemia-induced oxidative stress in diabetes mellitus (DM) is the major factor in the pathogenesis of cardiovascular complications. The phenolic compounds are potent antioxidants that can reverse the factors leading to cardiovascular complications in DM. The aim of this study was to determine the antagonizing effects of a polyphenol-rich antioxidant supplement containing pomegranate extract, green tea extract, and ascorbic acid, on oxidative stress in Type 2 diabetic patients. MATERIALS AND METHODS A total of 114 male and female non-smokers (56 study, 58 placebo) with Type 2 DM and without any complications were recruited. The blood levels of fasting blood glucose, glycated hemoglobin, LDL, HDL, triglycerides, plasma malondialdehyde (MDA), total glutathione (GSH), hydrogen peroxide, and antioxidant capacity (AOC) were determined at the beginning and at the end of the 3-month trial. The differences of the data changes between the groups were statistically analyzed by Mann-Whitney U test. RESULTS The study group showed a decrease in LDL and an increase in HDL and the comparison with the difference in placebo group was statistically significant (p<0.001 for LDL and p<0.001 for HDL). Accordingly, as a by-product of lipid peroxidation, plasma MDA was decreased in the study group compared to the placebo group (p<0.001). As an indicator of increased antioxidant defense, total plasma GSH and AOC increased more in the study group compared to control group (p<0.001). CONCLUSIONS These observations indicated that the polyphenol-rich antioxidant supplement containing pomegranate extract, green tea extract, and ascorbic acid has important antagonizing effects on oxidative stress and lipid peroxidation in patients with Type 2 DM and might be beneficial in preventing cardiovascular complications.
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Affiliation(s)
- A Kutan Fenercioglu
- Department of Family Medicine, Yeditepe University Medical Faculty, Istanbul, Turkey.
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van Dieren S, Uiterwaal CSPM, van der Schouw YT, van der A DL, Boer JMA, Spijkerman A, Grobbee DE, Beulens JWJ. Coffee and tea consumption and risk of type 2 diabetes. Diabetologia 2009; 52:2561-9. [PMID: 19727658 DOI: 10.1007/s00125-009-1516-3] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Accepted: 08/07/2009] [Indexed: 02/06/2023]
Abstract
AIMS/HYPOTHESIS The aim of this study was to examine the association of consumption of coffee and tea, separately and in total, with risk of type 2 diabetes and which factors mediate these relations. METHODS This research was conducted as part of the Dutch Contribution to the European Prospective Investigation into Cancer and Nutrition, which involves a prospective cohort of 40,011 participants with a mean follow-up of 10 years. A validated food-frequency questionnaire was used to assess coffee and tea consumption and other lifestyle and dietary factors. The main outcome was verified incidence of type 2 diabetes. Blood pressure, caffeine, magnesium and potassium were examined as possible mediating factors. RESULTS During follow-up, 918 incident cases of type 2 diabetes were documented. After adjustment for potential confounders, coffee and tea consumption were both inversely associated with type 2 diabetes, with hazard ratios of 0.77 (95% CI 0.63-0.95) for 4.1-6.0 cups of coffee per day (p for trend = 0.033) and 0.63 (95% CI: 0.47-0.86) for >5.0 cups of tea per day (p for trend = 0.002). Total daily consumption of at least three cups of coffee and/or tea reduced the risk of type 2 diabetes by approximately 42%. Adjusting for blood pressure, magnesium, potassium and caffeine did not attenuate the associations. CONCLUSIONS/INTERPRETATION Drinking coffee or tea is associated with a lowered risk of type 2 diabetes, which cannot be explained by magnesium, potassium, caffeine or blood pressure effects. Total consumption of at least three cups of coffee or tea per day may lower the risk of type 2 diabetes.
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Affiliation(s)
- S van Dieren
- Julius Centre for Health Sciences and Primary Care, University Medical Centre Utrecht, P.O. Box 85500, 3508 GA, Utrecht, the Netherlands
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Sá CM, Ramos AA, Azevedo MF, Lima CF, Fernandes-Ferreira M, Pereira-Wilson C. Sage tea drinking improves lipid profile and antioxidant defences in humans. Int J Mol Sci 2009; 10:3937-3950. [PMID: 19865527 PMCID: PMC2769154 DOI: 10.3390/ijms10093937] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Revised: 08/25/2009] [Accepted: 09/08/2009] [Indexed: 01/24/2023] Open
Abstract
Salvia officinalis (common sage) is a plant with antidiabetic properties. A pilot trial (non-randomized crossover trial) with six healthy female volunteers (aged 40–50) was designed to evaluate the beneficial properties of sage tea consumption on blood glucose regulation, lipid profile and transaminase activity in humans. Effects of sage consumption on erythrocytes’ SOD and CAT activities and on Hsp70 expression in lymphocytes were also evaluated. Four weeks sage tea treatment had no effects on plasma glucose. An improvement in lipid profile was observed with lower plasma LDL cholesterol and total cholesterol levels as well as higher plasma HDL cholesterol levels during and two weeks after treatment. Sage tea also increased lymphocyte Hsp70 expression and erythrocyte SOD and CAT activities. No hepatotoxic effects or other adverse effects were observed.
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Affiliation(s)
- Carla M. Sá
- CBMA–Centre of Molecular and Environmental Biology/Department of Biology, School of Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; E-Mails: (C.M.S.); (A.A.R.); (M.F.A.)
| | - Alice A. Ramos
- CBMA–Centre of Molecular and Environmental Biology/Department of Biology, School of Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; E-Mails: (C.M.S.); (A.A.R.); (M.F.A.)
| | - Marisa F. Azevedo
- CBMA–Centre of Molecular and Environmental Biology/Department of Biology, School of Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; E-Mails: (C.M.S.); (A.A.R.); (M.F.A.)
| | - Cristovao F. Lima
- CITAB–Centre for the Research and Technology of Agro-Environment and Biological Sciences/Department of Biology, School of Sciences, University of Minho, 4710-057 Braga, Portugal; E-Mails: (C.F.L.); (M.F.F.)
| | - Manuel Fernandes-Ferreira
- CITAB–Centre for the Research and Technology of Agro-Environment and Biological Sciences/Department of Biology, School of Sciences, University of Minho, 4710-057 Braga, Portugal; E-Mails: (C.F.L.); (M.F.F.)
| | - Cristina Pereira-Wilson
- CBMA–Centre of Molecular and Environmental Biology/Department of Biology, School of Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; E-Mails: (C.M.S.); (A.A.R.); (M.F.A.)
- Author to whom correspondence should be addressed; E-Mail:; Tel. +351-253604318; Fax: +351-253678980
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Kourlaba G, Panagiotakos D. The number of index components affects the diagnostic accuracy of a diet quality index: the role of intracorrelation and intercorrelation structure of the components. Ann Epidemiol 2009; 19:692-700. [PMID: 19560370 DOI: 10.1016/j.annepidem.2009.03.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Revised: 03/07/2009] [Accepted: 03/16/2009] [Indexed: 11/16/2022]
Abstract
PURPOSE The aim of this work was to evaluate whether the number of components influences the diagnostic accuracy of a diet quality index and whether this association is affected by the intercorrelation structure of components and by the association of components with an outcome (intracorrelation). METHODS Simulated data were used to develop theoretical indices with various intracorrelation and intercorrelation structures of the components and outcomes. Moreover, dietary intake data of 668 elderly people from the MEDIS (Mediterranean Islands) study were also used to develop a diet index and to test it toward obesity status (outcome). RESULTS On the basis of 1,000 simulations, we observed that the diagnostic accuracy of an index increases as the number of components increases, only when the components are not intercorrelated or have low intercorrelation. Moreover, the diagnostic accuracy of an index developed with all components associated with an outcome is higher compared with an index developed by using only some components related to the outcome. Finally, the predictive ability of an isolated component is lower than that of an index developed by using non-intercorrelated or low-intercorrelated components. Real data confirmed the aforementioned findings. CONCLUSION Low-intercorrelated or non-intercorrelated components, strongly associated with a particular outcome, should be used in order to obtain an accurate composite index.
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Affiliation(s)
- Georgia Kourlaba
- Office of Biostatistics-Epidemiology, Department of Nutrition Science-Dietetics, Harokopio University, Athens, Greece
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Development of a Diet Index for Older Adults and Its Relation to Cardiovascular Disease Risk Factors: The Elderly Dietary Index. ACTA ACUST UNITED AC 2009; 109:1022-30. [DOI: 10.1016/j.jada.2009.03.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2008] [Accepted: 12/04/2008] [Indexed: 12/25/2022]
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Jing Y, Han G, Hu Y, Bi Y, Li L, Zhu D. Tea consumption and risk of type 2 diabetes: a meta-analysis of cohort studies. J Gen Intern Med 2009; 24:557-62. [PMID: 19308337 PMCID: PMC2669862 DOI: 10.1007/s11606-009-0929-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2008] [Revised: 12/16/2008] [Accepted: 01/26/2009] [Indexed: 12/25/2022]
Abstract
BACKGROUND Tea consumption has been extensively studied in relation to various diseases, several epidemiologic studies have been performed to investigate the association of tea consumption with type 2 diabetes; however, the results of these studies were not entirely consistent. OBJECTIVE To conduct a meta-analysis of studies that assessed the association of tea consumption and the risk of type 2 diabetes. RESEARCH DESIGN AND METHODS We performed a systematic literature search through November 2008 in PUBMED, MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews. The search was limited to English-language studies. Studies were excluded if they were type 1 diabetes, animal studies. Nine cohort studies were identified by two authors, and summary relative risks (RRs) were calculated using a random-effects model. RESULTS We identified nine cohort studies, including 324,141 participants and 11,400 incident cases of type 2 diabetes with follow-up ranging from 5 to 18 years. The summary adjusted RR did not show that tea consumption was associated with a reduced type 2 diabetes risk (RR, 0.96; 95% confidence interval (CI), 0.92-1.01). Evidence from the results of our stratified analyses revealed that tea consumption > or =4 cups per day (RR, 0.8; 95% CI, 0.7-0.93) might play a role in the prevention of type 2 diabetes. However, no statistically significant association was observed for sex and the follow-up durations stratified between tea consumption and type 2 diabetes. CONCLUSIONS This meta-analysis indicates that tea consumption > or =4 cups per day may lower the risk of type 2 diabetes.
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Affiliation(s)
- Yali Jing
- Department of Endocrinology, Drum Tower Clinical Medical College of Nanjing Medical University, Nanjing, Jiangsu Province China
| | - Guanjun Han
- Department of Endocrinology, Drum Tower Clinical Medical College of Nanjing Medical University, Nanjing, Jiangsu Province China
| | - Yun Hu
- Department of Endocrinology, Affiliated Drum Tower Hospital, Medical College of Nanjing University, Nanjing, Jiangsu Province China
| | - Yan Bi
- Department of Endocrinology, Affiliated Drum Tower Hospital, Medical College of Nanjing University, Nanjing, Jiangsu Province China
| | - Lirong Li
- Department of Endocrinology, Affiliated Drum Tower Hospital, Medical College of Nanjing University, Nanjing, Jiangsu Province China
| | - Dalong Zhu
- Department of Endocrinology, Drum Tower Clinical Medical College of Nanjing Medical University, Nanjing, Jiangsu Province China
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Ulrich-Merzenich G, Zeitler H, Vetter H, Kraft K. Synergy research: vitamins and secondary plant components in the maintenance of the redox-homeostasis and in cell signaling. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2009; 16:2-16. [PMID: 19118991 DOI: 10.1016/j.phymed.2008.11.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2008] [Accepted: 11/20/2008] [Indexed: 05/27/2023]
Abstract
The maintenance of the redox-homeostasis is an essential task of antioxidants. Reactive oxygen species (ROS) formed during oxidative stress can potentially damage the normal cellular functions and support pathological processes like atherosclerosis in vessels or malignant growth in other tissues, but also the aging process. However, recent findings link ROS also to cell survival and/or proliferation, which revolutionises the age-old dogmatic view of ROS being exclusively involved in cell damage and death. Low concentrations of hydrogenperoxide e.g. are involved in cell signaling and can activate mitogen-activated kinases (MAPK) to initiate cell growth. Nutritional antioxidants like vitamin C or E can promote endothelial cell growth, but can also inhibit growth of muscle cells, and influence MAPK. Thus, keeping the redox-homeostasis in a steady state especially in the context of tissue regeneration appears to be more important than previously known and seems to be a controlled synergistic action of antioxidants and ROS. The present review summarizes the properties and functions of ROS and nutritional antioxidants like the vitamins C and E, and polyphenols in redox-homeostasis. Their relevance in the treatment of various diseases is discussed in the context of a multitarget therapy with nutraceuticals and phytotherapeutic drugs.
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Abstract
PURPOSE OF REVIEW To update the growing literature suggesting that tea and its constituent flavonoids are inversely related to the risk of chronic diseases common among the elderly. RECENT FINDINGS Results are provided from recent observational studies and clinical trials on the relationship of tea and tea catechins to body weight control and energy metabolism, impaired glucose tolerance and diabetes, cardiovascular disease, bone mineral density, cognitive function and neurodegenerative disease, and cancer. The evidence for the efficacy and potency of tea and tea extracts in benefiting these outcomes ranges from compelling for cardiovascular disease to equivocal at best for some forms of cancer. SUMMARY Although randomized clinical trials of tea have generally been of short duration and with small sample sizes, together with experimental and epidemiological studies, the totality of the data suggests a role for tea in health promotion as a beverage absent in calories and rich in phytochemicals. Further research is warranted on the putative benefits of tea and the potential for synergy among its constituent flavonoids, L-theanine, and caffeine.
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Affiliation(s)
- Bradley W Bolling
- Antioxidants Research Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts 02111, USA
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Maruyama K, Iso H, Sasaki S, Fukino Y. The Association between Concentrations of Green Tea and Blood Glucose Levels. J Clin Biochem Nutr 2008; 44:41-5. [PMID: 19177186 PMCID: PMC2613497 DOI: 10.3164/jcbn.08-13] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Accepted: 03/11/2008] [Indexed: 02/03/2023] Open
Abstract
Our objective was to examine whether habitual green tea consumption is associated with blood glucose levels and other biomarkers of glucose metabolism. We conducted a cross-sectional study of 35 male volunteers, 23–63 years old and residing in Shizuoka Prefecture in Japan. Biochemical data were measured and we conducted a questionnaire survey on health, lifestyle, and nutrition, as well as frequency of consumption and concentrations (1%, 2%, and 3%) of green tea. Men who consumed a 3% concentration of green tea showed lower mean values of fasting blood glucose and fructosamine than those who consumed a 1% concentration. Fasting blood glucose levels were found to be significantly associated with green tea concentration (β = −0.14, p = 0.03). However, green tea consumption frequency showed no significant differences in mean levels of blood glucose, fructosamine and hemoglobin A1c. In conclusion, our findings suggest that the consumption of green tea at a high concentration has the potential to reduce blood glucose levels.
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Affiliation(s)
- Koutatsu Maruyama
- Department of Food and Nutritional Sciences, Graduate School of Nutritional and Environmental Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka-shi 422-8526, Japan
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Green tea: beneficial effects on cholesterol and lipid metabolism besides endothelial function. ACTA ACUST UNITED AC 2008; 15:497. [PMID: 18677179 DOI: 10.1097/hjr.0b013e32830e1e75] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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