Cardiovascular Benefits of EGCG

February 24, 2009 by  
Filed under All, Science, Tea

Recent research published in the American Journal of Physiology Endocrinology And Metabolism describes wide-ranging cardiovascular protective functions of a green tea polyphenol, EGCG. EGCG improved endothelial function and insulin sensitivity, reduced blood pressure and protected against myocardial ischemia and reperfusion injury. The addition of improvements in insulin sensitivity to the cardiovascular benefits indicates the benefit of green tea polyphenols against metabolic syndrome with hypertension, insulin resistance and overweight.

Am J Physiol Endocrinol Metab, 2007 Jan 16; [Epub ahead of print]Potenza MA, Marasciulo FL, Tarquinio M, et al.

Epigallocatechin gallate (EGCG), a bioactive polyphenol in green tea, may augment metabolic and vascular actions of insulin. We investigated effects of EGCG treatment to simultaneously improve cardiovascular and metabolic function in SHR rats (model of metabolic syndrome with hypertension, insulin resistance, and overweight). In acute studies, EGCG (1-100 microM) elicited dose-dependent vasodilation in mesenteric vascular beds (MVB) from SHR ex vivo, inhibitable by L-NAME (NOS antagonist) or wortmannin (PI 3-kinase inhibitor). In chronic studies, 9-wk old SHR were treated by gavage for 3 weeks with EGCG (200 mg/kg/d), enalapril (30 mg/kg/d), or vehicle. A separate group of SHR receiving L-NAME (80 mg/L in drinking water) was treated for 3 weeks with either EGCG or vehicle. Vasodilator actions of insulin were significantly improved in MVB from EGCG- or enalapril-treated SHR (compared with vehicle-SHR). Both EGCG and enalapril therapy significantly lowered systolic blood pressure (SBP) in SHR. EGCG therapy of SHR significantly reduced infarct size and improved cardiac function in Langendorff-perfused hearts exposed to ischemia/reperfusion injury (I/R). In SHR given L-NAME, effects of EGCG on SBP and I/R were not observed. Both enalapril and EGCG treatment of SHR improved insulin sensitivity and raised plasma adiponectin. We conclude that acute actions of EGCG to stimulate production of NO from endothelium using PI 3-kinase dependent pathways may explain, in part, beneficial effects of EGCG therapy to simultaneously improve metabolic and cardiovascular pathophysiology in SHR. These findings may be relevant to understanding potential benefits of green tea consumption in patients with metabolic syndrome.

Green Tea for HIV Treatment?

February 24, 2009 by  
Filed under All, Science, Tea

The green tea flavonoid EGCG has potential therapeutic value for
treatment to for HIV-1 infection EGCG binds to the CD4 molecule on
T-cells according to research conducted in 2006. “We have
demonstrated clear evidence of high affinity binding of EGCG to the CD4
molecule. EGCG has potential use as an adjunctive treatment in HIV-1
infection.”

J Allergy Cli, Immunol Williamson ME McCormick TG, Nance CL, Shearer WT. 2006;118:1369-1374.
Epigallocatechin gallate, the main polyphenol in green tea, binds to
the T-cell receptor, CD4: potential for HIV-1 therapy.(Recent
Abstracts)(Brief article)
BACKGROUND: The green tea flavonoid, epigallocatechin gallate (EGCG),
has been proposed to have an anti-HIV-1 effect by preventing the
binding of HIV-1 glycoprotein (gp) 120 to the CD4 molecule on T cells.
OBJECTIVE: To demonstrate that EGCG binds to the CD4 molecule at the
gpl20 attachment site and inhibits gp120 binding at physiologically
relevant levels, thus establishing EGCG as a potential therapeutic
treatment for HIV-1 infection. METHODS: Nuclear magnetic resonance
spectroscopy was used to examine the binding of EGCG and control,
(-)-catechin, to CD4-IgG2 (PRO 542). Gp120 binding to human CD4+ T
cells was analyzed by flow cytometry. RESULTS: Addition of CD4 to EGCG
produced a linear decrease in nuclear magnetic resonance signal
intensity from EGCG but not from the control, (-)-catechin. In
saturation transfer difference experiments, addition of 5.8 micromol/L
CD4 to 310 micromol/L EGCG produced strong saturation at the aromatic
rings of EGCG, but identical concentrations of (-)-catechin produced
much smaller effects, implying EGCG/CD4 binding strong enough to reduce
gp120/ CD4 binding substantially. Molecular modeling studies suggested
a binding site for EGCG in the D1 domain of CD4, the pocket that binds
gpl20. Physiologically relevant concentrations of EGCG (0.2 micromol/L)
inhibited binding of gp120 to isolated human CD4+ T cells. CONCLUSION:
We have demonstrated clear evidence of high-affinity binding of EGCG to
the CD4 molecule with a Kd of approximately 10 nmol/L and inhibition
ofgpl20 binding to human CD4+ T cells. CLINICAL IMPLICATIONS:
Epigallocatechin gallate has potential use as adjunctive therapy in
HIV-1 infection.

USP Investigates Safety Of Green Tea Extracts

February 24, 2009 by  
Filed under All, Science, Tea

Green tea is the fourth most commonly used dietary supplement in the
United States. After the publication of adverse event case reports
involving green tea products and potential liver toxicity, the US
Pharmacopeia reviewed safety information for green tea products. 216
case reports on green tea products were analyzed including 34 reports
concerning liver damage. 27 reports pertaining to liver damage were
categorized as possible causality and seven as probable causality.
Pharmacokinetic and animal toxicological studies indicate that
consumption of green tea concentrated extracts on an empty stomach is
more likely to lead to adverse effects than consumption in the fed
state. USP concluded “when dietary supplement products containing
green tea extracts are used in formulated appropriately the Committee
is unaware of significant safety issues that would prohibit monograph
development, provided that caution statement is included in the
labeling section.”

Safety of Green Tea Extracts : A Systematic Review by the US Pharmacopeia.
Drug Saf. 2008;31(6):469-84.. Sarma DN, Barrett ML, Chavez ML, Gardiner
P, Ko R, Mahady GB, Marles RJ, Pellicore LS, Giancaspro GI, Low Dog T.

Green tea [Camellia sinensis (L.) Kuntze] is the fourth most
commonly used dietary supplement in the US. Recently, regulatory
agencies in France and Spain suspended market authorization of a
weight-loss product containing green tea extract because of
hepatotoxicity concerns. This was followed by publication of adverse
event case reports involving green tea products. In response, the US
Pharmacopeia (USP) Dietary Supplement Information Expert Committee (DSI
EC) systematically reviewed the safety information for green tea
products in order to re-evaluate the current safety class to which
these products are assigned. DSI EC searched PubMed (January 1966-June
2007) and EMBASE (January 1988-June 2007) for clinical case reports and
animal pharmacological or toxicological information. Reports were also
obtained from a diverse range of other sources, including published
reviews, the US FDA MedWatch programme, USP’s MEDMARX((R))
adverse event reporting system, the Australian Therapeutic Goods
Administration, the UK Medicines and Healthcare products Regulatory
Agency, and Health Canada’s Canadian Adverse Drug Reaction
Monitoring Program. Case reports pertaining to liver damage were
evaluated according to the Naranjo causality algorithm scale. In
addition, the Committee analysed information concerning historical use,
regulatory status, and current extent of use of green tea products. A
total of 216 case reports on green tea products were analysed,
including 34 reports concerning liver damage. Twenty-seven reports
pertaining to liver damage were categorized as possible causality and
seven as probable causality. Clinical pharmacokinetic and animal
toxicological information indicated that consumption of green tea
concentrated extracts on an empty stomach is more likely to lead to
adverse effects than consumption in the fed state. Based on this safety
review, the DSI EC determined that when dietary supplement products
containing green tea extracts are used and formulated appropriately the
Committee is unaware of significant safety issues that would prohibit
monograph development, provided a caution statement is included in the
labelling section. Following this decision, USP’s DSI ECs may
develop monographs for green tea extracts, and USP may offer its
verification programmes related to that dietary ingredient.

Green Tea Consumption And Liver Disease

February 24, 2009 by  
Filed under All, Science, Tea

Just to keep things in perspective, the previous item about green
tea extracts potentially causing liver problems must be balanced
against research showing that green tea is protective against liver
disease. Chinese researchers a value weighted interventional and
observational studies in both Western countries and in China published
between 1989 and 2007. They found “a significant protective role
of green tea against various liver diseases” and “a
positive correlation between green tea intake and attenuation of liver
disease.” Their conclusion? “An increased consumption of
green tea may reduce the risk of liver disease.”

Green tea consumption and liver disease: a systematic review. Liver Int. 2008 May 14. [Epub ahead of print]
Jin X, Zheng RH, Li YM.

Objectives: To present the effect of green tea consumption against
liver disease. Data sources: Interventional and observational studies
both in Western countries and in China and published between the years
1989 and December 2007. Review Methods: The articles were retrieved
from Medline, Embase database, Chinese biomedicine web database and
Chinese scientific journal’s database using proper MESH headings
and assessed by two independent investigators according to established
inclusion criteria. The characteristics and outcomes of the chosen
articles were displayed for further analysis and the quality of each
study was also evaluated according to the widely acknowledged criteria.
P<0.05 was defined as statistically significant in all enrolled
trials. Results: Ten qualified studies (eight from China, one from
Japan and the other from the USA) with various outcomes such as liver
cancer, cirrhosis and fatty liver disease were finally chosen. Among
them, study designs differed in that there were four
randomized-controlled clinical trials, two cohort, one case-control and
three cross-sectional studies. The heterogeneity in the study design,
outcomes, cofounders and amount of tea consumption precluded further
meta-analysis. Nevertheless, eight studies showed a significant
protective role of green tea against various liver diseases as
determined by relative risk/odds ratio or P-value and among them, four
studies showed a positive correlation between green tea intake and
attenuation of liver disease. Moreover, the other two studies also
presented the protective tendency of green tea against liver disease.
Conclusions: An increased consumption of green tea may reduce the risk
of liver disease.

Tea And Sweat: A New Antiaging Strategy

February 24, 2009 by  
Filed under All, Science, Tea

Japanese researchers explored the effect of tea catechins and
regular exercise and the aging associated declining physical
performance in mice. The endurance capacity of mice as measured by
running time decreased by 17% in control mice, while those fed green
tea catechins (0.35%) suffered no decline in endurance. The authors
concluded “long-term intake of catechins, together with habitual
exercise, is beneficial for suppressing the age-related decline in
physical performance and energy metabolism, and these effects are due,
at least in part, to improved mitochondrial function in skeletal
muscle.”

Tea catechin ingestion combined with habitual exercise suppresses
the aging-associated decline in physical performance in
senescence-accelerated mice.

Am J Physiol Regul Integr Comp Physiol. 2008 May 14. Murase T, Haramizu S, Ota N, Hase T.

Catechins, which are abundant in green tea, possess a variety of
biologic actions, and their clinical application has been extensively
investigated. In this study, we examined the effects of tea catechins
and regular exercise on the aging-associated decline in physical
performance in senescence-accelerated prone mice (SAMP1) and
age-matched senescence-accelerated resistant mice (SAMR1). The
endurance capacity of SAMR1 mice, measured as the running time to
exhaustion, tended to increase over the 8-week experimental period,
whereas that of SAMP1 mice decreased by 17%. On the other hand, the
endurance capacity of SAMP1 mice fed 0.35% (w/w) catechins remained at
the initial level and was significantly higher than that of SAMP1 mice
not fed catechins. In SAMP1 mice fed catechins and given exercise,
oxygen consumption was significantly increased, and there was an
increase in skeletal muscle fatty acid beta-oxidation. The mRNA levels
of mitochondria-related molecules, such as peroxisome
proliferator-activated receptor-gamma coactivator-1, cytochrome c
oxidase-II, III, and IV in skeletal muscle were also higher in SAMP1
mice given both catechins and exercise. Moreover, oxidative stress
measured as thiobarbituric reactive substances was lower in SAMP1
groups fed catechins than in the SAMP1 control group. These results
suggest that long-term intake of catechins, together with habitual
exercise, is beneficial for suppressing the aging-related decline in
physical performance and energy metabolism, and that these effects are
due, at least in part, to improved mitochondrial function in skeletal
muscle. Key words: energy metabolism, exercise, green tea,
mitochondria, oxidative stress.

Effect Of Green Tea Extract On Obese Women

February 24, 2009 by  
Filed under All, Science, Tea

Scientists in Taiwan studied the effect of green tea extract on 78
obese women aged 16 to 60 years. They found no significant improvement
in body weight, body mass index and weight circumflex. There were
significant improvements in LDL cholesterol and triglyceride.

Effect of green tea extract on obese women: A randomized, double-blind, placebo-controlled clinical trial.

Clin Nutr. 2008 May 9. [Epub ahead of print]. Hsu CH, Tsai TH, Kao YH, Hwang KC, Tseng TY, Chou P.

AIMS: To examine the effect of green tea extract (GTE) on obese
women and to explore the relationship between GTE and obesity-related
hormone peptides. METHODS: A randomized, double-blind,
placebo-controlled clinical trial was conducted from July 2006 to June
2007 in Taipei Hospital, Taiwan. Seventy-eight of 100 obese women aged
between 16 and 60years with BMI>27kg/m(2) and who had not received
any other weight control maneuvers within the last 3months completed
this study. The subjects were randomly divided into Groups A and B.
Group A (n=41) received GTE while Group B (n=37) took cellulose as a
placebo, one capsule (400mg) three times each day for 12weeks. The body
weight (BW), body mass index (BMI) and waist circumflex (WC) were
measured at the beginning of the study and after 12weeks of treatment
with GTE. The data were compared and expressed as % reduction. RESULTS:
There was only a 0.3% reduction in BW (0.15kg) after 12weeks of
treatment with GTE. There was no statistical difference in % reduction
in BW, BMI and WC between the GTE and placebo groups. Within group
comparison revealed that the GTE group had significant reduction in
LDL-cholesterol and triglyceride, and marked increase in the level of
HDL-cholesterol, adiponectin and ghrelin. On the other hand, the
placebo group showed significant reduction in triglyceride only, and a
marked increase in the level of ghrelin alone. CONCLUSIONS: This study
showed no statistical difference in % reduction in BW, BMI and WC
between the GTE and placebo groups after 12weeks of treatment. The
intake of GTE (491mg catechins containing 302mg EGCG) for 12weeks is
considered safe as shown by the results.

Green Tea Polyphenols Protect The Skin

February 24, 2009 by  
Filed under All

Green tea polyphenols have been reported to preserve tissues such as
blood vessels, corneas, nerves, islet cells, articular cartilage, and
myocardium. Research in Japan examined the effects of EGCG on skin
preservation. Utilizing epidermal and dermal skin cells in culture, the
researchers report that the tea polyphenol helped to preserve the skin
cells for up to seven weeks and allowed successful skin grafting. The
researchers commented that these findings suggest “the future
clinical usefulness of EGCG for skin preservation, however the
mechanism by which EGCG promotes skin preservation still remains
unclear.”

Green tea polyphenols affect skin preservation in rats and improve the rate of skin grafts.

Cell Transplant. 2008;17(1-2):203-9. Kawazoe T, Kim H, Tsuji Y, Morimoto N, Hyon SH, Suzuki S.
Green tea polyphenols have been recently reported to promote the
preservation of tissues, such as blood vessels, corneas, nerves, islet
cells, articular cartilage, and myocardium, at room temperature. These
findings indicate the possibility of a new method of tissue banking
without freezing. A main active ingredient of green tea,
epigallocatechin-3-gallate (EGCG), is a polyphenol that possesses
antioxidant, antimicrobial, antiproliferative, and free radical
scavenging effects. This study examined the effects of EGCG regarding
skin preservation. Skin sample biopsy specimens measuring 1 x 1 cm from
GFP rats were held in sterile containers with 50 ml preserving solution
at 4 degrees C and 37 degrees C for up to about 8 weeks. Periodically,
some of the preserved skin specimens were directly examined
histologically and others were transplanted into nude mice.
Histological examinations of skin preserved at 4 degrees C revealed a
degeneration of the epidermal and dermal layers from 5 weeks in all
groups. In the groups preserved at 37 degrees C, degeneration and
flakiness of the epidermal layer were demonstrated starting at 2 weeks
preservation regardless of addition of EGCG. After 2-7 weeks of
preservation the rat skin grafted to nude mice in the EGCG groups
stored at 4 degrees C showed successful engraftment. However, grafts
preserved at 4 degrees C without EGCG and at 37 degrees C did not
demonstrate GFP-positive keratinocyte or fibroblasts. In conclusion,
the present findings suggest the future clinical usefulness of EGCG for
skin preservation without freezing; however, the mechanism by which
EGCG promotes skin preservation still remains unclear.

Green Tea for Keloids

February 24, 2009 by  
Filed under All, Science, Tea

New research from Korea shows that EGCG selectively suppressed
keloid fibroblast proliferation and migration compared to its effect on
normal fibroblast proliferation and migration. Keloids are common
benign skin tumors, characterized by collagen accumulation and
hyperproliferation of fibroblasts.

Green Tea Polyphenol Epigallocatechin-3-Gallate Suppresses Collagen
Production and Proliferation in Keloid Fibroblasts via Inhibition of
the STAT3-Signaling Pathway.

J Invest Dermatol. 2008 May 8. Park G, Yoon BS, Moon JH, Kim B, Jun EK, Oh S, Kim H, Song HJ, Noh JY, Oh C, You S.

Keloids are benign skin tumors characterized by collagen
accumulation and hyperproliferation of fibroblasts. To find an
effective therapy for keloids, we explored the pharmacological
potential of (-)-epigallocatechin-3-gallate (EGCG), a widely
investigated tumor-preventive agent. When applied to normal and keloid
fibroblasts (KFs) in vitro, proliferation and migration of KFs were
more strongly suppressed by EGCG than normal fibroblast proliferation
and migration (IC(50): 54.4 muM (keloid fibroblast (KF)) versus 63.0
muM (NF)). The level of Smad2/3, signal transducer and activator of
transcription-3 (STAT3), and p38 phosphorylation is more enhanced in
KFs, and EGCG inhibited phosphorylation of
phosphatidylinositol-3-kinase (PI3K), extracellular signal-regulated
protein kinase 1/2 (ERK1/2), and STAT3 (Tyr705 and Ser727). To evaluate
the contribution of these pathways to keloid pathology, we treated KFs
with specific inhibitors for PI3K, ERK1/2, or STAT3. Although a PI3K
inhibitor significantly suppressed proliferation, PI3K and MEK/ERK
inhibitors had a minor effect on migration and collagen production.
However, a JAK2/STAT3 inhibitor and a STAT3 siRNA strongly suppressed
proliferation, migration, and collagen production by KFs. We also found
that treatment with EGCG suppressed growth and collagen production in
the in vivo keloid model. This study demonstrates that EGCG suppresses
the pathological characteristics of keloids through inhibition of the
STAT3-signaling pathway. We propose that EGCG has potential in the
treatment and prevention of keloids.Journal of Investigative
Dermatology advance online publication, 8 May 2008;
doi:10.1038/jid.2008.103.

Green Tea Catechin Polyphenols Attenuate Behavioral and Oxidative Responses to Intermittent Hypoxia

May 25, 2008 by  
Filed under Tea

Rationale: The intermittent hypoxia (IH) that characterizes sleep disordered breathing impairs spatial learning and increases NADPH oxidase activity and oxidative stress in rodents. We hypothesized that green tea catechin polyphenols (GTPs) may attenuate IHinduced neurobehavioral deficits by reducing IH-induced NADPH oxidase expression, lipid peroxidation, and inflammation.

Conclusions: Oral GTP attenuates IH-induced spatial learning deficits and mitigates IH-induced oxidative stress through multiple beneficial effects on oxidant pathways. Because oxidative processes underlie neurocognitive deficits associated with IH, the potential therapeutic role of GTP in sleep-disordered breathing deserves further exploration.

Green Tea Polyphenol Administration Partly Ameliorates Chemotherapy-Induced Side Effects in the Small Intestine of Mice

May 25, 2008 by  
Filed under Science

Abstract

The chemotherapeutic agent irinotecan (IT) is highly effective
against several types of cancer, although its use is limited due to
severe intestinal toxicity. The aim of this study was to evaluate
inflammatory and oxidative stress-related processes contributing to
small intestinal mucosa damage and to determine the extent to which
green tea polyphenols could ameliorate the detrimental effects induced
by IT. In Expt. 1, mice were challenged intraperitoneally with IT or
saline on 2 consecutive days. For time kinetic measurements, the
IT-treated mice were killed at 3, 24, 48, 72, and 96 h after the 2nd
dose of IT. Three hours after IT administration, the ileum glutathione
concentration dropped significantly. Lipid peroxidation and
inflammation, as measured by macrophage inflammatory protein-2 content,
myeloperoxidase activity, and nuclear factor-κB translocation,
were highest between 24 and 48 h after IT treatment. In Expt. 2, green
tea polyphenols (1 g/L) were supplied via drinking water for 7 d before
and 3 d after treatment with IT. Green tea polyphenols significantly
affected the glutathione:glutathione disulfide ratio but not lipid
peroxidation, macrophage inflammatory protein-2 levels, myeloperoxidase
activity, or nuclear factor-κB activation. Our study reveals that
IT administration is associated with oxidative stress and inflammation,
both occurring simultaneously to IT-induced mucosal damage. The
antioxidative defense is affected soon after IT administration. Green
tea polyphenols supplied orally protected against oxidation in our
experimental model and could be one approach to reducing the risk of
IT-induced side effects in the clinical setting. J. Nutr. 137: 634-640,
2007.

« Previous PageNext Page »