Effectiveness of Green Tea in a Randomized Human Cohort: Relevance to Diabetes and Its Complications

ANDI Centre of Excellence for Biomedical and Biomaterials Research and Department of Biosciences University of Mauritius, Réduit, Mauritius.
BioMed research international 09/2013; 2013(4):412379. DOI: 10.1155/2013/412379
Source: PubMed
ABSTRACT
Epidemiological studies have argued that green tea could mitigate diabetes and its complications. This study investigated the phytophenolic profile of Mauritian green tea and its antioxidant propensity. The effect of green tea on the risk factors: waist-hip ratio, glucose level, arterial pressure, antioxidant status, and alanine aminotransferase (ALT) in prediabetics was assessed. The experimental group consumed 3 cups of green tea daily for 14 weeks followed by a 2-week washout period. The control group followed a water regimen. Green tea contained high level of phenolics related to its antioxidant power. Green tea suppressed waist-hip ratio of women from a significant increase and suppressed mean arterial pressure of men and women from a significant decrease after week 14. It reduced ALT level in women by 13.0% (P < 0.1) while increasing the antioxidant potential of men and women sera by 2.7% (P < 0.1) and 5.1% (P < 0.1). The study timescale may have been too short to enable demonstration of effects on fasting plasma glucose and HbA1c outcomes. Green tea regimen could form part of a healthy lifestyle that might ameliorate features of metabolic syndrome and subsequent risks for diabetes and its complications. This trial is registered with ClinicalTrials.gov NCT01248143.

Full-text

Available from: Theeshan Bahorun, May 13, 2014
Hindawi Publishing Corporation
BioMed Research International
Volume , Article ID ,  pages
http://dx.doi.org/.//
Clinical Study
Effectiveness of Green Tea in a Randomized Human Cohort:
Relevance to Diabetes and Its Complications
Naushad Ali Toolsee,
1
Okezie I. Aruoma,
2
Teeluck K. Gunness,
3
Sudhir Kowlessur,
4
Venkatesh Dambala,
5
Fatima Murad,
6
Kreshna Googoolye,
7
Diana Daus,
8
Joseph Indelicato,
8
Philippe Rondeau,
9
Emmanuel Bourdon,
9
and Theeshan Bahorun
1
1
ANDI Centre of Excellence for Biomedical and Biomaterials Research and Department of Biosciences University of Mauritius,
R
´
eduit, Mauritius
2
School of Pharmacy and Biomedical Sciences, American University of Health Sciences, Signal Hill, CA 90755, USA
3
Cardiac Centre, Sir Seewoosagur Ramgoolam National Hospital, Pamplemousses, Mauritius
4
Non-Communicable Diseases Unit, Ministry of Health and Quality of Life, Port Louis, Mauritius
5
Department of Biochemistry, Apollo Bramwell Hospital, Moka, Mauritius
6
Centre for Clinical Research and Education, Apollo Bramwell Hospital, Moka, Mauritius
7
Human Resource Development Council, NG Tower, Ebene, Mauritius
8
Department of Occupational erapy, Touro College of Health Sciences, Bay Shore, NY 11706, USA
9
Groupe d’Etude sur lInammation Chronique et l’Ob
´
esit
´
e, Universit
´
edeLaR
´
eunion, Plate-forme CYROI, Saint Denis,
97400LaR
´
eunion, France
Correspondence should be addressed to Okezie I. Aruoma; oaruoma@auhs.edu and eeshan Bahorun; tbahorun@uom.ac.mu
Received April ; Revised  July ; Accepted August 
Academic Editor: Yvonne F. Heerkens
Copyright ©  Naushad Ali Toolsee et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Epidemiological studies have argued that green tea could mitigate diabetes and its complications. is study investigated the
phytophenolic prole of Mauritian green tea and its antioxidant propensity. e eect of green tea on the risk factors: waist-hip
ratio, glucose level, arterial pressure, antioxidant status, and alanine aminotransferase (ALT) in prediabetics was assessed. e
experimentalgroupconsumedcupsofgreenteadailyforweeksfollowedbya-weekwashoutperiod.econtrolgroup
followed a water regimen. Green tea contained high level of phenolics related to its antioxidant power. Green tea suppressed waist-
hip ratio of women from a signicant increase and suppressed mean arterial pressure of men and women from a signicant decrease
aer week . It reduced ALT level in women by .% (𝑃 < 0.1) while increasing the antioxidant potential of men and women sera by
.% (𝑃 < 0.1)and.%(𝑃 < 0.1). e study timescale may have been too short to enable demonstration of eects on fasting plasma
glucose and HbAc outcomes. Green tea regimen could form part of a healthy lifestyle that might ameliorate features of metabolic
syndrome and subsequent risks for diabetes and its complications. is trial is registered with ClinicalTrials.gov NCT.
1. Introduction
Diabetes has been shown to be a chronic metabolic disorder
of multiple aetiologies. e socioeconomic suering is enor-
mous. Diabetes, characterized by a state of insulin deciency
that leads to a rise in glycemia [], is commonly classied as
insulin-dependent diabetes mellitus (type , an autoimmune
disease where 𝛽-cells of the pancreas are aected by the body’s
defence system) and noninsulin-dependent diabetes mellitus
(type , a metabolic disorder characterized by insulin resis-
tance and deciency). Reactive radical species are formed via
a number of pathways during hyperglycemia []. Under
normal glycemic condition, glucose primarily undergoes
glycolysis and oxidative phosphorylation whereas under
hyperglycemic state, glucose could swamp the glycolytic pro-
cess and hinder glyceraldehyde catabolism, thereby causing
fructose-,-bisphosphate and glyceraldehyde--phosphate
to be channelled to other pathways such as enolization and
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BioMed Research International
𝛼-ketoaldehyde formation; protein kinase C activation; hex-
osamine metabolism; sorbitol metabolism; dicarbonyl forma-
tion and glycation. ese combined biochemical pathways
play a cardinal role in the pathogenesis of diabetes, whose
therapeutic management is argued here to potentially benet
from adjunct inclusion of dietary biofactors in functional
beverages [, ].
e physiological eects of polyphenol-rich beverages
have continued to receive considerable attention as healthful
dietary sources of antioxidants [, ]. is growing body of
evidence advocates the role of green tea or its bioactive pol-
yphenolic compounds in ameliorating features of metabolic
syndrome and subsequent risks for type diabetes [, ].
Green tea contains important phytochemicals such as cat-
echins, gallic acid, caeic acid, kaempferol, myricetin, and
quercetin []. ese green tea polyphenols showed antiox-
idant activities in vitro by scavenging reactive radical species
and function indirectly as antioxidants through inhibition of
redox-sensitive transcription factors; inhibition of “prooxi-
dant” enzymes; and induction of antioxidant enzymes [, ].
Several studies have shown that green tea controls glomerular
ltration rate, lowers albuminuria, attenuates hypertension,
prevents free radical generation in cardiac myocytes, and
reduces renal advanced glycation end-product in diabetic
nephropathy model rats []. In this study, the phytophe-
nolic proles of a green tea infusate were determined, and
its antioxidant potential was evaluated using a multiassay
approach. e potential modulatory eects of green tea
consumption on some selected parameters including waist-
hip ratio, glucose level, arterial pressure, antioxidant status,
alanine aminotransferase, and lipid proles were assessed,
over a dened period of time, in individuals inclined to
develop type diabetes.
2. Materials and Methods
2.1. Reagents. ,
󸀠
-Azobis(-methylpropionamidine)dihydro-
chloride (AAPH) was obtained from Sigma-Aldrich, Inc. (St.
Louis, MO, USA). Clinical biochemistry reagent kits were
purchased from Beckman Coulter Inc. (Brea, CA, USA) and
Randox Laboratories Ltd. (Dublin, UK).
2.2. Plant Material. Camellia sinensis var. sinensis (Chinese
Jat)wasobtainedashomogenousgreenteabags(nished
product) from Bois Ch
´
eri Tea Estate (Bois Ch
´
eri, Republic
of Mauritius). e tea bag, containing approximately g of
green tea, was manufactured on November .
2.3. Total Phenol Content. Phenol was determined by the
method of Singleton and Rossi [].
2.4. Total Flavonoid Content. Flavonoid was determined by
the method of Lamaison and Carnet [].
2.5. Total Proanthocyanidin Content. Proanthocyanidin was
determined by the method of Porter et al. [].
2.6. High-Performance Liquid Chromatography
2.6.1. Sample Preparation. One green tea bag was infused in
 mL hot water (
C)forminutesasdescribedbyWang
et al. []. e brew was cooled under running tap water and
centrifuged at  rpm for  minutes at 
C. For gallic
acid, (+)-catechin, ()-epigallocatechin, ()-epigallocatechin
gallate, ()-epicatechin gallate, procyanidin B, and ()-
epicatechin analyses, the supernatant was mixed with abso-
lute methanol in a : supernatant : methanol, v/v ratio prior
to HPLC analysis.
Myricetin, kaempferol, and quercetin were identied and
quantied in green tea infusate aer acid hydrolysis of
avonol conjugates, essentially as follows and using morin
as internal standard: the supernatant was mixed with M
HCLina:supernatant:MHCL,v/vratioandincubated
at
C for . hours. Aer cooling, the hydrolysed green
tea supernatant extract was taken up in absolute methanol
( : v/v, hydrolysed green tea extract : absolute methanol)
prior to HPLC analysis.
2.6.2. Chromatographic Conditions. HPLC analysis of the
green tea infusate was carried out using a Hewlett Packard
 series (Waldbronn, Germany) liquid chromatography
system equipped with a vacuum degasser, quaternary pump,
autosampler, thermostated column compartment, and diode
array detector. Aer ltration (. 𝜇m lter paper) (Mil-
lipore Corporation, Bedford, USA),  𝜇L of extract was
injected into a Zorbax SB-C column (. mm internal
diameter ×  mm length, . 𝜇m pore size) (Agilent Tech-
nologies, CA, USA). Elution with a ow rate of . mL/min
at 
C was as follows: – min, –% B in A; – min,
–% B in A; – min, –% B in A; – min, –
%BinA;min,%BinA.(SolventA:ace-
tonitrile/water, / v/v, pH .; Solvent B: acetonitrile/water,
/ v/v, pH .; adjusted with phosphoric acid). e diode
array detector was set at  nm for the quantitative determi-
nation of gallic acid and avan--ol derivatives and at  nm
for avonol aglycones. e identication and quantication
of these phenolics were determined from retention times
and peak areas in comparison with authentic standards.
Results were expressed in appropriate standards (mg) per
cup ( mL). Green tea extracts were analysed in triplicate.
Calibrated graphs of authentic standards were prepared
via appropriate serial dilutions with methanol and ltered
(. 𝜇m) before use. Calibration graphs were obtained by
plotting the peak area of authentic standards versus their
known quantities (.–. 𝜇g).
2.7. Sample Preparation for Antioxidant and Free Radical-
Induced Hemolysis Assays. Two grams of green tea (equiva-
lent to tea bag) were infused in  mL hot water (
C)
for minutes. e green tea brew was cooled under running
tap water and ltered through a . 𝜇mnylonlter.ebrew
was diluted to generate dierent concentrations of green tea
extracts (. mg/mL to  mg/mL) for use in antioxidant and
free radical-induced hemolysis assays.
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2.7.1. Antioxidant Assays
(1) Superoxide Radical Scavenging Assay. e superoxide
anion radical scavenging activity of green tea was measured
according to Nishikimi et al. []withslightmodications.
(2) Nitric Oxide Radical Scavenging Assay. e nitric oxide
radical scavenging activity of green tea was measured accord-
ing to Garratt []withslightmodications.
(3) 2,2
󸀠
-Azino-bis (3-Ethylbenzothiazoline-6-sulfonic Acid)
Radical Scavenging Assay. e ABTS
∙+
scavenging activity of
green tea was measured according to Henriquez et al. []
with slight modications.
(4)FerricReducingAntioxidantPowerAssay.e ferric reduc-
ing activity of green tea was measured according to Benzie
and Strain []withslightmodications.
(5) 2,2-Diphenyl-1-picrylhydrazyl Radical Scavenging Assay.
e DPPH scavenging activity of green tea was measured
according to Sharma and Bhat []withslightmodications.
(6) Ferrous Ion Chelating Assay. e ferrous ion chelating
activity of green tea was assessed according to Stookey []
with slight modications.
(7) Hypochlorous Acid Scavenging Assay. e hypochlorous
acid scavenging activity of green tea was assessed according
to Wang et al. []andAruomaandHalliwell[].
2.7.2. Free Radical-Induced Hemolysis Assay. e antioxidant
activities of green tea extracts and human sera, derived from
theclinicaltrial,wereevaluatedusinganassaybasedonfree
radical-induced hemolysis [].
2.8. Clinical Trial
2.8.1. Subjects. ree hundred prediabetic Mauritians, who
participated in a  nationwide survey that was organized
by the Non-Communicable Diseases Unit of the Ministry
of Health and Quality of Life, Republic of Mauritius, were
selected for the randomized controlled clinical trial (Clinical-
Trials.gov Identier—NCT). e inclusion criteria
were individuals at risk of diabetes (fasting plasma glucose
ranged from  to  mg/dL, measured using the hexokinase
method);agerangedfromtoyears.eexclusion
criteria were smokers or those who have stopped smoking
months before the clinical trial; daily alcoholic intake exceed-
ing two standard drinks; postmenopausal women receiv-
ing hormone replacement therapy; hypertensive patients
(>/ mmHg). e clinical trial was approved by the
National Ethics Committee of the Ministry of Health and
Quality of Life, Republic of Mauritius and endorsed by
the Institutional Review Board at Touro College of Health
Sciences (Bay Shore, NY, USA). e study was conducted in
accordance with the guidelines of the Declaration of Helsinki
principles. All subjects gave written informed consent before
clinical trial enrolment.
2.8.2. Trial Prole and Study Design. e clinical trial was
conductedfromNovembertoMarchattheCar-
diac Centre of the Sir Seewoosagur Ramgoolam National
Hospital, Pamplemousses, Republic of Mauritius, over a -
week period. e experimental group (𝑛=65)consumed
onecupofgreenteainfusate(greenteabaginfusedfor
min in  mL hot water without milk or sugar) three
times a day before meals (breakfast, lunch, and dinner) for
 weeks, followed by a -week washout period. e control
group (𝑛=58)consumedanequivalentvolumeofwarm
water during the -week period (Figure ). e random
allocation sequence was generated by a qualied statistician
using a random generator that takes into account an unbiased
age and gender distribution within each group. A simple
randomization approach with blocking for gender was used
to allocate subjects into their respective groups. Participants
were instructed to maintain their usual daily activities and
their former diet during the clinical trial.
2.8.3. Dietary Survey Questionnaires. Participants were con-
tacted twice a week via phone to remind them to keep
arecordofallfoodandbeveragesconsumedduringthe
clinical trial. A questionnaire indicating food and beverage
items consumed daily during the three main meals was
issued to each participant and was collected duly lled aer
blood sampling exercise. Dietary information provided by the
participants enabled the assessment of any possible changes
in the diet during the clinical trial. Descriptive statistics of
these questionnaires were based on daily mean calorie index
and daily lipid/fat ratio [] observed during the -week
intervention period and the -week washout period.
2.8.4. Anthropometry and Blood Pressure. Anthropometric
and blood pressure data were recorded for each participant.
Height was measured to the nearest . cm without shoes
using a calibrated stadiometer. Weight was measured without
shoes and excess clothing to the nearest . kg using a
calibrated mechanical beam balance. BMI was calculated as
weight in kilograms divided by height in square meters. Waist
and hip circumference was measured to the nearest . cm
using a dressmakers measuring tape applied horizontally.
Waist girth was measured at the midpoint between the iliac
crest and the lower margin of the ribs. Hip girth was recorded
as the maximum circumference around the buttocks. Waist-
hip ratio was calculated as waist in cm divided by hip in
cm. Blood pressure was measured on the right upper arm,
in seated and supine position, aer resting for ve minutes,
with an automatic device (Automatic blood pressure monitor
Model SEM-, Omron Healthcare Company, Singapore). Two
measurements were taken, with minute interval between
them, and the mean of the measurements was calculated.
ese blood pressure values were used to calculate mean
arterial pressure using the standard formula / diastolic
blood pressure + / systolic blood pressure.
2.8.5. Sample Collection.  mL of blood was collected, under
the guidance of physicians, from each participant fasting
for at least  hours. e blood was dispensed appropriately
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145 declined to participate
155 randomly allocated to
Experimental group
(male, n = 40; female, n = 37)
Control group
(male, n = 43; female, n = 35)
Completed 16-week period
(male, n = 33; female, n = 32)
(male, n = 30; female, n = 28)
300 participants met inclusion criteria and were invited to participate in the clinical study
Green tea regimen
1 cup of green tea 3 times a day before
meals for 14 weeks
Water regimen
1 cup of warm water 3 times a day before
meals for 14 weeks
Washout period
1 cup of warm water 3 times a day before
meals for 2 weeks
1 cup of warm water 3 times a day before
meals for 2 weeks
intervention
12 lost to followup or discontinued 12 lost to followup or discontinued
intervention
Washout period
Completed 16-week period
F : Flow diagram showing trial prole and study design.
into EDTA-K tube, sodium uoride oxalate tube, and plain
tubes. Biological samples were kept at
Candtransported,
for analysis, to Apollo Bramwell Hospital, Moka, Republic
of Mauritius. Before conducting any assays, all tubes were
centrifuged at  rpm for min at 
Cwiththeexception
of EDTA-K tube. Human sera from plain tubes were used
for free radical-induced hemolysis and clinical biochemistry
assay. Whole blood from EDTA-K tubes and human plasma
from sodium uoride oxalate tubes were used only for clinical
biochemistry assay.
2.8.6. Clinical Biochemistry Assay. Human sera obtained
from plain tubes were tested for total cholesterol, LDL, HDL,
triglycerides, urea, albumin, creatinine, ferritin, total antiox-
idant status, aminotransferase aspartate (AST), and ALT.
Human plasma obtained from sodium uoride oxalate tubes
were tested for glucose. Whole blood from EDTA-K tube
was used to determine glycated haemoglobin. Using stan-
dardized methods, the automated Beckman Coulter AU
analyzer was used to quantify all biomarkers, except total
antioxidant status which was evaluated by RX Daytona ana-
lyzer. All clinical biochemistry assays were completed within
 h aer sample collection. Serum creatinine (nonisotope
dilution mass spectrometry traceable), urea, and albumin
were used to estimate glomerular ltration rate (eGFR), using
the “modication of diet in renal disease (MDRD) formula
[].
2.9. Statistical Analysis. Parametric and nonparametric vari-
ables are expressed, aer omitting outliers, as mean ± stan-
dard deviation and median [interquartile range], respec-
tively. Simple regression analysis was performed to calculate
the dose-dependent relationship of green tea extracts in
dierent antioxidant assays. Data derived from antioxidant
assays were tted into appropriate regression model [](lin-
ear, polynomial order or polynomial order ) that allowed
us to determine AA
50
. Statistical inference was carried out,
aer omitting outliers, using MedCalc for Windows (version
...; Mariakerke, Belgium). Signicant dierences over
time, within each group, were determined using paired
Student’s 𝑡-test, and where data was not normal the non-
parametric alternative Wilcoxon test was used. Signicant
dierences over time, between each group, were determined
using independent samples 𝑡-test and where data was not
normal the nonparametric alternative Mann-Whitney test
was used. e level for establishing signicant dierences
was set at % successively. Statistical analyses were also
performed to calculate any signicant correlations between
individual variables, daily mean calorie index, and daily,
lipid/fat ratio. Pearson or Spearman rank correlation coe-
cientwasusedfornormallyornonnormallydistributeddata
sets, respectively. Correlation analyses between individual
variables, daily mean calorie index, and daily lipid/fat ratio
were carried out separately on week  and washout data sets
whereby gender stratied data were taken into account. All
statistical tests were two-tailed.
3. Results
3.1. Phytophenolic Composition of Mauritian Green Tea. e
Mauritian green tea phytophenolic prole is shown in
Table . e most prominent phytophenolics, in an unhy-
drolyzed Mauritian green tea infusate, were ranked accord-
ing to their quantity per cup ( mL), in the following
decreasing order: procyanidin B > ()-epigallocatechin
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T : Mauritian green tea phytophenolic data.
Phytophenolic of unhydrolyzed Mauritian green tea/mg per cup
( mL)
Total phenol . ± .
a
Total avonoid . ± .
b
Total proanthocyanidin . ± .
b
Procyanidin B . ± .
c
()-Epigallocatechin gallate . ± .
d
()-Epigallocatechin . ± .
e
()-Epicatechin gallate . ± .
f
()-Epicatechin . ± .
g
(+)-Catechin . ± .
h
Gallic acid . ± .
i
Phytophenolics in hydrolyzed Mauritian green tea/mg per cup
( mL)
Quercetin . ± .
j
Myricetin . ± .
j
Kaempferol . ± .
k
Data are expressed as mean ± standard deviation (𝑛=3). Statistical analyses
were performed, using independent samples t-test, for multiple comparisons.
Dierent alphabetical superscripts between rows represent signicant dif-
ferences between mean phytophenolic contents (𝑃 < 0.05). Free avonoids
were not detected in the green tea extract; however, aer hydrolysis, HPLC
analysis showed that quercetin, kaempferol, and myricetin were the main
avonol aglycones present in the following decreasing order: quercetin >
myricetin > kaempferol.
gallate > ()-epigallocatechin > ()-epicatechin gallate > ()-
epicatechin > (+)-catechin > gallic acid. Procyanidin B was
found to be the most important compound with . mg
per cup ( mL) while gallic acid was least prominent
(. mg per cup).
3.2. Antioxidant Capacities of Mauritian Green Tea. e
green tea antioxidant prole was characterized using inde-
pendent assays (Table ) at concentrations varying from
. to mg/mL. A concentration ranking order indicat-
ing % antioxidant activity (AA
50
) for the green tea ex-
tract in each antioxidant assay was established as follows:
ABTS
∙+
scavenging activity (. mg/mL) > ferric reduc-
ing activity (. mg/mL) > nitric oxide scavenging activ-
ity (. mg/mL) > Fe
2+
chelating activity (. mg/mL) >
HOCL scavenging activity (. mg/mL) > superoxide scav-
enging activity (. mg/mL) > DPPH scavenging activity
(. mg/mL). e data showed that the Mauritian green
tea extract had a higher predisposition (𝑃 < 0.05)tothe
ABTS
∙+
radical than the DPPH radical. It also revealed a
nonsignicant (𝑃 > 0.05) sensitivity to hypochlorous acid
and superoxide anion radical. Moreover, Mauritian green tea
had a higher anity (𝑃 < 0.05)toreduceFe
3+
into Fe
2+
than
to chelate Fe
2+
.
3.3. Clinical Trial. A randomized controlled clinical trial
was conducted on humans predisposed to type diabetes.
Among the  participants that met the inclusion criteria,
T : Antioxidant activities of Mauritian green tea using a mul-
tiassay approach.
Antioxidant assays AA

(mg/mL)
ABTS radical scavenging assay . ± .
a
FRAP assay . ± .
b
Nitric oxide radical scavenging assay . ± .
c
Ferrous ions chelating assay . ± .
c,d
HOCL scavenging assay . ± .
d,e
Superoxide radical scavenging assay . ± .
e
DPPH radical scavenging assay . ± .
f
Data are expressed as mean ± standard deviation (𝑛=3). Statistical analyses
were performed, using independent samples t-test, for multiple comparisons.
Dierent alphabetical superscripts between rows represent signicant dier-
ences between mean AA

(𝑃 < 0.05). AA

wasdenedasMauritiangreen
tea concentration that revealed a % antioxidant activity.
 agreed to enrol in the clinical trial and they were randomly
allocated into the experimental and control group. e num-
ber of participants at the end of the clinical trial was ,
representing a .% dropout from initial population size.
e nal experimental and control groups consisted of 
and participants, respectively. No subject withdrew from
the clinical trial due to discomfort or any adverse eects
associatedwiththeregimen.ecomplieddietarysurvey
questionnaires showed that the daily mean calorie index and
daily lipid/fat ratio remained relatively constant for both the
experimental and control groups in the male and female
population during the -week intervention period and the
-week washout period (Figures and ). No correlation
analyses between individual variables, daily mean calorie
index, and daily lipid/fat ratio for any group or gender turned
out to be signicant, nor were there any consistency in the
direction of correlations.
e data in Tables and dene the anthropometric
and biochemical characteristics measured at the beginning
of the study, at the end of the -week intervention period,
and aer the -week washout period. During the clinical trial,
waist-hip ratio, an indicator of obesity, increased signicantly
(𝑃 < 0.1) in the female control group whereas the female
experimental group did not experience any change on week
. Mean arterial pressure, dened as the average arterial pres-
sure during a single cardiac cycle, decreased insignicantly on
week  as indicated by the experimental group whereas male
and female control groups endured a critical decline of .%
(𝑃 < 0.1)and.%(𝑃 < 0.1), respectively.
Based on the ndings set out in Table ,malesubjects
under green tea regimen showed an insignicant reduction of
.% in ferritin concentration aer week  whereas in male
control group its concentration rose considerably by .%
(𝑃 < 0.1). Moreover, the green tea regimen did not aect the
fasting plasma glucose of subjects.
eGFR, used to diagnose and monitor kidney function,
was estimated using the -variable MDRD study equation.
During the -week period, eGFR increased insignicantly
in the male control group. e male experimental group
experienced a signicant decrease of .% (𝑃<0.1)aerweek
Page 5
BioMed Research International
T : Characteristics of male participants (𝑛) at baseline, aer -week intervention period, and aer -week washout period.
Var iables
Male green tea group Male control group
n Baseline Week Washout n Baseline Week  Washout
Age (year)  48.9 ± 6.9  48.1 ± 7.9
Weight (kg) 70.8 ± 13.6 71.6 ± 13.5 71.4 ± 13.8  75.3 ± 13.3 75.9 ± 13.6 75.4 ± 13.4
BMI (kg/m
)24.67 ± 3.69 24.97 ± 3.70 (.)
24.87 ± 3.78 (.)
 26.28 ± 4.76 26.46 ± 4.79 (.)
26.23 ± 4.71 (.)
Waist-hip ratio  0.91 ± 0.06 0.90 ± 0.06 (.) 0.89 ± 0.05 (.)
 0.92 ± 0.05 0.91 ± 0.06 (.) 0.90 ± 0.04 (.)
MAP
a
(mmHg)  93.49 ± 9.48 92.85 ± 9.06 (.) 92.67 ± 10.59 (.)  95.62 ± 8.70 92.76 ± 8.73 (.)
92.29 ± 8.88 (.)
Glucose (mg/dL)  89.70 ± 11.18 90.47 ± 11.65 (.) 92.87 ± 9.45 (.)  90.56 ± 10.35 87.56 ± 11.66 (.) 89.15 ± 11.18 (.)
HbAc (%)  . [.–.] . [..] . [.–.]
 . [.–.] . [.–.]
. [.–.]
Cholesterol (mg/dL)  218.75 ± 40.39 195.91 ± 34.52 (.)
199.19 ± 32.72 (.)
 215.45 ± 40.01 184.86 ± 35.34 (.)
194.10 ± 42.06 (.)
Triglycerides (mg/dL)  125.42 ± 54.97 127.77 ± 55.66 (.) 115.55 ± 48.38 (.)  124.96 ± 47.71 115.58 ± 41.15 (. ) 108.04 ± 38.81 (.)
LDL (mg/dL)  145.28 ± 33.72 131.47 ± 28.53 (.)
134.94 ± 26.89 (. ) 147.89 ± 37.34 128.26 ± 26.97 (.)
136.44 ± 35.99 (. )
HDL (mg/dL)  48.58 ± 10.92 42.81 ± 11.05 (.)
44.00 ± 10.31 (.)
 45.54 ± 9.41 38.89 ± 8.30 (.)
40.86 ± 9.26 (.)
LDL/HDL  3.11 ± 0.85 3.22 ± 0.75 (.) 3.22 ± 0.77 (.)  3.38 ± 1.03 3.29 ± 0.62 (.) 3.41 ± 0.76 (.)
Ferritin (ng/dL)  100.45 ± 72.68 97.41 ± 65.48 (.) 98.97 ± 65.49 (.)  80.04 ± 47.12 111.42 ± 75.86 (.)
107.65 ± 72.83 (.)
Albumin (g/dL)  4.50 ± 0.23 4.43 ± 0.20 (.) 4.48 ± 0.20 (.)  4.50 ± 0.23 4.41 ± 0.23 (.)
4.47 ± 0.20 (.)
Serum creatinine (mg/dL)  . [.–.] . [.–.] . [.–.]  . [.–.] . [.–.] . [.–.]
Urinary creatinine (mg/dL)  131.52 ± 65.76 188.17 ± 94.65 (.)
170.66 ± 76.81 (.)
 138.31 ± 70.17 200.38 ± 64.94 (.)
197.38 ± 80.27 (.)
Urea (mg/dL)  14.42 ± 4.66 14.65 ± 3.89 (.) 15.48 ± 3.94 (.)  13.63 ± 2.62 13.85 ± 3.59 (.) 12.52 ± 2.64 (.)
eGFR
b
(mL/min per . m
) 82.62 ± 16.73 76.74 ± 9.00 (. )
79.64 ± 11.26 (.) 81.92 ± 14.24 84.24 ± 13.79 (.)
85.55 ± 15.35 (.)
AST
c
(IU/L)  26.35 ± 6.22 26.41 ± 5.11 (.) 26.79 ± 5.54 (.) 27.11 ± 7.37 26.93 ± 7.35 (.) 27.11 ± 7.21 (.)
ALT
d
(IU/L)  29.09 ± 16.64 27.06 ± 13.45 (.) 27.81 ± 11.39 (.)  28.25 ± 12.99 27.54 ± 11.33 (.) 28.61 ± 12.25 (.)
TAS
e
(mmol/L)  1.60 ± 0.15 1.75 ± 0.11 (.)
1.92 ± 0.14 (.)
 1.62 ± 0.13 1.72 ± 0.10 (.)
1.92 ± 0.17 (.)
Human sera HT (minutes) 165.5 ± 25.7 170.0 ± 27.2 (.)
173.4 ± 26.5 (.)
 181.4 ± 31.3 176.1 ± 25.5 (.) 178.0 ± 29.1 (.)
Parametric variables are expressed as mean ±standard deviation, whereas nonparametric variables are expressed as median [interquartile range]. Percentage changes relative to baseline meansareindicatedinround
brackets.
Mean or median value is signicantly dierent from that of baseline (𝑃<0.1)(comparewithinrowandwithingroup).
Mean or median value is signicantly dierent from that of week  (𝑃<0.1)
(compare within row and between group).
a
Mean arterial pressure;
b
estimated glomerular ltration rate;
c
aminotransferase aspartate;
d
aminotransferase alanine;
e
total antioxidant status.
Page 6
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T : Characteristics of female participants (𝑛) at baseline, aer -week intervention period, and aer -week washout period.
Var iables
Female green tea group Female control group
n Baseline Week Washout n Baseline Week  Washout
Age (year)  49.3 ± 6.6  46.9 ± 8.4
Weight (kg) 61.3 ± 12.2 61.9 ± 12.4 61.7 ± 12.4  63.2 ± 9.8 63.6 ± 9.8 63.7 ± 9.9
BMI (kg/m
)25.02 ± 3.66 25.17 ± 3.59 (.) 25.07 ± 3.53 (.)  26.64 ± 3.29 26.68 ± 3.34 (.) 26.74 ± 3.35 (.)
Waist-hip ratio  0.82 ± 0.05 0.82 ± 0.06 (.) 0.84 ± 0.06 (.)
 0.83 ± 0.05 0.84 ± 0.05 (.)
0.85 ± 0.03 (.)
MAP
a
(mmHg)  88.80 ± 6.63 87.74 ± 9.15 (.) 88.59 ± 9.16 (.)  88.94 ± 8.44 86.63 ± 7.58 (.)
86.85 ± 6.96 (.)
Glucose (mg/dL)  94.41 ± 12.10 94.84 ± 13.47 (.) 92.69 ± 10.66 (.)  91.50 ± 9.70 95.21 ± 10.62 (.)
91.21 ± 11.69 (.)
HbAc (%)  . [.–.] . [.–.] . [.–.]  . [.–.] . [.–.] . [.–.]
Cholesterol (mg/dL) 209.87 ± 31.81 199.77 ± 34.79 (.) 208.13 ± 37.11 (.)  205.32 ± 47.52 188.79 ± 42.14 (.)
194.04 ± 32.34 (.)
Triglycerides (mg/dL)  118.55 ± 50.73 110.90 ± 51.29 (.) 124.90 ± 74.12 (.) 93.68 ± 33.53 102.08 ± 35.40 (.) 103.16 ± 45.48 (.)
LDL (mg/dL)  140.40 ± 25.68 129.33 ± 25.51 (.)
138.30 ± 30.03 (.)  135.22 ± 38.55 116.63 ± 37.05 (.)
128.82 ± 26.20 (.)
HDL (mg/dL)  50.36 ± 10.24 48.42 ± 8.90 (.)
49.55 ± 9.20 (.) 52.07 ± 15.29 49.36 ± 13.69 (.)
49.14 ± 12.36 (.)
LDL/HDL  2.92 ± 0.83 2.76 ± 0.66 (.) 2.90 ± 0.81 (.)  2.84 ± 1.25 2.51 ± 0.85 (.) 2.75 ± 0.77 (.)
Ferritin (ng/dL)  44.03 ± 36.95 49.17 ± 36.75 (.) 50.55 ± 45.01 (.)  42.73 ± 42.05 40.04 ± 35.60 (.) 45.39 ± 41.97 (.)
Albumin (g/dL)  4.39 ± 0.26 4.35 ± 0.20 (.) 4.45 ± 0.32 (.) 4.38 ± 0.16 4.28 ± 0.19 (.)
4.32 ± 0.19 (.)
Serum creatinine (mg/dL)  . [.–.] . [.–.] . [.–.]
 . [.–.] . [.–.] . [.–.]
Urinary creatinine (mg/dL) 94.47 ± 53.48 111.63 ± 76.63 (.) 83.40 ± 61.43 (.)  95.35 ± 39.22 104.61 ± 57.90 (.) 82.74 ± 51.70 (.)
Urea (mg/dL)  11.47 ± 2.92 11.63 ± 3.72 (.) 10.84 ± 2.84 (.) 10.63 ± 2.78 10.07 ± 2.16 (.) 9.89 ± 2.19 (.)
eGFR
b
(mL/min per . m
) 77.70 ± 16.00 80.61 ± 12.26 (.) 82.59 ± 11.75 (.)
 82.42 ± 13.53 85.16 ± 13.64 (.) 89.93 ± 13.65 (.)
AST
c
(IU/L)  23.23 ± 4.92 23.39 ± 4.72 (.) 22.36 ± 4.62 (.)  21.78 ± 5.36 21.93 ± 4.98 (.) 22.56 ± 5.03 (.)
ALT
d
(IU/L)  18.00 ± 6.72 15.66 ± 3.69 (.)
16.21 ± 5.02 (.)
 17.39 ± 6.73 16.19 ± 4.67 (.) 16.27 ± 5.34 (.)
TAS
e
(mmol/L)  1.48 ± 0.11 1.66 ± 0.11 (.)
1.77 ± 0.09 (.)
 1.48 ± 0.11 1.60 ± 0.08 (.)
#
1.79 ± 0.15 (.)
Human sera HT (minutes)  160.0 ± 32.3 168.2 ± 32.3 (.)
165.7 ± 32.4 (.)
 160.1 ± 33.5 158.6 ± 26.1 (.) 159.7 ± 30.7 (.)
Parametric variables are expressed as mean ± standard deviation, whereas nonparametric variables are expressed as median [interquartile range]. Percentage change relative to baseline means are indicated in round
brackets.
Mean or median value is signicantly dierent from that of baseline (𝑃<0.1)(comparewithinrowandwithingroup).
Mean or median value is signicantly dierent from that of week  (𝑃<0.1)
(compare within row and between group).
a
Mean arterial pressure;
b
estimated glomerular ltration rate;
c
aminotransferase aspartate;
d
aminotransferase alanine;
e
total antioxidant status.
Page 7
BioMed Research International
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Mean calorie index/day (a.u.)
MaleMale
Female Female
Green tea Control
During 2-week washout period
During 14-week intervention period
F : Daily mean calorie index variation for participants under
green tea and water regimen during the -week intervention
period and -week washout period in a male and female Mauritian
population. Main and error bars represent mean values and standard
deviations, respectively, for experimental group (male, 𝑛=33;
female, 𝑛=32) and control group (male, 𝑛=30;female,𝑛=28).
MaleMale
Female Female
Green tea Control
During 2-week washout period
During 14-week intervention period
0
100
200
300
400
500
600
Lipid/fat ratio/day (a.u.)
F : Daily lipid/fat ratio for participants under green tea
and water regimen during the -week intervention period and -
week washout period in a male and female Mauritian population.
Main and error bars represent mean values and standard deviations,
respectively, for experimental group (male, 𝑛=33;female,𝑛=32)
and control group (male, 𝑛=30;female,𝑛=28).
, followed by a critical increase of .% (𝑃 < 0.1)(relative
to week  value) aer the washout period.
e ALT, a transaminase enzyme used to determine
liver health, decreased signicantly by .% (𝑃 < 0.1)as
illustrated by the female experimental group on week ,
whereas female control group did not show any signicant
change throughout the clinical trial. e time taken for
human sera to delay hemolysis by %, representing the
antioxidant potential of human sera at the cellular level,
increased signicantly by .% (𝑃 < 0.1)and.%(𝑃 < 0.1)in
male and female experimental groups, respectively, aer week
, whereas their corresponding control groups experienced
adecrease.
0
100
200
300
400
500
Control 0.25 0.50 1.00 1.50
Time taken for 50% hemolysis to occur
HT50 (minutes)
∗∗∗
∗∗∗
∗∗∗
Green tea extracts (mg/mL)
F : e prophylactic eect of green tea extracts against free
radical which might be a causative agent of metabolic syndrome.
Mainanderrorbarsrepresentmeanvalueandstandarddeviation
of three independent experiments, respectively. Statistical analyses
were performed, using independent samples 𝑡-test, for multiple
comparisons.
∗∗∗
Time taken for % hemolysis to occur was
signicantly dierent from that of control (𝑃 < 0.01).
4. Discussion
e current management of type diabetes involves a
combination of dietary plans, exercise programs, and the use
of drugs, such as sulfonylureas and biguanide []. Besides
these conventional therapies, a growing body of evidence
has indicated the role of green tea polyphenols in improving
features of metabolic syndrome and subsequent risks for
diabetes and its complications [, ]. e putative benecial
eects ascribed to green tea polyphenols are partly mediated
by their free radical scavenging, antioxidant action, and abil-
ity to form complexes with metal ions. e green tea analysed
in this study had high levels of total phenols, avonoids, and
proanthocyanidins with a wide range individual compounds
that synergistically contributed to the antioxidative propen-
sity of the extract as evidenced by the multiantioxidant anal-
ysis data including the free radical-induced hemolysis assay
data (Figure ).Similarobservationsweremadeinanearlier
report where green and black teas were characterised for their
antioxidant functions []. e green tea supplementation in
this study led to a signicant increase in serum antioxidant
capacity as measured by the free radical-induced hemolysis
assay. is suggests that the oxidative stress condition that
can be encountered in diabetes [, ]couldbenetfrom
greenteaconsumption.RazaandJohn[]havereported
that tea catechins can prevent protein degradation by altering
subcellular reactive oxygen species production, glutathione
metabolism, and cytochrome P E activity. Grinberg
et al. [] found that tea polyphenols protect red blood cells
against primaquine-induced lysis and H
2
O
2
-induced lipid
peroxidation. While it can be further derived from the data
in this study that green tea consumption can reinforce in
vivo antioxidant defences, the potential prophylactic eects
of green tea against diabetes and its complications remain to
be clearly dened. In the study, the eect of cigarette smoking,
excessive alcohol intake, and hormone replacement therapy,
on levels of biomarkers measured, were minimised by the
exclusion criteria applied to the subject population. Dietary
Page 8
BioMed Research International
survey questionnaires indicated that daily mean calorie index
and daily lipid/fat ratio of the population diet did not change
signicantly during the -week period. e subjects also
were not on any medication against diabetes, cardiovascular
diseases, or hypertension. us, it is not plausible at this stage
to suggest whether the eects of green tea regimen could be
translated to other dietary factors and medication.
Anthropometric data suggest that green tea regimen for
a -week intervention period suppressed the signicant
elevation of waist-hip ratio in the female experimental group.
It is of interest to note that in a randomized, double-blind,
placebo-controlled clinical trial obese women supplemented
with green tea for a -week intervention period experienced
a marked reduction in waist and hip circumference [].
e mechanism by which tea or its bioactive components
might decrease abdominal obesity may occur at dierent
levels.Inthedigestivetract,greenteacatechinsappearto
form complexes with lipids and lipolytic enzymes, thereby
interfering with the luminal processes of emulsication,
hydrolysis, micellar solubilisation, and subsequent uptake of
lipids []. An increase in -hour energy expenditure and
fat oxidation in humans has also been attributed to green tea
consumption [].
e consumption of green tea times a day suppressed
mean arterial pressure from a signicant decrease aer week
, indicating that green tea may promote a good blood
ow all around the body and as a consequence prevents
ischemic reperfusion injury of end organs. Potenza et al.
[] investigated the metabolic eects of epigallocatechin--
gallate (EGCG) in spontaneously hypertensive rats. EGCG
( mg/kg for weeks) signicantly reduced systolic blood
pressure and enhanced both endothelial function and insulin
sensitivity. It has also been shown that epicatechin derivatives
from green tea leaves can relax rat mesenteric arteries,
probably by inhibiting Ca
2+
inux and increasing nitric oxide
release which has a vasodilatory eect [, ].
Green tea consumption during the -week period of
study did not aect fasting plasma glucose (measured using
the glucose oxidase method), nor was the level of the
HAc impacted. e green tea regimen however prevented
impaired fasting glucose from a signicant increase as com-
pared to the control group. ese ndings show the potential
role of green tea as a glycemic regulator. e subjects involved
in this study are prediabetic who have the potential risk
for developing diabetes. Li et al. []postulatedthatgreen
tea catechins might ameliorate insulin resistance by acting
as peroxisome proliferator-activated receptor ligands with a
dual alpha/gamma agonistic eect. Green tea phytochemicals
arealsoreportedtopreventintestinalglucoseuptakeby
inhibiting the sodium-dependent glucose transporter of rab-
bitintestinalepithelialcells[]. Many other interventional
clinical trials have also illustrated the benecial eect of green
tea against diabetes [].
Ferritin, a ubiquitous intracellular protein, stores iron and
releases it in a controlled fashion. e amount of ferritin
usually reects the amount of iron in vivo.Iron,aredoxactive
transition metal ion, is important for the normal functioning
of the human body. However, at high level free ferrous
ions react with peroxides to produce hydroxyl radicals,
via the Fenton reaction. e formed hydroxyl radicals are
highly reactive and can damage cellular components such
as proteins, DNA, and lipids. At week  of the green tea
regimen, the ferritin of male experimental group slightly
reduced whereas the ferritin of male control group increased
considerably by .% (𝑃<0.1). A plausible explanation
forourresultsisthatiron-phenolchelatesmightformin
the lumen during digestion resulting in lower iron absorp-
tion []. Interestingly, Kim et al. [] also showed that
epigallocatechin--gallate inhibit nonheme iron absorption
by reducing basolateral iron exit, possibly through formation
of a nontransportable polyphenol-iron complex.
Daily consumption of green tea has been oen associated
with a lifestyle which may support healthiness and longevity.
However, the hepatotoxicity of green tea has been put into
question and led to the recent publication of a systematic
review of the safety of green tea extracts by the United
States Pharmacopeia []. In our study, the consumption
of green tea three times a day before meals did not show
any hepatotoxic eect. Consistent with this outcome is
the interventional studies involving supplementation with
mggreenteapolyphenoldailytohealthymenfor
weeks and supplementation of  mg green tea polyphenol
daily to postmenopausal osteopenic women for  weeks not
causing any adverse eects on liver and kidney function, as
determined by blood test parameters [, ].
Chronic kidney disease is recognized public health prob-
lem and eGFR has been considered to be a good indicator
to evaluate renal function. Most clinicians claimed that it
is dicult to estimate glomerular ltration rate, only from
serum creatinine concentration, as its accuracy is aected by
other factors []. To circumvent these limitations, several
formulas have been designed to estimate glomerular ltration
rate not only from serum creatinine concentration but also
from age, body size, gender, serum albumin concentration,
and serum urea concentration []. e -variable MDRD
equation has been used. eGFR of male experimental group
decreased signicantly on week , and aer discontinuing
the green tea regimen for a -week washout period, a critical
increase of .% (relative to week  value) in eGFR was
noticed. Current guidelines dene chronic kidney disease as
a glomerular ltration rate less than  mL/min per . m
2
for months or more [, ]. On the contrary, the ndings in
this study showed that the green tea regimen decreased eGFR
to a concentration which was still greater than the cuto point
associated with kidney damage. e clinical trial also showed
that the green tea regimen is not associated with any side
eects or toxicity at the recommended level of intake and
revealed prophylactic eects such as antiobesity. Relative to
water regimen, the green tea regimen prevents waist-hip ratio
of subjects from a signicant increase during the intervention
period. It signicantly increases the antioxidant capacity of
serum.
In conclusion, the clinical trial is acknowledgeable to
certain limitations. It was not possible for all subjects to
maintain their normal diet. eir cooking mode and the
amount of food consumed by each subject were not known.
In the future, a more detailed dietary survey questionnaire
should be used to ensure that the prescribed regimen is
Page 9
 BioMed Research International
being properly followed. e protocol for using cups of
greenteawasinitiallybasedonthetotalphenoliccontent
corresponding to  mg gallic acid equivalent/cup, thus
bringing the ingestion to  mg of total phenols/day. is
was consistent with the literature data [, ]andour
previous studies using black tea [, ]whichhaveshown
signicant changes in cardiovascular disease clinical param-
eters with  mg of total phenols/day. In the light of the
data obtained in this study, a greater intervention period
andaconsumptionofmorethancupsperdaycould
eventually be envisaged for a more signicant modulation of
the clinical markers. Nonetheless, more in-depth research is
warranted to corroborate these potential benets in a large
multinational cohort []. e green tea regimen could form
part of a healthy lifestyle that might ameliorate features of
metabolic syndrome and subsequent risks for individuals
with the potential propensity to develop type diabetes. e
mechanisms accounting for the benecial healthy eects of
green tea merit further exploration at the molecular level.
Conflict of Interests
All authors read and approved the nal paper. None of the
authors had any conict of interests.
Acknowledgments
is work was supported by grants from the Universit
´
ede
la R
´
eunion, La R
´
eunion, France (Conseil R
´
egional de La
R
´
eunion et l’Europe); University of Mauritius, Mauritius; Ter-
tiary Education Commission, Mauritius; Mauritius Research
Council, Mauritius; Soci
´
et
´
eUsini
`
ere de St Aubin, Mauritius;
and the Conseil R
´
egional de la R
´
eunion et l’Europe. e
logistics were supported by the Apollo Bramwell Hospital,
Mauritius; Biosant
´
e Ltd., Mauritius; Soci
´
et
´
eUsini
`
ere de St
Aubin, Mauritius, and the Cardiac Centre of the Sir See-
woosagur Ramgoolam National Hospital, Pamplemousses,
Mauritius. Naushad Ali Toolsee was awarded a postgraduate
research scholarship by the Tertiary Education Commission
of Mauritius. is study was conducted under the National
Research Chair program (eeshan Bahorun).
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  • Source
    • "Green tea extract (GTE) has been extensively studied as herbal remedy due to antioxidation [1] [2], antihypertension [3], antimutagenicity [4], anticarcinogenesis [5] and enhancing glucose tolerance [6] effects to protect against cardiovascular diseases [7], ultraviolet attack [8], oral diseases [9] and obesity [10]. These effects are mainly attributed to the multiple target properties of GTE in signaling and regulatory pathways. "
    [Show abstract] [Hide abstract] ABSTRACT: Green tea extract (GTE) exerts antioxidative activities in ocular tissues of rats, but high levels of (-)-epigallocatechin gallate (EGCG) can induce oxidative stress. In this study, pharmacokinetics, diurnal variation of oxidative status, antioxidation and transcription factors changes in ocular tissues of rats were investigated. Rats were fed intragastrically with GTE and catechin mixtures containing different amounts of EGCG. Plasma and various ocular tissues were taken for pharmacokinetic analysis, oxidation marker testings and gene expression assays. Effects of EGCG on ocular oxidation status were assessed by 8-isoprostane level and reduced/oxidized glutathione ratio. Oxidation, inflammation and apoptosis regulations in retina were evaluated by real-time polymerase chain reaction. Epicatechin, epigallocatechin and EGCG were dominant in various ocular tissues except vitreous humor, where gallocatechin was predominant. Diurnal variation of oxidative status was found in some compartments. GTE caused oxidative stress increase in the plasma, aqueous humor, vitreous humor, cornea and retina but decrease in the lens and choroid-sclera. Catechins mixture containing half dose of EGCG lowered 8-isoprostane in the retina and lens. GTE treatment induced superoxide dismutase 1 and glutathione peroxidase-3 expressions but suppressed catalase in the retina. Our results reveal pro-oxidation of GTE with high EGCG content to the ocular tissues. Optimal EGCG level is needed for protection.
    Full-text · Article · Sep 2015 · The Journal of nutritional biochemistry
  • Source
    • "And so forth, relate the change in HbA1c concentration to an increase in polyphenols intake. In this case, only 7 (Balzer et al., 2008; Curtis et al., 2012; Fenercioglu et al., 2010; Kudolo et al., 2005; Pan et al., 2007; Toolsee et al., 2013; Vinson et al., 2012) of the trial included in the meta-analysis included polyphenol metabolites analysis or antioxidant capacity assay. A dose-response effect between polyphenol and HbA1c was not included in the meta-analysis given the variability of trials. "
    [Show abstract] [Hide abstract] ABSTRACT: Polyphenols have been extensively studied for their antioxidant and anti-inflammatory properties. Recently, their antiglycative actions by oxidative stress modulation have been linked to prevention of diabetes and associated complications. This paper assesses the evidence for polyphenol interventions on glycohaemoglobin (HbA1c) in non-diabetic, pre-diabetic and type 2 diabetes mellitus (T2DM) subjects. A systematic review of polyphenols clinical trials on HbA1c in humans was performed according to the Preferred Reporting Items for Systematic Review and Meta-Analysis. Thirty-six controlled randomized trials with HbA1c values were included. Polyphenols (extracts, supplements, foods), were supplemented (28 mg to 1.5g) for 0.7 to 12 months. Combining all subjects (n=1954, mean baseline HbA1c=7.03%, 53 mmol/mol), polyphenol supplementation significantly (p<0.001) lowered HbA1c% by -0.53±0.12 units (-5.79±0.13 mmol/mol). This reduction was significant (p<0.001) in T2DM subjects, specifically (n=1426, mean baseline HbA1c=7.44%, 58 mmol/mol), with HbA1c% lowered by -0.21±0.04 units (-2.29±0.4 mmol/mol). Polyphenol supplementation had no significant effect (p>0.21) in the non-diabetic (n=258, mean baseline HbA1c=5.47%, 36 mmol/mol) and the pre-diabetic subjects (n=270, mean baseline HbA1c=6.06%, 43 mmol/mol) strata: -0.39±0.27 HbA1c% units (-4.3±0.3 mmol/mol), and -0.38±0.31 units (-4.2±0.31 mmol/mol), respectively. In conclusion, polyphenols can successfully reduce HbA1c in T2DM, without any intervention at glycaemia, and could contribute to the prevention of diabetes complications.
    Full-text · Article · Mar 2015 · Proceedings of The Nutrition Society
  • Source
    • "Catechins are abundant in less-fermented teas (Henning et al. 2003; Murakami et al. 2006; Myers et al. 2013). It is believed that most of the health benefits, including antioxidant, anti-inflammatory, antiproliferative, antimutagenic, antibacterial and antiviral properties as well as protection against cardiovascular disease, hyperglycaemia , metabolic disorders and some cancers (Dufresne & Farnworth 2001; Gupta et al. 2002; Luczaj & Skrzydlewska 2005; Cabrera et al. 2006; Anandh Babu et al. 2008; Kuriyama 2008; Venables et al. 2008; Butt & Sultan 2009; Meltzer et al. 2009; Schramm 2013; Toolsee et al. 2013; Uchiyama et al. 2013) are due to EGCG. Tea may also reduce the risk of osteoporotic fractures among elderly people (Shen et al. 2013). "
    [Show abstract] [Hide abstract] ABSTRACT: Consumers are very aware of contaminants that could pose potential health hazards. Most people drink tea as an infusion (adding hot water); however, in some countries, including India, China, and Egypt tea is drunk as a decoction (tea and water are boiled together). An infusion usually brings the soluble ingredients into solution; whereas a decoction brings all soluble and non-soluble constituents together. Therefore, a cup of tea may contain various kinds of contaminants. In this review, we focus on green and black tea, because they are most commonly consumed. Our target was to examine the transfer rate of contaminants (pesticides, environmental pollutants, mycotoxins, microorganisms, toxic heavy metals, radioactive isotopes (radionuclides), and plant growth regulators) from tea to infusion/brewing, factors contributing to the transfer potential and contaminants degradation, and residues in or on the spent leaves. We concluded that most contaminants leaching into tea infusion are not detected or are detected at a level lower than the regulatory limits.However, the traditional practice of over-boiling tea leaves should be discouraged, as there may be a chance for more transfer of contaminants from the tea to the brew.
    Full-text · Article · Aug 2014 · Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment
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