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The anti-diabetic potential of black and green teas
Piteesha Ramlagan, Philippe Rondeau, Cynthia Planesse, Vidushi Neergheen-Bhujun, Emmanuel Bourdon and Theeshan Bahorun
Introduction: Tea
Camellia sinensis
Green tea
Black tea
TEA Antioxidant
Anti-inflammatory
Anti-diabetic
Anti-obesity
Anti-atherogenic Neuroprotective
No fermentation
Fermentation
Introduction: Diabetes Statistics
Estimated number of people with diabetes worldwide (IDF Diabetes Atlas, 2015)
Introduction: Diabetes Statistics
Diabetes estimates (20-79 years)
Mauritius Reunion Madagascar Comoros
Prevalence, % 22.3 15.8 4.0 9.9
% of diabetic population
18.3 13.0 1.5 3.6
Diabetes related deaths
2931.2 NA 5580.2 318.7
Mean diabetes related expenditure (USD), per person
934.3 NA 111.4
152.2
Introduction: Post-prandial hyperglycemia
α-amylase
α-glucosidase
Glucose
Oligosaccharides
Starch
Post-prandial hyperglycemia
Introduction: Glycation
α-amylase
α-glucosidase
Glucose
Oligosaccharides
Starch
Glucose Proteins
Schiff base Amadori product
Advanced Glycation End products (AGEs)
Introduction: AGEs & diabetic complications
AGE receptor
AGE
Target genes transcription
Vascular adhesion molecules
Oxidative stress
ROS
Diabetic complications
Pro-inflammatory cytokines
Our focus
α-amylase
α-glucosidase
Glucose Starch
Proteins
Schiff base Amadori product
AGEs AGE receptor
AGE
Oxidative stress
ROS
Inflammation
Biochemical, antioxidant & carbohydrate hydrolysing inhibition screening
Biochemical screening
Carbohydrate hydrolysing enzymes
inhibitory assays
Phenolic, Flavonoid, Proanthocyanidin
α-amylase α-glucosidase
Antioxidant evaluation
FRAP, ORAC, Iron (II) chelating, superoxide,
nitric oxide, H2O2, ABTS, DPPH scavenging
Rich in polyphenols
Tea TPC mg GAE per g
TFC mg CE per g
TPrC mg (CEE) per g
Black tea 99.83 ± 1.51b 23.42 ± 0.81b 2.03 ± 0.09b
Green tea 179.47 ± 8.55a 43.50 ± 0.81a 7.14 ± 0.28a
High antioxidant capacity
Black tea Green tea
0
1
2
3
4
5
mmol fe2+/g DM
mmol trolox/g DM
a
b
a
b
mm
ol/g
DM
In vitro scavenging of IC50 (µg LP/mL)
Black tea Green tea
ABTS·+ 20.35 ± 0.30b 12.18 ± 0.65a
DPPH· 36.07 ± 1.93b 19.94 ± 0.24a
H2O2 700.99 ±15.25b 477.92 ±20.47a
NO· 19.32 ± 0.91b 8.42 ± 0.44a
O2·- 31.62 ± 0.75b 18.29 ± 0.59a
In vitro chelating of Fe2+ 133.90 ± 2.37a 253.97 ± 10.14b
Tea inhibits α-amylase and α-glucosidase activity
Sample IC50 (µg LP/mL)
α-amylase α-glucosidase
Black tea 589.86 ± 39.51b 72.31 ± 4.23a
Green tea 947.80 ± 18.20c 100.23 ± 8.10b
Acarbose 1.78 ± 0.08a 162.07 ± 4.66c
Starch Side effects
Bacterial fermentation
α-amylase
Oligosaccharides
α-glucosidase
Glucose
acarbose
Anti-glycative activity of tea
BSA
Glucose/ ribose/
Methylglyoxal (MGO)
Tea/ aminoguanidine
Glycation products
Incubation at 37 °C for 15 days
Fluorescent AGEs Fructosamine
Tea as an anti-glycating agent
Protective effect of tea against oxidative stress & inflammation
Pretreatment with tea for 24h
3T3-L1 preadipocytes: mimicking diabetes-like oxidative stress
BSAMGO H2O2
(Castan-laurell et al., 2012)
BSARIB BSA
Tea reduces ROS production
24 h stress oxidant treatment
Control BSAG0 BSAMGO BSARIB H2O2
50
75
100
125
Control Black Tea Green Tea
# # #
# # #
*
***
# #
# # #
# #
# #***
# #
# # #
RO
S p
rod
ucti
on
(% a
s c
om
pa
red
to
un
tre
ate
d c
ell
s)
Tea suppresses oxidative modification of proteins
a b
Control BSAG0 BSAMGO BSARIB H2O2
50
75
100
125
Control Black Tea Green Tea
# #
# #
*
#
#
# #
# ## #
# #
**
Pro
tein
Ca
rbo
ny
l L
ev
el
(% a
s c
om
pa
red
to
co
ntr
ol)
Control BSAG0 BSAMGO BSARIB H2O2
0
5
10
15
20
25
Control Black Tea Green Tea
# # #
# # #
***
*
# #
#
#
#
*
#
#
AO
PP
le
ve
l
(nm
ol
ch
lora
min
e-T
eq
uiv
ale
nt
/
mg
to
tal
pro
tein
s)
Tea reduces oxidative modification of proteins
a b
80 90 100 110 120 13080
90
100
110
120
130
r = 0.70p<0.0001
ROS level
Pro
tein
carb
on
yl le
vel
80 90 100 110 120 1300.00
0.05
0.10
0.15
0.20
0.25
r = 0.69p<0.0001
ROS level
AO
PP
level
Tea inhibits reduction of intrinsic antioxidant enzymatic activity a
b
c
Control BSAG0 BSAMGO BSARIB H2O2
0
5
10
15
20
25
Control Black Tea Green Tea
**
*
***
***
*
# # #
# # #
# #
# #
#
SO
D a
cti
vit
y
(U/m
g t
ota
l p
rote
in)
Control BSAG0 BSAMGO BSARIB H2O2
0
10
20
30
40
50
Control Black Tea Green Tea
***
***
*** # # #
#
#
# #
#
# #
#
CA
T a
cti
vit
y
(U/m
g t
ota
l p
rote
in)
Control BSAG0 BSAMGO BSARIB H2O2
0
50
100
150
***
***
*
# # #
# # #
#
#
Control Black Tea Green Tea
# #
#
GP
x a
cti
vit
y
(%/m
g t
ota
l p
rote
in)
c
Tea exerts anti-inflammatory role
Control BSAG0 BSAMGO BSARIB H2O2
0
10
20
30
100
120
140
160
Control Black Tea Green Tea
# # #
# # #
***
***
******# #
# #
# # #
# # #
***
# # #
# # #
IL-6
Se
cre
tio
n (
pg
/mL
)
Conclusion
AGEs
ROS
Modified proteins
Transcription
IL-6
Inhibit
Decrease activities of SOD, CAT and GPx
α-amylase
α-glucosidase Glucose Proteins
Black tea Green tea
Starch
Intermediate products
Nucleus Trigger
Black tea Green tea
Black tea Green tea
Ribose/MGO
Acknowledgement
Dr Philippe Rondeau
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