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