Piero Marchetti University of Pisa Effects of gliclazide on oxidative stress in the pancreatic...

transcript

Piero MarchettiUniversity of Pisa

Effects of gliclazide on oxidative stress

in the pancreatic beta-cell

Defining T2DM

…varying degrees of insulin resistance and insulin secretory deficiency

Defining T2DM

…varying degrees of insulin resistance and insulin secretory deficiency

The natural history of T2DM

T2DM: the fundamental factor is…

…the beta-cell!

To be discussed

• The beta-cell in normal conditions and in type 2 diabetes

• The importance of oxidative stress induced beta-cell damage

• The role of gliclazide

To be discussed

~ 3,000 cells75% Beta cells25% non-Beta cells

200 µm

Micrograph: Lelio Orci, Geneva

Islet of Langerhans

Presented by Pr Philippe Halbanat the 1st Amsterdam Diabetes Meeting, March 30-April 1, 2006

10 µm~ 10,000granules

Micrograph: Lelio Orci, Geneva

The normal beta-cell

Presented by Pr Philippe Halbanat the 1st Amsterdam Diabetes Meeting, March 30-April 1, 2006

• Half-life of ~30 days

• Apoptosis is the major mechanism of death

normal

normalapoptotic

• New beta-cells by– replication– neogenesis

Butler P et al, Diabetes 2003

Del Guerra S et al, Diabetes 2005

The beta-cell in T2DM

Summary1

• Compared to the normal situation, in T2DM there is:– decreased beta-cell mass – reduced insulin secretion function (in particular

in response to glucose)

To be discussed

Beta-cell oxidative stress in human T2DM beta-cells

8-OHdG immunostaining

Beta-cell oxidative stress in human T2DM beta-cells

Mn-SOD Cu/Zn-SOD

Controls

gene expression

Marchetti P et al, JCEM 2004

Glucose Toxicity

Robertson RP, JBC 2004

Summary2

• In T2DM, there is increased oxidative stress at the beta-cell level, which contributes to:– mass reduction – insulin secretion defects

normal

Genetic factors

Acquired factors(glucotoxicity, lipotoxicity,IAAP, others)

normal

Genetic factors

normal

Type 2 diabetes

Genetic factors

normal

Type 2 diabetes

WHAT’S THE ROLE OFSULPHONYLUREAS?

To be discussed

The role of sulphonylureas

• Some studies have reported increased sulphonylurea-induced beta-cell apoptosis in-vitro

The role of sulphonylureas

• Some studies have reported increased sulphonylurea-induced beta-cell apoptosis in-vitro

Maedler K et al, JCEM 2005

ctrl nategl glibencl

The role of gliclazide

Diabetes Metab Res Rev 2007

• Human islets were prepared by collagenase digestion and density gradient purification

number age (yrs) gender BMI (Kg/m2)

16 57.9 ± 5.7

24.6 ±

Collagenase digestionCollagenase digestion

Density gradient Density gradient purificationpurification

Preparation of isolated human islets

• Culture for 5 days in: – continuous normal glucose medium (NG, 5.5

mM) or high (HG, 16.7 mM) and normal glucose media, alternating every 24h

– with or without 10 µmol/l glibenclamide (GLIB) or 1/10 µmol/l gliclazide (GLICL)

• Assessment of:– acute glucose-stimulated insulin secretion– beta-cell apoptosis and mitochondrial

morphology (electron microscopy)– gene expression– protein expression– oxidative stress (nitrotyrosine concentration)

NG+GLIB

NG+GLICL

Stimulation index (% of controls)

NG+GLIB

NG+GLICL

HG/NG+GLIB

HG/NG+GLICL

Stimulation index (% of controls)

* * **

apoptosis

HG/NG+GLIB

HG/NG+GLICL

Beta-cell apoptosis (%)

The role of gliclazide(antioxidant properties)

• Scott NA et al, Eur J Pharmacol 1991• Noda Y et al, Res Commun Mol Pathol Pharmacol

1997• Jennings PE and Belch JJ, Metabolism 2000• Renier G et al, J Diabetes Complications 2000• Fava D et al, Diabet Med 2002• Onozato ML et al, Kidney Int 2004• Alper G et al, Endocr Res 2005• Li L and Renier G, Metabolism 2006

The role of gliclazide(antioxidant properties)

nitrotyrosine

HG/NG+GLIB

HG/NG+GLICL

Nitrotyrosine (ng/ml)

The role of gliclazideCtrl H2O2

H2O2+GLIBH2O2+GLICL

0102030405060708090

100 150 200

gliclazide 1

gliclazide 5

glibenclamide 1

glibenclamide 5

% viability

H2O2 (µmol/l)

Summary3

• Gliclazide has several beneficial effects on beta-cells, including:– better survival– improved function

Conclusions

• The pancreatic beta-cell is central to the development and progression of diabetes

• Several factors and mechanisms contribute to beta-cell damage in T2DM, including increased oxidative stress

• Gliclazide has protective effects on the beta-cell, due, at least in part, to its antioxidant properties

• Additional long term, prospective studies in patients are needed to confirm the in-vitro data

Piero MarchettiUniversity of Pisa

Effects of gliclazide on oxidative stress

in the pancreatic beta-cell

Piero Marchetti University of Pisa Effects of gliclazide on oxidative stress in the pancreatic...

Documents