Poor glycaemic control in type 2 diabetes patients reduces endothelial progenitor cell number by influencing SIRT1 signalling via platelet-activating factor receptor activation.
OBJECTIVE
Downregulation of levels of endothelial progenitor cells (EPCs) during in-vitro short-term exposure to high glucose concentrations relates to reduced activity of silent information regulator 1 (SIRT1) and increased synthesis of platelet-activating factor (PAF). We investigated the possible relationship between PAF and SIRT1 pathways in EPCs during altered glucose homeostasis.


METHODS
SIRT1 and PAF receptor (PAF-R) levels were determined by western blot, RT-PCR and confocal laser-scanning microscopy. In-vivo experiments were performed on 48 type 2 diabetic patients (25 with poor glycaemic control and 23 with good glycaemic control) and 20 control individuals. In-vitro experiments with the PAF-R antagonist CV3988 were performed on EPCs isolated from leucocyte-rich buffy coat of healthy human donors.


RESULTS
Decreased SIRT1 protein levels were observed in EPCs from type 2 diabetic patients compared with control individuals (p < 0.01). Notably, the SIRT1 level was consistently lower in patients with poor glycaemic control than in those with good glycaemic control (p < 0.01). Diabetic patients also showed an upregulation of PAF-Rs; this response occurred to a greater extent in individuals with poor glycaemic control than in those with good glycaemic control. In-vitro experiments confirmed that EPCs respond to PAF stimulation with decreased SIRT1 protein and SIRT1 mRNA levels. Moreover, reduction of SIRT1 levels and activity were abolished by CV3988.


CONCLUSIONS
These findings unveil a link between PAF and SIRT1 pathways in EPCs that contributes to the deleterious effect of hyperglycaemia on the functional properties of EPCs, crucial in diabetes and peripheral vascular complications.
Department of Biochemistry, Biophysics and General Pathology, Second University of Naples, Via L. de Crecchio 7, Naples 80138, Italy. marialuisa.balestrieri@unina2.it
M L
ML
Balestrieri
L
L
Servillo
A
A
Esposito
N
N
D'Onofrio
A
A
Giovane
R
R
Casale
M
M
Barbieri
P
P
Paolisso
M R
MR
Rizzo
G
G
Paolisso
R
R
Marfella
D000328:Adult; D053687:Adult Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D000368:Aged; D058621:Blood Buffy Coat / Q000473:pathology; D002452:Cell Count; D002469:Cell Separation; D002478:Cells, Cultured; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D003925:Diabetic Angiopathies / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D015536:Down-Regulation / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D006943:Hyperglycemia / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D010742:Phospholipid Ethers / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D010980:Platelet Membrane Glycoproteins / Q000819:agonists* / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D056564:Sirtuin 1 / Q000235:genetics / Q000378:metabolism*
D010742:Phospholipid Ethers; D010975:Platelet Aggregation Inhibitors; D010980:Platelet Membrane Glycoproteins; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; C037913:CV 3988; C447939:SIRT1 protein, human; D056564:Sirtuin 1