Advanced glycation end products in diabetic patients with optimized glycaemic control and their effects on endothelial reactivity: possible implications in venous graft failure.
BACKGROUND
Diabetic patients exhibit an increased risk of saphenous graft occlusion after coronary bypass. Advanced glycation end products (AGEs) are ubiquitous signalling proteins that are associated with vascular and neurological complication of diabetes. The aim of this study is to verify whether AGE levels may promote endothelial cell alterations responsible for vein graft failure.


METHODS
Segments of saphenous vein were obtained from both normal people and diabetic patients (HbA(1c) < 6.0%) at the time of coronary surgery. Cultured endothelial cells were incubated in the absence/presence of AGEs (2 and 20 microM), and mRNA and protein for both receptor of AGEs (RAGE) and peroxisome proliferator-activated receptors-gamma (PPAR-gamma) were analysed by real-time polymerised chain reaction (PCR) and Western blot analysis. In the same fashion, the cell release of reactive oxygen species (ROS) was estimated in the absence/presence of AGEs by spectrofluorimetric analysis. Finally, neutrophil-endothelial adhesion was evaluated in saphenous vein segments with and without the addition of AGEs.


RESULTS
AGEs activated in a dose-dependent manner the expression of RAGE and inhibited PPAR-gamma expression in endothelial cells as testified by both reverse transcription-PCR (RT-PCR) and Western blot analysis. Stimulation of cultured endothelial cells with AGEs significantly enhanced intracellular ROS formation in a dose-dependent manner. Finally, neutrophil-endothelial adhesion was significantly increased after incubation of control veins with AGEs.


CONCLUSIONS
These findings indicate that even in diabetic patients with HbA(1c) < 6.0%, elevated serum levels of AGE determine a sort of a pro-thrombotic state, providing a common mechanism that could explain the increased rate of vein graft occlusion in this population.
Chello
Massimo
M
Department of Cardiovascular Sciences, University Campus Bio Medico of Rome, Rome, Italy. m.chello@unicampus.it
Spadaccio
Cristiano
C
Lusini
Mario
M
Covino
Elvio
E
Blarzino
Carla
C
De Marco
Federico
F
Di Domenico
Fabio
F
Coccia
Raffaella
R
D001786:Blood Glucose / Q000378:metabolism; D016022:Case-Control Studies; D002448:Cell Adhesion / Q000502:physiology; D002478:Cells, Cultured; D003324:Coronary Artery Disease / Q000097:blood / Q000150:complications / Q000601:surgery; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000150:complications; D003925:Diabetic Angiopathies / Q000097:blood / Q000150:complications / Q000601:surgery; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D017127:Glycation End Products, Advanced / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood; D006085:Graft Survival; D006801:Humans; D009504:Neutrophils; D047495:PPAR gamma / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D017382:Reactive Oxygen Species / Q000378:metabolism; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000187:drug effects*; D012016:Reference Values; D012501:Saphenous Vein / Q000166:cytology / Q000637:transplantation
D001786:Blood Glucose; D017127:Glycation End Products, Advanced; D047495:PPAR gamma; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic