Abstract:

BACKGROUND: Studies have demonstrated that intermittent high glucose can have a more severe impact on vascular endothelial function in comparison with persistent hyperglycemia.
OBJECTIVE: To investigate the effect of intermittent high glucose on the proliferation and apoptosis of endothelial progenitor cells (EPCs) from human peripheral blood in vitro as well as the production of malondialdehyde (MDA) and antioxidant.
METHODS: Total mononuclear cells were isolated from human peripheral blood by Ficoll density gradient centrifugation and then the cells were placed on fibronectin-coated culture dishes. After 7 days of culture, the adherent cells were identified as EPCs by laser scanning confocal microscope. The cells were synchronized and then stimulated with glucose 5.5 mmol/L (normal control group), 20 mmol/L (constant high glucose group), and 5.5/20 mmol/L (intermittent high glucose group, 5.5 and 20 mmol/L glucose culture solution was changed every 8 hours) for 72 hours. EPCs proliferation and apoptosis was measured by MTT assay and flow cytometry, respectively. The content of MDA and the activity of superoxide dismutase (SOD) in culture solution were detected with colorimetry.
RESULTS AND CONCLUSION: After EPCs were exposed to constant high glucose (20 mmol/L) and intermittent high glucose (5.5/20 mmol/L) for 72 hours, proliferated cells were significantly reduced and the apoptosis rate was significantly increased compared with those exposed to normal glucose (P < 0.01). Furthermore, there was a significant increase in MDA contents as well as a significant reduce in SOD activities in the constant high glucose and intermittent high glucose group (P < 0.01), especially in the latter group. These findings indicated that both intermittent high glucose and constant glucose could inhibit the proliferation and promote the apoptosis of EPCs; however, intermittent high glucose appears to worsen the effects on EPCs. This is maybe due to the increased oxidative stress.