Objective: To investigate the number and function of circulating endothelial progenitor cell (EPC) in different vascular complications of type 2 diabetes (T2DM) and its associations with vascular endothelial function.
Methods: A total of 415 T2DM patients were recruited from the outpatients and inpatients of the Endocrinology Department at Union Hospital. Assessments of cardiovascular disease and cerebrovascular disease were based on each patient's medical records. Peripheral vascular disease was diagnosed by bilateral ultrasonography bilaterally. Non-mydriatic fundus camera screening was used as a tool to identify diabetic retinopathy. Urinary albumin exceeding 30 mg/24 h occurring twice over a period of six months was diagnosed as diabetic nephropathy. Circulating EPC was quantified by flow cytometry. Colony forming count (CFU) and migration assay were used for evaluating the function of circulating EPC. Vascular endothelial function was assessed by flow-mediated brachial artery dilatation (FMD).
Results: There were four groups in the study: T2DM without vascular disease (TC, n = 97), T2DM with macrovascular disease (TA, n = 106), T2DM with microvascular disease (TI, n = 100), T2DM with macro- and micro-vascular diseases (TAI, n = 112). The sequence of circulating EPC number and CFU in four groups was TA < TAI < TI < TC (532 +/- 90, 616 +/- 93, 768 +/- 97 and 1045 +/- 106 cell/ml; 21 +/- 4, 28 +/- 5, 43 +/- 7 and 70 +/- 9 unit/chamber) and there was a significant difference between any two groups (P < 0.05). The results of migration were consistent with circulating EPC number (125 +/- 12; 90 +/- 9 cell/HP field) except there were no significant differences in TA and TAI groups (24 +/- 6; 28 +/- 7 cell/HP field). Age, HbA1c, SBP, BMI and duration of T2DM were the independent risk factors of circulating EPC number in T2DM patients with macrovascular disease (P < 0.05). Age, HbA1c and duration of T2DM were the independent risk factors of circulating EPC number in T2DM patients with microvascular disease (P < 0.05). After the adjustment of traditional risk factors, the number of circulating EPC had a close correlation with FMD (standardized coefficient, t = 0.61, P = 0.01).
Conclusion: The number and function of circulating EPC decreased with different degrees in T2DM patients of different vascular diseases. Circulating EPC number was associated with endothelial function and can be considered as a surrogate biological marker of vascular endothelial function for T2DM.