Patients with an HbA1c in the prediabetic and diabetic range have higher numbers of circulating cells with osteogenic and endothelial progenitor cell markers

Abstract

Context: Vascular calcification, an important feature of diabetic vasculopathy, is an active process potentially mediated by endothelial progenitor cells (EPCs) coexpressing the osteoblastic marker osteocalcin (OCN).

Objective: In this study we tested the hypothesis that cells expressing these markers are associated with the presence of elevated glycated hemoglobin (HbA1c).

Design, setting, and patients: This was a cross-sectional comparison. Patients (n = 133, aged 57.4 ± 15.7 yr) were divided into two groups according to the presence of an HbA1c in a (pre-)diabetic (>5.6) or normal range at the time of blood sampling.

Methods: Using flow cytometry of peripheral blood mononuclear cells (MNCs), cells positive for OCN, the EPC markers (CD34/KDR and CD133(+)/CD34(-)/KDR(+)) and OCN(+) EPCs were counted.

Results: Patients with elevated HbA1c compared with those with normal HbA1c had a significantly higher percentage of circulating OCN(+) MNCs [4.6 (interquartile range 2.68-7.81%) vs. 3.12 (0.99-7.81%), P = 0.035], higher numbers of OCN(+)/CD133(+)/CD34(-)/KDR(+) cells [20 (9-74) vs. 8 (0-19) counts per 100,000 gated events, P < 0.001] and a higher fraction of CD133(+)/CD34(-)/KDR(+) and CD34/KDR cells coexpressing OCN (23.7 ± 24.3 vs. 40.5 ± 34.6%, P = 0.002 and 37.1 ± 39.5 vs. 59.7 ± 37.7%, P = 0.002, respectively). The association between circulating OCN(+)/CD133(+)/CD34(-)/KDR(+) cells and an HbA1c in the (pre-) diabetic range remained strong, even after adjusting for differences in obesity and cardiovascular risk factors, disease, and medications in a multivariate model [odds ratio 1.72 (1.21-2.61), P =0.002].

Conclusion: This study demonstrated that patients with HbA1c in the (pre-)diabetic range have a significant increase in OCN(+) MNCs, and OCN(+)/CD133(+)/CD34(-)/KDR(+) cells, in particular. Whether these cells increase vascular calcification in (pre-)diabetes warrants further studies.

Fig. 1.

Circulating EPCs and EPCs coexpressing OCN. Upper left panel shows the number of circulating CD34⁺/KDR⁺ [40 (10–140) and 30 (none to 100) cells per 100,000 gated events for high and low HbA1c, respectively, P = 0.23], and lower left panel shows CD133⁺/CD34⁻/KDR⁺ cells [10 (none to 53) and 28 (four to 95) cells, respectively, P = 0.03]. Upper middle panel shows number of circulating OCN⁺/CD34⁺/KDR⁺ [11 (three to 24) and 16 (three to 38) cells per 100,000 gated events for high and low HbA1c, respectively, P = 0.24], and lower middle panel shows OCN⁺/CD133⁺/CD34⁻/KDR⁺ cells [eight (none to 19) and 20 (nine to 74) cells, respectively, P < 0.001]. Upper right panel shows the fraction of CD34⁺/KDR⁺ and lower right panel the fraction of CD133⁺/CD34⁻/KDR⁺ cells, which also coexpress OCN [15.7 (1.7–40.9) vs. 41.5 (none to 69.6), P = 0.022, and 19.8 (none to 73.6) vs. 72.9 (19.4–92.9), P = 0.005, respectively]. *, P < 0.05, significant difference between the two groups.