The synergistic effects of saxagliptin and metformin on CD34+ endothelial progenitor cells in early type 2 diabetes patients: a randomized clinical trial

Abstract

Aims: Type 2 diabetes is associated with endothelial dysfunction leading to cardiovascular disease. CD34+ endothelial Progenitor Cells (EPCs) are responsible for endothelial repair and neo-angiogenesis and can be used as a cardiovascular disease risk biomarker. This study investigated whether the addition of saxagliptin, a DPP-IV inhibitor, to metformin, may reduce cardiovascular disease risk in addition to improving glycemic control in Type 2 diabetes patients.

Methods: In 12 week, double-blind, randomized placebo-controlled trial, 42 subjects already taking metformin 1-2 grams/day were randomized to placebo or saxagliptin 5 mg. Subjects aged 40-70 years with diabetes for < 10 years, with no known cardiovascular disease, BMI 25-39.9, HbA1C 6-9% were included. We evaluated EPCs number, function, surface markers and gene expression, in addition to arterial stiffness, blood biochemistries, resting energy expenditure, and body composition parameters. A mixed model regression to examine saxagliptin vs placebo, accounting for within-subject autocorrelation, was done with SAS (p < 0.05).

Results: Although there was no significant increase in CD34+ cell number, CD31+ cells percentage increased. Saxagliptin increased migration (in response to SDF1α) with a trend of higher colony formation count. MNCs cytometry showed higher percentage of CXCR4 double positivity for both CD34 and CD31 positive cells, indicating a functional improvement. Gene expression analysis showed an upregulation in CD34+ cells for antioxidant SOD1 (p < 0.05) and a downregulation in CD34- cells for IL-6 (p < 0.01). For arterial stiffness, both augmentation index and systolic blood pressure measures went down in saxagliptin subjects (p < 0.05).

Conclusion: Saxagliptin, in combination with metformin, can help improve endothelial dysfunction in early diabetes before macrovascular complications appear. Trial registration Trial is registered under clinicaltrials.gov, NCT02024477.

Keywords: Arterial stiffness; DPP-4 inhibitor; Diabetes; Endothelial progenitor cells; Saxagliptin.

Figures

Fig. 1

CFU-Hill’s colonies as an indicator of vascular health. Experiments were performed in duplicate and values are given as mean ± SD (p = 0.07, for the visit x treatment interaction t-test in a random effects mixed model)

Fig. 2

Migration of CD34+ cells in response to SDF-1α (100 ng/mL). Results are expressed as fluorescence ratio between cells exposed to the chemotactic factor and cells exposed to chemoattractant-free media (control) followed by lysis in presence of CyQuant GR dye. Experiments were performed in duplicate and results are given as mean ± SD (p 

Fig. 3

Representative image (a and b) indicating the CD34+ CXCR4+ expression in MNCs by flow cytometry. CD34+ CXCR4+ expression is higher for the saxagliptin group at visit 3 than visit 1 (7.95 and 4.64%, respectively). c Double positivity for CD34 and CXCR4 along the visits for placebo and saxagliptin groups (p < 0.01)

Fig. 4

CD31+ CXCR4+ expression in MNCs assessed by flow cytometry. Double positivity of CD31 and CXCR4 is higher for saxagliptin group at visit 2 and visit 3 in comparison to placebo group (p 

Fig. 5

Effect of saxagliptin on gene expression of CD34+ (a) and CD34− (b) cells. A low number of CD34+ cells obtained resulted in a reduced amount of mRNA affecting the number of samples suitable for analysis. The genes affected by saxagliptin treatment were: SOD1 (n = 11), GPX1 (n = 11), CASP3 (n = 10), IL6 (n = 13), IGF1 (n = 7). *p < 0.05; **p < 0.01. Results are relative to visit 1 (control)

Fig. 6

a Fat free mass (kg) show that the saxagliptin group had a sharp decline after visit 1, but then a rise after visit 2, and the placebo group remained relatively stable (0.072). b  % Body Fat across visits 1–3. Saxagliptin patients had a decline from visit 1 to 3, whereas the control group increased at visit 3 (p = 0.079). c % total body water remained relatively stable for the placebo group, but increase in saxagliptin (p = 0.098)

Fig. 7

a Shows adiponectin values from visit 1 to visit 3. Saxagliptin showed a decrease throughout the study, after visit 2, while the placebo group increased steadily from visit 1 to visit 3 (p = 0.01). b Shows serum creatinine values from visit 1 to visit 3. There is a steep decline from visit 1 to 2 in the placebo group, while levels remain stable in the saxagliptin group (p = 0.12)

Fig. 8

a Shows the arterial stiffness parameter, augmentation index adjusted for a heart rate of 75. Saxagliptin subjects remained stable across visit 1 through 3, whereas the control subjects had an increase in arterial stiffness (p = 0.04). b Shows radial systolic blood pressure in saxagliptin, compared to Placebo, across the three visits. Saxagliptin blood pressure remains stable across visits 1 and 2, but then drops in visit 3. In the placebo group, blood pressure drops at visit 2, but then rises dramatically by visit 3 (p = 0.009)