Non-classical monocytes frequency and serum vitamin D₃ levels are linked to diabetic foot ulcer associated with peripheral artery disease

Aims/introduction: Peripheral artery disease (PAD) serves as a risk factor for diabetic foot ulcers (DFUs). PAD pathology involves atherosclerosis and impaired immunity. Non-classical monocytes are believed to have an anti-inflammatory role. 1,25-Dihydroxy vitamin D (vitamin D₃ ) is claimed to have immune-modulating and lipid-regulating roles. Vitamin D receptor is expressed on monocytes. We aimed to investigate if circulating non-classical monocytes and vitamin D₃ were implicated in DFUs associated with PAD.

Materials and methods: There were two groups of DFU patients: group 1 (n = 40) included patients with first-degree DFUs not associated with PAD, and group 2 (n = 50) included patients with DFU with PAD. The monocyte phenotypes were detected using flow cytometry. Vitamin D₃ was assessed by enzyme-linked immunosorbent assay.

Results: DFU patients with PAD showed a significant reduction in the frequency of non-classical monocytes and vitamin D₃ levels, when compared with DFU patients without PAD. The percentage of non-classical monocytes positively correlated with vitamin D₃ level (r = 0.4, P < 0.01) and high-density lipoprotein (r = 0.5, P < 0.001), whereas it was negatively correlated with cholesterol (r = -0.5, P < 0.001). Vitamin D₃ was negatively correlated with triglyceride/high-density lipoprotein (r = -0.4, P < 0.01). Regression analysis showed that a high vitamin D₃ serum level was a protective factor against PAD occurrence.

Conclusions: Non-classical monocytes frequency and vitamin D₃ levels were significantly reduced in DFU patients with PAD. Non-classical monocytes frequency was associated with vitamin D₃ in DFUs patients, and both parameters were linked to lipid profile. Vitamin D₃ upregulation was a risk-reducing factor for PAD occurrence.