METHODS: This prospective cross-sectional study involved 70 patients with diabetic nephropathy; 40 were categorized into the group with nondeficient serum 25-hydroxyvitamin D levels [25(OH)D >50 nmol/l], whereas 30 patients were categorized to the group with deficient serum 25(OH)D (<50 nmol/l). Microvascular endothelial function was determined using laser Doppler fluximetry and the process of iontophoresis. Acetylcholine and sodium nitroprusside were used to determine endothelium-dependent and independent vasodilatation.

RESULTS: Mean age of patients was 56.7 ± 3.8 years; 50 were men, whereas 20 were women. Mean serum 25(OH)D in the vitamin D-nondeficient group was 69.4 ± 2.9 nmol/l; the level in the vitamin D-deficient group was 42.1 ± 1.3 nmol/l, P < 0.001. Endothelium-dependent vasodilatation was lower in the vitamin D-deficient group compared with the vitamin D-nondeficient group (23.6 ± 2.7 versus 37.3 ± 3.8 arbitrary units, P = 0.004). No significant differences were observed between the two groups in their hsCRP levels, mean age, estimated glomerular filtration rate, systolic blood pressure (SBP) and diastolic blood pressure (DBP) and glycosylated haemoglobin.