Serum 25-Hydroxyvitamin D Level Is Positively Associated with Vascular Reactivity Index in Patients with Type 2 Diabetes Mellitus

Circulating 25-hydroxyvitamin D (25(OH)D) significantly influences endothelial function. This study assessed the correlation between serum 25(OH)D and endothelial function using the vascular reactivity index (VRI) in patients with type 2 diabetes mellitus (T2DM). Fasting blood samples from 102 T2DM participants and VRI were assessed. Patients were divided into three categories based on VRI: low (VRI < 1.0), intermediate (1.0 <= VRI < 2.0), and good (VRI >= 2.0). Among these patients, 30 (29.4%) had poor, 39 (38.2%) had intermediate, and 33 (32.4%) exhibited good vascular reactivity. Higher serum fasting glucose (p = 0.019), glycated hemoglobin (p = 0.009), and urinary albumin-to-creatinine ratio (p = 0.006) were associated, while lower prevalence of hypertension (p = 0.029), lower systolic blood pressure (p = 0.027), lower diastolic blood pressure (p < 0.001), and lower circulation 25(OH)D levels (p < 0.001) were associated with poor vascular reactivity. Significant independent associations between diastolic blood pressure (p = 0.002) and serum 25(OH)D level (p < 0.001) and VRI were seen in T2DM patients according to multivariable forward stepwise linear regression analysis. Serum 25(OH)D positively correlated with VRI values, and lower levels of serum 25(OH)D were linked to endothelial dysfunction in T2DM patients.