High Prevalence of Vitamin D Deficiency and Correlation with Cystatin-C and Other Cardiovascular and Renal Risk Biomarkers in Patients with Type 2 Diabetes Mellitus Complicated with Hypertension

Background: Vitamin D is increasingly investigated as having a role in Type 2 Diabetes Mellitus (T2DM) and its cardiovascular and renal complications. Objective: This study aimed to investigate the association between 25-hydroxyvitamin D (25-OHD) and biomarkers of cardiovascular and renal complications, including cystatin-C. Methods: This cross-sectional study involved 117 participants with T2DM that was not complicated with cardiovascular or renal diseases except hypertension. 25-OHD was measured by electrochemiluminescence immunoassay, while cystatin-C was measured by enzyme-linked-immunosorbent-assay. Other biomarkers, including lipids, creatinine, urea and glycemic measures, were determined by the routine biochemistry assays. Results: The prevalence of vitamin D deficiency was 74.36%. There was no significant difference in cardiovascular and renal biomarkers, including glucose, HbA1c, lipids, urea, creatinine and cystatin-C between participants with adequate and deficient vitamin D (p-values<0.05). Participants with adequate vitamin D were older in age, more obese and having lower eGFR (p-values<;0.05). 25-OHD was weakly correlated with age, duration of DM, urea, creatinine and inversely correlated with eGFR (rvalues<0.32, p-values<0.05). Although creatinine and cystatin-C were directly correlated (r=0.42, pvalue<0.001), cystatin-C and 25-OHD were not correlated (p-value<0.05). Hypertensive participants were more obese, having a longer duration of DM and higher urea and cystatin-C compared to nonhypertensive participants (p-values<0.05). Binary logistic regression analysis revealed that hypertension could be predicted from increased BMI. Conclusion: 25-OHD was not found to be correlated with cardiovascular risk biomarkers, but it was correlated with renal biomarkers, including urea, creatinine and eGFR. Cystatin-C and 25-OHD were not observed to be correlated to each other, but both were correlated to renal function. Obesity was a significant predictor of hypertension.