Objective: To evaluate the association between vitamin D deficiency and diabetic nephropathy in type 2 diabetic patients.
Methods: A total of 594 patients with type 2 diabetes were enrolled from the inpatients of the Nanjing Medical University Affiliated Nanjing Hospital. Fasting serum lipid profile, 25-hydroxycalciferol vitamin D and urinary albumin excretion rate were investigated. The relationship between nephropathy and vitamin D deficiency ( < 20 µg/L) or insufficiency (20-<30 µg/L) was analyzed.
Results: Nephropathy was found in 177 subjects (29.8%) with albuminuria in 141 and proteinuria in 36 subjects. Vitamin D deficiency was found in 180 subjects and insufficiency in 157 subjects. The proportion of vitamin D deficiency was higher in the individuals with nephropathy than those without nephropathy (36.2% vs 27.8%, P < 0.05). The urinary albumin excretion rate was significantly higher in the patients with vitamin D deficiency than those with normal vitamin D concentration [(123.0 ± 299.2) mg/24h vs (47.6 ± 97.1) mg/24h, P < 0.01]. The prevalence of nephropathy was higher in the patients with vitamin D deficiency than those with normal vitamin D concentration (35.6% vs 26.1%, P < 0.05), while the prevalence of proteinuria was higher in patients with vitamin D deficiency (12.2% vs 3.1%, P < 0.01). Logistic regression analysis demonstrated that vitamin D deficiency was associated with nephropathy (OR 1.57, 95%CI 1.04-2.37), even after the adjustment for age, gender, hypertension, dyslipidemia, smoking status, use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (OR 1.78, 95%CI 1.12-2.81). The Vitamin D concentration was significantly negatively correlated with urinary albumin excretion rate (r = -1.783, P < 0.001).
Conclusions: Type 2 diabetic patients have a high prevalence of vitamin D deficiency. Vitamin D deficiency is independently associated with diabetic nephropathy.