The specific relationship between vitamin D deficiency and diabetic nephropathy among patients with advanced chronic kidney disease: A cross-sectional study in Gran Canaria, Spain

Abstract

Aims: Vitamin D deficiency is highly prevalent in subjects with advanced chronic kidney disease (CKD), but diabetes, the most common cause of CKD, has also been linked to low levels of serum 25-hydroxyvitamin D [25(OH) D]. We compare vitamin D status between subjects with type 2 diabetes-related advanced CKD and subjects with either advanced CKD without diabetes or type 2 diabetes without advanced CKD. Methods: Subjects were patients with advanced CKD (estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73 m(2)) from February 2011 to November 2013 (113 with diabetes-related CKD and 80 without diabetes) and 61 patients with long-lasting type 2 diabetes without advanced CKD, simultaneously enrolled from our center. Participants fulfilled a survey questionnaire and underwent physical examination, blood samples, and 24-h urine collection. Kidney disease was assessed using eGFR and 24-h urinary protein excretion. Serum 25(OH) D was measured by chemiluminescence immunoassay. Results: The prevalence of vitamin D deficiency (25(OH) D < 20 ng/mL) was 70.8% in subjects with diabetes-related CKD, 38.8% in subjects with non-diabetic CKD and 41% in subjects with diabetes without advanced CKD. Adjusted means (95% confidence interval (CI)) of 25(OH) D in participants with diabetes-related CKD, in nondiabetic participants with CKD, and in participants with diabetes without advanced CKD were, respectively, 17.5 (14.2 - 20.7), 23.6 (19.4 - 27.8), and 23.5 (16.8 - 30.3) ng/mL (p = 0.023). Conclusions: Low vitamin D status is characteristically associated with advanced diabetic nephropathy. This relationship is not entirely attributable to the individual effects of CKD or long-lasting diabetes.