Changes in serum and urine vitamin D binding protein concentrations in type 2 diabetes

Objective To determine the changes in serum and urine vitamin D binding protein(VDBP)concentrations in type 2 diabetes, and to explore the clinical significance. Methods The serum and urine VDBP concentrations in 102 healthy individuals and 106 type 2 diabetic patients were determined by ELISA. For analysis and comparison, 106 type 2 diabetic patients were divided into imperfect glycemic control subgroup and perfect glycemic control subgroup, microalbuminuria subgroup and normal albuminuria subgroup. Results The cut-off point of serum VDBP concentrations was 60.6 μg/ml and the cut-off point of the urine ratio of VDBP and creatinine was 7.76 mg/g, and both were determined according to the upper limit of 97. 5 % credit intervals in 110 healthy individuals. Serum VDBP concentration and the urine ratio of VDBP to creatinine in type 2 diabetic patients were significantly higher than those in the healthy individuals(P<0.01), the imperfect glycemic control subgroup had higher serum VDBP concentrations and the urine ratio of VDBP to creatinine than those in the perfect glycemic control subgroup(P<0.05). The microalbuminuria subgroup had higher urine ratio of VDBP to creatinine than that in the normal albuminuria subgroup(P<0.01). Urine ratio of VDBP to creatinine in diagnosing early diabetic nephropathy had sensitivity of 96. 4 %, specificity of 68 %, and concordance of 83%. Conclusion Detection of serum VDBP levels has some reference value in understanding the state of diabetes. Combined determinations of urine ratio of VDBP to creatinine and ratio of albumin to creatinine have significant clinical value in the early diagnosis of diabetic nephropathy. Key words: Vitamin D binding protein; Diabetes mellitus, type 2; Diabetic nephropathy