The association of urinary vitamin D binding protein with kidney dysfunction and hypovitaminosis D in patients at risk for type 2 diabetes

One possible explanation for hypovitaminosis D in type 2 diabetes (T2DM) is that vitamin D metabolites may still be bound to the vitamin D binding protein (VDBP) as the protein is lost in urine. Given that VDBP may be linked to both kidney dysfunction and hypovitaminosis D, the objective is to investigate longitudinal associations of urinary VDBP on measures of kidney health and vitamin D status. Data from a cohort of adults at risk for T2DM was used (n=729). Albumin-to-creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR) were measures of kidney function while 25-hydroxyvitamin D (25(OH)D) indicated vitamin D status. Adjusted generalized estimating equation models showed that uVDBP was associated with higher ACR over time, but was not associated with changes in eGFR or 25(OH)D. These results emphasize that although mild VDBP loss is not linked with hypovitaminosis D, urinary VDBP may be a useful biomarker for tubular damage.M.Sc