Intra-body dynamics of d -serine reflects the origin of kidney diseases

Introduction d -Serine, present only in trace amounts in humans, is now recognized as a biomarker of chronic kidney disease (CKD). CKD is heterogeneous in its original kidney diseases, whose diagnoses require kidney biopsy. In this study, we examined whether the intra-body dynamics of d- serine, indexed by its blood and urinary levels, reflects the origin of kidney diseases. Methods Patients with six kinds of kidney disease undergoing kidney biopsy were enrolled in a single center. Levels of d- and l -serine were measured using two-dimensional high-performance liquid chromatography. The associations between the origin of kidney diseases and the intra-body dynamics of d- serine were examined using multivariate cluster analyses. Results Unlike the non-CKD profile, patients with CKD showed broadly-distributed profiles of intra-body dynamics of d- serine. The plasma level of d- serine plays a key role in the detection of kidney diseases, whereas a combination of plasma and urinary levels of d- serine distinguished the origin of CKD, especially lupus nephritis. Conclusion Intra-body dynamics of d- serine have the potential to predict the origin of kidney diseases. Monitoring of d- serine may guide specific treatments for the origin of kidney diseases.