Urinary Immature Truncated O-glycans Correlate with Glomerular and Tubulointerstitial Severity of Biopsy-Proven Diabetic Kidney Disease

Background: Since it has been technically challenging to quantify glycans due to their structural complexity, little is known about the association between changes of glycosylation and the progression of DKD. We previously reported that urinary levels of immature truncated O-glycans, referred to as DKD related O-glycans, strongly predicted renal prognosis in patients with type 2 diabetes (Diabetes Care. 2018;41:1765-1775). However, the association of those O-glycans in urine and blood with the pathological findings of DKD remains elusive. Methods: We enrolled 36 patients with type 2 diabetes and biopsy-proven DKD in this study. Using serum and urine samples at renal biopsy, we measured the levels of Cy3-labeled glycoproteins binding to 45 lectins with different specificities. Specifically, we analyzed binding signals of DKD related O-glycans to the lectins, e.g. Sialyl-Tn to SNA, Galb4GlcNAc to RCA120, T-antigen to ABA, Jacalin, and ACA, and GalNAca3GalNAc to DBA. The RPS pathologic classification was used to evaluate glomerular and tubulointerstitial lesions in DKD. The relationships of glomerular classes and interstitial fibrosis and tubular atrophy (IFTA) scores with serum and urinary DKD related O-glycan levels were analyzed. Results: At renal biopsy, 29 patients had macroalbuminuria (81%), and 7 patients showed either normoalbuminuria (11%) or microalbuminuria (8%). The profile of DKD related O-glycans in urine was distinct from that in serum. Among glomerular classes I, IIA, and IIB, urinary DKD related O-glycans gradually increased (p for trend <0.05 for all 6 glycans), while such trend was observed only in RCA120-binding O-glycans in the serum. In contrast, higher urinary levels of T-antigens recognized by ABA, Jacalin, and ACA were significantly associated with higher IFTA scores (P for trend: 0.017, 0.023, and 0.007, respectively), whereas there was no correlation between serum DKD related O-glycans and IFTA scores. Conclusion: This study discovered that urinary levels of DKD related O-glycans, especially T-antigens, were correlated with the pathological development of early glomerular lesions and tubulointerstitial lesions. Given that such findings were observed in only urinary sample, urinary DKD related O-glycans might reflect the alteration of glycosylation in tissues of DKD. Funding: Private Foundation Support