Intrarenal podocalyxin level may predict dialysis-free survival in diabetic kidney disease
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Among patients with diabetic kidney disease, intrarenal podocalyxin level was an independent predictor of dialysis-free survival, according to data published in Kidney Medicine.
However, researchers note intrarenal podocalyxin level may not be suitable for routine clinical use.
“Preliminary studies showed that urinary podocalyxin level of [diabetic kidney disease] DKD patients was higher than that of the control group, and the level positively correlated with glycemic control and urinary albumin excretion, indicating that urinary podocalyxin level might serve as a biomarker of DKD,” Lingfeng Zeng, MB, from the Carol and Richard Yu Peritoneal Dialysis Research Centre, and colleagues wrote. “In the present study, we compared the role of urinary and intrarenal levels of podocalyxin and podocin (a prototype slit-diaphragm protein) biomarker in patients with biopsy-proven DKD.”
In an observational cohort study, researchers examined 118 consecutive patients with biopsy-proven DKD. A total of 13 patients with hypertensive nephrosclerosis, but without DKD, served as the controls.
Researchers measured the urinary and kidney levels of podocalyxin and podocin in all patients. Patients were followed for up to 12 months, with kidney function assessed every 3 months.
With dialysis-free survival, kidney event-free survival or a decline in kidney function during 12 months as primary outcomes of the study, researchers considered urinary podcalyxin and podocin levels and the corresponding intrarenal levels as predictors.
Exposure data were derived by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA).
Although the urinary podocalyxin level was associated with its messenger RNA level (mRNA), it did not predict the progression of DKD in patients. Researchers observed a modest correlation between intrarenal podocalyxin levels and its urinary mRNA and ELISA levels. However, intrarenal podocalyxin was an independent predictor of dialysis-free survival and showed an insignificant trend of predicting kidney event-free survival. Additionally, urinary podocin level by ELISA showed a modest association with the rate of kidney function decline and did not predict dialysis-free survival.
“[O]ur results show that the urinary podocin level may be a prognostic marker of DKD. Although the intrarenal podocalyxin level also has prognostic value, it does not appear to be a promising clinical marker in view of the invasive nature of the test, and urinary podocalyxin, either at mRNA or protein level, does not provide additional prognostic information,” Zeng and colleagues wrote. “Our results also suggest that qualitative changes in various cellular compartments of the podocyte, rather than the change in the absolute podocyte number, may be an important pathological alteration in DKD.”
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