A recent study shows that endocan is as a potential diagnostic or prognostic biomarker for chronic kidney disease.
In the study by Yilmaz et al., there are some limitations. They have performed just a single measurement of serum endocan. A single point measurement of serum endocan is a little relevant, but serial multiple measurements could give more information on prognostic outcome of CKD. For instance, Li and Wang et al. performed multiple point measurements of serum endocan level during evaluation of acute rejection after renal transplantation. Multiple measurement of serum endocan level could discriminate acute rejection from renal allograft dysfunction. They additionally showed that endocan expression was located mainly in glomeruli, which may give a clue to the origin of serum endocan in CKD patients. Another instance is a report on serum endocan levels in septic patients. The severity of sepsis showed positive correlation with initial serum endocan levels. Moreover, it was significantly increased in non-survivors.
However, the lack of multiple follow-up data on serum endocan levels prohibits the evaluation of sepsis treatment outcome, which requires multiple measurements. Another limitation is that Yilmaz et al.did not rule out accompanying cancers or other inflammatory diseases, which could be sources of serum endocan. Serum endocan is detected as a few hundred picograms in 1 ml of serum under normal physiologic conditions. Serum endocan solely could not inform regarding the location or kinds of diseases, but its detection over the normal range may give a clue to search for some diseases, such as systemic inflammatory diseases, cardiovascular diseases, and various cancers. Finally, it is unclear whether the increased serum endocan level in CKD patients was the result of an increased secretion or a decreased renal clearance. The clearance mechanism of endocan has not yet been identified. As renal function declines, serum endocan level increases, which may be due to increased production or decreased clearance. The former might be due to kidney inflammation, which is preferable. In this report, serum endocan levels of patients in the third quartile (6.6 ng/ml) or fourth quartile (13.3 ng/ml) in the CKD classification based on estimated glomerular filtration rate were significantly higher than those of patients in the first (1.2 ng/ml) and second quartiles (2.8 ng/ml). This pattern was the same for high-sensitivity C-reactive protein, which was induced considerably by kidney inflammation. However, the reason why serum endocan levels were significantly higher in CKD than in any other disease conditions must be evaluated. The possibility that the increased serum endocan levels in CKD patients resulted from decreased clearance could be evaluated simply by urine endocan level. Serial follow-up of serum endocan levels in CKD patients could also be informative in this regard.
In conclusion, Yilmaz et al. have reported an endocan as a novel prediction marker of all-cause mortality and cardiovascular events in CKD patients. More detailed study of molecular mechanisms in endocan expression and degradation in CKD may increase the value of serum endocan levels.
Reference
Endocan as a potential diagnostic or prognostic biomarker for chronic kidney disease, Kidney International (2014) 86, 1079–1081; doi:10.1038/ki.2014.292