Authors’ reply
We would like to thank Prof. Stompór for his interest in our article1 and for joining the discussion on the role of renalase in chronic kidney disease (CKD).
Renalase is a flavoprotein with enzymatic activity. The first studies suggested that renalase is mainly responsible for the metabolism of catecholamines and plays a significant role in the regulation of the adrenergic nervous system and blood pressure. Recent studies indicated that renalase has cytoprotective, renoprotective, antifibrotic, and antiapoptotic properties as well as may inhibit oxidative stress. The role of renalase in physiology and pathogenesis of diseases remains controversial. Early studies suggested that patients with CKD have reduced renalase levels and renalase deficiency is associated with increased levels of catecholamines and contributes to hypertension and cardiovascular diseases.2,3 Recent studies indicated increased levels of renalase in patients with CKD that correlated negatively with kidney function.4,5 We agree with Prof. Stompór that high levels of adrenergic hormones may stimulate renalase secretion or high levels of adrenergic hormones may be secondary to low levels of renalase.
In our study, serum concentrations of renalase in patients with CKD were increased, whereas the concentrations of renalase in erythrocytes of CKD patients were decreased. Urinary renalase concentrations did not differ between patients with CKD and the control group. Urinary and erythrocyte renalase concentrations were negatively correlated with estimated glomerular filtration rate.
The results of our study suggest that increased serum renalase levels may be caused by a compensatory secretion of renalase in patients with CKD induced by elevated levels of catecholamines. Unfortunately, this increase in renalase levels cannot sufficiently counterbalance the development of cardiovascular complications in patients with CKD.
Additionally, we observed decreased levels of renalase in erythrocytes. We concur with Prof. Stompór that there may be many hypotheses explaining this finding. Decreased renalase levels in erythrocytes of patients with CKD may be caused by the primarily decreased synthesis of renalase in CKD, the reduced lifespan of erythrocytes in CKD, or decreased renalase activity in red blood cell precursors in bone marrow. Despite numerous studies, the role of renalase in CKD remains ambiguous and requires further studies.
Prof. Andrzej Pawlik, MD, PhD, Department of Physiology, Pomeranian Medical University, ul. Powstańców Wielkopolskich 72, 70-111 Szczecin, Poland, phone: +48914661611, email: pawand@poczta.onet.pl
Magda Wiśniewska, Violetta Dziedziejko, Krzysztof Safranow, Andrzej Pawlik (MW: Clinical Department of Nephrology, Transplantology and Internal Medicine, Pomeranian Medical University, Szczecin, Poland; VD, KS: Department of Biochemistry and Medical Chemistry, Pomeranian Medical University, Szczecin, Poland; AP: Department of Physiology, Pomeranian Medical University, Szczecin, Poland)
None declared.
Wiśniewska M, Dziedziejko V, Safranow K, Pawlik A. Renalase in chronic kidney disease: the evolving story. Authors’ reply. Pol Arch Intern Med. 2020; 130: 90. doi:10.20452/pamw.15170
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