Circulating Angiotensin-Converting Enzyme 2 Activity in Kidney Transplantation: A Longitudinal Pilot Study

Abstract

Background/Aims: Angiotensin-converting enzyme 2 (ACE2) is the only known active homologue of ACE, and degrades angiotensin (Ang) II and Ang I to Ang(1–7) and Ang(1–9), respectively. The role of ACE2 in kidney transplant (KT) is unknown. Our objective was to investigate circulating ACE2 activity in KT patients, and the relationship between serum ACE2 activity and age, gender, graft function and cardiovascular risk markers in KT patients. Methods: 113 KT patients with stable graft function were included in this cross-sectional study. Circulating ACE2 activity was assessed using a fluorescent assay. Results: Circulating ACE2 activity was detectable in KT patients and was increased in KT with ischemic heart disease as compared to KT without ischemic heart disease (105.9 ± 8.7 vs. 97.1 ± 7.05 relative fluorescence units (RFU)/µl/h, p < 0.05). ACE2 activity was increased in male KT as compared to females (105.2 ± 9.1 vs. 84.7 ± 6.9 RFU/µl/h, p = 0.05). ACE2 activity correlated positively with serum creatinine (r = 0.27), serum urea (r = 0.29), age (r = 0.24), aspartate transaminase (r = 0.39), alanine transaminase (r = 0.48), γ-glutamyl transferase (γ-GT) (r = 0.52), age (r = 0.24), and glycosylated hemoglobin (r = 0.19) (p < 0.05). By multiple regression analysis, age, serum creatinine, and serum γ-GT were independent predictors of serum ACE2 activity (r = 0.66, p < 0.001). Conclusions: Circulating ACE2 activity is measurable in KT patients and directly correlates with age, renal allograft and liver function parameters. These findings suggest that measurement of serum ACE2 may be used as a non-invasive marker to understand the role of the renin-angiotensin system in KT patients.

Characterization of ACE and ACE2 Expression within Different Organs of the NOD Mouse

“…ACE2 enzymatic activity assay was performed as previously published by our group [25,44,45,46] and adapted to different tissues. Briefly, 5 μL of serum or 5 μg of tissue samples that were previously homogenized were incubated using a 100 mM Tris-HCl, 600 mM NaCl, 10 μM ZnCl 2 , pH 7.5 buffer in the presence of protease inhibitors containing 100 μM captopril, 5 μM amastatin, 5 μM bestatin (all from Sigma-Aldrich, Madrid, Spain), and 10 μM Z-Pro-prolinal (Enzo Life Sciences, Grupo Taper, Madrid, Spain).…”

Role of Circulating Angiotensin Converting Enzyme 2 in Left Ventricular Remodeling following Myocardial Infarction: A Prospective Controlled Study

“…The ACE2 fluorescent enzymatic assay protocol was performed as previously described with modifications, using an ACE2 quenched fluorogenic substrate (Mca-Ala-Pro-Lys(Dnp)-OH, Enzo Life Sciences) [10], [11]. Briefly, 20 µL of serum was incubated with a buffer (100 mM Tris-HCl, 600 mM NaCl, 10 µM ZnCl 2 , pH 7.5) in the presence of protease inhibitors, including 100 µM captopril, 5 µM amastatin, 5 µM bestatin (all from Sigma-Aldrich), and 10 µM Z-Pro-prolinal (Enzo Life Sciences).…”

RAS and sex differences in diabetic nephropathy

“…In addition, in a multivariate analysis, circulating ACE2 activity directly correlated with the classical cardiovascular risk factors, namely older age, diabetes, and male sex (7). Increased activity of circulating ACE2 has also been detected in males compared with females after kidney transplant (112) and in hemodialysis patients (99). Mizuiri et al did not find sexual dimorphism in urinary ACE2 activity or protein levels in patients with CKD (78).…”