title: Circulating angiotensin-converting enzyme 2 activity in kidney transplantation: a longitudinal pilot study.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Nephrology, Hospital del Mar-IMIM, Barcelona, Spain. msoler@parcdesalutmar.cat
authors.forename: María José
authors.initials: MJ
authors.lastname: Soler
authors.forename: Marta
authors.initials: M
authors.lastname: Riera
authors.forename: Marta
authors.initials: M
authors.lastname: Crespo
authors.forename: Marisa
authors.initials: M
authors.lastname: Mir
authors.forename: Eva
authors.initials: E
authors.lastname: Márquez
authors.forename: María José
authors.initials: MJ
authors.lastname: Pascual
authors.forename: Josep M
authors.initials: JM
authors.lastname: Puig
authors.forename: Julio
authors.initials: J
authors.lastname: Pascual
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000085962:Angiotensin-Converting Enzyme 2; D002318:Cardiovascular Diseases / Q000097:blood* / Q000453:epidemiology*; D015897:Comorbidity; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000453:epidemiology*; D016030:Kidney Transplantation / Q000706:statistics & numerical data*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D007703:Peptidyl-Dipeptidase A / Q000097:blood*; D010865:Pilot Projects; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D017678:Sex Distribution; D013030:Spain / Q000453:epidemiology; D055815:Young Adult
chemical_list: D007703:Peptidyl-Dipeptidase A; C000705307:ACE2 protein, human; D000085962:Angiotensin-Converting Enzyme 2