Angiotensin converting enzyme (ACE) 2 is a homologue of ACE that catalyzes the
conversion of Angiotensin (Ang) II into Ang1-7, which induces vasodilation, anti-fibrotic,
anti-proliferative and anti-inflammatory effects. Given that ACE2 counterbalances the effects
of Ang II, it has been proposed as a biomarker in kidney disease patients. Circulating ACE2
has been studied in human and experimental studies under physiological and pathological
conditions and different techniques have been assessed to determine its enzymatic activity. In
patients with cardiovascular (CV) disease circulating ACE2 has been shown to be increased.
In addition, hypertensive and diabetic patients have also shown higher circulating ACE2 activities.
A study in type 1 diabetes patients found a negative association between circulating
ACE2 and estimated glomerular filtration rate in male and female patients. Recently, it has
been demonstrated that circulating ACE2 is increased in male patients with chronic kidney
disease (CKD) and that it is independently associated with other classical CV risk factors,
such as advanced age and diabetes. Furthermore, circulating ACE2 has been shown to be associated
with silent atherosclerosis and CV outcomes in CKD patients. In diabetic nephropathy,
experimental studies have demonstrated an increase in circulating ACE2 activity both at
early and late stages of the disease, as well as a direct association with increased urinary albumin
excretion, suggesting that it may be increased as a renoprotective mechanism in these
patients. In this paper we will review the measurement of circulating ACE2 and its role in
kidney disease, as well as its potential role as a renal and CV biomarker.