Abstract 657: Increased Urinary Angiotensin Converting Enzyme 2 (ACE2) In Type 2 Diabetic Patients

Abstract

Diabetes and its associated chronic kidney disease (CKD) is a major health burden and there is an urgent need for new sensitive biomarkers to detect and monitor the progression of CKD. Albuminuria is still the gold standard for the evaluation of kidney function. However, its sensitivity and reliability have recently been questioned. ACE2 is highly expressed in renal tubules and has been shown to be shed in the urine of diabetic patients with CKD. The aim of the study was to investigate whether urinary ACE2 is increased in diabetic patients with CKD before the onset of microalbuminuria. Participants were recruited from Dayton VA Medical Center (Dayton, OH, USA). Baseline urinary albumin creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) were determined three months before initiation of the study in non-diabetic patients (UACR <30 mg/g, eGFR=97.40±16 ml/min/1.73 m 2 ), and in diabetic patients with normoalbuminuria (UACR <30 mg/g, eGFR=83.08±17 ml/min/1.73 m 2 ), microalbuminuria (UACR = 30-300 mg/g, eGFR=47.13±23 ml/min/1.73 m 2 ), and macroalbuminuria (UACR >300 mg/g, eGFR=39.68±20 ml/min/1.73 m 2 ). Using fluorogenic and mass spectrometry-based enzyme assays, we measured urinary and plasma ACE2 activity in patients. Urinary ACE2 activity was significantly increased in diabetic patients with normoalbuminuria (0.58±0.2 nmol/hr/mg creatinine), microalbuminuria (1.19 ±0.5 nmol/hr/mg creatinine), and macroalbuminuria (2.265±0.4 nmol/hr/mg creatinine) compared with non-diabetic controls (0.06 ± 0.02 nmols/hr/mg creatinine) (p<0.0001). These results were confirmed by detecting the ACE2 product Ang-(1-7) ( m/z 899) in incubations of urine samples with the natural substrate Ang II ( m/z 1046) using mass spectrometry-based enzyme assays. In addition, urinary ACE2 expression was significantly increased in diabetic patients as determined by western blot analysis (p<0.05). Plasma ACE2 activity was not detectable in control and diabetic patients. In conclusion, urinary ACE2 is increased in diabetic patients with CKD which suggests that urinary ACE2 could be used as an early, noninvasive biomarker for diabetic nephropathy before the onset of microalbuminuria.