Investigation of Urinary Angiotensinogen in Renal Transplant Recipients

Background

Recent studies have indicated that angiotensinogen (AGT) is also locally produced in the kidney and that urinary AGT is a marker of local renal renin-angiotensin system activation. Because urinary AGT levels are significantly higher in patients with chronic kidney disease (CKD) than in patients without CKD and correlate with urinary albumin and other levels, urinary AGT is increasingly recognized as a marker for CKD monitoring, prognosis, and treatment. In this study, we investigated urinary AGT levels in renal transplant recipients.

Methods

Among the patients who were treated as outpatients at the Department of Urology of Osaka City University Hospital from March 2012 to April 2013, 146 stable renal transplant recipients and 50 donors who gave informed consent were studied. Urinary AGT and creatinine (Cr) levels were measured. The urinary AGT-to-Cr ratio was calculated, and its correlation with clinical parameters was examined.

Results

The urinary AGT-to-Cr ratio of the renal transplant recipients was significantly higher than that of the renal transplant donors (P = .0143). Furthermore, the urinary AGT-to-Cr ratio had a significantly positive correlation with the urinary albumin-to-Cr ratio (ACR; r = 0.39, P < .0001), while on the other hand, it had a significantly negative correlation with estimated glomerular filtration rate (eGFR; r = −0.31, P = .0002). Multiple linear regression analysis of factors associated with eGFR showed that urinary AGT was a significant and independent factor after adjusting for age, sex, and ACR.

Conclusions

Our results indicated that urinary AGT levels were elevated in renal transplant recipients. In addition, urinary AGT significantly correlated with renal function and degree of albuminuria.