The Relationship Between Proteinuria and Urinary Angiotensinogen Levels in Patients with Nephrotic Syndrome

OBJECTIVE: Recently, urinary angiotensinogen (AGT) is used frequently as a marker of intrarenal renin-angiotensin-aldosterone system (RAAS) activity. In this study, we aimed to investigate the relationship between urinary AGT and proteinuria in patients with nephrotic syndrome.

MATERIAL and METHODS: Twenty-four patients followed up with nephrotic syndrome were included. The patients diagnosed with vasculitis, lupus nephritis, diabetes mellitus or amyloidosis, those with a glomerular filtration rate (GFR) <90 ml/min/1.73 m2, and patients receiving RAAS inhibitors, aldosterone receptor antagonists, diuretics or immunosuppressive drugs were excluded. Urinary AGT was calculated as AGT-to-creatinine ratio and proteinuria was calculated as protein-to-creatinine ratio (UP/Ucre) (mg/mg). Logarithmic transformations of UAGT/Ucre and UP/Ucre values were calculated to obtain the normal distributions.

RESULTS: Log(UP/Ucre) was 2.9±0.9, and log(UAGT/Ucre) was 0.7±0.2. There was a strong positive correlation between log(UP/Ucre) and log(UAGT/Ucre) (r=0.783, p<0.001). The strong correlation between log(UP/Ucre) and log(UAGT/Ucre) remained when controlled for the effects of 24-hour mean systolic and diastolic blood pressures (r=0.752, p=0.001).

CONCLUSION: We found a strong correlation between proteinuria and urinary AGT levels. Different from the previous studies, GFR was >90 ml/min in all patients. Therefore, high urinary AGT levels in earlier stages of nephrotic syndrome may reflect intrarenal RAAS activity that is supposed to play a role in pathogenesis of the disease.