Abstract
Aim. Blockade of the renin-angiotensin-aldosterone system (RAAS) affects both the glomerulus and tubules. We aimed to investigate the effect of irbesartan on the tubular markers: urinary (u) neutrophil gelatinase associated protein (NGAL), Kidney injury molecule 1 (KIM1) and liver-fatty acid-binding protein (LFABP). Methods. A substudy of a double-masked, randomized, cross-over study including 52 patients with type 2 diabetes, hypertension and microalbuminuria. After 2 months washout of all antihypertensive medication except bendroflumethiazid, patients were treated in random order with irbesartan 300, 600 and 900 mg for 2 months. End points. Urinary tubular markers at baseline and after each treatment period (ELISA), 24-h blood pressure, glomerular filtration rate (GFR, 51CrEDTA) and 24-h urine albumin excretion (UAER). Results. Fifty-two patients completed the study (41 male). Age (mean (SD)): 58(10) years and diabetes duration 13(8) years. Baseline GFR was 101(24) and UAER (geometric mean [95%CI]) 133 (103–172) mg/24 h.
With increasing doses of irbesartan (300, 600, 900 mg) u-KIM1 was reduced with 15%, 10% and 15% (p = 0.07 between 300 mg vs. baseline and no difference between doses). Patients with high u-KIM1 at baseline (above median) had a 32% reduction in u-KIM1 during treatment (p = 0.01). No significant decline in U-NGAL compared to baseline. U-LFABP increased during treatment (p < 0.01). Conclusions. Irbesartan treatment reduced levels of the tubular marker u-KIM1 in patients with type 2 diabetes and microalbuminuria. u-NGAL changed insignificantly and u-LFABP increased. More studies with longer follow up are needed to determine the role of tubular markers in monitoring treatment effect and prediction of prognosis in diabetic nephropathy.
Acknowledgements
We appreciate the help from our laboratory technicians Ulla M. Smidt, Birgitte V. Hansen, Lotte Pietraszek, Tina R. Juhl and Inge-Lise Rossing for their help collecting the data.
Declaration of interest: D. Zdunek is currently and G. Hess has been employed by Roche Diagnostics. G. Hess is a consultant to Roche Diagnostics. P. Rossing has received a lecture fee from Sanofi Aventis.