Losartan improves renal function and pathology in obese ZSF-1 rats

Losartan, a blocker of the angiotensin II type I receptor, is an important part of the standard of care for diabetic nephropathy (DN). The obese ZSF-1 rats display many aspects of the clinical features of human Type II DN. The current study was designed to examine the treatment effects of losartan on obese ZSF-1 rats and to evaluate the impact of the onset of dosing on efficacy.

The rats (7-10 weeks) underwent a right uninephrectomy (Unx) or sham surgery. Losartan (3, 10, 30 mg/kg) was dosed 3 or 9 weeks post-Unx and continued for 12 weeks.

Treatment with losartan reduced urinary protein excretion and blood lipids (triglyceride and cholesterol) dose-dependently in both studies. The glomerular filtration rate (GFR) was significantly lower in obese ZSF-1 rats compared with those in lean rats, and losartan was efficacious against this endpoint, in particular with the earlier onset of treatment. Losartan also decreased tubulointerstitial fibrosis, and similar to GFR, earlier treatment conferred beneficial actions even at the lowest dose of 3 mg/kg. Several urinary biomarkers were elevated in the obese ZSF-1 rats, but the levels of sTNFR1, TIMP-1, L-FABP and KIM-1 were the only markers decreased by losartan.

Losartan was renoprotective in the ZSF-1 rats with DN, improving both the pathological and functional parameters of the disease. Importantly, the data also highlight the importance of treatment at earlier stages of the disease for protecting against decline in the GFR and the development of fibrosis.