P0104THERAPEUTIC METFORMIN TREATMENT IS ABLE TO HALT THE PROGRESSION OF CHRONIC KIDNEY DISEASE IN RATS

Abstract

Abstract Background and Aims Metformin, a biguanide drug, is the first-line oral antidiabetic agent used by 200 million patients suffering from type 2 diabetes mellitus. In the last decades, it has become clear that metformin exerts benign pleiotropic actions beyond its prescribed use and emerging data show protective effects against different age-related diseases. Additionally, recent preclinical and clinical data point towards a beneficial impact of metformin on the kidney. Current treatment strategies for chronic kidney disease (CKD) mainly focus on controlling important risk factors, such as high blood pressure and diabetes. To date, effective treatment directly targeting the kidney is lacking. Here, the ability of metformin to attenuate progression of already established CKD, independent from its effects on diabetes, was investigated. Method A rat model of adenine-induced CKD (n=64) was used. Metformin (200 mg/kg) or vehicle (1% carboxymethylcellulose) treatment, by daily oral gavage (7 days/week), was initiated after 4 and 5 weeks of adenine (0.25%) administration; i.e. after CKD had developed. Treatment was continued during 4 weeks until the end of the study (i.e. week 8 and 9, respectively). A constant dose volume of 10 mL/kg was used. The effect of metformin on renal function and histopathology was studied. Results Serum creatinine levels dramatically rose in vehicle-treated CKD rats: from 0.6 ± 0.1 mg/dL (week 0) to 1.3 ± 0.2 mg/dL (week 4) and 2.6 ± 1.2 mg/dL (week 5) and further to 5.7 ± 0.6 mg/dL (week 8) and 4.8 ± 1.1 mg/dL (week 9). Metformin treatment, which started after 4 and 5 weeks, prevented almost completely further increases in serum creatinine levels after 8 (2.0 ± 0.5 mg/dL) and 9 (2.9 ± 0.5 mg/dL) weeks compared to vehicle-treated CKD rats (p<0.05). The calculation of creatinine clearance confirmed these results. Histological examination of periodic acid–Schiff (PAS)-stained renal sections revealed less tubular dilation, epithelial flattening, brush border loss and, basement membrane thickening in metformin-treated CKD rats in comparison to vehicle-treated animals. The renal tubulointerstitial area percentage was significantly lower in metformin-treated CKD rats, as compared to vehicle treatment (from 35% and 41% tubulointerstitial area after 4 and 5 weeks, respectively, to 50% and 53% in vehicle-treated CKD rats and 34% and 41% in metformin-treated CKD rats after 8 and 9 weeks, respectively). Leukocyte common antigen (CD45)-staining revealed significantly less infiltration of inflammatory cells in metformin-treated CKD rats after 9 weeks (8%) as compared to the vehicle-treated CKD rats (12%). Semiquantitation of proliferating cell nuclear antigen (PCNA)-staining at 9 weeks showed that the amount of tubules containing more than 50% proliferating cells were increased, whereas PCNA-negative tubules were decreased in metformin-treated CKD rats compared to vehicle-treated CKD rats (p<0.05) . Conclusion Therapeutic metformin treatment is able to attenuate the progression of pre-existing adenine-induced CKD in rats.