Drug testing for residual progression of diabetic kidney disease in mice beyond therapy with metformin, ramipril, and empagliflozin

Abstract

Background Progression of CKD in type 2 diabetes, despite dual inhibition of sodium-glucose transporter-2 and the renin-angiotensin system, remains a concern. Bromoindirubin-39-oxime (BIO), previously reported to promote podocyte survival and regeneration, is a candidate additional drug to elicit renoprotective effects beyond therapy with metformin, ramipril, and empagliflozin (MRE). Evaluating a drug with standard therapeutics more closely mimics the clinical setting than evaluating the drug alone. Methods Uninephrectomized BKS-Lepr2/2 (db/db) mice treated with or without MRE served as a model of progressive CKD in type 2 diabetes. Mice on or off MRE were randomized to only 4 weeks of add-on BIO or vehicle. The primary end point was slope of GFR (DGFR). Results Four weeks of MRE treatment alone did not affect DGFR, but significantly attenuated hyperglycemia, albuminuria, and glomerulosclerosis and increased podocyte filtration slit density, as assessed by STED super-resolution microscopy upon tissue clearing. BIO alone improved albuminuria, podocyte density in superficial and juxtamedullary nephrons, and podocyte filtration slit density. MRE1BIO combination therapy had additive protective effects on DGFR, glomerulosclerosis, podocyte density in juxtamedullary nephrons, and filtration slit density. Conclusions Add-on treatment with BIO for only 4 weeks attenuates progression of CKD beyond MRE therapy in mice with type 2 diabetes. Additional drug combinations may help to further delay ESKD in type 2 diabetes.