Oral Ketone β-Hydroxybutyrate Supplement Retards the Loss of GFR in Alport Mice on Dual Renin-Angiotensin System/ Sodium-Glucose Transporter 2 Blockade

Background: Several studies suggest that dietary beta hydroxybutyrate supplementation delays the progression of chronic kidney disease (CKD) by suppressing inflammation and fibrosis. We hypothesized that the oral supplementation with the beta-hydroxybutyrate (BHB) precursor 1,3-butanediol in addition to inhibitors of the renin-angiotensin system (RAS) and sodium-glucose transporter (SGLT)2 would be superior to dual RAS/SGLT2 blockade alone in attenuating the loss of glomerular filtration rate in Col4a3-deficient mice with Alport nephropathy, a spontaneous model of progressive CKD. Methods: We performed a placebo-controlled study in Col4a3-deficient mice with Alport nephropathy. Treatment was initiated at a late stage of the disease at the age of six weeks. Mice were fed food admixes of 10 μg/g ramipril plus 30 μg/g empagliflozin with or without addition of 0,04g/g 1,3-butanediol (concentration per gram of bodyweight). The mice were monitored daily and sacrificed upon reaching renal failure. The glomerular filtration rate (GFR) was measured at the start of the treatment and after one and four weeks. Results: The addition of beta hydroxybutyrate significantly attenuated the loss of glomerular filtration rate beyond the effect of dual RAS/SGLT2 blockade. The mean glomerular filtration rate after four weeks of treatment was 1.4±5.0 μl/min (vehicle), 61.3±51.1 μl/min (RASi + SGLT2i), and 138.9±68.5 μl/min (RASi + SGLT2i + 1,3-butanediol). No additional effects on lifespan could be observed. Kidney RNA sequencing revealed significant protective effects on inflammation when adding the beta hydroxybutyrate precursor 1,3-butanediol to RAS/SGLT2 inhibition. In histopathology, antifibrotic effects were seen upon beta hydroxybutyrate addition. Conclusion: The results in mice suggest that beta hydroxybutyrate supplementation improves the GFR in Alport syndrome by suppressing inflammation and fibrosis. However, the effects did not lead to a significant increase in lifespan. Furthermore, the observed effects stay behind the effects of finerenone as a combination partner, which was tested earlier in the same mouse model. Comparison in kidneys of Col4a3-/- mice fed with Ramipril/Empagliflozin (Data available with GSM7073816) vs Ramipril/Empagliflozin/1,3-butanediol regarding RNA expression of significantly altered canonical pathways. This study includes re-analysis of publicly available samples: GSM7073825, GSM7073826 and GSM7073827. Data for these samples are included in the files: GSM7073825: counts_without_BHB_1.csv, Col4a3_KO_Ram_Empa_1.csv GSM7073826: counts_without_BHB_2.csv, Col4a3_KO_Ram_Empa_2.csv GSM7073827: counts_without_BHB_3.csv, Col4a3_KO_Ram_Empa_3.csv