Metabolomic Insights into Hypoxia-Inducible Factor Prolyl Hydroxylase Inhibitors' Kidney Protection in Contrast-Induced Nephropathy

Background: Contrast-induced nephropathy (CIN) is an acute kidney injury (AKI) associated with the use of contrast medium. We have recently reported that administration of HIF prolyl hydroxylase (HIF-PH) inhibitor, enarodustat play a protective role in rat model of CIN, suggested by improved renal dysfunction, 24-hour creatinine clearance levels and histopathological findings compared to a vehicle-treated group. HIF-PH inhibitors are thought to restore tissue homeostasis under anaerobic conditions by activating HIF1α, 2α, contributing to organ-protective effects. This study aimed to elucidate the mechanism through metabolomics analysis. Methods: Sprague-Dawley rats were assigned to sham (Nx-S), vehicle-treated CIN (Nx-V), or drug-treated CIN (Nx-E) groups. At 15 weeks, Nx-V and Nx-E underwent right nephrectomy. Enarodustat or vehicle was given at 10 mg/kg for 3 days pre-CIN induction. At 17 weeks, CIN was induced, and rats were sacrificed 2 days later for kidney metabolomic analysis. Results: CE-TOFMS and CE-QqQMS metabolomic analysis differentiated Nx-S from CIN groups (Nx-V and Nx-E). Nx-S maintained normal purine metabolism, implied by abundance of sedoheptulose 7-phosphate, hypoxanthine, and uric acid. In contrast, Nx-V and Nx-E showed elevated urea and amino acid metabolites, such as N-carbamoylaspartic acid, indicating nitrogen waste management due to kidney injury. Oxidative stress response was suggested by increased glutathione (GSH and GSSG) levels in CIN groups. PLS analysis revealed Nx-E had higher levels of metabolites involved in energy metabolism, purine metabolism, and cellular repair, like serine, aspartic acid, and hydroxyproline, suggesting enarodustat’s renoprotective effects. Additionally, reduced levels of creatinine and phosphocreatine in Nx-E implied decreased renal stress byproducts. Changes in citric acid cycle intermediates, such as citric acid and isocitric acid, in Nx-E suggested improved mitochondrial function and energy production. Conclusion: This study has clarified the biochemical changes from contrast medium and enarodustat’s modulation. Enarodustat appeared to promote a metabolic shift aiding renal recovery post-CIN. Elevated metabolites related to energy and repair in Nx-E suggested enhanced AKI protection. Reduced stress-linked metabolites supported HIF-PH inhibitors’ therapeutic potential in CIN. Funding: Government Support – Non-U.S.