Kidney Week

Abstract: TH-PO562

Isotope-Guided Metabolomics Dissects Arginine Metabolism in Proteinuria

Session Information

• Glomerular Diseases: Omics, Biomarkers, and Tools
  October 24, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology

Authors

• Chrysopoulou, Maria, Aarhus Universitet Institut for Biomedicin, Aarhus, Midtjylland, Denmark

Maria Chrysopoulou, MS, MSc

• Bleich, Markus, Christian-Albrechts-Universitat zu Kiel, Kiel, Schleswig-Holstein, Germany

Markus Bleich, MD, PhD

• Himmerkus, Nina, Christian-Albrechts-Universitat zu Kiel, Kiel, Schleswig-Holstein, Germany

Nina Himmerkus, MD

• Rinschen, Markus M., Aarhus Universitet Institut for Biomedicin, Aarhus, Denmark

Markus M. Rinschen, MD

Group or Team Name

• Laboratory of Kidney Omics and Metabolism.

Background

Proteinuria is a direct outcome of kidney glomerulus injury and an independent risk factor for cardiovascular disease (CVD). Arginine (Arg) metabolism links protein metabolism to renal function and CVD through urea excretion and nitric oxide generation. Due to the many metabolic fates, signals related to Arg metabolism are uninterpretable and its role in proteinuric kidney disease is not completely understood. The aim of this study is to investigate arginine's metabolic fate and interorgan communication in the healthy kidney and proteinuric kidney disease in a systemic way by comprehensive metabolomics and proteomics approaches.

Methods

Compound-heterozygous Pod^R231Q/A286V is a mouse model of human hereditary nephrotic syndrome developing progressive proteinuria and leading to focal segmental glomerulosclerosis. Ex vivo, isolated and dissected nephron segments from healthy mice (n=4) and isolated tubule and glomeruli suspension from healthy and Pod^R231Q/A286V mice, (n=8), were incubated with ¹³C₆-Arg for 60 minutes. Extracted metabolites were analyzed with UHPLC/QQQ-based mass spectrometry targeting Arg-related metabolic pathways. In vivo, healthy and Pod^R231Q/A286V mice (n=21) were fed with normal and stable isotope-labeled Arg diet for 2 weeks. Metabolites and proteins extracted from 19 metabolically active organs, urine, and plasma were analyzed accordingly.

Results

Ex vivo, Arg-derived glutamate, proline and agmatine were detected along the whole nephron, whereas ¹³C₅-ornithine and ¹³C₁-guanidineacetic acid were mostly formed in the proximal nephron segments. The same Arg metabolic pathways were also confirmed in the tubules and glomeruli suspensions. Proteinuria did not alter Arg metabolism in glomeruli, however, in proteinuric renal tubules, ¹³C₅-glutamate, ¹³C₅-proline and ¹³C₁-guanidineacetic acid were increased. In vivo, in proteinuric animals, Arg was accumulated in the liver. Even though total urea levels showed systemic accumulation in all investigated organs and lower excretion in the urine, the relative abundance of newly synthesized urea was decreased. Arg-derived glutamate was increased mostly in the kidneys, demonstrating significant metabolic rewiring across organ borders.

Conclusion

In proteinuria, arginine metabolism shifts from the liver-focused urea formation towards a more global utilization of arginine in the kidney.