Metabolic Insults Drive the Development of Glomerular Sclerosis and Proteinuria in Salt‐Sensitive Hypertensive Nephropathy

Hypertensive nephropathy causes more than one third of end stage renal cases, but its molecular mechanisms are not fully understood. Here, we performed a multi‐layered omic analysis of a well‐established animal model of hypertensive nephropathy, the Dahl salt‐sensitive (SS) rat. Specifically, we performed a time‐course untargeted and targeted metabolomics as well as quantitative phosphoproteomic and proteomic analysis of glomerular and whole kidney cortex. For this experiments three groups of age matched 8 weeks old SS rats were fed either a low salt (0.4% NaCl) or high salt (4% NaCl; 7 and 21 days of HS). Analysis of microalbuminuria, as a marker of kidney injury, revealed that SS rats had a progressive kidney damage following HS treatment (Alb/Cre ratio was 4.6 ± 0.8, 10.7 ± 1.5 and 12.2±2.0, for SS rats fed LS and HS for 7 and 21 days, respectively). Metabolomics, phosphoproteomic and proteomic analyses were performed either in the kidney cortex homogenate or pure fraction of glomeruli. Glomeruli were isolated by consecutive sieving as we previously reported. Metabolomic analysis of the glomeruli revealed a decrease in energy fuels before the onset of proteinuria, including glucose‐6‐phosphate, alpha‐Ketoglutarate, and branched chain amino acids, suggesting a wide‐spread energy depletion. In addition, proinflammatory molecules such as free fatty acids were increased before onset of proteinuria. Notably, these changes did not occur in the kidney cortex where glomeruli fraction was negligeable, suggesting glomerular vulnerability as a key event in hypertensive nephropathy. Phosphoproteomics revealed that podocyte‐specific nutrient‐sensing 5′ AMP‐activated protein kinase (AMPK), as well as regulatory‐associated protein of mTORC1 Raptor, were activated before the onset of structural damage. Structural changes as shown by complement deposition and fibrosis proteins were detectable upon onset of heavy proteinuria. Furthermore, comparative proteomics across glomerular insult models revealed that increased expression of alpha‐Ketoglutarate depleting enzymes is common in glomerular injury. Oxidative protein modifications was also detected in the extracellular matrix of the glomeruli, explaining the energy depletion. In the kidney cortex, reduced uptake of amino acids was observed among other metabolic changes. These data suggest metabolome‐driven insults in the glomeruli of the kidney that proceed the insult in the other parts of nephron. Therefore, this study provides a novel framework for the study of hypertensive nephropathy. Support or Funding Information Supported by the DFG. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .