Abstract P108: Compensatory Changes In Metabolomic Profiles In The Kidney Of Sprague-dawley Rats Fed A High-salt Diet.

Abstract

Goal: The effects of a high salt diet on renal cortical ( Cx ) and outer medulla ( OM ) tissue metabolism of normal age matched male Sprague-Dawley rats (SD; 15-16 wk age; n-5) was determined with rats fed 0.4% NaCl (LS) and after switching to 4.0% NaCl (HS) diet at day HS14 and HS21. Methods: From snap-frozen Cx and OM tissue, novel analytical approaches were developed and applied at the JAX lab to determine metabolic profiles using 4 modes (C18+/- and HILIC+/-) using a Thermo Q-Exactive Orbitrap coupled to a Vanquish UPLC system. Results: Kidney weight was increased (P<0.05) by 0.5 mgkw/gbw at HS14 from from LS level of 3.2±0.1 mgkw/gbw and remained constant at HS21. A principal component analysis (PCA) of each mode found distinct separation of metabolites in both the Cx and OM comparing LS to HS14, and HS21. Of 2085 named compounds identified in Cx and 1886 in OM, the Metaboanalyst database found 968 (Cx) and 861 (OM) with 285 (Cx) and 284 (OM) changed (P<0.05) at HS14. At day HS21, 438 were changed (P<0.05) in Cx and 349 in OM compared to LS. A pathway enrichment analysis (SMPDB) of those metabolites was carried out. Expressed as the enrichment ratio (ER; observed hits/expected hits) found enrichment of Arachidonic acid metabolism pathway at HS13 (ER=2.7), consistent with observed increases (P<0.05) of L-glutamic acid, arachidonic acid and thromboxane B2. Increased levels of phosphoenalpyruvic acid and glucose 1-phosphate were observed (p<0.05), consistent with elevated glycolysis and gluconeogenesis, not observed at HS21. In the OM at HS14, the “Tyrosine metabolism” (ER:1.9), “Lysine degradation” (ER:2.2) and “Beta-alanine metabolism” (ER:1.9) pathways were enriched (P<0.05). Lysine, tyrosine and glutamate levels were reduced (P<0.05) indicating increased amino acid utilization. Also found were reductions of glucose-6-phosphate, pyruvate and alpha-ketoglutarate (P<0.05) indicating reduced glycolysis and TCA activity. At day HS21 these changes were generally not significant in either Cx or OM. Conclusion: Kidney weight increased after 2 wks of HS diet which was associated with increased amino acid metabolism and reduced glycolysis in OM (e.g. anabolic profile). Those metabolites (above) then returned to levels observed on a LS diet as kidney weight stabilized.