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The Food Energy/Protein Ratio Regulates the Rat Urea Cycle but Not Total Nitrogen Losses

Nitrogen balance studies have shown that a portion of the N ingested but not excreted is not accounted for. We compared several diets (standard, high-fat, high-protein, and self-selected cafeteria) to determine how diet-dependent energy sources affect nitrogen handling, i.e., the liver urea cycle. D...

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Autores principales: Oliva, Laia, Alemany, Marià, Remesar, Xavier, Fernández-López, José-Antonio
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412698/
https://www.ncbi.nlm.nih.gov/pubmed/30717282
http://dx.doi.org/10.3390/nu11020316
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author Oliva, Laia
Alemany, Marià
Remesar, Xavier
Fernández-López, José-Antonio
author_facet Oliva, Laia
Alemany, Marià
Remesar, Xavier
Fernández-López, José-Antonio
author_sort Oliva, Laia
collection PubMed
description Nitrogen balance studies have shown that a portion of the N ingested but not excreted is not accounted for. We compared several diets (standard, high-fat, high-protein, and self-selected cafeteria) to determine how diet-dependent energy sources affect nitrogen handling, i.e., the liver urea cycle. Diet components and rat homogenates were used for nitrogen, lipid, and energy analyses. Plasma urea and individual amino acids, as well as liver urea cycle enzyme activities, were determined. Despite ample differences in N intake, circulating amino acids remained practically unchanged in contrast to marked changes in plasma urea. The finding of significant correlations between circulating urea and arginine-succinate synthase and lyase activities supported their regulatory role of urea synthesis, the main N excretion pathway. The cycle operation also correlated with the food protein/energy ratio, in contraposition to total nitrogen losses and estimated balance essentially independent of dietary energy load. The different regulation mechanisms observed have potentially important nutritional consequences, hinting at nitrogen disposal mechanisms able to eliminate excess nitrogen under conditions of high availability of both energy and proteins. Their operation reduces urea synthesis to allow for a safe (albeit unknown) mechanism of N/energy excess accommodation.
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spelling pubmed-64126982019-04-09 The Food Energy/Protein Ratio Regulates the Rat Urea Cycle but Not Total Nitrogen Losses Oliva, Laia Alemany, Marià Remesar, Xavier Fernández-López, José-Antonio Nutrients Article Nitrogen balance studies have shown that a portion of the N ingested but not excreted is not accounted for. We compared several diets (standard, high-fat, high-protein, and self-selected cafeteria) to determine how diet-dependent energy sources affect nitrogen handling, i.e., the liver urea cycle. Diet components and rat homogenates were used for nitrogen, lipid, and energy analyses. Plasma urea and individual amino acids, as well as liver urea cycle enzyme activities, were determined. Despite ample differences in N intake, circulating amino acids remained practically unchanged in contrast to marked changes in plasma urea. The finding of significant correlations between circulating urea and arginine-succinate synthase and lyase activities supported their regulatory role of urea synthesis, the main N excretion pathway. The cycle operation also correlated with the food protein/energy ratio, in contraposition to total nitrogen losses and estimated balance essentially independent of dietary energy load. The different regulation mechanisms observed have potentially important nutritional consequences, hinting at nitrogen disposal mechanisms able to eliminate excess nitrogen under conditions of high availability of both energy and proteins. Their operation reduces urea synthesis to allow for a safe (albeit unknown) mechanism of N/energy excess accommodation. MDPI 2019-02-01 /pmc/articles/PMC6412698/ /pubmed/30717282 http://dx.doi.org/10.3390/nu11020316 Text en © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Oliva, Laia
Alemany, Marià
Remesar, Xavier
Fernández-López, José-Antonio
The Food Energy/Protein Ratio Regulates the Rat Urea Cycle but Not Total Nitrogen Losses
title The Food Energy/Protein Ratio Regulates the Rat Urea Cycle but Not Total Nitrogen Losses
title_full The Food Energy/Protein Ratio Regulates the Rat Urea Cycle but Not Total Nitrogen Losses
title_fullStr The Food Energy/Protein Ratio Regulates the Rat Urea Cycle but Not Total Nitrogen Losses
title_full_unstemmed The Food Energy/Protein Ratio Regulates the Rat Urea Cycle but Not Total Nitrogen Losses
title_short The Food Energy/Protein Ratio Regulates the Rat Urea Cycle but Not Total Nitrogen Losses
title_sort food energy/protein ratio regulates the rat urea cycle but not total nitrogen losses
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412698/
https://www.ncbi.nlm.nih.gov/pubmed/30717282
http://dx.doi.org/10.3390/nu11020316
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