Plasma and Urinary Amino Acid-Derived Catabolites as Potential Biomarkers of Protein and Amino Acid Deficiency in Rats.

Joanna Moro,Jean-Charles Martin,Thierry Berton,Catherine Tardivel,Delphine Jouan-Rimbaud Bouveresse,Claire Gaudichon,Daniel Tomé,Nadezda Khodorova,Dalila Azzout-Marniche

doi:10.3390/nu13051567

Abstract

Objective: Dietary intakes must cover protein and essential amino acid (EAA) requirements. For this purpose, different methods have been developed such as the nitrogen balance method, factorial method, or AA tracer studies. However, these methods are either invasive or imprecise, and the Food and Agriculture Organization of the United Nations (FAO, 2013) recommends new methods and, in particular, metabolomics. The aim of this study is to determine total protein/EAA requirement in the plasma and urine of growing rats. Methods: 36 weanling rats were fed with diets containing 3, 5, 8, 12, 15, and 20% protein for 3 weeks. During experimentation, urine was collected using metabolic cages, and blood from the portal vein and vena was taken at the end of the experiment. Metabolomics analyses were performed using LC-MS, and the data were analyzed with a multivariate analysis model, partial least Squares (PLS) regression, and independent component-discriminant analysis (ICDA). Each discriminant metabolite identified by PLS or ICDA was tested by one-way ANOVA to evaluate the effect of diet. Results: PLS and ICDA allowed us to identify discriminating metabolites between different diet groups. Protein deficiency led to an increase in the AA catabolism enzyme systems inducing the production of breakdown metabolites in the plasma and urine. Conclusion: These results indicate that metabolites are specific for the state of EAA deficiency and sufficiency. Some types of biomarkers such as AA degradation metabolites appear to be specific candidates for protein/EAA requirement.

Highlights

The quality and the quantity of protein intake has become a sensitive issue in the context of current debates on both the increase in the world population, the problem of child undernutrition, and the need to rebalance animal and vegetable food sources
This study addressed the consequences of three weeks of protein restriction on the plasma and 24-h urine biomarkers of protein deficiency
The portal vein being the reflection of food intake, the low protein diet led to a decrease in essential amino acid (EAA) [18,19], and the same profile was found in the vena cava

Summary

Introduction

The quality and the quantity of protein intake has become a sensitive issue in the context of current debates on both the increase in the world population, the problem of child undernutrition, and the need to rebalance animal and vegetable food sources. Every day there is a renewal of the protein pool by proteolysis and proteosynthesis estimated at 250–300 g per day (2% on average) [1]. The maintenance of tissues and physiological functions in adults and the support of growth in the young require a balance of the body free AA pool, renewed by food intake and body proteolysis. 20 AA are called “proteinogenic”, and among these, 9AA are considered essential (EAA), because their carbon skeleton is not or poorly synthesized in the body and they must be provided by food. Protein synthesis depends critically on a balanced intake of dietary AAs, and EAA, as protein can only be synthesized if all the constituting AAs are simultaneously available in adequate quantity

Methods

Results

Conclusion