[Frontiers in Bioscience S3, 1298-1307, June 1, 2011]

Biomarkers for optimal requirements of amino acids by animals and humans

Gang Lin1, Chuang Liu1, Taiji Wang1, Guoyao Wu1,2, Shiyan Qiao1, Defa Li1, Junjun Wang1

1State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing, China 100193, 2Department of Animal Science, Texas A and M University, College Station, TX, 77843

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Some concepts about amino acid requirements
3.1. Classification of amino acids
3.2. Amino acid balance and imbalance
4. Requirements of amino acids by animals and humans 4.1. Definition of amino acid requirements
4.2. Factors affecting amino acid requirements
4.3. Methodology of estimating amino acid requirements
5. Biomarkers as potential functional parameters for amino acid requirements by animals and humans
5.1. Biomarkers for the metabolism of amino acids
5.2. Biomarkers for amino acid requirements under different conditions
5.3. Biomarkers for recommendation of amino acid requirements
6. Summary and future directions
7. Acknowledgements
8. References

1. ABSTRACT

Amino acids are building blocks of proteins and key regulators of nutrient metabolism in cells. However, excessive intake of amino acids can be toxic to the body. Therefore, it is important to precisely determine amino acid requirements by organisms. To date, none of the methods is completely satisfactory to generate comprehensive data on amino acid requirements of animals or humans. Because of many influencing factors, amino acid requirements remain a complex and controversial issue in nutrition that warrants further investigations. Benefiting from the rapid advances in the emerging omics technologies and bioinformatics, biomarker discovery shows great potential in obtaining in-depth understanding of regulatory networks in protein metabolism. This review summarizes the current approaches to assess amino acid requirements of animals and humans, as well as the recent development of biomarkers as potentially functional parameters for recommending requirements of individual amino acids in health and disease. Identification of biomarkers in plasma or serum, which is a noninvasive approach, holds great promise in rapidly advancing the field of protein nutrition.