A concept of dietary dipeptides: a step to resolve the problem of amino acid availability in the early life of vertebrates

Abstract

SUMMARY The premise that a dietary dipeptide approach will improve the understanding of amino acid utilization in the fastest-growing vertebrate, the teleost fish, was tested by examining the muscle free amino acid (FAA) pool and enzyme activities, in concert with growth response, when dietary amino acids were provided in free, dipeptide or protein molecular forms. We present the first evidence in fish that, in response to a synthetic dipeptide diet,muscle FAA varies as a result of both growth rate and amino acid availability of specific peptides. We demonstrate significantly diminished muscle indispensable FAA (3–10-fold) in rainbow trout alevins fed a dipeptide-based diet compared with a protein-based diet. The dipeptide-based diet did not contain proline, resulting in 10–27-fold less muscle free proline and hydroxyproline in alevins. The response of alevins fed FAA-based or peptide-based diets can be indicative of collagen turnover (Hyp/Pro ratio)and showed significant differences between dietary treatments. Pyrroline-5-carboxylate (P5C) reductase activity was detected, suggesting that P5C may ameliorate proline deficiency, but synthesis from glutamate could not maintain free proline levels in muscle. This finding will provide an impetus to test whether proline is conditionally indispensable in young fish, as in mammals and birds. This study shows that amino acids given entirely as dipeptides can sustain fish growth, result in muscle FAA and enzyme responses in line with dietary levels and identify growth-limiting amino acids. The understanding of these factors necessitates a diet formulation that will improve the accuracy of determining amino acid requirements in the early life stages of vertebrates.

Supplementations of dl‐Methionine and Methionine Dipeptide in Diets are Effective for the Development and Growth of Larvae and Juvenile Red Sea Bream, Pagrus major

“…In contrast, juvenile rainbow trout Oncorhynchus mykiss growth experiment (Terjesen et al 2006) showed that amino acid in dipeptide form was efficiently absorbed than an identical amino acid in free form that resulted in higher accumulation rate and postprandial peak time for muscular free amino acid. This may indicate different metabolic handling of amino acids and availability for protein synthesis, which is translated to better growth rate (Dabrowski et al 2005). Juvenile fish study indicated a faster free amino acid absorption compared with protein bound amino acids for carp, Cyprinus carpio (Plakas and Katayama 1981), rainbow trout (Cowey and Walton 1988) and Atlantic cod, Gadus morhua (Berge et al 1994).…”

Postprandial changes in plasma free amino acid levels obtained simultaneously from the hepatic portal vein and the dorsal aorta in rainbow trout (Oncorhynchus mykiss)

“…Thus, if the number of transporters is limited, the uptake profile will have a longer duration. By contrast, AAs absorbed via passive carriers and diffusion will be concentration dependent, and small peptides are known to be absorbed more rapidly (Steinhardt and Adibi, 1986;Matthews, 2000;Bogé et al, 2002;Dabrowski et al, 2005). …”

The differences in postprandial free amino acid concentrations and the gene expression of PepT1 and amino acid transporters after fishmeal partial replacement by meat and bone meal in juvenile turbot (Scophthalmus maximus L.)

“…PepT1 is one of key intestinal transporters, which play an important role in regulating oligopeptide transportation (Daniel 2004;Terova, Robaina, Izquierdo, Cattaneo, Molinari, Bernardini & Saroglia 2013). Accumulating evidence demonstrates that PepT1 and diverse AA transporters may have a major role in regulating body AA homoeostasis (Dabrowski, Terjesen, Zhang, Phang & Lee 2005;Bakke, Jordal, G omez-Requeni, Verri, Kousoulaki, Aksnes & Rønnestad 2010;Xu, He, Mai, Zhou, Xu & Song 2016b). Large amounts of peptides and amino acids were transported by the PepT1 and AA transporters across cell membrane, providing essential nutrients for growth and metabolism (Poncet & Taylor 2013).…”