Reduction in dietary lysine increases muscle free amino acids through changes in protein metabolism in chickens

Abstract

Taste is crucial to meat quality, and free Glu is an important taste-active component in meat. Our recent study showed that the short-term feeding of a low-Lys diet increases the concentration of free Glu and other free amino acids in chicken muscle and improves its taste. Here, we investigated the mechanisms by which the feeding of a low-Lys diet increases free Glu in chicken muscle. Two groups (n = 10 per group) of 28-day-old female Ross strain broiler chickens were fed diets with a graded Lys content of 90% or 100% of the recommended Lys requirement (according to National Research Council [1994] guidelines) for 10 D. Free amino acid concentrations and the mRNA abundance of protein metabolism–related genes were measured in breast muscle, and breast muscle metabolome analysis was conducted. Free Glu in muscle was increased by 51.8% in the Lys 90% group compared with the Lys 100% group ( P < 0.01). Free threonine, glutamine, glycine, valine, isoleucine, leucine, tyrosine, phenylalanine, histidine, and 3-methyl-histidine concentrations in breast muscle were also increased in the Lys 90% group ( P < 0.05). Metabolome analysis also showed that free amino acids were increased in the Lys 90% group. The mRNA abundance of μ-calpain, caspase-3, and 20S proteasome C2 subunit were increased in the Lys 90% group ( P < 0.05). Moreover, the free Glu concentration in muscle was correlated with mRNA abundance of μ-calpain ( r = 0.74, P < 0.01), caspase 3 ( r = 0.69, P < 0.01), 20S proteasome C2 subunit ( r = 0.65, P < 0.01), and cathepsin B ( r = 0.52, P < 0.05). Our study suggests that the feeding of a low-Lys diet to chickens increased the free Glu content of breast muscle by promoting protein degradation.

Lysine Depletion during Different Feeding Phases: Effects on Growth Performances and Meat Quality of Broiler Chickens

“…Overall, the increased hypoxanthine content coupled with the slightly reduced inosine level observed in broilers fed low Lys diets suggests an altered energy metabolism within these muscles. This hypothesis is further corroborated by the findings obtained by Watanabe et al [ 52 ], who speculated an increased ATP synthesis as a response towards dietary Lys restriction. This suggests an increased energy requirement in the pectoral muscles belonging to Lys-restricted birds and further supports the above-mentioned hypothesis of a reduced protein synthesis taking place within these muscles as it is generally held that protein metabolism can also be affected by the energetic status of the muscle itself [ 54 ].…”

“…In addition, as a higher amount of proline was previously associated to an enhanced protein synthesis [ 51 ], the reduced content of this amino acid found in Lys-restricted groups may suggest an inhibited protein anabolism. Accordingly, a previous study highlighted a change in protein metabolism, mainly catabolism, when a reduction of dietary Lys was implemented in broiler chickens [ 52 ]. In addition, together with hydroxyproline, glycine and proline account for more than 50% of the total amino acids composing collagen [ 53 ].…”

Understanding metabolic phenomena accompanying high levels of yeast in broiler chicken diets and resulting carcass weight and meat quality changes

“…Myofibrillar protein degradation in the chicken muscle is rather plausible keeping in mind a trend in loss of appetite and a small numerical increase in the mortality rate for chicken fed yeast-containing diets ( Cruz et al., 2020 ), leading to reduced cold carcass weight for CJ30 compared with the controls ( Table 4 ). In addition, the content of protein and amino acids in the chicken diet dictates free amino acid content in skeletal muscles ( Watanabe et al., 2020 ). Therefore, even at the lowest yeast inclusion level (CJ10) protein metabolism in the chicken muscle may be affected.…”

Increased Dietary Inclusion Levels of Lysine Are More Effective than Arginine in Supporting the Functional Status of the Gut in Growing Turkeys

“…The regulatory effect of Lys in reducing substrates available for the synthesis of putrefactive SCFA could be partially explained by the fact that Lys is the most limiting AA in turkeys, and even excessive levels of dietary Lys are well tolerated in terms of SCFA production in the cecal environment. In contrast, an insufficient supply of dietary Lys, below the chickens’ requirements, was reported to induce protein degradation to satisfy muscle requirements for protein synthesis, which suggests that the regulatory system could preferentially use Lys and make it available for cecal bacteria due to its key role in protein synthesis [ 41 ]. However, it should be noted that the SCFA profile was not disrupted in terms of the contribution of major SCFA, including C2, C3 and C4, which are formed in the greatest abundance in the ceca of turkeys [ 42 ].…”