Effects of methionine on muscle protein synthesis and degradation pathways in broilers

Abstract

This study investigated the hypothesis that supplementation of methionine (Met) to broiler diets increases muscle growth due to regulation of molecular pathways related to protein synthesis and degradation depending on the Met source. Day‐old male Cobb‐500 broilers (n = 240) were phase‐fed three different wheat–soya bean meal‐based basal diets during days 1–10, 11–21 and 22–35. Basal diets (Met‐ group, Met + Cys concentration 15% below NRC recommendations) were supplemented with 0.10% or 0.40% Met either as DL‐Met (DLM) or DL‐2‐hydroxy‐4‐(methylthio) butanoic acid (DL‐HMTBA) (equimolar comparison). Breast muscle weights were lower in the Met‐ group compared to all Met‐supplemented groups and were lower in broilers supplemented with 0.10% of DL‐HMTBA compared to the other groups fed Met‐supplemented diets. However, the expression of genes or relative phosphorylation and thus activation state of proteins involved in the somatotropic axis, the mammalian target of rapamycin (mTOR) pathway of protein synthesis, the ubiquitin–proteasome pathway (UPP) and autophagy–lysosomal pathway of protein degradation, the GCN2/eIF2a pathway involved in the inhibition of protein synthesis and in the myostatin–Smad2/3 pathway involved in myogenesis were not affected by Met source. Feeding diets with suboptimum Met + Cys concentrations, however, decreased expression of GHR and IGF1 in liver and muscle and increased that of MURF1 involved in the UPP in the broiler's muscle at day 10 and 21, while that of FOXO and atrogin‐1 and FOXO phosphorylation remained unaffected. Additionally, suboptimum dietary Met concentrations increased expression of the autophagy‐related genes ATG5 and BECN1 at day 35. Met supplementation neither affected gene expression nor phosphorylation of proteins involved in the GNC2/eIF2a and mTOR pathways. These data indicate that protein synthesis was not affected on the molecular level, while protein degradation was marginally affected by dietary Met dosage.

Effect of dietary digestible sulphur amino acids level on growth performance, blood metabolites and liver functional enzymes of broilers 1–11 days of age

“…However, recent insights have highlighted its action as a signal molecule in regulating protein metabolism (Majdeddin et al 2019). In fast-growing broilers, Met supplementation promotes anabolism and reduces catabolic processes, favouring muscle protein synthesis (Zeitz et al 2019). One of the reasons for the reducing serum TP and Alb concentration in the birds fed a diet with lower DSAAs level in our experiment may be related to its decomposition for supplying AA requirements.…”

Digestible methionine levels for white-egg layer pullets from 7 to 12 weeks of age

“…Handique, Saikia, Dowarah, Saikia, and Tamuly (2019) observed that higher serum protein values may be attributed to higher crude protein metabolism with higher nitrogen retention due to adequate dietary amino acid balance, resulting in increased absorption and circulation of amino acids in the blood. With the increased availability of amino acids in the poultry organism, through the optimal level of methionine in the diet, it is expected that the anabolism process will be maximized, while a reduction in the catabolic process, favoring protein synthesis in different tissues body (Zeitz et al, 2019).…”

Estimation of digestible sulphur amino acids requirements for growth performance and immune responses to Newcastle disease and avian influenza vaccination in broilers

“…The anabolic effect of Met is partly due to increased substrate supply at the sites of protein synthesis; however, recent insights have highlighted its action as a signal molecule in the regulation of protein metabolism (Majdeddin et al 2019). Other studies have confirmed that, in fast-growing chickens, supplementary Met promotes anabolism and reduces catabolic processes, favouring muscle protein synthesis (Vesco and Gasparino 2013 ;Wen et al 2017), though others did not find any conclusive evidence (Zeitz et al 2019) .…”