This review highlights the current state of phenotypic mechanisms of regulation of muscle protein metabolism in animals. Since the skeletal muscle represents 40–50% of body mass in mammals it is a critical regulator of overall metabolism. Therefore, an understanding of the processes involved in the postnatal increase in muscle mass, with associated accumulation of protein, is fundamental. Throughout life, a delicate balance exists between protein synthesis and degradation that is essential for growth and normal health of humans and animals. Signaling pathways coordinate muscle protein balance. Anabolic and catabolic stimuli are integrated through the PKB/Akt-mTORC1 signaling to regulate mechanisms that control muscle protein synthesis and breakdown. At an early periods of intensive growth, muscle mass is stimulated by an increase in protein synthesis at the level of mRNA translation. Throughout the life, proteolytic processes including autophagy lysosomal system, ubiquitin proteasome pathway, calcium-dependent calpains and cysteine protease caspase enzyme cascade influence the growth of muscle mass. Several signal transmission networks direct and coordinate these processes along with quality control mechanisms to maintain protein homeostasis (proteostasis). Genetic factors, hormones, amino acids, phytoecdysteroids, and rhodanines affect the protein metabolism via signaling pathways, changing the ability and / or efficiency of muscle growth.
One of the approaches to creating biologically active additives for use in pig breeding can be the use of 20-hydroxyecdysone regulating protein metabolism in piglets. The purpose of the work is to assess the effect of 20-hydroxyecdysone on turnover of protein in piglets. The experiment was carried out on barrows (♂ Danish Yorkshire × ♀ Danish landrace) to achieve a live weight of 53-62 kg. At the age of 60 days, 2 groups of piglets were formed: control and experimental. Piglets of the experimental group were injected with 20-hydroxyecdysone at a dose of 1.6 mg / kg body weight. In piglets of the experimental group, in comparison with the control, a decrease in the excretion of nitrogen in the urine was noted (by 26.8%, P <0.05). Nitrogen deposition was higher in piglets of the experimental group by 19.0% (P <0.001) compared with the control. 20-hydroxyecdysone contributed to increased protein deposition in the body of piglets due to protein synthesizing activity. Thus, the use of 20-hydroxyecdysone in pigs increases the efficiency of using amino acids for the synthesis and deposition of proteins in the body.
In recent years, a number of new functions of branched-chain amino acids (BCAA) - leucine, valine and isoleucine - have been revealed in various states of the body in animals and humans. BCAA are involved in the regulation of the metabolism of not only proteins, but also lipids and carbohydrates, maintain the health of the mammary glands and intestines, and help in early implantation and development of embryos. BCAA increase protein synthesis and are currently considered as feed additives to improve meat productivity in pigs. New aspects of metabolic and regulatory functions of BCAA include a number of regularities: 1) insufficient or excessive levels of them in the diet enhances lipolysis; 2) BCAA, especially isoleucine, play an important role in glucose utilization by activating glucose transporters in the intestines and muscles; 3) BCAA enhance the development of the intestine, the transport of amino acids and the production of mucin; 4) BCAA are involved in the regulation of innate and adaptive immune responses. In the near future, the use of high-performance functional genomics, metabolomics, and proteomics will make it possible to more fully reveal the functions of BCAA in gene expression, protein synthesis, and metabolism regulation.
The effectiveness of using 20-hydroxyecdysone in the diet of piglets during the growing period and its effect on the formation of natural resistance, the antioxidant defense system of the body and their meat productivity were studied. The introduction of 20-hydroxyecdysone into the diet at the rate of 30 mg per kg of feed positively influenced on the bactericidal and lysozyme activity of blood serum, which in the experimental group were higher by 12,9 and 14,0%, respectively, compared with the control. The activity of superoxide dismutase and catalase enzymes in blood plasma in piglets of the experimental group was statistically significantly higher compared to the control. On the contrary, the content of malondialdehyde in blood plasma was statistically significantly lower in piglets of the experimental group compared with the control (17,1%, P≤0,01). In piglets of the experimental group, in comparison with the control, the output of muscle tissue (by 5,3%, P≤0,01), the area of the “muscle eye” (34,5%, P≤0,05) was statistically significantly higher, with less adipose tissue outlet.
One of the approaches to the creation of biologically active additives in pig nutrition can be the use of phytopreparations, in par-ticular, 20-hydroxyecdysone (20-GE), which regulates protein metabolism in piglets. The aim of this work is to assess the effect of 20-GE on the metabolism of proteins in the body and to measure their turnover in grow-ing boars. The experiment was carried out on boars (♂ Danish Yorkshire × ♀ Danish Landrace) from 60 to 120 days of age. At the age of 60 days, boars were divided into 2 groups: control and experimental, fed with feed with a content (g / kg) of crude protein 158.7, lysine 7.7, threonine 4.8, methionine 4.6, exchange energy (EE) 12.7 MJ / kg. The ratio of the first limiting amino acid lysine to EE was 61%. The boars of the experimental group were injected with 20-GE at a dose of 1.6 mg / kg of body weight. In boars of the experimental group, compared with the con-trol, there was a decrease in urinary nitrogen excretion (by 26.8%, P≤0.05). Nitrogen re-tention was higher in boars of the experi-mental group by 19.0% (P≤0.001) compared to the control. The results of studies on pro-tein turnover obtained using a stable isotope indicate that the anabolic effect of 20-GE isdetermined by an increase in the rate of pro-tein synthesis at the same rates of their deg-radation, nitrogen flow against the back-ground of a decrease in its endogenous loss-es. 20-GE by activating a signal through protein kinase B provides an increase in bio-synthetic processes at the stage of transla-tion. It was concluded that the use of 20-GE in boars cultivation increases the efficiency of using amino acids for the synthesis and deposition of proteins in the body.
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