Protein synthesis regulation by leucine

Abstract

In vivo and in vitro studies have demonstrated that high protein diets affect both protein synthesis and regulation of several cellular processes. The role of amino acids as substrate for protein synthesis has been established in the literature. However, the mechanism by which these amino acids modulate transcription and regulate the mRNA translation via mTOR-dependent signaling pathway has yet to be fully determined. It has been verified that mTOR is a protein responsible for activating a cascade of biochemical intracellular events which result in the activation of the protein translation process. Of the aminoacids, leucine is the most effective in stimulating protein synthesis and reducing proteolysis. Therefore, it promotes a positive nitrogen balance, possibly by favoring the activation of this protein. This amino acid also directly and indirectly stimulates the synthesis and secretion of insulin, enhancing its anabolic cellular effects. Therefore, this review aimed to identify the role of leucine in protein synthesis modulation and to discuss the metabolic aspects related to this aminoacid. Uniterms:Leucine. Protein synthesis. Transcription Factors. mTOR. Translation Protein.Estudos in vivo e in vitro verificaram que dietas hiperprotéicas influenciam a síntese protéica e regulam vários processos celulares. O papel dos aminoácidos como substrato para a síntese de proteínas já está bem evidenciado na literatura, porém as formas como esses aminoácidos modulam a etapa da transcrição e regulam a tradução do RNAm, pela via de sinalização dependente da mTOR, ainda não estão totalmente esclarecidas. Tem-se verificado que a mTOR é uma proteína responsável por ativar uma cascata de eventos bioquímicos intracelulares que culminam na ativação do processo de tradução protéica. Dentre todos os aminoácidos, a leucina é a mais eficaz em estimular a síntese protéica, reduzir a proteólise e, portanto, favorecer o balanço nitrogenado positivo, possivelmente por favorecer a ativação desta proteína. Além disso, este aminoácido estimula direta e indiretamente a síntese e a secreção de insulina, e, assim, aumenta as propriedades anabólicas celulares. Nesse sentido, a presente revisão tem como objetivo identificar o papel da leucina na modulação da síntese protéica e abordar aspectos metabólicos relacionados a este aminoácido.Unitermos: Leucina. Síntese protéica. Fator de transcrição. mTOR. Tradução de proteínas. INTRODUCTIONProtein synthesis in tissue is rapidly stimulated after nutrient consumption. Insulin and aminoacids stimulate protein anabolism, acting in a posterior step of gene transcription, i.e., on protein translation. However, the mechanism by which the aminoacids stimulate protein translation has yet to be fully determined (Proud, 2002).Some studies have verified that high-protein diets stimulate protein synthesis. Some of the benefits promoted by this diet on body composition can be attributed to high consumption of branched-chain aminoacids (BCAA), which include the aminoacids leucine, valine and isoleucine (Donato...

Leucine markedly regulates pancreatic exocrine secretion in goats

“…In summary, the different results from the short‐term and long‐term experiments indicate that the regulations of leucine to pancreatic exocrine secretion depended on the sustaining time of infusion. A number of previous studies have shown that leucine stimulated protein synthesis through the mTOR signalling pathway immediately (Vianna et al., ). However, long‐term leucine supplementation did not increase muscle mass in healthy elderly men (Verhoeven et al., ; Leenders et al., ).…”

“…It has been well verified that the increase in amino acids concentration in diets can stimulate muscle (Dreyer et al., ) and milk (Burgos et al., ) protein synthesis. Among the amino acids, leucine is the most effective member in stimulating protein synthesis by mTOR networks in different organs (Kim, ; Vianna et al., ), including pancreas (Sans et al., ). Digestive enzyme is also protein and makes up 90% of pancreatic protein (Steer, ).…”

“…Amino acids, especially leucine, rapidly stimulate protein synthesis through the mTOR signalling pathway (Kim, ; Vianna et al., ). However, long‐term leucine supplementation does not increase muscle mass in healthy elderly men (Verhoeven et al., ; Leenders et al., ).…”

Regulation of pancreatic exocrine secretion in goats: differential effects of short‐ and long‐term duodenal phenylalanine treatment

“…In addition, although the effects of acute treatment with phenylalanine on PES in non‐ruminants (Owyang et al., 1986; Riepl et al., 1996) have been determined, the studies on the clinical benefits of prolonged phenylalanine supplementation are lacking. Amino acids, especially leucine, rapidly stimulate protein synthesis through the mTOR signalling pathway (Kim, 2009; Vianna et al., 2010). However, long‐term leucine supplementation does not increase muscle mass in healthy elderly men (Verhoeven et al., 2009; Leenders et al., 2011).…”

Branched chain amino acids in feeding pigs: Review

“…Alguns benefícios promovidos pela dieta são atribuídos ao alto consumo dos ACR (Vianna et al, 2010), uma vez que estes AA representam 35% dos AA essenciais presentes na proteína do músculo (Riazi et al, 2003). Pelo fato dos ACR serem metabolizados primeiramente no músculo esquelético, será fonte de energia e substratos para a síntese proteica muscular, sua suplementação poderia influenciar o processo de anabolismo proteico.…”