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Cell Physiology
Published in Wei-Shou Hu, Cell Culture Bioprocess Engineering, 2020
Glutamine is a major amino acid constituent of cellular proteins. Additionally, its amide group supplies the nitrogen in the synthesis of purine and pyrimidine bases, which are the backbone of nucleic acids. However, the amount of glutamine consumed by cells far exceeds what is needed for synthesizing cellular components.
Benefits of β-hydroxy-β-methylbutyrate supplementation in trained and untrained individuals
Published in Research in Sports Medicine, 2019
Yftach Gepner, Alyssa N. Varanoske, David Boffey, Jay R. Hoffman
A recent area of concern regarding HMB supplementation is that the beneficial effects of reducing proteolysis in skeletal muscle incited by HMB supplementation may result in adverse effects in other body tissues. For example, the decrease in protein breakdown after HMB supplementation results in a decrease in the concentration of free amino acids in the blood, subsequently reducing their availability to visceral organs (Holecek, 2017). One investigation reported a decrease in plasma glutamine concentration after an acute administration of HMB (100 mg· kgBW−1) in rats (Holecek, Muthny, Kovarik, & Sispera, 2009). Glutamine is an amino acid that is essential for maintaining proper gut and immune cell function, and reductions in plasma glutamine may impair skeletal muscle protein synthesis (Elia & Lunn, 1997; Holecek & Sispera, 2014; Newsholme, 1996). Low plasma glutamine concentrations may be experienced in individuals exhibiting symptoms of critical illness (Holecek & Sispera, 2014; Keast, Arstein, Harper, Fry, & Morton, 1995). HMB does however increase protein synthesis in muscle (Wilkinson et al., 2013) and therefore, glutamine must not be limiting. As these data again are derived from rodent studies, more research in humans on the overall balance of amino acid metabolism with HMB is warranted.