Cystic fibrosis influence
J Cystic Fibrosis. 2013. Dietary essential amino acids are highly anabolic in pediatric patients with cystic fibrosis. Current nutritional approaches have been partially successful in Cystic Fibrosis (CF). Essential amino acids mixtures with high Leucine levels (EAA) have anabolic properties in catabolic conditions, however data in CF are lacking. On two days according a randomized crossover design, 15 pediatric CF patients ingested g EAA versus mixture of total amino acids as present in whey. Whole body protein and Arginine metabolism (as EAA lack Arginine) were assessed by stable isotope methodology. Protein synthesis but not protein breakdown was higher after EAA and 70% higher values for net anabolism were found both in patients with and without nutritional failure. Arginine turnover was lower and de novo Arginine synthesis tended lower after EAA. Nitric oxide synthesis was not different. CF patients are highly responsive to EAA intake independent of their nutritional status. Addition of Arginine to the EAA mixture may be warranted in CF.
Based upon animal studies, HMB appears to be metabolized within skeletal muscle into cholesterol , which may then be incorporated into the muscle cell membrane , thereby enhancing membrane integrity and function. [sources 8] The effects of HMB on muscle protein metabolism may help stabilize muscle cell structure.  One review suggested that the observed HMB-induced reduction in the plasma concentration of muscle damage biomarkers (., muscle enzymes such as creatine kinase and lactate dehydrogenase ) in humans following intense exercise may be due to a cholesterol-mediated improvement in muscle cell membrane function. [note 4] 
Glutamine (abbreviated as Gln or Q ; encoded by the codons CAA and CAG) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH 2 + form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO − form, known as carboxylate, under physiological conditions), and a side chain amide which replaces the carboxylic acid side chain of glutamic acid , classifying it as a charge neutral (at physiological pH), polar amino acid. It is non-essential and conditionally essential in humans, meaning the body can usually synthesize sufficient amounts of it, but in some instances of stress, the body's demand for glutamine increases, and glutamine must be obtained from the diet.