A prospective clinical trial was undertaken to determine the nitrogen-sparing efficacy of three amino acid solutions with different concentrations of branched-chain amino acids (BCAA) in 25 postoperative patients. The patients were a homogenous male population with stage I bladder cancer who underwent radical cystectomy. Administration rates of the intravenous solutions were designed to provide 30 kcal/kg/day and 1.5 g protein per kg per day during the 7-day study period. A control group (n = 4) received 5% dextrose in water (150 g/day). Nitrogen balance was determined daily and the whole body protein turnover was measured using a primed-constant infusion of 15N glycine on postoperative days 3 and 4. The group receiving the 45% BCAA enriched (low leucine) amino acid solution exhibited a significant decrease in cumulative (7 day) nitrogen balance (7.6 +/- 2.6 g) compared to the groups receiving either the standard 25% BCAA (19.9 +/- 2.1 g) or the 45% BCAA enriched (high leucine) (21.6 +/- 7.0 g) amino acid solution. The group receiving the 45% BCAA enriched (low leucine) amino acid solution exhibited a higher rate of mean whole body protein catabolism compared to the other groups. For patients undergoing major elective operations, the amount of leucine necessary for optimal daily nitrogen balance was 0.13 g/kg/day. These results demonstrate that the ratio of individual BCAA and the amount of leucine were more critical to nitrogen-sparing efficacy than the percentage total BCAA infused.

Biofilms are surface-attached, matrix-enclosed microbial communities that can cause various diseases like formation of dental plague, urinary tract infection and cystic fibrosis. The purpose of this study was to examine the effects of amino acids (arginine, valine, leucine, glycine, lysine, phenylalanine, threonine and proline) on biofilm formation swimming motility and twitching motility in Escherichia coli BL21. M63 minimal salt media (supplemented with different types and concentrations of amino acids) were used for induction of biofilm formation and the resulting biofilm growth was quantified spectrophotometrically at optical density of 550 nm after 24 hours of inoculation. For swimming and twitching motility assays, amino acid-supplemented tryptone and Luria-Bertani agar plates were used and the diameter of halo formed in the agar was measured after the same duration. The eight amino acids tested showed varied effects on biofilm formation, swimming motility and twitching motility in E. coli BL21. Leucine, glycine, threonine and proline promoted both twitching and swimming motility up to about 100%. Arginine and valine increased swimming motility up to 50% but had no effect on twitching motility. Lysine and phenylalanine completely inhibited both swimming and twitching motility in the bacteria. With regard to biofilm formation, both leucine and valine promoted it up to a maximum of 25%. However, glycine, lysine, phenylalanine, and threonine inhibited biofilm formation; proline and arginine showed inhibitory effects only at higher concentrations (0.4%). These results suggest that amino acids may play a role in inhibiting or promoting biofilm formation. The potential use of amino acid-based dietary supplements to control biofilm formation and ultimately to treat its associated diseases warrants further investigation.

We asked the question, if the amount of nutrients given parenterally is progressively increased, does the rate of whole body protein synthesis rate increase correspondingly and how does the protein breakdown rate change? Eight malnourished patients requiring total parenteral nutrition (TPN) were studied. We measured their whole body protein synthesis and breakdown rate four times at intervals of 3 days using 15N glycine as the tracer. The first study was done pre-TPN. The 2nd, 3rd, and 4th studies were done at increasing TPN rates. The rates were TPN 1, 1440 kcal/day and 7.9 g/N/day; TPN 2, 2160 kcal/day and 11.9 g/N/day; TPN 3, 2880 kcal/day and 15.8 g/N/day. The protein synthesis rate initially increased as the amount of TPN was increased, but increasing the rate from TPN-2 to TPN-3 did not result in further increase. Increasing the rate of TPN above a certain level does not lead to a concomitant increase in the protein synthesis rate.

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