Free and protein-bound glutamine have identical splanchnic extraction in healthy human volunteers.
Boza JJ, Dangin M, Moennoz D, Montigon F, Vuichoud J, Jarret A, Pouteau E, Gremaud G, Oguey-Araymon S, Courtois D, Woupeyi A, Finot PA, Ballevre O.
Nestle Research Center, Vers-Chez-Les-Blanc, 1000 Lausanne 26, Switzerland.
The objectives of the present study were to determine the splanchnic extraction of glutamine after ingestion of glutamine-rich protein ((15)N-labeled oat proteins) and to compare it with that of free glutamine and to determine de novo glutamine synthesis before and after glutamine consumption. Eight healthy adults were infused intravenously in the postabsorptive state with L-[1-(13)C]glutamine (3 micromol x kg(-1) x h(-1)) and L-[1-(13)C]lysine (1.5 micromol x kg(-1) x h(-1)) for 8 h. Four hours after the beginning of the infusion, subjects consumed (every 20 min) a liquid formula providing either 2.5 g of protein from (15)N-labeled oat proteins or a mixture of free amino acids that mimicked the oat-amino acid profile and contained L-[2,5-(15)N(2)]glutamine and L-[2-(15)N]lysine. Splanchnic extraction of glutamine reached 62.5 +/- 5.0% and 66.7 +/- 3.9% after administration of (15)N-labeled oat proteins and the mixture of free amino acids, respectively. Lysine splanchnic extraction was also not different (40.9 +/- 11.9% and 34.9 +/- 10.6% for (15)N-labeled oat proteins and free amino acids, respectively).
The main conclusion of the present study is that glutamine is equally bioavailable when given enterally as a free amino acid and when protein bound. Therefore, and taking into consideration the drawbacks of free glutamine supplementation of ready-to-use formulas for enteral nutrition, protein sources naturally rich in this amino acid are the best option for providing stable glutamine.
Oxidation of glutamine by the splanchnic bed in humans.
Haisch M, Fukagawa NK, Matthews DE.
Departments of Medicine and Chemistry, University of Vermont, Burlington, Vermont 05405, USA.
[1,2-(13)C(2)]glutamine and [ring-(2)H(5)]phenylalanine were infused for 7 h into five postabsorptive healthy subjects on two occasions. On one occasion, the tracers were infused intravenously for 3.5 h and then by a nasogastric tube for 3.5 h. The order of infusion was reversed on the other occasion. From the plasma tracer enrichment measurements at plateau during the intravenous and nasogastric infusion periods, we determined that 27 +/- 2% of the enterally delivered phenylalanine and 64 +/- 2% of the glutamine were removed on the first pass by the splanchnic bed. Glutamine flux was 303 +/- 8 micromol. kg(-1). h(-1). Of the enterally delivered [(13)C]glutamine tracer, 73 +/- 2% was recovered as exhaled CO(2) compared with 58 +/- 1% of the intravenously infused tracer. The fraction of the enterally delivered tracer that was oxidized specifically on the first pass by the splanchnic bed was 53 +/- 2%, comprising 83% of the total tracer extracted. From the appearance of (13)C in plasma glucose, we estimated that 7 and 10% of the intravenously and nasogastrically infused glutamine tracers, respectively, were converted to glucose. The results for glutamine flux and first-pass extraction were similar to our previously reported values when a [2-(15)N]glutamine tracer [Matthews DE, Morano MA, and Campbell RG, Am J Physiol Endocrinol ****b 264: E848-E854, 1993] was used.
The results of [(13)C]glutamine tracer disposal demonstrate that the major fate of enteral glutamine extraction is for oxidation and that only a minor portion is used for gluconeogenesis.
Effect of glutamine supplementation combined with resistance training in young adults.
Candow DG, Chilibeck PD, Burke DG, Davison KS, Smith-Palmer T.
College of Kinesiology, University of Saskatchewan, Saskatoon, Canada.
The purpose of this study was to assess the effect of oral glutamine supplementation combined with resistance training in young adults. A group of 31 subjects, aged 18-24 years, were randomly allocated to groups (double blind) to receive either glutamine (0.9 g x kg lean tissue mass(-1) x day(-1); n = 17) or a placebo (0.9 g maltodextrin x kg lean tissue mass(-1) x day(-1); n = 14 during 6 weeks of total body resistance training. Exercises were performed for four to five sets of 6-12 repetitions at intensities ranging from 60% to 90% 1 repetition maximum (1 RM). Before and after training, measurements were taken of 1 RM squat and bench press strength, peak knee extension torque (using an isokinetic dynamometer), lean tissue mass (dual energy X-ray absorptiometry) and muscle protein degradation (urinary 3-methylhistidine by high performance liquid chromatography). Repeated measures ANOVA showed that strength, torque, lean tissue mass and 3-methylhistidine increased with training (P < 0.05), with no significant difference between groups. Both groups increased their 1 RM squat by approximately 30% and 1 RM bench press by approximately 14%. The glutamine group showed increases of 6% for knee extension torque, 2% for lean tissue mass and 41% for urinary levels of 3-methylhistidine. The placebo group increased knee extension torque by 5%, lean tissue mass by 1.7% and 3-methylhistidine by 56%.
We conclude that glutamine supplementation during resistance training has no significant effect on muscle performance, body composition or muscle protein degradation in young healthy adults.
The effects of high-dose glutamine ingestion on weightlifting performance
Antonio J, Sanders MS, Kalman D, Woodgate D, Street C.
Sports Science Laboratory, University of Delaware, Newark, Delaware 19716, USA.
The purpose of this study was to determine if high-dose glutamine ingestion affected weightlifting performance. In a double-blind, placebo-controlled, crossover study, 6 resistance-trained men (mean +/- SE: age, 21.5 +/- 0.3 years; weight, 76.5 +/- 2.8 kg(-1)) performed weightlifting exercises after the ingestion of glutamine or glycine (0.3 g x kg(-1)) mixed with calorie-free fruit juice or placebo (calorie-free fruit juice only). Each subject underwent each of the 3 treatments in a randomized order. One hour after ingestion, subjects performed 4 total sets of exercise to momentary muscular failure (2 sets of leg presses at 200% of body weight, 2 sets of bench presses at 100% of body weight). There were no differences in the average number of maximal repetitions performed in the leg press or bench press exercises among the 3 groups.
These data indicate that the short-term ingestion of glutamine does not enhance weightlifting performance in resistance-trained men.
The effect of free glutamine and peptide ingestion on the rate of muscle glycogen resynthesis in man.
van Hall G, Saris WH, van de Schoor PA, Wagenmakers AJ.
Department of Human Biology, Maastricht University, The Netherlands.
[email protected]
The present study investigated previous claims that ingestion of glutamine and of protein-carbohydrate mixtures may increase the rate of glycogen resynthesis following intense exercise. Eight trained subjects were studied during 3 h of recovery while consuming one of four drinks in random order. Drinks were ingested in three 500 ml boluses, immediately after exercise and then after 1 and 2 h of recovery. Each bolus of the control drink contained 0.8 g x kg(-1) body weight of glucose. The other drinks contained the same amount of glucose and 0.3 g x kg(-1) body weight of 1) glutamine, 2) a wheat hydrolysate (26% glutamine) and 3) a whey hydrolysate (6.6% glutamine). Plasma glutamine, decreased by approximately 20% during recovery with ingestion of the control drink, no changes with ingestion of the protein hydrolysates drinks, and a 2-fold increase with ingestion of the free glutamine drinks. The rate of glycogen resynthesis was not significantly different in the four tests: 28 +/- 5, 26 +/- 6, 33 +/- 4, and 34 +/- 3 mmol glucosyl units x kg(-1) dry weight muscle x h(-1) for the control, glutamine, wheat- and whey hydrolysate ingestion, respectively.
It is concluded that ingestion of a glutamine/carbohydrate mixture does not increase the rate of glycogen resynthesis in muscle. Glycogen resynthesis rates were higher, although not statistically significant, after ingestion of the drink containing the wheat (21 +/- 8%) and whey protein hydrolysate (20 +/- 6%) compared to ingestion of the control and free glutamine drinks, implying that further research is needed on the potential protein effect.
