The 24-h whole body leucine and urea kinetics at normal  and high protein intakes with exercise in healthy adults

Forslund, Anders; Hambræus, Leif; Olsson, Roger; El-Khoury, Antoine E.; Yu, Yong‐Ming; Young, Vernon R.

doi:10.1152/ajpendo.1998.275.2.e310

Cited by 36 publications

(57 citation statements)

References 25 publications

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“…, before, during, or after exercise (7,9,13). The only consistent response is an increase in leucine oxidation with higher protein intakes (7,13).…”

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confidence: 99%

Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates after endurance exercise

Bolster¹,

Pikosky²,

Gaine³

et al. 2005

American Journal of Physiology-Endocrinology and Metabolism

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Five endurance-trained, male runners participated in a randomized, crossover design diet intervention, where they consumed either a low (0.8 g/kg; LP)-, moderate (1.8 g/kg; MP)-, or high (3.6 g/kg; HP)-protein diet for 4 wk. Diets were designed to be eucaloric with carbohydrate, fat, and protein approximating 60, 30, and 10%; 55, 30, and 15%; and 40, 30, and 30% for LP, MP, and HP, respectively. Substrate oxidation was assessed via indirect calorimetry at 3 wk of the dietary interventions. Mixed-muscle protein fractional synthetic rate (FSR) was measured after an endurance run (75 min at 70% V O2 peak) using a primed, continuous infusion of [ 2 H5]phenylalanine. Protein oxidation increased with increasing protein intake, with each trial being significantly different from the other (P Ͻ 0.01). FSR after exercise was significantly greater for LP (0.083%/h) and MP (0.078%/h) than for HP (0.052%/h; P Ͻ 0.05). There was no difference in FSR between LP and MP. This is the first investigation to establish that habitual dietary protein intake in humans modulates skeletal muscle protein synthesis after an endurance exercise bout. Future studies directed at mechanisms by which level of protein intake influences skeletal muscle turnover are needed. amino acids; fractional synthetic rate; humans THE EFFECT OF ACUTE EXERCISE on protein metabolism is well documented. The majority of investigations regarding protein metabolism and endurance exercise to date have examined whole body protein turnover. These findings suggest the protein turnover response during this mode of exercise is catabolic in nature (9,25,27,35), with the postexercise environment being more anabolic (or at least less catabolic; see Refs. 12,25,and 29). The majority of studies examining skeletal muscle protein turnover have focused on the effect of resistance exercise. Few published studies have directly assessed the effect of acute aerobic exercise on skeletal muscle protein synthesis in humans (10,26,29). Skeletal muscle protein synthesis [fractional synthetic rate (FSR)] is increased after resistance exercise; however, the simultaneous increase in breakdown [fractional breakdown rate (FBR)] results in a NET balance (FSR Ϫ FBR) that remains negative (3, 23). Leg protein kinetic data after a 60-min cycling bout indicates that a negative NET is noted after aerobic exercise in the fasted state (20). It is generally accepted that, in the fasted state, NET muscle balance will remain negative. However, the acute provision of nutrients (primarily amino acids) can influence skeletal muscle protein turnover, such that NET becomes positive. These studies provide substantial evidence that, when amino acids (alone or with carbohydrates) are administered immediately postexercise, a shift to a positive NET balance results (4,5,24,28,30,33). A similar positive NET balance has been reported when a protein-containing supplement was consumed after endurance exercise (20). Therefore, provision of exogenous amino acids creates a more anabolic environment by increasing muscle...

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“…, before, during, or after exercise (7,9,13). The only consistent response is an increase in leucine oxidation with higher protein intakes (7,13).…”

mentioning

confidence: 99%

Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates after endurance exercise

Bolster¹,

Pikosky²,

Gaine³

et al. 2005

American Journal of Physiology-Endocrinology and Metabolism

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“…Splanchnic extraction cannot be measured directly, and a reliable assessment is difficult. Retention of 10 to 32% of gut-absorbed dietary leucine has been reported (22,(25)(26)(27)(28). Little is known about splanchnic retention of peritoneally absorbed AA (15).…”

Section: Discussionmentioning

confidence: 99%

“…Little is known about splanchnic retention of peritoneally absorbed AA (15). We assumed a value of 25% for both orally and peritoneally absorbed AA (22). Assuming increasing values of splanchnic retention brings about that the effects of protein intake shift from inhibition of protein breakdown to stimulation of protein synthesis.…”

Section: Discussionmentioning

confidence: 99%

“…A fraction of 0.25 of absorbed leucine was assumed for the retention in the splanchnicus bed (22). This correction factor was ap- Figure 1.…”

Section: Calculations Of Wbptmentioning

confidence: 99%

“…A fraction of 0.32 was assumed for the oxidation of leucine taken up by the splanchnic region (22). Therefore, leucine fluxes and rates of whole-body protein synthesis and breakdown corrected for splanchnic uptake were calculated as follows …”

Section: Calculations Of Wbptmentioning

confidence: 99%

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Peritoneal Dialysis with Solutions Containing Amino Acids Plus Glucose Promotes Protein Synthesis during Oral Feeding

Tjiong

Rietveld

Wattimena

et al. 2007

Clinical Journal of the American Society of Nephrology

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Inadequate food intake plays an important role in the development of malnutrition. Recently, an increased rate of protein anabolism was shown in fasting state in patients who were on automated peritoneal dialysis with combined amino acids (AA) and glucose (G) dialysate serving as a source of both proteins and calories. This study investigated the effects of such a dialysis procedure in the daytime in the fed state in patients who were on continuous ambulatory peritoneal dialysis (CAPD). A crossover study was performed in 12 CAPD patients to compare, at 7-d intervals, a mixture of AA (Nutrineal 1.1%) plus G (Physioneal l.36 to 3.86%) versus G only as control dialysate. Whole-body protein turnover was studied by primed constant intravenous infusion of 13 C-leucine during the 9-h dialysis. For meeting steady-state conditions during whole-body protein turnover, frequent exchanges with a mixture of AA plus G were done using an automated cycler. M any patients who are on peritoneal dialysis (PD) develop protein-energy malnutrition (1,2). Inflammation, acidosis, insulin resistance, insufficient intake of proteins and calories as a result of anorexia, and peritoneal losses of proteins and amino acids (AA) contribute to protein-energy malnutrition (3-5). A strong association between malnutrition, inflammatory parameters, and cardiovascular mortality has been reported (6 -10). However, it is not understood completely how these factors are related causally.Dialysate that contains AA was introduced to compensate for low protein intake and protein losses (11-13). The use of AAcontaining dialysate was shown to be most effective when intraperitoneal AA were supplied simultaneously with sufficient oral calories (14 -18). However, anorexia in continuous ambulatory PD (CAPD) patients prevents adequate oral intake of protein and calories. Recently, we showed improved protein anabolism in fasting patients who were on PD with dialysate that contained AA plus glucose (G) (18).The daily cycle of fasting and feeding plays a key role in whole-body protein homeostasis. In this study, we examined the metabolic effects of AA plus G (AAG) dialysis in PD patients to determine whether the AAG mixture could contribute to protein anabolism in the fed state. This could be of clinical relevance especially when daily protein and calorie intake of CAPD patients is insufficient. Effects of AAG dialysate on protein metabolism were studied using whole-body protein turnover (WBPT). Because metabolic steady-state conditions are not achieved with a standard CAPD scheme, frequent dialysate exchanges were done using an automated cycler. The dialysis took place during the day while the patients consumed liquid food hourly in identical portions. This was a randomorder crossover study in 12 patients to compare AAG dialysate with G dialysate as a control at 1-wk intervals. Materials and Methods PatientsTwelve CAPD patients were recruited from the PD Unit of the Erasmus Medical Center. Inclusion criteria called for stable patients who were on PD for Ͼ3 mo and h...

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Nutrition and Fluid Intake with Training

Hambræus¹,

Branth²,

Raben³

2003

Textbook of Sports Medicine

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The 24-h whole body leucine and urea kinetics at normal and high protein intakes with exercise in healthy adults

Cited by 36 publications

References 25 publications

Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates after endurance exercise

Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates after endurance exercise

Peritoneal Dialysis with Solutions Containing Amino Acids Plus Glucose Promotes Protein Synthesis during Oral Feeding

Nutrition and Fluid Intake with Training

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