Postoperative Infusion of Amino Acids Induces a Positive Protein Balance Independently of the Type of Analgesia Used

2006 ◽  
Vol 105 (2) ◽  
pp. 253-259 ◽  
Author(s):  
Francesco Donatelli ◽  
Thomas Schricker ◽  
Giovanni Mistraletti ◽  
Francisco Asenjo ◽  
Piervirgilio Parrella ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Epidural Analgesia ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Whole Body ◽  
Protein Balance ◽  
Body Protein ◽  
Leucine Oxidation ◽  
Endogenous Glucose

Background Net loss of body protein is a prominent feature of the catabolic response to surgical tissue trauma. Epidural analgesia with hypocaloric dextrose has been demonstrated to attenuate leucine oxidation but was unable to make protein balance positive. The current study was set to determine whether an infusion of amino acids on the second day after colon surgery would revert the catabolic state and promote protein synthesis while maintaining glucose homeostasis in patients receiving epidural analgesia as compared with patient-controlled analgesia with morphine (PCA). Methods Sixteen patients undergoing colorectal surgery were randomly assigned to receive epidural blockade or PCA as analgesic techniques and underwent a 6-h stable isotope infusion study (3 h fasted, 3 h fed) on the second postoperative day. Whole body glucose kinetics and protein turnover were measured using [6,6-2H2]glucose and l-[1-13C]leucine as tracer. Results The infusion of amino acids caused a decrease in endogenous glucose rate of appearance in both groups (P < 0.05), with greater changes in the PCA group (P < 0.05). Administration of amino acids suppressed the appearance of leucine from protein breakdown in both groups (P < 0.05), although the decrease was greater in the PCA group (P < 0.05). Leucine oxidation increased in both groups (P < 0.05), with greater change in the epidural group (P < 0.05). Protein synthesis increased to the same extent in both groups (P < 0.05). Protein balance became positive after the infusion of amino acids, and the effect was greater in the PCA group (P < 0.05). Conclusions Infusion of amino acids decreased the endogenous glucose production and induced a positive protein balance independent of the type of anesthesia provided, although such effects were greater in the PCA group.

Glucose and insulin administration while maintaining normoglycemia inhibits whole body protein breakdown and synthesis after cardiac surgery

2014 ◽  
Vol 117 (11) ◽  
pp. 1380-1387 ◽  
Author(s):  
Roupen Hatzakorzian ◽  
Dominique Shum-Tim ◽  
Linda Wykes ◽  
Ansgar Hülshoff ◽  
Helen Bui ◽  
...  
Keyword(s):  
Amino Acids ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Whole Body ◽  
Control Group ◽  
Protein Breakdown ◽  
Body Protein ◽  
Cabg Surgery ◽  
Insulin Group ◽  
Endogenous Glucose

We investigated the effect of insulin administered as part of a hyperinsulinemic-normoglycemic clamp on protein metabolism after coronary artery bypass grafting (CABG) surgery. Eighteen patients were studied, with nine patients in the control group receiving standard metabolic care and nine patients receiving insulin (5 mU·kg−1·min−1). Whole body glucose production, protein breakdown, synthesis, and oxidation were determined using stable isotope tracer kinetics (l-[1-13C]leucine, [6,6-2H2]glucose) before and 6 h after the procedure. Plasma amino acids, cortisol, and lactate were also measured. Endogenous glucose production (preoperatively 10.0 ± 1.6, postoperatively 3.7 ± 2.5 μmol·kg−1·min−1; P = 0.0001), protein breakdown (preoperatively 105.3 ± 9.8, postoperatively 85.2 ± 9.2 mmol·kg−1·h−1; P = 0.0005) and synthesis (preoperatively 88.7 ± 8.7, postoperatively 72.4 ± 8.4 mmol·kg−1·h−1; P = 0.0005) decreased in the presence of hyperinsulinemia, whereas both parameters remained unchanged in the control group. A positive correlation between endogenous glucose production and protein breakdown was observed in the insulin group ( r2 = 0.385). Whole body protein oxidation and balance decreased after surgery in patients receiving insulin without reaching statistical significance. In the insulin group the plasma concentrations of 13 of 20 essential and nonessential amino acids decreased to a significantly greater extent than in the control group. In summary, supraphysiological hyperinsulinemia, while maintaining normoglycemia, decreased whole body protein breakdown and synthesis in patients undergoing CABG surgery. However, net protein balance remained negative.

The Anabolic Effect of Epidural Blockade Requires Energy and Substrate Supply

2002 ◽  
Vol 97 (4) ◽  
pp. 943-951 ◽  
Author(s):  
Thomas Schricker ◽  
Linda Wykes ◽  
Leopold Eberhart ◽  
Ralph Lattermann ◽  
Louise Mazza ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Glucose Production ◽  
Whole Body ◽  
Body Protein ◽  
Epidural Blockade ◽  
Thoracic Epidural ◽  
Parenteral Alimentation ◽  
Infusion Study ◽  
Intravenous Analgesia

Background The authors examined the hypothesis that continuous thoracic epidural blockade with local anesthetic and opioid, in contrast to patient-controlled intravenous analgesia with morphine, stimulates postoperative whole body protein synthesis during combined provision of energy (4 mg x kg(-1) x min(-1) glucose) and amino acids (0.02 ml x kg(-1) x min(-1) Travasol 10%, equivalent to approximately 2.9 g x kg(-1) x day(-1)). Methods Sixteen patients were randomly assigned to undergo a 6-h stable isotope infusion study (3 h fasted, 3 h feeding) on the second day after colorectal surgery performed with or without perioperative epidural blockade. Protein synthesis, breakdown and oxidation, glucose production, and clearance were measured by L-[1-(13)C]leucine and [6,6-(2)H(2) ]glucose. Results Epidural blockade did not affect protein and glucose metabolism in the fasted state. Parenteral alimentation decreased endogenous protein breakdown and glucose production to the same extent in both groups. Administration of glucose and amino acids was associated with an increase in whole body protein synthesis that was modified by the type of analgesia, i.e., protein synthesis increased by 13% in the epidural group (from 93.3 +/- 16.6 to 104.5 +/- 11.1 micromol x kg(-1) x h(-1) ) and by 4% in the patient-controlled analgesia group (from 90.0 +/- 27.1 to 92.9 +/- 14.8 micromol x kg(-1) x h(-1);P = 0.054). Conclusions Epidural blockade accentuates the stimulating effect of parenteral alimentation on whole body protein synthesis.

Epidural Ropivacaine versus  Epidural Morphine and the Catabolic Response to Colonic Surgery

2004 ◽  
Vol 100 (4) ◽  
pp. 973-978 ◽  
Author(s):  
Thomas Schricker ◽  
Linda Wykes ◽  
Leopold Eberhart ◽  
Ralph Lattermann ◽  
Franco Carli
Keyword(s):  
Protein Synthesis ◽  
Epidural Analgesia ◽  
Protein Oxidation ◽  
Glucose Production ◽  
Whole Body ◽  
Protein Breakdown ◽  
Body Protein ◽  
Oxidation Rates ◽  
Metabolic Substrates ◽  
Catabolic Response

Background The authors examined the hypothesis that epidural administration of local anesthetic, in contrast to epidural analgesia with morphine, inhibits postoperative protein oxidation during administration of glucose. Methods Fourteen patients were randomly assigned to undergo a 6-h stable isotope infusion study (3 h fasted, 3 h feeding with 4 mg.kg(-1).min(-1) glucose) on the second day after colorectal surgery using epidural analgesia with either continuous ropivacaine or intermittent morphine. Protein synthesis, breakdown and oxidation, and glucose production were measured by L-[L-13C]leucine and [6,6-2H2]glucose. Substrate oxidation rates were determined by indirect calorimetry. Plasma concentrations of metabolic substrates and hormones were also measured. Results Whole body protein breakdown, oxidation, synthesis, and glucose production in the fasted state were similar between the two groups. Glucose administration decreased protein breakdown (P = 0.01), protein synthesis (P = 0.001), and glucose production (P = 0.001) to the same extent in both groups, whereas protein oxidation was not significantly affected. The type of epidural analgesia did not significantly influence the circulating concentrations of metabolic substrates and hormones in the fasted or in the fed state. Carbohydrate oxidation rate in the ropivacaine group was greater than in patients receiving morphine (P = 0.04), regardless of whether glucose was infused. Conclusion Epidural analgesia achieved with ropivacaine or morphine does not suppress the catabolic response to surgery, either under fasting conditions or in the presence of an energy supply.

Effects of growth hormone and IGF-I on glucocorticoid-induced protein catabolism in humans

1996 ◽  
Vol 270 (4) ◽  
pp. E552-E558 ◽  
Author(s):  
M. Oehri ◽  
R. Ninnis ◽  
J. Girard ◽  
F. J. Frey ◽  
U. Keller
Keyword(s):  
Growth Hormone ◽  
Plasma Concentrations ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Whole Body ◽  
Protein Catabolism ◽  
Body Protein ◽  
Glucose Clearance ◽  
Igf I ◽  
Endogenous Glucose

The effects of similar increases in total insulin-like growth factor I (IGF-I) plasma concentrations achieved by either recombinant human (rh) growth hormone (GH) or rhIGF-I administration on whole body protein and glucose kinetics were assessed. Twenty-six healthy subjects received methylprednisolone (0.5 mg.kg-1.day-1 orally) during 6 days in combination with either placebo (saline sc), GH (0.3 mg.kg-1.day-1 sc), or IGF-I (80 micrograms.kg-1.day-1 sc) in a double-blind randomized fashion. Glucocorticoid administration resulted in protein catabolism as indicated by an increase in leucine flux and a 62 +/- 13% increase in leucine oxidation ([1-13C]leucine infusion technique); this increase was abolished by GH (-1 +/- 18%) as was statistically insignificant during IGF-I treatment (+53 +/- 25%). GH increased endogenous glucose production by 28 +/- 8%, augmented glucocorticoid-induced insulin resistance of peripheral glucose clearance (euglycemic clamp), and increased circulating lipids. IGF-I administration resulted in both increased endogenous glucose production and increased peripheral glucose clearance such that plasma glucose concentrations remained unchanged by IGF-I. IGF-I lowered circulating GH and insulin and altered IGF binding proteins, which all may have reduced bioactivity of IGF-I. The data demonstrate that, in spite of similar total IGF-I plasma concentrations during treatment, GH and IGF-I exert markedly different effects on whole body leucine, glucose, and lipid metabolism.

TNF directly stimulates glucose uptake and leucine oxidation and inhibits FFA flux in conscious dogs

1996 ◽  
Vol 270 (5) ◽  
pp. E864-E872 ◽  
Author(s):  
Y. Sakurai ◽  
X. J. Zhang ◽  
R. R. Wolfe
Keyword(s):  
Glucose Production ◽  
Baseline Period ◽  
Endogenous Glucose Production ◽  
Whole Body ◽  
Constant Infusion ◽  
Direct Effects ◽  
Body Protein ◽  
Leucine Oxidation ◽  
Period 2 ◽  
Plasma Ffa

We tested the hypothesis that the metabolic changes in glucose, lipid, and protein metabolism seen during tumor necrosis factor (TNF) infusion were due to the increase in plasma glucagon concentration rather than to the direct effects of TNF. We employed a pancreatic clamp technique to keep plasma insulin and glucagon concentrations constant throughout a 4-h isotope infusion. Glucose, lipid, and protein kinetics were measured by means of the primed, constant infusion of [6,6-2H]glucose, [2H5]glycerol, [2H2]palmitic acid, and [1-13C]leucine. After a 2-h baseline period (period 1), TNF was infused as a primed, constant infusion (prime, 2.5 micrograms/kg; constant infusion, 62.5 ng.kg-1.min-1) for 2 h (period 2). Whereas plasma glucose concentration dropped significantly during TNF infusion, endogenous glucose production did not change. The decrease in glucose concentrations was due to a stimulation of glucose clearance (P < 0.05). The rate of lipolysis did not decrease significantly, but free fatty acid (FFA) flux and plasma FFA concentration significantly decreased during TNF infusion (P < 0.05). The rate of appearance of leucine was not affected by TNF infusion, but TNF caused a significant increase in 13CO2 excretion (P < 0.05) and leucine oxidation (P < 0.05). The calculated rates of whole body protein synthesis decreased. We concluded that TNF did not directly affect glucose production. Furthermore, changes in protein and lipid kinetics during TNF infusion were not mediated by changes in insulin or glucagon and may have reflected direct effects of TNF.

scholarly journals Hyperinsulinemic-normoglycemic clamp administered together with amino acids induces anabolism after cardiac surgery

2016 ◽  
Vol 311 (6) ◽  
pp. R1085-R1092 ◽  
Author(s):  
Takumi Codère-Maruyama ◽  
Thomas Schricker ◽  
Dominique Shum-Tim ◽  
Linda Wykes ◽  
Evan Nitschmann ◽  
...  
Keyword(s):  
Cardiac Surgery ◽  
Heart Surgery ◽  
Artery Bypass ◽  
Open Heart Surgery ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Whole Body ◽  
High Dose ◽  
Protein Balance ◽  
Body Protein

Cardiac surgery triggers an inflammatory stress response, leading to protein catabolism, a process that even high-dose insulin therapy alone cannot reverse. To determine whether hyperinsulinemic-normoglycemic clamp and perioperative amino acid (AA) supplementation improves whole body protein balance, 20 patients scheduled for elective coronary artery bypass grafting surgery were randomly assigned to have intra- and postoperative hyperinsulinemic-normoglycemic clamp, with or without intravenous AA supplementation. Primed continuous infusions of [6,6-2H2]glucose and l-[1-13C]leucine were used to quantify whole body protein and glucose metabolism before and after surgery. Adipose tissue and serum cytokines were also analyzed to measure their responsiveness to the anabolic effect of AA administration. During hyperinsulinemic-normoglycemic clamp, AA supplementation successfully stimulated whole body protein synthesis, resulting in a positive whole body protein balance after surgery (insulin: −13.6 ± 4.5 vs. insulin + AA: 2.1 ± 5.4 μmol·kg−1·h−1, P < 0.001). Endogenous glucose production was equally suppressed in both groups (insulin: 0.0 ± 3.8 vs. insulin + AA 1.6 ± 1.6 μmol·kg−1·min−1, P = 0.230). AA supplementation led to significant changes in serum and tissue IL-6 (insulin: 246.6 ± 111.2 vs. insulin + AA: 124.5 ± 79.3 pg/ml, P = 0.011). In conclusion, hyperinsulinemic-normoglycemic clamp technique, together with AA supplementation, can induce an anabolic state after open-heart surgery, as quantified by a positive whole body protein balance.

Measurement of protein turnover in the small intestine of lambs. 2. Effects of feed intake

1997 ◽  
Vol 128 (2) ◽  
pp. 233-246 ◽  
Author(s):  
S. A. NEUTZE ◽  
J. M. GOODEN ◽  
V. H. ODDY
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Small Intestine ◽  
Experimental Model ◽  
Feed Intake ◽  
Protein Turnover ◽  
Jugular Vein ◽  
Specific Radioactivity ◽  
Whole Body ◽  
Body Protein

This study used an experimental model, described in a companion paper, to examine the effects of feed intake on protein turnover in the small intestine of lambs. Ten male castrate lambs (∼ 10 months old) were offered, via continuous feeders, either 400 (n = 5) or 1200 (n = 5) g/day lucerne chaff, and mean experimental liveweights were 28 and 33 kg respectively. All lambs were prepared with catheters in the cranial mesenteric vein (CMV), femoral artery (FA), jugular vein and abomasum, and a blood flow probe around the CMV. Cr-EDTA (0·139 mg Cr/ml, ∼ 0·2 ml/min) was infused abomasally for 24 h and L-[2,6-3H]phenylalanine (Phe) (420±9·35 μCi into the abomasum) and L-[U-14C]phenylalanine (49·6±3·59 μCi into the jugular vein) were also infused during the last 8 h. Blood from the CMV and FA was sampled during the isotope infusions. At the end of infusions, lambs were killed and tissue (n = 4) and digesta (n = 2) samples removed from the small intestine (SI) of each animal. Transfers of labelled and unlabelled Phe were measured between SI tissue, its lumen and blood, enabling both fractional and absolute rates of protein synthesis and gain to be estimated.Total SI mass increased significantly with feed intake (P < 0·05), although not on a liveweight basis. Fractional rates of protein gain in the SI tended to increase (P = 0·12) with feed intake; these rates were −16·2 (±13·7) and 23·3 (±15·2) % per day in lambs offered 400 and 1200 g/day respectively. Mean protein synthesis and fractional synthesis rates (FSR), calculated from the mean retention of 14C and 3H in SI tissue, were both positively affected by feed intake (0·01 < P < 0·05). The choice of free Phe pool for estimating precursor specific radioactivity (SRA) for protein synthesis had a major effect on FSR. Assuming that tissue free Phe SRA represented precursor SRA, mean FSR were 81 (±15) and 145 (±24) % per day in lambs offered 400 and 1200 g/day respectively. Corresponding estimates for free Phe SRA in the FA and CMV were 28 (±2·9) and 42 (±3·5) % per day on 400 g/day, and 61 (±2·9) and 94 (±6·0) on 1200 g/day. The correct value for protein synthesis was therefore in doubt, although indirect evidence suggested that blood SRA (either FA or CMV) may be closest to true precursor SRA. This evidence included (i) comparison with flooding dose estimates of FSR, (ii) comparison of 3H[ratio ]14C Phe SRA in free Phe pools with this ratio in SI protein, and (iii) the proportion of SI energy use associated with protein synthesis.Using the experimental model, the proportion of small intestinal protein synthesis exported was estimated as 0·13–0·27 (depending on the choice of precursor) and was unaffected by feed intake. The contribution of the small intestine to whole body protein synthesis tended to be higher in lambs offered 1200 g/day (0·21) than in those offered 400 g/day (0·13). The data obtained in this study suggested a role for the small intestine in modulating amino acid supply with changes in feed intake. At high intake (1200 g/day), the small intestine increases in mass and CMV uptake of amino acids is less than absorption from the lumen, while at low intake (400 g/day), this organ loses mass and CMV uptake of amino acids exceeds that absorbed. The implications of these findings are discussed.

scholarly journals Presleep dietary protein-derived amino acids are incorporated in myofibrillar protein during postexercise overnight recovery

2018 ◽  
Vol 314 (5) ◽  
pp. E457-E467 ◽  
Author(s):  
Jorn Trommelen ◽  
Imre W. K. Kouw ◽  
Andrew M. Holwerda ◽  
Tim Snijders ◽  
Shona L. Halson ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Dietary Protein ◽  
Myofibrillar Protein ◽  
Whole Body ◽  
Body Protein ◽  
Protein Ingestion ◽  
Casein Protein ◽  
The Impact ◽  
Myofibrillar Protein Synthesis

The purpose of this study was to determine the impact of ingesting 30 g casein protein with and without 2 g free leucine before sleep on myofibrillar protein synthesis rates during postexercise overnight recovery. Thirty-six healthy young men performed a single bout of resistance-type exercise in the evening (1945) after a full day of dietary standardization. Thirty minutes before sleep (2330), subjects ingested 30 g intrinsically l-[1-13C]phenylalanine-labeled protein with (PRO+leu, n = 12) or without (PRO, n = 12) 2 g free leucine, or a noncaloric placebo (PLA, n = 12). Continuous intravenous l-[ ring-2H5]phenylalanine, l-[1-13C]leucine, and l-[ ring-2H2]tyrosine infusions were applied. Blood and muscle tissue samples were collected to assess whole body protein net balance, myofibrillar protein synthesis rates, and overnight incorporation of dietary protein-derived amino acids into myofibrillar protein. Protein ingestion before sleep improved overnight whole body protein net balance ( P < 0.001). Myofibrillar protein synthesis rates did not differ significantly between treatments as assessed by l-[ ring-2H5]phenylalanine (0.057 ± 0.002, 0.055 ± 0.002, and 0.055 ± 0.004%/h for PLA, PRO, and PRO+leu, respectively; means ± SE; P = 0.850) or l-[1-13C]leucine (0.080 ± 0.004, 0.073 ± 0.004, and 0.083 ± 0.006%/h, respectively; P = 0.328). Myofibrillar l-[1-13C]phenylalanine enrichments increased following protein ingestion but did not differ between the PRO and PRO+leu treatments. In conclusion, protein ingestion before sleep improves whole body protein net balance and provides amino acids that are incorporated into myofibrillar protein during sleep. However, the ingestion of 30 g casein protein with or without additional free leucine before sleep does not increase muscle protein synthesis rates during postexercise overnight recovery.

Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects

2005 ◽  
Vol 288 (4) ◽  
pp. E645-E653 ◽  
Author(s):  
René Koopman ◽  
Anton J. M. Wagenmakers ◽  
Ralph J. F. Manders ◽  
Antoine H. G. Zorenc ◽  
Joan M. G. Senden ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Whole Body ◽  
Vastus Lateralis Muscle ◽  
Protein Balance ◽  
Body Protein ◽  
Breakdown Rates ◽  
Postexercise Recovery ◽  
Male Subjects

The present study was designed to determine postexercise muscle protein synthesis and whole body protein balance following the combined ingestion of carbohydrate with or without protein and/or free leucine. Eight male subjects were randomly assigned to three trials in which they consumed drinks containing either carbohydrate (CHO), carbohydrate and protein (CHO+PRO), or carbohydrate, protein, and free leucine (CHO+PRO+Leu) following 45 min of resistance exercise. A primed, continuous infusion of l-[ ring-13C6]phenylalanine was applied, with blood samples and muscle biopsies collected to assess fractional synthetic rate (FSR) in the vastus lateralis muscle as well as whole body protein turnover during 6 h of postexercise recovery. Plasma insulin response was higher in the CHO+PRO+Leu compared with the CHO and CHO+PRO trials (+240 ± 19% and +77 ± 11%, respectively, P < 0.05). Whole body protein breakdown rates were lower, and whole body protein synthesis rates were higher, in the CHO+PRO and CHO+PRO+Leu trials compared with the CHO trial ( P < 0.05). Addition of leucine in the CHO+PRO+Leu trial resulted in a lower protein oxidation rate compared with the CHO+PRO trial. Protein balance was negative during recovery in the CHO trial but positive in the CHO+PRO and CHO+PRO+Leu trials. In the CHO+PRO+Leu trial, whole body net protein balance was significantly greater compared with values observed in the CHO+PRO and CHO trials ( P < 0.05). Mixed muscle FSR, measured over a 6-h period of postexercise recovery, was significantly greater in the CHO+PRO+Leu trial compared with the CHO trial (0.095 ± 0.006 vs. 0.061 ± 0.008%/h, respectively, P < 0.05), with intermediate values observed in the CHO+PRO trial (0.0820 ± 0.0104%/h). We conclude that coingestion of protein and leucine stimulates muscle protein synthesis and optimizes whole body protein balance compared with the intake of carbohydrate only.

scholarly journals Muscle Protein Synthesis and Whole-Body Protein Turnover Responses to Ingesting Essential Amino Acids, Intact Protein, and Protein-Containing Mixed Meals with Considerations for Energy Deficit

Nutrients ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2457 ◽  
Author(s):  
Jess A. Gwin ◽  
David D. Church ◽  
Robert R. Wolfe ◽  
Arny A. Ferrando ◽  
Stefan M. Pasiakos
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Energy Deficit ◽  
Whole Body ◽  
Intact Protein ◽  
Body Protein ◽  
Protein Feeding

Protein intake recommendations to optimally stimulate muscle protein synthesis (MPS) are derived from dose-response studies examining the stimulatory effects of isolated intact proteins (e.g., whey, egg) on MPS in healthy individuals during energy balance. Those recommendations may not be adequate during periods of physiological stress, specifically the catabolic stress induced by energy deficit. Providing supplemental intact protein (20–25 g whey protein, 0.25–0.3 g protein/kg per meal) during strenuous military operations that elicit severe energy deficit does not stimulate MPS-associated anabolic signaling or attenuate lean mass loss. This occurs likely because a greater proportion of the dietary amino acids consumed are targeted for energy-yielding pathways, whole-body protein synthesis, and other whole-body essential amino acid (EAA)-requiring processes than the proportion targeted for MPS. Protein feeding formats that provide sufficient energy to offset whole-body energy and protein-requiring demands during energy deficit and leverage EAA content, digestion, and absorption kinetics may optimize MPS under these conditions. Understanding the effects of protein feeding format-driven alterations in EAA availability and subsequent changes in MPS and whole-body protein turnover is required to design feeding strategies that mitigate the catabolic effects of energy deficit. In this manuscript, we review the effects, advantages, disadvantages, and knowledge gaps pertaining to supplemental free-form EAA, intact protein, and protein-containing mixed meal ingestion on MPS. We discuss the fundamental role of whole-body protein balance and highlight the importance of comprehensively assessing whole-body and muscle protein kinetics when evaluating the anabolic potential of varying protein feeding formats during energy deficit.

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