The Role of Protein and Amino Acids in Sustaining and Enhancing Performance

FIGURE 5-1 Major Pathways of Protein Degradation. Source: Young, V.R. and Y.M. Yu, 1996. Protein and amino acid metabolism. Pp. 159-200 in Nutrition and Metabolism in the Surgical Patient, 2nd Edition, Josef E. Fischer, ed. Boston: Little, Brown and Company.

mitochondrial proteins are degraded through energy-dependent pathways requiring hydrolysis of ATP (Gottesman et al., 1997). Extracellular and membrane proteins are degraded through the lysosomal pathway. Although the latter route is not an energy-dependent process in itself, energy is required for proton movement into and maintenance of the acid environment within the lysosome. In Table 5-5, Mitch and Goldberg (1996) have summarized some of the conditions that alter muscle protein degradation through the energy-dependent ubiquitin-proteosome pathway. It is clear from this table that the

TABLE 5-5 Conditions That Alter Muscle Protein Degradation Through the Ubiquitin-Proteosome Pathway

Rat Models	Humans
Increased Protein Degradation
Fasting	Eating disorders
Metabolic acidosis	Renal tubular defects
Renal failure	Uremia
Diabetes mellitus	Diabetes mellitus
Thermal injury	Bums
Endotoxin, bacteria	Sepsis
Tumors	Cancer cachexia
Glucocorticoids	Cushing's Syndrome
Decreased Protein Degradation
Deficient dietary protein	Malnutrition
Hypothyroidism	Hypothyroidism
SOURCE: Adapted from Mitch and Goldberg, 1996

Table of Contents

Front Matter R1-R18

Executive Summary 1-16

I Committee Summary and Recommendations 17-18

1 Committee Review 19-76

2 Responses to Questions, Conclusions, and Recommendations 77-82

II Authored Papers and Workshop Discussions 83-84

3 Protein and Amino Acids: Physiological Optimization for Current and Future Military Operational Scenarios 85-92

4 Overview of Garrison, Field, and Supplemental Protein Intake by U.S. Military Personnel 93-108

5 The Energy Costs of Protein Metabolism: Lean and Mean on Uncle Sam's Team 109-120

6 Regulation of Muscle Mass and Function: Effects of Aging and Hormones 121-136

7 Effects of Protein Intake on Renal Function and on the Development of Renal Disease 137-154

8 Infection and Injury: Effects on Whole Body Protein Metabolism 155-168

9 Inherent Difficulties in Defining Amino Acid Requirements 169-216

10 Amino Acid Flux and Requirements: Counterpoint Tentative Estimates are Feasible and Necessary 217-242

11 Physical Exertion, Amino Acid and Protein Metabolism, and Protein Requirements 243-254

12 Skeletal Muscle Markers 255-278

13 Alterations in Protein Metabolism Due to the Stress of Injury and Infection 279-284

Discussion I 285-288

14 Amino Acid and Protein Requirements: Cognitive Performance, Stress, and Brain Function 289-308

15 Supplementation with Branched-Chain Amino Acids, Glutamine, and Protein Hydrolysates: Rationale for Effects on Metabolism and Performance 309-330

16 Dietary Supplements Aimed at Enhancing Performance: Efficacy and Safety Considerations 331-340

Discussion II 341-346

Appendixes 347-348

A Workshop Agenda 349-352

B Biographical Sketches 353-368

C Acronyms and Abbreviations 369-372

D Proteins and Amino Acids - A Selected Bibliography 373-410

E Protein and Energy Content of Selected Operational Rations 411-412

Index 413-429