Human Protein Metabolism

1 The Importance of Protein Dynamics.- Protein Structure and the Concept of Protein Turnover.- Rapid Turnover of Proteins Facilitates Rapid Changes in Protein Concentrations.- Protein Turnover Is Necessary to Maintain Protein Quality.- 2 Basic Mechanisms of Protein Turnover.- Protein Degradation.- Disposal of Amino Acids Generated by Proteolysis.- Protein Synthesis.- Posttranslational Modifications.- Mitochondrial Protein Synthesis.- Potential Sites of Regulation of Protein Turnover.- 3 Methods for Studying Protein Metabolism in Humans.- Measuring Changes in Protein Mass of the Body.- Whole-Body Protein Turnover.- Whole-Body Protein Oxidation.- Protein Metabolism in Specific Organs or Limbs.- Incorporation of Tracer into Tissue Proteins or Specific Proteins.- Polyribosome Abundance as a Measure of Protein Synthesis.- 3-Methylhistidine Excretion as a Measure of Myofibrillar Proteolysis.- Markers of Collagen Metabolism.- Radioiodinated Protein Administration to Measure Protein Half-Life.- Analytical Methods.- 4 Normative Data from Infancy to Old Age.- Whole-Body N Balance.- Protein Oxidation.- Whole-Body Protein Turnover.- Protein Turnover in Organs and Tissues.- Turnover of Specific Proteins.- 5 Nutritional Influences.- Acute Responses to Meals.- Starvation.- Very-Low-Energy Diets.- Malnutrition.- High Energy Intake.- High Protein Intake.- Summary of Effects of Energy and Protein on Whole-Body Protein Metabolism.- 6 Endocrine, Paracrine, and Autocrine Regulation.- Insulin.- Growth Hormone.- Insulin-Like Growth Factor-I (IGF-1).- Other Growth Factors.- Androgens.- Ovarian Steroids.- Epinephrine.- Cortisol.- Thyroid Hormones.- Glucagon.- Cytokines.- Prostaglandins.- 7 Regulation by Metabolic Substrates.- Amino Acids.- Glucose and Its Metabolites.- Triglycerides, Fatty Acids, and Ketone Bodies.- Summary.- 8 Physical Activity.- Effect of Inactivity on Protein Metabolism.- Effect of Increased Physical Activity on Protein Metabolism.- 9 Topics of Clinical Interest.-