Human Protein Metabolism

Human Protein Metabolism is a succinct review of hundreds of studies on the regulation of protein mass and protein turnover in the human body. The biochemistry of protein synthesis and breakdown is summarized, and the methods that are used to examine protein metabolism in humans are explained, and their limitations discussed. The book includes chapters that review the effects of nutrition, hormones, metabolic substrates, and physical activity. Various topics of clinical interest are covered, including cancer, diabetes, tissue injury, pregnancy, renal disease, muscular dystrophies, and other conditions. Normal values are presented for turnover of proteins in the whole body and individual organs,and for turnover of many individual proteins. This book will be a valuable resource for physiologists, nutritionists, and clinicians interested in the regulation of body protein stores in health and disease. For scientists primarily interested in the basic aspects of protein metabolism, it shows how the basic knowledge is being applied to the study of humans.

This book provides a thorough source of information on the methods used to study protein metabolism in humans, and what we have learned by using these methods. The book focuses on understanding the principles of the methods, and on their limitations. It discusses the basic concepts and mechanisms of protein dynamics and turnover, nutritional influences and the regulation of the process by hormones and by general metabolic regulation. A chapter covers the role of physical activity in modulating protein metabolism. Clinical aspects, such as diabetes, obesity, anorexia and malnutrition are also included.

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.- Acidosis.- Alcoholism.- Arthritis.- Cancer.- Cirrhosis.- Diabetes.- Glucocorticoid Therapy.- Heart Disease.- HIV Infection and AIDS.- Infection.- Muscular Dystrophies.- Obesity.- Parenteral and Enteral Nutrition.- Pregnancy and Lactation.- Renal Failure.- Tissue Injury (Trauma, Surgery, Burns).- References.