Transcript Chapter 1
Chapter 7 Integration & Regulation of Metabolism & the Impact of Exercise & Sport 2009 Cengage-Wadsworth Interrelationship of Carbohydrate, Lipid, & Protein Metabolism • Any energy nutrient can fuel the body in the short term • TCA cycle = amphibolic pathway • Lipogenesis – CHO spares lipolysis - promotes gain – Glucose is precursor for glycerol & fatty acids 2009 Cengage-Wadsworth Interrelationship of Carbohydrate, Lipid, & Protein Metabolism • Gluconeogenesis – Glycerol portion only from fat – Fatty acids with odd # of C atoms – Glucogenic amino acids • Conversion among energy nutrients favors lipogenesis 2009 Cengage-Wadsworth Interrelationship of Carbohydrate, Lipid, & Protein Metabolism • TCA cycle & electron transport chain - common to all 3 • This catabolic pathway also: – Produces CO2 for carboxylation & C for other needs – Provides common intermediates – Provides citrate & malate for lipogenesis 2009 Cengage-Wadsworth The Central Role of the Liver in Metabolism • Key processor & distributor • Glycogenesis & glycogenolysis • Protein synthesis, catabolism, conversion to other compounds • Lipoprotein synthesis 2009 Cengage-Wadsworth Tissue-Specific Metabolism during the Fed-Fast Cycle • Stages of fed-fast cycle – Fed state - lasts 3 hours after meal ingestion – Postabsorptive/early fasting state - 3 to 12-18 hours after meal – Fasting state - 18 hours to 2 days after meal when nothing else eaten – Starvation/long-term fast - fully adapted to deprivation (weeks) 2009 Cengage-Wadsworth Carbohydrate & Lipid Metabolism • The fed state – Glucose glycogen & fatty acids – Glucose used by nervous tissues, RBCs, adipose & muscle tissues • The postabsorptive or early fasting state – Glycogenolysis – Gluconeogenesis 2009 Cengage-Wadsworth Carbohydrate & Lipid Metabolism • The fasting state – Amino acids (primarily), glycerol, lactate used for gluconeogenesis – Ketone formation • The starvation state – Fatty acids used to greater extent – Glycerol major glucose source – Ketosis after oxaloacetate depletion 2009 Cengage-Wadsworth Amino Acid Metabolism • Fed state - used for proteins or degraded • Fasting – Catabolism for energy produces quantities of N • Excreted in urea – Gluconeogensis in liver & kidneys 2009 Cengage-Wadsworth System Integration & Homeostasis • Major regulatory systems – Nervous system – Endocrine system – Vascular system • Endocrine function in fed state – GIP, CCK, gastrin, secretin – Insulin 2009 Cengage-Wadsworth System Integration & Homeostasis • Endocrine function in postabsorptive or fasting state – Glucagon – Epinephrine & norepinephrine – Low levels of insulin 2009 Cengage-Wadsworth Metabolic Syndrome • Cluster of risk factors for CVD, CKD & T2DM • Insulin resistance • Weight loss & insulin insensitivity 2009 Cengage-Wadsworth Sports Nutrition • Energy for physical activity comes from nutrients • Energy demands during physical exertion in athletes similar to fedfast cycle 2009 Cengage-Wadsworth Biochemical Assessment of Physical Exertion • Types of muscle – Type I (“red”) - oxidative – Type IIa (“white”) - hybrid of I & IIb – Type IIb (“white”) - fewer mitochondria & active glycolytic pathway • Common measurements – Respiratory quotient (RQ) – Maximal oxygen consumption (VO2 max) 2009 Cengage-Wadsworth Energy Sources during Exercise • The ATP-CP (phosphagen) system – Muscles use high-energy creatine phosphate with ATP • The lactic acid system – Anaerobic glycolysis • The aerobic system – TCA cycle 2009 Cengage-Wadsworth Energy Sources during Exercise • Fuel sources during exercise – Muscle glycogen – Plasma glucose – Plasma fatty acids – Intramuscular triacylglycerols 2009 Cengage-Wadsworth Energy Sources during Exercise • Exercise intensity & duration – Low intensity - plasma fatty acids – Moderate intensity - increased fatty acid oxidation (due to muscle TG) – High intensity - CHO oxidation & lactate production increase 2009 Cengage-Wadsworth Energy Sources during Exercise • Level of exercise training – Training increases muscle glycogen & TG stores • Initial muscle glycogen levels 2009 Cengage-Wadsworth Carbohydrate Supplementation (Supercompensation) • Classical regimen – 2 sessions of intense exercise, 2 days of low-CHO diet, 3 days of high-CHO diet + rest • Modified regimen – Exercise tapered over 5 days, 1 day of rest – 3 days of 50%-CHO diet, then 3 days of 70%-CHO diet 2009 Cengage-Wadsworth Diets for Exercise • Macronutrients • Meal frequency • Pre-event meal • Glycemic index 2009 Cengage-Wadsworth Nutritional Ergogenic Aids • Amino acids – Arginine – Ornithine – Aspartate salts – Branched-chain amino acids • Antioxidants 2009 Cengage-Wadsworth Nutritional Ergogenic Aids • Herbs – The ginsengs • Caffeine • Intermediary metabolites – – – – – Bicarbonate Carnitine Coenzyme Q10 Creatine Other 2009 Cengage-Wadsworth Perspective 7 Diabetes: Metabolism Out of Control 2009 Cengage-Wadsworth Diabetes • Type 2 diabetes – Insulin resistance in peripheral tissues due to lack of functional glucose transporters • Type 1 diabetes – Lack of insulin due to autoimmune response against pancreatic -cells 2009 Cengage-Wadsworth