Substrates6pp - Intensity Substrates for Activity As...

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1 Substrates for Activity Intensity z As intensity increases, we rely more heavily on carbs z RQ goes up 0% 20% 40% 60% 80% 100% relative contributions to exercise glycogen pl glucose other fats ffa From van Loon et al , J Physiol (2001)536.1, pp. 295-304 40% 75% 55% Intensity of maximal workload Intensity Intensity Duration Short term activity Anaerobic vs aerobic
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2 Duration Uptake of oxygen and nutrients by legs, orange is intramuscular sources Duration z Initial fuel relies on muscle glycogen then liver starts putting out glucose (initial is from glycogenolysis then gluconeogenesis) 0 50 100 150 200 250 300 350 Grams Storage Muscle Liver Blood 100 kcals 25 g Blood 300-400 kcals 75-100 g Liver 1200-1600 kcals 300-400 g Muscle Glycogenolysis Debranching enzyme Glycogen phosphorylase phosphoglucomutase Glucose-6 phosphatase Gluconeogenesis z Almost a reversal of glycolysis, but what about those one way arrows? z Glucokinase/hexokinase z Phosphofructokinase z Pyruvate kinase z Why does this happen? z Glucose-6-phosphatase z Fructose 1,6-bisphosphatase z Pyruvate carboxylase and phosphoenolpyruvate carboxykinase (PEPCK) z Pyruvate carboxylase requires biotin as coenzyme α -kg glutamate Glucose-alanine cycle
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3 Cori cycle Training state z muscle glycogen depends on training status mmol/kg wwt 210-230 trained, carb loading 130-135 trained 80-90 untrained Up-regulation of enzymes Endurance adaptations z increase cardiac output and allow for better extraction of oxygen at tissue level to favor glycogen sparing and fat burning z will not accumulate lactic acid at same intensity as untrained, higher blood lactate threshold allows for more fat utilization z increases capillary and mitochondrial density z increase activity of glycogen synthase z increased IM lipid stores Carbohydrate z Factors to determine CHO utilization for exercise: z intensity z duration z training state z diet composition/metabolism Carbohydrates- how we can maximize z Digestion z Mouth z Stomach z SI: Duodenum z Pancreatic z Brush border z Large intestine
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4 Absorption LI: Fermentability of dietary fibers z More fermentable fibers z Pectins z Beta-glucan z Some hemicelluloses z FOS, other oligosaccharides z Gums, mucillages z Resistant starch z Polydextrose z Lactose/lactulose z Less fermentable fibers z Cellulose z Methylcellulose is key ingredient in Citrucel z Some hemicelluloses z Lignins Glucose transporters z GLUT family (14 family members total, only highlights presented) z GLUT 1 (blood brain barrier, erythrocytes) z Gets glucose across blood brain barrier z Erythrocytes dependent on glucose (no mitochondria) z GLUT 2 z GLUT 2 is part of blood glucose sensing mechanism of pancreatic beta-cells z Gets glucose out of intestinal cells (basolateral membrane) z liver z GLUT 4 z the main glucose transporter for skeletal muscle and adipose tissue z Requires insulin! GLUT receptors continued
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Substrates6pp - Intensity Substrates for Activity As...

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