Hormone regulation during exercise Flashcards
What are the sizes of the different stores of energy in the body?
Triglyceride= 400mj
Usable protein = 100mj
Liver glycogen= 2.4mj
Blood glucose= 0.16mj
Daily needs= 12mj
What are the factors that are affecting fuel use?
- Fat is more dense, 10 times as much energy per gram (wet weight), best long term store
- Fats can ONLY be metabolised aerobically, ATP production is intrinsically slow, can’t meet high energy demands
- Fats power gentle “routine” physical activity, shift towards aerobic oxidation of carbohydrates as work rate rises.
- Anaerobic glycolysis is used at the highest work rates, but these can only be sustained for very short times.
What are the main hormones involved in the control of energy use?
Insulin, glucagon/adernaline, growth hormone, cortisol, TNF-a and IL-1
How is AMP made?
ADP + ADP —> ATP +AMP
What does increased levels of AMP indicate?
[AMP] is a sensitive indicator of cellular energy stress, activates AMPK
How is cAMP made?
ATP –> cAMP +PP
What is the reaction that created cAMP catalysed by?
This is catalysed by adenylate cyclase and is a second messenger for some G-protein coupled receptors, activates PKA
What is the role of AMP kinase?
It controls fuel use
How does cyclic AMP work?
Cyclic AMP is a Second Messenger
Hormone binding activates a G-protein
G-protein activates adenylate cyclase
[cAMP] rises
Protein Kinase A activated and activates other proteins
Glucagon and β-adrenergic receptors act in this way
What is the effect of inulin on the muscle, adipose tissue and liver?
MUSCLE Enhances -glucose uptake by GLUT 4 -Glycogen synthesis -glycogenesis -amino acid uptake -enhance protein synthesis
Inhibits
- gluconeogenesis (protein degradation)
- glycogenolysis
ADIPOSE Increase glucose uptake but GLUT 4 Increase lipogenesis decrease lipolysis Decreases FFA release
LIVER Increase glycogen synthesis Increase Lipogenesis Increases protein synthesis Decrease gluconeogenesis Decreases glucose release Decreases glycogenolysis
What is the effect of glucagon on the muscle, adipose tissue and liver?
MUSCLE
No effect
ADIPOSE
Increased lipolysis
LIVER
Decreased glycogen synthesis
Increased glycogenolysis
Increase gluconeogenesis
What is the effect of epinephrine on the muscle, adipose tissue and liver?
MUSCLE
Increased glycogenolysis
ADIPOSE TISSUE
increased lipolysis
LIVER
decreased glycogen synthesis
increased glycogenolysis
increased gluconeogenesis
How does the uptake of glucose controlled?
Exercise increases insulin sensitivity, and independently stimulates vesicle recycling.
What is the action of glucagon?
Binds to the glucagon receptor in the liver and adipose tissue.
Activates second messenger signalling via cAMP.
Activates protein kinase A.
What two pathways does glucagon act to control?
- Stimulates breakdown of hepatic glycogen.
2. Activates hepatic gluconeogenesis
How does glucagon work?
Glucagon binds to a receptor causing GTP exchange which activated AMP cyclase which creates cAMP which creates protein kinase A which leads to gluconeogenesis and glycogen breakdown
When are catecholamines secreted?
Secreted from the medulla of the adrenal gland in response to sympathetic nervous system stimulation
Secreted in response to low blood glucose, exercise and fear. Relative exercise has to be >50% VO2 max.
What effects do catecholamines have on the body?
Systemic effects throughout the body, including stimulation of heart rate contractility and alteration of blood vessel diameter.
What is the overall action of adrenaline?
Stimulates use of glucose in the muscles but production of glucose in the liver
Stimulates lipolysis and fat uptake by muscles
Large range of physiological effects all supportive of exercise
Two different receptors which act via different mechanisms
Suppresses the release of insulin and stimulates the release of glucagon
Dominant hormone during intense exercise
How is fat released as a fuel source?
Cannot be made available through anaerobic metabolism at high rates but is released fairly slowly in the process of being converted to CO2 and H2O.
What is lipolysis?
The breakdown of triglycerides into fatty acids and glycerol components.
What controls lipolysis and how is it activated?
Initial reaction is catabolised by a hormone sensitive lipase.
Adrenaline and glucagon raise cAMP levels, activating protein kinase A, which phosphorylates and activates hormone sensitive lipase.
Insulin signalling counteracts this to lower levels of cAMP – to inhibit lipase activity.
What is released under extended stress?
Cortisol
What is the biochemistry of cortisol?
-Steroid hormone produced by the adrenal cortex when stimulated by the polypeptide ACTH from the anterior pituitary
-Acts upon the nucleus of cells in response to stressful situations, exercise, injury, infection, lack of food
Immunosuppressive
