W2 - Metabolic effects of hormones & cytokines during exercise Flashcards
Define Metabolism
the biochemistry in the cell to keep the e.g.: muscle functioning
Name some hormones which are effecting during exercise
- Glucagon
- Insulin
- Adrenaline
- Steroid/sex hormones
Where are the MAIN hormones in the body? Where are they produced?
- Adrenaline - adrenal glands
- Thyroid hormones - thyroid glands
- Pancreas - Insulin
- Muscles & Adipose tissues - cytokines (very metabolically active in their endocrine function)
What are the main functions of hormonal changes during exercise
- Maintain blood pressure
- Redistribution of blood to working
muscle - Increase fuel mobilisation: glucose and free fatty acids (FFA)
- Maintain blood glucose concentration
Name the hormones which rise during exercise:
Name the hormone that is reduced in production during exercise:
+ adrenaline (vasomotor tone, heart rate & contractility)
+ noradrenaline (above & lipolysis, glycogenolysis)
+ cortisol (Gluconeogenesis, anti-inflammatory)
- Insulin (lipolysis, liver glucose release)
Name some examples of steroid hormones?
cortisol, progesterone, testosterone, aldosterone
Describe how steroid hormones(lipid soluble) cross a cell membrane and form a protein
- Steroid Hormone enters cell
- Hormone binds to specific receptor in cytoplasm/in nucleus
- Hormone receptor complex activates the cell’s DNA = forms RNA
- The mRNA leaves the nucleus & enters the cytoplasm
- The mRNA directs protein synthesis in the cytoplasm
Hormone at beginning –> Protein at end
* e.g.: testosterone, Progesterone, cortisol
Explain how non-steroid hormones cross a cell membrane and create hormonal effects
- Nonsteroid hormones can’t pass through the cell membrane
- Hormone binds to specific receptor on the cell membrane
- The hormone receptor complex activates adenylate cyclase within cell membrane
- Adenylate cyclase catalyses the formation of cAMP
- cAMP activates protein kinases (enzymes) that lead to cellular changes & hormonal effects
- second messengers: cAMP, cGMP, IP3
- e.g.: Adrenaline, Insulin
What is insulin?
- Insulin regulates glucose entry into tissues
- Insulin insensitivity (→ Diabetes): inability to control blood glucose levels
- Neurones are dependent on blood glucose e.g.: brain cells, which can cause problems with neurones
- Can be used as a murder weapon: Insulin shock
What hormone inhibits insulin secretion and why?
Adrenaline inhibits Insulin secretion during exercise → increasing a cells’ sensitivity to insulin
○ More glucose is therefore present in blood stream for muscle cells
○ Insulin causes glucose uptake into cells
○ For same concentration of insulin MORE glucose can be taken up into the cell (insulin sensitivity)
○ A healthy lifestyle helps to increase cell insulin sensitivity
What are insulins effect of blood vessel size?
- Insulin creates a vasodilation action
- Insulin induces greater blood flow to e.g.: muscle cells
- Action via nitric oxide (NO)
What is the role of glucagon?
How is it’s release stimulated?
Where is it released from?
- Increases blood glucose levels but stimulating the breakdown of glycogen (glycogenolysis) in the liver.
- Promotes the formation of glucose from non-carbohydrate precursors (gluconeogenesis) in the liver.
- Glucagon has the opposite effect to insulin
- Stimulated by the fall in blood glucose levels
- Released by a cells of the pancreas
What effect does insulin have on GLUT4 transporters?
What is the role of GLUT4?
- Insulin signalling changes the concentration of glucose transporters at the cell membrane
- GLUT4 acts on the cell membrane of muscle and adipose tissue
- translocation to cell membrane from intracellular space
- Muscle contraction independently can move the GLUT transporter to the membrane
Describe the hormonal activation of glycogenolysis
Adrenaline turns ATP into cAMP, which can trigger reactions
- Kinase puts a phosphate group onto another cell
- Changes the cell from being inactive to active
- Allows for 1 glucose molecule to be broken off from a chain of glycogen e.g.: a liver cell
- Releases glucose into the muscle, which can be taken up by muscles for contraction
- Adrenaline is involved when bringing glucose OUT the cell (gluconeogenesis) & lipolysis in adipose tissue
- Insulin can convert cAMP to AMP (change the reaction)
Explain the hormonal activation of lipolysis
- when adrenaline converts ATP into cAMP, it causes an onset of multiple reactions
- Active HSL when activated can breakdown fat
- FFA into blood stream
- FFA in blood stream can be used for energy in cell when taken up
- Insulin can convert cAMP to AMP (to keep energy dense molecules in cells)
What are the intracellular factors that are involved in muscle glycogen breakdown and glycolysis during exercise?
Intracellular factors
* Increased Ca2+
* Increased AMP and Pi
* Decreased ratio of ATP:ADP
* Decreased PCr
* Increased fructose 6-phosphat
What hormones involved in muscle glycogen breakdown and glycolysis during exercise
- increased adrenaline and noradrenaline
- decreased insulin
- increased glucagon
How does the multitude of the hormonal influence differ in contracting to non-contracting muscles during exercise?
- Glycogen breakdown in non-contracting muscles(exposed to hormonal changes) is NOT significant compared to contracting muscles(because they are metabolically active)
How do intracellular factors change enzyme function?
Name some activators
Name some inhibitors
These are molecules produced in a cell with a capacity to activate or inactivate enzymes by binding to binding to allosteric sites
- e.g.: Phosphofructokinase (phosphorylates fructose 6-phosphate in glycolysis
- Activators: AMP, Pi, ADP
- Inhibitors: ATP PCr
What are the mechanisms of changed hormone secretion during exercise?
CNS:
- Metaboreceptors in working muscles
- Thermoreceptors
- Motor centres of brain
- Fall in blood glucose (glucagon)
Hypothalamus:
- Pituitary gland (ACTH, vasopressin, cortisol)
Increased SNS activity:
- nor/adrenaline, renin, aldosterone
How do hormonal changes during exercise act on the kidney?
- Increased WATER and SODIUM retention
- Helps to maintain blood volume and change blood pressure
–> INCREASE vasopressin (from pituitary) = helps retain water
–> INCREASE aldosterone (from adrenal cortex) = helps to retain sodium
- Helps to maintain blood volume and change blood pressure
What are cytokines?
○ Secreted molecules that can cause specific effects both on the cell that they are secreted (autocrine effects) and on other cells (paracrine effects)
* Cytokine: cell- movement
* Interleukin (IL): communication between leukocytes
* Messenger molecules to communicate between (white blood) cells, important in cell signalling
How are cytokines different to hormones?
- Both are secreted into circulation and modify the behaviour of cells elsewhere
– Cytokines- Proteins
- Originally in white blood cells (→interleukins), but secreted by other tissues
– Hormones
* Can be proteins e.g. insulin, testosterone/ FA derivatives
* Produced by specific cells (e.g. insulin by pancreas, adrenaline by adrenal glands etc.)
What can the anti-inflammatory effects of exercise lead to?
- Decrease in visceral fat accumulation(lipolysis and fat oxidation)
- Decreased inflammation (ageing)
- Decreased chance of Chronic disease: diabetes, CVD
What role does IL-6 play at rest?
- Reduces resting levels of inflammation (tested through inflammatory markers in the blood)
- IL-6 increase triggers increase in anti-inflammatory cytokines
- IL-6 released into blood when strenuous exercise is taking place
—-> this triggers inflammation, from contracting myofibers
—->Induces an increase in other (inflammatory) cytokines - Prevents CVD, diabetes etc. as they are all associated with inflammation
What are the metabolic actions of IL-6?
Increased:
- Glycogenolysis
- Lipolysis
- Fat oxidation
- Triacylglycerol
(decreased: type 2 diabetes, athesclerosis and autoimmune disease)
What are the anti-inflammatory actions of IL-6?
Increased:
- IL-10
- cortisol
- TNF-α
When is IL-6 produced?
More IL-6 produced when there is a NEED for energy
Induces an anti-inflammatory environment
What are the factors affecting the magnitude of hormonal response to exercise?
Intensity of exercise increases
* Duration of exercise increases
* Increase body temperature
* Psychological stress increases
* Hypoxia (altitude) increases
* Nutritional status (more with fasting)
