Energy Balance Flashcards
What are the key hormonal systems involved in humans/animals?
- GH (insulin-like growth factor-1 = IGF-1 axis)
- thyroid hormones
- sex hormones
- androgens
- estrogens
- insulin
What other hormones have powerful modifying effect?
- cortisol
- glucocorticoids
- leptin
- progesterone
What study models can be used to study growth?
- deficiency syndromes (GH/iodine deficiency)
- over-production tumours (pituitary tumours)
- pharmacological stimulation
- nutritional interactions (under/over-feeding studies)
What is leptin from adipose tissue’s effect on?
appetite and growth
When the body cannot produce leptin, what happens?
obese
What is myostatin?
negative regulator of skeletal muscle growth
- its deletion/inhibition causes extreme muscular development in animals/humans
Why is there a need for energy balance?
for net accretion of tissues to take place and growth to occur in muscle/lean/organ/adipose tissues and bone + fat mass
What are the body composition compartments?
- body fat
- skeletal muscle mass
- organs
- water
- bones
What is body fat made up principally of?
adipose tissue made of lipids
What are organs and skeletal muscle made up of?
lean tissue made up of protein and water predominantly
What is bone tissue made up of?
minerals and some protein
What is protein turnover?
takes place everyday, continuous breakdown and renewal of protein
What must be so, for NET protein synthesis to occur?
synthesis MUST be greater than breakdown
Name the anabolic hormones having the positive effect on net protein synthesis in muscle:
- GH-IGF
- androgens
- insulin
Name the catabolic hormones having the negative effect on net protein synthesis in muscle:
- cortisol
- glucocorticoids
- proinflammatory cytokines
Name the hormones that have modulatory effects on growth and protein turnover:
- catecholamines
- thyroid hormone (major impact on fetal growth)
- estrogens
- progesterones
- leptin
- ghrelin
Name the particular amino acids that are essential for protein synthesis to occur:
- essential aa
- branched chain aa (leucine)
When the catabolic state is created during infection and illness, what does it include?
heightened proinflammatory cytokine production and cortisol
what hormone reductions are there during dietary restriction?
insulin, IGF-1, thyroid activities
What is one generic description of how nutritional intake affects hormonal status in different ways?
nutrient-gene interactions
What is the GH-IGF axis?
- major system that regulates global growth and development of tissues (bone, tissues) esp. during childhood growth/development
- both the GH and IGF-1 have major effects on tissue growth and development
- highly regulated by nutrition and other hormones too (thyroid, sex hormones, leptin, insulin)
Where is GH produced?
pituitary gland
where is IGF-1 produced?
by liver under stimulation of GH
Which has a greater anabolic impact on protein turnover, GH or IGF-1?
IGF-1
Does GH have a substantial metabolic role?
Yes
What is the local production of growth factors such as IGF-1/GH regulated by?
factors like hormones, nutrition and exercise
When GH is produced, what does it affect?
hepatic and local production of IGF-1 (autocrine and paracrine)
What are the effects of dietary restriction on GH-IGF axis?
- along with stress, can increase GH release (to increase fat mobilisation, lipolysis)
- downstream problem
- loss of IGF production + activity
- alteration in IGF binding proteins = affects clearance and cellular activity
Meat is a bioavailable source of?
protein, essential amino acids and other nutrients
What are critical factors in meat production?
feed efficiency and growth rates
What are beta-adrenergic agonists?
bind selectively to beta adrenergic receptors in tissues
- modelled on adrenaline/noradrenaline
- sympathomimetic amines
Give an example of beta-adrenergic agonists?
classical asthma drugs
salbutamol
What are beta-agonists used usually in?
classically used in farm animal research studies and meat production
What are some types of beta-agonists?
- cimaterol
- clenbuterol
- ractopamine
What is the beta 2 receptor’s effect on?
potent effect on fat loss in adipose tissue and protein gain in muscle
What is the effect of BAA (beta-adrenergic factor) on fibre?
there’s switch in fibre type from slow to fast WITH chronic administration
Explain the nutrient repartitioning concept:
- drugs/BAA affect lipid and protein metabolism
- energy is diverted from fat towards muscle
- basically, decreased synthesis in adipose tissue (fatty acids, glycerol, triglycerides involved), but increase for skeletal muscle tissue (amino acids and proteins involved)
- degradation for adipose increase but opposite for muscle tissue
The effects of BAA administration are?
- reducing adipose tissue mass, lipogenesis, protein breakdown, but
- increase lipolysis, muscle mass, protein synthesis
Explain the mechanism of ß-adrenergic receptor signal transduction:
- receptor activated by agonist and interacts with Gs proteins
- Gs proteins stimulate adenylyl cyclase to convert ATP to cAMP
- Increased cAMP activates protein kinase A (PKA) to phosphorylate enzymes + regulatory factors = metabolic regulation
What is the usual duration period of BAA treatments?
desensitisation over 2 week period
Explain the dosages of BAA treatments:
- asthma drugs low dose
- higher dose = better gains
Which muscle fibre types do BAA have specific effects on?
- fast twitch fibres
- causes transition of fibre types
What has BAA treatment been considered for?
- muscle wasting (muscular dystrophy, cancer cachexia, AIDS)
- it antagonises DEX
