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Muscle & Exercise Physiology > Lecture 25 - Growth-promoting agents for skeletal muscle > Flashcards

Lecture 25 - Growth-promoting agents for skeletal muscle Flashcards

1
Q

Medical applications of anabolic agents is important for treatment of many diseases including…

A 
MDs
HIV-AIDS
cancer cachexia
ageing (sarcopenia)
sepsis
denervation
plaster casting 
enhancing regeneration after muscle injury
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2
Q

What are the hormonal therapeutic agents?

A

GH, testosterone, DHEA, SARMs

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3
Q

What are the hormonal therapeutic agents?

A

IGF-1, IL-15, TGF-Beta

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4
Q

What are the other growth promoter agents?

A

beta2-agonists

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5
Q

What is an Ergongenic aid?

A

Allows the bosy to train/perform at a higher level

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6
Q

What is the effect of endogenous levels and exogenous administration of testosterone?

A

endogenous levels

  • responsible for male phenotype
  • promotes bone and muscle growth

exogenous administration
- stimulates muscle protein synthesis

There are also synthetic analogues of testosterone and their precursors: nandrolone, oxandrolone, stanozolol

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7
Q

androgenic -anabolic steroids are synthetic derivatives of ______ capable of exerting strong effects on the body that can benefit athletic performance

A

androgenic -anabolic steroids are synthetic derivatives of testosterone capable of exerting strong effects on the body that can benefit athletic performance

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8
Q

True or false

testosterone replacement has been used to counteract loss of lean body mass in hypogonadal men, in older men with normal or low serum testosterone and HIV-infected men with low serum testosterone

A

true

muscle growth achieved

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9
Q

What are the Direct mechanisms of action for androgenic -anabolic steroids ?

A

Androgen receptor

  • located in skeletal muscle
  • stimulated by testosterone and DHT

receptor stimulation causes: increase in protein synthesis and therefore increase in muscle mass

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10
Q

What are the indirect mechanisms of action for androgenic -anabolic steroids ?

A

modulate gene expression of autocrine and paracrine mediators via other receptors (IFG-1)

Alter secretion of other hormones that suppress skeletal muscle growth - cortisol

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11
Q

What are the potential benefits of androgenic -anabolic steroids use?

A

Muscle hypertrophy
- increased protein synthesis

Ca2+ deposition in bones

lipolysis - increased lean body mass

increased RBC production - greater oxygen carrying capacity

motivation

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12
Q

what are the levels of testosterone administration and endogenous levels?

A

endogenous levels - 7mg testosterone/day

medicinal 4-10 mg/day

females
medicinal 0.04-0.12 mg/day

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13
Q

some studies have demonstrated enhanced muscle strength following testosterone administration, but other have reported…

A

n effect of androgen therapy on muscle function despite increases in muscle size

although anabolic steroids have been used for the treatment of HIV-related wasting and other wasting conditions for many years, many questions remain unanswered

e.g what are appropriate and safe doses for long-term administration and what are the associated potential risks or side-effects

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14
Q

What are the potential medical consequences of testosterone abuse?

A

at 100-350+ mg/day

liver dysfunction
testicular atrophy
increased body hair

male pattern baldness

gynaecomastia

acne

reduced HDL cholesterol levels

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15
Q

The abuse of testosterone in sports undermines the…

A

potential theapeutic applications

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16
Q

Where is growth hormone released from endogenousl and what inhibits it?

A

the ant. pituitary

somatostatin inhibits GH release

17
Q

What is the mechanism of action of GH and its effects?

A

GH binds two receptors resulting in dimerisation

  • causes the release of somatomedins = IGF-1
Effects
- lipolysis
increase lean body mass
- bone growth
protein accretion

rhGH(synthetic) has the same effect

18
Q

Is there clinical evidence for increased performance, bone strength and decreased body fat for GH in sport?

A

No

19
Q

True or false

rhGH is indistinguishable from GH

A

true

banned by IOC, but undetectable

20
Q

What are the side effects of GH excess?

A

gigantism (pre-puberty)

acromegaly (post-puberty)

organomegaly

hypertension (increase Na reabsorbtion)

Collagen deposition

21
Q

what is the therapeutic potential of GH?

A

improves muscle structure

mscuel function

numerous side effects
limited therapeutic potential

22
Q

true or False

GH has been used by athletes since the 1980s to improve performance despite being banned for many years and appearing on the WADA list of banned substances

A

True

the actions of GH that interest athletes are anabolic and lipolytic

some of the anabolic GH actions are mediated through the generation of IGF-1 and there is anecdotaed evidence that this too is being abused by athletes either alone or in combination with GH

23
Q

What does IGF-1 do?

A

growth factor with structural homology to insulin

involved with normal growth and repair of muscle

mediates action of GH

mechanism of Action:
Binding of IGF-1 to receptor
- increases protein synthesis
Decreases protein degradation 
increase Muscle mass
24
Q

How is IGF treated wrt sport?

what are its potential therapeutic benefits?

A

expensive (10,000 for 50mg)

does incerase muscle mass, strength and oxidative capacity

hence banned by the IOC

25
Q

What are the thrapeutic benefits for Beta-agonists for sarcopenia?

A

increase muscle mass, Fibre size, absolutele force-producing capacity

cause slow-to-fast muscle fibre transitions (which causes hypertrophy)

enhance muscle repair after damage

26
Q

Beta-adrenoceptor agonists (beta agonsits) are used for what?

A

used traditioanlly as bronchodilators for treating asthma, some have powerful anabolic effects on muscle however (when taken in higher doses and systemically rather than inhalation)

27
Q

what is the mechanism of action of Beta-agonists?

A

acts through Pi3K/AKT and PKA

28
Q

Increased levels of adrenergic stimulants reduces the response, how?

A

Desensitisation = same adrenoreceptor number but decreased receptor function

downregulation = decrease in adrenoceptor number, but same receptor fucntion

29
Q

Can we separate the beneficial effects on skeletal muscle from those (delerious effects) on the heart?

A

all of these can be factors to deal with the CV side effect

choice of beta-agonists (clenbuterol is old, there are newer versions)
dosage
duration of treatment
mode of adminsitration

30
Q

what family of receptors are beta-adrenoreceptors a part of?

A

G-protein coupled receptors (GPCRs)

31
Q

True or False

currently in development, a synthetic receptor and an activator neither of which activates or impairs endogenous signalling

A

true

RASSLs and DREADDs - still in early phases of development

limits signalling to the tissue/region of interest - a result that current beta-agonists cannot achiebe

Muscle & Exercise Physiology (34 decks)

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