ageing in skeletal muscle part 2: contributors to Sarcopenia

Question 1

what 2 things are Satellite cells central for in muscle?

Answer 1

1. regeneration
2. maintaince

Question 2

satellite cells

what are SC cells for and what type of loss is loss of SCs specific for?

Answer 2

• SC cells are for muscle regeneration/maintainance
• loss of SCs is specific to type II muscle fibres

Question 3

motor unit remodelling

what are ALL muscle fibres invervated by in healthy muscle?

Answer 3

• myelinated motor axons/neurones

Question 4

outline what happens to muscle fibres when loss of motor neurones and denervation occurs in 3 steps

Answer 4

1. loss of motor neurones leaves fibres denervated
2. denervation causes motor neurone loss
3. denervation induced fibre atrophy and potential loss occurs

Question 5

what can a different motor neurone do if muscle fibres undergo denervation from their original motor neurones? and what does this sacrifice?

Answer 5

a different motor neurone can re-innervate the muscle fibres that lost their original motor neurones

• this can sacrifice fine motor control

Question 6

changes in muscle metabolism with age

what 2 things can cause decline in muscle mitochondrial protein synthesis, what does this lead to in elderly and what percentage does that decrease in age

Answer 6

Causes:
- decreased oxidative phosphorylation and ATP generation

• Fatigability

can be 40% decline

Question 7

changes in muscle metabolism with age

what are 3 changes in muscle metabolism with age

think mitchondria and myosin

Answer 7

• increase in mitochondrial DNA mutation
• decline in muscle mitochondrial protein synthesis
• decline in myosin heavy chain synthesis

Question 8

what is the major protein involved in ATP and conversion of chemical energy to mechanical energy?

Answer 8

myosin heavy chain

Question 9

what 4 things can mitochondrial dysfunction lead to?

Answer 9

lowered mitochondrial:
- content (capacity)

• oxidative capacity per mitochondrial volume
• mitochondrial protein concentration
• mitochondrial ATP production (MAPR)

Question 10

effects of ageing of muscle protein turnover

True or False, postabsorptive (fasting) protein balance is unchanged in the basal state in the elderly?

Answer 10

True protein balance/turnover is unchanged

Question 11

effects of ageing on muscle protein turnover

what is “anabolic blunting”

Answer 11

accumulation of such small but functionally meaningful decreases inmuscle protein synthesis and essential amino acids that lead to atrophy.

Question 12

MPB insensitivity to insulin with ageing

True or false, Muscle protein breakdown is not suppressed after feeding in the elderly

Answer 12

True, MPB is NOT suppressed after feeding in the elderly

Question 13

what does insulin do to muscle protein breakdown

Answer 13

it inhibits muscle protein breakdown

Question 14

dynapaenia

Define Dynapaenia

Answer 14

The progressive loss of muscle function (eg: strength and power) during the ageing process

Question 15

dynapaenia

what is functional capacity directly dependent on in elderly people?

Answer 15

• directly dependent on muscle size/fitness

Question 16

how much of a decline in leg maximal voluntary force production (MVC) do people usually have between 65-80

Answer 16

between 20-40% decline in leg MVC

Question 17

strength loss with aging

when does strength increase up to, when does it plateau and when does it decline and by how much?

Answer 17

• increases up to age 30
• pleateaus from age 30-50
• declines 24%-36% between age 50-70

Question 18

muscle strength

what 3 reasons does muscle strength decrease

think size, MU and hormones

Answer 18

• decrease in muscle Cross-sectional area
• decrease in MU recruitment or lower quality in firing rate
• intrinsic factors like lower testosterone in body

Question 19

what is the equation of power

Answer 19

power = work or STRENGTH / Time

/ means divide

Question 20

mean motor unit forces

what happens to fast fatigable (FF) [Type II] motor units in old age?

Answer 20

they get smaller and decrease in number

Question 21

mean motor unit forces

what happens to slow twitch (S) motor units as you age?

Answer 21

• they get bigger with NO change in number

Question 22

what 2 things can fat infiltration of skeletal muscle cause which contributes to decrease in muscle quality?

Answer 22

can cause:
- increased fibrosis
- disorganised extra-cellular matrix

Question 23

what is the FOXO transcription factor

Answer 23

a transcription factor that activates transcription of genes that inhibit cell proliferation