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Skelatal Muscle in Health and Disease > Ageing and skeletal muscle > Flashcards

Ageing and skeletal muscle Flashcards

1
Q

Compare lifespan and healthspan

A
  • Lifespan - how long you are alive for - life expectancy
  • Healthspan- how long are you healthy for
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2
Q

What are pro-aging factors?

A
  • Loss of renewal capacity:
  • Stem cells
  • Telomeres
  • Hormornal changes
  • Accumulation of Damage
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3
Q

What are Longevity Assurance Systems?

A
  • DNA repair
  • Stress responses
    -Antioxidant defenses
  • Protein and cell turnover
  • Mitochondrial Maintainenace
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4
Q

What is genome analysis?

A
  • Looking into 1000s of hemes
  • Single nucleotide polymorphisms (SNPS)
  • We can look at complex genetic signatures
  • Very few genes consistently involved
  • No genes associated with diseases
  • Genes do not solely governn whether you will live longer than an average lifespan
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5
Q

What is the concept of hormesis?

A
  • Something that causes harm but up to a certain point, that harm may be beneficial/ have a positive benefit e.g.g exercise
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6
Q

What are the changes in muscle mass with aging?

A
  • 40% loss in muscle mass from 20-70 years of age
  • 6% decline in muscle mass per decade from aeg 30-70
    1.4-2.5 % decline in muscle mass per year after 60
  • 6% decrease in leg muscle volume over a 5 year follow up - from 71-76 years olf
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7
Q

What is sarcopenia?

A
  • Age-associated decline in muscle mass
    Sarco = flesh, penia = deficiency
  • Asssociated with increased mortality and functional decline
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8
Q

What is the prevalence of sarcopenia?

A
  • More prevalent in females (60-75)
  • <70 -85 increase in sarcopenia in men
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9
Q

What is the catabolic crisis model?

A

Muscle catabolism leads to a loss of muscle mass. This process reduces muscle protein levels, which are essential for building and repairing muscle. The reduction in muscle mass has a negative impact on body appearance and the body’s ability to process fat and carbohydrates
- e.g. injury and bed ridden = loss of muscle , never gained back

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10
Q

What is sarcopenia?

A
  • Sarcopenia = reduced musclemass, also associated with decreased muscle quality
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11
Q

What are some cross -sectional studies for ageing muscle?

A
  • Fibre loss - denervation , apoptosis
  • Fibre atrophy
  • Ratio of type II/I goes from ~ 1.25/1 to ~0.85/1 between ages 30-80
  • Lower extremities> Upper extremities
  • Postural/locomotor> non-postural
  • Rate of loss in males > females
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12
Q

What can cause sarcopenia (satellite cells) ?

A
  • Satellite cells - central to muscle regeneration/maintainenance
  • SC content decreases with age
  • Loss of SCs is specific to type II muscle fibres
  • Currently all associative : no evidence yet that SC decline preceds sarcopaenia
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13
Q

What is motor unit remodelling?

A
  • Loss of normal innervation
  • Denervation and reinveration
  • Loss of motor neuron leaves fibres denervated
  • Denervation causes motor neuron loss
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14
Q

What are the changes in muscle metabolism with age?

A
  • Increase in mitochondrial DNA mutation
  • Decline in muscle mitochondrial protein synthesis (40%)
  • Decreased oxidative phosphorylation and ATP generation
  • Results in fatigability
  • Decline in myosin heavy chain synthesis
  • Major protein involved in ATP and conversion of chemical to mechanical energy
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15
Q

What is mitochondrial dysfunction?

A
  • Disrupted mitochondria also display abnormal function in humans
  • Lowered mitochondrial :
  • Content (overall capacity)#
  • Oxidative capacityy per mitochondrial volume
  • Mitochondrial protein concentration
  • Mitochondrial ATP production (MAPR)
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16
Q

What are the effects of ageing on muscle protein turnover?

A
  • Postabsorptove (fasting) protein balance is unchanged in the basal state in elderly
  • Acuumulation of neg effects of ageing cells may decrease muscle quality/function when protein balance is unchanged
17
Q

What are the effects of healthy aging on dose response of MPS to EAA?

A
  • Accumulation of small but meaningful decreases = leads to atrophy
    = ANABOLIC
  • Muscle protein breakdown also not suppressed after feeding in the elderly

MPS- Muscle Protein Synthesis
EAA - Essential Amino Acids (Stimulator of MPS)
FSR - Fractional synthetic rate (i.e. rate of newly made protein)

18
Q

Explain glucose metabolism in older muscle

A
  • Older muscle does not swithch to glucose metabolism in response to insulin
  • suggests that muscle is less able to dispose of glucose with age and therfore contributes to age related diabetes.
19
Q

What is dynapaenia?

A
  • Porgressive loss of muscle function during the ageing process
  • In elderly people, functional capacity is directly dependent on muscle size/ fitness
  • 65-80 yr have approc 20-40 % decline in leg maximal voluntary force production
    (MVC)
  • 50% decline in MVC with progressive age
20
Q

What is muscle strength?

A

The maximum capacity to generate force or tension declines

21
Q

What is strength loss in ageing (percentages)?

A
  • Strength increases up to age 30
  • Plateaus from age 30-50
  • Declines 24-36% betweem 50-70
  • 12% decrease in leg muscle strength over a 5 year follow up from 71-76 years old
  • Most precipitous loss after 70
  • 15% loss per decade up to 6th and 7th decades of life
  • 30% loss per dcecade thereafter
  • 35% loss over 11 year period in 80 year old subjects
  • Women unable to lift 4.5 kg (!0 ibs) increased from 40% in 55-64 year olds to 65% in those afe 75-84
22
Q

Why does the max capacity to henerate force or tension decline?

A
  • Mucsle Cross sectional area
  • MU recruitment/ Firing rate
  • Intrinsic factors
23
Q

What are mean motor unit forces?

A
  • Fast fatigable FF motor units get smaller in old age and decrease in number
  • Slow twitchs motor units get bigger with no change in number
  • Decreased rate of force generation and POWER
24
Q

Explain what happens with SKM quality with age

A
  • More fat infiltration of muscles
  • Increased fibrosis/ disorganised extracellular matrix
25
Q

What mechanisms underpin sarcopenia / dynapenia?

A
  • Genetic influence
  • Immobility
  • Muscle fibre atrophy
  • Neurodegenerative processes
  • Decreased protein synrhesis
  • Nutritional status ( decreased protein and energy intake)
  • Autophagy, Apoptosis, Mitochondria dysfunction
  • Endocrine factors (decreased GH, IGF-1, sex steroids, insulin resistance)

Skelatal Muscle in Health and Disease (16 decks)

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