Lecture 9: skeletal muscle energetics and ageing Flashcards
VO2 max = maximal oxygen consumption at maximal exercise intensity. = measure of endurance exercise capacity.
X with ageing and parallels the X
Declines , maximal heart rate
“Are muscle mito’s involved in the age-related decline in VO2 max?”
Nobody knows for sure. However, skeletal muscle mito density is related to VO2 max (association)
Q: “An important process in ATP production is oxidative phosphorylation. What about it?”
A: (1) it is the only process in energy metabolism that produces ATP
(2) It is the only process in energy metabolism that consumes oxygen
(3) It requires several protein complexes located in the outer mito membrane
(4) All of the above
(2)
bc answer 3 should be ‘ inner membrane’
Better phrasing of (2) would be ‘the primary process’
Because ox phos is main oxygen user, A measure of X is therefore a measure of ox phos
oxygen consumption
How can mito function be measured ex vivo?
By high resolution respirometry. Measures disappearance of oxygen from the medium (e.g. permeabilized muscle fibers)
Ageing is associated with decreased mitochondrial density in muscle, both in mice and humans
ok
Various, but not all ex vivo studies using muscle biopsies indicate lower expression of … in older subjects
mito proteins
Q: “Besides an increased mito capacity, what other factor could improve (muscle) aerobic capacity?”
A: (1) An increased total lung volume
(2) An increased density of capillaries in the muscle
(3) A high blood glucose level
(4) All of the above
(2) An increased density of capillaries in the muscle
Capillary to muscle fiber ratio determines X
X = exercise endurance capacity
“What is PGC-1alfa?”
A transcriptional coactivator, involved in the regulation of mito functioning
PGC-1alfa: content is higher in high-functioning elderly, related to complex 4 activity. It is also higher in…
walking speed in high-vs low functioning elderly
So, human ageing is associated with decreased (Aerobic) energetic capacity of skeletal muscle by:
lower mito density
lower mito oxidative capacity
lower capillary-to-fiber ratio
lower PGC-1alfa
decreased (Aerobic) energetic capacity of skeletal muscle may negatively impact..
VO2 max
Gait speed
What stimulates PGC-1alfa?
Exercise
What plays an important role in PGC-1alfa + exercise?
AMPK connects PGC-1alfa with exercise. During exercise, you consume ATP. AMPK is upregulated > upregulation TGC-1alfa. See image p.33
Exercise training improves mito density, ox capacity and capillarization
true/false
true
PCr is used during the initial phase of exercise (first 20 s) to produce ATP. Post-exercise recovery of PCR: explain
ATP is needed again to refill PCr storage → depending on oxidative metabolic pathways → reflects mitochondrial oxidative functioning
Immediately after exercise, muscle O2 consumption remains transiently elevated to restore PCr levels. Higher mito capacity will result in a ..”
A: “Faster recovery of muscle O2 consumption and PCr”
How can you locate phosohocreatine-containing compounds?
magnetic resonance spectroscopy (MRS).
Different muscles possible
How can you determine mito ox functioning with MRS?
post-exercise revovery of PCR -> depending on ox phos -> reflects mito ox functioning
Do all skeletal muscle groups have this post-exercise PCr delayed recovery?
No
What can you measure with NIRS?
whether there is more oxygenated or deoxygenated haemoglobin.
Decline in oxygenated Hg, reflects decline in ox phosph
what would happen if we (transiently) occlude the muscular blood flow completely in terms of NIRS?
Oxy-Hb signal will go down, deoxy-Hb signal will go up
NIRS protocol:
- Exercise, to deplete Pcr stores
- After exercise, body increases ox consumption to restore Pcr
- Slope reflects oxygen consumption (same curve as with Pcr)
So, mito ageing affects skeletal muscle energetics:
decrease in ..
mito density
mito enzyme expr
mito ox capacity
capillarization
Are the ageing effects in skeletal muscle energetics modulated completely by physical activity?
No, suggesting they are (partially) inherent
