Lecture 9: skeletal muscle energetics and ageing

Question 1

VO2 max = maximal oxygen consumption at maximal exercise intensity. = measure of endurance exercise capacity.

X with ageing and parallels the X

Answer 1

Declines , maximal heart rate

Question 2

“Are muscle mito’s involved in the age-related decline in VO2 max?”

Answer 2

Nobody knows for sure. However, skeletal muscle mito density is related to VO2 max (association)

Question 3

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

Answer 3

(2)
bc answer 3 should be ‘ inner membrane’

Better phrasing of (2) would be ‘the primary process’

Question 4

Because ox phos is main oxygen user, A measure of X is therefore a measure of ox phos

Answer 4

oxygen consumption

Question 5

How can mito function be measured ex vivo?

Answer 5

By high resolution respirometry. Measures disappearance of oxygen from the medium (e.g. permeabilized muscle fibers)

Question 6

Ageing is associated with decreased mitochondrial density in muscle, both in mice and humans

Answer 6

ok

Question 7

Various, but not all ex vivo studies using muscle biopsies indicate lower expression of … in older subjects

Answer 7

mito proteins

Question 8

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

Answer 8

(2) An increased density of capillaries in the muscle

Question 9

Capillary to muscle fiber ratio determines X

Answer 9

X = exercise endurance capacity

Question 10

“What is PGC-1alfa?”

Answer 10

A transcriptional coactivator, involved in the regulation of mito functioning

Question 11

PGC-1alfa: content is higher in high-functioning elderly, related to complex 4 activity. It is also higher in…

Answer 11

walking speed in high-vs low functioning elderly

Question 12

So, human ageing is associated with decreased (Aerobic) energetic capacity of skeletal muscle by:

Answer 12

lower mito density
lower mito oxidative capacity
lower capillary-to-fiber ratio
lower PGC-1alfa

Question 13

decreased (Aerobic) energetic capacity of skeletal muscle may negatively impact..

Answer 13

VO2 max
Gait speed

Question 14

What stimulates PGC-1alfa?

Answer 14

Exercise

Question 15

What plays an important role in PGC-1alfa + exercise?

Answer 15

AMPK connects PGC-1alfa with exercise. During exercise, you consume ATP. AMPK is upregulated > upregulation TGC-1alfa. See image p.33

Question 16

Exercise training improves mito density, ox capacity and capillarization
true/false

Answer 16

true

Question 17

PCr is used during the initial phase of exercise (first 20 s) to produce ATP. Post-exercise recovery of PCR: explain

Answer 17

ATP is needed again to refill PCr storage → depending on oxidative metabolic pathways → reflects mitochondrial oxidative functioning

Question 18

Immediately after exercise, muscle O2 consumption remains transiently elevated to restore PCr levels. Higher mito capacity will result in a ..”

Answer 18

A: “Faster recovery of muscle O2 consumption and PCr”

Question 19

How can you locate phosohocreatine-containing compounds?

Answer 19

magnetic resonance spectroscopy (MRS).
Different muscles possible

Question 20

How can you determine mito ox functioning with MRS?

Answer 20

post-exercise revovery of PCR -> depending on ox phos -> reflects mito ox functioning

Question 21

Do all skeletal muscle groups have this post-exercise PCr delayed recovery?

Answer 21

No

Question 22

What can you measure with NIRS?

Answer 22

whether there is more oxygenated or deoxygenated haemoglobin.
 Decline in oxygenated Hg, reflects decline in ox phosph

Question 23

what would happen if we (transiently) occlude the muscular blood flow completely in terms of NIRS?

Answer 23

Oxy-Hb signal will go down, deoxy-Hb signal will go up

Question 24

NIRS protocol:

Answer 24

1. Exercise, to deplete Pcr stores
2. After exercise, body increases ox consumption to restore Pcr
3. Slope reflects oxygen consumption (same curve as with Pcr)

Question 25

So, mito ageing affects skeletal muscle energetics:

Answer 25

decrease in ..

mito density
mito enzyme expr
mito ox capacity
capillarization

Question 26

Are the ageing effects in skeletal muscle energetics modulated completely by physical activity?

Answer 26

No, suggesting they are (partially) inherent