Lecture 22 - Skeletal muscle mass: mechanisms of hypertrophy

Question 1

having an episode of acute major disease has a huge impact on…

Answer 1

exercise capacity in the years following

all daily activities will be completed at a higher intensity, more easily tired etc…

a downward spiral

Question 2

How can you measure AAs in the body and work out if they are being oxidised?

Answer 2

continuous infusion of 13C-labelled AAs

measure the ratio of labelled/unlabelled in plasma

measure 13CO2/12CO2 ratio in breath

More 13CO2 in breath means more oxidation of infused tracer?

Question 3

How is whole-body protein synthesis and breakdown measured?

Answer 3

constant infusion of labelled AA

measure plasma tracer enrichment against time

At a certain point the increase in labelled AA in the plasma will plataeu

The whole body protein metabolism can be determined from this (not sure if need to know the specifics)

Question 4

The ____ contributes most to whole body protein turnover

Answer 4

muscle

despite the fact that other tissues, liver etc.. have a high synthesis rate

Question 5

Protein synthesis and breakdown rates are not constant during the day, they are highly responsive to:

Answer 5

Food intake - protein, CHO, fat

Exercise

Inflammatory signals

hormones

Question 6

With resistance exercise there is a __% increase in protein synthesis after exercise (3 hours)

Answer 6

100

remain elevated for 48 hours

Question 7

True or false

mixed muscle protein synthesis is reduced during exercse

Answer 7

true

but increased for >24h post-exercise in untrained individuals

Question 8

Resistance exercise increase ______ and _______ protein synthesis

Answer 8

myofibrilar and sarcoplasmic protein synthesis

Question 9

true or false

Mitochondrial protenin synthesis rate

Answer 9

false, other way around

a

Question 10

mitochondrial protein synthesis is favoured in ____ exercise

Answer 10

endurance

Question 11

Exercise training alters the acute response to exercise

Answer 11

that different signalling pathways are activated

Question 12

Increase muscle protein synthesis (MPS) could be achieved through which two means?

Answer 12

Increasing transcription of mRNA which in turn will lead to protein synthesis

or modify existing mRNA and influence at the translational level

Question 13

True or False

Increased translation seems to drive increase MPS after exercise

Answer 13

ttrue

Question 14

What are the signalling pathways that cause cell/tissue growth and proliferation?

Answer 14

P13K, mTOR, MAPKs

Also signal translation factors causing rapid activation of synthesis of specific proteins

Question 15

Regulation of mTOR is very complex - just need to know that..

Answer 15

its one of the most important proteins in the regulation of protein synthesis

Question 16

True of False

During exercise AMPK activity is decrease while mTOR signalling in increased

Answer 16

false

AMPK activity is increaed while mTOR signalling in decreased

AMPK shuts down alot of energy consuming proteins of wihch mTOR is one.

Question 17

The effect of exercise on S6K1 is ________ specific.

Answer 17

Fibre type specific

Question 18

If you block mTOR, what don’t you get?

Answer 18

a metabolic response to exercise

Question 19

What are the alterations in protein metabolism as we age?

Answer 19

initial hypothesis: basal protein synthesis is reduced and breakdown is increased

But this would account for a huge loss in muscle mass - its more like 8-10% per decade

Protein synthetic response to exercise is reduced in the elderly

Protein synthesis rates after physical activity and protein intake are significantly reduced in elderly humans

Question 20

7 days of bed rest was shown to…

Answer 20

reduced the anabolic response to AA intake

Question 21

What happens to protein synthesis in cancer patients?

Answer 21

the increase in protein synthesis after food intake is blunted

If the cancer is taken away the responses is restored