L8.1 Hypertrophy

Question 1

How are protein levels measured?

Answer 1

• Measuring oxidation of 13C labelled isotopes
  
  • ↑ 13C in breath = ↑ oxidisation of infused tracer (↓13C during exercise)
• Measure protein turn-over
  
  • Take blood sample & inspired air sample
  • See how much disappeared from circulation
• Measuring protein breakdown using tracer is hard, researchers use surrogate measures or measure catabolic activities

Question 2

Equation for protein synthesis?

Answer 2

Breakdown + Intake (tracer) = Synthesis + Oxidation

Question 3

What is protein synthesis responsive to?

Answer 3

• Food intake
• Exercise
• Inflammatory signals
• Hormones

Question 4

What are the changes in protein synthesis post-exercise?

Answer 4

• ↑100% protein synthesis after 3 hour resistance exercise, high than basal at 24hr, slightly higher than basal at 48hr
  
  • Protein syn > protein breakdown post-exercise

Question 5

What happens to the protein balance during over-night fasting?

Answer 5

Overnight fast → -ve protein balance (breakdown>syn)

Question 6

Trained vs untrained response to protein synthesis

Answer 6

Trained → shorter period of ↑ protein syn (shorter anaoblic response)

Question 7

Myofibrillar protein synthesis & sarcoplasmic protein synthesis?

Answer 7

• ↑ post-exercise
• 90% max resistance training to fail → highest ↑
• 30% to fail → similar ↑

Question 8

Difference between resistance and endurance training on protein synthesis?

Answer 8

• Myofibrillar protein:
  
  • Untrained: Res > mito (no change)
  • Trained: Res (basal protein syn higher than untrained) > mit (slight ↑)
• Mitochondrial protein:
  
  • Untrained: Mito > res
  • Trained: Mito > res (no change)

Question 9

Regulation of protein synthesis?

Answer 9

• Transcription:
  
  • ↑mRNA → ↑protein synthesis
• Translation:
  
  • No change in mRNA, just ↑ribosomes → ↑protein syn
  • Drives MPS after exercise

Question 10

How is translation regulated?

Answer 10

• Pre-initiation complex to mRNA
• Binding of 1st tRNA to ribosome

Question 11

How is mTOR inhibited during exercise?

Answer 11

• During ex → AMPK → inhibits TSC1 → inhibits mTOR → ↓protein synthesis

Question 12

S6K1

Answer 12

• S6K1 ↑ fibre - type specific
  
  • More type 2 muscle fibres → ↑ S6K1 → ↑muscle mass

Question 13

What is Rapamycin

Answer 13

• mTOR → target of Rapamycin
  
  • Rapamycin blocks mTOR post-ex → ↓↓ post-ex protein syn

Question 14

Aging & muscle wastage

Answer 14

• ↓muscles → ↑fats
• Initial hypothesis of ↓basal syn of protein & ↑ breakdown
  
  • But will lose 1.25% per da6 (wrong hypothesis)
• Sarcopenia is a SLOW process
  
  • Muscle loss → 8-10% per decade
• Aging → protein synthesis response to exercise & food intake is reduced in the elderly

Question 15

Effect of cancer on protein synthetic response

Answer 15

• Cancer → also blunts protein synthetic response to exercise & food intake