Lecture 31: New approaches in measuring muscle protein metabolism: the science of muscle hypertrophy Flashcards
How is protein metabolism measured?
Nitrogen balance
Plasma urea and urea in urine
Above methods give a general idea
Using stable isotopes (most accurate method)
How is the stable isotope methodology performed?
Amino acid infused is labelled and ratio between labelled/unlabelled amino acid is measured in muscle biopsies and blood.
13CO2 in breath (more = more oxidation)
What happens to protein metabolism during endurance exercise?
Some amino acids are oxidised (leucine for example) and others are not
What does exercise do to urea production?
Exercise does not increase urea production.
What does protein intake do to leucine and phenylalanine metabolism and urea production?
Increases oxidation of both and increases urea production
What does exercise do to phenylalanine and leucine metabolism?
Exercise increases leucine oxidation but not phenylalanine oxidation
What happens to protein synthesis during and after exercise is performed?
During exercise protein synthesis is reduced and then increases after exercise for >24 hours.
How is protein measured in different muscle organelles?
centrifugation is used to select mitochondria, sarcoplasmic proteins, and myofibrillar proteins
What happens to sarcoplasmic and myofibrillar protein synthesis as a result of resistance training?
Resistance training increases both myofibrillar and sarcoplasmic protein synthesis
What happens to mitochondrial protein turnover following endurance training?
mitochondrial protein turnover rate is higher than myofibrillar protein turnover in endurance training
Which type of muscle fiber has higher mitochondrial protein turnover rate?
Type 1 fibers have more mitochondria so they would have a higher protein turnover rate
Do all mitochondrial proteins have high turnover rate?
Which protein has the highest turnover rate?
Each protein has a different turnover rate:
Electron transport chain proteins have the highest turnover (4x higher than myosin heavy chain)
What is the SunSET methodology?
Expose rats to puramycin in vivo and then use antibodies against puramycin to extract them.
Puramycin looks like tRNA so it can take the place of it and bind to the protein.
Measure protein turnover using a standard western blot.
How is leucine involved in activation of protein synthesis following leucine intake?
It activates mTOR in a leucyl-tRNA synthetase dependent manner.
How is the activity of intracellular signalling pathways measure?
Western blotting using phospho-specific antibodies.
Immunoprecipitation/GST-pulldown: protein-protein interactions
Luciferase assays: transcriptional activity
mRNA sequencing or PCR to detect changes in gene expression
Using transgenic animals
