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Regulation of skeletal muscle mass: hypertrophy (Muscle protein B & S…
Regulation of skeletal muscle mass: hypertrophy
FFA pool (~70). IN: de novo synthesis, intake and breakdown of proteins. OUT: oxidation, and protein synthesis
Measure oxidation of AA: infuse 13C labelled AA. Beta blockade increases AA oxidation by decreasing lypolysis and glycogen breakdown.
Measuring whole body protein S and B
infusion of 13C phenylalanine labelled AA. Take plasma samles and measure labelled AA:unlabblled. Over time there is plateau of labelled AA. Take blood samples ???
Measuring protein synthesis:
2 hr infusion period. look at label in biopsy at time=0--> minimal label. Biopsy at t=6--> increased labelled 13C phenalalynine in protein--> protein synthesis
Protein synthesis in different tissue:
Fractional synthetic rate: protein synthesis expressed as %/day. Muscle: 1.5% synthesised/day. Liver: 12.% synthesised/day. VLDL 425% synthesised/day.
%whole body protein turnover. Muscle contributes to 20% of whole body turnover. liver to 11% and VLDL 0.12%. This is dependent on the mass of the organ.
Measurement of protein synthesis in different protein fractions: From muscle biopsy can work out protein synthesis in itochondria, sarcoplasmic proteins and myofibrillar protein. Mitochondrial synthesis rate is > myofibrillar protein systhesis rate.
Muscle protein B & S responde to:
Inflammatory signals
Food intake
Hormones
Exercise
Measuring protein breakdown:
quite hard. Researches rely on surrogate measures rather than using tracers to measure protein B.
Resistance exercise and protein B:
STUDY: measure protein S and B post exercise: Protein S increases to greater extent than B during post exercise recovery for up to 48 hr.
Whole-muscle protein synthesis during and after exercise: During exercise protein S is decreased, after it is increased. Protein S is increased post exercise for less time in a trained individual.
Myofibrillar and sarcoplasmic protein S rates (FSR) post exercise:
Post Resistant exercise: increases myofibrillar and sarcoplasmic protein synthesis. At higher intensities protein S is higher post exercise.
Post Endurance Exercise: mito FSR> myo FSR. Only resistant exercise increases myo FSR. Trained: resistant training doesn't increase mito FSR????
Regulation of protein synthesis: multiple steps (trancription, translation ect). Is energy dependent.
Increase in transcription--> multiple mRNA. Increase in translation efficiency--> increases number of ribosomes.
Driver of increase in MPS post exercise
STUDY reasistant exercise --> measure protein S using stable isotope and changes in mRNA expression (myosin and actin mRNA). No change in mRNA but increase in protein S. Therefore increases must be due to translation.
Regulation of protein S
cell surface receptros--> signalling pathways (PI3K, mTOR, MAPKs--> general translation factors and RNA binding proteins.
