INGESTED PROTEIN DOSE RESPONSE
OF MUSCLE AND ALBUMIN PROTEIN
SYNTHESIS AFTER RESISTANCE
EXERCISE IN YOUNG MEN
Presented by Leanne Gravette, Jeff Gibberman, Zoe Fisher-Falk
BACKGROUND
American Journal of Clinical Nutrition
 Published in 2009.
 Authors: Daniel R. Moore, Meghann J.
Robinson, Jessica L. Fry, Jason E.Tang, Elisa I.
Glover, Sarah B. Wilkinson, Todd Prior, Mark A.
Tarnopolsky,and Stuart M. Phillips

1ST OF IT’S KIND
1st study to measure a “dose-response relation
between ingested whole protein and muscle
protein synthetic rates after resistance
exercise” (Moore, et al 161).
 Past studies have proved a dose response at
rest, but never after resistance exercise.

BACKGROUND

There is a correlation between
amino acid intake and
enhanced anabolic effect of
resistance exercise on muscle.
POINTS OF INTEREST
How do specific doses of whole protein intake
affect muscle protein synthesis (MPS) and albumin
protein synthesis (APS)?
 Does the dose intake enhance phosphorylation of
the candidate signaling proteins?
 Does albumin act as a protein storage system in
times of excessive protein intake?


How is this possible phenomenon tied in to increase in
albumin synthesis?
THE PATHWAY

mTOR Signaling Pathway
 Pathway
towards MPS
 Contains regulatory proteins

Candidate signaling proteins
 Changes
in MPS may be regulated by these target
proteins

“Stimulation of MPS in humans after feeding or resistance exercise is
accompanied by enhanced phosphorylation, and presumably activity, of the
mTOR signaling pathway.”
ALL ABOUT ALBUMIN
Albumin unaffected by resistance exercise in
young men.
 Albumin synthesis stimulated by increased
availability of amino acids.
 Can dietary amino acids be incorporated into
albumin protein in an effort to minimize their
irreversible oxidation?


Feeding induced increase in albumin protein synthesis
may serve as “storage’’ until amino acids are needed in
periods of reduced supply.
HYPOTHESIS




Mixed MPS will demonstrate a dose response to
dietary protein after resistance exercise.
The maximal effective (maximally stimulated MPS)
dose will be similar to what has previously been
reported to be maximal at rest.
Plasma albumin protein synthesis will display a
similar dose response to dietary protein as mixed
muscle protein.
Above an ingested dose of protein that maximally
stimulated muscle and albumin protein synthesis,
amino acid oxidation will increase.
SUMMARY OF OTHER AREAS OF INTEREST



The response of MPS to both feeding and exercise
is regulated by specific protein kinases in the
mTOR signaling pathway. Is there increased
phosphorylation in response to increased dietary
protein?
Is there a direct relationship between increased
dietary protein intake and increased
phosphorylation?
Can excess dietary amino acid be stored by
albumin protein after increased APS?
TEST SUBJECTS
Six healthy, active males
 Age: 20-24yrs
 Weight 174-205lbs approx
 Height: 5’7’’-6’3”
 At least 4 months previous recreational
weightlifting experience.

METHODS
Subjects performed exercise, ingested variable
quantities of whole protein and then were tested
for increases in MPS, APS and oxidation.
 In this experiment Leucine was used as a tracer.
This means that a stable isotopic form of leucine (
[1-13C] leucine), not usually found in the body was
used to track what happened to the protein
ingested post-exercise.
 Leucine chosen b/c it is a EAA and a BCAA,
primarily metabolized in skeletal muscle.

PROCEDURE




The subjects were tested five times with at least one week
between each trial.
The trial consisted of intensive leg resistance exercises
that were designed to max out their physical capabilities.
After exercise a catheter was inserted in each arm, one
was used for taking blood samples and the other was used
to inject the leucine tracer into the blood stream.
This was followed immediately by an ingestion of an egg
protein drink. The protein content for each participant
varied between 0, 5, 10, 20 and 40 grams of dietary
whole protein.
PROCEDURE CONT.



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In order to determine the physiological response to
the ingested protein they used various methods of
analyzing blood, breath, and muscle samples
Blood samples were taken from the catheterized arm
Breath was collected to determine CO2 enrichment
Muscle biopsy was taken twice (ouch!) at 1 and 4
hours from exercise
They took a ton of measurement from all these
samples using many different devices.
MEASUREMENT DEVICES

Isotope ratio mass spectrometry


Standard radioimmunoassay kit


Blood glucose concentration
Standard spectrophometric kit


Plasma insulin concentration
Standard glucose peroxidase enzymatic kit


CO2 enrichment in breath sample
Plasma urea concentration
Gas chromatography-mass spectrometry

Plasma enrichment
MORE MEASUREMENT DEVICES

Cation exchange chromatography
 Free

amino acid purification
Combustion-isotope ratio mass spectrometry
 Amino

acid conversion
Bicinchoninic acid protein assay


Determines protein contest of homogenates
GC-combustion-isotope ratio mass spectrometry

Liberates bound amino acids
RESULTS
Direct correlation of increased dietary protein
and MPS and APS up until 20 grams of ingested
egg protein.
 At 40 grams, no change in MPS or APS,
however there was greater measure of leucine
oxidation.



demonstrates that albumin does not actually store
excess dietary amino acids.
No noticeable increase in phosphorylation of
the protein kinases in the mTOR signaling
pathway as a direct result of increased protein
intake.
ALBUMIN PROTEIN SYNTHESIS
MUSCLE PROTEIN SYNTHESIS
LIMITATIONS

Small sample size
6
people to represent the population
 young and active men only.
The study is nonspecific about the level of
fitness and capability of each individual.
 What is the change of maximal protein
utilization in people of various size (ex: Jeff vs.
Leanne)

FUTURE RESEARCH
Researchers proposed the possibility that
ingesting 20 grams of protein, the peak
amount for MPS and APS stimulation, five to six
times daily would maximize utilization of
ingested protein.
 With a stronger study in this area one could
provide empirical evidence to convince people
to eat an optimal amount of protein.

RELEVANCE

Detrimental effects of overconsumption of
animal protein.




Ex: Met from meat
Osteoporosis
Atherosclerosis
Excess dietary AA get oxidized and stored as
fat.