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.

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 CO2 enrichment in breath sample

Standard radioimmunoassay kit Plasma insulin concentration

Standard glucose peroxidase enzymatic kit Blood glucose concentration

Standard spectrophometric kit 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.