Re-evaluation of the muscle-full effect during continuously elevated amino acid availability in healthy young males

Muscle tissue consists of proteins. These proteins are built up of a collection
of smaller building blocks: amino acids. When protein is consumed, it gets
digested and absorbed into the blood. The body can use these amino acids, by
taking them up from the circulation. By consuming sufficient protein through
our diet, we ensure that the body is provided with enough amino acids to enable
muscle protein building. Sufficient muscle protein synthesis is important for
maintaining muscle function and strength.
Previous research has shown that when 20 to 25g of protein is eaten, muscle
protein synthesis is maximized. It is therefore recommended to eat 20g of
protein per meal. However, it is currently unclear what happens to muscle
protein synthesis rates if multiple meals are eaten. When multiple meals are
consumed, amino acids appear in the circulation for prolonged period of time.
Theoretically, when there are a high amino acid concentrations in the blood,
muscle protein synthesis rates will increase.
Contrary to this theory, a study more than 20 years ago showed otherwise. It
was observed that muscle protein synthesis rates are only elevated for 2 hours
after which they decrease again. This phenomenon was referred to as the
''muscle-full'' effect. Because this phenomenon is in contrast with more
previous studies, the objective is to replicate that study. This is important
so we can improve nutritional advice for healthy, but also clinical populations
in the future.

To assess muscle protein synthesis rates to continuous, elevated plasma amino
acid availability in healthy young males

Non-randomized, non-blinded, clinical trial

Infusion of amino acids

The burden and risks associated with this study are moderate. It is a short
study (1.5 days) with a few invasive, but low-risk
measurements.It is possible that for a few days there is a feeling of soreness
after the biopsies which is comparable to the soreness after bumping into
a table. Also, there is a possibility of some additional bleeding after the
biopsies. For six biopsies this risk is present six times in total, but it
is no major health risk.
Placing the cannulas during the test day can be uncomfortable and can result in
a small hematoma. However, this makes the 15 blood
draws relatively easy. The amount of blood that is drawn (160 mL) is way less
than an average blood donation and will recover within a
month.
In total, participants visit the university twice, being fasted on both
occasions. On the test day participants will stay fasted for a longer
time, which can cause a feeling of hunger. Water drinking is allowed and
unlimited. Furthermore, the participants will fill out diaries 2
days prior to the test day that will cost 30 minutes. During these days, they
are also not allowed to drink alcohol or do heavy physical
activities.
The dexa scan provides valuable data about the body composition, but has a
small radiation burden. This burden is negligible when
compared to the yearly background radiation.
There is no direct benefit for the participants, only their contribution to
scientific knowledge. The participants will get more insight into
their body composition.