The influence of different levels of exercise on protein oxidation measured by 13CO2 breath test

Disturbed protein metabolism is a major negative determinant for the clinical
outcome of patients. The hallmark of disturbed protein metabolism is increased
oxidation of amino acids and/or decreased incorporation of amino acids, which
leads to loss of muscle mass.

To initiate, guide and evaluate (dietary) intervention, it would be highly
useful to be able to monitor the derangements in protein oxidation directly,
but until recently a bedside tool to assess protein oxidation was not available.

A recently developed noninvasive low naturally enriched 13C-protein 13CO2
breath test has shown to be able to quantify the oxidation rate of ingested low
naturally 13C-enriched milkproteins derived amino acids directly. This breath
test seems valuable for patient populations, because it elicits the possibility
to develop a simple bedside monitoring tool for quantification of amino acid
oxidation and amino acid incorporation. The underlying principle of the test
is: 13C-protein + O2 --> 13CO2 + H2O.
A study showed that after 4 weeks of aerobic training in untrained young
healthy subjects (average age, y 21 ± 1) had reduced leucine oxidation [1]. A
pilot experiment showed that exercise results in less oxidation of protein
compared to a rested situation, which shows that the breath test has
discriminative powers and that exercise before protein consumption reduces
oxidation of protein.



1. Gaine, P.C., Viesselman, C.T., Pikosky, M.A., Martin, W.F., Armstrong L.E.
et al. (2005). Aerobic exercise training decreases leucine oxidation at rest in
healthy adults. Human Nutrition and Metabolism, vol. 135, pp. 1088-1092.

To test whether our breath test differentiates between a baseline state and two
different levels of exercise (15 minutes at 30% of VO2 max and 15 minutes at
60% of VO2 max) in 16 healthy volunteers, thereby confirming or denying that
protein oxidation is indeed reduced due to exercise as seen in the pilot
experiments.

Randomized cross-over study.

A submaximal Astrandtest to estimate VO2max. 15 minutes cycling at 30% of
estimated VO2max and 15 minutes cycling at 60% of estimated VO2max.

The subjects will keep a food diary for 3x three days in order to collect data
on their habitual diet. On each third day, the subjects will collect 24-hour
urine in which urea and creatinine will be measured, which will serve as a
measure for muscle mass. Age will be noted. Physical parameters such as height,
weight, body mass index, waistcircumference and fatfree mass will be measured
and/or determined. Fatfree mass will be measured by bioelectrical impedance,
which is a noninvasive method. Body surface area will be calculated upon height
and weight, using the formula described by Haycock et al. Taken together, these
will serve as their baseline values.

Every subject that wants to participate shall start by filling in the ACSM Risk
Classification Form to chart possible heartdisease related problems. Only
subjects who score a 'low risk' are allowed to participate in this study. In
total there will be three exercisetests performed on a stationary bike. The
first is a submaximal Astrandtest to estimate VO2max. The other exercises are
in random order: 15 minutes cycling at 30% of estimated VO2max and 15 minutes
of cycling at 60% of estimated VO2max.

The breath tests will be performed under the supervision of the coordinating
investigator. The risks of all described items are considered negligible. There
is no direct benefit for the subjects. Due to the fact that we will recruit at
the Hanzehogeschool, Wiebengacomplex the chances are that the subjects will be
enrolled in a healthcurriculum. Therefore it could be very interesting for the
subjects to get a sense of what research entails. Especially dieting, fasting
and also the breath test. We offer the subjects the possibility to be present
at a final meeting which will take place after the results have been analyzed.