Effects of acute exercise on acetylcarnitine concentration in endurance trained- and untrained subjects

It has been suggested that imbalance between TCA-cycle flux and *-oxidation may
underlie insulin resistance, leading to type 2 diabetes mellitus.
Acetylcarnitine concentration is suggested to be a marker of such imbalance. It
is expected that when TCA- cycle capacity is high (high oxidative capacity),
less acetylcarnitine will accumulate.

The major research objective is to examine if acute exercise results in a more
pronounced increase in acetylcarnitine concentration in sedentary subjects
compared to endurance-trained subjects and if the exercise-induced increase in
acetylcarnitine is restored more quickly in endurance-trained subjects when
compared to sedentary subjects.

Acetylcarnitine will be determined by 1H-MRS before and after a 30 minute
cycling test. Blood will also be collected from the subjects, prior to and just
afterwards the cyling protocol, to be able to determine free fatty acids in
blood.

N.A.

Subjects will come to the university twice. The first time the subjects will be
screened to access eligibility, which will include filling in of a medical
history questionnaire and a physical activity questionnaire and measurement of
height and body weight. Body composition will also be accurately determined by
hydrostatic weighing and the subjects* maximal aerobic capacity (VO2-max) and
maximal performance (W-max) will be determined by an exercise test (duration of
visit ca. 2 h.).

The second visit is a test day (duration ca. 2.5 h.), for which subjects have
to report to the university in the late afternoon (ca 17.00), not having eaten
after 12.00 o*clock. The test day contains the following measurements: After a
baseline MRI/MRS-scan for acetylcarnitine quantification (duration ca. 1 h.), a
blood sample will be taken (10 mL) and subjects will cycle for 30 minutes at
50% of W-max. Immediately after cycling, another blood sample (10 mL) will be
taken and another MRI/MRS-scan will be performed (duration ca. 1 h.). During
cycling an indirect calorimetry measurement will be performed to determine
energy expenditure, fat- and carbohydrate oxidation.

The experimental procedures are without significant risks. MRS is a safe
procedure (no ionizing radiation), with no known health risk as long as none of
the exclusion criteria is met. There is a chance that MRI reveals an unexpected
medical condition, of which the subject will be informed. His physician will
also be informed.