Labelled-butyrate and labelled-glucose breath testing to detect mesenteric ischemia, a proof of principle study in healthy volunteers

Chronic mesenteric ischemia (CMI) is an incapacitating disease that can
progress to potentially fatal acute mesenteric ischemia. The yearly incidence
of CMI is 9.2 per 100.000 and will increase due to the aging population and the
rising prevalence of cardiovascular risk factors. A gold standard diagnostic
test to diagnose CMI is currently lacking, causing both undertreatment and
overtreatment of patients and thereby superfluous healthcare expenses. Since
oxygen is needed to absorb and metabolize butyrate and glucose in the
enterocyte, a 13C-butyrate, 13C-glucose, or 13C-glucose and D-butyrate breath
test could theoretically quantify mucosal oxygen content and thereby identify
patients with CMI.

To explore the possibility of detecting mesenteric ischemia by 13C-butyrate,
13C-glucose, and 13C-glucose and D-butyrate breath testing by comparing the
timing and concentration of the peak of expired 13CO2 and DHO.

This study is a multi-center randomized interventional proof of principle
study, exploring the possibility of quantifying mucosal oxygen content by
13C-butyrate, 13C-glucose, and 13C-glucose and D-butyrate breath testing.

Three control groups consisting of 5 volunteers will be used during the study.
The first group will receive an oral dose of 0.03 µmol 13C-butyrate, the second
group 3.5 gr D-glucose-1-13C, and the third group 3.5 gr D-glucose-1-13C and a
dose of D7-butyrate. The D7-butyrate dose is set by performing dose-finding
experiments, before the start of inclusion. The control groups will perform
breath tests without performing any physical exercise. Three intervention
groups both consisting of 5 volunteers will receive similar dosages of
13C-butyrate, 13C-glucose, and 13C-glucose and D7-butyrate as the control
group. All intervention groups will be performing a standardized bicycle
ergometer exercise test with a total duration of 30 minutes(10). The exercise
test has been proven to provoke mesenteric ischemia in athletes(11).
All volunteers will perform two breath tests at the following time points
baseline, 0.5, 1, 1.25 1.5, 1.75, 2, 2.25, 2.5, 3, 3.5, and 4 hours after
ingestion of 13C-butyrate, 13C-glucose, or 13C-glucose and D7-butyrate. The
decision to perform breath testing for a total of 4 hours was based on a study
that determined 14CO2 elimination after administering 14C-butyrate (7, 12). A
peak in expired 14CO2 was measured after 2 hours. Since we are interested in
the peak of expired 13CO2 and DHO, a measurement period of 4 hours seems
sufficient, even in the intervention group, in whom a delayed or lower peak is
expected. The frequency of breath testing is intensified between 1 and 2.5
hours after ingestion, to detect the timing of the 13CO2 and DHO peak more
precisely. Samples will be analyzed using mass spectrometry.

Description of intervention: The exercise test consists of 3 phases. Phase 1:
The first 10 minutes of exercise are used to gradually increase the workload
until submaximal exercise intensity is reached. Submaximal exercise is defined
as lactate between 3 and 5.5 mmol/L, obtained from a peripheral intravenous
catheter. Lactate measurements are performed every 2 minutes, using a rapid
lactate measurement kit. Phase 2: From minute 10 until 20 submaximal exercise
intensity is maintained by adjusting the workload based on lactate
measurements. The lactate measurements are performed every 3 minutes. Phase 3:
Minute 20 until 30 are used to reach maximal exercise intensity. Every 3
minutes the workload is increased by 10% of the submaximal workload until
exhaustion. Lactate measurements will be continued with 3-minute intervals.

All participating volunteers will perform 2 breath tests at baseline, 0.5, 1,
1.25 1.5, 1.75, 2, 2.25, 2.5, 3, 3.5, and 4 hours after ingestion of
13C-butyrate, 13C-glucose, and 13C-glucose and D-butyrate. A peripheral
intravenous cannula will be inserted in patients in the intervention group, to
obtain a serum blood sample at baseline and after the exercise test. The
cannula will also be used to obtain blood for the lactate measurements during
the exercise test. Participating volunteers will not experience any benefits of
participation. No adverse events are expected and risks associated with
participation are deemed very low to non-existent. Insertion of the peripheral
intravenous cannula can result in a hematoma.