Chronic Mesenteric Ischemia Breath Testing

a solution containing butyrate of which 12C of the last 4 carbon positions of butyrate were replaced by 13C butyrate. Participants received 0.80 gram 13C-butyrate (7.3 mMol butyrate / 29 mMol 13C) dissolved in 50 mL water at baseline

a glucose solution in which all six 12C carbons were replaced by 13C D-Glucose. Participants received 0.75 gram 13C-glucose (4.2 mMol D-glucose/ 25 mMol 13C) dissolved in 50 mL water at baseline

Breath tests were performed 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 and 13C-glucose. Breath samples were obtained by blowing a single breath of air through a straw into a test tube. Two breath samples were collected at all mentioned time points. Measurement of 13CO2 is performed using mass spectrometry (IDMicro Breath, Compact Science Systems, Newcastle-Under-Lyme, United Kingdom) using procedures described earlier for galactose and methacetin breath tests, and expressed as an absolute increase in the 13CO2-to-12CO2 ratio in delta permil (δ‰).

The intervention groups performed a standardized bicycle ergometer exercise test of 30 minutes and semi-continuous peripheral blood lactate monitoring. The bicycle ergometer protocol consists of three phases. The first 10 minutes of exercise was used to gradually increase the workload until submaximal exercise intensity was reached which is defined as a circulating blood lactate level between 3 and 5.5 mmol/L. From minute 10 to 20 submaximal exercise intensity was maintained by adjusting the workload based on lactate measurements. Minute 20 to 30 was used to reach maximal exercise intensity, the workload was increased by 10% of the submaximal workload until exhaustion