Non-invasive panel tests for gastrointestinal motility monitoring within the MARS-500 Project

AIM:To develop an integrated approach for monitoring gastrointestinal motility and inflammation state suitable for application in long-term spaceflights.METHODS:Breath tests based on the oral administration of 13 C-labeled or hydrogen-producing substrates followed by the detection of their metabolites(13 CO 2 or H 2) in breath were used to measure gastrointestinal motility parameters during the 520-d spaceflight ground simulation within the MARS-500 Project.In particular,the gastric emptying rates of solid and liquid contents were evaluated by 13 C-octanoic acid and 13 Cacetate breath tests,respectively,whereas the orocecal transit time was assessed by an inulin H 2-breath test,which was performed simultaneously with the 13 C-octanoic acid breath test.A ready-to-eat,standardized pre-packaged muffin containing 100 mg of 13 C-octanoic acid was used in the 13 C-octanoic acid breath test to avoid the extemporaneous preparation of solid meals.In addition,a cassette-type lateral flow immunoassay was employed to detect fecal calprotectin,a biomarker of intestinal inflammation.Because no items could be introduced into the simulator during the experiment,all materials and instrumentation required for test performance during the entire mission simulation had to be provided at the beginning of the experiment.RESULTS:The experiments planned during the simulation of a manned flight to Mars could be successfully performed by the crewmembers without any external assistance.No evident alterations(i.e.,increasing or decreasing trends) in the gastric emptying rates were detected using the 13 C-breath tests during the mission simulation,as the gastric emptying half-times were in the range of those reported for healthy subjects.In contrast to the 13 C-breath tests,the results of the inulin H 2-breath test were difficult to interpret because of the high variability of the H 2 concentration in the breath samples,even within the same subject.This variability suggested that the H 2-breath test was strongly affected by external factors,