Tunable Diode Laser High-Resolution Spectroscopic Measurements of the Microbiota Gaseous Biomarkers Kinetics.
Medvedev OS*(1), Ponurovskii YaYa (2), Stavrovskii DB (2)
- Department of Pharmacology, School of Medicine, Lomonosov Moscow State University, Moscow, Russia
- Department of Molecular Physics and Diagnostics, Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia
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Abstract
During several decades hydrogen/methane (H2/CH4)-breath test was used in gastroenterology for analysis of the fermentative activity of the gut microbiome, diagnosis of carbohydrates malabsorption, small intestine bacterial overgrowth (SIBO) depended on microbial composition, mouth-to-caecum transit time and the location of the fermentation along the gastrointestinal system. To perform such a test, the human usually takes nondigestible carbohydrates or glucose as a load. Levels of hydrogen and methane in the breath are usually measured by gas chromatography every 15 or 20 min for 2 or 3 hours after taking a carbohydrate load. Consumption of H2 by the organism could be obtained by measuring the H2 levels in the exhaled breath after drinking hydrogen-rich water (Shimouchi A. et al., PMID: 22259109) They concluded that 41% of taken H2 is consumed by the body. We did not find similar results on the CH4 consumption.
To overcome some limitations of the traditional H2/CH4 breath test we suggest combining the lactulose breath test with an analysis of the kinetics of the exhaled H2 and CH4 after taking H2+CH4-rich water. Tunable Diode Laser High-Resolution Spectrometer (TDLS) was used for measurements of O2, 12/13CO2, CH4, H2S, and NH3 levels in breath in real time (time resolution <0.5 s). The level of H2 in the breath was measured in parallel by the metal-insulator-semiconductor sensor. 25 adult volunteers participated in this pilot study. In 12 experiments H2-rich water was prepared via hydrogen-producing tablets (HRW Natural Health Products Inc., Canada) dissolved in 250 ml of water. In 13 experiments H2 and CH4 -saturated water was prepared by saturating 2 volumes of 250 ml with H2 and CH4, respectively under pressures between 1-4 bar. Concentrations of H2 and CH4 were measured in headspace air over 1 ml sample of freshly prepared water by GC (BreathTracker H2+ , Quintron, USA) (Shimouchi A. et al., PMID: 22259109). In 8 experiments administration of H2/CH4- saturated water was combined with 10 g of lactulose. Expiratory minute volume was measured using a laboratory-made spirometer based on the differential pressure transducer (DUXL Series, Honeywell) calibrated with TSI 4088 D Certifier FA Plus.
We showed that levels of H2 and CH4 increased in breath by 35-60 ppm with a max on 8-12 min and returned to the baseline level in 45-55 min after drinking H2+CH4-saturated water. The ratio of H2 exhaled/H2 ingested is higher than CH4 exhaled/CH4 ingested, which may reflect different intestinal wall permeability for these gases. It allows a combination of this test with taking lactulose or glucose for the regular breath testing because microbiota-produced gases appear in 60-70 min, the time needed to reach the large intestine. Assessment of the H2 or CH4 consumed by the body by using H2-generating tablets or high-pressure gas-saturated water is complicated by the belching evoked by the dissipation of H2 and CH4 in the stomach from the ingested water. We guess that using TDLS allows us to investigate several microbiota-connected pathological conditions by giving test water saturated by H2, CH4 and containing test substances like carbohydrates or/and 13C-carbamide.
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