Differential effects of non-absorbable carbohydrates and food fibers on themicrobiota hydrogen and methane production in low- and high-methane-producing ratsтезисы доклада
Аннотация:Background: Non-absorbable carbohydrate (lactulose) and food fibers are used for feeding
gut microbiota, producing biomarkers with positive effects on health: generation of molecular
hydrogen with antioxidant activity, short-chain fatty acids for keeping intestine-blood barrier,
and stimulation of immunity. It is shown that different food fibers induce different responses
of microbiota that depend on the taxonomical composition of the microbiota microorganisms.
Clinical and experimental studies have shown that 40-50% of humans and laboratory animals
generate just hydrogen, whereas the rest of them produce both, hydrogen (H2) and methane
(CH4), the latter is exclusively produced by the methanogenic Archaea (Pimentel et al., 2020;
Modesto et al., 2022). The percentage of methane-produces increases with age. The potential
contribution of methanogenic Archaea in the specific effects of different carbohydrates on the
gut microbiota remains unknown.
Objective: To evaluate the potential effect of methanogenic Archaea on the biomarkers of
the microbiota fermentation function was the aim of our study.
Methods: We have discovered that Wistar rats from two nurseries in the Moscow district are
the different concerning generation of methane by the microbiota. Rats from the Puschino
nursery predominantly produced hydrogen (M- group, n=25), whereas rats from the
Stolbovaya nursery produced a lot of methane (M+group, n=25). So, we used rats from these
two nurseries as models of similar groups of humans.
Before the breath test, the rats were deprived of food for approximately 12 hours. Three types
of dietary compounds were chosen as a carbohydrate load: lactulose (2.0 g/kg), partially
hydrolyzed guar gum (PHGG), (Optifiber®) (4.0 g/kg), and inulin (4.0 g/kg). A breath test
with each carbohydrate was performed in sequence on the rats of both groups every other
day. H2 and CH4 levels produced by the microbiota were measured in air samples by gas
chromatograph (TRILyzer mBA-3000, Japan). Microbial community analysis in the feces of
both groups was performed using high-throughput 16S V4 amplicon sequencing.
Results: Gavage of the tested carbohydrates followed by the increase of H2 in exhaled air in
the "M-group" of rats, the maximum response was to the administration of lactulose and
minimal – to inulin. Responses to the used carbohydrates differed significantly, PHGG vs
Inulin (p=0.03), Lactulose vs PHGG (p=0.009), and Lactulose vs Inulin (p<0.0001). At the
same time, when using all dietary fibers, no significant increase in the level of methane
relative to the "fasting" state (zero measurement point) was recorded. In the "M+ group" we
did not observe significant changes in H2 response, but it was a high increase in the level of
methane. Detailed analysis of the microbial communities in the groups "M-" and "M+" have
shown much higher Alpha and Beta diversities in "M+" group (p <0.001). In both groups of
rats, representatives of the phyla Bacteriodota and Firmicutes make up the majority of the
microbiome. The correlations between the levels of H2 and CH4 in the exhaled air and the
quantitative content of various microorganisms of both groups were observed, as well.
Conclusion: Two groups of rats used in our study imitate groups of humans producing
mainly hydrogen or methane. It was shown that in the group of methane-producing rats, it
was impossible to increase levels of H2 in response to any type of usually used
carbohydrates. We assume that the data received could be explained by the high
activity/quantity of CH4-producing microorganisms that can consume any amount of H2-
produced. We recommend screening humans with non-invasive H2/CH4 breath tests to offer
personalized advice on the healthy consumption of food fibers.