Differential Effects of Carbohydrates on the Generation of Hydrogen and Methane in Low- and High-Methane-Producing Rats

The goal of the study was to check the hypothesis that low- and high-methane producers will react differently to the administration of non-digestible carbohydrates. It was discovered in our previous studies that Wistar rats from the Puschino nursery (SPF status) were low methane producers, whereas conventional rats from Stolbovaya nursery were high methane producers. Hydrogen and methane breath tests and the taxonomic content of the gut microbiota were evaluated in 25 rats from each nursery. Samples of the exhaled air were taken from awake rats using nose-only apparatus and analyzed by gas chromatography. The taxonomic content of the gut microbiota was evaluated in each rat by the 16S rRNA method. Lactulose, Guar Gum, and inulin were administered by gavage to each rat in 1-week time intervals. Levels of hydrogen and methane in the samples of exhaled air were measured during 8 h after carbohydrate administration. Taxonomic microbiome compositions were quite different between groups. Low methane-producing rats had low alpha and beta diversity, higher abundance of Christensenellaceae and Akkermansia bacteria, lower abundance of Helicobacteraceae, and absence of Methanobacteriaceae) that show similarity to the microbiome of the newborns and children. High methane-producing rats (from Stobovaya nursery) had a much higher diversity of microbiota bacteria, a higher abundance of hydrogen-consuming microorganisms, like Helicobacteraceae and Methanobacteriaceae, and close to the microbiota composition in the elderly. The gavage of carbohydrates in low-methane-producing rats was followed just by the increase in hydrogen level in exhaled air, whereas the same carbohydrates evoked an increase in methane level only. We speculate that the administration of the exogenous hydrogen (hydrogen-rich water) will be more efficient in increasing the antioxidant defense in the elderly because taking the food fibers is not followed by the increase of hydrogen level in the blood.