Dietary fiber ingestion serves as a critical regulator of intestinal motility and the structure and function of the enteric microbiome. Yet, the extent to which subtle structural differences among fibers modulate motility via microbiota-host interactions remains undefined. GABA is a microbial metabolite intimately related to microbial fructan fermentation and host intestinal motility. The purpose of this study was to investigate how fructan chain length influenced microbiota-host signaling underlying ileal and colonic contractions. Male and female mice were pair-fed diets containing no fiber (fiber-free diet, FFD) or the same diet containing cellulose (CELL, fiber control), short-chain fructooligosaccharides (scFOS), or inulin (INU) for 2 weeks. scFOS and INU similarly enhanced total microbial load (fluorescence in situ hybridization), relative abundances of GABA-synthesizing bacteria (16S rRNA sequencing), and luminal GABA concentrations (ELISA) in the ileum and colon versus FFD. Conversely, scFOS altered expression (Fluidigm qPCR) of more motility- and GABA-related genes than INU in the ileum, whereas INU altered expression of more motility and GABA-related genes than scFOS in the colon. Incubation of ileal segments with GABA potentiated contraction force in INU but not scFOS ex vivo. Conversely, incubation of colon segments with GABA repressed contraction force in scFOS, reducing them to levels observed in INU with or without GABA. Notably, GABA altered contraction forces only in female mice. Our study highlights dietary fructan chain length as a determinant of segment- and sex-specific GABA-mediated intestinal motility and creates a rationale and framework for investigation of how prebiotic fiber structures influence microbiota-host interactions and physiology.
Copyright © 2025 The Author(s). Published by Elsevier Inc. All rights reserved.

The gut-brain axis refers to the network of connections that involve multiple biologic systems, allowing bidirectional communication between the gut and the brain. This communication is mainly mediated by gut microbiota, thanks to its ability to modulate several processes like the production of neurotransmitters. As such, keeping a balanced gut microbiota through probiotic intake could be a valid solution in supporting the right gut-brain communications.
A two-step in vitro screening of five different probiotic strains was carried out to select the best performers in the modulation of stress markers. A first selection on SK-N-DZ neuronal cell lines was performed to evaluate the inhibition of the epigenetic enzyme LSD1, promotion of GABA, and expression of serotonin. Three out of five strains were tested for their ability to promote serotonin synthesis in the Caco2 cell line. As a result, Limosilactobacillus reuteri PBS072 and Bifidobacterium breve BB077 were selected as the best performing strains. To confirm their effects in humans, a proof-of-concept trial was carried out to evaluate stress-related parameters for 28 days of product intake in a group of 30 stressed students.
A significant improvement of cognitive functions, in terms of short-term memory, attention, and executive performance, as well as of psychophysiological markers, such as salivary cortisol level, skin conductance, sleep quality, and anxiety, were observed.
According to the results, L. reuteri PBS072 and B. breve BB077 are potential probiotic candidates for improving stress resilience, cognitive functions, and sleep quality.
© 2021 S. Karger AG, Basel.