藤井 匡

Aims: To characterize fecal gut microbiota features associated with a history of aggression in dogs and to explore whether supplementation with the prebiotic fructooligosaccharide 1-kestose is associated with alterations in gut microbiota composition and owner-reported aggression-related behaviors. Study Design: An exploratory, non-randomized field study comparing aggressive and non-aggressive client-owned dogs, followed by a single-arm pre–post supplementation study in aggressive dogs with owner-reported behavioral outcomes. Place and Duration of Study: The study was conducted in Japan between 2021 and 2023, with a 60-day 1-kestose supplementation period for the intervention group. Methodology: Fecal samples from aggressive toy poodles (Agg; n = 10) and non-aggressive controls (N-Agg; n = 6) were analyzed using 16S rRNA gene sequencing. Dogs in the Agg group received 1-kestose (400 mg/day) for 60 days. Behavioral outcomes were assessed before and after supplementation using the shortened, owner-reported Canine Behavioral Assessment and Research Questionnaire (C-BARQ). Genome analysis of Blautia caecimuris was conducted to identify glycoside hydrolase family 32 (GH32) enzymes, and a recombinant GH32 enzyme was functionally characterized for fructooligosaccharide hydrolysis. Results: At baseline, Agg dogs differed in gut microbial β-diversity from N-Agg dogs and showed higher relative abundances of Mediterraneibacter gnavus, the Segatella copri group, and the Phocaeicola vulgatus group. Following 1-kestose supplementation, M. gnavus was lower, the B. caecimuris group was higher, and the β-diversity difference between groups diminished. In parallel, owner-reported aggression-related C-BARQ items—particularly responses to unfamiliar dogs and strangers near the home—were lower after supplementation. The characterized GH32 enzyme from B. caecimuris hydrolyzed 1-kestose and nystose. Conclusion: These findings indicate that 1-kestose supplementation is associated with concurrent alterations in the canine gut microbiota and owner-reported aggression-related behavioral scores. While causality cannot be established, the results support further investigation of microbiota–behavior associations using larger, well-controlled study designs incorporating objective physiological and microbial measurements.

Prebiotics, such as short- and long-chain fructans, beneficially modulate the microbiota; however, individual variability in response remains unclear. In this randomized, double-blind, placebo-controlled trial, 40 healthy adults received either a combined fructan supplement—1-Kestose (Kes) and inulin (Inu)—or a placebo (maltose + cornstarch) for 4 weeks. We investigated the fecal microbiome, bacterial growth, and glycoside hydrolase family 32 (GH32) gene abundance, and further examined the association between dietary intake and GH32. Kes and Inu co-supplementation selectively increased Bifidobacterium adolescentis and B. longum, harboring the GH32 genes inuA and cscA, respectively. Growth assays revealed that B. longum, which expresses cscA, grew only on Kes, whereas B. adolescentis, which expresses inuA, showed growth on Kes and Inu. Only responders—participants showing increases in both species—exhibited consistent upregulation of GH32 genes and were associated with higher retinol and C16:3 (n-6) fatty acid intake, as well as greater green leafy vegetable and canned tuna consumption. This study provides insights into species level responses to prebiotics, supporting personalized dietary strategies for gut microbiota modulation.

Psychiatric disorders such as major depressive disorder are closely linked to the intestinal environment, suggesting intestinal health may contribute to their prevention. Prebiotics, which enhance intestinal health, are promising candidates for preventing psychiatric disorders. 1-Kestose (kestose), a type of prebiotics, has shown potential, but its effects on psychiatric disorders remain unclear. In this study, we investigated whether kestose prevents abnormal behaviors induced by social isolation (SI) stress and which underlies mechanisms of preventive effects. C57BL/6J male mice (3 weeks old) were divided into two groups: individually housed (SI) group and housed five mice per cage (GH) group. Each group received either a normal diet or a kestose diet (5% kestose) for 5 weeks daily until the end of the behavioral testing. Kestose prevented the SI-induced abnormal behaviors including reduced sociality, impaired spatial recognition, and heightened anxiety, which were associated with suppressed microglial activation in the hippocampus. Kestose altered the diversity of gut microbiota and increased the abundance of Bacteroides sartorii. Furthermore, short-chain fatty acids (SCFAs) such as butyric acid, acetic acid, and propionic acid, produced by intestinal microbiota, were increased after kestose supplementation. Positive correlations were observed between B. sartorii abundance and SCFA levels, suggesting that B. sartorii contributes to SCFA production. Notably, both B. sartorii and SCFAs were strongly associated with the abnormal behaviors by SI. These findings suggest that kestose prevents SI-induced abnormal behaviors by modulating gut microbiota, particularly B. sartorii, through an increase of SCFA production. Taken together, kestose could be used as a promising prebiotic intervention for psychiatric disorders.

Aims: Feline atopic skin syndrome (FASS) is a chronic inflammatory skin disease characterized by pruritus and typical lesions such as erythema, papules, excoriations, and lichenification. Although the relationship between gut microbiota and atopic dermatitis is well-documented in humans and dogs, research exploring gut-targeted therapies for FASS remains limited, and the role of gut microbiota in this condition is unclear. This study aimed to conduct a pilot investigation into the effects of a parasynbiotic containing 1-Kestose and heat-killed Lactobacillus plantarum FM8 on clinical symptoms and gut microbiota in cats with FASS. Methodology: Eleven cats with FASS were orally administered the parasynbiotic, composed of 1-Kestose (400 mg/day) and heat-killed Lactobacillus plantarum FM8 (2.0 × 1010 CFU/day), for 8 weeks. Clinical symptoms were assessed using the SCORing Feline Allergic Dermatitis (SCORFAD), investigator pruritus score (IPS), and rating of global assessment of improvement (GAI). Fecal microbiota was analyzed at baseline and post-intervention using 16S rRNA sequencing, with samples from 16 healthy cats as controls. Results: Parasynbiotic intervention significantly reduced SCORFAD and IPS scores (p = 0.0224 and p = 0.0018, respectively), and improvement in GAI scores was observed in 10 of 11 cats. Additionally, β-diversity analysis of fecal microbiota did not reveal significant differences between baseline and post-intervention samples within the FASS group, a trend toward distinction from healthy controls was observed. Taxonomic analysis revealed that Collinsella stercoris was significantly enriched in FASS cats compared with healthy controls, whereas its abundance decreased significantly after parasynbiotic intervention. Conclusion: These findings suggested that improvements in clinical symptoms may be linked to alterations in gut microbiota, specifically through the reduction of C. stercoris, which was initially enriched in FASS cats. This pilot study underscores the potential of parasynbiotic administration as a therapeutic strategy for FASS, while its small sample and lack of placebo control warrant cautious interpretation.