Reduced gut microbial diversity characterized by decreased Bacteroides is associated with vasovagal syncope in...

Vasovagal syncope (VVS) represents the most prevalent form of orthostatic intolerance in children and is characterized by recurrent fainting episodes that substantially impair quality of life and psychosomatic well-being. The pathogenesis of VVS is primarily associated with dysregulation of the autonomic nervous system. Emerging evidence suggests that the gut microbiota, a complex microbial community residing in the human intestine, plays a pivotal pathological role in various autonomic nervous system related disorders. However, data on the gut microbiota profile in pediatric VVS remain limited. The present study therefore aims to characterize gut microbiota changes in children with VVS and its subtypes, providing novel insights into the underlying mechanisms and potential therapeutic strategies.

Fecal samples were obtained from 40 children diagnosed with VVS, comprising 20 with the vasodepressor subtype, 8 with the cardioinhibitory subtype, and 12 with the mixed subtype, as well as from 60 age-matched healthy controls. Microbial community composition was assessed through 16S rRNA gene sequencing. Alpha and beta diversity analyses were conducted to evaluate differences between the VVS and HC groups, as well as among the different VVS subtypes. Then, the bacterial flora with significant differences was identified based on microbial relative abundance data using the Wilcoxon rank-sum test, ANCOM-BC2, and LEfSe analyses.

Compared with HCs, children with VVS exhibited reduced alpha diversity, reflected by lower Simpson and Shannon indices. Beta diversity analysis indicated a modest shift in community structure based on Bray-Curtis and weighted UniFrac distances, accompanied by increased within-group dispersion in VVS. No significant differences were detected in dominant phyla. At the genus level, among the predominant taxa, ANCOM-BC2 identified decreased Bacteroides and increased Prevotella_9 in the VVS group. LEfSe revealed reduced abundances of Bacteroides and Faecalibacterium. No significant differences in alpha or beta diversity indices were observed among the VVS subtypes including vasodepressor, cardioinhibitory, and mixed types.

Our findings provide evidence of gut microbiota alterations in children with VVS and suggest that reduced microbial diversity, particularly the decreased abundance of the key genera Bacteroides, may be involved in the development of VVS.