The microbe-heart-brain dialogue: Vagal activity is associated with gut-microbiome patterns in women

Introduction: A functional reciprocity between the gut microbiome and vagal nerve activity has been suggested, however, human studies addressing this phenomenon are limited. Methods: 24- hour cardiac vagal activity (CVA) was assessed from 73 female participants (aged 24.5±4.3 years). Additionally, stool samples were subjected to 16SrRNA gene analysis (V1–V2). Quantitative Insights Into Microbial Ecology (QIIME) was used to analyze microbiome data. Additionally, inflammatory parameters (such as CRP and IL-6) were derived from serum samples. Results: Daytime CVA correlated significantly with gut microbiota diversity (r=0.254, p=0.030), CRP (r=-0.348, p= 0.003), and IL-6 (r=-0.320, p=0.006). When the group was divided at the median of 24 hour CVA (Mdn=1.322), the following features were more abundant in the high CVA group: Clostridia (Linear discriminant analysis effect size (LDA)= 4.195, p= 0.029), Clostridiales (LDA=4.195, p= 0.029), Lachnospira (LDA=3.489, p=0.004), Ruminococcaceae (LDA=4.073, p=0.010), Faecalibacterium (LDA=3.982, p= 0.042), Lactobacillales (LDA=3.317, p=0.029), Bacilli (LDA=3.294, p=0.0350), Streptococcaceae (LDA=3.353, p= 0.006), Streptococcus (LDA=3.332, p=0.011). Based on Dirichlet multinomial mixtures two enterotypes could be detected, which differed significantly in CVA, age, BMI, CRP, IL-6 and diversity. Conclusions: As an indicator of gut-brain communication, gut microbiome analysis could be extended by measurements of CVA to enhance our understanding of signalling via microbiota-gut-brain-axis and its alterations through psychobiotics.