Exploratory analysis of gut microbiota and its association with peripheral blood immune cell populations in canine myxomatous mitral valve disease

BACKGROUND: There is increasing evidence that gut microbiota is associated with cardiovascular health. In this exploratory study, the 16 S rRNA amplicon sequencing was employed to investigate the composition and differential abundances of bacterial gut microbiota of dogs at different stages of myxomatous mitral valve disease (MMVD): dogs with congestive heart failure (CHF, n = 38), dogs in the preclinical stage of the disease (non-CHF, n = 23) and healthy controls with no apparent heart disease (n = 17). Flow cytometry was performed to quantify T lymphocytes and their subtypes, as well as monocytes, natural killer (NK) cells and B lymphocytes. Concentrations of selected chemokines, N-terminal pro-B-type natriuretic peptide (NT-proBNP) and C-reactive protein (CRP) were also measured. Correlation analysis was performed between immunological parameters and bacterial taxa of the gut microbiota. RESULTS: Alpha diversity did not differ significantly between the study groups; however, several differentially abundant taxa were identified. Escherichia/Shigella was overabundant in the CHF group and showed a positive correlation with activated T lymphocyte levels, whereas Megamonas was overabundant in the control group and was negatively correlated with monocytes and NT-proBNP levels. Lachnospiraceae was overabundant in the non-CHF group. CONCLUSIONS: These findings suggest that dogs with varying severity of heart disease differ in gut microbiota composition. The observed associations between microbiota profiles, immunological parameters and disease status indicate potential microbiome-immune interactions in disease progression.