Abstract
Limited information is available regarding the metabolic consequences of intestinal dysbiosis in dogs with acute onset of diarrhea. The aim of this study was to evaluate the fecal microbiome, fecal concentrations of short-chain fatty acids (SCFAs), as well as serum and urine metabolites in healthy dogs (n=13) and dogs with acute diarrhea (n=13). The fecal microbiome, SCFAs, and serum/urine metabolite profiles were characterized by 454-pyrosequencing of the 16S rRNA genes, GC/MS, and untargeted and targeted metabolomics approach using UPLC/MS and HPLC/MS, respectively. Significantly lower bacterial diversity was observed in dogs with acute diarrhea in regards to species richness, chao1, and Shannon index (p=0.0218, 0.0176, and 0.0033; respectively). Dogs with acute diarrhea had significantly different microbial communities compared to healthy dogs (unweighted Unifrac distances, ANOSIM p=0.0040). While Bacteroidetes, Faecalibacterium, and an unclassified genus within Ruminococcaceae were underrepresented, the genus Clostridium was overrepresented in dogs with acute diarrhea. Concentrations of fecal propionic acid were significantly decreased in acute diarrhea (p=0.0033), and were correlated to a decrease in Faecalibacterium (ρ=0.6725, p=0.0332). The predicted functional gene content of the microbiome (PICRUSt) revealed overrepresentations of genes for transposase enzymes as well as methyl accepting chemotaxis proteins in acute diarrhea. Serum concentrations of kynurenic acid and urine concentrations of 2-methyl-1H-indole and 5-Methoxy-1H-indole-3-carbaldehyde were significantly decreased in acute diarrhea (p=0.0048, 0.0185, and 0.0330, respectively). These results demonstrate that the fecal dysbiosis present in acute diarrhea is associated with altered systemic metabolic states.
Highlights
Recent molecular studies have greatly increased our knowledge about the microbiota in the gastrointestinal tract (GIT) of dogs, mice, and humans [1,2,3,4]
A previous study by our group has compared the fecal microbiome between healthy dogs, dogs with IBD, and dogs with acute diarrhea, but reported only phylogenetic data based on 16S rRNA gene sequences and it is currently unknown whether these microbiome changes are associated with metabolic changes in the host [14]
The Shannon Index was significantly decreased in dogs with acute diarrhea (AD) and non-hemorrhagic diarrhea (NHD) compared to healthy dogs (p = 0.0033 and p < 0.0500, respectively)
Summary
Recent molecular studies have greatly increased our knowledge about the microbiota in the gastrointestinal tract (GIT) of dogs, mice, and humans [1,2,3,4]. Despite recent advances in characterizing microbial communities using sequencing technology, there remains a rudimentary understanding of the complex interactions that occur between the host and intestinal microbes and their metabolic end-products. Metabolomics is a relatively new field that aims to characterize qualitatively and/or quantitatively the presence of small molecules in biological samples [11]. This approach may enhance our understanding of the host-microbe interactions, as well as the metabolic pathways that are involved in health and disease. The aim of the present study was to evaluate a new cohort of dogs with acute diarrhea to confirm the previous findings, and to elucidate whether microbiome changes based on 16S rRNA genes are associated with metabolic and functional changes. This study used Ultra Performance Liquid Chromatography-Mass Spectrometry (UPLC-MS) in an untargeted metabolomics approach coupled with High Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS) in a targeted metabolomics approach to characterize and confirm metabolomic alterations in the serum and urine of dogs with acute diarrhea
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