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Oral Session
Nutritional Microbiology
Wayne Young, PhD
Senior Scientist
AgResearch
Caterina Carco, MSc
PhD student
AgResearch
Jane Mullaney, PhD
Postdoctoral Researcher
AgResearch
Paul Maclean, MSc
Statistician
AgResearch
Paul Cotter, PhD
Head of Department, Food Biosciences
Teagasc
Karl Fraser, PhD
Senior Scientist
AgResearch
Warren McNabb, PhD
Deputy Director
Riddet Institute
Richard Gearry, MB, ChB, PhD, FRACP
Academic Head, Department of Medicine
University of Otago
Nicole Roy, PhD
Science Team Leader, Food Nutrition & health
AgResearch
Objectives : Irritable Bowel Syndrome (IBS) is a functional gastrointestinal (GI) disorder featuring chronic or recurrent abdominal discomfort, usually with changes in GI habit. To improve our understanding of links between the microbiome and IBS, and how these links can be manipulated through diet, we undertook shotgun metagenomic sequencing of fecal samples from a case-control study.
Methods :
Fecal samples from 172 individuals were analyzed by shotgun sequencing using the Illumina NextSeq platform. Of these, 77 were classified as controls, 16 were constipation-predominant IBS (IBS-C), 39 were diarrhea-predominant IBS (IBS-D), 29 were diagnosed with functional constipation (FC), and 11 had functional diarrhea (FD). Taxonomic classifications were determined using Metaxa2 and the SILVA 128 database. Gene functions were assigned by alignment of sequences against a protein reference database using DIAMOND. Mean relative abundance of bacterial taxa and functional genes were compared using permutation ANOVA. Ethical approval was obtained from the University of Otago Human Ethics Committee (Health) (Reference H16/094).
Results : Bacterial genera that discriminated case-controls (P< 0.05) from those with constipation (IBS-C + FC) and diarrhea (IBS-D + FD) included Megasphaera (increased in those with constipation), Blautia (increased in those with diarrhea), and Bilophila (increased in both constipation and diarrhea groups). Megasphaera and Blautia include bacteria that are bile-resistant and produce butyrate, possessing a wide range of Carbohydrate-Active enzymes. Bilophila are sulfite-reducing bacteria that are able to utilize bile-acids. Associated with these taxonomic differences, a wide range of genes involved in carbohydrate, energy, and amino acid metabolism differed significantly (P< 0.05), including some involved in taurine and glycine metabolism. Bile acids are conjugated with taurine or glycine in the liver, and these amino acids are removed by the action of members of the GI microbiota.
Conclusions :
Results from our study suggest carbohydrate and bile acid metabolism by the GI microbiome may be important distinguishing characteristics in functional GI disorders.
Funding Sources :
Funded by the New Zealand National Science Challenge High-Value Nutrition program