Microbial Fermentation, SCFA Absorption and Further Metabolism by Host. Karen Scott

Transcription

1 Microbial Fermentation, SCFA Absorption and Further Metabolism by Host Karen Scott

2 SCFA metabolism section Contributors Bert Groen Gilles Mithieux Elaine Vaughan Karen Scott

3 Functions of the gut microbiota modification of host secretions (mucin, bile, gut receptors..) Defence against pathogens competition Barrier function ph inhibition metabolism of dietary components Production of essential metabolites to maintain health Development of immune system, Immune priming Host signalling Gut brain axis Healthy gut microbiota = healthy person

4 Functions of the gut microbiota metabolism of dietary components Production of essential metabolites to maintain health Includes short chain fatty acids (SCFA) Healthy gut microbiota = healthy person

5 Role of the gut microbiota degradation of dietary substrates Faecal SCFA balance between: synthesis conversion absorption Small intestine* Proximal large intestine Distal faeces Food absorption Digestion of dietary carbohydrate, starches, sugars, fat, protein Monosaccharides, fat, aminoacids, soluble phytochemicals Microbial Fermentation Resistant Starch, Fibre (NSP), Oligosaccharides (FOS), SCFA, gases, phytochemicals, other metabolites, minerals Short Chain Fatty Acid (SCFA) concentration gradient Undigested carbohydrate, Lignin, unabsorbed nutrients Blood stream

6 Bacterial metabolism in the large intestine Important for gluconeogenesis in the liver, also cholesterol cycling protects against diabetes and heart disease Major energy source for human colonocytes protects against colon cancer Transported in blood to peripheral tissues, used in lipogenesis Lowers ph - Prevents growth of pathogens Right Side (Proximal) fermentation Absorption Short Chain Fatty Acids + H 2 + CO 2 + CH 4 Dietary fibre Left Side (Distal)

7 Metabolism of the gut microbiota High SCFA production and absorption mmol/kg Low SCFA production and absorption mmol/kg carbohydrate metabolism (~40g/day) Major products SCFA acetate, propionate, butyrate Gases CO2, H2, CH4) protein metabolism (12 18g/day) Major products Branched SCFA -iso-butyrate, isovalerate Gases NH3, H2S Phenols, indoles, amines

8 Composition of the gut microbiota - Dominant bacterial phyla major Phyla 1. Firmicutes 2. Bacteroidetes 1 3. Actinobacteria 4. Proteobacteria Eckburg et al (11831 sequences ; 391 species) Wilson et al 1996; Suau et al 1999; Bonnet et al 2002; Hold et al 2002; Hayashi et al 2002; Hayashi et al 2003; Wang et al 2003; Mangin et al 2004; Manichanh et al 2006

9 Different bacteria produce different metabolites Numerical Functional importance Example abundance* Firmicutes 60% Lachnospiraceae (25%) butyrate production E.rectale Ruminococcaceae (25%) polysaccharide utilisation F. prausnitzii R. bromii Cluster IX (10%) propionate production Megasphaera Bacteroidetes 25% wide range of substrates utilised Bacteroides acetate, succinate, propionate produced Actinomycetes 10% many probiotic strains Bifidobacteria utilise prebiotics lactate production Others 5% lactic acid bacteria Lactobacilli sulphate reducing bacteria [*- In western society] mucin degraders Desulfovibrio

10 Pathways for SCFA production many carbohydrates fucose, rhamnose CO 2 CoA PEP DHAP + L-lactaldehyde acetyl-coa pyruvate oxaloacetate acetyl-coa acetoacetyl-coa β-hydroxybutyryl-coa Lactate lactate lactoyl-coa CO 2 malate fumarate succinate propane-1,2-diol crotonyl-coa acryloyl-coa succinyl-coa propionaldehyde acetate butyryl-coa butyryl-p propionyl-coa R-methylmalonyl-CoA S-methylmalonyl-CoA propionyl-coa propionate propionyl-coa propionate butyrate butyrate propionate Pathway: Species: CoA-transferase Butyrate kinase Eubacterium rectale Coprococcus eutactus Roseburia spp. Coprococcus comes Coprococcus catus Faecalibacterium prausnitzii Anaerostipes spp. Eubacterium hallii Acrylate Coprococcus catus Megasphaera spp. Succinate Bacteroidetes Veillonella spp. Dialister succinatiphilus Phascolarctobacterium succinatutens Propanediol Ruminococcus obeum Blautia wexleri Roseburia inulinivorans From Harry J. Flint et al Proc Nut Soc 2015; 74, Issue 1

11 Pathways for SCFA production many carbohydrates fucose, rhamnose CO 2 CoA PEP DHAP + L-lactaldehyde acetyl-coa pyruvate oxaloacetate acetyl-coa acetoacetyl-coa β-hydroxybutyryl-coa Lactate lactate lactoyl-coa CO 2 malate fumarate succinate propane-1,2-diol crotonyl-coa acryloyl-coa succinyl-coa propionaldehyde acetate butyryl-coa butyryl-p propionyl-coa R-methylmalonyl-CoA S-methylmalonyl-CoA propionyl-coa propionate propionyl-coa propionate butyrate butyrate propionate Pathway: Species: CoA-transferase Butyrate kinase Eubacterium rectale Coprococcus eutactus Roseburia spp. Coprococcus comes Coprococcus catus Faecalibacterium prausnitzii Anaerostipes spp. Eubacterium hallii Acrylate Coprococcus catus Megasphaera spp. Succinate Bacteroidetes Veillonella spp. Dialister succinatiphilus Phascolarctobacterium succinatutens Propanediol Ruminococcus obeum Blautia wexleri Roseburia inulinivorans From Harry J. Flint et al Proc Nut Soc 2015; 74, Issue 1

12 Pathways for SCFA production many carbohydrates fucose, rhamnose CO 2 CoA PEP DHAP + L-lactaldehyde acetyl-coa pyruvate oxaloacetate acetyl-coa acetoacetyl-coa β-hydroxybutyryl-coa Lactate lactate lactoyl-coa CO 2 malate fumarate succinate propane-1,2-diol crotonyl-coa acryloyl-coa succinyl-coa propionaldehyde acetate butyryl-coa butyryl-p propionyl-coa R-methylmalonyl-CoA S-methylmalonyl-CoA propionyl-coa propionate propionyl-coa propionate butyrate butyrate propionate Pathway: Species: CoA-transferase Butyrate kinase Eubacterium rectale Coprococcus eutactus Roseburia spp. Coprococcus comes Coprococcus catus Faecalibacterium prausnitzii Anaerostipes spp. Eubacterium hallii Acrylate Coprococcus catus Megasphaera spp. Succinate Bacteroidetes Veillonella spp. Dialister succinatiphilus Phascolarctobacterium succinatutens Propanediol Ruminococcus obeum Blautia wexleri Roseburia inulinivorans From Harry J. Flint et al Proc Nut Soc 2015; 74, Issue 1

13 Manipulation by dietary change Human dietary study effects of Atkin s type diets in obese subjects [Rowett Human Nutrition Unit] Carbohydrate g NSP g Starch g Protein g Fat g Maintenance (M) Moderate carbohydrate (HPMC) Low carbohydrate (HPLC) M (3 days) HPMC (4 weeks) HPLC (4 weeks) M (3 days) HPLC (4 weeks) HPMC (4 weeks)

14 Effect of dietary carbohydrate content on faecal short-chain fatty acid production 90 A Diet: Faecal short-chain fatty acids [mm] B B A B B A B C Maintenance Moderate carbohydrate Low carbohydrate Significance - A, B, C: P < Acetate Propionate Butyrate Isobutyrate Isovalerate Production of SCFA as dietary carbohydrate [Duncan et al (2007) AEM 73; ]

15 Direct correlation between faecal butyrate concentration and numbers of E. rectale/roseburia group 30 r = mm [Butyrate] Diets maintenance BuK -high BuM carbohydrate BuNK medium regression carbohydrate; low carbohydrate Number of Roseburia bacteria (log10 Rrec584 count) Specific groups of bacteria produce specific products - Relevant to health [butyrate protects against development of colon cancer] [Duncan et al (2007) AEM 73; ]

16 Volunteers with the lowest initial levels of bifidobacteria gave the maximum increase in bifidobacteria numbers after inulin supplementation Change in bifidobacteria (log10 cells/g faeces) after treatment Bifidobacteria (log10 cells/g faeces) at start of study Greatest change in Bifidobacteria numbers in individuals with lowest starting populations Prebiotic effect of fruit and vegetable shots containing Jerusalem artichoke inulin: a human intervention study P. Ramnani, et al BJN (2010), 104, Background levels of host bacteria critical in level of response Responders vs. non-responders in a study

17 Different bacteria produce different metabolites altering microbial composition also alters the overall activity 8% (IX) 4% 25% (Bact) 8% 20% (IV) 35% (XIVa) Low GC Gram +ves Produce butyrate and other SCFAs, utilise polysaccharides Bifidobacteria Produce lactate, many probiotic strains Stimulated by prebiotics Prebiotic consumption increases the intestinal population of Bifidobacteria BUT prebiotics also result in increased butyrate production HOW? Options- Direct stimulation of other bacteria? Bacterial cross-feeding?

18 In pure culture, commensal anaerobes use prebiotic substrates for growth 1,6 1,4 1,2 1 0,8 0,6 0,4 0,2 0-0,2 YCFA basal Starch P95 FOS Synergy HP Dahlia inulin XOS 1,2 1 0,8 0,6 0,4 0,2 P95 FOS synergy HP dahlia As complexity of substrate No. of bacteria utilising it Structure of prebiotic important 0 Bi. infantis E. rectale R. inulinivorans R. faecis Scott KP et al FEMS Micro Ecol 2014

19 Bacterial cross-feeding Gut bacteria exist in a complex mixed ecosystem Starch/FOS Acetate Lactate Formate Butyrate Bifidobacterium adolescentis SCFA concentration [mm] Acetate L-Lactate Formate Eubacterium hallii Bif. adol. E. hallii Duncan SH et al, AEM, 2004

20 Bacterial cross-feeding Gut bacteria exist in a complex mixed ecosystem Starch/FOS Acetate Lactate Formate Butyrate Bifidobacterium adolescentis SCFA concentration [mm] Acetate L-Lactate Formate cross-feeding Eubacterium hallii Butyrate Bif. adol. Bif. adol. E. hallii E. hallii Duncan SH et al, AEM, 2004 Belenguer et al, AEM 2006

21 Mechanisms by which prebiotics increase butyrate production? SCFA production and cross-feeding Complex carbohydrates INULIN FOS Utilisation of intermediate products: CROSS-FEEDING Direct utilisation by butyrate producers Short chain breakdown products Increase in Bifidobacteria [Butyrate] Lactate utilisers [Lactate] [Acetate] [propionate]

22 Mathematical modelling of the gut microbiota Not simple onedirectional interactions

23 Mathematical modelling of the gut microbiota Not simple twodirectional interactions

24 Mathematical modelling of the gut microbiota Intermediary metabolites Complex ecosystem with bacteria interacting with eachother and with intermediary metabolites

25 Short-chain fatty acids (SCFA) and the host Small intestine* large intestine faeces Proximal Distal Food absorption Digestion of dietary carbohydrate, starches, sugars, fat, protein Monosaccharides, fat, aminoacids, soluble phytochemicals Microbial Fermentation Resistant Starch, Fibre (NSP), Oligosaccharides (FOS), SCFA, gases, phytochemicals, other metabolites, minerals SCFA concentration gradient Undigested carbohydrate, Lignin, unabsorbed nutrients Blood stream 7-20µM : 7-20µM : µM Small detectable amounts Much inter-individual variation

26 Short-chain fatty acids (SCFA) and the host Active transport of dissociated acids across epithelial membrane Intestinal gluconeogenesis Butyrate, propionate Results in glucose production Signals to brain Decreases fat storage and body weight Direct interaction with gut hormone receptors

27 SCFA and gut hormone receptors FFAR2 (GPR43) intestinal endocrine cells activated by acetate, propionate > butyrate, results in GLP-1 secretion FFAR2 activation inhibits fat accumulation regulates host energy homeostasis FFAR3 (GPR41), expressed in GLP-1 and PYY secreting endocrine cells activated by propionate and butyrate, results in PYY secretion maintains energy homeostasis, improves insulin resistance satiety signalling PYY (peptide tyrosine tyrosine) and GLP-1 (glucagon-like peptide 1) are gut hormones involved in appetite control and reduced food intake GPR109A, expressed in colonic epithelial cells activated by butyrate GPR109A activation suppresses colonic inflammation and carcinogenesis (anti-inflammatory cytokines eg. IL-10) butyrate inhibits histone deacetylase activity (HDAC), modulating gene expression

28 Why the SCFA production by gut microbiota is important Provides a balance within the host between health and disease Host signalling Bacterial composition Metabolite concentrations

29 Thankyou for your attention