Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome

Transcription

1 Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome Andrew T. Gewirtz et al N A T U R E VOL M A R C H

2 Background Incidence of IBD Fact 1: increasing in the past decades worldwide Fact 2: markedly higher in developed western countries Journal Club / Ioannis Linas 2

3 Background Incidence of IBD Fact 1: increasing in the past decades worldwide Fact 2: markedly higher in developed western countries Chron s disease V. Loftus, Jr. Clinical Epidemiology of Inflammatory Bowel Disease: Incidence, Prevalence, and Environmental Influences, Edward. Gastroenterology 2004;126: Journal Club / Ioannis Linas 3

4 Background Incidence of IBD Fact 1: increasing in the past decades worldwide Fact 2: markedly higher in developed western countries Ulcerative colitis V. Loftus, Jr. Clinical Epidemiology of Inflammatory Bowel Disease: Incidence, Prevalence, and Environmental Influences, Edward. Gastroenterology 2004;126: Journal Club / Ioannis Linas 4

5 Journal Club / Ioannis Linas 5

6 Role of Microbiota Background Fact 3: gut microbiota provides important benefits: metabolism / immune development Fact 4: disturbance of the microbiota host relationship: numerous chronic inflammatory diseases (IBD and metabolic syndrome) Fact 5: multi-layered mucus structures regulate this interaction Journal Club / Ioannis Linas 6

7 Hypothesis Agents that disrupt mucus bacterial interactions might promote gut inflammation Fact 6: Emulsifiers can increase bacterial translocation across epithelia in vitro Emulsifiers Microbiota Host Interaction Colitis Roberts, C. L. et al. Translocation of Crohn s disease Escherichia coli across M-cells: contrasting effects of soluble plant fibres and emulsifiers. Gut 59, (2010). Journal Club / Ioannis Linas 7

8 Methods 1. wild-type C57Bl/6 2. two engineered strains (IL10 -/- and Tlr5 -/- ) 3. Germ free mice carboxymethylcellulose(cmc) or polysorbate-80 (P80) via drinking water (1.0% w/v or v/v, resp.) for 12 weeks. *P80: FDA approved at up to 1.0%. * CMC deemed generally regarded as safe (GRAS) used at up to 2.0% Journal Club / Ioannis Linas 8

9 Endpoints and Results Microbiota encroachment of the epithelium Wild Type, Water closest bacteria 25 μm from epithelial cells no bacteria within 10 μm Wild Type Emulsifier treated average distance reduced > 50% bacteria in contact with the epithelium IL10 -/- and Tlr5 -/- basal microbiota encroachment enhanced by both CMC and P80 Journal Club / Ioannis Linas 9

10 Confocal microscopy + mucus-preserving Carnoy fixation Journal Club / Ioannis Linas 10

11 Microbiota composition Endpoints and Results Both CMC and P80 dramatically altered composition of both faecal and intestinal-adherent microbiota in in all groups. reduced levels of Bacteroidales / increased levels of bacteria with mucolytic properties marked reduction in microbial diversity Journal Club / Ioannis Linas 11

12 Endpoints and Results Increase in colonic adherent bacteria Journal Club / Ioannis Linas 12

13 Endpoints and Results Pro inflammatory activity in faeces Exposure to emulsifiers increased faecal levels of bioactive lipopolysaccharide LPS and flagellin in all groups * lipopolysaccharide (LPS) and flagellin receptors TLR4 and TLR5 activate pro-inflammatory gene expression Journal Club / Ioannis Linas 13

14 Endpoints and Results Gut permeability Emulsifier treatment increased gut permeability in wild-type and Il10-/-mice *increased levels of serum antibodies to flagellin and LPS correlate with permeability Ziegler, T. R. et al. Detectable serum flagellin and lipopolysaccharide and upregulated anti-flagellin and lipopolysaccharide immunoglobulins in human short bowel syndrome. Am. J. Physiol. Regul. Integr. Comp. Physiol. 294, R402 R410 (2008). Journal Club / Ioannis Linas 14

15 Conclusion 1 exposure to dietary emulsifiers results in erosion of the protective function of the mucus, increased bacterial adherence and a more pro-inflammatory microbiota Journal Club / Ioannis Linas 15

16 Conclusion 1 exposure to dietary emulsifiers results in erosion of the protective function of the mucus, increased bacterial adherence and a more pro-inflammatory microbiota Emulsifiers Microbiota Host Interaction Journal Club / Ioannis Linas 16

17 Conclusion 1 exposure to dietary emulsifiers results in erosion of the protective function of the mucus, increased bacterial adherence and a more pro-inflammatory microbiota Emulsifiers Microbiota Host Interaction Colitis??? Journal Club / Ioannis Linas 17

18 Features of colitis Endpoints and Results the presence of immune cell infiltrates changes in gross colon morphology elevated levels of the leukocyte myeloperoxidase Faecal lipocalin 2 (LCN2) Il10-/- and Tlr5-/-: promoted extent and incidence of colitis, 10fold increase in LCN2 wild-type: subtle histopathologic changes, modest increase in LCN2 Journal Club / Ioannis Linas 18

19 Conclusion 2 emulsifiers may promote robust colitis in susceptible hosts and induce low-grade inflammation in wild-type hosts Journal Club / Ioannis Linas 19

20 Conclusion 2 emulsifiers may promote robust colitis in susceptible hosts and induce low-grade inflammation in wild-type hosts Emulsifiers Microbiota Host Interaction Journal Club / Ioannis Linas 20

21 Conclusion 2 emulsifiers may promote robust colitis in susceptible hosts and induce low-grade inflammation in wild-type hosts Emulsifiers Colitis Journal Club / Ioannis Linas 21

22 Conclusion 2 emulsifiers may promote robust colitis in susceptible hosts and induce low-grade inflammation in wild-type hosts Emulsifiers Microbiota Host Interaction Colitis Journal Club / Ioannis Linas 22

23 Microbiota required? Endpoints and Results Emulsifier treated germ free mice No change in LCN2, Colon length, no splenomegaly No reduction in mucus structure Transfer of microbiota from emulsifier-treated mice to germ-free mice microbiota encroachment, low grade inflammation elevated levels of faecal LPS and flagellin altered microbiota composition Journal Club / Ioannis Linas 23

24 Conclusion 3 emulsifier-induced changes in the microbiota have a role in driving the inflammation and metabolic changes promoted by these food additives Journal Club / Ioannis Linas 24

25 Conclusion 3 emulsifier-induced changes in the microbiota have a role in driving the inflammation and metabolic changes promoted by these food additives Emulsifiers Microbiota Host Interaction Colitis Journal Club / Ioannis Linas 25

26 Discussion Steady increase in the consumption of food additives, many of which have not been carefully tested Testing has used animal models designed to detect acute toxicity and/or promotion of cancer Emulsifiers, can disturb the host microbiota relationship and thus promote intestinal inflammation, which can manifest as colitis or metabolic syndrome. Dietary emulsifiers may have contributed to the post-midtwentieth-century increase in incidence of inflammatory bowel disease and metabolic syndrome Journal Club / Ioannis Linas 26

27 Limitations Animal model study Continuous exposition to emulsifier Withdrawal effect? Overall Provides possible explanations for epidemiologic data Proves Hypothesis step by step Excludes interfering factors Journal Club / Ioannis Linas 27

28 Thank you for your attention Journal Club / Ioannis Linas 28