What is the evidence that dietary components can act on the microbiome and influence health?

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1 What is the evidence that dietary components can act on the microbiome and influence health? Kristin Verbeke Translational Research in Gastrointestinal Disorders KU Leuven, Leuven, Belgium

2 Diet? health Microbiome 2

3 Experiences from our group Protein fermentation and faecal water toxicity Wheat bran administration and barrier function, lipid metabolism, systemic inflammation Arabinoxylan oligosaccharides (AXOS) administration and lipid and glucose metabolism 3

4 EX. 1: High protein diets increase colonic protein fermentation Urinary p cresol excretion: Unique bacterial metabolite of tyrosine biomarker for protein fermentation 2 16 r=.371; p=.7 sulfate and glucuronide conjugation tyrosine Absolute protein intake (g/24h) 12 8 p cresol Urinary p cresol excretion (mg/24h) Windey K, Plos One 212:7, e52387

5 Relevance for health In vitro studies NH 3, p cresol, phenol and H 2 S have deleterious effects on colonocytes Animal studies Infusion of metabolites Increased protein intake: increased protein intake ~ colonic DNA damage in rats Human studies Epidemiological studies: no clear association between protein intake and CRC risk Intervention studies: Comet assay as marker of faecal water genotoxicity and assessment of CRC risk No consistent effect of high protein intake on faecal water toxicity

6 Impact of protein intake on fecal water toxicity N=2 genotoxicity NP = 15E% from protein HP = 27E% from protein LP = 12E% from protein Low Semi Low 15 Medium NL HP 2 wks isocaloric diets cytotoxicity 12 2 Semi High High LP NL HP LP Windey K, PlosOne 212, 12: e52387

7 Role of sulfate reducing bacteria (SRB) in fecal water genotoxicity S containing AZ (cysteine, methionine) Inorganic sulfur 1 Isocaloric HP diet * Sulfate SRB Genotoxicity (HP baseline, TL, µm) H 2 S 15 Low SRB High SRB

8 Prebiotic administration reduces protein fermentation Reduction in urinary p cresol excretion AXOS (2x5g/d; 2 or 3 wks) (Cloetens L, Br J Nutr, 21: 13, ; Francois IE. Br J Nutr 212: 18, ) Lactulose (2g/d; 4 wks) (De Preter V, J Am Coll Nutr 26: 25, ). Reduction in faecal branched chain fatty acids Wheat bran extract (1g/d or 3g/d) (Windey K, Br J Nutr 215: 113, ; Windey K, Mol Nutr Food Res 214: 58, ) Altered ammonia metabolism: increased uptake in bacterial mass faecal excretion less uptake in systemic circulation urinary excretion as urea (De Preter V, Br J Nutr 24: 92, ; De Preter V, Am J Physiol Gastrointest Liver Physiol 27:292, G358 G368.)

9 Impact of prebiotics on fecal water toxicity No effect of WBE (1g/d) for 3 wks on fecal water cytotoxicity nor genotoxicity Significant reduction of fecal water cytotoxicity after high dose of WBE (3g/d) 6 5 * FW cytotoxicity (IC5) FW genotoxicity (TL) before after before after before after WBE FOS Placebo 1 before after before after before after WBE FOS Placebo Windey K, Br J Nutr 215: 113, Windey K, Mol Nutr Food Res 214: 58,

10 EX. 2: health benefits of modified wheat bran Wheat bran with reduced particle size (WB RPS; 17 µm) 7% 6% 28 days 17 % 5 % n=36 n=14 2 % Dietary fibre Protein Starch Lipids Ash

11 Fasting Ac and total SCFA are increased after WB RPS in Fasting acetate concentrations Fasting total SCFA concentrations Fibre intake Average effect * WB PL WB PL Average effect * WB PL WB PL g/day Before After Before After Before After Before After WB RPS PL Mean and Standard deviation *p<.5 Baseline: Mann Withney U test Before After: Wilcoxon signed rank test Effects: Two way ANCOVA with adjustment for baseline values

12 WB RPS decreases protein fermentation Isobutyrate P cresol Isovalerate Concentration (mmol/l) * Before After Before After Before After Before After Concentration (mmol/l) * Before After Before After WB PL Concentration (mmol/l) * Before After Before After WB PL WB RPS PL Mean and Standard deviation *p<.5 Baseline: Mann Withney U test Before After: Wilcoxon signed rank test Effects: Two way ANCOVA with adjustment for baseline values

13 Microbial richness was not affected by WB RPS

14 Gut permeability is not affected by WB RPS and PL.6 Small intestinal permeability 2. Baseline small intestinal permeability Average effect.4.2 Percentage (%) BMI = 42 BMI = 35. WB PL WB PL..4 Colon permeability 2. Baseline colon permeability Average effect Percentage (%) (Damms Machado et al., Gut, 217).6 WB PL WB PL. Normal values Mean and Standard deviation Baseline: Mann Withney U test Before After: Wilcoxon signed rank test Effects: Two way ANCOVA with adjustment for baseline values

15 Lipid metabolism is not affected by WB RPS and PL 25 Baseline total cholesterol 3 Total cholesterol Concentration (mg/dl) Average effect 2 1 WB PL WB PL 15 Baseline triglycerides 4 Triglycerides Normal values Concentration (mg/dl) 1 5 Mean and Standard deviation Baseline: Mann Withney U test Before After: Wilcoxon signed rank test Effects: Two way ANCOVA with adjustment for baseline values 3 Average effect WB PL WB PL HUMAN INTERVENTION TRIAL 2

16 Systemic inflammation is not affected by WB RPS Baseline CRP CRP 8 * 5 Concentration (mg/l) Average effect WB PL WB PL CRP levels are significantly higher in Indication for low grade systemic inflammation Normal values Mean and Standard deviation *p<.5 Baseline: Mann Withney U test Before After: Wilcoxon signed rank test Effects: Two way ANCOVA with adjustment for baseline values 31 HUMAN INTERVENTION TRIAL 2

17 EX. 3: Impact of AXOS on glucose and lipid metabolism 1 subjects with metabolic syndrome Interventions (2 wks): Outcome parameters: 3g AXOS Equivalent amount of SCFA Insuline resistance: Homeostatic model assessement HDL, LDL and total cholesterol levels, triglyceride levels Plasma SCFA

18 Study design Group 1 (n=5) Screening AXOS 3g/day Wash out 4 weeks SCFA Eq. amount 2 weeks 2 weeks Group 2 (n=5) Screening SCFA Eq. amount Wash out 4 weeks AXOS 3g/day 2 weeks 2 weeks Testday 1 Testday 2 Testday 3 Testday 4 Testday 5 Baseline effects Acute effects Long term effects Acute effects Long term effects 18

19 Overview of a test day Standard breakfast AXOS or SCFA or no supplement Standard lunch Meal Blood samples Vas Scores (satiety) h 4 h 8 h 19

20 Both interventions increase plasma acetate and total SCFA

21 Effects on fasting parameters of glucose metabolism AXOS SCFA

22 Effects on fasting parameters of lipid metabolism AXOS SCFA

23 Effects on fasting parameters of lipid metabolism AXOS SCFA

24 Postprandial glucose and insuline metabolism p=.39

25 Subjective ratings of satiety

26 Conclusions Dietary interventions can modify the microbial activity Changes in microbial activity do not necessarily result in health benefits More pronounced changes in microbial activity may be required to improve health If health benefits are observed, they are not necessarily the consequence of microbiota modulation Intervention studies should investigate whether CHANGE in microbiome correlates to CHANGE in health benefit mediation analysis may provide substantiation for a causal relationship