Understanding prebiotics and scientific discoveries furthering their development

Transcription

1 Understanding prebiotics and scientific discoveries furthering their development Karen P. Scott Microbiology Group Rowett Institute of Nutrition and Health

2 CONTENT What are synbiotics, prebiotics, probiotics The gut microbiota Can we use prebiotics to improve health? Are Prebiotics the most effective approach to improving health?

3 Definitions Probiotics live microorganisms which, when administered in adequate amounts confer a health benefit on the host (FAO/WHO 2001) Prebiotics A selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health. (Gibson et al. 2010) Synbiotics mixtures of probiotics and prebiotics that beneficially affect the host by improving the survival and implantation of live microbial dietary supplements in the gastrointestinal tract (Andersson et al 2001)

4 Definitions Probiotics Prebiotics Consumption of live bacteria Food for bacteria that are already in large intestine Synbiotics mixtures of live bacteria and substrate that can help them (and resident bacteria) grow and survive

5 Prebiotics Definition Description Example A selectively fermented ingredient Must reach the large intestine undigested by host enzymes Fructooligosaccharides (FOS) that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, Must only be fermented by one/few colonic bacteria, not by all bacteria OR Must change the balance of fermentation products Increases numbers of Bifidobacteria Increases butyrate production thus conferring benefit(s) upon host health. Must be a measurable health benefit Eg increases Ca absorption

6 Prebiotics Accepted examples of prebiotics Fructo-oligosaccharides (FOS) Galacto-oligosaccharides (GOS) Inulin Candidate prebiotics Lactulose Human milk oligosaccharides (HMOs) Arabinoxylan Resistant starch Occurrence (3-10%) FOS/inulin occur naturally in some foods Chicory, garlic, artichoke, leek Increase amounts by supplementation cereals, bread, yoghurts,etc Use in infant formula/foods (FOS and GOS) Target (adult) intake: 2 20g/day Health benefits Garlic (9-16%) Leeks Change bacterial growth/activity Stool bulk/transit time Onion (2-6%) BUT current lack of real biomarker for GI health

7 CONTENT What are synbiotics, prebiotics, probiotics The gut microbiota Can we use prebiotics to improve health? Are Prebiotics the most effective approach to improving health?

8 Human Gut Microbiota / ml gut contents (large intestine) Outnumber human cells in the body by 10 : 1 Complex and diverse bacterial community >500 hundred different bacterial species colonise each individual Colon Most are highly oxygen sensitive, but can be cultured Molecular approaches (mainly based on 16S ribosomal genes) allow analysis of bacterial communities without cultivation Until recently >70 % of phylotypes belonged to no known cultured species

9 Dominant bacterial phylotypes ~50% of sequences correspond to 25 most abundant species We have cultured representatives of all of them 295 additional phylotypes 8% 0.6% Data from 6 healthy, obese individuals; converted from Walker et al 2011, ISME J 5% 2% Faecalibacterium prausnitzii Eubacterium rectale Colinsella aerofaciens Clostridium clostridioforme Bacteroides vulgatus Bacteroidetes Anaerostipes hadrus Ruminococcus bromii IV, Ruminococcus group Eubacterium hallii Blautia wexleri Bacteroides dorei Roseburia faecis Dorea longicatena Subdoligranulum variabile Bacteroides uniformis Ruminococcus obeum Bacteroides ovatus Blautia luti Parabacteroides distasonis sp nov A2-166 sp nov SR1/5 Lachnospira pectinoschiza sp nov 80/3 Dialister invisus Roseburia inulinivorans Ruminococcus callidus others IV, F.prausnitzii group XIVa, E.rectale/Roseburia group major butyrate producers Major propionate producers Major lactate utilisers (into butyrate) Top 25 range of products

10 Fate of dietary products in the GIT Food absorption Small intestine* Digestion of dietary carbohydrate, starches, sugars, fat, protein Monosaccharides, fat, aminoacids, soluble phytochemicals Proximal large intestine Resistant Starch, Fibre (NSP), prebiotics SCFA, gases, phytochemicals, other metabolites, minerals Distal SCFA concentration gradient (acetate, butyrate, propionate) faeces Undigested carbohydrate, Lignin, unabsorbed nutrients Blood stream Transported in blood to peripheral tissues, used in lipogenesis [Adapted from Topping & Clifton, 2001 Physiol Rev. 81; ] Major energy source for human colonocytes; Protects against cancer Important for gluconeogenesis in the liver; satiety signalling

11 Diseases where dysbiosis of the gut microbiota has been noted (and opportunities for prebiotics) Disease IBS IBD Microbial association Therapy target or substrate Altered diversity (inc Clostridium; Dec Bifido, Fprau) Reduced diversity (inc proteo/enterobacteria; dec Lachnospiraceae, cluster IV) Colorectal cancer Inc Fusobacterium, E. coli Coronary heart disease Inc or dec fibre intake (eg inc starch) dietary fibre prebiotics Lower serum cholesterol; Inc β-glucan Scientific evidence variable Alter fermentation, faecal bulking, reduced transit time Reduce cholesterol, BP Obesity Reduced diversity Appetite regulation? Diabetes Inc opportunist pathogens, dec butyrate producers prebiotics Modify glycemic and insulin response Osteoporosis Inc colonic ph Prebiotics Lower ph, increase Ca absorption

12 log Bif log Rrec The microbial community and disease : IBS Irritable bowel syndrome (IBS) complex disease, different manifestations Increased fibre intake helps some sufferers, increases symptoms in others more variability between IBS-C individuals than between healthy volunteers. E.rectale/Roseburia group p= baseline 1=Back; 2=Dextrose; dextrose 3=Starch starch Blue healthy Red IBS Bifidobacteria p=0.029 PCA of FISH data for background samples Significantly less Roseburia and Bifidobacteria species in IBS:healthy Chassard et al Aliment Pharm Ther. 2012, 35; baseline 1=Back; 2=Dextrose; dextrose 3=Starch starch

13 CONTENT What are synbiotics, prebiotics, probiotics The gut microbiota Can we use prebiotics to improve health? Are Prebiotics the most effective approach to improving health?

14 Health benefits attributed to prebiotics Improved gut function stool bulking and faster gut transit Management of Inflammatory bowel disease reduction in inflammatory markers Jan 2014 EFSA preliminary approval of health claim Increased consumption of Native chicory inulin can Prebiotics may reduce the increase risk of colon stool cancer frequency reduced DNA damage and cell proliferation, faster gut transit Prebiotic (GOS/FOS) supplementation of infant formula increases bifidobacteria numbers Prebiotics (FOS/Inulin) increase calcium absorption and bone health ph effect Consumption of prebiotics instead of sugars can lower glycaemic index induce a lower blood glucose rise after meals compared to those containing sugars Jan 2014 EFSA preliminary approval of health claim Rodent studies indicate that prebiotics reduce food intake and fat mass SCFA stimulated secretion of gut peptides Inulin/FOS can lower glycaemic index (PYY, GLP-1, reduced ghrelin)? more work required consumption of foods containing non-digestible carbohydrates instead of sugars induces a lower blood glucose rise after meals compared to those containing sugars

15 Galacto-oligosaccharides (GOS) GOS are produced from lactose Gal Glu Gal Glu Gal Glu Lactose Lactose β-galactosidase GOS stimulate growth of Bifidobacteria n Galacto- Oligosaccharides (n = 1 7) Glu Glucose 9 studies in healthy adults between studies also showed increase in Lactobacilli 8 studies in infants comparing GOS formula with normal formula 2 studies also showed increase in Lactobacilli Applications improve infant formula to be more representative of breast milk - use to improve constipation and increase Bifidobacteria populations in geriatrics

16 More recent studies using GOS prebiotic supplementation Prevents decrease in bifidobacteria population and butyrate production otherwise shown following amoxicillin treatment Ladirat SE et al BJN 2014 Reduced colic incidence in formula fed infants, increased bifidobacteria (mimics effect of human milk) Giovannini et al J Am Coll Nut 2014 Increases Ca absorption and bifidobacteria counts in adolescent girls Whisner et al 2013 BJN Increases bifidobacteria in healthy adults but response is individual-specific Responders and non-responders Davis LMG 2011 PLosOne - Bacterial effects mainly focus on Bifidobacteria

17 Dietary supplementation with traditional prebiotics Many studies have shown that fructo-oligosaccharides (FOS) and inulin stimulate numbers of Bifidobacteria = Bifidogenic BUT Bifidobacteria produce lactate, and prebiotics stimulate butyrate production HOW? 2 possible mechanisms of butyrate Fructans, β(1-2) fructose polymer FOS n= 2-8 (DP) inulin 9<n<60 1. additional direct stimulation butyrate producers 2. Bacterial cross-feeding

18 % of universal 16S rrna gene copies Effect of prebiotics (inulin) on the faecal microbiota Q-PCR quantification of dominant groups of the human gut microbiota 50 Cluster XIVa Cluster IV background control inulin 20 P = P = Bact Cl XIVa Rrec2 Rrec1 Ehal Cl IV Fprau Rum CoAT Bifids Stimulation of bifidobacteria and Faecalibacterium prausnitzii produces butyrate Fuller et al, BJN (2007); Ramirez et al, BJN (2009)

19 Commensal anaerobes use prebiotic substrates for growth YCFA basal Starch P95 FOS Synergy HP Dahlia inulin XOS 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

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

21 SCFA concentration [mm] Bacterial cross-feeding Gut bacteria exist in a complex mixed ecosystem Starch/FOS Acetate Lactate Formate Butyrate Bifidobacterium adolescentis Acetate L-Lactate Formate cross-feeding Eubacterium hallii 2 0 Bif. adol. Bif. adol. Butyrate (Duncan et al, AEM, 2004; Belenguer et al, AEM 2006) E. hallii E. hallii Duncan SH et al, AEM, 2004 Belenguer et al, AEM 2006

22 Mechanisms by which prebiotics increase butyrate Prebiotics and butyrate 2 routes for production production? (Resistant starch) FOS INULIN Direct utilisation by butyrate producers Increase in Bifidobacteria Utilisation of intermediate products: CROSS-FEEDING [Butyrate] [Lactate] [Acetate]

23 Is a prebiotic best given along with a probiotic bacterium - as a synbiotic? Synbiotic = probiotic plus prebiotic Combination critical - Probiotic bacterium should be able to use prebiotic as a growth substrate can help survival and establishment Lactitol and Lb. acidophilus in elderly Increase in Lb. acidophilus and total Bifidobacteria synergy 1(FOS) plus B. animalis Increased population of total bifidobacteria, Mix of 4 bacteria plus FOS reduced upper GIT infection in intensive care patients Different mix of 4 bacteria with 4 prebiotics reduced post-operative infections following liver transplants (3% compared to 48%) Synbiotic therapy (GOS + B. breve + Lb. casei) significantly improved numbers of beneficial bacteria (Bifids and Lactobacilli), and decreased the number of harmful bacteria in elderly patients undergoing gastroenterological surgery Synbiotic consumption (B. longum plus Synergy1) improved clinical symptoms in Crohns disease patients Distinguishing responders : non-responders is an important factor for consideration in all prebiotic/probiotic/synbiotic studies

24 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 Greatest change in Bifidobacteria numbers in individuals with lowest starting populations Bifidobacteria (log10 cells/g faeces) at start of study 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

25 Identifying new prebiotics Prebiotics A selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health. (Gibson et al. 2010) Increasing carbohydrate content of diet has a prebiotic effect Increases numbers of Roseburia group and stimulates butyrate production - is this selective fermentation? Increasing RS III component of diet has a prebiotic effect selective fermentation, increasing numbers of R. bromii and E. rectale - what is benefit on host health? What makes a prebiotic? not always easy to answer

26 Is there a role for new prebiotics to specifically modify the composition of the gut microbiota and improve health? Targeted approach : Novel prebiotics Microbiome studies identify bacteria lacking in disease states Genomic studies identify substrate degradation capabilities In vitro testing to confirm bacterial growth on novel prebiotic In vitro testing to confirm increased population In vivo confirmation microbiota composition and health markers Ultimate requirement: Personalised nutrition based on individual microbial profile Prebiotics can help boost the numbers of key species ALREADY THERE

27 Acknowledgements Jenny Martin Petra Louis Professor Harry Flint Sylvia Duncan Alan Walker Everyone in the microbial ecology group - including numerous visitors and summer students Everyone in the Human Nutrition Unit Genomics section (Gill Campbell, Pauline Young) BioSS (Claus-Dieter Mayer, Grietje Holtrop) Annick Bernalier-Donadille, Christophe Chassard