High-level dietary fibre - PowerPoint Presentation

Slide1

High-level dietary fibre up-regulates colonic fermentation and relative abundance of saccharolytic bacteria within the human faecal microbiota in vitro

By: Hannah

hankins

Large Intestines, Microbiota, and Fiber

Large intestines/Colon: Last part of the Digestive System. Responsible for removing the remaining water and nutrients from food before it is excreted. Absorb vitamins created by colonic bacteria

Gut Microbiota: microscopic organisms living in the gut. About 10^11-10^12 bacteria in the colon. They compose up to 60% of your feces.

Fiber: fiber is the edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small

intestine

.

FiberDietary fiber is suggested to impact human energy metabolism in a number of ways including:regulation of intestinal transit time,

digestive function through bulking and gel-form activities

r

educing energy density of foods

acti

ng as a substrate for carbohydrate fermentation by the colonic microbiota. Carbohydrate fermentation results in the production of short chain fatty acids:

Acetate, propionate, and butyrateHelp regulates lipogenesis, act as an energy source for the gut, regulate gut hormones, and impact fat storage.

Certain types of dietary fiber like oligosaccharides, inulin, fructo

-oligosaccharides and

galacto

-oligosaccharides induce bifidogenic effects within human

faecal

microbiota.

Microbiota and HealthThe intestinal microbiota has been linked to the aetiology or maintenance of many chronic diseases.

Bowel disease

Colon cancer

Diseases associated with obesity.

Increasing production of beneficial bacteria like

bifidobacterium

and lactobacillus may increase immunity, vitamin production, and inhibit pathogens.

Objectives and HypothesisPast study done in rural Africa found that children who consumed plant based diets rich in different types of fiber had a distinct microbiota composition, mainly

saccharolytic

bacteria. Found three times the amount of SCFA in the

faeces

of the

the Africans compared to a European diet.8grams

see the

impact of increasing total dietary

fibre

by

threefold (3x the normal western diet)

on the composition and metabolic activities of human gut

microbiota.

Use an

in vitro (non-living) three stage continuous culture system to mimic the colon and simulate the effects of different amounts fiber on the gut.

Vessel 1

280 mL

Vessel 2

300 mL

Vessel 3

300 mL

Proximal Colon

Transverse Colon

Distal Colon

pH 5.5

pH 6.8

pH 6.2

Culture Medium: Designed to mimic the most common western-style diet in the UK.

RESAZURIN: Indicator of

anaerobicity

Nitrogen

Nitrogen

Nitrogen

Nitrogen Free gas pumped in to maintain anaerobic conditions

Used a

FerMac

pH controller to pump

HCl

ans

NaOH

to maintain

pH.

Inoculated with 100ml of 20% Faecal

Inocula

(2 males and 1 female)and pre-reduced PBS.

Fermented in three phases (Steady States). Retention time was 36 hours long.

1. Gut Models were fed with a standard medium with initial level of dietary

fibre

content.2. The level of fiber was increased three-fold with starch, inulin, guar gum,

xylan, pectin, and arabinogalactin.

3. Level of fiber reduced and allowed back to normal.

Samples were taken for four consecutive days for bacterial and short chain fatty acids analysis.

Methods

AnalysisAnalysis used: FISH, SCFA via GC, PCR-DGGE, and statistical analysis of bacteria count. FISHOligonucleotide probe to recognize certain microbiota

5890 Series GC

system

calculated Short Chain Fatty acids from culture.

PCR-DGGE

PCR: amplifies replication of specific segments of DNA based on primers applies DGGE: Denaturing Gradient Gel Electrophoresis- banding patterns can be used to visualize variations in microbial genetic diversity

Results

FISH analysis shows the mean changes in bacterial changes.

5890 Series GC system to show changes in SCFA production

Results

banding patterns

show variations

in microbial genetic

diversity.

More/thicker bands show more diversity/presence of microbiota

Binary Data Matrix and PCA

Generated by the presence or absence of DGGE bands

Red-Steady State 1

green- Steady State 2

black- Steady State 3

DiscussionUpon the high fiber supplementation there was a relative abundance of:Bifidobacterium (p<0.05)

Associated

with improved biomarkers of CVD and colon cancer.

Eubacterium

rectale-clostridium coccoidesfaecalibacterium prausnitzii

(p<0.05) proximal colon (vessel 1)Produce a majority of butyrate in the colon. faecalibacterium prausnitzii aids in maintaining colonic health and reducing chances of inflammatory bowel diseases. Helps with the secretion of metabolites able to block NF-

kB and IL-8 production.Lactobacillus/enterococcus (p<0.05)Ruminococcus

(

p<0.05)

Adheres

to starch particles and digests cellulose

Carbohydrate rich environment increased the growth of this bacterium.

Implies the bacteria is sensitive to modulation created by starch/carbohydrate-rich diets.

Possible future studies and limitations of this studySince the study is In vitro, it lacks: - human cell or immune interactions- no capacity to mimic absorption of organic acids and other microbiota metabolites or conversely,

- hosts secretions and water absorption.

It has a small sample size (2 males and one female)

FUTURE STUDIES: How different

enterotypes

respond to high fiber availability

ConclusionMixed fiber consumption intake has a beneficial effects on the human gut microbiota composition.

Continuous consumption of large quantities of high fiber foods can improve colonic health and overall well being.

What to Take From This

FIBER IS YOUR FRIEND!!!

DON’T BE AFRAID TO MIX IT UP A BIT!

END

SFCAACETATEActs as a substrate for hepatic de novo lipogenesis

via

acetyle-coa

and fatty acid synthase

BUTYRATE

butyrate is a major energy source for colonic mucosa. May enhance adaptive thermogenesis thus increasing energy expenditure to control body weight and markers of metabolic syndrome.

propionatePropionate down-regulates lipogenesis-reduced expression of fatty acid synthase