Transcript dietary fiber pres.

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.
Fiber
Dietary 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
reducing energy density of foods
acting as a substrate for carbohydrate fermentation by the colonic microbiota.
Carbohydrate fermentation results in the production of short chain fatty acids:
Acetate, propionate, and butyrate
Help 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 galactooligosaccharides induce bifidogenic effects within human faecal microbiota.
Microbiota and Health
•The 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 Hypothesis
•Past 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 → 𝐸𝑆𝐹𝐴 𝑟𝑒𝑝𝑜𝑟𝑡 𝑜𝑓 25 𝑔𝑟𝑎𝑚𝑠 𝑜𝑓 𝑓𝑖𝑏𝑒𝑟 𝑝𝑒𝑟 𝑑𝑎𝑦
•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.
Nitrogen Free gas
pumped in to maintain
anaerobic conditions
Nitrogen
RESAZURIN: Indicator of anaerobicity
Culture Medium: Designed to mimic the
most common western-style diet in the UK.
Used a FerMac pH
controller to pump HCl ans
NaOH to maintain pH.
Nitrogen
Nitrogen
Vessel 1
280 mL
Vessel 2
300 mL
Proximal Colon
Transverse Colon
pH 5.5
pH 6.2
Vessel 3
300 mL
Distal Colon
pH 6.8
Methods
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 threefold 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.
Analysis
Analysis used: FISH, SCFA via GC, PCR-DGGE, and statistical analysis of bacteria count.
◦ FISH
◦ Oligonucleotide 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
Discussion
Upon 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 coccoides
faecalibacterium 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 study
Since 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
Conclusion
Mixed 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
SFCA
ACETATE
Acts 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.
propionate
Propionate down-regulates lipogenesis-reduced expression of fatty acid synthase