Session 6 - SIBO / DYSBIOSIS Flashcards
What is the microbiota?
The set of microorganisms that share our body space and may be commensal (derives food from another - helpful to humans), symbionts (associated to a large organism), or pathogens (causes disease).
Where are these microorganisms found?
Skin, mucosa, gastrointestinal, respiratory, urinary tract, vagina and placenta.
What microorganism are vaginally delivered infants enriched in?
Lactobacillus spp (probiotic), which resembles the maternal vaginal microbiota.
What are C-section children colonised by instead?
Staphylococcus, streptococcus, or propionibacteria (skin, mouth and gut)
At what age is a child’s microbiome like an adults?
3 years of age
What influences the gut microbiome across a lifespan?
Diet, medications, stress, exercise, ageing, genetics.
How does stress hormones affect gut bacteria?
Stress can change gut bacteria composition through stress hormones, inflammation, and autonomic alterations. Microbial diversity reduces, promoting pathogen expansion.
What are some of the functions of the microbiome?
Multiple functions:
- Produces short chain fatty acids (SCFAs) to nourish mucosa and stimulate epithelial cell regeneration.
(SCFAs are fuel for colonic cells)
- Contributes to maturation of immune system ( & GALT- gut associated lymphoid tissue)
- stimulates immune responses to defend pathogens
- synthesis and metabolism of certain nutrients, hormones, vitamins.
What nutrients does the microbiome make?
B12, B5, folate and vitamin K
What other systems development in the body does the microbiome influence?
immune, metabolic, and nervous system
What are the types of SCFAs and how are they produced?
Acetate, propionate, butyrate are produced by bacterial fermentation within large intestine from undigested carbs
How does the Gut-Liver axis communicate?
Via the biliary tract, portal vein and systemic meditators.
How does the gut influence the liver?
Metabolites from dysbiosis can cause bacterial translocation to the liver, promoting systemic inflammation and bile acid metabolism.
How does the liver influence the gut?
Liver metabolites such as acetylaldehyde ethanol metabolites are transported to the intestines affecting microbiota.
What pro inflammatory molecule does high levels of bacteria produce in dysbiosis?
Lipopolysaccharide (LPS) - associated with inflammation, diabetes and obesity.
How does the GUT brain axis become imbalanced due to stress? (Bi-directional communication)
Stress causes release of cortisol by HPA:
Affecting immune cells;
Altering gut permeability and barrier function;
Changes gut microbiota composition.
(Anxiety, depression, epilepsy, autism).
How do we clinically modulate/prevent dysbiosis?
Probiotics & soluble fibre (first for 3months) Prebiotics (insoluble fibres) second.
What are some studied probiotics?
Saccharomyces species (boulardii)
Lactobacillus (rhamnosus, etc),
Bifidobacterium (longum etc), &
S.thermophilus (have been found to survive upper GI tract and proliferate colonisation in colon
What are the proposed mechanisms of probiotics?
These microbes:
- enhance intestinal immune response.
- Maintain normal levels of SCFA’s, providing energy to intestinal epithelial cells.
- Modulate immune system function (e.g suppress inflammatory cytokines)
- Repair intestinal permeability.
- Suppress growth of pathogenic bacteria
- Upregulate intestinal electrolyte absorption
What bacteria is the human colon known to be residence of and what chain of carbohydrates?
Bifidobacteria and are observed to be a preference for oligosaccharides
What criteria are used to classify a compound as a probiotic?
- be resistant to acidic pH of stomach, cannot be hydrolyzed or absorbed by GIT
- be fermented by intestinal microbiotia
- the growth or activity of intestinal bacteria can be selectively stimulated.
What dietary fibre is bifidogenic (enhances growth of bifidobacteria?) Give examples
Fructo-oligosaccharides and other fructans.
E.g watermelon, grapefruit, ripe bananas, dates, asparagus, leeks, brussel sprouts, onions.
What probiotics are affective on allergies?
Lactobacillus rhamnosus strain GG (LGG) given prenatally to mothers can reduce atopic eczema in infants =
Biifidobacterium lactis Bb-12 to infants with atopic eczema
T/F - Dietary fibre cannot be digested by human enzymes in the small intestine
True - Dietary fibre (soluble and insoluble) is a diverse group of compounds (including lignin, pectins, resistant starches and other complex carbohydrates) that cannot be digested by enzymes in the small intestines.
T/F - Soluble fibres can lower serum LDL cholesterol concentrations and normalise blood glucose & insulin responses
True - examples include psyllium and fibres found in oats
What are some examples of soluble, viscous/gel forming, readily fermented fibres?
B-glucans from oats and barley, raw guar gum.
What are examples of soluble, viscous/gel forming, nonfermented fibres?
Psyllium
Soluble, nonviscous, readily fermented fibers
Inulin (leeks, asparagus, onions, garlic, chicory, oats, soybeans, artichokes) Oligosaccharides Resistant starches (pasta, legumes such as lentils, chickpeas, kidney beans, starchy vegetables).
When does the first major exposure of a new-born to microbes occurs?
During the birthing process
What gut population does a newborn gain after vaginal delivery?
Lactobacillus (consistent with vaginal bacteria)
T/F Bi-directional communication happens in the gut-brain axis only
False - It happens in the gut liver axis too
Gut dysbiosis is associated with which of the following human diseases?
Mental health such as anxiety
Metabolic conditions such as diabetes
Liver disorders such as NAFLD
T/F: Supplementation with Lactobacillus rhamnosus strain prenatally does not have any effect of prevalence of eczema among infants born to those mothers.
False – Lactobacillus rhamnosus supplements has been shown to reduce the prevalence of eczema in new-borns.
T/F Prebiotics are fibre, however not all fibre are prebiotics
True
Which fibres are proven to produce more butyrate compared to oligosaccharides?
Resistant starches (FOS) Butyrate is a four-carbon short-chain fatty acid that is produced through microbial fermentation of dietary fibres (predominantly resistant starches) in the lower intestinal tract.
What are the mechanisms of action of prebiotics?
- Food for probiotics
- Allow healthy microbiota to generate short chain fatty acids such as butyrate (generating butyrate)
- down regulate inflammation/disease preventive benefit
List 2 diseases associated with gut dysbiosis
NAFLD Diabetes IBS/ leaky gut Anxiety Eczema
