Gut Microbiota Flashcards
How many organisms do we contain in our body?
100 trillion organisms: mostly bacteria, archaea, eukaryota, (fungi, and protozoa)
Where is the highest concentration of organisms in our body?
colon because we have a low pH in the stomach
Where is the most of our gut bacteria from?
90% from the phyla Firmicutes and Bacteroidetes, other important phyla is Actinobacteria (Bifidobacterium), and Proteobacteria
Are mucosa-associatd bacteria different from luminal bacteria?
Yes
Why do we refer to the colon as a microbial organ?
it contains 150x more genes than the human genome - includes a complex collection of glysocide hydrolases and polysaccharide lyases that break down complex carb linkages into consumable oligosaccharides or monosaccharides
How many % bacteria are we?
90
Proteobacteria
some pathogens
What do bacterias do?
digest indigestable things
5 functions of gut microbiota
enhances energy extraction through fermentation - SCFA production
essental vit synthesis
regulates immune system development
xenobiotic elimination
maintains integrity and function of gastrointestinal barrier
Dysbiosis
altered gut microbiota - could be associated with many diseases/disorders
Obesity and related gut microbiota - 2
decreased in abundance of dominant bacterial phyla -
bifidobacterium, and faecalibacterium prausnitzii
decreased microbiome diversity - high specificity and sensitivity
If bacteria in our digestive system went into the bloodstream
it would be attacked
are we born with gut microbiota?
no, GI tract of a fetus is sterile
Colonization of the infant gut (4)
genotype
mode of delivery - vaginal they get the gut bacteria of mother - lactobacillus prevotella, c-section - staphyfococcus, corynebaterium, propionibacterium, higher susceptibility to certain pathogens (skin/operating room), higher risk of atopic (hypersensitivity) diseases
early life exposure to antibiotics - kills everything
feeding practices - breast fed - increases bifidobacteria, formula fed - increase diversity
microbiota fingerprint established by
age 3 - remains stable
microbiota biome in early childhood - 4
new strains less certain in origin outcompete old ones
rapid increase in diversity
early microbiota development - high instability
shifts in response to diet and illness
adult microbiota biome - 2
highly distinct, differentiated microbiota
continue to change but at a slower rate
elderly microbiota biome
different than young adults
germ free vs germ mice and the amount of food
germ free ate more food 30%
germ ate less but had 40% in body fat
5 strategies to manipulate gut microbiota
prebiotics probiotics synbiotics antibiotics microbiota transplant
prebiotics - 2
effects attribute to - 4
non-digestible food ingredient food for healthy organisms - stimulate growth and metabolic activity - does not benefit from probiotics
- stimulation of beneficial bacteria and SCFA production
- improved barrier function
- suppression of lipogenic enzymes - decreased synthesis of lipoproteins and triglycerides
stimulation of glucagon like peptide secretion
probiotics - what are they, how do they do it? 2 common species
live health promoting organisms - benefit from prebiotics
- directly interact with host cells/indirectly through effects on other bacterial species
bifidobacteria, lactobacillus
synbiotics
combination of a synergistic prebiotic and probiotic
antibiotic
agent to inhibit growth of bacteria
microbiota transplant
transplantation of fecal bacteria
common prebiotics - 3
inulin, fructo-oligosaccharides, galacto-oligosaccharides
potential prebiotics - 3, what kinda diet can you go on?
resistant starch, xylo-oligosaccharides, arabinoxylan-oligosaccharides, high fiber/microbiota-accessible carb diet
6 food examples of prebiotics
bulb of leeks, jerusalem artichokes, jicama, onions, cooked and cooled potatoes, garlic
2 bacterial groups affected by prebiotics
generally bifidobacterium and lactobacillus
other beneficial organisms that may be increased are akkermansia mucinphila and faecalibacterium prausnitzii
what feeds bifidobacterium?
fructose molecule links that we cant break
where do we get resistant starch? -2
cooked and cool potatoes, hard bananas
lean vs obese people microbes in germ free mice
obese would eat less and gain more weight
why are processed foods bad for your biome?
sugars that are absorbed and go right into your blood stream and starve your microbes
how can you tell if a food is high in fibre
things that get stuck in your teeth and are undigestible so lentils and leeks and bukwheat and quinoa
current diet and dietary fibre
huge drop
what nerve communicates between the digestive system and the base of the brain?
vagus
10 days of fast food and your microbe biome
6000 to 3500
how long did it take for the fast food guy to regain his biome diversity?
more than 2 weeks
antibiotics and biome
wipes out everything and the species go down in number, increasing the chances that they will be fat later
chances of being fat and c-section
22%
what other daily activities can increase your biome? -2
playing in dirt and with pets
bariatric surgery and biome
may be more than a new stomach
more ___ of food can increase your microbe biome
diversity
microbes can have widespread impact on?
diverse aspects of a host’s physiology
Microbiata dysbiosis are starring in
growing list of western diseases such as metabolic syndrome
dysbiotic must be accompanied by
the recognition that the definition of a healthy microbiota that should serve a a frame of reference
MACs
microbiota accessible carbs - carbs metabolically available to gut microbes - dietary and resistant to degration and absorption by the host - may come from a variety of sources including plants
MACs for infants
breast milk known as human milk oligosaccharides
most common microbiota fuel for humans and it gives?
dietary plant/dietary fibre - carbs for gut microbrobe fermentation
What can the missing mechanistic explanation for the beneficial effects of dietary fibre be?
fermentation by the microbiota
Scenario for high MAC diet
few simple sugars, microbiota will create SCFA fermentation end products to create microbiota diversity and increase metabolic output - play diverse regulatory role including protection from many western disease
Scenario for low MAC diet
loss of beneficial microbial metabolites such as SCFA and weird microbiota, lower microbiota diversity and leads to western disease
gut microbiota of children from a rural village in Burkina Faso compared to “healthy” estern cohort in Italy - 3
what do they eat?
- altered ration of 2 dominant phyla - increased rep of bacteroidetes relative to Firmicutes
- increased microbiota diversity
- large increases of SCFA production including 4-fold more butyrate and propinoate
twice the dietary fiber
microbiota from traditional agrarian gps compared to western counterparts
more similar to one another in microbiota diversity and SCFA production
link between microbiota diversity and health
unknown, but SCFA is likely a mediator - high MAC ->diversity-> fermentation end products in circulation (short chain FA, acetate, propionate, butyrate)
SCFAs are - 3
acetate, propionate, butyrate - energy source for the colonocytes absorbed by host - kcals salvaged/fermented from inaccessible carbs - also diverse regulatory role
dietary fiber and SCFA can
protect one from diet induced obesity
argument supporting why the ancient microbiota is better
traditional societies have mushc lower rates of western diseases
ability of microbiota to accommodate dietary change (MAC deprivation in generations of developed countries)
deleterious to its own maintenance and our health
metabolic syndrome often preceds
onset of T2D and CV diseases
main barrier between internal sites from luminal antigens is composed of
colonocytes and the seal between them provided by the tight junctions
Microbiota enhances 2
gut barrier function and protects against translocation of bacterial toxins by competition with potential pathogenic bacteria for nutrients
butyrate - 2
SCFA of particular interest for gut barrier function as it is a preferred nutrient for colonocytes - appears to enhance gut barrier function by regulation of TJ proteins and mucins.
prebiotic effect of a food component
stimulate growth of bifidobacteria and lactobacillus
saccharolytic
capable of hydrolyzing a sugar molecule - gut bacteria because humans eat carbs
Metabolic endotoxemia - what is it? mechanism?
endotoxins in blood - could be caused by high fat feeding - increased translocation of gram neg bacteria and bacteria derived components such as LPS into the bloodstream
intake of prebiotic fibres in combo with high fat diet
can counteract diet induced metabolic disturbances
microbiome in metabolically healthy ind appear to be - 3
enriched in bacterial gene functions, metabolism of co-factors and vitamins, and production of butyrate
using qPCR (real time polymerase chain reaction) to characterize the gut microbiota
identified increased abundance of bifidobacteria species in healthy vs obese and T2D
interventions with diff types of dietary fibre including prebiotics has shown to - 3
modulate gut microbiota and improve insulin sensitivity, low-grade chronic inflammation, and lipid metabolism
prebiotics create?
what does it help with?
SCFA - acetate - butyrane - propiate decrease pH
6 mechanisms of prebiotics
gut microbiota - increased bifidobacterium, lactobacillus - increase SCFA and decreases pH improbed gut barrier - increased GLP 2 Reduced inflammation - decreased LPS Reduced adiposity - decrease lipogenesis increased satiety - increased GLP1/PYY -decreased Ghrelin/energy dilution Improved glycemia - increased GLP 1 and decreased visceral adipose tissue
How specific are the beneficial effects of probiotics?
strain specific
5 probiotic mechanisms
gut microbiota - increase strain of probiotic organism - exclusion of pathogenic organisms - reduced inflammation through probiotic interaction with immune cells Improved gut barrier function Reduced inflammation - decreased LPS Reduced adiposity - decreased lipid uptake improved blood lipids - increased bile acid secretion - decrease lipid uptake
extinct organisms in the gut
need to be reintroduced
PA and gut microbiota
increases diversity
Non-caloric artificial sweeteners and gut microbiota
increase insulin resistance
