The Gut Microbiota in Health and Disease Flashcards
Where in the GIT does the food spend the longest amount of time?
Large intestine (10h-several days)
What happens to oxygen concentration as you go further down the GIT?
Increasingly less oxygen
Are the bacteria in the large intestine aerobic or anaerobic?
Anaerobic
Which part of the GIT has the most bacteria?
Large intestine
What is the reason that everyone has a different microbial composition?
Everyone has a different diet, the food we eat=microbial food
What does the GIT microbiota do?
-Defence against pathogens
-Metabolism of dietary components
-Modification of host secretions
-Host signalling
-Development of immune system
-Production of metabolites which are essential for health
What does processed junk food supply the microbiota with?
Very little, refined sugars so nothing to feed on
What food is best for our gut microbiota?
Fibre rich foods, fruits and vegetables, pulses, wholegrains
Which part of the GIT is the most energy absorbed from?
Stomach and small intestine >70% of energy uptake
What are the benefits of dietary fibre?
HEALTH AND FOOD TECH LETS GOOOOO
-Provides faecal bulk
-Contains anti-oxidants, phytochemicals and vitamins
-Assists with bacterial fermentation
Why do we want a very diverse microbiome?
Different bacteria play different roles, the more roles, the better
What are the main products of carbohydrate metabolism by the microbiota?
Short chain fatty acids
Gases
Name three short chain fatty acids which can be produced by carbohydrate metabolism.
Acetate
Propionate
Butyrate
Name three gases produced due to the carbohydrate metabolism by the microbiota.
Carbon dioxide
Hydrogen
Methane
Which site of the large intestine does most of the bacterial fermentation happen in?
Proximal/right side
Which site of the large intestine does most of the intestinal disease?
Distal/left side
What are the products of protein metabolism in the large intestine?
Branched chain fatty acids
Gases
Phenols, indoles, amines
What are more damaging- SCFA or BCFA?
Branched chain fatty acids
Name two branched chain fatty acids which are produced in the large intestine during protein synthesis.
Iso-butyrate
Isovalerate
Name two gases which are produced in the large intestine during protein synthesis.
Ammonia
Hydrogensulphate
So, would more carbohydrate or protein in the body help with better products from metabolism by the microbiota?
Carbohydrate- less harmful products
What is the ratio of the SCFA’s produced by the carbohydrate metabolism?
1:1:3
Butyrate : propionate : acetate
What is the function of butyrate?
Epithelial cell growth and regeneration
What is the function of propionate?
Gluconeogenesis in liver
Satiety signalling*
Satiety signals are relayed to the hindbrain, either indirectly via nerves such as the vagus from the GI tract
What is the function of acetate?
Transported in blood to peripheral tissues to assist with lipogenesis.
What are some of the local effects of bacterial fermentation?
Lowering of pH: increased calcium absorption and pathogen inhibition
Increased faecal bulking
SCFA production
At what pHs do bacteria usually grow best in?
pH >6
If there is a higher pH, will there be more protein metabolism or carbohydrate metaboslim?
Protein metabolism
-> think, proteins denature at higher pH…idk if this is why but might help to remember
Describe how the barrier effect helps resist against pathogens.
Large numbers of indigenous microbiota prevent colonisation by ingested pathogens.
Also, they inhibit the overgrowth of potentially pathogenic bacteria which is normally resident at lower levels.
Describe how active competitive exclusion helps resist pathogens.
Commensal microbes produce substances that interact with pathogenic bacteria and kill them off
What are some of the systemic effects of bacterial fermentation?
SCFA and other metabolites go into bloodstream before being transported to the liver or brain.
Short chain fatty acids are have an important role as molecules, what is this?
They are signalling molecules impacting on gut, metabolic, brain and overall health
What is the role of the receptors in gut epithelial cells?
Detect SCFA’s and secrete hormones
What are the GPR43/FFAR2 receptors activated by?
Acetate and propionate > butyrate
What do the GPR43/FFAR2 receptors cause to happen once activated?
Secretes GLP-1 which inhibits fat accumulation
What are the GPR41/FFAR3 receptors activated by?
Propionate and butyrate
What do the GPR41/FFAR3 receptors cause to happen once activated?
Secretes PPY which improves insulin resistance and satiety signalling to the brain.
What are the GPR109A receptors activated by?
Butyrate
What do the GPR109A receptors cause to happen once activated?
Supresses colic inflammation and carcinogenesis
What role does the commensal bacteria found close to the GIT epithelium have?
Blocks and prevents the adhesion or colonisation of pathogens
How does the outer mucous layer of the GIT help with immuinity?
Barrier effect
How does the inner mucus layer of the GIT help with immuinity?
Prevents bacterial penetration
How does the postnatal immune system develop?
By exposure to certain bacteria/pathogens
List some of the central nervous system conditions which have been linked to a disruption in the gut microbiota.
Autism spectrum disorders
Multiple sclerosis
Major depressive episodes
List some of the gastrointestinal conditions which have been linked to a disruption in the gut microbiota.
IBD (CD, UC)
IBS
NAFLD
Cirrhosis
List some of the metabolic conditions which have been linked to a disruption in the gut microbiota.
Obesity
CHD
Insulin resistance (T2D)
Obesity
List some of the immune conditions which have been linked to a disruption in the gut microbiota.
Allergies
Auto-immune diseases
Cancer immunotherapy
What is the cause of a lot of conditions relating to the gut microbiota?
Lack of different microbiota
How can antibiotics affect the gut microbiome>?
Reduces bacterial diversity
Increases enterobacteria which cause inflammation
Does selective pressure increase or decrease diversity of microbacertia?
Decreases it
Antibiotics can lead to pathogen colonisation. Which pathogen is particular can become more abundant after antibiotics and results in infections?
C.difficile
What is FMT?
Faecal microbiota transplationation
What does FMT help to do?
Restore the microbiota and helps to prevent reinfection
How can we increase the diversity of microbiota in terms of diet?
Increase fibre
Reduce processed foods
Low carb diets = less bacteria
What are probiotics?
Live microorganisms which when administrated in adequate amounts, can have a positive health benefit in the individual
aka live bacteria added to food
What are prebiotics?
A substrate which is selectively utilised by host organisms conferring a benefit.
aka food for resident bacteria
Do all probiotics have the same function?
No- some have widespread mechanisms but some are niche.
Widespread= competitive exclusion from pathogens
Rare= production of vitamins
How can prebiotics help with satiety signalling?
Prebiotics stimulate SCFA production which interact w immune cell receptors.
List the external influences on the gut microbioma.
Diet
Antibiotics
Probiotics/prebiotics
