The Gut Microbiota in Health and Disease

Question 1

Where in the GIT does the food spend the longest amount of time?

Answer 1

Large intestine (10h-several days)

Question 2

What happens to oxygen concentration as you go further down the GIT?

Answer 2

Increasingly less oxygen

Question 3

Are the bacteria in the large intestine aerobic or anaerobic?

Answer 3

Anaerobic

Question 4

Which part of the GIT has the most bacteria?

Answer 4

Large intestine

Question 5

What is the reason that everyone has a different microbial composition?

Answer 5

Everyone has a different diet, the food we eat=microbial food

Question 6

What does the GIT microbiota do?

Answer 6

-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

Question 7

What does processed junk food supply the microbiota with?

Answer 7

Very little, refined sugars so nothing to feed on

Question 8

What food is best for our gut microbiota?

Answer 8

Fibre rich foods, fruits and vegetables, pulses, wholegrains

Question 9

Which part of the GIT is the most energy absorbed from?

Answer 9

Stomach and small intestine >70% of energy uptake

Question 10

What are the benefits of dietary fibre?

Answer 10

HEALTH AND FOOD TECH LETS GOOOOO

-Provides faecal bulk
-Contains anti-oxidants, phytochemicals and vitamins
-Assists with bacterial fermentation

Question 11

Why do we want a very diverse microbiome?

Answer 11

Different bacteria play different roles, the more roles, the better

Question 12

What are the main products of carbohydrate metabolism by the microbiota?

Answer 12

Short chain fatty acids
Gases

Question 13

Name three short chain fatty acids which can be produced by carbohydrate metabolism.

Answer 13

Acetate
Propionate
Butyrate

Question 14

Name three gases produced due to the carbohydrate metabolism by the microbiota.

Answer 14

Carbon dioxide
Hydrogen
Methane

Question 15

Which site of the large intestine does most of the bacterial fermentation happen in?

Answer 15

Proximal/right side

Question 16

Which site of the large intestine does most of the intestinal disease?

Answer 16

Distal/left side

Question 17

What are the products of protein metabolism in the large intestine?

Answer 17

Branched chain fatty acids
Gases
Phenols, indoles, amines

Question 18

What are more damaging- SCFA or BCFA?

Answer 18

Branched chain fatty acids

Question 19

Name two branched chain fatty acids which are produced in the large intestine during protein synthesis.

Answer 19

Iso-butyrate
Isovalerate

Question 20

Name two gases which are produced in the large intestine during protein synthesis.

Answer 20

Ammonia
Hydrogensulphate

Question 21

So, would more carbohydrate or protein in the body help with better products from metabolism by the microbiota?

Answer 21

Carbohydrate- less harmful products

Question 22

What is the ratio of the SCFA’s produced by the carbohydrate metabolism?

Answer 22

1:1:3

Butyrate : propionate : acetate

Question 23

What is the function of butyrate?

Answer 23

Epithelial cell growth and regeneration

Question 24

What is the function of propionate?

Answer 24

Gluconeogenesis in liver
Satiety signalling*

Satiety signals are relayed to the hindbrain, either indirectly via nerves such as the vagus from the GI tract

Question 25

What is the function of acetate?

Answer 25

Transported in blood to peripheral tissues to assist with lipogenesis.

Question 26

What are some of the local effects of bacterial fermentation?

Answer 26

Lowering of pH: increased calcium absorption and pathogen inhibition Increased faecal bulking SCFA production

Question 27

At what pHs do bacteria usually grow best in?

Answer 27

pH >6

Question 28

If there is a higher pH, will there be more protein metabolism or carbohydrate metaboslim?

Answer 28

Protein metabolism -> think, proteins denature at higher pH...idk if this is why but might help to remember

Question 29

Describe how the barrier effect helps resist against pathogens.

Answer 29

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.

Question 30

Describe how active competitive exclusion helps resist pathogens.

Answer 30

Commensal microbes produce substances that interact with pathogenic bacteria and kill them off

Question 31

What are some of the systemic effects of bacterial fermentation?

Answer 31

SCFA and other metabolites go into bloodstream before being transported to the liver or brain.

Question 32

Short chain fatty acids are have an important role as molecules, what is this?

Answer 32

They are signalling molecules impacting on gut, metabolic, brain and overall health

Question 33

What is the role of the receptors in gut epithelial cells?

Answer 33

Detect SCFA's and secrete hormones

Question 34

What are the GPR43/FFAR2 receptors activated by?

Answer 34

Acetate and propionate > butyrate

Question 35

What do the GPR43/FFAR2 receptors cause to happen once activated?

Answer 35

Secretes GLP-1 which inhibits fat accumulation

Question 36

What are the GPR41/FFAR3 receptors activated by?

Answer 36

Propionate and butyrate

Question 37

What do the GPR41/FFAR3 receptors cause to happen once activated?

Answer 37

Secretes PPY which improves insulin resistance and satiety signalling to the brain.

Question 38

What are the GPR109A receptors activated by?

Answer 38

Butyrate

Question 39

What do the GPR109A receptors cause to happen once activated?

Answer 39

Supresses colic inflammation and carcinogenesis

Question 40

What role does the commensal bacteria found close to the GIT epithelium have?

Answer 40

Blocks and prevents the adhesion or colonisation of pathogens

Question 41

How does the outer mucous layer of the GIT help with immuinity?

Answer 41

Barrier effect

Question 42

How does the inner mucus layer of the GIT help with immuinity?

Answer 42

Prevents bacterial penetration

Question 43

How does the postnatal immune system develop?

Answer 43

By exposure to certain bacteria/pathogens

Question 44

List some of the central nervous system conditions which have been linked to a disruption in the gut microbiota.

Answer 44

Autism spectrum disorders Multiple sclerosis Major depressive episodes

Question 45

List some of the gastrointestinal conditions which have been linked to a disruption in the gut microbiota.

Answer 45

IBD (CD, UC) IBS NAFLD Cirrhosis

Question 46

List some of the metabolic conditions which have been linked to a disruption in the gut microbiota.

Answer 46

Obesity CHD Insulin resistance (T2D) Obesity

Question 47

List some of the immune conditions which have been linked to a disruption in the gut microbiota.

Answer 47

Allergies Auto-immune diseases Cancer immunotherapy

Question 48

What is the cause of a lot of conditions relating to the gut microbiota?

Answer 48

Lack of different microbiota

Question 49

How can antibiotics affect the gut microbiome>?

Answer 49

Reduces bacterial diversity Increases enterobacteria which cause inflammation

Question 50

Does selective pressure increase or decrease diversity of microbacertia?

Answer 50

Decreases it

Question 51

Antibiotics can lead to pathogen colonisation. Which pathogen is particular can become more abundant after antibiotics and results in infections?

Answer 51

C.difficile

Question 52

What is FMT?

Answer 52

Faecal microbiota transplationation

Question 53

What does FMT help to do?

Answer 53

Restore the microbiota and helps to prevent reinfection

Question 54

How can we increase the diversity of microbiota in terms of diet?

Answer 54

Increase fibre Reduce processed foods Low carb diets = less bacteria

Question 55

What are probiotics?

Answer 55

Live microorganisms which when administrated in adequate amounts, can have a positive health benefit in the individual aka live bacteria added to food

Question 56

What are prebiotics?

Answer 56

A substrate which is selectively utilised by host organisms conferring a benefit. aka food for resident bacteria

Question 57

Do all probiotics have the same function?

Answer 57

No- some have widespread mechanisms but some are niche. Widespread= competitive exclusion from pathogens Rare= production of vitamins

Question 58

How can prebiotics help with satiety signalling?

Answer 58

Prebiotics stimulate SCFA production which interact w immune cell receptors.

Question 59

List the external influences on the gut microbioma.

Answer 59

Diet Antibiotics Probiotics/prebiotics