WEEKS 8&9

Question 1

Define the microbiome

Answer 1

The collective genome of the micro organisms in a particular environment

Question 2

Define microbiota

Answer 2

The community of microorganisms themselves within a particular environment

Question 3

What are commensal microbiota?

Answer 3

The relationship between microbes and their host which is mutually beneficial to both

Question 4

What are probiotics?

Answer 4

Live microorganisms that are administered as supplements

Question 5

What is alpha diversity and how is it achieved?

Answer 5

Alpha diversity is a richness and evenness of species in an environment for optimal health benefits

Achieved by eating a wide range of foods

Question 6

How does microbiome of infants vary with birthing methods?

Answer 6

C section babies’ microbiome resembles that of the mothers skin

Natural babies’ microbiome resembles that of the mothers vagina

Question 7

List factors which can influence composition of microbiome

Answer 7

• age
• drugs
• geography
• birthmode
• breastfeeding
• diet
• exercise
• disease

Question 8

What are the 3 main mechanisms by which the microbiome effect host health?

Answer 8

1. Protection of gut barrier integrity
2. Triggering an innate immune response to structural component of bacteria leading to systemic inflammation
3. Production of metabolites from dietary compounds through fermentation

Question 9

What is dysbiosis

Answer 9

Dysbiosis is an ecosystem where bacteria no longer live in mutual harmony and pathogenic microbes as well as microbial metabolites enter through the epithelial layer, triggering an innate immune response

Question 10

What is eubiosis

Answer 10

there are lots of good bacteria living harmoniously within the ecosystem and low levels of pathogenic species

Question 11

What is the greatest substrate available for fermentation by the gut bacteria?

Answer 11

Resistant starch

Question 12

What occurs when protein is fermented?

Answer 12

Production of TMAOs which are from the bacterial fermentation of choline and carnitine

Increases inflammation, collitis and linked to CVD

Question 13

What are the effects of microbially produced imidazole proprionate?

Answer 13

Produced from histidine by type 2 diabetes associated bacteria

Impaired glucose tolerance by interfering with IRS pathway and GLUT4 recruitment

Question 14

List 5 benefits of short chain fatty acids

Answer 14

1. keeps pH of colon low to inhibit growth of pathogens
2. low pH makes mineral easier to absorb (due to 2+ valence shell)
3. stimulation of pancreatic secretions
4. regulation of colonic epithelial proliferation (preventing colon cancer)
5. modulation of appetite

Question 15

What effect do artificial sweeteners have on the microbiome?

Answer 15

Decrease diversity and change the profile NOT in favour of glucose control

Makes you much more effective at extracting glucose from the diet

Question 16

How does solubility of fibre effect SCFA production?

Answer 16

The higher the solubility the more SCFA production

Question 17

Define the gut-brain axis

Answer 17

The bidirectional communication between the gut and its residents

Question 18

What are the 3 main pathways in which the gut-brain axis operates?

Answer 18

• endocrine
• immune
• neural

Question 19

What effect does cortisol have on the microbiome?

Answer 19

Increases dysbiosis

Tightens enteric cells

Stimulates immune cells to release pro-inflam cytokines

Question 20

TRUE OR FALSE: SCFA can act as neurotransmitters?

Answer 20

TRUE

Question 21

What effect does stress have on the fate of tryptophan?

Answer 21

Less stress: tryptophan → serotonin

More stress: tryptophan → kynurenine

Question 22

What effect does a low vs high casein diet have on microbiome?

Answer 22

Low casein diet: good microbial density, high diversity

High casein diet: increased microbial density, decreased diversity

Question 23

What effect does acetate have on adipose tissue?

Answer 23

↓ lipogenesis

↓ insulin mediated fat accumulation

Question 24

What effect does acetate have on the brain?

Answer 24

↓ BBB permeability

↑ satiety

Question 25

What effect does acetate have on the liver?

Answer 25

↑ insulin sensitivity
↑ AMPK activity
↓ gluconeogenesis
↓ lipid storage

Question 26

What were the outcomes of the microbiota transplant from obese individuals to mice?

Answer 26

The sterile mice who received their microbiome from obese donors:
- harvested more energy from their diet
- had greater body fat
than the mice who received bacteria from lean donors

Question 27

Which species of bacteria reduced in a predominantly meat diet?

Answer 27

Firmicutes

Question 28

What are FODMAPS?

Answer 28

Fermentable oligo, di, mono and polysaccharides

Question 29

What effect does a low FODMAP diet have on microbiome?

Answer 29

If implemented long term can have negative effects on abundance and diversity of microbiome

Question 30

What are prebiotics?

Answer 30

Fermentable dietary constituents which ‘feed’ the bacteria in the microbiome

Question 31

What are probiotics?

Answer 31

Fermented foods and supplements which contain live bacteria used to populate the gut

Question 32

What is fecal transplant?

Answer 32

Fecal microbiota transplant (FMT) is a method to directly change an individuals microbiota to normalize composition. Most commonly applied to those with gastrointestinal disorders

Question 33

Explain what happens in the GBA under stress conditions

Answer 33

The HPA axis increases cortisol secretion from adrenal gland

This causes tightening of enteric muscle cells

Increases gut permeability and thus triggers immune response

Cortisol changes microbiome composition in favour of dysbiosis

Dysbiosis and immune response trigger release of pro-inflammatory cytokines