The Gut Microbiome in Metabolic Disorders Flashcards

1
Q

What is the microbiome?

A

Collection of microorganisms and their genes and proteins living within our mucosae, skin, and secretions

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2
Q

What is the exposome?

A

Environment

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3
Q

What are the two most dominant phyla in the colons of healthy adults?

A

Firmicutes

Bacteroidetes

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4
Q

What are the Firmicutes mainly made of?

A

Gram positive Clostridia

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5
Q

What are the Bacteroidetes mainly made of?

A

Gram negative Bacteroides

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6
Q

Are the less important phyla functionally important?

A

Yes

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7
Q

What are the two approaches to sequencing the microbiome?

A

16S ribosomal sequencing

Metagenomic shotgun sequencing

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8
Q

How does 16S ribosomal sequencing work?

A

Takes areas common to most bacteria in 16S ribosomal subunit gene and amplifies it
Those areas that are different are also amplified
On this basis, bacteria can be separated

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9
Q

What is the speed and ease of 16S ribosomal sequencing?

A

Simple
Fast
Straightforward to analyse

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10
Q

What does 16S ribosomal sequencing report?

A

Operational taxonomic units, not sequences of species

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11
Q

Does 16S ribosomal sequencing resolve well at the species level?

A

No

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12
Q

What are the shortcomings of 16S ribosomal sequencing?

A

May fail to resolve substantial fraction of diversity
Not ID novel/highly diverged microbes
Can’t resolve biological functions associated with taxa

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13
Q

How does metagenomic shotgun sequencing work?

A

Microbial and human DNA separated

Microbial DNA randomly sheared into short segments > sequenced > re-assembled

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14
Q

Does metagenomic shotgun sequencing reveal microbial genes that are active?

A

No, only those that are present

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15
Q

What is alpha diversity?

A

Measure of species diversity within sample

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16
Q

What is beta diversity?

A

Measure of diversity between samples

17
Q

What is dysbiosis?

A

Disturbance/imbalance in biological system

18
Q

How is a newborn baby seeded with microbiota?

A

Vagina
Gut
Skin
Breast milk

19
Q

What are the dominant species in the vagina with which the baby is seeded?

A

Lactobacillus

Prevotella

20
Q

What does a healthy microbiome do in a baby?

A
Induces maturation and maintains integrity of
- Gut
- Immune system
- Neurological system
- Others
Protects against infection
Produces nutrients and vitamins
Utilises energy > regulates metabolism and weight
21
Q

What happens to the breast milk microbiome after elective C-section?

A

Altered

22
Q

What childhood diseases is C-section associated with?

A

Allergic rhinitis
Asthma
Coeliac disease
Type 1 diabetes

23
Q

What evidence is there to show that the microbiome regulates development of type 1 diabetes?

A

Incidence of T1D in wild mice very low
More than half of mice reared in specific pathogen free environments developed T1D
All mice reared in germ-free environment, and had no microbiome, developed T1D

24
Q

What does diet protection against autoimmune diabetes need?

A

Microbiome

25
Q

What is the relationship between gut microbial diversity and seroconversion to clinical type 1 diabetes?

A

Decrease in diversity with seroconversion

Significant decrease in diversity with diagnosis T1D compared to controls

26
Q

How does the gut microbiome change in children with type 1 diabetes?

A

Diversity decreases
Actinobacteria and Firmicutes decreased
Bacteriodetes increased
Butyrate-producing species within Clostridium decreased

27
Q

How are short-chain fatty acids, such as butyrate, produced?

A

Bacteria ferment undigested starch

28
Q

What do short-chain fatty acids do?

A
Maintain epithelial integrity
Absorbed > go to
- Liver
- Muscle
- Brain
- Etc
Anti-inflammatory
- Bind and activate GTRs
- Inhibit histone deacetylases
29
Q

How does a fast food diet change the gut microbiome?

A

Decreases diversity

Has many additives affecting microbiome

30
Q

What is the gut microbiome like in type 2 diabetes?

A

Fewer butyrate-producing bacteria

More opportunistic pathogens > can cause infections

31
Q

What is a better predictor of insulin resistance than BMI?

A

Metagenomic signature

32
Q

Is there evidence that a faecal microbiota transplant cures anything?

A

No clear evidence that it cures anything except recurrent C difficile infection

33
Q

How did things change in people with metabolic syndrome with the transfer of gut microbiota from lean donors?

A

Increased insulin sensitivity
Increased diversity in faecal microbiome
Butyrate-producing bacteria increased

34
Q

Is obesity transmissible by gut bacteria?

A

Yes

35
Q

What are the issues with probiotics?

A

Contain only few bacteria
Evidence for passage to large bowel
Varying resistance to acid and bile across species and strains
Lack of randomised clinical trials

36
Q

What are prebiotics?

A

Food parts that promote specific changes in growth/activity of gut bacteria to confer health benefit to host
Examples
- Non-digestible carbohydrates
- Phytochemicals = chemicals in plants