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NUTR 3360 > Module 4: Gut Bacteria > Flashcards

Module 4: Gut Bacteria Flashcards

1
Q

3 core function of a healthy microbiome

A
  1. breakdown of dietary fiberes
  2. production of short chain fatty acids (propionate, acetate, butyrate)
  3. production of vitamins and other co-factors
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2
Q

2 ways to study the gut microbiome

A
  1. Traditional culturing
    - bacteria grown in petri dish
    -away from communities
  2. Classification using SSU rRNA
    -SSU rRNA reads mRNA, determines evolutionary relationdship s
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3
Q

Traditional culturing limitations/challenges

A

-O2 rich environments
-growing individual bacteria apart from their communities

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4
Q

SSU rRNA approach limitations/challenges

A
  1. Analysis done w fecal famples-microbes that reside in other regions of gut can be missed (eg. small intestine)
    2.Comparisons made w “healthy” gut
    3.Identification vs function
    -can tell what microbes are present, no info on what they do
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5
Q

2 ways to define healthy gut

A

1.stability
- resist change in face of stress
- return to equilibrium following stress-induced perturbation
2. Diversity
-range of species with a range of functions

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6
Q

Metagenomics

A

Application of modern genomics techniques to the study of communities of microbial organisms directly in their natural environment
-bypasses need for isolation and lab cultivation

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7
Q

2 branches of metagenomics

A
  1. Sequence-based
    - Determine what genes are
    2.Function-based
    - Determine what genes do
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8
Q

Sequence-based metagenomics

A

-sequence DNA to create a “catalogue of genes” present
-investigate genetic potential to predict functions

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9
Q

Function based metagenomics

A

-discoever new functions
-work backwards to figure out genes underlying functions

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10
Q

Upside & downside of function-based metagenomis

A

Upside: discover new biological advances
Downside: laborious and time consuming

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11
Q

Establishing the gut microbiome –> birth - first few years) aerobic/anaerobic

A

-Fetile intesine is sterile
-initial O2 abundance in newborn gut influences first colonizers
(gut environ favours aerobic bacteria)
-As they grow/expand O2 consumed
(gut environ now favours anaerobic)
-In a few years: anaerobic >aerobic

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12
Q

3 factors that have a significant impact on infant gut bacteria development

A
  1. Mode of delivery
  2. Antibiodics
  3. Diet
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13
Q

Mode of delivery affect on infant gut bacteria

A

Vaginal: colonized with vaginal and distal gut bacteria of mom
C-section: colonized by skin bacteria of the mom

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14
Q

Antibiotics affect on infant gut bacteria

A

Alters microbial diversity and number

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15
Q

Newborn diet affect on infant gut bacteria (breast fed vs formula)

A

Breast milk: bacteria and HMO - promote growth of specific microbial communities
Formula feeding + probiotic use can show similar microbial community to breast fed

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16
Q

Example of HMO on microbial community

A

encourage growth of Bifidobacterium
-inhibit growth of pathogenic organisms, maintain mucosal barrier function, regulate inflammatory respoonses

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17
Q

Core gut microbiome

A

Basic functions shared by bacteria from all people
-basic cell functions
-energy harvesting (sugars to SCFA)
-degrades xenobiotics (foreign substancess)
-vitamin production

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18
Q

Short-chain fatty acids and what they do

A

Acetate C2:0 - influence cholesterol and fatty acid production
Propionate C3:0 - used by liver for gluconeogenesis
Butyrate C4:0 - used for energy for intestinal enterocytes

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19
Q

Gut bacteria and obesity relation

A

Obesity = less diversity in gut bacteria

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20
Q

When in life is gut bacteria more stable?

A

Adulthood
-decrease in infancy and old age

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21
Q

When is gut bacteria the most diverse

A

childhood - late senior

22
Q

Probiotic

A

Live microorganisms that when administered in adequate amounts confer a health benefit on the host

23
Q

Prebiotic

A

A substrate that is selectively utilized by host microorganisms conferring a health benefit

24
Q

Synbiotic

A

A mixture, comprimising live microorganisms and substrate(s) selectively utilized by host microorganisms, that confers a health benefit on the host

25
Q

Does the presence of gut bacteria influence mouse body weight?

A

Gut bacteria presence associated with higher body fat and larger fat pads

26
Q

Gut bacteria and plasma markers of metabolism

A

Gut bacteria associated w higher fasting leptin, insulin and glucose levels in blood

27
Q

Gut bacteria and hepatic production of TAGs

A

Gut bacteria associated w more liver triglycerides and greater expression of hepatic genes (involved in de novo lipogensis)

28
Q

Gut bacteria and adipocyte lipid storage

A

-LPL hydrolyzes blood TAG -allows for fatty acid takeup into adipocyte
-LPL inhibited by FIAF
-Gut bacteria suppress FIAF production
-Higher LPL = higher body weight (increased fat storage)

29
Q

Is obesity associated w changes in the gut microbiota in mice?

A

Obese mice showed:
-reduction in bacteriodetes
-increase in fermicutes

30
Q

How do firmicutes efficiently extract energy from food

A

-rich in glycoside hydrolases (digest dietary starch)
-enriched with proteins that impoart glycoside hydrolases, metabolize them and generate SCFA

31
Q

Are obese or lean mice more efficient at extracting energy from food?

A

Obsese mice
-less energy remaining in feces relative to lean mice

32
Q

Can gut microbiota be remodelled by fecal transplants?

A

-obese patients received transplant from lean healthy donor, microbiome shifted to that of lean donor
-increased microbial diversity
-bile acids reduced

33
Q

Do gut microbiota influence diet-induced obesity

A

-Germ free mice resistant to diet-induced obesity

34
Q

Germ free vs conventional mice TAG

A

Germ free mice have higher levels of blood TAG

35
Q

Relationship between gut bacteria and fat oxidation in liver and muscle

A

Fat oxidation reduced in animals w gut bacteria by reducing AMPK signalling

36
Q

AMPK activation promotes (1)

A

Fat oxidation

37
Q

FIAF

A

LPL inhibitor

38
Q

LPL

A

encourage TAG uptake into adipose tissue

39
Q

Glycoside hydrolases

A

Enzymes needed for digestion of complex plant polysaccharides
-human genome poor
-microbial genome rich(bacteria efficient at breaking down to produce SCFA)

40
Q

SCFA - what pathway do they activate

A

-signalling molecules
-activate GPR41 pathwas

41
Q

GPR41-/- mice

A

-energy content in feces higher
-more SCFA in cecum and feces

-weakens energy absorption

42
Q

GPR41 and body weight relationship

A

GPR41-/- -colonized with gut bacteria weight less
GPR41 +/+ - weigh more

43
Q

Can dietary habits (animal vs. plant based) shape human gut bacteria?

A

Animal: rapidly changed bacterial community
Plant: did not

44
Q

Mango study 280g/day on plasma metabolic markers and gut microbiome

A

-3.5% reduction in SBP, 10.5% reduction in 2hr pl glucose
-Increased abundance of specific species, enhanced gut microbial diversity

45
Q

Diet-induced or genetic obesity is characterized by(3)

A

-low-level chronic inflammation
-increased expression/secretion of cytokines ans chemokines (TNF-a, IL-6, etc)
*cytokines promote crosstalk between tissues = insulin resistance

46
Q

What does LPS impact

A

Gut permeability
(High LPS = high gut perm)

47
Q

LPS production/transportation

A

-Produced by death of gram-negative bacteria (bacteroidetes)
-Transported out of intestine and through body bound to LPS-binding proteins

48
Q

What does LPS interact with/what does it do

A

Interacts with receptor CD14 on immune cells, increases production of pro-inflammatory cytokines

49
Q

HFD and LPS

A

HFD increases blood LPS levels
–> higher body weight & fat pads, higher bl glucose and insulin, whole body insulin resistance
–> increased inflammatory markers

50
Q

CD14-/-

A

No change in inflammatory markers, no change in body weight, no change in blood glucose or liver fat

51
Q
A

NUTR 3360 (11 decks)

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