Microbiome/Diarrhoea

Question 1

what reduces bacterial growth in the gut?

Answer 1

gastric acid
bile acids
propulsive motility
pancreatic enzymes

(bowel overgrowth - abdominal pain, bloating, diarrhoea)

Question 2

name some of the risk factors for SI bacterial overgrowth (SIBO_

Answer 2

structural/anatomical abnormality
gastric resection
motility disorders
coeliac disease
diabetes
gastric acid suppression
crohns disease

Question 3

generally describe bacteria in the LI

Answer 3

stagnant motility (up to 3 days to move through colon)
pH 4.5-7
binds to mucous/mucosa
99% anaerobic
over 1000 species

Question 4

describe the functions of gut bacteria

Answer 4

ferment carbohydrates
produce short chain fatty acids
reduce pH
inhibit pathogens
produce vitamins
metabolise polyphenols (produce phenolic acids)
educate immune system

Question 5

expain fermanetation

Answer 5

anaerobic carb/protein metabolism by microbiota to short chain fatty acids
(mainly dietary fibre, glucans, pectins, sugar alcohols, prebiotics/insulin)

Question 6

explain the role of short chain fatty acids in the colon

Answer 6

acetic, propionic, butyric, lactic acid and branched types

promote absorption (reduce diarrhoea)
provide energy (influence hormone release)
protect/heal gut mucosa
influence lipid metabolism

Question 7

describe propionate in the colon

Answer 7

inhibits cholesterol synthesis
inhibits lipid synthesis (if acetate ratio increased)
increases insulin sensetivity
influences hormones (GPCR)

Question 8

describe acetate in the colon

Answer 8

main SCFA reaching systemic blood
used for energy
increases hepatic lipogenesis

Question 9

describe butyrate in the colon

Answer 9

preferred fuel for colonic cells
promotes healthy mucosa (improves gut barrier function)
heals damaged mucosa
may be anti cancer (stimulates apoptosis etc.)

Question 10

explain the consequences of a low colonic pH

Answer 10

reduced by fermentation (proximal more acidic than distal)
low pH inhibits harmful enzymes and precipitates harmful molecules (fatty soaps, bile acids)
increases cell proliferation
increases Ca and Mg absorption
inhibits pathogens

Question 11

what are the harmful effects of colonic bacteria?

Answer 11

releases toxins/carcinogens
produces hydroxy fatty acids
produces NH3, phenols

Question 12

define prebiotics

Answer 12

carbs or other compounds which stimulate growth of specific bacteria to promote health

Question 13

define probiotics

Answer 13

live microorganisms that when administered in adequate amounts provide a health benefit to the host