KINESIOL 1Y03 Chapter Notes - Chapter 13: Chylomicron, Cecum, Homeostasis
22 Jun 2018
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Effects of the gastrointestinal microbiota on metabolism
Definitions
Gut microbiota = collective microbial community contained within the whole length of the human
gut
Gut microbiome = genes of the microbiota = total genetic capacity of the gut community
Metagenome = total DNA from the gut (aggregate of host and microbiota)
Enterotype = grouping of the microbiota of a given person
Gnotobiotic = organism with a known microbiome (either germ-free or colonised with known
bacteria)
Conventionalised = giving bacteria to germ free mice
Fermentation = energy production in anaerobic conditions
¼ of UK population are obese; gut microbiota may be responsible for the metabolic syndrome
the gut microbiome may be more dominant than our own genes
There is an increase in microbe density as you go down through the gut
Mostly comprised of anaerobes
Influences on the microbiome
1) Early development: infantile exposure e.g. to animals, prenatal exposure in the wound,
delivery type, ABx before 12 months old, urbanization
2) Adult microbiota: host genome, nutrition, lifestyle
Nutritional influence on microbiome:
- Mixed omnivorous diet = high levels of enterobacteriaceae
- Diet rich in plant polysaccharides (complex carbohydrates) = high bacteroides (e.g. Prevotella and
Xylanibacter which can degrade cellulose) and low firmiculates suggests microbiome adapts to
maximise energy derivation from diet, however this change must be long-term (-Wu, Science, 2011)
Techniques for mapping the microbiome
Difficulty arises as most microbes of the GI tract cannot be cultured technology has had to
overcome this so be can now map the microbiome without culture
Metagenomics
= Application of genomics to uncultured organisms
1) take host’s faecal matter 2) extract 16S RNA genes 3) amplify by PCR 4) clone to make libraries 5)
determine gene function
Role of the gut microbiome
Immune: immune system development, secreting antimicrobial substances e.g. lactic acid, pathogen
displacement
Metabolic: vitamin synthesis e.g. biotin and folate, metabolism of indigestible dietary polsaccharides
e.g. xylans, cellulose, starches, inulin
Microbes convert complex carbs short chain fatty acids
= butyrate: used as energy source by colonic epithelial cells
= propionate and acetate: used for gluconeogenesis and lipogenesis at the liver
Can gut microbes make you fat?
YES: germ-free mice colonised with microbes from normal mass exhibit 60% weight increase in 2
weeks –Backhed et al. 2004
Does being fat change your bacteria?
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Gut microbiota = collective microbial community contained within the whole length of the human gut. Gut microbiome = genes of the microbiota = total genetic capacity of the gut community. Metagenome = total dna from the gut (aggregate of host and microbiota) Enterotype = grouping of the microbiota of a given person. Gnotobiotic = organism with a known microbiome (either germ-free or colonised with known bacteria) Conventionalised = giving bacteria to germ free mice. Of uk population are obese; gut microbiota may be responsible for the metabolic syndrome. The gut microbiome may be more dominant than our own genes. There is an increase in microbe density as you go down through the gut. Influences on the microbiome: early development: infantile exposure e. g. to animals, prenatal exposure in the wound, delivery type, abx before 12 months old, urbanization, adult microbiota: host genome, nutrition, lifestyle. Mixed omnivorous diet = high levels of enterobacteriaceae.
