9/14/22 Flashcards
in cholera treatment,
glucose stimulates SGLT1
role of nutrients in gut
nutrients tell gut there is stuff in there, gut sends the right signals
carbohydrate absorbable form
monosaccharides: glucose, fructose, etc.
fats absorbable form
fatty acids, glycerol
proteins absorbable form
amino acids
minerals absorbable form
elemental minerals
vitamins absorbable form
free vitamins
macronutrients
carbs, fats, proteins
micronutrients
minerals and vitamins
why do we degrade foods so much?
- avoid immune response (food form is so big, body would freak out)
- control of nutrient metabolism
food processing advantages
- loss of food matrix
a) higher digestibility: high caloric and nutritional values
b) nutrients are more quickly absorbed: deprive colon bacteria of nutrients - preservation: higher shelf life
- sterlizaition: lower cost for immune system
food processing disadvantages
- excessive nutrient and caloric density (obesity)
- cooking: some loss of nutrients (heat inactivation, dripping, dilution), formaiton of potentially harmful agents: Maillard compounds, etc.
benefits of fermented drinks/foods
sterile!
easier to digest
compared to other primates, humans have
- smaller mouths and teeth
- weaker jaw muscles
- smaller guts, which saves humans at least 10% of daily energy expenditure
- bigger brains, likely as the result of switching energy expenditure in the gut to the brain
Stages of the digestion process
- Movement: of food through the alimentary tract
- Secretion: of digestive juices and digestion of the food
- Absorption: of water, various electrolytes, and digestive products
- Circulation: of blood and lymph through the gastrointestinal organs to carry away the absorbed substances
- Control: of all these functions by local, nervous, and hormonal systems
main function of digestive tract
provide body with continual supply of water, electrolytes, and nutrients AND excrete metabolic waste
how does digestive tract achieve its main function?
- Ingestion: incorporation of food into digestive tract
- Digestion: breakdown of food into absorbale nutrients
- Absorption: incorporation of nutrients into the body
- Elimination: removal of non-digested food and waste
taste vs. flavor
taste: we all have the same 5 tastes
flavor: chocolate, strawberry, perceived differently
function of sweet
permits identification of energy-rich nutrients
function of umami
recognition of amino acids (protein)
function of salty
ensures proper dietary electrolyte balance
function of sour AND bitter
warn against intake of potentially noxious and/or poisonous chemicals
taste triggers a…
response, body prepares to receive nutrients
Taste bud: Type I cells
~50% of cells in a taste bud
glia-like functions: structural and nutritional support
no taste receptors
Taste bud: Type II cells
~30% of taste bud cells
contains bitter, sweet, and umami receptors (primary tastes)
most cells have only one receptor type T1R or T2R
Taste bud: Type III cells
2-20% of taste bud cells
contain sour taste receptors
have synaptic structures
role of glutamate in taste
glutamate terminates taste signal to prep for another round
taste-receptor cells (TRCs) are what type of cell
stratified epithelia
spice
activates TRPV1 (heat-sensitive) ion channel by capsaicin and other stimulants
not in taste receptor complex
follows pain pathway to brain
Taste GPCRs
T1Rs
T2Rs
same signaling family
Taste Ion Channels
ENaC
Taste transporters
nutrient sensors
GLUT4
SGLT1
T1Rs
sweet and umami taste receptors
T2Rs
bitter taste receptors
ENaC
epithelial Na+ channel
salty?
GLUT4 and SGLT1
glucose sensors
nutrient sensors
essential events for transduction of primary taste stimuli (sweet, bitter, umami)
- activation of gustducin, phospholipase C-beta2, and TRPM5 channels
- calcium release
signal transduction cascade: taste receptors
- tastant binds to receptor
- stimulates gastducin
- activates PL C-beta2
- send IP3
- release Ca2+
OTOP1
sour receptor
proton channel
senses acidity
OTOP1 pathway
- protons from acid go across OTOP1
- close K+ channel
- K+ accumulates
- local depolarization
- leads to greater depolarization
- opens Na+ channels
- releases Ca2+
OTOP1 pathway official
- OTOP1 conducts H+ ions (protons) into cell cytosol
- Lower intracellular pH blocks KIR2.1 K+ channels which further depolarize membrane potential
- in response to depolarization, voltage-gated Na+ channels open, cause action potential
- action potentials open voltage-gated Ca2+ channels evoking NT release
eNaC pathway
- Na+ ions in oral cavity enter taste receptor cells through eNaC channels (pretty much everywhere)
- membrane depolarization followed by action potentials
- CALHM1/3 channels open in response to AP and release ATP onto afferent nerve fibers (ATP as a signaling molecule)
- salty cells are identified by co-expression of CALHM1/3 and eNaC-alpha
what proteins signal fat taste
CD36 and GPR120
taste receptors control…
metabolism!
they are involved in secretion of hormones in pancreas and gut
obligatory step in stimulation of gut hormone secretion
nutrient absorption!
rate of gut hormone secretion is determined by…
rate of monosaccharides and lipids absorption
gut hormones also control…
blood nutrient levels by modulating digestion and absorption
GLP1
glucagon-like peptide 1
CCK
cholecystokinin
GIP
gastric inhibitory polypeptide
PYY
peptide YY
glucose absorption triggers…
secretion of incretins GIP and GLP1 in proximal small-intestinal cells
lipid absorption in small intestine modulates release of…
GIP and CCK
microbial products of metabolism (short-chain FAs, indole, lipopolysaccharide, seocndary bile acids) modify…
intestinal secretion of GLP-1, GLP-2, and PYY
primary bile acids
needed for lipases
1. colic acid
2. deoxycolic acid
the two acids convert to signals
SGLT1 role
incorporates glucose into enterocyte, then into circulation
enteroendocrine cells produce…
gut hormones that coordinate food digestion and absorption, insulin secretion, and appetite
GLP, CCK, and GIP modulate
human metabolism through anorexigenic and/or insulinotropic actions
bariatric surgery increases…
postprandial concentrations of GLP-1 and PYY, which cause post-surgical weight loss and resolution of type 2 diabetes in humans (increase insulin regulation)
basis for new therapeutics for type 2 diabetes and obesity
gut hormones!
EX: GLP-1
anorexigenic peptides
say hey! we have enough food
suppress appetite
acid
high conc H+
activators of gastric acid release
Hist, gast, ACh
inhibitors of gastric acid release
SST
when does digestion begin?
before we even consume food
as soon as we see/smell/think about it
