Flashcards in B2.047 Hormonal Regulation of Glucose Homeostasis Deck (41)
what are the 5 type of pancreatic cells and what do they secrete?
F- pancreatic polypeptide
describe the steps of glucose mediated insulin secretion in the beta cells
passive glucose transport into cell via GLUT2
glucose metabolism in mitochondria
ATP mediated inhibition of K+ channel
activation of voltage gated ca2+ channel
Ca2+ influx stimulates vesical mediated secretion
what mediators in addition to glucose can activate the voltage gates Ca2+ channel?
anything that increases ATP
at approx. what blood glucose levels does insulin secretion begin and level off?
begin 100 mg/ 100 mL
level 500 mg/ 100 mL
how can plasma free fatty acids both stimulate and suppress B cell function?
stimulate- can increase ATP via fatty acid metabolism
suppress- very high levels like in obesity can inhibit B cell sensitivity
what are the 2 primary inhibitors of beta cell function?
sympathetic stimulation (epinephrine, norepinephrine)
delta cell (somatostatin)
what type of state does insulin promote?
anabolic- stores fuels
how does insulin impact liver glucose release?
inhibits it by phosphorylating glucose
how doe insulin impact amino acids?
stimulates active transport into cells
stimulates protein synthesis
decreases protein breakdown
how does insulin impact fatty acids?
increases uptake by adipose
inhibits hormone sensitive lipase
what are the primary sites of insulin action?
liver, muscle, adipocytes
how is GLUT1 regulated
increased by growth factors, hypoglycemia, and PPAR gamma (TZDs)
decreased by hyperglycemia
where is GLUT2 expressed?
pancreatic B cells, liver, intestine, kidney
what two mechanisms mobilize GLUT4 in muscle and adipocytes?
what can suppress GLUT4 mobilization?
what is the main target and primary regulator of glucagon?
what are the two primary inhibitors of glucagon?
what state does glucagon promote?
catabolic- fuel breakdown
how are liver proteins impacted by glucagon?
stimulates hepatic proteolysis
stimulates liver AA uptake
stimulated hepatic ureagenesis (ammonia disposal)
how are TG breakdown proteins used?
FA- liver converts to ketones (CNS, muscle, heart)
glycerol- liver uses for gluconeogenesis
what stimulated somatostatin secretion?
glucose and AA
what is the function of somatostatin?
slow gastric emptying
fine tune nutrient absorption and utilization
what levels of I:G ratio are associated with each metabolic status?
O/N fast: 2
prolonged fast: 0.5
what hormones in addition to glucagon and insulin and important in glucose homeostasis? where do they come from?
growth hormone: anterior pituitary
cortisol: adrenal cortex
epinephrine: adrenal medulla
thyroid hormone: thyroid gland
how are catecholamines regulated by hypoglycemia?
hypoglycemia induces sympathetic neuronal activity in the adrenal medulla
how are growth hormone and cortisol regulated by hypoglycemia?
hypoglycemia induces a CNS response in the hypothalamus ultimately leading to increased hormone secretion
how does growth hormone regulate tissues in glucose homeostasis?
adipose: stimulates lipolysis
liver: stimulates gluconeogenesis
decreases glucose uptake by tissues by increasing FFA and inducing insulin resistance
how do glucocorticoids regulate homeostasis?
alter gene expression
slow acting, more "chronic" regulators than other hormones
what 4 functions do glucocorticoids help regulate?