B2.047 Hormonal Regulation of Glucose Homeostasis

Question 1

what are the 5 type of pancreatic cells and what do they secrete?

Answer 1

beta- insulin
alpha- glucagon
delta- somatostatin
F- pancreatic polypeptide
epsilon- ghrelin

Question 2

describe the steps of glucose mediated insulin secretion in the beta cells

Answer 2

passive glucose transport into cell via GLUT2
glucose metabolism in mitochondria
ATP mediated inhibition of K+ channel
cell depolarization
activation of voltage gated ca2+ channel
Ca2+ influx stimulates vesical mediated secretion

Question 3

what mediators in addition to glucose can activate the voltage gates Ca2+ channel?

Answer 3

glucagon
GLP1
anything that increases ATP

Question 4

at approx. what blood glucose levels does insulin secretion begin and level off?

Answer 4

begin 100 mg/ 100 mL

level 500 mg/ 100 mL

Question 5

how can plasma free fatty acids both stimulate and suppress B cell function?

Answer 5

stimulate- can increase ATP via fatty acid metabolism

suppress- very high levels like in obesity can inhibit B cell sensitivity

Question 6

what are the 2 primary inhibitors of beta cell function?

Answer 6

sympathetic stimulation (epinephrine, norepinephrine)
delta cell (somatostatin)

Question 7

what type of state does insulin promote?

Answer 7

anabolic- stores fuels

Question 8

how does insulin impact liver glucose release?

Answer 8

inhibits it by phosphorylating glucose

Question 9

how doe insulin impact amino acids?

Answer 9

stimulates active transport into cells
stimulates protein synthesis
decreases protein breakdown

Question 10

how does insulin impact fatty acids?

Answer 10

increases uptake by adipose

inhibits hormone sensitive lipase

Question 11

what are the primary sites of insulin action?

Answer 11

liver, muscle, adipocytes

Question 12

how is GLUT1 regulated

Answer 12

increased by growth factors, hypoglycemia, and PPAR gamma (TZDs)
decreased by hyperglycemia

Question 13

where is GLUT2 expressed?

Answer 13

pancreatic B cells, liver, intestine, kidney

Question 14

what two mechanisms mobilize GLUT4 in muscle and adipocytes?

Answer 14

insulin

exercise

Question 15

what can suppress GLUT4 mobilization?

Answer 15

FFAs

Question 16

what is the main target and primary regulator of glucagon?

Answer 16

the liver

glucose regulated

Question 17

what are the two primary inhibitors of glucagon?

Answer 17

insulin

somatostatin

Question 18

what state does glucagon promote?

Answer 18

catabolic- fuel breakdown

Question 19

how are liver proteins impacted by glucagon?

Answer 19

stimulates hepatic proteolysis
stimulates liver AA uptake
stimulated hepatic ureagenesis (ammonia disposal)

Question 20

how are TG breakdown proteins used?

Answer 20

FA- liver converts to ketones (CNS, muscle, heart)

glycerol- liver uses for gluconeogenesis

Question 21

what stimulated somatostatin secretion?

Answer 21

glucose and AA

Question 22

what is the function of somatostatin?

Answer 22

slow gastric emptying

fine tune nutrient absorption and utilization

Question 23

what levels of I:G ratio are associated with each metabolic status?

Answer 23

fed: 30
O/N fast: 2
prolonged fast: 0.5
DM: imbalance

Question 24

what hormones in addition to glucagon and insulin and important in glucose homeostasis? where do they come from?

Answer 24

growth hormone: anterior pituitary
cortisol: adrenal cortex
epinephrine: adrenal medulla
thyroid hormone: thyroid gland

Question 25

how are catecholamines regulated by hypoglycemia?

Answer 25

hypoglycemia induces sympathetic neuronal activity in the adrenal medulla

Question 26

how are growth hormone and cortisol regulated by hypoglycemia?

Answer 26

hypoglycemia induces a CNS response in the hypothalamus ultimately leading to increased hormone secretion

Question 27

how does growth hormone regulate tissues in glucose homeostasis?

Answer 27

adipose: stimulates lipolysis
liver: stimulates gluconeogenesis
decreases glucose uptake by tissues by increasing FFA and inducing insulin resistance

Question 28

how do glucocorticoids regulate homeostasis?

Answer 28

alter gene expression

slow acting, more “chronic” regulators than other hormones

Question 29

what 4 functions do glucocorticoids help regulate?

Answer 29

metabolism
inflammation
circulation
development

Question 30

what metabolic enzymes are regulated in part by glucocorticoids?

Answer 30

PEPCK
gluc-6-phosphatase
lipolytic agents

Question 31

describe the differences in half life between catecholamines and glucocorticoids

Answer 31

catecholamines: seconds
cortisol: hours

Question 32

how do catecholamines (epinephrine) regulate various systems during glucose homeostasis?

Answer 32

pancreas: decreases insulin, increases glucagon
liver: stimulates glycogenolysis and gluconeogenesis
skeletal muscle: stimulates glycogenolysis
adipose tissue: induces hormone sensitive lipase

Question 33

what is the acute stress response promoted by epinephrine?

Answer 33

increased blood glucose, FFA, and glycerol

Question 34

what hormone regulates basal metabolic rate?

Answer 34

thyroid hormone

Question 35

what are the primary functions of thyroid hormone?

Answer 35

regulates cell sensitivity to insulin and epinephrine

regulates BMR and fuel consumption by increasing expression of NA-K ATPase

Question 36

absorptive phase

Answer 36

increased insulin
[increased glucagon]
[increased GH]
basal cortisol

Question 37

post-absorptive phase

Answer 37

basal insulin
low glucagon
low GH
basal cortisol

Question 38

short term fast (3-5 days)

Answer 38

low insulin
increased glucagon
increased GH
basal cortisol

Question 39

prolonged fast

Answer 39

low insulin
increased glucagon
increased cortisol
increased catecholamines (stress response)

Question 40

what are symptoms of glucocorticoid deficiency?

Answer 40

insulin sensitivity
hypoglycemia
increased ACTH and pigmentation
hyperkalemia/hyponatremia
hypovolemia

Question 41

what happens if you have excess glucocorticoids?

Answer 41

locked in a catabolic state

redistribution of fat w obesity (trunk)