Insulin and Glucagon

Question 1

how long would plasma glucose last? glycogen? fat?

Answer 1

1 hour
part of one day
40 days with water

Question 2

how much protein is in the body and how much of it could be use for energy needs?

Answer 2

10-12 kg

1/2 is available

Question 3

what is the normal blood concentration of glucose?

Answer 3

80-100 gm/dL

Question 4

what is the role of somatostatin in the pancreas?

Answer 4

prevents release of insulin and glucagon

Question 5

what is the brain energy source? how much oxygen does it require?

Answer 5

glucose

20% of resting oxygen supply

Question 6

what are the three types of islets of langerhans cells and what do they secrete?

Answer 6

alpha- glucagon
beta- insulin
delta- somatostatin

Question 7

where is pancreatic polypeptide secreted? what does it do?

Answer 7

GI hormone synthesized by F cells at the periphery of the islet (with alpha and delta cells)
inhibits gallbladder contraction and pancreatic exocrine secretion

Question 8

when is pancreatic polypeptide secreted?

Answer 8

during strenuous exercise, after ingestion of a protein rich meal or during hypoglycemia

Question 9

how is glucagon synthesized?

Answer 9

it is translated as pre-proglucagon and processed postranslationally into glucagon, glicentin, GLP-1 and 2 and glicentin- like peptide
stored in membrane bound granules

Question 10

what happens to glucagon after it is released?

Answer 10

it is degraded by the liver and kidney (not excreted)

Question 11

what are stimulators of glucagon secretion?

Answer 11

hypoglycemia <50mg/dl
increase in arginine and alanine (protein degredation)
exercise and stress

Question 12

what are three inhibitors of glucagon secretion?

Answer 12

insulin, somatostatin and hyperglycemia

Question 13

what are the counter regulatory hormones? what do they do?

Answer 13

glucagon, catecholamines, growth hormone and cortisol

keep blood glucose high enough for brain

Question 14

what is the primary target of glucagon? what does it do?

Answer 14

liver

increases blood glucose- glycogenolysis, gluconeogenesis, and lypolysis

Question 15

what does glucagon do in adipose tissue?

Answer 15

decreases glycolysis and promotes release of fatty acids

Question 16

how is insulin synthesized?

Answer 16

synthesized in perproinsulin form

processed in storage granules with endopeptidase (secreted together)- cleaved into insulin and C peptide

Question 17

why is zinc included in secretory granules?

Answer 17

to join 6 insulin molecules into hexamers

Question 18

what are levels of C peptide used for?

Answer 18

to quantitate endogenous insulin production when patients receive insulin injections

Question 19

what type of insulin is used to inject to diabetic patients?

Answer 19

crystalline zinc insulin

Question 20

how is insulin degraded?

Answer 20

insulinases in liver, kidney and other tissues

Question 21

describe postprandial insulin secretion.

Answer 21

there is an early phase of insulin release after 10 min and a peak at 30-45 min (late phase)

Question 22

describe release of insulin with IV glucose.

Answer 22

early phase (release of stored insulin) which falls in 10 min
late phase if stimulus is maintained- reflects newly formed

Question 23

what is the mechanism of insulin secretion from beta cells?

Answer 23

1 GLUT 2 transporter mediates diffusion of glucose in
2 increase in ATP due to glucose metabolism
3 ATP inhibits a K channel-cell voltage increase
4 depolarization activates Ca channel and Ca induced Ca release
5 elevated Ca leads to fusion of vesicles- insulin release

Question 24

besides glucose, what else can modulate insulin secretion?

Answer 24

amino acids, other monosaccharides, and certain hormones

Question 25

describe the phases of digestion with respect to insulin.

Answer 25

cephalic phase- vagus mediates small rise in insulin | intestinal phase- glucose absorption stimulates secretion

Question 26

what do incretins do?

Answer 26

provide advance notice of feeding and stimulate insulin secretion CCK, GIP and GLP-1 increase insulin during feeding

Question 27

describe the effects of epinephrine and NE on beta cells.

Answer 27

epinephrine- stimulates secretion (beta receptor) | NE- supresses insulin (alpha receptor)- from postsynaptic nerve terminals

Question 28

what is the net effect of sympathetic action on beta cells?

Answer 28

there is a net supression of insulin secretion

Question 29

what is insulin's effect on the liver?

Answer 29

stimulates glucose uptake, glycogenesis, lipogenesis, glycolysis and protein synthesis

Question 30

what is insulin's effect on myocytes?

Answer 30

stimulates glucose uptake with increase GLUT 4 on surface, promotes glycogenesis and glycolysis also stimulates lipogenesis and protein synthesis (AA uptake also)

Question 31

what is insulin's effect on adipocytes?

Answer 31

increase in GLUT 4 and LPL export to capillaries. also increases glycolysis and esterification of fats

Question 32

what is the difference in results of a glucose tolerance test with diabetes?

Answer 32

plasma glucose will rise higher and remain there longer

Question 33

what disease causes insulin deficiency? insulinemia? glucagon deficiency?

Answer 33

type 1 diabetes insulin shots and insulinoma glucagon deficiency very rare

Question 34

what are orixigenic factors? give an example

Answer 34

neurotransmitters that stimulate feeding | neuropeptide Y

Question 35

what are anorexigenic factors? give 4 examples

Answer 35

neurotransmitters that inhibit feeding | GLP-1, corticotropin releasing hormone, alpha MSH and CART

Question 36

what do satiation sinals do?

Answer 36

secreted in response to food ingestion, act within timeframe of single meal and reduce meal size

Question 37

where is the primary control of food intake?

Answer 37

hypothalamus

Question 38

which GI peptides reduce meal size?

Answer 38

CCK, GLP-1, GLP-2, glucagon, and PYY

Question 39

what pathway carries information that fat and protein has been eaten?

Answer 39

nucleus of the solitary tract

Question 40

where is ghrelin secreted and what does it do?

Answer 40

secreted from oxyntic glands of stomach | stimulates food intake by acting on arguate nucleus to increase NPY and inhibit CART

Question 41

what hormones are secreted in proportion to the amount of fat in the body?

Answer 41

leptin and insulin- enter hypothalamus to influence energy homeostasis

Question 42

what contributes to meal onset signals and what do they activate?

Answer 42

environmental factors, low leptin, hypoglycemia, hypoinsulinemia and negative energy balance activate orexin and MCH expression

Question 43

what strategies need to be devised for long term weight loss success?

Answer 43

counteracting hormonal changes to weight loss that stimulate appetite