glucose lect 20

Question 1

what are the primary hormones that regulate plasma glucose

Answer 1

insulin and glucagon

Question 2

insulin and glucagon secretion is determined primarily by

Answer 2

plasma substrate levels

Question 3

differentiate between insulin and glucagon in terms of overall function

Answer 3

• insulin: stores excess glucose as fuel when it is in excess
  
  • fed state
• glucagon: promotes the mobilization of glucose when glucose levels are low
  
  • fasting state

Question 4

insulin and glucagon are released from what organ? What cells specifically

Answer 4

pancreas

• alpha cells: glucagon
• beta cells: insulin

Question 5

what is the islets of langerhans? what cell populations does it have

Answer 5

• clusters of endocrine cells
• cell population
  
  • B cells: insulin
  • a-cells: glucagon
  • delta-cells: somatostatin

Question 6

precleaved insulin consists of what 3 chains

Answer 6

• A chain
• B chain
• c-peptide

Question 7

list stages of insulin maturation

Answer 7

1. preproinsulin
2. proinsulin
   
   • packaged into granules
3. in granule, proinsulin is cleaved to insulin + C-peptide

Question 8

release of insulin is tied to ATP production from

Answer 8

glucose

• glucose is the most important stimulator of insulin secretion

Question 9

define the incretin effect

Answer 9

the increased stimulation of insulin secretion elicited by oral as compared with intravenous administration of glucose under similar plasma glucose levels

Question 10

what are Incretins

Answer 10

• group of metabolic hormones that stimulate a decrease in blood glucose levels.
  
  • cause an increase in the amount of insulin released from pancreatic beta cells of the islets of Langerhans after eating, before blood glucose levels become elevated

Question 11

list the two incretins

Answer 11

• glucagon-like peptide-1 (GLP-1)
• gastric inhibitory peptide (GIP)

Question 12

function of cholecystokinin

Answer 12

peptide hormone of the gastrointestinal systemresponsible for stimulating the digestion of fat and protein.

Question 13

if the glucose challenge is given intravenously, then the plasma glucose compared to oral glucose load

Answer 13

plasma glucose rises much more rapidly than with oral glucose

Question 14

insulin acts on what type of cell receptor

Answer 14

tyrosine kinase

• insulin binds to alpha subunit
• b subunits are tyrosine kinase

Question 15

what is IGF-1? what is important about it

Answer 15

• Insulin-like growth factor 1
• high concentrations of insulin can stimulate the IGF-1 receptor and
• high levels of IGF-1 can stimulate the insulin receptor

Question 16

describe the process from insulin binding to glucose entering the cell

Answer 16

1. kinase activated when insulin binds to a subunit
2. autophosphorylates B subunits at the tyrosines and insulin receptor substrates (IRS)
3. results in Glut 4 translocation to the cell membrane (in skeletal muscle and adipose tissue)

Question 17

list the multiple effects of insulin

Answer 17

1. increase glucose storage
2. increase protein synthesis and decrease proteolysis
3. increase growth
4. increase triglyceride synthesis and decrease lipolysis

• **tissue uptake of glucose and amino acids is stimulated by insulin and tissue release of glucose, amino acids, and free fatty acids is inhibited by insulin

Question 18

list insulin effect on liver for carbohydrates

Answer 18

1. increase sotrage of glucose
2. increase glycogen synthesis
3. decrease gluconeogenesis
4. promotes conversion of glucose to fat

Question 19

list insulin effect on liver for lipids

Answer 19

1. promotes the synthesis and storage of fat and inhibits fat oxidation
2. releases fats which are then stored or used for fuel by adipose tissue and skeletal muscle

Question 20

list insulin effect on liver for protein

Answer 20

1. increase protein synthesis
2. decrease protein degradation

Question 21

list insulin effect on skeletal muscle

Answer 21

1. increase protein synthesis and decrease protein degradation
2. increased glucose uptake (GLUT4)
3. increase glycogen synthesis
4. increase glucose breakdown and oxidation which promotes formation of triglycerides

Question 22

where is the principle site of glucose disposal

Answer 22

skeletal muscle

Question 23

list insulin effect on adipose tissue

Answer 23

1. increase glucose uptake (GLUT4)
2. promotes the flow of glucose to fatty acids
3. promotes the formation of triglycerides