Endocrine Pancreas and Carb Metabolism

Question 1

Active transport of glucose

Answer 1

Occurs in the intestine and kidney

- co transport via Na/glucose

Question 2

Passive transport of glucose

Answer 2

• GLUT1: fetal tissues, erythrocytes
• GLUT2: renal tubular cells, liver, beta cells
• GLUT3: neruons –> diffusion with high affinity, even at low bg concentrations
• GLUT4: insulin-regulated

Question 3

Insulin-regulated glucose transport

Answer 3

Present in:

• adipose
• muscle
• heart
• -> inserts into membrane when activated by insulin

Question 4

GLUT4 is not present in what tissues?

Answer 4

• brain

- liver

Question 5

Secretions of the endocrine pancreas

Answer 5

Interstitial fluid –> capillaries –> portal vein –> liver –> rest of the body

Question 6

Insulin structure

Answer 6

Polypeptide

- C peptide: connecting peptide, secreted with insulin and directs fold of insulin

Question 7

_____ can be used as a marker for endogenous insulin

Answer 7

C-peptide

Question 8

Insulin structure variations

Answer 8

• dogs: 1 amino acid (same as pigs!)
• cats: 4 amino acids
• horse: 2 amino acids
• cow: 3 amino acids

Question 9

Insulin is stored in ______

Answer 9

Secretory granules

Question 10

Insulin in the blood

Answer 10

Circulates mostly unbound

• half life in plasma: 6 min
• mostly cleared within 10-15 min
• degraded by insulinase in liver
• allows rapid turn on/off of insulin functions

Question 11

Insulin is ______

Answer 11

Anabolic

• decreases bg
• facilitates tissue uptake of glucose, amino acids, fatty acids, K, Mg, P

Question 12

Insulin stimulates _____

Answer 12

• glycogen synthesis
• lipogenesis
• protein synthesis and storage

Question 13

Insulin inhibits ______

Answer 13

• glycogenolysis
• lipolysis
• protein catabolism

Question 14

Insulin receptor binding

Answer 14

Results within seconds!!

• 80% of body’s cells increase glucose uptake (muscle, adipose, NOT most neurons)
• immediate phosphorylation of glucose

Question 15

Insulin helps transport glucose into the cell, ________ blood glucose

Answer 15

Decreasing

Question 16

Glucose uptake via GLUT4

Answer 16

Insulin binding –> receptor activation

- translocation of intracellular vesicles with GLUT4 to cell membrane to facilitate glucose uptake into cells

Question 17

What happens when insulin is no longer available?

Answer 17

Vesicles separate from cell membrane within 3-5 min and move back inside cell until needed again

Question 18

Insulin is a requirement for glucose transport in all cells in the body, EXCEPT

Answer 18

• neurons
• intestinal epithelium
• renal tubular epithelium
• liver
• RBC
• leukocytes
• beta cells

Question 19

Insulin binding increases cell membrane permeability to

Answer 19

• amino acids
• K
• P

Question 20

Slower insulin effect

Answer 20

10-15 minutes

• decrease or increase activity level of intracellular enzymes
• continues for hours to days

Question 21

Treatment of DKA with IV insulin

Answer 21

• decreases K in blood
• decreases P in blood
• could lead to hemolysis and death

Question 22

Muscle in the presence of insulin

Answer 22

• absorbs glucose for immediate energy

- synthesizes glycogen for use later

Question 23

Liver in the presence of insulin

Answer 23

• stimulates glycogenesis (glycogen synthesis)

- inhibits glycogenolysis (glycogen breakdown)

Question 24

In the absence of insulin (between meals)

Answer 24

• only slightly permeable to glucose

- muscle is dependent on FAs for energy

Question 25

In the presence of insulin (post-prandial)

Answer 25

- high insulin, bg concentration | - insulin increases permeability to glucose

Question 26

____ is the preferential energy source during exercise

Answer 26

Glucose

Question 27

Effects of insulin on liver carbs

Answer 27

Promotes glucose storage in the form of glycogen

Question 28

Insulin ______ glucose uptake and retention

Answer 28

Enhances - increases activity of glucokinase (hexokinase) - decreases activity of phosphatase (would release glucose)

Question 29

Insulin _____ glycogen synthesis enzymes

Answer 29

Activates - increases glycogen synthase - enzyme adds glucose to glycogen polymers

Question 30

Insulin ______ breakdown of glycogen

Answer 30

Inhibits - decreases activity of liver phosphorylase - enzyme causes hepatic glycogen breakdown to glucose

Question 31

Liver in the absence of insulin (fasting)

Answer 31

Releases glucose into the circulating blood - decreases bg = decreased pancreatic insulin secretion - effects of insulin on glucose uptake and glycogen storage is reversed

Question 32

Glycogen breakdown

Answer 32

Phosphorylase activation - splits glucose from glycogen Glucose phosphatase activated (inhibited by insulin) - allows free glucose to diffuse into blood

Question 33

Insulin is not present when ________

Answer 33

BG is low

Question 34

Glucose is the primary energy source in the _____

Answer 34

Brain - insulin has little effect on uptake/use of glucose in the brain - critical to maintain BG above a certain level

Question 35

Promotion of fat synthesis and storage by insulin

Answer 35

- carb excess = promotion of FA synthesis in hepatocytes - promotes FA transport to and storage in adipose tissue - inhibits lipolysis (lipid breakdown)

Question 36

Insulin ____ hepatic glucose uptake

Answer 36

Increases - increase in hepatic glycogen leads to inhibition of further synthesis - glucose converted into substrates for FA synthesis via insulin

Question 37

Insulin ______ lipoprotein lipase

Answer 37

Activates - splits triglycerides into FA and glycerol - allows storage of TG in adipose tissue!

Question 38

Insulin ____ hormone-sensitive lipase

Answer 38

Inhibits - enzyme causes hydrolysis of TG stored in fat cells - releases FA from adipose into blood

Question 39

Insulin deficiency effect on lipids

Answer 39

Causes lipolysis! - hormone sensitive lipase activation - hydrolysis of stored TG = release of FA and glycerol into blood --> ketone formation in liver --> conversion of some FA into phospholipids and cholesterol

Question 40

Insulin ______ protein synthesis and storage

Answer 40

Promotes - stimulates transport of amino acids into cells, increasing translation of mRNA - inhibits protein catabolism - decreases hepatic gluconeogenesis

Question 41

Hypoglycemia

Answer 41

Brain depends upon a constant blood glucose concentration for optimal function

Question 42

Hyperglycemia

Answer 42

Causes decreased osmotic pressure and cellular dehydration - loss of glucose in urine results in osmotic diuresis and dehydration - damage to blood vessels and nerves over time (humans)

Question 43

The _____ is the primary regulator of insulin release

Answer 43

Blood glucose - glucose enters beta cells via GLUT 2 (non-insulin dependent) - rate of glucose entry controls exocytosis of insulin vesicles

Question 44

High BG = ____ insulin secretion

Answer 44

Increase

Question 45

Low BG = ____ insulin secretion

Answer 45

Decrease

Question 46

Stimuli of insulin secretion

Answer 46

- increased blood amino acids - increased blood FAs - GI hormones - parasympathetic stimulation - GH, cortisol, glucagon, etc

Question 47

Inhibition of insulin release

Answer 47

- somatostatin - sympathetic activity - fasting

Question 48

Glucagon function

Answer 48

Anti-insulin/diabetogenic - rapid acting - hepatic glycogenolysis - hepatic glucogenesis (amino acid mobilization) - lipolysis

Question 49

Glucagon regulation in response to glucose

Answer 49

- decrease glucose = increased glucagon secretion | - increase glucose = decreased glucagon secretion

Question 50

Amino acids ____ glucagon secretion

Answer 50

Stimulate - same as insulin!! - for gluconeogenesis