Energy Homeostasis - The endocrine pancreas Flashcards

1
Q

Pancreatic islet contains

A
  • alpha cells - glucagon
  • beta cells - insulin
  • delta cells - somatostatin
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2
Q

glucagon increases what

A

blood glucose

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3
Q

insulin decreases what

A

blood glucose

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4
Q

in insulin, they have alpha and beta chains connected by ?

A

disulfide bonds

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5
Q

insulin is degraded by ?

A

insulinase

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6
Q

what is released alongside insulin and can be used to determine how much endogenous insulin is secreted

A

C-peptide

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7
Q

what is the pathway for insulin secretion

A

low glucose -> increased ADP:ATP ration -> open K+ channels -> hyperpolarization -> depolarization -> VGC opening -> Exocytosis of insulin

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8
Q

what happens when insulin binds to its receptor

A

insulin binds to its receptor -> dimerization -> activating protein tyrosine kinase activity

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9
Q

what are the key pathways from insulin receptor activation

A
  • PI3K pathway -> Akt and mTOR activation
  • IRS activates Ras -> Raf activation -> MEK & MAPK activation -> protein synthesis
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10
Q

cells that are chronically exposed to high levels of insulin:

A
  • reduce the number of insulin receptors expressed
  • down-regulate some signaling pathways distal to receptor activation
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11
Q

what are the stimulators of insulin secretion

A
  • Nutrients in the bloodstream
    ○ Glucose (major)
    ○ Amino acids (arg, lys)
    ○ Free fatty acids
  • Hormonal signals
    ○ CCK, GIP (gastric inhibitory polypeptide), and GLP-1 (glucagon-like peptide) are released from the small intestine in response to food – these are known as incretins
    ○ parasympathetic innervation – mostly from the cephalic phase of digestion
    ○ GH – needed for normal insulin secretion
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12
Q

what are the inhibitors for insulin secretion

A
  • Hormones
    ○ Somatostatin
    ○ Epinephrine
    ○ Leptin
  • Sympathetic nervous system
    ○ Both epinephrine and norepinephrine can inhibit insulin secretion – mediated by alpha receptors
    ○ Stimulation of beta-receptors can stimulate some insulin secretion – however, activation of the SNS results in net inhibition of insulin secretion
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13
Q

what are the insulin-independent glucose transporters?

A

○ SGLT-1 and SGLT-2: intestine and kidney
○ GLUT-1 and GLUT-3: wide distribution
- GLUT-2: liver and pancreas

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14
Q

what is the major insulin dependent glucose transporter?

A

GLUT-4

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15
Q

what are the insulin to liver effects?

A
  1. increased glucose uptake from bloodstream
  2. increased glucose use
  3. increased fatty acid synthesis and VLDL formation
  4. decreased ketogenesis
  5. increased protein synthesis and decreased urea cycle activity
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16
Q

proglucagon includes?

A

amino acid sequence that can yield glucagon-related polypeptide (GRPP), glucagon, IP-1, GLP-1, IP-2, and GLP-2

17
Q

what cleaves proglucagon at points that yield GRPP, glucagon, and a C-terminal fragment

A

proteases

18
Q

what stimulates glucagon synthesis

A
  • drops in blood glucose
  • rise in serum amino acids
  • cortisol
  • sympathetic nervous system stimulation
  • exercise, stress
19
Q

what inhibits glucagon synthesis

A
  • rise in blood glucose
  • stomatostatin
20
Q

what are the glucagon to liver effects

A
  1. increased glucose “output” to other tissues
  2. increased beta oxidation
  3. increased ketogenesis
  4. increased urea cycle activity
21
Q

when there is a high ration of insulin/glucagon

A

anabolic state

22
Q

when there is a low ration of insulin/glucagon

A

catabolic state

23
Q

somatostatin tends to ?

A

decrease the secretion of both insulin and glucagon