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Met2 > Insulin: counter regulatory hormones > Flashcards

Insulin: counter regulatory hormones Flashcards

1
Q

What stimulates the secretion of glucagon?

A
  1. low glucose concentration
  2. increased blood volume
  3. exercise
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2
Q

What inhibits the secretion of glucagon?

A

insulin and somatostatin

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3
Q

How does insulin inhibit glucagon signalling?

A

insulin activates phosphodiesterase –> cAMP –> 5’AMP –> glucagon dependent signalling switched off

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4
Q

What type of receptor is the glucagon receptor?

A

GPCR

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5
Q

Explain the effect of glucagon on glycogenolysis.

A
  1. low glucose –> no insulin secretion –> no glucose transport
  2. Glycogen + triglycerides are not synthesised
  3. Processes that release glucose/fatty acids are not inhibited
  4. glucagon increases glycogenolysis
    - glycogen breakdown is stimulated via PKA and phosphorylase kinase a
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6
Q

Explain the effect of glucagon on gluconeogenesis.

A
  1. low glucose –> no insulin secretion
  2. gluconeogenesis is not inhibited
  3. lipolysis is not inhibited
  4. glucagon increases gluconeogenesis and inhibits glycolysis
    - increased amino acid uptake
    - inhibition of PFK-1 (mediated by cAMP/PKA)
    - inhibition of pyruvate kinase (mediated by cAMP/PKA)
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7
Q

Explain the effect of glucagon on lipolysis.

A

triglycerides –> free fatty acids and glycerol

  1. hormone sensitive lipase is inhibited by insulin/activated by glucagon
  2. malonyl-CoA inhibits transport of FFAs into mitochondria via CPT-I –> inhibits beta-oxidation
    * glucagon stimulates CPT-I
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8
Q

State the effect of insulin/glucagon on ketogenesis.

A 
Insulin = inhibits
Glucagon = activates
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9
Q

What are catecholamines and when are they released?

A
  • Monoamines synthesised from phenylalanine and tyrosine

- released in response to stress/hypoglycaemia

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10
Q

What stimulates/inhibits epinephrine? What are the effects of epinephrine being released?

A

Inhibits: insulin
Stimulates: glycogenolysis (liver + muscle) and glucagon
- increases lipolysis in adipose tissue
- end result: increased blood sugars and fatty acid levels

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11
Q

What is secreted by cortex cells of the adrenal gland and what stimulates this?

A
  • secretes glucocorticoids and other steroids

- stimulated by ACTH (pituitary)

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12
Q

What stimulates/inhibits cortisol? What are the effects of cortisol being released?

A

Inhibits: glucose uptake and utilisation
Stimulates: muscle proteolysis and adipose tissue lipolysis
- enhances gluconeogenesis
- end result: rapid mobilisation of amino acids and fatty acids from cellular stores

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13
Q

What can occur if cortisol is elevated for too long?

A

proteolysis and muscle wasting

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14
Q

What is the effect of growth hormone on adipose tissue?

A
  • increased lipolysis
  • reduced glucose uptake
  • reduced lipogenesis
  • reduced re-esterification of FFAs
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15
Q

What is the effect of growth hormone on skeletal muscle?

A
  • reduced glucose uptake
  • increased LPL activity
    = increased beta-oxidation
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16
Q

What is the effect of growth hormone on liver?

A
  • stimulates IGF-1 production
  • increases VLDL secretion
  • increased HPL activity
  • reduced PPAR alpha expression
    = increased production + uptake of IDL, LDL, HDL
17
Q

What are the thyroid hormones T4 and T3 called?

A 
T4 = thyroxine
T3 = triiodothyronine
18
Q

What are the roles of the thyroid hormones?

A
  • increase number and activity of mitochondria = increase rate of ATP synthesis
  • increase insulin secretion
  • increase fat metabolism
  • increase BMR
  • enhances glycolysis and gluconeogenesis
  • increased glucose uptake
19
Q

Give examples of incretins.

A

glucagon-like peptide 1

gastric inhibitory peptide

20
Q

What is the effect of GLP-1 on glucagon secretion and hepatic glucose production?

A

glucagon secretion: inhibited
hepatic glucose production: inhibited

*augments glucose-induced insulin secretion

21
Q

What is hypoglycaemia?

A

plasma glucose level: <70 mg/dL (<3.9 mmol/L)

22
Q

What causes hypoglycaemia?

A
  • reactive hypoglycaemia (excessive insulin secretion in response to high carb meal –> hyperdiabetic condition)
  • excessive exercise (increase glucose utilisation)
  • insulinoma (tumour of pancreatic beta cell)
  • alcohol excess (inhibition of gluconeogenesis)
  • high insulin doses
23
Q

What are the S+S of hypoglycaemia?

A
  1. Autonomic:
    - trembling
    - palpitation
    - sweating
    - anxiety
    - hunger
    - tingling
  2. Neuroglycopaenic:
    - difficulty concentrating/speaking
    - confusion
    - weakness
    - drowsiness/tiredness
    - vision changes
    - dizziness
  3. other neuro symptoms:
    - disorientation
    - convulsion/fitting/seizures
    - loss of consciousness
    - coma
24
Q

What are the effects of hypoglycaemia?

A
  • GH and cortisol secreted –> reduced glucose utilisation cells convert to FAT utilisation
  • storage of glucose for the brain
  • -> prolonged and repeated hypoglycaemia = permanent brain damage

Met2 (26 decks)

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