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Metabolism > Postprandial Glucose Metabolism - Pancreatic Function > Flashcards

Postprandial Glucose Metabolism - Pancreatic Function Flashcards

1
Q

How many cells are in each islet of langerhans?

A

50-300

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2
Q

What are the four types of cells in the islets of langerhans?

A

alpha, beta, delta and theta

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3
Q

What hormone do beta cells secrete?

A

insulin and amylin

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4
Q

What hormone do alpha cells secrete?

A

glucagon

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5
Q

What hormone do delta cells secrete?

A

somatostatin

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6
Q

What hormone do theta cells secrete?

A

pancreatic polypeptide

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7
Q

Which hormones cleave insulin?

A

prohormone convertase 1 and 2

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8
Q

Which part of the proinsulin molecule is cleaved to make insulin?

A

the c peptide

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9
Q

How are the two peptides of insulin connected?

A

disulphide bonds

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10
Q

Where is preproinsulin converted to proinsulin?

A

in the microvesicles after the rough endoplasmic reticulum

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11
Q

Where is proinsulin converted to insulin?

A

in the vesicles after the golgi apparatus

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12
Q

What are the two phases of insulin secretion?

A

1st phase is a sharp rise in insulin that lasts for 2-5 minutes and the 2nd phase is a prolonged secretion that lasts for the duration of the stimulus

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13
Q

Describe the cellular events in glucose induced insulin secretion

A

glucose enters the cell via GLUT-2 transporter, glucose is converted to G-6-P by glucokinase, glucose goes through glycolysis and the krebs cycle to produce ATP, the increase in ATP closes the potassium channel which depolarises the membrane which opens the voltage gated calcium channel, the entry of calcium into the cell allows the release of insulin from vesicles

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14
Q

What is the Km of GLUT-2 and glucokinase?

A

high Km so that the process is not easily saturated

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15
Q

What other nutrients can induce insulin secretion other than glucose?

A

amino acids and fatty acids

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16
Q

How do amino acids induce insulin secretion?

A

by increasing ATP in the cell in the same way that glucose does

17
Q

How do fatty acids induce insulin secretion?

A

the fatty acids have to be converted to malonyl CoA

18
Q

Why is more insulin secreted when glucose is ingested orally rather than intravenously?

A

because incretins (gut derived hormones) which are produced in response to nutrients in the gut also stimulate insulin secretion

19
Q

What are the two main incretins and where are they secreted?

A

GIP from the K cells in the upper small bowel and GLP-1 from L cells in the lower small bowel

20
Q

What are the actions of GLP-1?

A

inhibits glucagon secretion, stimulates insulin synthesis, promotes beta cell proliferation, promotes beta cell differentiation, stimulates beta cell maturation, inhibits gastric emptying

21
Q

Why dont incretin based therapies cause hypoglycaemia?

A

because incretins dont release insulin if blood glucose isnt high

22
Q

What incretin based therapies are available for diabetes treatment?

A

DPP-4 inhibitors which inhibit the enzyme which destroys GLP-1 and GLP-1R agonists

23
Q

What are liraglutide and exenatide?

A

GLP-1R agonists

24
Q

What is bydureon?

A

a long acting GLP-1R agonist

25
Q

What are the actions of GIP?

A

stimulates insulin secretion and lipoprotein lipase to enhance fat clearance

26
Q

What are the actions of amylin?

A

inhibits glucagon secretion, delays gastric emptying, inhibits food intake

27
Q

What is pramlintide?

A

an amylin analogue used in the treatment of diabetes

28
Q

What are the actions of glucagon?

A

stimulates liver to release glucose

29
Q

What are the actions of pancreatic polypeptide?

A

inhibits food intake, increases energy expenditure, inhibits secretion of enzymes from the pancreas, blocks contraction of the gall bladder

30
Q

What are the actions of somatostatin?

A

inhibits insulin and glucagon secretion, inhibits pancreatic exocrine function - prevents exaggerated responses to a meal

Metabolism (16 decks)

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