Insulin secretion and intermediary metabolism

Question 1

What are the 4 factors that lead to an increase blood glucose level?

Answer 1

Glucagon
Catecholaines
Somatotrophin
Cortisol

Question 2

What decreases blood glucose? Why is there only one? What occurs if there is a problem with this?

Answer 2

Insulin, only one as glucose is needed a lot, so too many may decrease too much, problem is diabetes type 1 and 2

Question 3

Difference between T1DM and T2DM?

Answer 3

T1 is ABSOLUTE INSULIN DEFICIENCY

T2 is ACQUIRED INSULIN RESISTANCE

Question 4

Which cells are in the Islets of Langerhans and how are they linked?

Answer 4

Alpha - Make glucagon
Beta- make insulin
Gamma - make somatostatin

Linked by TIGHT and GAP junctions, for forming intracellular spaces and allowing ions to move, respectively

Also, 98% of pancreas in EXOcrine

Question 5

What effect does Somatostatin have on Insulin and glucagon?

Answer 5

It inhibits the release of both (& somatotrophin)

Question 6

Describe the pathway for low blood glucose and hence the principal actions of glucagon

Answer 6

Glucagon release is stimulated pancreatic alpha cells receiving stimuli from:
Certain AAs and GI hormones
(Para)sympathetic activity

This leads to glucagon release, increasing hepatic glycogenolysis, gluconeogenesis and lipolysis

Question 7

How is glucose sensed in blood

Answer 7

Glucokinase is sensor

GLUT-2 transports glucose into beta cell, where glucokinase is the rate limiting step, so if [glucose] too high, it will occur, forming insulin. - build up

Question 8

How is insulin synthesised?

Answer 8

SYnthesised as PREPROinsulin, enters rER and has signal peptide cleaved
This forms PROinsulin, which is packaged at Golgi into vesicles w enzymes that cleave C-peptide, yielding insulin

Question 9

How is insulin stored and secreted?

Answer 9

Stored in beta cell, when glucose enters, it is converted to G6P which undergoes glycolysis.

This produces ATP which causes efflux of K+ through ATP channels.

This efflux leads Ca2+ to enter cell, causing insulin . vesicles to fuse w membrane and exocytose.

Question 10

What is the Glucagon-like Peptide and what does it do?

Answer 10

Gut hormone secreted in response to GUT NUTRIENTS

Stimulates insulin, inhibits glucagon

Increases satiety

Question 11

What is the insulin receptor and what does it do?

Answer 11

It binds to insulin, on the alpha unit, changing its beta unit

This allows phosphorylation of cell protein substrates by attaching.