The Endocrine Pancreas

Question 1

Different islet endocrine cell types?

Answer 1

*
α-cells secrete glucagon
*
β-cells secrete insulin (the most numerous)
*
δ-cells secrete somatostatin
*
PP-cells secrete pancreatic polypeptide(PP)
*
ε-cells secrete Ghrelin

Question 2

Systemic G homeostasis feedback loops:

Answer 2

Eugalycaemia: a normal concentration of glucose in the blood

Question 3

Essential molecular components of β-cell glucose sensing?

Answer 3

*
Glucose transporters (GLUT1/2)
*
Glucokinase (GCK)
*
Oxidativemetabolism
*
KATP-channels(KATP)
*
L-type voltage-dependant (Ca2+) channels (VDCC)
*
Exocytotic machinery

Question 4

Glucose-stimulated insulin secretion
(GSIS) in pancreatic beta cells role?

Answer 4

Facilitates dose-dependent stimulation of insulin secretion by glucose

Question 5

What is the role of K channel in beta cells?

Answer 5

• At low glucose, the KATPchannel is open, maintaining a hyperpolarised plasma membrane as K leaves the cell.
• At high glucose, closure of the KATP channel depolarises the PM, triggering insulin secretion.

Question 6

Beta cells respond to nutrients, hormones and neurotransmitters and secrete appropriate amounts of insulin. T/F

Answer 6

T

Question 7

Insulin secretion is—-

Answer 7

Biophasic and switch off rapidy at low glucose

Question 8

What happenes to insulin biphases in T2DM?

Answer 8

• The phases have impairments.
• Insulin secretion defects observed early in the aetiology of T2D (pre-diabetes).
• Type-2 diabetes not always associated with insulin resistance (e.g. SIDD).

Question 9

Islet defects in T2DM:

Answer 9

• Impaired insulin secretion.
• Dyregulatedglucagonsecretion
• Lack of suppression of GCG secretion at high glucose. (Glucagon is still releasing regardless that there is less insulin)
• May contributeto hyperglycaemia.

Question 10

What is the function of delta cell?

Answer 10

.Paracrine regulator of islet function
*Somatostatin 14 (sst14) is secreted in response to nutrient or hormonal stimulation.
*SST14 suppresses beta cell and alpha cell function, in a paracrine manner.