Diabetes Pathophysiology Flashcards
Define Diabetes Mellitus
A heterogeneous complex metabolic disprder characterised by elevated blood glucose concentration secondary to wither resistance to the action of insulin, insufficient insulin secretion, or both
Briefly explain the structure of Insulin
peptide hormone 2 protein chains linked by disulphide bonds
Where is insulin produced
B-cells of the islets of Langherhans in the pancreas
What sort of hormone is Insulin?
Endocrine- it is released into the bloodstream
what three major cell types are there within the islets of Langerhans?
○ α-cells : produce glucagon ○ β-cells : produce insulin ○ δ-cells : produce somatostatin
How is extracellular glucose transported into the β-cell?
via GLUT2 transporter
After entering the cell what happens to glucose?
- Glucose is metabolised to form ATP which increases ATP:ADP ratio -LEads to closure of ATP-dependent K+ channels - this leads to membrane depolarisation -leads to opening of voltage-dependent calcium channels and a calcium influx -leads to exocytosis of stored insulin vesicles
Explain the 1st phase of insulin release
- Rapid onset
- Lasts around 10 minutes
- Involves the release of pre-docked and primed vesicles
Explain the second phase of insulin release
- A prolonged plateau which lasts as long as the hyperglycaemia lasts
- Release of insulin from granules is complex and involves
Transport –> Docking –> Priming –> Fusion
Are insulin actions mainly anabolic or catabolic?
Anabolic
How does insulin exert its action?
Action via activation of insulin receptor on target cell membrane
Outcome depends on which secondary pathway is activated
Which one of the GLUT transporters is insulin sensitive?
GLUT 4
Where is GLUT 4 stored?
GLUT 4 predominantly stored in IC vesicles
How does insulin facilitate glucose transport into cells?
Insulin promotes fusion of vesicles and transporter insertion into cell walls
Thus facilitates glucose transport into cells
