insulin release and metabolic homeostasis

Question 1

What is metabolic homeostasis

Answer 1

the mantinance of the metabolic processes required to ensure an optimal level of essential molecules to life

Question 2

What are some of the specific tissue requirements for fuel

Answer 2

Brain - glucose, ketones (fasting)
RBC - glucose
adipose - FFA
SM + liver - any fuel source
heart - FFA

Question 3

how can vascular glucose levels connect glucose sensation in insulin secretion

Answer 3

Increased vascular glucose -> PBC increased glucose via GLUT1
metabolic increase -> increased ATP production -> closes ATP gated K-channel
depolarisation -> opening of Ca2+ channels -> second messanger signal to cause insulin granule exocytosis

Question 3

how can the GIT connect glucose sensation in insulin secretion

Answer 3

GIT glucose increase:
L-cells decet increase -> secrete proglucagon, cleaved via convertase enzyme to GLP-1
GLP-1 binds to receptors on PBC -> insulin released

• used as unregulated weight loss - effecting brain, pancreases, gastric emptying
• used as T2 diabetes treatement

Question 4

how is insulin processed in PBC

Answer 4

translated in the ribosomes in rER to preproinsulin
- signal chain dropped makes proinslin
- disulfide bridges form between alpha and beta chains to stabilises
moves through golgi -> forms inulin vessicles
- c-chain remoed to form mature inslin
- c-chain has longer halflife and can be used as a marker of insulin secretion

Question 5

How does insulin facilatite a decrease in blood glucose levels

Answer 5

Binds to a RTK on cells -> triggers phosphorylation cascade -> activation of the glut4 secretory vessicles (GSV) -> movement of GLU4 to the cell surface
increased uptake of glucose into cells