MCB Lecture 17 The Post-Prandial state Flashcards
What does F-F-F bring about?
Compare the muscles and the liver
Muscles: glycolysis, glycogenolysis
Liver: glycogenolysis, gluconeogenesis
What is the Fright-Flight-Fright response? Where does it target?
This is enacted in times of stress
Fright: adrenaline released
Flight, fight: glycogenolysis, gluconeogenesis
How does glycogenolysis activation differ in the liver and the muscles?
It’s the same
What are the differences between adrenaline pathways in muscle and liver? (2)
- In the muscles, pyruvate kinase is not deactivated (because it doesn’t have the Serine residue
- Adrenaline signals to neurons causing muscle contraction and phosphorylase kinase activation
Describe how neuronal signalling is affected in the FFF response
Neurons release ACh onto ACh receptor Ca2+ released from ER Calciul causes muscle contraction Calcium activates Phosphorylase kinase Glycogen phosphorylase is activates
Describe the steps in the synthesis of Insulin
Preproinsulin
Proinsulin
Signal sequence removed
Disulfide bridges form between A-B and intra chain on A
Insulin
C peptide removed
Give an overview of the insulin signal-transduction pathway
- Insulin binds to the insulin receptor (a tyrosine kinase)
- Tyrosine kinase phosphorylates IRS-1
- Phosphorylated IRS-1 activates PI-3K
- PI-3K catalyses PIP2 -> PIP3
- PIP3 activates PKB
6a. PKB upregulates GLUT4 placement in muscle and fat cells
6b. PKB deactivates GSK3, which can now no longer deactivate Glycogen synthase
What is the receptor in the insulin signal-transduction pathway?
What type of receptor is it?
Insulin receptor
Tyrosine kinase
Describe what the receptor in the insulin signal-transduction pathway does
It phosphorylates IRS-1
What are the targets of PIP3 ? (3)
- Glycogen synthase
- GLUT4
- Glycogen phosphorylase inhibited
How is the MAPK pathway implicated in the post Prandial state?
After we have eaten, protein synthesis is upregulated by MAPK
Insulin signals to muscle and liver cells
IRS-1 is activated and activates Grb-2, which then continues on with the MAPK pathway, activating transcription of genes
What does PIP3 stand for?
Phosphatidyl inositol tri-phosphate
Where are PIP2 and PIP3?
In the cell membrane
Describe GLUT4 deposition in muscle and fat cells
Insulin triggers the deposition of GLUT4 in the membrane of muscle and fat cells so that glucose may be taken up from the blood.
PIP3 activates a protein that leads to deposition of GLUT4
Wat diseases are associated with insulin?
Diabetes mellitus
What is the incidence of diabetes in Australia?
4.3% and rising
What are the two types of diabetes?
Type I: autoimmune destruction of B cells that secrete insulin
Type II: prevalent in obese people, may be genetic. Caused by diet as well
What are the symptoms of diabetes?
Dizziness
Blackouts
Lethargy
What are the biochemical symptoms of diabetes?
Elevated blood glucose during fasting (above 7 mM)
How is diabetes treated?
Synthetic insulin post-Prandially in Type I
Change of diet, weight loss and exercise can reverse type II
How can diabetes be diagnosed?
Oral tolerance test of glucose
Give a person glucose, and monitor glucose concentration in blood
Normal: 7-8 mM
Impaired glucose tolerance: 8-11
Diabetes: more than 11
What type of molecule is insulin
It is a peptide hormone
From where is insulin released?
Under what conditions will it be released?
It is synthesised by the beta cells in the pancreas
It is release when there is high blood glucose concentration (above 7 mM)
