Regulation of Blood glucose Levels by Pancreatic Hormones- 25 Flashcards
What is the absorptive state in the Body
Ingested nutrients enter bloodstream from the GI tract
These nutrients support energy requirements for the body
Excess nutrients are stored for use in the post-absorptive state
What is the post-absorptive state.
No nutrients are entering the bloodstream from the GI tract
Switch to net catabolism of stores- breakdown of glycogen, fat and protein
The post-absorptive state must maintain blood glucose levels in the abscence from the GI tract
What do alpha cells produce
Glucagon
What do beta cells produce
Insulin
What state is insulin released in
The absorptive state
What does insulin do to the liver
Increased glucose uptake
increased glycolysis
Increased glycogen synthesis
Inhibition of gluconeogensis
Inhibition of glycogen breakdown
What does insulin do to skeletal muscle.
Increased glucose uptake
Increased glycolysis
Increased glycogen synthesis
Inhibition of glycogen breakdown
What does insulin do to adipose tissue
Increased glucose uptake
Increased glycolysis
Increased triglyceride synthesis
What are the steps of insulin release from pancreatic Beta cells.
Increased uptake and metabolism of glucose leads to an increase in ATP: ADP ratio
Increased ATP: ADP leads to the closure of ATP-sensitive K+ channels and membrane depolarisation
Depolarisation of membrane leads to opening of voltage gated CA2+ channels
The increase in systolic Ca2+ promotes insulin secretion via exocytosis of insulin granules.
What is the process of protein kinase B becoming active.
Binding of insulin to the insulin receptor leads to receptor auto-phosphorylation
Phosphorylated residues on the IR act as binding sites for insulin receptor substrate proteins
IR phosphorylates IRS proteins
Phosphoinositide-3-Kinase binds to phosphorylated residues on IRS proteins, then converts the membrane lipid PIP2 into PIP3
Binding to PIP3 activated PDK1 which then phosphorylates and activates protein kinase B
Acvtivated PKB mediates the intracellular effects of insulin.
How does insulin transport glucose to adipocytes and skeletal muscle
By increasing the amount of GLUT-4 transporters at the cell surface.
Protein kinase B activation is a key step that regulates insulin-stimulated GLUT4 vesicle exocytosis
How does Protein kinase B activation lead to an increase in glycogen synthesis
Insulin signalling leads to activation of protein kinase B
PKB phosphorylates and inactivates Glycogen synthase kinase
This leads to an increase in the active form of glycogen synthase
Increased activity of glycogen synthase increase glycogen synthesis.
What is Fox01 and where is it synthesised
A transcription factor that regulates the expression of gluconeogenic genes
Synthesised in the cytosol but moves to the nucleus to perform the function
How does PKB activation lead to a decrease in gluconeogenesis
It affects the transcription of gluconeogenic genes
PKB phosphorylates Fox01 which prevents it from entering the nucleus
This turns off the expression of gluconeogenic genes.
Why does type 1 diabetes arise
due to a loss of insulin synthesis/release from pancreatic beta cells (autoimmune destruction of beta cells)
