L21 - Blood Glucose Control II

How many grams of glycogen stored in liver?

50g/kg of liver

How many grams of glycogen stored in muscles?

10g/kg muscle

Why can’t organs store glucose as glucose?

Glucose would attract H2O into organs, storage as glycogen is one molecule, reducing osmosis into organs

How many days of glycogen is stored in the liver at rest?

3 days

How many days of glycogen stored during exercise?

3 hours

How many days can most humans last without food?

40

What is gluconeogenesis?

Occurs after first 3 days of fast, making new glucose in liver, using proteins (amino acids) from muscles, lactate and glycerol

What allows gluconeogenesis in hibernation?

More muscle, smaller brains → less need for glucose

How does insulin affect skeletal muscles?

The insulin receptors signal phospholipid bilayer vesicles with GLUT4 to translocated and insert to sarcolemma to allow glucose uptake

Insulin signal transduction pathway

Insulin never enters cell, instead binds to IR and sends signal to GLUT4 vesicle to translocate, if the pathway was discovered it could treat diabetes

What age does DM1 occur?

<16 years, thought to be autoimmune

What cells are destroyed in the pancreas in DM1?

Beta cells → insulin not produced

Why DM1 causes hyperglycemia

Insulin not released → GLUT4 stays intracellular → glucose cannot enter cell

Glucose → glycogen pathway

Insulin binds to IR → GLUT4 vesicles translocate and allow glucose transport → glycogen synthase makes alpha 1-4 bonds between glucose

How does insulin inhibit glycogen breakdown?

Inhibits phosphorylase, reducing hepatic glucose output and suppressing gluconeogenesis

What causes liver glucose output to go down?

LGO decreases when insulin signals cells to uptake glucose

Structure of the insulin receptor

Alpha subunit, beta subunit, tyrosine kinase (phosphorylates), insulin receptor substrate 1 (IRS1) becomes IRS1-P (first step of transduction pathway)

What is the issue in DM2?

Insulin released but IR does not work as well → need more insulin than pancreas can make, tyrosine kinase does not phosphorylate, defect in signalling GLUT4

What is insulin shock?

Too much insulin causing blood glucose to drop → hypoglycemic, CNS dysfunction…

How do the beta cells know when to release insulin?

They directly respond to glucose levels in the blood