Insulin & Glucagon Flashcards
(32 cards)
When you think of insulin and glucagon what is important?
Substrate levels (very sensitive to what you are being exposed to, i.e. eating)
What hormones are mediated through neural signals instead of what you are eating?
Epinephrine and norepinephrine
What are the 4 major tissues for insulin/glucagon?
1) Liver (gluconeogenesis, FA synthesis, making of VLDLs, glycolysis)
2) Adipose
3) Muscle
4) Brain
What is the most important hormone coordinating use of fuels and where is it made?
Insulin; pancreas (beta cells of Islets of Langerhans)
What is the most powerful anabolic hormone?
Insulin
-Stimulates making of glycogen, TAGs and proteins
How many chains does insulin have? How are they linked?
2 chains; A chain and B chain attached by critical disulfide bond
What does the preproinsulin contain that proinsulin does not?
Signal sequence (guides the protein into the ER where it will be cut out)
Where does proinsulin go?
Golgi apparatus -> C-peptide will be cut -> final product (A + B) -> insulin ready to go just waiting for secretion
What increases secretion of insulin?
Glucose (#1 signal), AAs, and GI peptide hormones
What is the secretion of insulin by pancreatic beta cells closely coordinated with?
Glucagon by alpha cells
-Insulin goes up, glucagon goes down
How will a muscle cell know that you are releasing insulin from your pancreas?
Insulin surface receptor, i.e. receptor tyrosine kinase (RTK)
What happens once the insulin activates RTK?
Internal phosphorylation: tyrosine residues of beta subunit are auto-phosphorylated -> phosphorylates other proteins (insulin receptor substrate-IRS)
What does phosphorylated IRS promote in muscle and adipose cells?
Upregulation of GLUT-4 (glucose uptake)
What does phosphorylated IRS promote in liver and muscle cells?
Glycogen synthesis and protein synthesis
What does phosphorylated IRS promote in liver cells?
Fat synthesis
What does phosphorylated IRS downregulate in liver cells?
Gluconeogenesis and glycogenolysis
What does phosphorylated IRS downregulate in adipose cells?
Lipolysis
-Inhibits HSL and activates lipoprotein lipase
Where is active transport INSENSITIVE to insulin?
Epithelia of intestine
Renal tubules
Choroid plexus
Where is facilitated diffusion INSENSITIVE to insulin?
Erythrocytes Leukocytes Lens of eye Cornea Liver Brain
Where is facilitated transport SENSITIVE to insulin?
Skeletal/cardiac muscle
Adipose tissue
What does insulin downregulate?
Glycogenolysis
Gluconeogenesis
Ketogenesis
Lipolysis
What does glucagon/ephinephrine upregulate?
Glycogenolysis
Gluconeogenesis
Ketogenesis (FA oxidation)
Lipolysis
What is glucagon known as?
Counterregulatory hormone (opposes insulin)
What does glucagon do?
Maintain blood [glucose] by activation of hepatic glycogenolysis/gluconeogenesis
