L76: Pancreas Flashcards
What’s the ““islets of langerhans”
Endocrine pancreas - 3 major cell types. Minority of pancreatic mass.
Exocrine pancreas
Majority of cells. Digestive enzymes and secretions.
What do epsilon cells secrete?
Ghrelin
What do delta cells secrete?
Somatostatin
What do beta cells secrete?
Insulin
What do PP cells secrete?
Pancreatic polypeptide
What does pancreatic polypeptide do?
inhibits acinar cells via paracrine action
What is amylin?
Synergizes with insulin. Can create plaques if built up in stressed out B-cells
C-peptide half life?
35 min. Good indicator of pancreatic function.
Good indicator of pancreatic function
C-peptide
Why is cleavage of C-peptide critical?
exposes end of insulin chain that interacts with receptor
What glucose transporter is on the Beta-cell?
Glut2
What is the “glucose sensor” of the beta-cell?
Glucokinase
What senses ATP from glucose metabolism in B-cell, promoting closure of K+ channels?
SUR subunit
What kind of drugs act on SUR to close the K+ channel, and promote insulin release?
Sulfonylurea drugs
What promotes vesicle (of insulin) release at B-cell?
Ca++ influx
What inhibits insulin release at B-cell?
ACh
What potentiates insulin release at B-cell?
FFA/aa’s (increase ATP through oxidation), and GLP1 (Incretin)
Describe the nature of insulin release
biphasic
Insulin binds what type of receptor?
Tyrosine kinase
Which GLUT is insulin dependent
GLUT4
What two pathways does the insulin receptor promote
- Increase GLUT4 installation
2. Increase growth/mitogenetic actions
What 4 factors does pro-glucagon consist of?
GRPP, glucagon, GLP-1, GLP-2
What happen to GRPP-Glucagon in the pancreatic islet cell?
Cleaved to GRPP + glucagon (Active peptides)
T/F: glucagon phosphorylates the bifunctional enzyme
True, it phosphorylates the enzyme, conferring PHOSPHATASE activity. Dephosphorylation of downstream enzymes promotes gluconeogenesis.
T/F: insulin dephosphorylates the bifunctional enzyme
T: insulin dephosphorylates the bifunctional enzyme, conferring KINASE activity. Phosphorylation of the downstream enzymes promotes glycolysis
What inhibits hepatic ketogenesis
insulin
Can insulin inhibit glucagon secretion at the alpha-cell?
Yes
Can glucagon inhibit insulin secretion at the b-cell?
no
What promotes hepatic ketogenesis?
Catecholamines, glucagon
SS14 (delta cells)
suppresses insulin release
Synergistic with insulin regulation of blood glucose
amylin
Contributes to amyloid formation in beta-cell
amylin
Inverse correlation with ghrelin and
obesity
What two hormones have a permissive effect on gluconeogenesis and lipolysis?
GH and cortisol
Ghrelin has what effect on hypothalamus?
Promotes appetite
What happens if GH is present, but not insulin?
“in the absence of insulin, GH is elevated but cannot stimulate hepatic IGF-1. Result: direct glucose mobilization effects of GH, but no cellular proliferation effects of IGF-1. Also, no negative feedback to GH.”
