W27-L2: Post-Prandial glucose metabolism Flashcards
What are the 4 cell types in the islets of langerhans and what do they secrete?
β-cells: insulin and amylin
δ-cells: somatostatin
α-cells: glucagon
φ-cells: pancreatic polypeptide
What are the roles of prohormone convertases?
PC 2 cleaves pre-pro to pro, PC 1 cleaves pro to insulin
Which chain of insulin is not highly conversed?
Other chains are conserved across animals but C peptide varies greatly and is allowed to mutate
What is insulin packaged with in secretory granules?
Endopeptidase enzymes
What are the phases of insulin secretion?
1st phase is a sharp rise that lasts for 2-5 minutes
2nd phase is if glucose is still high, prolonged secretion that lasts for duration of stimulus
Where are GLUT 2 and glucokinase expressed?
Pancreas and Liver
What is special about GLUT 2 and glucokinase?
High Km, So GLUT 2 is not saturated quickly, proportional uptake to blood levels
How does amino acids stimulate insulin secretion?
Increased ATP via TCA cycle then closes K+ channels and lets Ca2+ (like glucose)
How does fatty acids stimulate insulin secretion?
Via increasing Malonyl CoA which inhibits CPT-I
When is more insulin secreted, after oral or IV administration? Why?
Oral, glucose in the gut triggers hormones to induce insulin secretion
What are Incretins?
gut-derived hormones secreted in response to nutrients eg. glucose, fatty acids, amino acids
What are two examples of incretins?
GLP-1 and GIP
What is the role of Glucagon like peptide 1 (GLP-1)
stimulates proinsulin biosynthesis and release as well (but only if glucose is high)
promotes ß cell growth and function
What isn’t GLP-1 used for T2D?
Short half life
What are the therapeutic agents related to GLP-1?
Agonists (analogues of GLP-1) and DPP-4 inhibitors (inhibit enzyme which break it down)
What is action of Glucose-Dependent Insulinotropic Polypeptide?
activates lipoprotein lipase
What is action of Amylin?
Inhibits glucagon secretion and food intake
What is action of Glucagon?
Stimulates the liver to release glucose hence restoring the blood glucose to normal
What is action of Pancreatic polypeptide?
Inhibits food intake and is released after a meal
What is action of Somatostatin?
Inhibits insulin and glucagon secretion
