pancreatic hormones Flashcards
describe the cell types found in pancreatic islets and their specific hormone they secrete
- alpha cell = glucagon and proglucagon
- beta cell - insulin, C-peptide, proinsulin, IAPP, GABA
- Delta Cells = somatostatin
- Epsilon cells = ghrelin
- PP or F cells = pancreatic polypeptide
describe glucose on insulin release
- most potent stimulator of insulin release
- Increases intracellullar ATP –> causes inhibition of K channel leading to depolarization of the membrane
- results in Ca influx and that triggers release of insulin containing vesicles
describe vagal stimualtion on insulin release
- acetylcholine activates M3 receptors and increases intracellular Ca
- causes the release of insulin
describe GLP1 and Somatostatin effects on insulin release
- Glucagon-like peptide (GLP1) amplifies insulin release
- somatostatin can INHIBIT insulin release
describe catecholamines on insulin release
- beta adrenergic stim (epineprhine) amplifies secretion
- alpha-adrenergic stimulation can INHIbIT insulin release
describe the cellular events that take palce during glucose and acetylcholine stimulated insulin secretion
- glucose moves down conc gradient into cell (likely thru glucose transporter 2) –> leads to increase ATP in cell
- Increase ATP inhibits K channels causing membrane to depolarize and allowing Ca to flow in
- Ca influx leads to insulin release
What are the cellular consequences taht occur following activation of insulin receptors
- broadly activates intracellular signaling pathways
- outcomes are mitogenic (cellular growth) and metabolic
what are the metabolic consequences of insulin on the liver
- promotes anabolism = glycogen synth/storage
- inhibits glycogen breakdown
- increases protein, and triglyceride synth
- inhibits catabolism (inhibits glycogenolysis, ketogenesis and gluconeogenesis)
what are the metabolic consequences of insulin on adipose tissue
- increases triglyceride storage by promoting free FA uptake, promote esterification of free FAs and inhibits lipolysis
what are the metabolic consequences of insulin on skeletal muscle
- increase protein synth by increasing AA uptake
- increases glycogen synth by increasing glucose uptake
- increasing glycogen synthase activity
- inhibiting glycogen phosphorylase
Where can you find Glut 4 receptors
- skeletal muscle, adipose tissue
- insulin mediated uptake of glucose
where can you find Glut 2 receptors
- pancreatic B-cells, liver/kidney/gut
- leads to insulin release
what are the regulators of glucagon secretion
- glucagon has opposite effects of insulin and produced by alpha cells in the gut
- Glucose INHIBITS glucagon secretion
- FA INHIBIT glucagon release
- Catecholamines and GI homrones (CCK, gastrin) PROMOTE glucagon release
- Para and Symp stimulation PROMOTE glucagon release
describe the effects of glucagon and insulin on ketogenesis
- glucagon promotes ketogenesis
- insulin inhibits ketogenesis
- Triglycerides to ketones or glucose
describe the effects of glucagon and insulin on gluconeogenesis
- Insulin Inhibits
- glucagon promotes
- Amino acids (glycerol/lactate) to glucose
describe the effects of glucagon and insulin on Glycogenesis
- Insulin promotes glycogenesis
- Glucose to glycogen (storage)
describe the effects of glucagon and insulin on Glycogenolysis
- Glucagon promotes Glycogenolysis
- Glycogen to glucose (energy)
describe the effects of glucagon and insulin on Glycolysis
- Insluin promotes glycolysis
- Glucagon inhibits
- Glucose to pyruvate
what are the physiological impact of insulin, glucose and glucagon administration on blood glucose levels
- insulin decreases glucose in blood
- glucagon rapidly increases glucose in the blood
Define IAPP
- produced by B cells
- packaged in same vesicles as insulin
- Decreases glucagon secretion
- inhibits GI motility
- regulates appetite
Define pancreatic polypeptides
- secreted by F or PP cells in pancreas
- regulated by vagus nerve and neuronal control
- regulates exocrine function of pancreas, gallbladder contraction, gastric acid secretion and GI motility
define Somatostatin
- secreted by Delta cells
- secreted in response to same stimuli as insulin
- produced also in brain, peripheral neurons, endocrine cells of stomach/pancreas
- INHIBITS insulin secretion thru activation of SSTR-5
Define Ghrelin
- secreted by epsilon cells
- produced also in heart, lung, kidney, IS, hypothalamus and pituitary
- shown to INDUCE GASTRIC EMPTYING, gastric acid secretion and increase appetite
define Glucagon related peptides (GLP)
- Can yield GLP1 or GLP2
- GLP1 secreted in response to meal (insulin AMPLIFIER) and promotes production and secretion of insulin and somatostatin (neg reg of insulin)
- GLP1 protects and promotes growth of B cells
- DPP-4 breaks down GLP1
