INSULIN Flashcards
Half life of insulin
5-6 min
Uses of C peptide
Assessment of Beta cell function
Distinguish between endogenous and exogenous hyperinsulinemia
Factors the promote insulin secretion
Glucose
Fatty acids
Ketones
Amino acids
Why does oral glucose have a higher insulinotropic effect than IV glucose
Due to the incretin effect
Which adrenergic receptors promote and inhibit insulin secretion
Alpha-2 inhibits secretion
Beta-2 promotes secretion
Effect of vagal nerve stimulation on insulin release
Promotes insulin secretion
What effect does any condition that activates sympathetic system have on insulin release
Inhibits it through alpha2 receptor activation
What is the rate limiting step in glucose metabolism in the beta cells
Phosphorylation by Glucokinase (Hexokinase IV)
The different forms insulin goes through during secretion
Insulin is initially synthesized as preproinsulin
Preproinsulin is cleaved to produce proinsulin
Proinsulin is then cleaved to Insulin and C peptide
Parts of preproinsulin
Single peptide (SP)
B chain
C-peptide
A chain
Are the actions of insulin anabolic or catabolic
Anabolic
Functions of insulin
Stimulates glycogenesis, lipogenesis, protein synthesis and inhibits their catabolism
Inhibits gluconeogenesis
Stimulates transport of substrates and ions into cells
What type of receptor is the insulin receptor
Kinase linked receptor
Types of kinase linked receptors
Receptor tyrosine kinases
Serine/thréonine kinases
Cytokine receptor
Examples of receptor tyrosine kinases
EGF, FGF, insulin receptors , NGF, Toll like receptors
Examples of serine/threonine kinases
Transforming growth factor
Effect of insulin oh glycogen synthase
Insulin enhances the activity of glycogen synthase
Which hormones stimulate insulin secretion
Glucagon
Growth Hormone
Corticotrophin
Placenta Lactogen
Secretin
Gastrin
Cholecystokinin
Catecholamines
Which hormones stimulate insulin secretion
Glucagon
Growth Hormone
Corticotrophin
Placenta Lactogen
Secretin
Gastrin
Cholecystokinin
Catecholamines
Incretins
How does hypoxia affect insulin release
Inhibits insulin release
Name the incretins
GIP- Gastric inhibitory peptide or Glucose dependent insulinotropic peptide
GLP-1 - Glucagon-like peptide-1
Functions of the incretins
Increase insulin secretion
Prevent beta cell apoptosis
Inhibit glucagon release
Increases satiety
Reduce gastric emptying time
Which enzyme inactives the incretins
DPP-4
Dipeptidyl peptidase-4
Explain the incretin effect
Oral glucose intake elicits a higher insulin response compared to IV glucose that produces the same levels of serum glucose levels.
Source of the incretins
GIP - K cells of the duodenum and jéjunum
GLP- 1- L cells of the ileum and colon
Structure of insulin
51 amino acids
A chain - 21 amino acids
B chain - 30 amino acids
How is insulin release in response to glucose
Biphasic insuline response
Initial repaid release in the first 2 minutes
Second release 5-10 mins later
How is glucose different from other products in stimulating insulin release
Only glucose stimulates synthesis of insulin
