glucose lect 20 Flashcards
what are the primary hormones that regulate plasma glucose
insulin and glucagon
insulin and glucagon secretion is determined primarily by
plasma substrate levels
differentiate between insulin and glucagon in terms of overall function
- insulin: stores excess glucose as fuel when it is in excess
- fed state
- glucagon: promotes the mobilization of glucose when glucose levels are low
- fasting state
insulin and glucagon are released from what organ? What cells specifically
pancreas
- alpha cells: glucagon
- beta cells: insulin
what is the islets of langerhans? what cell populations does it have
- clusters of endocrine cells
- cell population
- B cells: insulin
- a-cells: glucagon
- delta-cells: somatostatin
precleaved insulin consists of what 3 chains
- A chain
- B chain
- c-peptide
list stages of insulin maturation
- preproinsulin
- proinsulin
- packaged into granules
- in granule, proinsulin is cleaved to insulin + C-peptide
release of insulin is tied to ATP production from
glucose
- glucose is the most important stimulator of insulin secretion
define the incretin effect
the increased stimulation of insulin secretion elicited by oral as compared with intravenous administration of glucose under similar plasma glucose levels
what are Incretins
- group of metabolic hormones that stimulate a decrease in blood glucose levels.
- cause an increase in the amount of insulin released from pancreatic beta cells of the islets of Langerhans after eating, before blood glucose levels become elevated
list the two incretins
- glucagon-like peptide-1 (GLP-1)
- gastric inhibitory peptide (GIP)
function of cholecystokinin
peptide hormone of the gastrointestinal systemresponsible for stimulating the digestion of fat and protein.
if the glucose challenge is given intravenously, then the plasma glucose compared to oral glucose load
plasma glucose rises much more rapidly than with oral glucose
insulin acts on what type of cell receptor
tyrosine kinase
- insulin binds to alpha subunit
- b subunits are tyrosine kinase
what is IGF-1? what is important about it
- Insulin-like growth factor 1
- high concentrations of insulin can stimulate the IGF-1 receptor and
- high levels of IGF-1 can stimulate the insulin receptor
describe the process from insulin binding to glucose entering the cell
- kinase activated when insulin binds to a subunit
- autophosphorylates B subunits at the tyrosines and insulin receptor substrates (IRS)
- results in Glut 4 translocation to the cell membrane (in skeletal muscle and adipose tissue)
list the multiple effects of insulin
- increase glucose storage
- increase protein synthesis and decrease proteolysis
- increase growth
- increase triglyceride synthesis and decrease lipolysis
- **tissue uptake of glucose and amino acids is stimulated by insulin and tissue release of glucose, amino acids, and free fatty acids is inhibited by insulin
list insulin effect on liver for carbohydrates
- increase sotrage of glucose
- increase glycogen synthesis
- decrease gluconeogenesis
- promotes conversion of glucose to fat
list insulin effect on liver for lipids
- promotes the synthesis and storage of fat and inhibits fat oxidation
- releases fats which are then stored or used for fuel by adipose tissue and skeletal muscle
list insulin effect on liver for protein
- increase protein synthesis
- decrease protein degradation
list insulin effect on skeletal muscle
- increase protein synthesis and decrease protein degradation
- increased glucose uptake (GLUT4)
- increase glycogen synthesis
- increase glucose breakdown and oxidation which promotes formation of triglycerides
where is the principle site of glucose disposal
skeletal muscle
list insulin effect on adipose tissue
- increase glucose uptake (GLUT4)
- promotes the flow of glucose to fatty acids
- promotes the formation of triglycerides
