Metabolic Hormones Flashcards
hormones
signaling molecules released by endocrine cells/tissues to influence the function of distant or neighboring cells and organs
islets of langerhan
endocrine component of the pancreas that contains A, B, D, and F cells
a cells
produce glucagon
b cells
produce insulin and amylin
d cells
produce somatostatin
glut 2
located on pancreatic B cells
transports glucose into the cell; senses levels of glucose in the blood to regulate insulin secretion
insulin INDEPENDENT
glut 4
located in skeletal muscle and fat cells
transports glucose into skeletal muscle and fat cells; translocates to cell surface in response to insulin
insulin DEPENDENT
insulin
dipeptide hormone produced by B cells in the islets of langerhan in the pancreas
function of insulin
decrease blood glucose by:
- increasing glucose uptake by skeletal muscle and fat cells
- decreasing glucose production in the liver
insulin synthesis
proinsulin –> A/B chains stabilized by disulfide bridges –> C chain cleaved off –> insulin
what stimulates insulin secretion
hyperglycemia
steps of insulin secretion
- glucose enters pancreatic B cells via GLUT2 transporters
- glucokinase converts glucose –> G6P
- G6P –> ATP –> opens K+ channels –> depolarizes cell
- depolarization opens Ca2+ channels –> Ca2+ influx
- Ca2+ influx causes insulin containing vesicles to mobilize to cell surface and exocytose
insulin receptor
tyrosine kinase receptor
2 extracellular a subunits
2 intracellular B subunits w/ tyrosine residues
what cells have insulin receptors on them
muscle, adipose tissue, liver
mechanism of insulin binding to target cells
- insulin binds receptor
- tyrosine resides on either subunit autophosphorylate each other
- active tyrosine residues phosphorylate IRS-1
- IRS-1 activates PI3 kinase
- PI3K causes translocation of GLUT4 transporters to cell surface
- glucose enters cell via GLUT4 transporters
effects of insulin in the liver
- stimulate glycogen synthesis
- inhibit glycogenolysis
- inhibit gluconeogenesis
- stimulate FA synthesis
- stimulate glycolysis
effects of insulin in skeletal muscle
- stimulate glucose uptake via GLUT4
- increase glycogen storage
- stimulate glycolysis
effects of insulin in adipose tissue
- stimulates lipoprotein lipase and fatty acid synthase (lipogenesis)
- inhibits fat mobilization
- stimulates glycolysis
- stimulates leptin
effects of insulin the the brain
- inhibits feeding behavior
- increases metabolic rate
insulin resistance
reduced ability of insulin to perform its normal actions in target cells
causes of insulin resistance
- obesity
- corticosteroids/Cushing’s
- inflammation
- oxidative stress
- free fatty acid accumulation
effects of insulin resistance
hyperinsulinemia –> diabetes
glucagon
polypeptide hormone produced by A cells in pancreas
function of glucagon
increase blood glucose by:
- stimualting glyocenolysis
- stimulating gluconeogenesis
what is glucagon derived from
proglucagon
what stimulates glucagon secretion
hypoglycemia and epinephrine
function of epinephrine
increases hepatic glucose production –> increases blood glucose
- inhibits insulin
- stimulates glucagon
function of glucocorticoids
increases hepatic glucose production and inhibits glucose uptake by tissues –> increases blood glucose
- chronic high levels of glucocorticoids causes Cushing’s –> can develop insulin resistance and diabetes