Glucose Regulation Flashcards
Where in the body are glucagon receptors mainly expressed?
In the liver and kidneys.
On which human cells have insulin receptors been detected?
All cell types tested in the Human Protein Atlas.
What differentiates the effect of insulin on blood glucose from the effect of glucagon on blood glucose?
Insulin decreases blood glucose, while glucagon increases blood glucose.
Which blood glucose regulating hormones are released by the pancreatic islets?
Insulin, glucagon, and somatostatin.
Which blood glucose regulating hormones are secreted by the small intestine?
Glucagon-like-Peptide-1 (GLP-1) and Gastric Inhibitory Peptide (GIP) aka Glucose-dependent Insulinotropic Peptide.
What are 2 examples of incretins? What do they do?
- Glucagon-like-Peptide-1 (GLP-1)
- Gastric Inhibitory Peptide (GIP)
Proteins that amplify the effects of insulin.
In the endocrine pancreas, which cells secrete insulin? Which cells secrete glucagon? Which cells secrete somatostatin? Where are all these cells located?
All in the Islets of langerhans.
(Inner) Insulin: β cells
(Outer) Glucagon: α cells
(Outer) Somatostatin: δ (delta) cells
What kind of feedback effects does insulin have on the islet cells?
Activates β cells, inhibits α cells.
What kind of feedback effect does glucagon have on the islet cells?
Activates α cells, β cells, and δ(delta) cells.
What kind of feedback effect does somatostatin have on the islet cells?
Inhibits α cells and β cells.
How are glucagon and GLP-1 similar? How are they different?
Similar: made from same precursor
Different: GLP-1 inhibits glucagon secretion and promotes insulin release + function
Describe the cause of hypoglycemia. What are some symptoms of this?
Blood sugar levels which are too low. Can cause loss of consciousness, brain damage, and even lethal coma.
Describe the cause of hyperglycemia. What are some symptoms of this?
Elevated blood sugar levels. Acts as a short-term appetite suppressant but can lead to diabetes mellitus: eye, kidney, heart disease + nerve damage.
How is diabetes mellitus brought about?
Either through a lack of insulin production (type 1) or development of insulin resistance (type 2).
How was supplemental insulin acquired for diabetics in the past? What about now?
Used to use pork or beef insulin, today use recombinant technology to make synthetic insulin.
Which 3 pathways are responsible for controlling insulin secretion in the pancreas?
- MAPK
- PKC
- PI3K
Why would insulin be stored in the pancreas?
Because it takes a while to make, so it’s important to have some on hand for instant release in response to food.
What ion is necessary for the release of insulin from the pancreas? What else is required?
Calcium and glucose stimulate the synthesis and release of insulin.
How do pancreatic cells link blood glucose levels to insulin secretion?
By employing a glucose “sensor”: K+ channels coupled to metabolism which depolarizing the membrane, allowing entry of Ca2+ into the cell when glucose levels are high.
How long does insulin last in the body once released? What gets rid of it?
Lasts 3-5 minutes in circulation before being degraded by insulinases in the liver, kidney (and placenta).
Describe the 5 general steps of insulin release.
- Glucose enters the cell
- ATP + cAMP block K+ channel, cell depolarizes the cell. Incretins act.
- Ca2+ cannels open, Ca2+ enters the cell
- Ca2+ and cAMP/PKA cause insulin release
- cell repolarizes
How do incretins GIP and GLP-1 act in the cell during the insulin-release process?
They increase intracellular cAMP/PKA, potentiating other steps.
What 3 important growth factors utilize growth factor receptors/tyrosine kinase receptors?
- Insulin-like growth factor 1 (IGF-1)
- Insulin-like growth factor 2 (IGF-2)
- Insulin
How did insulin and insulin-like growth factor (1 and 2) evolve?
Genes duplicated, allowing one copy to mutate without messing up the organism.
