glucose metabolism

Question 1

what are the 2 main function of the pancreas (mainly care about 1 for this exam)

Answer 1

glucose metabolism - controlled by endocrine pancreas
digestion - controlled by exocrine pancreas (not on this exam)

Question 2

what are the 2,main cell types and what do they secrete?

Answer 2

alpha - glucagon
beta - insulin

Question 3

how is the release of insulin coupled to an increase in blood sugar level? what is the story and who r the players…

Answer 3

• beta cells expresses GLUT2 which uptake of glucose from bloodstream which is then converted to ATP
• THUS increased in blood glucose > increase uptake into cell via GLUT2 > and increase in ATP within the cell
• There are ATP sensitive K-ch that closes due to increasing ATP > depolarization
• depolarization leads to the opening of voltage-gated calcium ch > influx ca2+ > exocytosis of insulin

Question 4

how does insulin allow glucose uptake in insulin sensitive cells?

Answer 4

insulin receptor = tyrosine kinase
binding > phosphor > signal transduction pathway > translocation of GLUT4 glucose transporter to cell surface

Question 5

name insulin sensitive tissues and insulin insensitive tissues

Answer 5

sensitive: skeletal muscles, adipose, liver
insens: neurons

Question 6

describe what happens in response to decreased blood sugar

Answer 6

alpha cells release glucagon > glucagon causes breakdown of glycogen in liver > glycogenolysis = release glucose > increase glucose in BS

Question 7

how does SNS mediated release of NE affects release of glucagon/insulin?

Answer 7

SNS mediated release of NE promotes release of glucagon from alpha cells but inhibits release of insulin from beta cells

Question 8

describe SNS effects on alpha cells. name players and detail the mechanisms

Answer 8

alpha cells expresses a1 and b2
NE on a1 > Gq > stim PLC > IP3 > release Ca2+ from intra stores > + exocytosis of glucagon
NE on b2 > Gs > stim AC > + cAMP > activates PKA > phos ca2+ ch > Ca2+ influx > increased exocytosis of glucagon

Question 9

describe SNS effects on beta cells. name players and detail the mechanisms

Answer 9

beta cells expresses a2
NE on a2 > Gi/o > inhibit AC > stimulate outward K current > hyperpol > decreased activation of voltage-gated ca2+ ch > decreased exocytosis of insulin

Question 10

describe diabetes

Answer 10

2 types
T1: destruction of pancreatic islet cells by immune system. Result: insulin-dependent patients
T2: beta cell dysfunction or insulin resistance of target tissues
result of both: hyperglycemia

Question 11

what are some clinical treatment for T2 diabetes?

Answer 11

sulfonylureas: for patients with decreased beta cell function (block atp sensitive k ch)
exercise and metformin: patients with decreased insulin receptor function

Question 12

describe mechanism of sulfonylureas

Answer 12

block ATP sensitive K-ch (depol the beta cell > increase insulin release)

Question 13

describe desensitization and down regulation of insulin receptors

Answer 13

pancreas release increasing amounts of insulin in response to high levels of blood glucose > high levels of insulin binding to receptor = desensitization + down reg. > decreased translocation of GLUT4

Question 14

describe how exercise and metformin work

Answer 14

• exercise increase translocation of GLUT4 via insulin independent mechanisms
• metformin activates AMP-activated protein kinase