Week 1 - Hormonal Regulation of Carbohydrate Metabolism

Question 1

What are the acute manifestations of HYPOglycemia?

Answer 1

Palpitations, tachycardia, diaphoresis, anxiety, weakness, hunger, nausea

Question 2

What are the chronic manifestations of HYPOglycemia?

Answer 2

hypothermia, confusion, hallucinations, seizure, coma

Question 3

What are the acute manifestations of HYPERglycemia?

Answer 3

polydipsia, polyphagia, altered vision, weight loss, mild dehydration

Question 4

What are the chronic manifestations of HYPERglycemia?

Answer 4

cardiac arrhythmias, coma

Question 5

What portion of the pancreas is endocrine?

Answer 5

The islets; make up 1-3% of pancreas

Question 6

What do beta-cells secrete?

Answer 6

insulin & IAPP (Islet Amyloid Polypeptide)

Question 7

What is the function of IAPP?

Answer 7

Slows gastric emptying and inhibits glucagon secretion

Question 8

What portion of islet endocrine cells are beta cells?

Answer 8

~60%

Question 9

What do alpha-cells secrete?

Answer 9

glucagon

Question 10

What do delta-cells secrete?

Answer 10

somatostatin

Question 11

What is the function of somatostatin?

Answer 11

inhibits both insulin & glucagon

Question 12

Aside from alpha, beta, and delta cells, what are the other type of pancreatic islet cells?
- what do they secrete?

Answer 12

PP cells

- secrete pancreatic polypeptide

Question 13

What is the function of PP (pancreatic polypeptide)?

Answer 13

reduces appetite and food intake

Question 14

What is the parasympathetic innervation to the pancreatic islet?

• what neurotransmitter?
• what is its effect?

Answer 14

Vagus nerve

• ACh
• increases insulin release

Question 15

What is the sympathetic innervation of pancreatic islets?

• what neurotransmitter?
• what is its effect?

Answer 15

Post ganglionic fibers of celiac ganglion

• NE
• inhibits insulin secretion

Question 16

What is the precursor to insulin in the synthesis pathway?

- where is it synthesized?

Answer 16

Proinsulin (A- & B-chains; C-peptide)

- RER of beta-cell

Question 17

What stimulates insulin secretion?

Answer 17

• glucose, Arg/Lys, FFA
• GIP, GLP-1, glucagon
• ACh

Question 18

What inhibits insulin secretion?

Answer 18

• NE/Epi
• Somatostatin
• Prolonged glc&FFA

Question 19

How does glc stimulate insulin secretion?

Answer 19

Glc enters beta-cells via GLUT-2

• phosphorylated to Glc-6-PO4
• glycolysis –> makes ATP
• closes ATP-sensitive K+ channels
• generates AP (depolarization)
• Ca++ channels open (Ca++ flows into cell)
• exocytosis of insulin granules

Question 20

What are the major target tissues for insulin?

Answer 20

Muscle, fat, liver

Question 21

What organs have GLUT-2?

Answer 21

Liver & pancreatic beta-cells

Question 22

What is the action of insulin on fat & muscle cells?

Answer 22

• insulin binds receptor
• PI3K signalling pathway
• stimulates translocation of GLUT-4 vesicles
• GLUT-4 expressed on cell surface
• glucose enters cell

Question 23

What are the acute effects of insulin on individual target tissues?

Answer 23

Fat - glc gets stored as fat (lipogenesis)

Muscle - glc used as energy or stored (as glycogen or protein)

Liver - increases glycogen synthesis; inhibits gluconeogenesis & glyogenolysis;

Question 24

Specifically how does insulin cause increased fatty acid and triglyceride synthesis?

Answer 24

Stimulate lipoprotein lipase (breaks down lipoproteins to FFAs –> can enter adipocyte)
Stimulates FA synthesis from glc

Inhibits hormone-sensitive triglyceride lipase - inhibits triglyceride breakdown in adipocytes

Question 25

The insulin receptor is in what class of receptor types?

Answer 25

Tyrosine kinase

Question 26

What is included as part of the proglucagon molecule?

Answer 26

GRPP, Glucagon, IP-1, GLP-1, IP-2, GLP-2

Question 27

What are enteroendocrine cells?

Answer 27

Specialized endocrine cells in GI tract and pancreas

• respond to stimuli to produce GI hormones/peptides
• initiate digestive actions & detect toxins

Question 28

Name some specific enteroendocrine cells in the intestine and state their function.

Answer 28

K cells - secrete GIP
L cells - secrete GLP-1 & GLP-2
Enterochromaffin cells - secrete serotonin

Question 29

What is GIP?

Answer 29

Gastric Inhibitory Peptide (an incretin)

Question 30

What is GLP-1?

Answer 30

Glucagon-like peptide-1 (an incretin)

Question 31

What enteroendocrine cells are found in the stomach?

- what is their function?

Answer 31

G cells - secrete gastrin

Enterochromaffin-like cells - secrete histamine

Question 32

What enteroendocrine cells are found in the pancreas?

Answer 32

alpha-cells, beta-cells, delta-cells, PP cells

Question 33

What is ghrelin?

• where is it produced?
• what causes it to be released?
• where does it act?
• what is its effect?

Answer 33

“hunger hormone” “Growth Hormone RELease-INducing”

• produced in GI tract (mainly stomach & duodenum)
• in response to empty stomach
• acts on hypothalamus
• increases feeling of hunger, increases gastric acid secretion & GI motility, decreases insulin secretion

Question 34

What is the major site of glucagon action?

- what are glucagon’s effects there?

Answer 34

Liver

• increase glycogenolysis
• increase gluconeogenesis

Question 35

What stimulates glucagon release?

Answer 35

• hypoglycemia
• amino acids
• GIP, CCK
• ACh, NE

Question 36

What inhibits glucagon release?

Answer 36

• insulin, somatostatin

- GLP-1

Question 37

How does the ANS directly affect metabolism regulation in the liver?

Answer 37

Sympathetic: stimulates hepatic glc output

Parasympathetic (vagus): stimulates hepatic glc uptake

Question 38

What are some counterregulatory horomones to insulin?

Answer 38

GH, Cortisol, Epi

Question 39

How does cortisol affect glc homeostasis?

Answer 39

• cortisol is released in response to low glc
• stimulates gluconeogenesis
• decreases translocation of GLUT-4
• INCREASES glycogen synthesis