Insulin Secretion and Intermediary Metabolism

Question 1

What is the hormone that lowers blood glucose?

Answer 1

Insulin

Question 2

What are the hormones responsible for increasing blood glucose?

Answer 2

Glucagon
Catecholamines
Somatotophin
Cortisol

Question 3

What is T1D?

Answer 3

Elevated glucose where insulin is required to prevent ketoacidosis.
Insulin dependent Diabetes

Question 4

What is T2D?

Answer 4

Insulin resistant diabetes

Question 5

Name 4 complications of diabetes:

Answer 5

Diabetic retinopathy
Nephropathy
Heart attacks
Stroke

Question 6

What is the range of glucose concentration for hypoglycemia?

Answer 6

4-5.5mM

Question 7

What could happen if blood glucose falls below 2mM?

Answer 7

Not enough glucose for respiration in the brain; leads to unconsciousness, coma and death

Question 8

What percentage of the pancreas are the islets of langerhans?

Answer 8

2%

Question 9

What are the three main cell types in islets of langerhans?

Answer 9

Alpha - Glucagon
Beta - Insulin
Delta - Somatostatin

Question 10

What is the function of Gap junctions between islet cells?

Answer 10

Allow hormones to have an effect on adjacent cells - paracrine effect

Question 11

What is the function of Tight junctions in islet cells?

Answer 11

Allow formation of small collections of fluid between cells

Question 12

What factors increase insulin secretion? (5)

Answer 12

Increased blood glucose
Certain gastrointestinal hormones
Glucagon
Parasympathetic activity
certain amino acids

Question 13

What are the effects of insulin? (7)

Answer 13

Increaed glycogenesis
Increased glycolysis
Increased glucose transport into cells via GLUT4
Decreased lipolysis
Increased Lipogenesis
Increased protein synthesis
Decreased protein break down

Question 14

What is the effect of somatostatin on insulin/glucagon?

Answer 14

Decreased production

Question 15

What factors affect Glucagon secretion?

Answer 15

Increase secretion:
Decreased blood glucose
Sympathetic activity
Parasympathetic activity
Certain gastrointestinal hormones
Certain amino acids

Decrease secretion:
Insulin
Somatostain

Question 16

What are the main effects of Glucagon?

Answer 16

Increased blood glucose
Main effects are on liver; increase hepatic glycogenolysis
Increased lipolysis/amino acid transport into liver resulting in increased gluconeogenesis

Question 17

How does the glucokinase ‘Glucose sensor’ work?

Answer 17

Glucose enters ß-cells via Glut 2 insulin independent transporter
Glucokinase in ß-cells converts Glucose into G6P; rate limiting step.
This produces ATP which binds to ATP sensitive K+ channel, blocking it, causing depolarisation.
This causes Ca2+ to rush into cell causing Insulin vesicles to exocytose

Question 18

What is used to measure endogenous insulin production levels?

Answer 18

C peptide levels, as produced on 1:1 ratio as cleaved from prohormone

Question 19

What is the incretin effect?

Answer 19

Food stimulates insulin production much more than an IV injection of glucose

Question 20

What is GLP-1? What does it do?

Answer 20

Glucagon like peptide-1
Gut hormone secreted in response to gut nutrients, that increases satiety, stimulating insulin, suppressing glucagon; has a short half life due to the enzyme dipeptidyl peptidase-4

Question 21

Describe the Insulin receptor:

Answer 21

Extracellular alpha subunits bind to the insulin, causing transmembrane beta subunits to allow phosphorylation of cell protein substrates using tyrosine kinase domains

Question 22

How does insulin resistance arise?

Answer 22

Post-receptor cytoplasmic elements of receptor do not work properly