Hormonal Regulation Of Fuel Homeostasis

Question 0

Explain the increase of anabolic actions of insulin.

Answer 0

Increase transporters in muscle and adipose to increase glucose uptake.
Increase glucokinase to increase glucose uptake.
Activate glycogen synthetase to increase glycogen production.
Increase synthesis of FA and AGP to TAG in adipocytes.

Question 1

What is insulin?

Answer 1

Polypeptide released from beta cells of the islets of langerhans - released in the absorptive state (BGL>5mM). Targets liver, muscle and adipocytes to increase glucose oxidation, increase glycogen synthesis and protein synthesis - an anabolic hormone.

Question 2

Explain the decrease in catabolic actions if insulin.

Answer 2

Inhibit glycogen phosphorylase to decrease glycogenolysis.
Inhibit gluconeogensis.
Inhibit ketone production in the liver.
Decrease intracellular lipase activity to inhibit adipocytes lipolysis.

Question 3

Glucagon?

Answer 3

Polypeptide from alpha cells - post absorptive state, targets liver to generate glucose. Glycogenolysis, gluconeogensis, ketone production. Catabolic.

Question 4

Cortisol?

Answer 4

Maintains liver and adipose enzymes for gluconeogensis and lipolysis.
Low [cortisol], like absorptive state - Addison’s disease.
High [cortisol], like post absorptive - Cushings.

Question 5

Growth hormone?

Answer 5

Polypeptide from anterior pituitary. Make adipose more sensitive to lipolysis stimuli.
Increase gluconeogensis in liver and decrease the effect of insulin and increase glucose uptake.
Acromegaly.

Question 6

Explain the neural control of glucose levels.

Answer 6

Decrease in plasma glucose.

Increase in adrenaline.
Increase glycogenolysis in skeletal muscle.
(increase activity of symp nerves to adipose and liver)
Increase lipolysis in adipose.
Increase glycogenolysis.
Increase gluconeogensis
Increase plasma glucose, FA and glycerol.

Question 7

What are the responses to prolonged fasting/starvation?

Answer 7

1) FA and ketones utilisation by peripheral tissue - glucose sparing for CNS.
2) Short term, protein to amino acids and to glucose by the ketoacid pathway.
3) Long term (3-4 days)…brains uses ketone and glucose…ketones from FA from TAG…less protein catabolism…less muscle wastage.
4) efficient mechanisms: after 4 days, decrease BGL by a few percent.
After a month decrease BGL by 25%.

Question 8

What are the responses to exercise?

Answer 8

Increase glucagon and decrease insulin.

Decrease glucose, increase adrenaline, increase sympathetic discharge in islets.

Question 9

Diabetes?

Answer 9

No/low insulin.

Increase catabolism.
Increase glycogenolysis.
Increase lipolysis.
Hyperketonaemia, acidosis.
Diabetic ketoacidosis.

Decrease anabolism.
Hyperglycaemia
Glycosuria
Osmotic diuresis.
Water and salt depletion.

Fatal if untreated.

Question 10

Explain the symptoms of diabetes associated.

Answer 10

Hyperglycaemia - fatigue.
Lipolysis - wasting, weight loss.
Hyperketonemia - vasodilation, hypotension and hypothermia.
Osmotic diuresis - thirst and polydipsia.