Insulin counter-regulatory hormones

Question 1

Which hormone controls blood glucose levels during fasting?

Answer 1

Glucagon

Actives processes to release glucose and fatty acids

Question 2

Which cell in the Islets of Langerhans produces glucagon?

Answer 2

Alpha cells

Question 3

Describe the structure of glucagon

Answer 3

29aa peptide

Question 4

When is glucagon secreted?

Answer 4

When blood glucose levels are too low
Increase in blood amino acids
During exercise

Question 5

Which molecules inhibit glucagon secretion?

Answer 5

Insulin

Somatostatin

Question 6

What type of receptor is the glucagon receptor?

Answer 6

G protein coupled receptor

Question 7

What happens to Gluconeogenesis and Lipolysis when no insulin is being secereted? (inhibited or not inhibited)

Answer 7

Insulin usually inhibits these processes. When there is no insulin there is no inhibition

Gluconeogenesis is not inhibited by insulin

Lipolysis is not inhibited by insulin

Question 8

Which biomarker is used to monitor insulin concentration in the blood

Answer 8

Monitor the C- peptide level

1 C peptide 1 Insulin molecule

Question 9

What effect does glucagon have on gluconeogenesis and glycolysis? Where in the body are these effects exerted?

Answer 9

increases gluconeogenesis and inhibits glycolysis in the liver

Question 10

What happens to triglyceride stores during fasting? Relate to insulin and glucagon.

Answer 10

Lipolysis occurs-
Break down of triglycerides

(Hormone sensitive lipase is inhibited by insulin and activated by glucagon/PKA)

Question 11

What happens to beta oxidation in a fasted state where glucagon concentration is high.

Answer 11

β oxidation is inhibited-

Malonyl-CoA inhibits transport of FFAs into mitochondria via CPT-1

Glucagon stimulates CPT-1

Question 12

During fasting, what happens to the Acetyl-CoA which can not enter the TCA cycle? Where does this Acetyl-CoA come from?

Answer 12

Converted into ketone bodies

It comes from fatty acid breakdown which occurs during prolonged fasting

Question 13

State the 3 types of ketone bodies

Answer 13

Acetoacetate
Acteone
Beta-hydroxybutyrate

Question 14

Where are adrenocortical hormones released from?

Answer 14

The adrenal medulla in the adrenal gland

Question 15

Name two physiological states can lead to the release of catecholamines?

Answer 15

Stress

Hypoglycaemia

Question 16

Which amino acids are used to produce the monamines for catecholamines?

Answer 16

phenylalanine and tyrosine

Question 17

Which molecules are broken down in short term stress and in long term stress?

Answer 17

Short term- liver converts glucagon to glucose which is released into the blood

Long term- Protein and fats are converted to glucose or broken down for energy

Question 18

Where and how are Glucocorticoids released?

Answer 18

Where- Adrenal cortex in the adrenal gland

How- The cortex has many low density lipoprotein receptors. These enable cholesteral uptake for steroid hormone synthesis

Question 19

Which hormone stimulates the release of cortisol? Where is this hormon produced?

Answer 19

adrenocorticotropic hormone

The pituitary

Question 20

What are the metabolic functions of cortisol? List 4

Answer 20

It enhances gluconeogenesis

It inhibits glucose uptake
(and utilisation)

It stimulates muscle proteolysis

It stimulates adipose-tissue lipolysis

(rapid mobilisation of amino acids and fatty acid stores)

Question 21

Which proteins are not broken down (mobilised) by cortisol?

Answer 21

Functional proteins-
Muscle contractile proteins
Neuronal proteins

Question 22

How does cortisol help to resist stress and inflammation?

Answer 22

For stress it maintains blood pressure

For inflammation it suppresses it

Question 23

What happens to your muscles when cortisol is elevated for prolonged periods of time?

Answer 23

Muscle wasting occurs due to proteolysis

Question 24

What effect do growth hormones have on adipose tissues?

Answer 24

• Increases lipolysis
• Reduces glucose uptake
• Reduces lipogenesis
• Reduces the re-esterification of free fatty acids
• reduces body fat mass

Question 25

When can ketone bodies by produced?

Answer 25

Starvation (prolonged fasting)

prolonged exercise

Question 26

What effect do growth hormones have on skeletal muscle?

Answer 26

Reduces glucose uptake in skeletal muscle
Increases the activity of LPL’s
Increases beta oxidation

Question 27

What effect do growth hormones have on the liver function?

Answer 27

Increases VLDL secretion from liver
Increases HL activity
Reduces PPARa expression
Increases production and uptake of IDL, LDL and HDL

Question 28

Name the two types of thyroid hormones

Answer 28

Tetraiodothyronine, thyroxine (T4) and Triiodothyronine (T3)

Question 29

What is the intracellular function of thyroid hormones?

Answer 29

activate nuclear receptors and transcription of large number of genes

Question 30

Which thyrpid hormone is more potent and by how much?

Answer 30

T3 is about 4 times more potent than T4

Question 31

Describe the difference in the concentrations of the two thyroid hormones within the tissues and within the blood

Answer 31

T4 is higher in the blood and T3 is higher in the tissues

This is because T4 concentration is higher in blood and it converted into T3 at the tissues

Question 32

What is the main function of thyroid hormones. Describe 3 metabolic actions of thyroid hormones which enable this to occur.

Answer 32

Increase the basal metabolic rate

1. Increase in the number and activity of mitochondria
   Increases the rate of ATP synthesis
2. Stimulation of carbohydrate metabolism
   Rapid glucose uptake
   Enhanced glycolysis and gluconeogenesis
   Increased insulin secretion
3. Stimulation of fat metabolism
   Lipid mobilised rapidly from fat tissue
   Increased fatty acids concentration in the plasma

Question 33

What are incretins? Give 2 examples

Answer 33

Gastrointestinal hormones

1. Glucagon-like peptide-1
2. Gastric inhibitory peptide

Question 34

What is the definition of hypoglycaemia?

Answer 34

any abnormally low plasma glucose concentration
that exposes the subject to potential harm” with a proposed threshold
plasma glucose value <70 mg/dL (<3.9 mmol/L)

Question 35

Describe 5 causes of hypoglycemia

Answer 35

High insulin doses

Alcohol excess (inhibition of gluconeogenesis)

Insulinoma (A tumour of pancreatic β cells)

Excessive exercise (Leading to increased glucose utilisation)

Reactive hypoglycaemia (Excessive insulin secretion in response to a high carbohydrate meal in the pre-diabetic condition)

Question 36

List 6 symptoms of mild hypoglycaemia

Answer 36

Trembling, palpitation, sweating, anxiety, hunger, tingling

Question 37

List 6 symptoms of severe hypoglycaemia

Answer 37

Confusion, disorientation, convulsion, fitting, seizures,

loss of consciousness, coma

Question 38

What happens in prolonged hypoglycaemia? What is the consequence of this?

Answer 38

Growth hormone and cortisol are secreted –
they decrease the rate of glucose utilisation
by most cells converting to fat utilisation?

neuroglycopaenia
(shortage of glucose for the brain)
Brain damage
Loss of cognitive function, seizures and coma