Endocrinology & Metabolism 1 - Fuel metabolism

Question 1

What is anabolism?

Answer 1

The use of chemical energy to build up macromolecules from precursors

Question 2

What is catabolism?

Answer 2

The breakdown of macromolecules to generate chemical energy

Question 3

What are the two reasons for whole body metabolism?

Answer 3

1) storage of nutrients/break down of stores when required

2) Maintenance of blood glucose (primary source for the brain)

Question 4

How can we divide metabolism?

Answer 4

1) Fed state (anabolic)

2) Fasted state (catabolic)

Question 5

What are the percentage of total energy stores for each food group?

Answer 5

Carbohydrate (stored as glycogen) = 1%

Lipids/fats (stored as triglycerides) = 77%

Proteins (mostly mobilised by skeletal protein) = 22%

Question 6

What is energy balance?

Answer 6

Energy input = work performed + heat produced

work performed = 40% (comes from mechanical, chemical and transport)

heat produced = 60% (maintain body temperature)

Question 7

What is a positive balance?

Answer 7

Energy input > energy output (energy in excess of output gets stored)

Question 8

What is a negative balance?

Answer 8

Energy input < energy output (net breakdown of macromolecules to provide energy)

Question 9

What are the characteristics of energy metabolism during fed state?

Answer 9

Nutrients in bloodstream plentiful 
Insulin is the hormonal control
Glycogen formed
Triglycerides formed
Protein formed

Question 10

What are the characteristics of energy metabolism during fasted state?

Answer 10

Energy stores must be metabolised
Maintain energy source for brain and other neural tissue
Glucagon is the hormonal control
All macromolecules produced are converted into energy

Question 11

Where is insulin released?

Answer 11

Beta cells in the Islets of langerhans in the Pancreas

Question 12

What can stimulate insulin secretion?

Answer 12

• Mostly Glucose but amino acids and fatty acids can also stimulate
• Gut hormones (Incretins) enhance insulin release through an anticipatory response by potentiating the beta cells so there is a big enough release of insulin to lower the spike in blood glucose through food intake

Question 13

How much do Incretins affect insulin release after eating?

Answer 13

60% post-meal insulin secretion

Question 14

What are alpha cells?

Answer 14

Cells in the islets of langerhans that secrete glucagon

Question 15

What are delta cells?

Answer 15

Cells within the islets of langerhans that secrete somatostatin

Question 16

What is somatostatin?

Answer 16

Inhibits the release of both glucagon and insulin

Question 17

What is the communication between these cells?

Answer 17

Paracrine communication

Question 18

How does innovation and the nervous system affect insulin release?

Answer 18

Muscarinic receptors on the beta cells are the receptors from parasympathetic nerves (Increase insulin secretion)

Alpha2-adrenoreceptors on the beta cell are sympathetic receptors (decrease insulin secretion) and can also bind to adrenaline

Also beta-adrenoceptors stimulate beta secretion but there are not as many present on the beta cell compared to alpha adrenoceptors

Question 19

What does insulin do in the body?

Answer 19

Lowers blood glucose levels

Question 20

Where does insulin work?

Answer 20

Liver:

• Increase in glycogen synthesis
• Decreasing in glycogen breakdown
• Decrease glucneogenesis (glucose production from pyruvate and amino acids)

Adipose tissue:

• Increase glucose uptake (via GLUT4)
• Increase in lipogenesis (anabolic)
• Decrease in lipolysis

Skeletal muscle:

• Stimulates glucose uptake (through GLUT 4 moving to cell membrane by cell signalling)
• Increase in protein synthesis (anabolic)
• Reduces protein breakdown

Question 21

What type of receptor is Insulin receptors?

Answer 21

Tyrosine Kinase receptors

Question 22

How does glucagon release occur?

Answer 22

• Stimulated by low blood glucose by both parasympathetic and sympathetic NS
• Stimulated by amino acids
• Inhibited by high blood pressure

Question 23

What are the main action of glucagon?

Answer 23

Raises blood glucose

• Stimulates hepatic glycogenolysis
• stimulates hepatic gluconeogenesis
• stimulates lipolysis

Question 24

What is the normal range of healthy human for blood glucose?

Answer 24

4-8mmols/L

Question 25

What are the 4 hormones that counter regulate insulin?

Answer 25

Glucagon
Adrenaline
Growth Hormone
Cortisol

All increase glucose production

Question 26

What is hypoglycaemia? Symptoms?

Answer 26

<4mmol/L
Low blood glucose

Dizziness
Hunger
Irritability
Headache
Tingly Lips
Anxiety
Tremors
Sweating

Can all lead to loss of consciousness and ultimately coma due to glucose deficiency in the brain

Question 27

What is hyperglycaemia? Symptoms for both?

Answer 27

> 7mmol/L fasted
11mmol/L 2h after eating
High blood glucose

Increased urination
Thirst
Dehydration

Acute: >40mmol/L
Confusion
High temperature
Seizure
Coma

Chronic:
Cardiovascular disease
Stroke
Retinopathy
Neuropathy
Nephropathy

Question 28

What is the most common endocrine disorder?

Answer 28

Diabetes

Question 29

How is diabetes caused?

Answer 29

• Insulin deficiency (type 1) 5-15%

- Impaired beta-cell function or loss of insulin sensitivity (type 2) 85-95%

Question 30

What is Type 1 Diabetes?

Answer 30

Autoimmune disease

• progressive destruction of beta-cells
• rapid onset

Treatment with Insulin, regular exercise and a healthy diet

Question 31

What is Type 2 Diabetes?

Answer 31

Relative insulin deficiency and/or insulin resistance

Onset usually >40 years old
Gradual onset

Treatment with healthy diet and drugs such as insulin injections

Question 32

What are other causes of diabetes?

Answer 32

Loss of pancreatic function

Excess of glucagon/adrenaline/growth hormone/cortisol