BIOC Lecture 9: Starvation and Ketosis

Question 1

What concepts are involved in energy homeostasis?

Answer 1

• Maintain blood glucose
• Making alternative fuels available
• Sparing of glucose and structural body proteins

Question 2

Why is the liver the ‘king’ of metabolism?

Answer 2

Because it can essentially do everything

Question 3

What 2 tissues can make new glucose?

Answer 3

The liver and kidney

Question 4

What can the liver and kidney do (processes)?

Answer 4

• Use, store and make new glucose
• Supply other tissues with glucose
• Synthesise and store Fatty acids
• Form ketone bodies

Question 5

Compared to the liver - brain, adipose and kidney are much more?

Answer 5

Specific

Question 6

What is adipose specialised for?

Answer 6

Using and storing fat - can synthesise and breakdown.
Adipose only used fat

Question 7

What is the brain specialised for?

Answer 7

Mainly uses glucose and can use ketone bodies

Question 8

What are the only organs that store fuel?

Answer 8

Muscle (resting) = glycogen
Adipose tissue = TAG’s
Liver = glycogen

Question 9

What organs use fatty acids as their preferred fuel?

Answer 9

Everything but the brain

Question 10

What is the preferred fuel of the brain?

Answer 10

Glucose and ketone bodies

Question 11

What organs will use any fuel?

Answer 11

Exercising skeletal muscle and the liver

Question 12

What organs do not export fuels?

Answer 12

Brain, skeletal muscle resting and heart muscle

Question 13

What does skeletal muscle during exercise export?

Answer 13

Lactate and alanine

Question 14

What does adipose tissue export?

Answer 14

Fatty acids and glycerol

Question 15

What does the liver export?

Answer 15

TAGS (VLDL), glucose, ketone bodies

Question 16

What happens to nitrogen during starvation?

Answer 16

Urinary ammonia increases and then plateaus, total urinary nitrogen decreases

Question 17

What is the source of glucose in the first 4 hours of starvation?

Answer 17

Use circulating glucose

Question 18

What is the source of glucose after a day or two of starvation?

Answer 18

Glycogen stores - in both muscle and liver (liver store lasts a lot longer)

Question 19

What happens after multiple days?

Answer 19

The main source is from glucose that is being made mostly in the liver and also the kidney - glycogenesis

Question 20

What happens to total nitrogen excretion during starvation?

Answer 20

Decreased

Question 21

What happens to urea during starvation?

Answer 21

Decreases - starts off well maintain, then drops off because urea cycle requires ATP

Question 22

What happens to ammonia during starvation?

Answer 22

Increases

Question 23

Why does ammonia increase during starvation?

Answer 23

It is more energy efficient to excrete nitrogen as ammonia through the kidneys than it is to be making urea in the liver

Question 24

What happens to uric acid and creatinine during starvation?

Answer 24

Maintained

Question 25

Under starvation mode there is a huge utilisation of?

Answer 25

Fatty acids

Question 26

Increased fatty acid mobilisation causes the generation of a lot of?

Answer 26

Acetyl CoA - this drives ketone bodies production

Question 27

What can be used to make glucose in the liver?

Answer 27

Pyruvate or lactate

Question 28

How does muscle aid in the liver making glucose?

Answer 28

Can provide alanine to the liver to get converted into pyruvate and then glucose

Question 29

How does the muscle aid in making ketone bodies?

Answer 29

release glutamine to the kidney, and via its metabolism make ketone bodies

Question 30

What is driving these huge changes (our tissues to switch in their utilization and production of fuels)?

Answer 30

Mainly glucagon as well as cortisol and adrenaline

Question 31

How does glucagon aid in the starvation response?

Answer 31

It increases and decreases activity of many different enzymes - Therefore it can drive most of what is going on

Question 32

What is adrenaline and cortisol secreted by?

Answer 32

Adrenal glands

Question 33

How do adrenaline and cortisol aid in the starvation response?

Answer 33

Binding to their receptors and generating downstream effects

Question 34

How is fat metabolism regulated?

Answer 34

By glucagon

Question 35

How does glucagon regulate fat metabolism?

Answer 35

By inhibiting lipogenesis

Question 36

How is lipogenesis inhibited?

Answer 36

Because glucagon inhibits the enzyme Acetyl CoA carboxylase

Question 37

What is the role of the enzyme Acetyl CoA carboxylase?

Answer 37

Converts Acetyl-CoA into malonyl CoA

Question 38

Why do we want to inhibit fat metabolism during starvation?

Answer 38

• you don’t want fats being synthesized you want them being utilized for fuel
• allows more acetyl coa to make ketone bodies in the mitochondria

Question 39

What does the ability to make ketones depend on?

Answer 39

Age - newborns make ketones early on compared to adults because they have a reduced ability to make new glucose

Question 40

Other than age, what factor also contributes to increased ketone production?

Answer 40

Pregnancy and lactation due to increased glucose requirements

Question 41

What is ketone body concentration in fed state?

Answer 41

< 0.1mmol/L

Question 42

What is ketone body concentration in fasted state?

Answer 42

0.3mmol/L

Question 43

What is ketone body concentration in starved state?

Answer 43

10mmol/L

Question 44

What is ketone body concentration in newborn babies?

Answer 44

2-3mmol/L

Question 45

What is ketone body concentrations in type 1 diabetes and ketoacidosis?

Answer 45

> 30mmol/L