Lecture 8 - Starvation and Ketosis

Question 1

what is the fuel utilisation of the brain

Answer 1

• almost exclusively glucose
• but can also use ketone bodies

Question 2

what is the fuel utilisation of the liver

Answer 2

• can store and create new glucose
• can utilise most fuels

Question 3

what is the fuel store in the brain

Answer 3

none

Question 4

what is the fuel store of skeletal muscle when resting

Answer 4

glycogen

Question 5

what is the fuel store of skeletal muscle when exercising

Answer 5

none

Question 6

what is the fuel store of heart muscle during exercise

Answer 6

none

Question 7

what is the fuel store of adipose tissue

Answer 7

triacylglycerols

Question 8

what is the fuel store in liver

Answer 8

glycogen

Question 9

what is the preferred fuel of muscle at resting

Answer 9

fatty acids

Question 10

what are the preferred fuels of muscle during exercise

Answer 10

• glucose
• fatty acids
• branch chain amino acids

Question 11

preferred fuel of the heart

Answer 11

fatty acids

Question 12

what are the fuels exported by skeletal muscle during exercise

Answer 12

lactate and alanine

Question 13

what are the fuels exported by adipose tissue

Answer 13

fatty acids

glycerol

Question 14

during starvation what happens to ketone body production

Answer 14

large increase right from the beginning of starvation

Question 15

what happened to glucose levels during the Minnesota starvation experiment

Answer 15

• Begins at a well fed state, then a slight drop initially which will activate the glucagon hormone
• Then as time goes on glucose levels are maintained very stable

Question 16

what happened to urinary ammonia levels during the Minnesota starvation experiment

Answer 16

increases

Question 17

what happened to fatty acid levels during the Minnesota starvation experiment

Answer 17

Increase at the start and then slowly creeping up as the starving continues

Question 18

what happened to total urinary nitrogen levels during the Minnesota starvation experiment

Answer 18

decreases as the body needs to use body proteins for energy

Question 19

what is exogenous glucose

Answer 19

glucose from the diet

Question 20

during the first 4 hours of starvation what is the primary source of glucose for the body

Answer 20

exogenous glucose

Question 21

during hours 4-16 where is most of the glucose for the body coming from

Answer 21

glycogen

Question 22

after hour 16, what is the primary source of glucose in the body

Answer 22

gluconeogenesis - formation of new glucose

Question 23

during starvation what is a important ketone body that supplies the brain with fuel

Answer 23

B-hydroxy-butyrate

Question 24

why is total nitrogen excretion is decreased during starvation

Answer 24

Cause body is trying to spare proteins

Question 25

why is urea decreased during starvation

Answer 25

The first reaction in the urea cycle to produce carbamoyl phosphate requires ATP, so this is decreased as the body tries to conserve energy

Question 26

why is NH3 increased during starvation

Answer 26

ATP is not needed to release ammonia so this is increased as it is a more energy efficient method

Question 27

how are ketones made in the liver in starvation

Answer 27

from catabolism of fat

Question 28

what are the inter-tissue relationships during starvation driven by

Answer 28

Driven by high glucagon to insulin ratio in response to low glucose

Question 29

what do cortisol and adrenaline do in the response to starvation and what are they related to

Answer 29

Related to stress + fight and flight response which will both help along with glucagon in the response to starvation

Question 30

what becomes the prominent hormone when starved

Answer 30

glucagon

Question 31

what is the regulation of fat metabolism in the liver by glucagon during starvation

Answer 31

glucagon inhibits the pathway so that fats can be used to produce ketone bodies instead of bing synthesised

Question 32

what enzyme is inhibited by glucagon in the fatty acid synthesis pathway during starvation and what does this do

Answer 32

acetyl CoA carboxylase - increases Acetyl CoA levels that can be used to make ketone bodies - stops the synthesis of fatty acids through inhibiting malonyl CoA, which promotes B oxidation in mitochondria

Question 33

what does acetyl CoA carboxylase do in fat metabolism

Answer 33

converts acetyl CoA to malonyl CoA

Question 34

why does glucagon inhibit the synthesis of fatty acid during starvation

Answer 34

you need fatty acid for fuel, they need to be going through the B oxidation pathway to make ATP

Question 35

what does malonyl CoA usually do in fatty acid synthesis if there are significant amounts of it around and when would we not want this to be happening

Answer 35

usually inhibits the fatty acids being transported into the mitochondria, which inhibits B oxidation (not what we want to be happening during starvation)

Question 36

does your ability to make ketone bodies depend on age and if so why

Answer 36

yes ketosis is enhanced in new borns because of their low carbohydrate diet and reduced ability to use gluconeogenesis

Question 37

when is your ability to make ketones also increased and why

Answer 37

pregnancy and lactation due to increased glucose requirements

Question 38

what do ketogenic diets promote

Answer 38

promote the use of body fat and ketones

Question 39

why do ketogenic diets reduce insulin secretion

Answer 39

due to low carbohydrates