Lecture 8 - Starvation and Ketosis Flashcards
what is the fuel utilisation of the brain
- almost exclusively glucose
- but can also use ketone bodies
what is the fuel utilisation of the liver
- can store and create new glucose
- can utilise most fuels
what is the fuel store in the brain
none
what is the fuel store of skeletal muscle when resting
glycogen
what is the fuel store of skeletal muscle when exercising
none
what is the fuel store of heart muscle during exercise
none
what is the fuel store of adipose tissue
triacylglycerols
what is the fuel store in liver
glycogen
what is the preferred fuel of muscle at resting
fatty acids
what are the preferred fuels of muscle during exercise
- glucose
- fatty acids
- branch chain amino acids
preferred fuel of the heart
fatty acids
what are the fuels exported by skeletal muscle during exercise
lactate and alanine
what are the fuels exported by adipose tissue
fatty acids
glycerol
during starvation what happens to ketone body production
large increase right from the beginning of starvation
what happened to glucose levels during the Minnesota starvation experiment
- 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
what happened to urinary ammonia levels during the Minnesota starvation experiment
increases
what happened to fatty acid levels during the Minnesota starvation experiment
Increase at the start and then slowly creeping up as the starving continues
what happened to total urinary nitrogen levels during the Minnesota starvation experiment
decreases as the body needs to use body proteins for energy
what is exogenous glucose
glucose from the diet
during the first 4 hours of starvation what is the primary source of glucose for the body
exogenous glucose
during hours 4-16 where is most of the glucose for the body coming from
glycogen
after hour 16, what is the primary source of glucose in the body
gluconeogenesis - formation of new glucose
during starvation what is a important ketone body that supplies the brain with fuel
B-hydroxy-butyrate
why is total nitrogen excretion is decreased during starvation
Cause body is trying to spare proteins
why is urea decreased during starvation
The first reaction in the urea cycle to produce carbamoyl phosphate requires ATP, so this is decreased as the body tries to conserve energy
why is NH3 increased during starvation
ATP is not needed to release ammonia so this is increased as it is a more energy efficient method
how are ketones made in the liver in starvation
from catabolism of fat
what are the inter-tissue relationships during starvation driven by
Driven by high glucagon to insulin ratio in response to low glucose
what do cortisol and adrenaline do in the response to starvation and what are they related to
Related to stress + fight and flight response which will both help along with glucagon in the response to starvation
what becomes the prominent hormone when starved
glucagon
what is the regulation of fat metabolism in the liver by glucagon during starvation
glucagon inhibits the pathway so that fats can be used to produce ketone bodies instead of bing synthesised
what enzyme is inhibited by glucagon in the fatty acid synthesis pathway during starvation and what does this do
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
what does acetyl CoA carboxylase do in fat metabolism
converts acetyl CoA to malonyl CoA
why does glucagon inhibit the synthesis of fatty acid during starvation
you need fatty acid for fuel, they need to be going through the B oxidation pathway to make ATP
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
usually inhibits the fatty acids being transported into the mitochondria, which inhibits B oxidation (not what we want to be happening during starvation)
does your ability to make ketone bodies depend on age and if so why
yes ketosis is enhanced in new borns because of their low carbohydrate diet and reduced ability to use gluconeogenesis
when is your ability to make ketones also increased and why
pregnancy and lactation due to increased glucose requirements
what do ketogenic diets promote
promote the use of body fat and ketones
why do ketogenic diets reduce insulin secretion
due to low carbohydrates
