Lecture 34 - Starvation Flashcards
What are the key concepts of metabolic homeostasis under starvation
- Maintenance of blood glucose levels
- Sparing to glucose by multiple tissues
- Making alternative fuels available
- Provision of special fuels need of each tissue
- Sparing of structural body proteins
Why must blood glucose be maintained during starvation
The brain relied on glucose for energy and function, particularly before ketone bodies become the primary fuel source
What happens to fuels levels in blood during starvation
- Ketone production increases
- Glucose levels maintaines
- Increase in FFAs
- Protein utilised initially then conserved
Source of glucose from fed to starving
1 stage
- Tissues using glucose: all
- Major fuel for the brain: glucose
5th stages
Origin of glucose: Gluconeogenesis
Tissues using glucose: Brain, RBCs
Major fuel of brain: Ketone bodies and glucose
How long do glycogen stored last after fasting begins
Glycogen lasts for approx 24 hrs
How does the body’s fuel source change during starvation
The body shifts from using glycogen to mobilising FAs and producing Ketone Bodies after glycogen depleted
What is the primary hormone regulating metabolism during starvations
Glucagon
Which hormones potentiate glucagons effects during starvations
Cortisol and adrenaline
How are fatty acids mobilised during starvations
Fat is broken down in adipose tissue and FAs are release unit the bloodstream for use by other tissues
Which tissue primarily use fatty acids during starvation
Muscles and liver utilise for energy
What role does gluconeogenesis play during starvation
It synthesises glucose to maintain blood levels, especially for the brain and RBC
What are the main substrate for gluconeogensis
- Lactate from RBC
- Alanine from muscle proteins
- Glycerol from fats
When does ketone body production increase
Ketone production increases after prolonged starvation when glycogen stores are depleted and gluconeogenesis sloes down
Where are ketone bodies synthesises
Ketone bodies are synthesised in the liver from acetyl coA derived from fatty acids