Starvation (L36) Flashcards
What does the body need to do during starvation?
Supply brain with fuel
Supply other tissues with fuel
Conserve protein as much as possible
What are the main fuel stores mobilised during starvation?
TAGs in adipose tissue
What is the main hormone involved in starvation?
Glucagon
How are the products of TAG digestion transported and used by the body during starvation?
Glucagon stimulates lipolysis:
- Glycerol enters blood and goes to liver
- Free fatty acids complexed with albumin travel in blood to be used by all aerobic tissues except brain
How is liver glycogen mobilised?
Glycogenolysis:
- Glycogen is phosphorylated to G1P
- Rearrangement by mutase by G6P
- Hydrolysed to removes phosphate to form glucose
What organ benefits from liver glycogen mobilisation?
The brain - for a day
How is the brain fuelled after glycogen stores are depleted?
Ketone bodies
What is gluconeogenesis?
Synthesis of new glucose by the liver
What are the substrates for gluconeogenesis, and where do they come from?
Lactate = muscle glycogen
Alanine = muscle protein
Glycerol = TAGS
Note: fatty acids (acetyl-CoA) cannot be used as only 2C, but ATP and NADH from B oxidation can be used in gluconeogenesis
What hormone stimulates gluconeogenesis?
Glucagon
Where are ketone bodies synthesised?
liver
What molecule provides the substrate to synthesise ketone bodies?
Fatty acids
How are ketone bodies generated and used to make energy?
Fatty acids undergo B oxidation –> acetyl-CoA, which undergoes ketogenesis –> acetoacetate and B-hydroxybutyrate
Acetoacetate can undergo process in brain to form acetyl -CoA to then be fed into CAC
What are the phases of starvation from point of view of glucose metabolism?
- Exogenous: glucose
- Glycogen: glucose
- Gluconeogenesis: glucose
- Ketone bodies
What are the metabolic adaptations to starvation?
- Fatty acids can be used as fuel by all aerobic tissues
- Ketone bodies used by brain .: demands less glucose
- Muscle degradation can slow down
= Body can survive longer
