Starvation Flashcards
What happens to glucose during a food deficit?
Glucose decreases
What effects does low glucose have?
Decreased insulin production
Increased glucagon and noradrenaline production
Increased cortisol production (during early starvation)
What affect does increased glucagon have on glycogenesis and glycogenolysis?
Activates glycogen phosphorylase - activates glycogenolysis
Inhibits glycogen synthase - inhibits glycogenesis
How long do liver glycogen stores last?
12 hours
How is blood glucose maintained after 12 hours?
Gluconeogenesis
AA in the muscle are transaminate to alanine.
Alanine is transported to the liver
Transaminated back to pyruvate using alpha-keto-glutarate.
Pyruvate froms glucose in gluconeogenesis
What is the effect of glucagon on glycolysis?
Inhibits pyruvate kinase so inhibits
What is the effect of glucagon on gluconeogensis?
Stimulate fructose-1,6bisphosphatase which is key enzyme in gluconeogenesis
What is the effect of high acetyl CoA due to fatty acid breakdown?
It inhibits pyruvate carboxylase so stops pyruvate -> acetyl CoA
Activates pyruvate carboxylase which directs pyruvate to gluconeogenesis
Why are there protein losses associated with fasting?
Proteins converted to alanine to fuel gluconeogenesis which decreases protein synthesis.
Increased production of urea - loss of nitrogen
Why is lipogenesis increased?
Decreased insulin activates hormone sensitive lipase
What is the fate of glycerol from lipolysis?
Enters gluconeogenesis to from glucose
What is the fate of fatty acids from lipolysis?
Oxidised in beta oxidation to form acetyl CoA
What is the fate of acetyl CoA?
TCA cycle.
Excess is used in ketogenesis
What are ketone bodies used for?
Energy for the brain
After 16 days of fasting what occurs in the brain for the use of ketone bodies?
Enzyme induction occurs to produce the enzymes needed to utilise ketone bodies for energy
What are the effects of adaption?
Brain utilises ketone bodies for energy. Requirement for glucose decreases, rate of gluconeogenesis decreases. Less protein loss and nitrogen loss in the urine
What happens to hormone levels during trauma?
Increased glucagon and adrenaline causing hyperglycaemia
How does hyperglycaemia occur during trauma?
Insulin resistance - so glucose cannot re-enter cells
Increased gluconeogenesis due to increased glucagon.
Demand for glucose does not increase so it is not used up
What happens in relation to the cori cycle during trauma?
Increased activity
Pyruvate converted to lactate
Transported to the liver
Lactate to pyruvate which is used in gluconeogenesis.
Glucose can not enter cells because of insulin resistance
Why is there a marked protein loss during trauma?
Increased amount of glutamine used as fuel fro the immune system. Less available for protein synthesis
