describe the processes involved in lipid metabolism during fed state
- dietary fats are hydrolysed by pancreatic lipase
- short chain fatty acid enter circulation directly
- most fatty acid are re-esterified with glycerol in epithelial cells
- triglyceride enter circulation as chylomicrons
- fatty acid stored as fat in adipose tissue or reesterified to triglycerides in liver and exported as VLDL
describe the process of lipid metabolism for fasting state?
- fat in adipose tissue hydrolysed to give glycerol and fatty acids during both fasting and exercise
- fatty acid mobilised and exported to liver and muscles
what does the combination of fatty acid and coenzyme A?
acyl-CoA
what is carnitine used for?
transport acyl-CoA into mitochondria matrix
what inhibits the transport process during fed state?
- malonyl-CoA
what process does acyl-CoA undergo in the mitochondria?
- beta-oxidation
what are the products of beta oxidation?
- FADH2
- NADH
- acetyl-CoA
what is the difference between the beta oxidation in liver and muscle?
- in muscle acetyl CoA oxidise in TCA cycle
- in liver acetyl-CoA converts to ketone bodies
what is the function of hormone sensitive lipase?
- catalyse breakdown of triglyceride to fatty acid
what activates hormone sensitive lipase?
- adrenaline
- glucagon
what inhibits hormone sensitive lipase?
- insulin
describe the function of lipoprotein lipase?
- breaks down chylomicrons and VLDL into chylomicrons remnants which release fatty acid and glycerol
what is lipoprotein lipase activated by?
apoCII
what releases lipoprotein lipase?
endothelial cells in systemic capillaries
where is ketone bodies synthesized?
liver mitochondria
function of ketone bodies?
energy source for brain and muscle where they are reconverted to acetyl-CoA then oxidise in TCA cycle
what is acetoacetate synthesized from?
acetyl CoA
what are ketone bodies?
water soluble products of fatty acid beta-oxidation
when are ketone bodies synthesized?
when there is high circulating fatty acids and low insulin concentration
what does excessive ketone production cause?
metabolic acidosis
describe why defects in mitochondrial fatty acid oxidation sometimes manifest as hypoglycaemia?
- defect cause body to be unable to break down adipose stores to provide energy
- body stores of glucose and glycogen will be depleted
- inability to produce glucose from mitochondria fatty acid oxidation cause low glucose levels
