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Carbohydrate metabolism

Insulin

  • Produced in B cells in Islets of Langerhans of the pancreas
  • Is a polypeptide containing two chains of amino acids
  • Structure is very similar between different species
  • Synthesised as a preprohormone
  • Half life of about 5 minutes

Principle actions of insulin

Adipose tissue

  • Increased glucose entry
  • Increased fatty acid synthesis
  • Increased glycerol phosphate synthesis
  • Increased triglyceride deposition
  • Activation of lipase
  • Increased potassium uptake

Muscle

  • Increased glucose entry
  • Increased glycogen synthesis
  • Increased amino acid uptake
  • Increased protein synthesis
  • Decreased protein catabolism
  • Increased ketone uptake
  • Increased potassium uptake

Liver

  • Decreased ketogenesis
  • Increased protein synthesis
  • Increased lipid synthesis
  • Decreased glucose output

Effects of insulin deficiency

Decreased glucose uptake

  • Hyperglycaemia
  • Glycosuria
  • Osmotic diuresis
  • Electrolyte depletion

Increased protein catabolism

  • Increased plasma amino acids
  • Negative nitrogen balance

Increased lipolysis

  • Increased plasma free fatty acids
  • Ketogenesis
  • Ketonuria

 
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