How does insulin control key pathways?

Insulin is a powerful hormone released to reduce blood glucose concentrations. It acts to promote storage of glucose, proteins and fats and it has actions on the liver, muscle and adipose tissue.

Essential knowledge

In greater depth

Actions of insulin on carbohydrates

Insulin achieves a reduction in blood glucose by stimulating glucose uptake, storage of glucose as glycogen and metabolism of glucose to ATP .

In addition to removing glucose from the blood stream, insulin also has a number of actions to reduce the amount of glucose re-entering the blood stream from the liver. It reduces the rate of release of glucose from the liver by:

  1. Inhibiting glycogenolysis
  2. Stimulating glycogen synthesis
  3. Stimulating glucose uptake
  4. Stimulating glycolysis
  5. Indirectly inhibiting gluconeogenesis via inhibition of fatty acid mobilisation from adipose tissue

Actions of insulin on carbohydrates diagram Figure: how insulin acts on carbohydrates

Actions of insulin on fats

Insulin also has significant effects on lipid metabolism. In the liver, insulin increases the synthesis of lipoproteins. It also reduces the rate of β-oxidation of lipids, as the rate limiting step is inhibited by insulin.

Both these actions result in an increase in circulating lipids. Insulin also reduces ketogenesis in the liver and lipolysis in the adipose tissue, as hormone sensitive lipase is inhibited by insulin.

Actions of insulin on fats diagram Figure: how insulin acts on fats

Actions of insulin on protein

Insulin promotes building up protein and inhibits the breakdown of protein.

Insulin has the following effects on protein metabolism:

  • Stimulates transport of free amino acids across plasma membranes in liver and muscle
  • Stimulates protein biosynthesis in muscle
  • Reduces release of amino acid (proteolysis) from muscle

Actions of insulin on proteins diagram Figure: how insulin acts on protein

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This article is from the free online course:

Understanding Insulin

University of Southampton