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How does insulin control key pathways?

This article will enable you to understand the different processes that insulin controls in the healthy body.
© University of Southampton

Insulin is a powerful hormone released to reduce blood glucose concentrations. It acts to promote the 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 bloodstream, insulin also has a number of actions to reduce the amount of glucose re-entering the bloodstream 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. Full colour represents actions that are relevant to the effect of insulin on carbohydrates, whilst faded icons represent actions that do not relate to 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. Full colour represents actions that are relevant to the effect of insulin on fats, whilst faded icons represent actions that do not relate to 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 the release of an amino acid (proteolysis) from muscle

Actions of insulin on proteins diagram. Figure: how insulin acts on protein. Full colour represents actions that are relevant to the effect of insulin on proteins, whilst faded icons represent actions that do not relate to proteins.

If you’d like to learn more about insulin, check out the full online course from the University of Southampton, below.

© University of Southampton
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Understanding Insulin

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