vesicles to the plasma membrane and release of insulin.

Insulin release is biphasic, where the first peak is due to release of stored insulin and the second peak is due to release of newly synthesised insulin. Insulin release is also increased by fatty acids, amino acids, gastrointestinal hormones (such as glucagon, gastrin, and secretin), the parasympathetic nervous system and drugs including those of the sulphonylurea class. Insulin release is inhibited by stress hormones such as somatostatin, adrenaline and nor-adrenaline and the sympathetic nervous system. Insulin enters the blood stream before binding to the insulin receptor, internalisation and degradation, mainly in the liver but also the kidneys and muscles. It has a half life of 5-6 minutes.

Insulin acts to increase storage of carbohydrate, fats and proteins, reducing the levels of their metabolites, such as glucose, in the blood stream. It provided an evolutionary safety net for times when food was scarce, allowing the body to store away reserves when food was plenty.

Insulin has binds to the insulin receptor where it initiates a cascade of enzymatic phosphorylation, resulting in changes in key activities:

• Changes in glucose transport
• Upregulation in glucose storage and downregulation of glucose synthesis/release
• Promotion of protein storage and inhibition of protein degradation
• Increases in lipid storage and decreases in lipolysis