Insulin molecule. Computer model showing the structure of a molecule of the hormone insulin. Insulin consists of two peptide chains, A and B, which are linked by disulphide bridges. It plays an important role in blood sugar regulation. Insulin is released from the pancreas when blood sugar levels are high, for example after a meal, prompting cells in the liver, muscle, and fat tissue to take up the glucose from the blood and store it as glycogen. Insufficient production of insulin leads to an accumulation of glucose in the blood causing diabetes.