Insulin molecule. Molecular model of the hormone insulin from a pig. 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 eating, 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.