Insulin is released by the ' β cells' in the islets of Langerhans in response to food. Its role is to lower glucose levels in the bloodstream and promote the storage of glucose in fat, muscle, liver and other body tissues. ' α cells' in the islets of Langerhans produce another important hormone, glucagon, which increase blood sugar levels. Related Theory Type I diabeles is an autoimmune reaction that attacks cells in pancreas that produce insulin and is caused by inherited genetics or environmental elements. Type 2 diabetes happens when body becomes resistant to insulin and is associated with genetics and lifestyle choice.