Diabetes Treatment, Part 3: Insulin and Incretins

Insulin is the oldest and the most effective treatment to control glucose levels in diabetic patients. It was first used in the treatment of diabetes by Frederick Banting and Charles Best in 1922. Although originally thought to be a cure for diabetes, it soon became evident that insulin was a method of controlling the disorder. Insulin has been the most versatile of diabetes treatments because it may be used to control any degree of hyperglycemia of type 1 or type 2 diabetes. Although it was initially prepared by isolation from animal pancreatic tissue, insulin is now prepared through recombinant DNA techniques using microorganisms. Use of recombinant insulin has decreased the immunogenicity of commercially available insulin.

Type 1 diabetes is characterized by a loss of ß-cells and therefore an absolute insulin deficiency. The mainstay of therapy, therefore, is insulin treatment. Because the disease does not affect insulin sensitivity, patients typically require small doses of insulin to maintain control of glucose levels. Type 2 diabetes, however, is characterized by preexisting insulin resistance followed by a relative insulin deficiency. As a result of insulin resistance and progressive insulin deficiency, patients with type 2 diabetes typically require higher doses of insulin and gradual upward titration of insulin doses.

Since the discovery of insulin and its use to treat diabetes, insulin has been combined with additives and modified at the molecular level to change its pharmacokinetic properties. Some insulin preparations accelerate insulin's effects in the bloodstream, whereas others prolong the pharmacokinetic profile. These insulin preparations may be used alone or in combination with other insulins in formulating an insulin regimen.

Rapid- and Short-Acting Insulins

Regular insulin. Regular insulin was the first available insulin preparation and therefore the first short-acting insulin. At the time of injection, regular insulin self-associates to form hexamers, which are poorly absorbed into the circulation. …