What is Insulin - an account on its action, its role in diabetes and its uses as a drug

Online Physician By Online Physician, 25th Sep 2011 | Follow this author | RSS Feed
Posted in Wikinut>Health>Drugs & Medicines

Insulin is an anabolic hormone secreted by the β cells of the pancreas. Lack of insulin secretion or its action in the target tissue is the pathophysiology of diabetes mellitus and replacement of insulin as a drug is one of the commonest and standard treatments of diabetes. This article discusses the action of insulin, its role in diabetes and its uses as a drug.

What is insulin?

Insulin is an anabolic hormone (a hormone causing storage and growth) secreted by the β cells of the islets of Langerhans of the pancreas. Being a hexamer secreted in response to glucose or other stimuli like amino acids it has a normal basal level with peaks after each meal. Lack of insulin secretion or its action in the target tissue is the pathophysiology of diabetes mellitus and replacement of insulin as a drug is one of the commonest and standard treatments of diabetes (particularly type I). Therefore, a thorough knowledge on insulin is crucial for health care professionals to offer a better management to the increasing number of patients suffering from diabetes mellitus. Though this hub is mainly aimed at educating the healthcare professionals and medical students the medical terms have been clarified as much as possible for the interest of the lay community.

How does insulin act?

Insulin has several actions in the human body. Being an anabolic hormone it increases glucose uptake, particularly in muscle, liver and adipose tissue (Here the brain is not under the control of insulin dependent glucose uptake). At the same time insulin suppresses glucose output from liver, glycogenolysis (break down of glycogen in the liver and muscle), gluconeogenesis (synthesis of glucose from amino acids and glycerol). It increases lipolysis (break down of fat in the body). The uptake of amino acids into muscles is promoted and breakdown of muscle (protein catabolism) is reduced.

Instances where insulin is used as a drug

As mentioned above, the pathophysiology of diabetes mellitus is lack of insulin and therefore one of the best methods of management of diabetes is to replace insulin. Thus, the uses of insulin are multiple with regard to diabetes.
• In Type 1 diabetes it is essential for survival since the synthesis of hormone is reduced
• In Type 2 diabetes it may be necessary for control in certain individuals where the response to oral hypoglycaemic agents is poor and at later stage when production of insulin is also law apart from the peripheral resistance to insulin
• In gestational diabetes to optimize the outcome insulin is used
• Women with diabetes mellitus become pregnant since oral hypoglycaemic agents cannot be used
• Rapid-acting insulin is used in hyperglycemic emergencies like diabetic ketoacidosis and hyperosmolar non ketotic coma (HONK)
• In late onset autoimmune diabetes mellitus of adult (LADA)
• Transiently in type 2 diabetes in special situations such as surgery or infection

What are the types of insulin?

In history until 1980’s insulin was manufactured from pancreas of cattle and pigs called bovine and porcine insulin respectively. However, in the present days human insulin, known as insulin analogues is produced by recombinant DNA technology; examples are rapid –acting insulins like Aspart and Lispro and long-acting insulin like Glargine. Human insulin is more potent, less antigenic and better absorbed than non-human insulins.
Unmodified insulin in solution has a short half life with short onset of action peak and duration of action; which is usually used with meals and as supplemental insulin namely rapid acting and short acting insulin. Intermediate acting insulin is made by adding substances to the unmodified insulin thereby slowing the breakdown of the molecule; which has a slower onset, peak and longer duration of action. Long acting insulin has longer duration of action and it is used to maintain the basal levels of insulin. It is as larger crystals and this crystallization delays subcutaneous absorption. Here Glargine and Determir are long acting insulin analogs; which have constant pharmacokinetic profiles consistent with physiologic basal insulin secretion.

In conclusion..........

Insulin is an anabolic hormone secreted by the β cells of the pancreas. Lack of insulin secretion or its action in the target tissue is the pathophysiology of diabetes mellitus and replacement of insulin as a drug is one of the commonest and standard treatments of diabetes. However, prior to the use of insulin as a drug, the dose has to be determined and the type of insulin suitable for each individual should be decided. The individual should become aware of the technique of injection and the common adverse effects. These are discussed in detail in another article.

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Comments

author avatar Denise O
7th Feb 2012 (#)

Good info. Thank you for sharing.:)

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