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Teacher 2011

Diabetes (advanced level)

Age range 16-19

Page 6 of 10

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Insulin preparations

Insulin is a 51 amino acid protein and needs to be injected into the body rather than taken orally to avoid being broken down in the digestive system.

Early insulin treatments used the hormone isolated from cow (bovine) and pig (porcine) pancreas. This needed a great deal of purification to isolate the insulin and even then, there were contaminants. The preparations were short-acting and could cause allergic reactions.

In 1955, the amino acid sequence of human insulin was discovered. The amino acid sequence of porcine insulin is different to human insulin by one amino acid. Bovine insulin differs by three amino acids.

Modern insulin is now obtained from bacteria that have been genetically modified to produce human insulin. By further manipulating the insulin, it has been possible to develop a range of medications that have different properties. For example, adding zinc causes the insulin molecules to form hexamers (six insulin molecules loosely attached to each other). This form of insulin is absorbed into the body more slowly than regular insulin, thus reducing the need for more frequent insulin injections.


Range of insulin preparations, from short acting to long acting

Range of insulin preparations, from short acting to long acting.



New Treatments

Injecting insulin on a regular basis can cause problems and researchers are constantly working to develop better ways to take insulin.

Skin patches are being developed that allow the insulin to be directly absorbed into the body and implants under the skin may also be a treatment of the future.

Small pumps which inject insulin under the skin in a controlled way throughout the day are now available. Miniaturised 'nanopumps' may soon replace the large pump shown here.

Insulin pump

Pumps deliver controlled amounts throughout the day.

Insulin Nanopump

Using nanopumps may allow insulin to be delivered from pumps the size of skin patches.

Courtesy of: Insulin Nanopump™ from Debiotech SA, Switzerland

Inhaled insulin-powders have been developed to enable the hormone to be absorbed directly into the blood from the nose and mouth mucosa. This bypasses the digestive system. These have so far proved unpopular with patients and their use is limited.

Transplants of the pancreas and islet cells from donors are becoming more common treatments. People with diabetes, particularly if they have associated kidney disease that requires a kidney transplant, may be given a whole pancreas from a donor. More commonly people with diabetes may be given donor islet cells. These donor cells are isolated from the several donors and then injected into the hepatic vein. From here they travel in the blood and become lodged within the liver and produce insulin. This procedure is called islet cell embolisation. As a result of both of these procedures insulin production in individuals with type 1 diabetes is reinstated and they no longer have to inject insulin.

In the future it may be possible to grow large numbers of beta cells from stem cells in the laboratory. This would be a much more readily available supply of insulin-producing beta cells which can then be used for islet cell embolisation.

Treating type 2 diabetes

Lifestyle changes play a key role in the management of type 2 diabetes, and initial steps include regular physical activity, a balanced diet and loss of any excess weight. For a large proportion of people with type 2 diabetes changes to their lifestyle will reduce their blood glucose levels sufficiently. However if levels remain high even with these changes, then medication is usually required.

There are five types of medicines that are used to treat type 2 diabetes. However, these should be used in addition to a change in lifestyle. The groups of medicines are:

  • Metformin
    Acts on the liver to reduce the production of glucose from fatty acids. Increases the uptake of glucose by skeletal muscle. Protects cells lining the blood vessels from damage and so reduces cardiovascular disease.
  • Sulphonylureas and Meglitinides
    Bind to receptors on the beta cells in the pancreas and promote insulin release.
  • Acarbose
    Inhibits the enzyme that breaks down polysaccharides in the diet and so slows the absorption of glucose in the small intestine to prevent the glucose peak after a meal.
  • Gliatazones
    Increases the sensitivity of fat, liver and muscle cells to insulin.

Long acting insulin may, if necessary, be administered once a day.

Question 4

Compare and contrast the treatment of type 1 and type 2 diabetes. Highlight the reasons behind using each type of treatment.

Click to see what our expert thinks

Acarbose
This type 2 diabetes medication is not much used now.
Amino acids
The basic building blocks of proteins. There are twenty amino acids used, in different combinations, to make every protein required by the human body.
Fatty acid
Large molecule consisting of a carboxylic acid (RCOOH) with the 'R' being a long unbranched hydrocarbon chain.
Hormone
A chemical messenger produced by a particular gland or cells of the endocrine system. Hormones are transported throughout the body in the blood stream but they produce a response only in specific target cells
Insulin
A hormone produced by the pancreas. It is active in controlling blood glucose levels as it allows cells in the body to take in and store glucose.
Liver
A large organ in the upper abdomen which manufactures, stores and breaks down substances as required by the body
Mucosa
The membrane that lines the body's cavities and passages. In certain areas, such as the nose and mouth, this membrane absorbs substances and secretes mucus.
Pancreas
An endocrine gland which produces insulin
Polysaccharides
Complex carbohydrates consisting of more than one sugar molecule.
Proteins
A polymer made up of amino acids joined by peptide bonds. The amino acids present and the order in which they occur vary from one protein to another.
Receptors
Protein molecules attached to cells that only bind to specific molecules with a particular structure.
Stem cells
Undifferentiated cells that can develop into a diverse range of specialised cell types.