A review of published research from the University of Liege, Belgium, reveals a decline in the number of people experiencing allergic reactions to insulin. This is largely due to better purification of animal insulin and the introduction of human recombinant insulin.
The review also looks forward to the arrival of newly designed molecules that mimic the action of insulin while avoiding triggering an allergic response. In addition new modes of drug delivery, such as continuous subcutaneous insulin infusion (CSII), may help, and early reports suggest that CSII can help people who have previously had an allergic reaction to insulin.
In the 1950s and 1960s more than half of patients who used insulin experienced some form of allergic reaction. This has reduced considerably, but reports show that 0.1% to 3.0% of people still produce reactions that range from mild irritation to life-threatening incidents.
Originally insulin was harvested from animals, and advanced purification now makes this safer to use.
The gene for human insulin has been sequenced, and the sequence placed in bacteria. These modified organisms then produce the human insulin protein which can then be purified and used for therapy. Fewer people react to this 'recombinant insulin' because this is the human protein.
Now that scientists know the gene sequence, the shape of the insulin molecule, and the shape of the active site of the molecule, they can start to redesign it. The idea is to create a molecule that retains the action of insulin, but does not excite the human immune response system. This way it will be active, but will not cause an allergic reaction.
One potential reason for adverse reaction is that insulin is often injected in sudden doses. This gives unnaturally high peaks and troughs of the hormone. To avoid this variation, pumps have been developed that slowly infuse the hormone throughout the day. Early results on these pumps are promising.
"Our review shows just how much progress has been made in reducing allergic reactions to insulin, but more excitingly it shows that there are definite hopes of improving the situation even further," says lead author Regis Radermecker, who works at the Division of Diabetes, Nutrition and Metabolic Disorders at the University of Ličge, Belgium.