Drugs in Sport: Insulin abuse subject to testing

Insulin cheats beware

Although it’s more usually associated with the regulation of blood glucose, the hormone insulin can also act as a powerful anabolic agent, helping to drive glucose and amino acids (the building blocks of protein) into muscle cells, thereby helping to increase glycogen synthesis and lean muscle mass. And when combined with anabolic steroids, insulin also helps prevent muscle tissue breakdown. Given the widespread availability of artificial insulin, it’s perhaps hardly surprising that growing numbers of athletes are reportedly using it in an effort to boost performance illegally.

The International Olympic Committee banned the use of this hormone by non-diabetic athletes in 1998, but the problem is that a test to catch insulin abusers does not yet exist, because chemical testing procedures to date have not been able to differentiate sufficiently reliably between the synthetic insulins produced for medical use, and the endogenously produced insulin produced naturally by the body. However, that looks set to change following some research conducted by German scientists at the University of Cologne.

What the scientists did was study athletes, diabetic patients and healthy controls (non-insulin users) and to purify the tiny amounts of breakdown products that occur when insulin (either natural or synthetically produced and administered) is metabolised in the body. In particular, they examined at ‘chemical signatures’ left by the sequences of amino acids, which are different in natural insulin and most synthetic types of insulin, and then analysed these signatures using a technique known as mass spectrometry (MS).

The World Anti Doping Agency (WADA) is currently seeking a test for insulin abuse based on this technique and so far, research in this area suggests that the technique of looking at MS signatures can discriminate metabolites of lantus insulin (a long-acting synthetic insulin) from naturally produced human insulin. However, this method doesn’t seem to work for the urine samples from diabetic patients who have been treated with recombinant human insulin or Levemir, two other commercially available long-acting insulins. This is obviously a major drawback when trying to establish a reliable test to detect insulin abuse.

However, what the German team discovered was that when they compared the ratio of a particular degradation product of the synthetic insulins to naturally produced insulin, the ratio was elevated in all diabetic patients treated with any of the types of synthetically produced insulin. This would therefore make the test suitable for the detection of artificial insulins of all types and as such could make life very difficult for would-be insulin cheats in the future. WADA is currently examining these results with a view to introducing an insulin doping test in the near future.
Anal Chem 2007; 79(6):2518-2524

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