Diabetes: Once a death sentence, Scottish scientist's work on insulin turned it into a treatable condition – Professor Mirela Delibegovic

Since the discovery of insulin in 1921, it has saved millions of lives globally. From its first use in January 1922, it has transformed diabetes from a death sentence to a treatable chronic condition.

The breakthrough was performed by John Macleod, a University of Aberdeen medical graduate and expert in carbohydrate metabolism and diabetes, assisted by Frederick Banting, Charles Best and James Collip.

Macleod and Banting were awarded the Nobel Prize in Physiology or Medicine for the discovery of insulin. However, the story was not without controversy as Banting felt Macleod was undeserving of the accolade, and for decades Macleod was airbrushed from the history books.

The story of diabetes is a long one dating back to around 1550 BC, with an ancient Egyptian papyrus mentioning a rare disease that makes patients lose weight rapidly and urinate frequently.

Only in 1889 was it first linked to pancreatic function by research charting the removal of a dog’s pancreas and subsequent onset of diabetes. It proposed the pancreas may produce an internal secretion to regulate blood sugar levels (only later discovered to contain insulin).

In 1906, two assistants at the University of Aberdeen, John Rennie and Thomas Fraser, used fish pancreas extracts from Aberdeen fish market to treat the patients. Unfortunately, the boiled or raw extracts fed to the patients resulted in no improvements. The following year, a German physician used injections of pancreas extract which, despite not being well tolerated and causing vomiting, resulted in some clinical benefit.

These experiments all led Macleod to make the final discovery. After moving to Aberdeen aged seven, he attended Aberdeen Grammar School then the University of Aberdeen where he graduated with honourable distinction in 1898. After doing some outstanding research, he was offered a chair in physiology in Cleveland, Ohio, aged 26, and then joined the University of Toronto.

A woman with diabetes measures the concentration of sugar in her blood (Picture: Franck Fife/AFP via Getty Images)

While there, he was approached by Frederick Banting with the idea to self-contain a dog’s pancreas while it creates secretions then use it to lower blood sugar levels in another dog. Banting seemed unaware this had been tried before, yet Macleod supported him to carry out the experiment.

After months of work, an extract was gathered but it was still not pure. Macleod then took the momentous step to instruct their biochemist, James Collip, to purify the extract using alcohol, creating the first ever recorded pure insulin.

Without that pure extract, there would have been no miracle cure.

Unfortunately, in the immortal story, Macleod did not receive public acclaim despite his reputation. He returned to the University of Aberdeen where he remained, making several more significant contributions, until his retirement.

Today, researchers and academics at Scottish universities continue to have major roles in discovering new treatments for diabetes. Their work keeps the achievement of John Macleod alive and creates a sense of anticipation about the next scientific breakthrough made at the hands of a Scot.

Professor Mirela Delibegovic is chair in diabetes physiology and signalling at the School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, and a fellow of the Royal Society of Edinburgh. The RSE is Scotland's National Academy, which brings great minds together to contribute to the social, cultural and economic well-being of Scotland. Find out more at rse.org.uk and @RoyalSocEd.