Substance X: history of the discovery of insulin

Leonard Thompson was the first human being, a 14-year-old boy, to receive a life-saving insulin injection on January 23, 1922. Leonard was diagnosed with nowadays type I diabetes, fatal in a short time. He had already received a first injection on the 11th with a limited effect.

But the image of a little boy getting life back in his cheeks after an injection in a Toronto hospital is perhaps one of the most magical moments in the history of science. It represents the tenacity of a team of researchers with Frederick Gates Banting at the helm. This story begins the way it ends: saving lives.

Previous evidence

At the time, Fred Banting was a professor of pancreatic physiology in Toronto, a job he performed in addition to his practice, having returned from military service in World War I. In the late 1920s, he fell into his problems. At the end of 1920, he came across a copy of the journal Surgery, Gynecology & Obstetrics, where he read an article by Moses Barron on a case of pancreatic lithiasis, characterized by stones in the pancreatic tube that connects to the gut. The paper described a human autopsy with an atrophy of the pancreatic juice-producing glands –the acinus–, while the Langerhans islets cells still were there. This was similar to what was observed when blocking a pancreatic duct with a ligature.

Russian-born Barron confirmed what his compatriot Sovolev discovered earlier in various animal species, including dogs: when he ligated the pancreatic duct, the enzyme-producing glands atrophied, and the Langerhans islets tissue was exposed. This meant there were two types of tissues with totally different products and actions in the organ. Those are now well known as the endocrine function, the production of insulin –and other hormones– by the islets, and the exocrine function, producing pancreatic juice with digestive enzymes, by the acini.

But at the time, Banting was tossing and turning over the article's conclusions, unable to fall asleep, and wrote: “Diabetes. Ligate the dog's pancreatic duct. Keep the dogs alive until their acini degenerate and islets remain. Try to isolate the internal secretion of these to alleviate glycosuria1”. With this idea in mind, in the summer of 1921, he persuaded Professor John Mcleod in Toronto to lend him a lab, a few dogs, and a student. It happened the student was Charles Bates, so the story says that an early candidate lost his chance at the flip of a coin. James Collip would later join in. Banting, Bates, Mcleod, and Collip thus formed the tetrad that was to change the history of diabetes. But the hard experimental work was done by Banting and Bates.

The experiments

Banting and Bates knew that the pancreas had something to do with diabetes. But was there something in the pancreatic juice that regulated the sugar level? In 1889, Oscar Minowsky in Germany removed a dog's pancreas to see if the animal could live without it. The next day, he observed that a bunch of flies swarmed around the dog's urine, because it was sweet. All attempts by other researchers to extract this hypothetical substance were unsuccessful. 

“Perhaps what is happening is this, Mr. Best,” said Banting (it was only after several days that our work became flatter and then we were Fred and Charley). — “It is possible that when the pancreas is removed from an animal and ground to extract substance X, the digestive enzymes of the organ mix with it and disintegrate it. Perhaps that may have been the cause that has so far prevented finding this substance.”

The young researchers decided to ligate the pancreatic ducts to prevent the digestive enzymes from damaging the substance. They would wait seven to ten weeks for the pancreas to degenerate as a digestive organ. By doing this, there would be no digestive enzymes to destroy Substance X. Finally, they would give the substance to a diabetic dog to test its effectiveness in lowering sugar in blood and urine. But besides, one of the biggest problems was the shortage of dogs. 

When the situation worsened, Banting didn't hesitate to tell Bates, “Start up the Pancreas –the name he had given his Model T Ford– and let's go.” With the help of his indefatigable Pancreas, they would scour the poorer areas of Toronto looking for dogs that owners were willing to sell for one dollar.

One day, after weeks of waiting, they opened the dogs to check the condition of their pancreases. The surprise was that they were still in perfect condition, which meant they hadn't done the ligatures too well. But, by all accounts, Banting was a stubborn man. They took advantage of the fact that Mcleod, the head of the physiology department who had given them the laboratory and the means to carry out the research, had gone on holiday. Mcleod's idea was to surgically transplant the remaining tissue after ligation, which was no small matter. At the end of this second set of experiments, the pancreases degenerated. They had taken another crucial step.

The two researchers extracted the pancreas from one animal, fragmenting it in a mortar previously cooled with Ringer's solution (a type of saline solution). They then froze the mixture, allowing it to thaw slowly before crushing it and passing it through filter paper. At that point, there was a diabetic terrier that was on death's door, so faint that he could not even lift his head. Bates proceeded to inject him with five milliliters of the filtrate. They noticed some improvement in the animal but were not optimistic and analyzed his blood. 

They extracted a few drops from the dog's paw to determine the amount of sugar in his blood concentration. Banting always stood by Bates' side while he did the test, waiting to see if the reagent in the test tube turned dark red or pale pink. They decided every hour. The coloration became paler, indicating that the blood sugar concentration gradually decreased. At that moment, the two researchers experienced the most incredible thrill of their lives: isletin, as they called it, existed, and they could use it as a treatment. Later, the head of the department persuaded them to change the name to insulin.

Injecting young Leonard

They arrived in Toronto a few days earlier with a small amount of insulin they had managed to produce. They were eager to test it on a human being. At Toronto General Hospital, just across the street, they agreed to work with young Leonard Thompson's doctors to try to save his life. Their discovery of insulin in the previous months had given Leonard's doctors faint hope: they knew insulin had the potential to save his life. But Banting and Bates had never tested it on humans before, and they were understandably nervous. They had no more choice but to roll up their sleeves and inject each other. Luckily, nothing more than a tiny swelling.

The injection for Leonard itself was a delicate and complicated procedure: the insulin had to be carefully prepared and measured. They had to give the injection with precision to avoid harming the kid. Banting and Best were confident in their abilities and proceeded with the injection. The results were almost immediate: Leonard's blood sugar levels began to normalize within a few hours, and he started to feel a little better. The two researchers injected a new dose a few days later. His doctors were amazed and continued to give him insulin injections over the next few days.

The boy's recovery was nothing short of miraculous. Within a week, he could eat and drink normally and regained his strength. His doctors marveled at the transformation and knew they had witnessed something extraordinary. The News of Leonard's recovery spread quickly, and soon more physicians ordered insulin for their patients. Banting and Best worked tirelessly to produce more insulin. They eventually managed to scale up production to meet demand thanks to James Collip, who played a crucial role in purifying the aggregate.

The discovery of insulin gave Banting and Mcleod recognition with the Nobel Prize in Medicine in 1923. After their disagreements, Banting shared the prize with his partner, and in response, Mcleod with Collip. Despite this, the research team sold the patent to companies to market it for one dollar. 

The development of scale up and improvement of insulin production processes, later carried on by Eli Lilly in the United States and Novo Nordisk in Denmark, was critical to make it available to the worldwide population.

To know more

1 Glycosuria: a medical term to describe the presence of sugar in the form of glucose in the urine, characteristic of diabetes.

Best, C. (Redacción de J.D. Ratcliff) Historia de la Insulina: Cómo descubrimos la insulina. Condensed from "Today’s Health", American Medical Association.

Jácome A. El descubrimiento de la insulina. En: Pinzón Barco JB, editor. Insulinoterapia: una travesía de principio a fin. Bogotá: Distribuna Editorial Médica; 2020. p. 1-10.