Diabetes: A Unit Study

The story of insulin goes back to 1869, when Paul Langerhans studied the pancreas under the microscope. As he examined the organ, he noticed that it was not uniform; clumps of a unique kind of tissue were scattered throughout. Langerhans was intrigued, but puzzled. What could the clumps in the pancreas be?

Paul Langerhans’s son Archibald continued his work, and eventually proposed a theory that the clumps, called “islets of Langerhans” in Paul’s honor, might have a role in digestion. Other researchers investigated. Slowly but surely it became apparent that Archibald’s theory was correct. What was more, by 1901 it was proved that something in the islets of Langerhans prevented diabetes, then a fatal disease.

Unfortunately, World War I interfered with the efforts of scientists to cure diabetes by somehow extracting and using the mysterious substance produced by the islets of Langerhans. In 1920, however, Frederick Banting came up with an idea. As a surgeon, he thought that by tying off certain arteries to the pancreas of a dog he could cause the organ to atrophy, leaving only the islets of Langerhans intact and creating a pure source of what he called “isletin.” His experiment was successful. He extracted isletin, or insulin, from the islets of several dogs on July 27, 1921 and used it to treat another dog that had had its pancreas removed. The dog survived with the aid of regular insulin treatments.

Of course, if insulin was going to be used to treat humans with diabetes, there had to be a reliable supply. The dogs used in the laboratory were not sufficient. Further experimentation demonstrated that a good supply would be fetal calf pancreases. Now the real test would be to try insulin on a human.

On January 11, 1922, Leonard Thompson was selected as the first patient. The 14-year-old Canadian lay dying in a hospital, but Banting and his assistant Charles Best had high hopes for their insulin. To their dismay, however, the extract proved to be impure. Thompson experienced a severe allergic reaction.

During the next 12 days, biochemist James Collip threw his energy into improving Banting’s method of extracting insulin. On January 23, he felt that he had perfected the procedure enough to make a second attempt at saving young Thompson. The experiment worked. Thompson recovered.

More patients were treated with insulin over the course of the year, and it became obvious that insulin would be an effective remedy for diabetes. Bovine insulin was first produced commercially in 1923, but researchers were not satisfied. Many wanted to understand insulin better, and others were interested in developing a synthetic source. Impurities frequently contaminated animal-derived insulin and caused allergic reactions in the patient. Molecular biologist Frederick Sanger studied insulin throughout the 1940s and early 1950s and finally succeeded in discovering its structure, making insulin manufacture a possibility.

Synthetic insulin was produced by several researchers in the 1960s, but the genetically engineered insulin used today was first made in 1978 by inserting human DNA into E. coli cells. The biosynthetic “human” insulin produced by the genetically modified E. coli bacteria became commercially available in 1982, and is now the only type of insulin available to human patients. (Veterinarians still treat pets with natural swine insulin.)

How Insulin Works

Insulin is the protein which regulates the body’s blood glucose levels. Normally, the pancreas detects increased levels of glucose in the blood after a meal and responds by releasing insulin. The insulin then triggers special transporter proteins, particularly in the membranes of fat and muscle cells, to take glucose out of the blood stream and carry it into the cells, where it can be used for energy. As glucose is removed from the blood, the pancreas senses that there is no need to release further insulin. Both glucose and insulin stabilize at their pre-meal levels.

However, insulin has more far-reaching effects on the body than this simple summary would suggest. Insulin is involved in a number of critical processes:

DNA replication.
Amino acid and potassium absorption.
Regulation of blood flow.
Maintenance of the central nervous system.
Regulation of stomach secretions.
Regulation of renal function.

Little wonder, then, that diabetes can have such serious implications.

Diabetes

Diabetes mellitus is a broad term used to describe any condition in which blood glucose tends to remain at abnormally high levels. Different types of diabetes have different causes, although the result is essentially the same. Type 1 diabetes usually occurs at a young age, when the autoimmune system destroys the insulin-producing cells of the pancreas, leaving the patient unable to produce any insulin. Patients with type 2 diabetes can produce their own insulin, but either do not produce enough or cannot use it efficiently, often because their body cells have become resistant to the influence of insulin. Gestational diabetes begins during pregnancy and is also due to insulin resistance, in this case because of hormonal changes. The underlying cause of all types of diabetes is a combination of genetic and environmental (age, weight, activity level, etc.) factors.

Symptoms of diabetes include:

Fatigue.
Irritability.
Slow-healing sores.
Frequent infections.
Blurred vision.
Pain, tingling, or numbness in hands and feet.
Extreme hunger.
Weight loss.
Thirst.
Frequent urination.

Unfortunately, people can have elevated blood glucose levels without showing any of these symptoms. This is particularly common with gestational diabetes and prediabetes, a state of high glucose that can lead to type 2 diabetes if left unchecked. Blood testing is a more reliable way to diagnose diabetes.

Over time, diabetes damages all of the body systems, directly or indirectly leading to many complications:

Alzheimer’s disease.
Skin disorders.
Blindness.
Hearing loss.
High cholesterol.
High blood pressure.
Amputations due to impaired circulation.
Heart attack.
Stroke.
Nerve damage.
Kidney disease.

Gestational diabetes can cause additional problems. For instance, it can cause the baby to grow too large while still in the womb, leading to dangerous complications at the time of delivery. Also, a baby whose mother suffers from gestational diabetes may have hypoglycemia (dangerously low blood glucose levels) at the time of birth and type 2 diabetes later on in life.

Treating Diabetes

While insulin is a proven treatment for diabetes, administering it at the right time and in the right dose is not always easy. A slight change in activity or food intake changes the amount of insulin that is needed, which makes frequent glucose monitoring necessary. To make things a little easier, two types of insulin are available: a long-acting type to keep blood glucose levels steady throughout the day and a rapid-acting type to help the body absorb the sudden boost of glucose provided by a meal.

Not all diabetics take insulin. People with prediabetes or sometimes even type 2 diabetes opt to take other medications that are easier to manage. These medications work in a variety of different ways, from increasing the body’s insulin production to making the cells more responsive to existing insulin.

Sometimes a lifestyle change is all that is necessary to control high blood glucose levels. Prediabetes patients, in particular, have an opportunity to restore their health naturally, but even people diagnosed with type 2 diabetes can put off the need to take insulin for a time by improving their diet and exercising regularly. Special diets are not necessary for diabetics; in fact, studies suggest that some sugar substitutes can have unpleasant side effects while still increasing blood glucose levels. Most diabetics are advised to eat more fruits, vegetables, and whole grains, and to eat starches and sweets in moderation. Plenty of aerobic exercise is recommended, because this type of activity can help cells remove excess glucose from the blood. A typical recommendation is 30 minutes of aerobic exercise a day for most days of the week.