Some Special Cells

Insulin comes from islet cells—unless they don't work! Here's what these cells do, and how scientists are finding ways to fix them when they're broken.

An organ about the size of your fist sits tucked behind your stomach. It's called a pancreas (pronounced PAN-kree-us), and it has a whole lot to do with diabetes.

The pancreas contains islet (EYE-let) cells—several million of them. Their purpose is to make insulin in the right amount at the right time, like when you've eaten, so you can have the energy you need. In people with Type I diabetes, the disease has destroyed their islet cells, or most of them. That's why they have to get insulin elsewhere and inject it.

How Islet Cells Are Supposed to Work

A German man named Paul Langerhans (langer rhymes with "hanger," plus "hans") discovered islet cells in 1869 and named them "islets of Langerhans." Islet means "little island," and that is what clusters of islets look like in the pancreas if you look at them through a microscope.

Islets are made up mostly of beta (BAY-duh) cells; these are the cells that make insulin. There are also a few alpha (AL-fuh) cells and delta cells, which play other important roles in changing meals to energy.

Islet cells are unbelievably complicated! They do their job in about the same way that a heart beats or nerves send impulses: with chemical and electrical signals, all interacting at lightning speed to make insulin on the spot.

And they're smart! they have electrical "channels" that sense when blood sugar is rising, and then let in ONLY the chemical that triggers insulin production.

Replacing Islets That Don't Work

Islet cells are also very delicate, which makes them hard to transplant. The idea of transplantation is to remove healthy islets from the pancreas of a donor (a person who has just died) and to place them in the body of a person with diabetes, where they begin to make insulin for that person.

Islet transplants have been done, but it still has not become routine. For one thing, the islets can easily be injured or destroyed when they're taken from the donor's pancreas. For another, people who receive the islets automatically try to "reject" them, or destroy them, just as they would a transplanted kidney or heart, or anything strange in the body. So they have to take really strong antirejection medicine, which can make them sick - maybe sicker than they ever were before the transplant. Finally, there just aren't enough donor islets available to give to all the people who have diabetes.

Trying to Cure Diabetes with Islets

Doctors are doing a lot to make islet transplants easier. Using chemicals, they have found a gentler way to remove the islets from a donor's pancreas. They are finding ways to enclose the transplanted islets in a coating or capsule for protection against rejection. They are also testing places in the patient's body to "hide" the islets—a kidney or a blood vessel may be a better spot than the pancreas. And they are working on ways to change the makeup of the islets just a bit so the patient's body doesn't consider them strange.

To increase the number of islets available for transplants, doctors are turning to animals. Insulin made by the islets of pigs is a lot like human insulin, and there are plenty of pig islets available. But even if the insulin is similar, the human body tries extra hard to reject anything transplanted from animals. So, unless the islets can be protected somehow, the person receiving the pig islets would still have to take antirejection medicine.

It's even possible that "fake" islets will be transplanted someday. These islets would start out as another kind of cell—one that is plentiful and sturdy—but then be changed so they make insulin.

It's exciting to know that with these new ideas for transplanting, the "little islands" that make insulin will help a lot of people with diabetes in the future.

By Melissa Culverwell
Published in Countdown For Kids Fall 1997
Posted February 2000
Updated October 2003