What are the Culprits? Type 1 Diabetes

Diabetes Survival Guide: Understanding the Facts About Diagnosis, Treatment, and Prevention
by Stanley Mirsky, M.D., Joan Rattner Heilman

(Page 4 of 6)

What are the Culprits?

The genetics of type 2 diabetes turns out to be very complicated, and the disease is thought to be caused, along with excess weight and a faulty lifestyle, by a variety of genes. A major development, reported in 2005, was the discovery of a variant gene - designated TCF7L2 - that increases the risk of diabetes significantly and is thought to be carried by more than a third of the American population. According to the Iceland-based research team that identified it, people with one copy of the gene are estimated to have a 45 percent greater risk of type 2, while those who have inherited two copies, one from each parent, are 141 percent more likely to develop the disease.

The immediate practical effect of this discovery is that it may lead to diagnostic tests that can identify people with this gene, inspiring them to watch their weight, get plenty of exercise, and eat healthy diets.

Similar work goes on in many places. One study at the University of Texas Southwestern Medical Center has shown that a variation in the gene ENPPI is much more common in people with type 2 diabetes and those at greater risk for the disease. It may explain why certain ethnic groups have a higher risk even when they are thin. Changes in the gene PTPN1 are another possibility that may affect the production of a protein important in insulin activity. Variations in HNF4A, a gene that seems to act as a master regulator of insulin-making cells, seem to be much more common in type 2 diabetes. And Dr. C. Ronald Kahn of the Joslin Clinic has identified genes specifically involving PI3K that are defective in some type 2 diabetics.

What's more, type 2s are almost always overweight. The vast majority of adult diabetics are too heavy or even obese. Many overweight type 2s can lose their diabetes by losing weight. Sometimes a loss of even a few pounds is sufficient to accomplish this miracle because now you may produce enough of your own insulin to keep your blood sugar normal or decrease the visceral fat around your abdomen that interferes with the action of insulin.

In controlled studies, it has been discovered that regular, vigorous exercise can lower or even eliminate the need for pills or injections.

Not all type 2 diabetes, however, is the result of overweight in a predisposed person. Sometimes it's simply the result of an inefficient pancreas. The beta cells become unable to sense the sugar molecules and so can't respond accurately to their presence; or they simply cannot produce enough insulin. In these cases, losing weight won't help but eating correctly and enough exercising will, perhaps supplemented by oral agents or insulin.

Type 1 (Insulin-Dependent Diabetes Mellitus, Or Iddm)

Type 1 diabetes, once known as juvenile diabetes, is quite another story and may even be another disease with a similar outcome. There are comparatively few type 1s - less than 10 percent of the total number of diabetics.

Type 1 can strike at any age, and about 15 to 20 percent of IDDMs are adults when they are diagnosed. But it happens for most people before they are twenty, and most commonly around the ages of eight, twelve, and puberty, when dramatic growth spurts take place. For every 100,000 people in the country, there are 50 diagnosed diabetics under the age of five; there are 150 under age ten; 270 below age fifteen; and 325 per 100,000 population by the age of eighteen.

Type 1 diabetes affects about one million Americans, with about thirteen thousand new cases each year, making it the second largest childhood disease in the U.S. after asthma.

It is now understood to be an autoimmune disease in which a body's germ-fighting defenses mistakenly attack organs and tissues; in this case, the insulin-producing beta cells of the pancreas. Theory today is that the disease is usually triggered by a virus - perhaps a virus that is fairly benign for most people - that sets off an unrelenting immune response in a person who is genetically susceptible, knocking the beta cells permanently out of commission.

This kind of diabetes develops only in children and some adults who carry a very specific genetic make-up.

If you are a type 1, you have a marked insufficiency in the number of beta cells your pancreas possesses and you produce little or no insulin of your own. That means you must take insulin injections to compensate. Except in extremely rare cases, the oral drugs, designed to stimulate production in a pancreas that has the capability to make its own insulin, won't work for you.

Unlike type 2, type 1 diabetes generally shows up very abruptly and dramatically, with unmistakable symptoms - excessive urination and thirst, dramatic weight loss, weakness, irritability. If these symptoms go untreated, they rapidly progress into acidosis (see Chapter 9) and finally coma in only a few days or weeks.

As a type 1, a person with the severest form of diabetes, you probably do not have diabetic parents, though there is a genetic factor here, too, as studies with identical twins have shown. Far from overweight, you are probably very thin and perhaps wan. There is no way for you to lose your symptoms by losing weight and eating sanely. But supplementary insulin, aided by good diet and plenty of exercise, will keep your blood sugar relatively normal.

Copyright © 2006 by Stanley Mirsky. Excerpted by permission of Ballantine Books, a division of Random House, Inc. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.

About the Author

Stanley Mirsky, M.D., is a practicing internist and diabetologist, a past president of the American Diabetes Association of New York State, and a board member of the Joslin Diabetes Center. He was named Endocrinologist of the Year for 2005 by the Mount Sinai School of Medicine. He lives in New York City.

Joan Rattner Heilman is an experienced health writer who has authored hundreds of articles and several books including Estrogen, What Every Woman Should Know: Staying Healthy After 40, and The Complete University Medical Diet. She Lives on Long Island.