The Genetics of Diabetes

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The Genetics of Diabetes

Why do I have diabetes? Many people with diabetes ask this question at some point. With type 1 diabetes, your immune system causes your pancreas to stop producing insulin. If you have type 2 diabetes, either you do not produce enough insulin, or your body is not able to use the insulin that you do produce.

With type 1 and type 2 diabetes, you are born with a predisposition to the disease, and something in your environment triggers it. This trigger can come from a virus or infection, your diet, lifestyle, or a group of factors.

In 2003, researchers found a gene that makes the body likely to develop type 1 diabetes.1-5 You inherit this gene from your parents. This discovery can help us to develop better tests and treatments for diabetes.

Type 2 diabetes appears to have a stronger genetic basis than type 1. That’s why it is often said that type 2 diabetes runs in families. The probability of children getting diabetes depends on whether the father, and mother have the condition, and when they developed it. If both parents have diabetes, the children have a 1 in 2 chance of developing diabetes, too.

However, just because your parents have diabetes or you carry the gene that can lead to it doesn’t guarantee you will get diabetes. For example, look at identical twins: they have the exact same genes. When one twin has type 1 diabetes, the other twin only gets it half the time. When one twin has type 2 diabetes, the other twin's risk is about 3 in 4.

You may be predisposed to get diabetes for many years before ever developing the condition. In fact, the majority of people who are at risk for diabetes do not develop it. So why do some people get diabetes and others don’t? Again, the answer is outside influences — what you eat, how and where you live, and other elements can play a role.

A proper diet starts at birth: breast-fed babies and those who don’t eat solid foods until they are older are less likely to develop diabetes. A larger factor, though, is our lifestyle. In general, Americans do not exercise enough. We also eat too much fat and not enough fiber. That’s why type 2 diabetes is often seen in overweight adults.

Cold weather also plays a role in developing diabetes. Type 1 diabetes develops more often in winter than summer and is more common in colder climates. Viruses may also initiate it. While most people may only have a mild reaction to a virus, for some people it can lead to the development of type 1 diabetes.

Scientists are still learning about the genetic and environmental risk factors linked to diabetes. If you would like to read more about the genetics of diabetes, the National Institutes of Health has published a free online book at www.ncbi.nlm.nih.gov/books. The American Diabetes Association website at www.diabetes.org and the Juvenile Diabetes Research Foundation website at www.jdrf.org have a lot of information. Your doctor can also answer your questions.

References

1. Noble, J. A., et al. (1996). The role of HLA class II genes in insulin-dependent diabetes mellitus: molecular analysis of 180 Caucasian, multiplex families. Am J Hum Genet, 59, 1134-1148.

2. Dorman, J., et al., (1999). Risk Factors for Insulin-Dependent Diabetes. In (Ed. 2nd), Diabetes in America (pp. 165-178). Bethesda, MD: National Diabetes Data Group, NIH.

3. Dubois-Laforgue, D., et al. (1997). Insulin-dependent diabetes mellitus in non-DR3/non-DR4 subjects. Hum Immunol, 57, 104-109.

4. Owerbach, D. and Gabbay, K. H. (1993). Localization of a type I diabetes susceptibility locus to the variable tandem repeat region flanking the insulin gene. Diabetes, 42, 1708-1714.

5. Bennett, S. T., et al. (1995). Susceptibility to human type 1 diabetes at IDDM2 is determined by tandem repeat variation at the insulin gene minisatellite locus [see comments]. Nat Genet, 9, 284-292.