Unlike some traits, diabetes does not seem to be inherited in a simple pattern. Yet when one twin has type 1 diabetes, the other gets the disease at most …
Genetics of Diabetes
Youve probably wondered how you got diabetes You may worry that your children will get it too Unlike some traits, diabetes does not seem to be inherited in a simple pattern Yet clearly, some people are born more likely to get diabetes than others
What leads to diabetes?
Type 1 and type 2 diabetes have different causes Yet two factors are important in both First, you must inherit a predisposition to the disease Second, something in your environment must trigger diabetes Genes alone are not enough One proof of this is identical twins Identical twins have identical genes Yet when one twin has type 1 diabetes, the other gets the disease at most only half the time When one twin has type 2 diabetes, the others risk is at most 3 in 4
Type 1 diabetes
In most cases of type 1 diabetes, people need to inherit risk factors from both parents We think these factors must be more common in whites because whites have the highest rate of type 1 diabetes Because most people who are at risk do not get diabetes, researchers want to find out what the environmental triggers are One trigger might be related to cold weather Type 1 diabetes develops more often in winter than summer
and is more common in places with cold climates Another trigger might be viruses Perhaps a virus that has only mild effects on most people triggers type 1 diabetes in others Early diet may also play a role Type 1 diabetes is less common in people who were breastfed and in those who first ate solid foods at later ages In many people, the development of type 1 diabetes seems to take many years In experiments that followed relatives of people with type 1 diabetes, researchers found that most of those who later got diabetes had certain autoantibodies in their blood for years before Antibodies are proteins that destroy bacteria or viruses Autoantibodies are antibodies gone bad, which attack the bodys own tissues
Type 2 diabetes
Type 2 diabetes has a stronger genetic basis than type 1, yet it also depends more on environmental factors Sound confusing? What happens is that a family history of type 2 diabetes is one of the strongest risk factors for getting the disease but it only seems to matter in people living a Western lifestyle
Americans and Europeans eat too much fat and too little carbohydrate and fiber, and they get too little exercise Type 2 diabetes is common in people with
these habits The ethnic groups in the United States with the highest risk are African Americans, Mexican Americans, and Pima Indians In contrast, people who live in areas that have not become Westernized tend not to get type 2 diabetes, no matter how high their genetic risk Obesity is a strong risk factor for type 2 diabetes Obesity is most risky for young people and for people who have been obese for a long time Gestational diabetes is more of a puzzle Women who get diabetes while they are pregnant are more likely to have a family history of diabetes, especially on their mothers side But as in other forms of diabetes, nongenetic factors play a role Older mothers and overweight women are more likely to get gestational diabetes
Type 1 diabetes: your childs risk
In general, if you are a man with type 1 diabetes, the odds of your child getting diabetes are 1 in 17 If you are a woman with type 1 diabetes and your child was born before you were 25, your childs risk is 1 in 25; if your child was born after you turned 25, your childs risk is 1 in 100 Your childs risk is doubled if you developed diabetes before age 11 If both you and your partner have type 1 diabetes, the risk is between
1 in 10 and 1 in 4 There is an exception to these numbers About 1 in every 7 people with type 1 diabetes has a condition called type 2 polyglandular autoimmune syndrome In addition to having diabetes, these people also have thyroid disease and a poorly working adrenal gland Some also have other immune system disorders If you have this syndrome, your childs risk of getting the syndrome including type 1 diabetes is 1 in 2 Researchers are learning how to predict a persons odds of getting diabetes For example, most whites with type 1 diabetes have genes called HLA-DR3 or HLA-DR4 If you and your child are white and share these genes, your childs risk is higher Suspect genes in other ethnic groups are less well studied The HLA-DR7 gene may put African Americans at risk, and the HLA-DR9 gene may put Japanese at risk Other tests can also make your childs risk clearer A special test that tells how the body responds to glucose can tell which school-aged children are most at risk Another more expensive test can be done for children who have siblings with type 1 diabetes This test measures antibodies to insulin, to islet cells in the pancreas, or to an enzyme called glutamic acid decarboxylase
High levels can indicate that a child has a higher risk of developing type 1 diabetes
Type 2 diabetes: your childs risk
Type 2 diabetes runs in families In part, this tendency is due to children learning bad habits eating
a poor diet, not exercising–from their parents But there is also a genetic basis In general, if you have type 2 diabetes, the risk of your child getting diabetes is 1 in 7 if you were diagnosed before age 50 and 1 in 13 if you were diagnosed after age 50 Some scientists believe that a childs risk is greater when the parent with type 2 diabetes is the mother If both you and your partner have type 2 diabetes, your childs risk is about 1 in 2 People with certain rare types of type 2 diabetes have different risks If you have the rare form called maturity-onset diabetes of the young MODY, your child has almost a 1-in-2 chance of getting it, too
What is At Risk?
Risk estimates are just scientists best guesses They can be wrong Risk estimates deal in probabilities, not absolutes For example, the chance of getting a royal flush in poker is 1 in 650,000, and the odds of two pairs are 1 in 20 Knowing these odds influences how you bet But it does not allow you to predict
when the next royal flush will be dealt Similarly, you may get a disease despite having a low risk, or you may not get a disease despite a high risk For example, smokers have a high risk of lung cancer, but some smokers never get cancer These factors mean that your children can still get diabetes even though their risk is low The average American has a 1-in-100 chance of getting type 1 diabetes and a 1-in-9 chance of type 2 diabetes Even if your childs risk is no higher than anyone elses, he or she still could get diabetes
This fact sheet was adapted from the American Diabetes Association ADA For more information, go to wwwdiabetesorg or contact 1-800-DIABETES
Source:unca.edu
