Is Diabetes Genetic?

Genetic Risks, Testing, and Prevention

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If you or someone in your family has developed diabetes, you might be wondering if it is genetic. There are different types of diabetes, all of which have specific risk factors contributing to the cause.

If you have a mother, father, brother, or sister with diabetes, you are at increased risk of developing it compared to someone who doesn't. But diabetes isn't caused by genetics alone, and having a relative with the disease doesn't mean you will absolutely get it.

In some instances, such as type 2 diabetes, lifestyle plays a role, and early screening can prevent or delay disease development. Also, identifying genes may help researchers and physicians predict a diabetes diagnosis and develop individualized treatment plans that are optimal for glucose control and modifying disease progression.

Learn more about the role of genetics in developing diabetes, screening, steps you can take to prevent or delay certain types of diabetes, and how environmental elements may implicate different types of diabetes.

Role of Genetics in Diabetes

Certain genetic predispositions make developing diabetes more likely. But just because you have genetic risk factors does not mean you will absolutely develop diabetes.

Over time, researchers have discovered a relationship between certain genes and the development of diabetes. It is estimated that types 1 and 2 diabetes have complex genetic etiologies, with over 40 and 90 genes/loci respectively implicated that interact with environmental/lifestyle factors.

The genes that have been identified have diverse functions and duties which can affect blood sugar control. Such functions include influencing the expression of other genes, controlling the release of insulin, pumping glucose into cells, and speeding up the breakdown of glucose.

But, in addition to genes, something in the environment must trigger diabetes to become active. For example, in children with a genetic predisposition to type 1 diabetes, researchers have found that viruses, cold weather, early food introduction, and whether they are breastfed are all variables that may play a role in developing type 1 diabetes.

Type 1 Diabetes

Type 1 diabetes is an autoimmune disease in which the body mistakenly attacks the beta cells of the pancreas, resulting in a person relying on insulin in the form of infusion or injection to live. It is estimated that 1.6 million Americans are living with type 1 diabetes.

People genetically predisposed to type 1 diabetes are at increased risk of developing it, but that does not mean they will absolutely get it.

The American Diabetes Association states, "If you are a man with type 1 diabetes, the odds of your child developing diabetes are 1 in 17. If you are a woman with type 1 diabetes and your child was born before you were 25, your child's risk is 1 in 25; if your child was born after you turned 25, your child's risk is 1 in 100.

Researchers have also found that among first-degree relatives, siblings of those with type 1 diabetes are at higher risk than offspring of parents (both fathers and mothers) that have type 1 diabetes.

According to the American Diabetes Association, most White people with type 1 diabetes have genes called HLA-DR3 or HLA-DR4, which are linked to autoimmune disease. Suspect genes in other ethnic groups may put people at increased risk.

For example, scientists believe that the HLA-DR9 gene may put Black people at risk, and the HLA-DR9 gene may put Japanese people at risk. While certain genes are more common predictors of type 1 diabetes, about 40 gene markers have been confirmed.

Genetic predisposition alone is not enough to cause type 1 diabetes. And some people can develop type 1 diabetes even though no one in their family has it. It is estimated that 85% of the people diagnosed with type 1 diabetes do not have a family history of the disease.

Type 2 Diabetes

Type 2 diabetes is characterized by insulin resistance and progressive loss of beta cell function (the beta cells are cells found in the pancreas that are responsible for making insulin) which can lead to elevated blood sugars.

Many people who have type 2 diabetes may also have other underlying health conditions, such as elevated blood pressure, cholesterol, and excess weight in the abdominal area. In the past, type 2 diabetes was often referred to as adult diabetes, but we know now that this disease can also affect children.

The genetic component of type 2 diabetes is complex and continues to evolve. There are many genes that have been identified in people with type 2 diabetes.

Some genes are related to insulin resistance, while others are related to beta cell function. Scientists continue to research genes involved in the development of type 2 diabetes and their role in disease progression and treatment. Studies have shown a wide range of variability, 20% to 80%, for the heritability of type 2 diabetes.

The lifetime risk of developing type 2 diabetes is 40% for individuals who have one parent with type 2 diabetes and 70% if both parents are affected. People with a family history from first-degree relatives are also estimated to be three times more likely to develop the disease.

But genetic factors are not the only risk. Environmental factors, behavioral factors, and shared environment can also impact risk.

The American Diabetes Association points out that while type 2 diabetes has a stronger link to family history than type 1 diabetes, environmental and behavioral factors also play a role, and intervention strategies can help to prevent or delay a diabetes diagnosis.

Gestational Diabetes

Gestational diabetes occurs during pregnancy when blood glucose levels become elevated. The placenta provides the baby with nutrients to grow and thrive. It also produces a variety of hormones during pregnancy.

Some of these hormones block the effect of insulin and can make after-meal blood sugars harder to control. This usually happens around 20 to 24 weeks of pregnancy, which is why people are screened for gestational diabetes at this time.

Normally, the pancreas will produce more insulin to compensate for hormonal insulin resistance. Some people cannot keep up with insulin production, which results in elevated blood sugar and ends with a gestational diabetes diagnosis. Most people will have no symptoms.

Gestational diabetes is thought to be caused by a combination of genetic and environmental risk factors. Genetic predisposition has been suggested since it clusters in families.

Several genes have been identified in those people with gestational diabetes. There also seems to be a correlation between gestational diabetes and genes for maturity-onset diabetes mellitus of the young (MODY).

Many people diagnosed with gestational diabetes have a close family member such as a parent or sibling with the disease or another form of diabetes, such as type 2 diabetes.

However, it is important to note that having a genetic predisposition doesn't mean you will automatically get gestational diabetes. Other risk factors include gestational age, weight, activity level, diet, previous pregnancies, and smoking, to name a few. Maintaining adequate blood sugar control is important for the health of the mother and baby.

Genetic Testing

Genetic testing for diabetes is complicated because in certain types of diabetes, such as type 2 diabetes, small variants of several different types of genes can lead to a diagnosis.

Genetic testing is valuable and can help with effective treatment when used to identify certain monogenic (mutation in a single gene) forms of diabetes, such as neonatal diabetes and MODY. In these instances, genetic testing is important because people with MODY are often misdiagnosed.

Physicians often recommend genetic testing when a diabetes diagnosis appears to be atypical. For example, a person who is around age 25, presents with abnormal blood sugars, and does not have any typical risk factors for type 1 or type 2 diabetes, may have MODY.

Genetic diagnosis of MODY additionally allows for the identification of at-risk first-degree family members, who have a 50% chance of inheriting a gene mutation.

However, one of the problems is that sometimes insurance denies coverage for genetic testing even when people fit the criteria, which can cause physicians to miss a MODY diagnosis. Researchers are continually trying to find ways to make genetic testing more cost-effective.

Certain genes and antibodies can help predict a type 1 diabetes diagnosis. If you suspect that you or your child are at increased risk of developing type 1 diabetes, you might be eligible for a risk screening offered through TrialNet Pathway to Prevention Study.

This risk screening is free to relatives of people with type 1 diabetes and uses a blood test to detect risk before symptoms appear. People found to be in the early stages of developing type 1 diabetes may also be eligible for the prevention study. Ask your healthcare provider whether genetic testing is available and how helpful it is in determining if you will get diabetes.

Currently, researchers do not feel that genetic testing is significant in the diagnosis of type 2 diabetes. Because there are so many variants of genes and subtypes of type 2 diabetes, they feel as though better methods and more research need to be done in this area before putting it to practical use.

People who are pregnant are screened for gestational diabetes between 20 to 24 weeks. However, as with type 2 diabetes, genetic testing is not yet clinically useful in polygenic gestational diabetes due to the relatively small amount of risk explained by known genetic variants.

On the other hand, researchers do find value in genetic testing for monogenic forms, particularly MODY, to determine treatment and pregnancy management.

Can You Reduce Your Risk?

While family history does increase your risk, simply having a genetic predisposition doesn't ensure you will develop diabetes. If you have a family history of gestational diabetes or type 2 diabetes, there are ways to reduce your risk of developing the disease.

Maintain a healthy weight or losing weight if you are overweight, particularly in the abdominal area, to reduce risk. Even modest weight reduction, about 5% to 10% weight loss, can reduce your risk. For people who are pregnant, gaining weight slowly rather than excessively can help to prevent gestational diabetes.

Stay active. Aim to exercise at least 150 minutes per week and avoid sitting for extending periods of time.

Eat more plants, such as fruits, vegetables, legumes, nuts, seeds, and whole grains. This has also been associated with a reduced risk of developing type 2 diabetes.

Health maintenance and regular checkups are important. If you've recently gained weight or are feeling very sluggish and tired, you may be experiencing high blood sugar, which is characterized by insulin resistance.

Screening

Because type 2 diabetes often takes years to develop, people can be walking around with impaired glucose tolerance (insulin resistance) or prediabetes for years without knowing it. If you catch this condition early, you may be able to prevent or delay diabetes from occurring. Screening is recommended if you have any of the following risk factors:

  • Over age 45: If your results are normal, testing should be repeated at least at a minimum of three-year intervals, with consideration of more frequent testing depending on initial results (those with prediabetes should be tested yearly).
  • High BMI: A BMI of more than 25 kg/m2 or a waist circumference of more than 40 inches in men or 35 inches in women is a risk factor. The BMI cut-off for Asian-Americans is lower (23 kg/m2).
  • Belong to a high-risk population: Populations with a higher risk of prediabetes include Black Americans, Hispanic/Latinx Americans, Native Americans, Alaska Natives, Asian Americans, and Pacific Islanders.
  • Family history: This includes having a parent or sibling with diabetes.
  • Gestational diabetes: A history of gestational diabetes or having given birth to a baby weighing more than 9 pounds are risk factors.
  • Lifestyle: Typically, a physically inactive lifestyle is a risk factor.
  • Hypertension: This is defined as a blood pressure that's equal to or greater than 140/90 mmHg or taking therapy for hypertension.
  • High fat and cholesterol levels: If you have low levels of high-density lipoprotein (HDL) cholesterol or high levels of triglycerides, you have a higher risk.
  • Predisposing conditions: These include acanthosis nigricans, nonalcoholic steatohepatitis, polycystic ovary syndrome, and atherosclerotic cardiovascular disease.
  • Medications: Atypical antipsychotics or glucocorticoids increase risk.

There are some noninvasive tests that can alert you if you are at increased risk of developing type 2 diabetes. These include hemoglobin A1C, blood pressure, cholesterol, and triglycerides.

Other Things to Consider

Sometimes people who have a family history of gestational diabetes can develop diabetes during pregnancy despite their efforts to keep weight gain within a healthy range, exercise, and eating a fiber-rich diet. Do not beat yourself up if this happens.

Pregnancy hormones and insulin resistance (which is typical during pregnancy) can make controlling blood sugar in pregnancy difficult for some people with genetic risk. Your medical team will help you reach your blood sugar goals during pregnancy to make sure that you and your baby are healthy and thriving.

Once you have delivered your baby, your blood sugars should go back to normal. But it's still important to continue to eat a well-balanced diet, maintain a healthy weight, and exercise; these steps can help reduce your risk of developing type 2 diabetes later in life.

Although type 1 diabetes cannot be prevented or cured, if you are genetically predisposed to type 1 diabetes, regular vaccinations and wellness visits will be important.

There is no vaccine to prevent type 1 diabetes, but some research suggests that viruses can trigger type 1 diabetes in people that are predisposed. Therefore, preventing catching these viruses may reduce the risk of developing diabetes.

Understanding the warning signs of type 1 diabetes will also help prevent a dangerous situation like diabetic ketoacidosis. Although there is no proven cure, scientists continue to make headway in developing better ways to manage the disease. Additionally, organizations will continue to invest time into researching and developing ways to cure this disease.

A Word From Verywell

There is a genetic component to the development of diabetes, but it's not the only element. Lifestyle factors, environmental triggers, and other health conditions can also play a role in developing the disease.

There are many different types of diabetes, so your risk depends on what type of diabetes you are genetically predisposed to. If you have concerns about your family history of diabetes, be sure to take it up with your medical team.

Genetic testing may not be helpful in certain instances; however, you may be screened for the disease. You will be educated on your individual risk, steps to take to prevent or delay it (if possible), and coping strategies.

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