The genetics of diabetes – by Faye Riley

Our DNA is a blueprint for the human body, containing tens of thousands of genes: instructions on how to build and look after it. Changes to the code of those genes can increase the risk of you getting – or even cause – certain conditions. So what about diabetes?

Type 1 diabetes

There are a number of different genes involved in Type 1 diabetes. Changes in these genes don’t ‘give’ you Type 1, but they do increase your chances of developing it. The more high risk genetic changes you have, the more likely you are to develop Type 1 diabetes.

Some of these genetic variations can be passed on through families, but having several high risk changes doesn’t mean you will definitely develop Type 1 diabetes. We know this from studying genetically identical twins, where their DNA code is exactly the same. There are examples of one identical twin developing Type 1, while the other doesn’t. This shows that our risk of Type 1 isn’t solely linked to our genes – there must be other factors involved.

We don’t yet fully understand what causes Type 1 diabetes. Scientists believe that the environment around us is likely to play a role, in combination with these high risk genetic changes. They’re studying different factors right now, such as viral infections, our gut bacteria, and diet, so we can build a clearer picture of how and why Type 1 develops.

Type 2 diabetes

Our genes also play an important role in Type 2 diabetes. There are over 400 genes in which certain changes to the code can bump up your risk of developing Type 2. Just like Type 1 diabetes, some of those changes can be passed down through families, and having more of those high risk changes will increase the likelihood of you developing the condition.

But having these high risk genetic changes doesn’t mean you will definitely develop Type 2 diabetes. We know that there are other factors that contribute to our risk of developing Type 2 diabetes, such as our weight and blood pressure. Unlike Type 1 diabetes, we can reduce our risk of Type 2 by maintaining a healthy weight.

Monogenic diabetes

Monogenic forms of diabetes, such as neonatal diabetes or Maturity Onset of Diabetes of the Young (MODY), are different. These rare forms of diabetes are directly caused by a change in a single gene alone, and this change can be passed down from parent to child. A child of someone with MODY has around a 50% (or 1 in 2) chance of developing the condition.

It’s important that people with monogenic diabetes get the right diagnosis, as they might be able to take tablets to keep their blood sugar levels stable, rather than managing their condition with insulin injections.

Genetic risk calculators

Scientists are developing genetic risk calculators. These add up the number of diabetes-related genetic changes that someone has and combine this with other factors (like their weight, or age of diagnosis) to determine their risk of developing diabetes – and which type. In the future, this could mean that we can find people at highest risk of developing a specific type of diabetes, or progressing quickly, or even developing complications, to ensure they get the best treatment and support possible.

You can read more about our research to spot newborns who have a higher risk of developing Type 1 in later life.

We can’t control which genes we inherit from our parents, or the genes we pass on to our children. But if you know that Type 1 diabetes is in your family, the most important thing to remember is the 4 T’s – thirst, tired, toilet and thinner. If Type 2 diabetes is within your family, you can also try and keep your risk as low as possible by leading an active lifestyle and having a healthy, balanced diet.

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