News from the ADA: the latest on Type 1 diabetes – by Emily Burns
We’ve given you an American Diabetes Association update on Type 2 diabetes research, and research more generally. Now it’s time for Type 1 diabetes, focusing on causes.
What increases the risk of Type 1?
We don’t know what causes Type 1, but it’s most likely to involve a higher genetic risk, due to changes in specific genes, alongside an environmental trigger(s). So far, we’ve got an idea of what some of those environmental triggers could be, but we need more evidence.
With this in mind, a big ticket session at the ADA this year was the TEDDY study: The Environmental Determinants of Diabetes in the Young. TEDDY screened 48,000 babies in the general population, recruiting 7,700 with a high genetic risk of developing Type 1 diabetes. They also screened 6,400 babies who had a sibling or parent with Type 1, recruiting another 949. The babies are seen four times a year by one of six research teams across the world. The team takes a range of samples, including blood, nasal swabs, urine, stools, nails and saliva.
They’re looking for molecules in the blood called ‘auto-antibodies’ – a sign that the immune system has wrongly begun to recognise the pancreas as foreign, the first step in the development of Type 1 diabetes. Having auto-antibodies doesn’t guarantee a diagnosis of Type 1 diabetes, but the risk is higher. There are also different types of auto-antibodies, and scientists believe that the type of immune attack might be defined by which auto-antibody appears first.
The scientists are collecting information about what the children eat, when they get sick (and what with), their life experiences and their wider families. Importantly, they’re looking for differences in these environmental factors between the children who develop Type 1 diabetes and the children who don’t.
So what have they found so far?
In Type 1 diabetes, the immune system starts to change very early on in life, which suggests that any environmental trigger happens very early too. So TEDDY looked at pregnancy.
TEDDY didn’t find any association between pregnancy supplements vitamin D or Omega 3 fatty acids and the risk of Type 1 diabetes in children. Studies looking at vitamin D and Omega 3 fatty acids have had different results so far, with some suggesting they could play a role in reducing the risk of Type 1 diabetes in babies. TEDDY suggests they don’t, but the scientists did suggest that they can’t yet rule out the potential benefits of taking supplements at specific points during pregnancy – something that TEDDY couldn’t examine.
What about infections during pregnancy? They asked mums to complete a questionnaire about the types of infections they experienced during their pregnancy. The results suggest that respiratory infections might influence which type of auto-antibody appears first. This is quite complex, but does shed more light on this potential link between the environment and a child’s genes.
They didn’t just look for infections in mums, they also looked at stomach infections in the first 48 months of the babies’ lives. While stomach infections didn’t increase the risk of Type 1 diabetes, they were associated with the appearance of a particular auto-antibody called GAD. And if babies also had a chest infection, this association grew stronger.
But that was where the association ended – multiple different auto-antibodies are needed before Type 1 diabetes will develop, and the infections didn’t predict this shift from one (like GAD) to more than one.
Finally, family history. They looked for Type 1, Type 2 and gestational diabetes, alongside other autoimmune conditions, in siblings, parents, aunts, uncles and grandparents. They found that having a sibling or dad (but not mum) with Type 1 diabetes predicted the appearance of auto-antibodies, as did having an aunt, uncle or grandparent with Type 1 diabetes.
Here’s the really interesting part: having an aunt, uncle or grandparent with Type 2 diabetes appeared to slow down the time it took for a child to progress from having auto-antibodies to developing Type 1 diabetes. In other words, it appeared to be protective. Although early days, this is an exciting find. We don’t know much about the connection between Type 2 diabetes and auto-immunity.
TEDDY is by no means finished. While they haven’t found any strong links to environmental factors yet, research like this helps us begin to untangle a very complex picture. And with this work linked to the POInT study (to see if insulin powder can prevent Type 1 diabetes), we’re bound to learn much more about the causes of Type 1 diabetes and how we might prevent it over the next few years.