TEDDY STUDY – Researching the Causes of Type 1 diabetes
What causes type 1 diabetes? There’s no one easy answer to this question, but researchers are working to find one. It’s widely agreed upon that type 1 diabetes is caused by some combination of environmental and genetic factors. The Environmental Determinants of Diabetes in the Young (TEDDY) Study aims to shed light on exactly what those triggers are that could lead to type 1 diabetes onset.
Researchers are studying a group of nearly 9,000 children from four countries from birth to 15 years old who are at an elevated risk for type 1 diabetes. In each of these 9,000 children and families, TEDDY is looking at a list of environmental and gene-environment interactions that could be causing the autoimmune response that leads to beta cell destruction.
What are they looking for? Participants provide information about diet, illnesses, psychosocial risk factors and more. Then, they’re followed by researchers and tested for the presence of autoantibodies in the blood. Antibodies indicate that the body is targeting its own cells in an immune attack – which is what leads to beta cell destruction and type 1.
The study tested for two different forms of autoantibodies that are predictors for type 1 diabetes—insulin autoantibodies (IAA) and glutamic acid decarboxylase autoantibodies (GADA). Interestingly, this study has shown that these two autoantibodies represent separate disease processes with distinct risk factors that both result in type 1 diabetes. “We are now talking about type 1 diabetes as being a heterogeneous collection of diseases, not a single disease, and have the data to support this concept.” explained Dr. Jeffrey Krischer, PhD, a TEDDY study coordinator.
So far, TEDDY has not pinpointed conclusive causes for type 1 diabetes, but it has revealed new associations worth further exploration.
Maternal dietary supplement use
TEDDY researchers concluded that Vitamin D and omega-3 fatty acids taken by mothers during pregnancy do not appear to be related to risk of type 1 diabetes.
Respiratory infections during pregnancy
By comparing mothers’ illness history during pregnancy to the specific genetics of the child, researchers were able to find several highly specific patterns. In children with HLA-DR_DQ 4-8/8-4 genotype, respiratory infections in the mother made it LESS likely that the IAA autoantibodies were the first to appear, and another genotype made it less likely that the GAD autoantibodies were the first to appear. This is a notable example of the way that the environment (the respiratory infection as a potential trigger) has complicated interactions with genetics.
TEDDY results around gastrointestinal infections in children revealed an interesting pattern in which of the two types of autoantibodies were likely to appear first (IAA or GAD). Children under 4 who had viral gastrointestinal infections in any six-month period were more likely to develop autoimmunity via GADA, rather than IAA.
Family diabetes history
In the diabetes community, we certainly hear anecdotally about type 1 diabetes running in families. TEDDY results reveal that children with a father or sibling with type 1 diabetes were more likely to develop islet autoimmunity, but that having a mother with type 1 diabetes did not increase the likelihood of the child developing type 1 diabetes (T1D).
Another interesting family history correlation: TEDDY participants with a second-degree relative with type 2 diabetes progressed more slowly from showing autoimmunity to developing clinical type 1 diabetes.
TEDDY researchers aren’t quite ready to answer the “What causes type 1 diabetes” question just yet. But their work is far from over. The TEDDY cohort of almost 9,000 children across international research centers provides a massive amount of data that likely holds more information about the factors contributing to the onset of type 1 diabetes—so keep an eye out for TEDDY news in the future.