Diabetes and the Environment — In-Depth Doctor’s Interview
Reported December 5, 2005
William Hagopian, M.D., Ph.D, discusses type 1 diabetes, its causes, and what The Environmental Determinants in Diabetes of the Young (TEDDY) study is doing to find the direct causes of the disease.
Ivanhoe Broadcast News Transcript with
William Hagopian, M.D., Ph.D., Endocrinologist,
Pacific Northwest Research Institute, Seattle,
TOPIC: Diabetes and the Environment
What is type 1 diabetes?
Dr. Hagopian: Type 1 diabetes is an autoimmune disease, which means the immune system gets confused and attacks and destroys the insulin-producing cells in the pancreas. Eventually there are not enough insulin-producing cells and the child gets diabetes, forcing them to take insulin shots to replace that insulin level.
Why is it important to look at the environmental factors?
Dr. Hagopian: When examining the causes of the disease, it appears about half of the underlying cause can be ascribed to genes one inherits. Human leukocyte antigen (HLA) is one gene that contributes about half of the genetic risk, which is a huge amount for a polygenic disease; while the other half of the overall risk is not genetic but environmental. While we would love to figure out what these environmental triggers are. There’s been some indication from literature that viruses may cause the immune system to get confused and attack the beta cells.
How does food impact type 1 diabetes?
Dr. Hagopian: In the early part of life, the food exposures have been the easiest to study. It’s been shown that gluten exposure in the first three months of life leads to a five-fold increased risk of subsequent type 1 diabetes. There are also foods that have a smaller effect, but these are harder to prove.
What is the TEDDY study?
Dr. Hagopian: The TEDDY study is designed as a six-center international trial, where each center screens a large number of kids from the general population. Those at an increased HLA risk are then followed carefully during the first years of their lives while researchers examine environmental exposures. We focus on infectious diseases, like viruses and food exposures, because those are the ones we can easily measure. We also test psychosocial factors, life situations, allergies, medications and illnesses, but focus on food diaries, carefully sampling each portion to determine viral infections.
Do scientists know how environmental factors trigger type 1 diabetes?
Dr. Hagopian: Many studies suggest that environmental factors contribute to the cause of the disease, however those studies were underpowered. During the TEDDY study, doctors are screening 44,000 kids at each of the six sites, allowing the statistical power to help us identify factors that impact the disease. With the information we are gathering, we will be able to identify factors with an increased risk of future diabetes, and then one can then avoid them.
If a child has no genetic risk for type 1 diabetes, can environmental factors still trigger the disease?
Dr. Hagopian: Yes. However, it’s much lower. That is one of the reasons we are doing the study. We are going to partition kids into a high-risk group and a low-risk group. The high-risk group is 6 percent of the total amount of kids and has a one in 30 chance of getting diabetes. The rest have about a 1 in 1,000 chance of getting diabetes, much less than even the average kid
Do we know how environmental factors activate type 1 diabetes in the body?
Dr. Hagopian: There is some preliminary evidence suggesting the coxsackie B virus is involved. This particular virus is an internal viruses, like polio, and tends infect the gut, causing diarrhea. The reaction is so mild the child might not even know they are sick, but if they get three or four of these infections in their early childhood, it could implicate diabetes. While it doesn’t infect the eyelets, it does infect the whole pancreas. Suppose the lymph nodes, where the immune surveillance occurs by the body, drain from the pancreas and those lymph nodes drain both the eyelets and the rest of the pancreas, making the digestive enzymes go into the gut. So even if the virus is infecting those cells that make the digestive enzyme, they drain to the same place, creating a viral danger signal that’s present in the lymph nodes, along with normal antigens from the pancreas. All of these environmental factors together could trigger the immune system to get confused.
What is the study trying to accomplish?
Dr. Hagopian: We are hoping to identify two, three, or four clear risk factors for type 1 diabetes. Then we can develop preventions for avoidance therapy, either by an immunization for a virus or a recommendation that kids not eat a certain food in the first six months or 12 months of life. Through those recommendations, we’re hoping the future rate of type 1 diabetes in the world’s population goes down by avoidance of these particular factors.
END OF INTERVIEW
