Type 1 diabetes, also known as insulin-dependent diabetes and juvenile diabetes, results when the cells of the pancreas fail to make enough insulin, an essential hormone that helps cells absorb glucose (sugar) circulating in the body. Glucose is the energy source for cells, and without enough insulin, cells functions falter and their health suffers. The likelihood of developing Type 1 diabetes increases with certain genetic and environmental risk factors.
Physiology
At its root, Type 1 diabetes is an autoimmune disorder. A malfunction in the immune system causes the body to treat the insulin-producing cells of the pancreas as foreign invaders. As antibodies engulf and destroy the cells, insulin production plummets and blood glucose levels rise. Viruses like Epstein-Barr—which causes mononucleosis, coxsackievirus, mumps, rubella, cytomegalovirus or some retroviruses—can cause a heightened immune reaction that mistakenly attacks the islet cells of the pancreas, or the virus can directly infect and destroy the cells, increasing the risk of Type 1 diabetes.
Nature vs. Environment
People with a family history of Type 1 diabetes have an increased risk for diabetes. However, even twins with the same genetic make-up only show about 50 percent concordance for Type 1 diabetes, meaning that when one twin has Type 1 diabetes, the other has it in only 50 percent of cases. In contrast, twin concordance for Type 2 diabetes is greater than 90 percent, according to the Merck Manual. Genetic factors might increase susceptibility to Type 1 diabetes, but environmental factors play an equally important role.
Expert Insight
Scientists have identified some susceptibility genes that lie in a region of the genome called the major histocompatibility complex (MHC), which determines the types of proteins displayed on cell surfaces, an important component of immune recognition. Mutations in other genes that control the manufacture and processing of insulin can contribute to Type 1 diabetes too.
Timing
Environmental factors present early in life can influence the risk for Type 1 diabetes. According to the Mayo clinic, giving cow’s milk to young babies increases the risk of Type 1 diabetes. Conversely, the vitamin D in milk protects against Type 1 diabetes. The Mayo Clinic references studies showing that introducing cereals to a baby’s diet between three to seven months of age can minimize the risk of Type 1 diabetes. Other risk factors include having jaundice or a respiratory infection as a newborn and being born to a mother with preeclampsia during the pregnancy or who was younger than 25 when giving birth.
Geography
People living in the northern countries of Finland and Sardinia have two to three times the risk of developing Type 1 diabetes compared to people in the United States. The Merck Manual suggests that this phenomenon has genetic underpinnings. People from Finland and Sardinia often carry the MHC gene alleles HLA-DR3,DQB1*0201 and HLA-DR4,DQB1*0302, which occur in more than 90 percent of patients with Type 1 diabetes. The presence of nitrates in drinking water also has been linked to increased risk for Type 1 diabetes.
