Type 2 diabetes is an autoimmune disease and not a metabolic disorder
The research, published in Nature Medicine, changes perception of type 2 diabetes completely. Its authors consider that type 2 diabetes is caused by autoimmune reactions with B cells engaged. The discovery makes the disease similar to type 1 diabetes, which results from destroying of insulin-producing cells by immune system in pancreas. The research suggests development of new drugs for type 2 diabetes, which will regulate immune processes. While existing treatments control the levels of blood sugar.
Type 2 diabetes is characterized by tissues’ resistance to insulin – hormone, which causes cells to take up glucose from the blood. It is proved that insulin resistance is associated with obesity and usually runs in families. The researchers consider insulin resistance is caused by the attacks of B cells (lymphocytes producing antibodies) and other immune cells on the own body. Their theory redefines the disease as an autoimmune pathology rather than a metabolic disorder.
Several years ago the researchers suggested the immune cells, including T cells and B cells, might cause inflammation in the fatty tissue around internal organs. They examined mice with high-fat and high-calorie diet demonstrating this type of inflammation. The animals’ fat tissue expanded rapidly while its blood supply lagged. This resulted in death of fat cells, and their content was spilled out. The immune system reacted with sending macrophages to clean up the tissue.
Besides, T cells and B cells were involved in the immune process, making the remaining fat cells less responsive to insulin. As a result fatty acids appeared in the blood causing high cholesterol, fatty liver and high blood pressure. The scientists decided to focus on B cells because their antibodies not only fight infections but also may cause pathologies. In their new experiments they used genetically engineered mice without B cells. These animals were on high-fat, high-calorie diet but didn’t develop insulin resistance.
To find out if the same processes occur in humans, the scientists examined 32 overweight individuals with different levels of insulin sensitivity. They discovered that people with insulin resistance had antibodies against some of proteins, while healthy ones did not produce them. It demonstrated that insulin resistance in humans is linked to autoimmune reactions. It may lead to creating new immune-modulating therapies for type 2 diabetes.