Current "hybrid closed-loop systems" use a continuous glucose monitor to sense blood sugar levels, and a subcutaneous insulin pump to deliver insulin; however, due to the delay between insulin injection and its action, current systems require the user to initiate insulin before taking meals. Several improvements to these systems are currently undergoing clinical trials in humans, including a dual-hormone system that injects glucagon in addition to insulin, and an implantable device that injects insulin intraperitoneally where it can be absorbed more quickly. Disease models
Various animal models of disease are used to understand the pathogenesis and etiology of type 1 diabetes. Currently available models of T1D can be divided into spontaneously autoimmune, chemically induced, virus induced and genetically induced.The nonobese diabetic (NOD) mouse is the most widely studied model of type 1 diabetes. It is an inbred strain that spontaneously develops type 1 diabetes in 30–100% of female mice depending on housing conditions. Diabetes in NOD mice is caused by several genes, primarily MHC genes involved in antigen presentation. Like diabetic humans, NOD mice develop islet autoantibodies and inflammation in the islet, followed by reduced insulin production and hyperglycemia. Some features of human diabetes are exaggerated in NOD mice, namely the mice have more severe islet inflammation than humans, and have a much more pronounced sex bias, with females developing diabetes far more frequently than males. In NOD mice the onset of insulitis occurs at 3–4 weeks of age.
Complications
The most pressing complication of type 1 diabetes are the always present risks of poor blood sugar control: severe hypoglycemia and diabetic ketoacidosis. Hypoglycemia – typically blood sugar below 70 mg/dL – triggers the release of epinephrine, and can cause people to feel shaky, anxious, or irritable. People with hypoglycemia may also experience hunger, nausea, sweats, chills, dizziness, and a fast heartbeat. Some feel lightheaded, sleepy, or weak. Severe hypoglycemia can develop rapidly, causing confusion, coordination problems, loss of consciousness, and seizure. On average, people with type 1 diabetes experience a hypoglycemia event that requires assistance of another 16–20 times in 100 person-years, and an event leading to unconsciousness or seizure 2–8 times per 100 person-years. The American Diabetes Association recommends treating hypoglycemia by the "15-15 rule": eat 15 grams of carbohydrates, then wait 15 minutes before checking blood sugar; repeat until blood sugar is at least 70 mg/dL. Severe hypoglycemia that impairs someones ability to eat is typically treated with injectable glucagon, which triggers glucose release from the liver into the bloodstream. People with repeated bouts of hypoglycemia can develop hypoglycemia unawareness, where the blood sugar threshold at which they experience symptoms of hypoglycemia decreases, increasing their risk of severe hypoglycemic events.