Inhaled insulin therapy for patients with diabetes mellitus

Diabetes mellitus is a devastating disease that is a leading cause of blindness, end stage renal disease, neuropathies, and peripheral vascular disease that lead to amputations. It is also a coronary heart disease equivalent (1,2) and is the sixth leading cause of death in the United States (3). Diabetes is a national epidemic that has been diagnosed in approximately 16 million Americans, and it is estimated that an additional 6 million Americans have undiagnosed diabetes (3). The incidence of diabetes is on the rise, and is expected to continue, especially type 2 diabetes mellitus (T2DM) (4). Diabetes can be simply classified into type 1 (insulin dependent) and type 2 (non-insulin dependent) diabetes mellitus (5). Type 1 diabetes (T1DM) is characterized by autoimmune destruction of insulin-producing b-cells in the pancreas causing hyperglycemia (6). These patients require exogenous insulin replacement to maintain glucose homeostasis. Type 2 diabetes is characterized by insulin resistance and progressive b-cell failure (7). Patients with T2DM can be managed with oral therapy initially (insulin sensitizers – insulin secretagogues); however, a large number of patients will require exogenous insulin therapy along with insulin sensitizers due to progressive b-cell failure. Insulin is an excellent choice, as its glucose-lowering potential is limited only by the potential side effect of hypoglycemia. Insulin therapy may have additional benefits, as the early use of insulin may slow the loss of beta cell insulin secretory function in type 2 diabetic patients versus sulfonylureas.