In the endocrine pancreas, the islets of Langerhans contain at least 4 types of endocrine cells, including A (alpha, glucagon producing), B (beta, insulin, and amylin producing), D (delta, somatostatin producing), and F (pancreatic polypeptide producing). Of these, the B (insulin-producing) cells are the most numerous.
The most common pancreatic disease requiring pharmacologic therapy is diabetes mellitus, a deficiency of insulin production or effect. Diabetes is treated with several parenteral formulations of insulin and oral or parenteral noninsulin antidiabetic agents. Glucagon, a hormone that affects the liver, cardiovascular system, and gastrointestinal tract, can be used to treat severe hypoglycemia.
|α-Glucosidase||An enzyme in the gastrointestinal tract that converts complex starches and oligosaccharides to monosaccharides; inhibited by acarbose and miglitol|
|Beta (B) cells in the islets of Langerhans||Insulin-producing cells in the endocrine pancreas|
|Hypoglycemia||Dangerously lowered serum glucose concentration; a toxic effect of high insulin concentrations and the secretagogue class of oral antidiabetic drugs|
|Lactic acidosis||Acidemia due to excess serum lactic acid; can result from excess production or decreased metabolism of lactic acid|
|Type 1 diabetes mellitus||A form of chronic hyperglycemia caused by immunologic destruction of pancreatic beta cells|
|Type 2 diabetes mellitus||A form of chronic hyperglycemia initially caused by resistance to insulin; often progresses to insulin deficiency|
Two major forms of diabetes mellitus have been identified. Type 1 diabetes usually has its onset during childhood and results from autoimmune destruction of pancreatic B cells. Type 2 diabetes is a progressive disorder characterized by increasing insulin resistance and diminishing insulin secretory capacity. Type 2 diabetes is frequently associated with obesity and is much more common than type 1 diabetes. Although type 2 diabetes usually has its onset in adulthood, the incidence in children and adolescents is rising dramatically, in parallel with the increase in obesity in children and adolescents.
The clinical history and course of these 2 forms differ considerably, but treatment in both cases requires careful attention to diet, fasting and postprandial blood glucose concentrations, and serum concentrations of hemoglobin A1c, a glycosylated hemoglobin that serves as a marker of glycemia. Type 1 diabetes requires treatment with insulin. The early stages of type 2 diabetes usually can be controlled with noninsulin antidiabetic drugs. However, patients in the later stages of type 2 diabetes often require the addition of insulin to their drug regimen.
Insulin is synthesized as the prohormone proinsulin, an 86-amino-acid single-chain polypeptide. Cleavage of proinsulin and cross-linking result in the 2-chain 51-peptide insulin molecule and a 31-amino-acid residual C-peptide. Neither proinsulin nor C-peptide appears to have any physiologic actions.
Insulin has important effects on almost every tissue of the body. When activated by the hormone, the insulin receptor, a transmembrane tyrosine kinase, phosphorylates itself and a variety of ...