Insulin is a hormone produced by the beta cells of the islets of Langerhans in the pancreas. The name of insulin comes from the Latin insula – island. Insulin effects
Despite the fact that insulin has many effects in various tissues of the human body, its main effect is to stimulate the transfer of glucose from the blood into the cells, which leads to a decrease in the concentration of glucose in the blood.
Other effects of insulin are to stimulate the synthesis of glycogen from glucose in the liver and muscles, increase the creation of fats and proteins, and suppress the activity of enzymes that break down fats and proteins. Thus, insulin has an anabolic effect, as it enhances the formation of fats and proteins, while slowing down their breakdown.
The main effect of insulin is to enhance the transport of glucose across the cell membrane into the cell. There are no other hormones that lower blood glucose levels in the human body. The main effects of insulin are in muscle and adipose tissue, which is why these tissues are called insulin-dependent. Blood glucose levels decrease when exposed to insulin and rise when exposed to so-called. hyperglycemic hormones (glucagon, growth hormone, glucocorticoids).
Additional effects of insulin are an increase in the intensity of glycogen formation, a decrease in the formation of glucose in the liver, and an increase in the absorption of amino acids necessary for protein synthesis by cells. At the same time, insulin reduces the breakdown of proteins and fats. Thus, the overall effect of insulin is anabolic – aimed at the formation of adipose and muscle tissue.
Insulin structure
Insulin is a polypeptide hormone composed of two amino acid chains: the A and B chains. The polypeptide chains are connected by disulfide bridges. Human insulin is structurally similar to porcine and bovine insulin, although it differs from them by one and three amino acid residues, respectively.
The discovery of insulin
The islets of the pancreas were discovered in 1869 by Paul Langerhans during a microscopic examination of the structure of the pancreas. In 1889, Oskar Malinowski in Germany, while removing the pancreas from a dog, caused her symptoms of diabetes. In 1921, F. Bunting and C. Best isolated insulin from the cells of the islets of the pancreas, and D. Collip developed a method for its purification.
In 1922, insulin was first administered to a diabetic patient. Its therapeutic effect has shown that this type of therapy is the most effective. In subsequent years, the main efforts of scientists were aimed at organizing production in large quantities. In 1923, the Nobel Prize was awarded for the discovery and isolation of insulin. Subsequently, the amino acid structure of insulin was completely deciphered by F. Senger.
Insulin synthesis
In the islet cells of the pancreas, insulin is synthesized in several steps. At the first stage, the synthesis of the insulin precursor molecule, preproinsulin, takes place. In the second step, a signal peptide is separated from the preproinsulin molecule, after which proinsulin is formed. After maturation, the final insulin molecule is formed. At the stage of maturation, C-peptide is separated from the proinsulin molecule, which has no biological effect. After the separation of the C-peptide, the active form of insulin is formed.
The release of insulin into the blood occurs when the level of glucose in the blood rises. In addition, the regulation of insulin production is carried out by the autonomic nervous system. The breakdown of insulin occurs in the liver and kidneys when exposed to the enzyme insulinase.
Insulin preparations
Currently, the pharmaceutical industry produces a significant number of insulin preparations with various biological effects. Allocate human, porcine insulin, bovine insulin. According to the degree of purification, traditional, monopic, monocomponent insulins are distinguished. By the time of action, insulins of short and prolonged action are released. The latter are divided into insulins of medium, long and ultra-long duration. There are also ultrashort insulins and depot insulins released slowly from the subcutaneous tissue.
The selection of an insulin therapy regimen is a complex and very responsible event. The success of achieving compensation for diabetes mellitus and, as a consequence, the patient’s quality of life depends on the correct choice of the form of insulin and its dosage regimen.