Which organ secretes insulin

Although the word insulin is not unfamiliar, many people do not know which organ in the body secretes insulin. In fact, this substance is secreted by the substances in the pancreas. If the secretion is abnormal, it will cause abnormal reactions in the insulin index during the examination, which will cause the occurrence of disease.

Insulin is a protein hormone secreted by pancreatic beta cells in the pancreas in response to endogenous or exogenous substances such as glucose, lactose, ribose, arginine, glucagon, etc. Insulin is the only hormone in the body that lowers blood sugar, while promoting the synthesis of glycogen, fat and protein. Exogenous insulin is mainly used to treat diabetes.

The rate of insulin biosynthesis is affected by plasma glucose concentration. When blood glucose concentration increases, the proinsulin content in β cells increases and insulin synthesis accelerates.

Insulin is synthesized in the pancreatic β cells. Insulin has a molecular weight of 5700 and is composed of two amino acid peptide chains. The A chain has 21 amino acids and the B chain has 30 amino acids. There are two disulfide bonds between the AB chains.

Insulin and C-peptide are secreted into the blood in equal molecules. Patients who are clinically treated with insulin have insulin antibodies in their serum, which affect the determination of blood insulin levels by radioimmunoassay. In this case, the state of endogenous insulin secretion can be understood by measuring plasma C-peptide levels.

Influencing factors

The secretion of insulin in the body is mainly affected by the following factors:

Plasma glucose concentration Plasma glucose concentration is the most important factor affecting insulin secretion. Following oral or intravenous administration of glucose, insulin release occurs in a biphasic response. In the early rapid phase, insulin in portal vein plasma reaches its maximum value within 2 minutes and then drops rapidly; in the delayed slow phase, plasma insulin level gradually rises again after 10 minutes and continues for more than 1 hour. The early rapid phase shows the release of stored insulin triggered by glucose, and the delayed slow phase shows the synthesis of insulin and the conversion of proinsulin to insulin.

After eating protein-rich foods, the amino acid concentration in the blood increases and insulin secretion also increases. Arginine, lysine, leucine and phenylalanine all have a strong effect in stimulating insulin secretion.

The increase in gastrointestinal hormones after meals can promote insulin secretion. For example, gastrin, secretin, gastric inhibitory peptide, and intestinal vasoactive peptide all stimulate insulin secretion.

The autonomic nervous system function state promotes insulin secretion when the vagus nerve is excited, and inhibits insulin secretion when the sympathetic nerve is excited.