Regulation of insulin secretion

Insulin is secreted by pancreatic cells in the human body. The concentration of blood sugar actually plays a key role in regulating the secretion of insulin. Amino acids also have some effect on stimulating the secretion of insulin, but not as obvious as blood sugar. When the human body consumes too much protein, the secretion of insulin will also increase accordingly.

1. The role of blood sugar

Blood sugar concentration is the most important factor in regulating insulin secretion. When blood sugar concentration increases, insulin secretion increases significantly, thereby promoting lowering of blood sugar. When blood sugar concentration drops to normal levels, insulin secretion also quickly returns to basal levels. Under the stimulation of sustained high blood sugar, the secretion of insulin can be divided into three stages: within 5 minutes of blood sugar rising, the secretion of insulin can increase by about 10 times, which is mainly derived from the release of hormones stored in B cells, so it does not last long, and the secretion of insulin drops by 50% after 5 to 10 minutes; 15 minutes after blood sugar rises, there is a second increase in insulin secretion, reaching a peak in 2 to 3 hours and lasting for a longer time, and the secretion rate is also much greater than the first phase, which is mainly due to the activation of the B cell insulin synthase system, promoting synthesis and release; if high blood sugar persists for about a week, the secretion of insulin can further increase, which is caused by long-term high blood sugar stimulating B cell proliferation.

2. The role of amino acids and fatty acids

Many amino acids can stimulate insulin secretion, among which arginine and lysine have the strongest effect. When blood sugar concentration is normal, the increase in amino acid content in the blood can only slightly stimulate the secretion of insulin. However, if blood sugar is high, excess amino acids can double the insulin secretion caused by blood sugar. When fatty acids and ketone bodies increase significantly, insulin secretion can also be promoted.

3. The role of hormones

The hormones that affect insulin secretion are:

① Gastrointestinal hormones, such as gastrin, secretin, cholecystokinin and gastric inhibitory peptide, all promote insulin secretion;

② Growth hormone, cortisol, thyroid hormone and glucagon can indirectly stimulate insulin secretion by increasing blood sugar concentration. Therefore, long-term and high-dose use of these hormones may cause B cell failure and lead to diabetes.

③ The growth inhibitor secreted by pancreatic D cells can inhibit the secretion of insulin and glucagon at least through paracrine effects, while glucagon can also directly stimulate B cells to secrete insulin.

4. Neuromodulation

The pancreatic islets are innervated by the vagus nerve and the sympathetic nerve. Stimulating the vagus nerve can directly promote the secretion of insulin by acting on the M receptor through acetylcholine; the vagus nerve can also indirectly promote the secretion of insulin by stimulating the release of gastrointestinal hormones. When the sympathetic nerves are excited, norepinephrine acts on the α2 receptors to inhibit the secretion of insulin.