Insulin like growth factor (IGF) is a group of peptides with growth-promoting effects, and its secreted cells are widely distributed in human liver, kidney, lung, heart, brain, intestine and other tissues. IGF family has IGF1 and IGF2 two kinds. The generation of IGF1 is more dependent on GH, which has a strong growth-promoting effect and is an important growth factor in childhood. The IGF1 synthesized in each tissue mostly exerts its growth-promoting function in the form of autocrine or paracrine, while the IGF1 synthesized in the liver enters the blood circulation and ACTS on the target cells in the form of endocrine. The level of IGF1 in vivo is regulated by GH, and IGF1 also has negative feedback regulation effect on GH secretion. The insulin-like effect of IGF2 is stronger and plays an important role in fetal growth.
IGF mediates the stimulation of growth hormone, regulates tissue growth and development, and plays an important role in the maintenance of muscle volume and strength, body composition and the regulation of nutrient metabolism. Through endocrine, paracrine and/or autocrine modes, target cell surface receptors IGF1R and IGF2R mediate its biological effects and are regulated by IGF binding protein. Most of the extrahepatic tissues can locally produce IGF, and most of them are not regulated by GH, which plays an important role in local tissues.
Insulin-like growth factor receptor IGF must bind to its specific receptor after dissociation with the carrier protein IGF binding protein (IGFBP). IGF receptor is divided into two types, namely IGF1 receptor (such as IGFBP3) and IGF2 receptor (such as IGF2R).The latter has no amino acid kinase activity. Let me introduce you to two members of the IGF family below:
1.IGF1
The full name of IGF1 is insulin-like growth factor no.1, also known as "growth promoting factor" (somatomedin C), which is a kind of peptide protein substance similar to insulin in molecular structure. IGF1 plays an important role in the growth of infants and the continuous anabolism in adults.
IGF1 is known to be an active protein polypeptide substance, which is the product of autocrine and paracrine of liver cells, kidney cells, spleen cells and a dozen other kinds of cells in human body (that is to say, IGF1 is contained in human body itself).
1. Lowering blood glucose: in this respect, IGF1 is similar to insulin in that it can enhance the absorption of glucose and amino acids, promote the synthesis of glycogen and the secretion of lactic acid, inhibit the decomposition of glycogen, increase the sensitivity of human body to insulin, and improve the efficiency of human insulin. It has a good effect on insulin-dependent diabetes mellitus (type II diabetes mellitus).
2. Lowering blood lipids: IGF1 acts on fat cells to promote fat decomposition and glycogen synthesis, and reduce the levels of total triglycerides, very low-density lipoprotein triglycerides and low-density lipoprotein cholesterol in blood.
3. Relaxing blood vessels: IGF1 can regulate the physiological and pathological conditions of the heart and has the function of diastolic blood vessels, reducing vascular resistance and increasing blood flow to the heart.
4. Promoting bone anabolism to maintain its normal structure and function: IGF1 can significantly promote the proliferation of chondrocytes from multiple sources and the synthesis of cartilage matrix. IGF1 can also stimulate chondrocytes to synthesize cartilage matrix specific collagen type II collagen, increase the activity of glycosamine polyase, and enhance the activity of alkaline phosphatase of osteoblasts.
5. Promoting human growth: IGF1 is a very important cell mitotic promoter in human body.
6. Promoting cell differentiation: IGF1 is important for maintaining the level of proteins related to cell differentiation, and its combination with some growth factors can promote cell differentiation and maturation.
7. Wound repair: IGF1 is also involved in the process of wound healing. It was demonstrated that the concentration of IGF1 in injured nerve, muscle and skin cells increased.
It is worth mentioning that studies have found that igf-1 may protect renal tubular epithelial cells through the ERK/MAPK1 signaling pathway when kidney is damaged.
2.IGF2
Insulin-like growth factor 2 (IGF2), also known as somatomedin A, is the most complex and versatile growth factor known. The original IGF2 just transcribed is a polypeptide chain composed of 156 amino acid residues. After subsequent shearing and processing, mature IGF2 is a kind of small weak acid polypeptide composed of 67 amino acid residues, with a molecular weight of 7471u. However, a 9000u IGF2 has been found in human spinal fluid, a higher molecular weight IGF2 has been found in human brain, and a 15000u IGF2 has been found in human serum. IGF2 can promote cell mitosis and differentiation, participate in postnatal genome reconstruction, and has an important relationship with the inactivation of X chromosome. All these functions indicate the importance of IGF2 in the growth and development of the body. In addition, IGF2 is closely related to individual growth rate, lean meat rate, backfat thickness and other production performance, and has been identified as a candidate gene in some species as an important imprinting gene. The expression of IGF2 is closely related to the occurrence and development of tumors, and plays an important role in tumor treatment.