The insulin-like growth factors ( IGFs ) are proteins with high sequence similarity to insulin . IGFs are part of a complex system that cells use to communicate with their physiologic environment. This complex system (often referred to as the IGF "axis") consists of two cell-surface receptors ( IGF1R and IGF2R ), two ligands ( IGF-1 and IGF-2 ), a family of seven high-affinity IGF-binding proteins ( IGFBP1 to IGFBP7 ), as well as associated IGFBP degrading enzymes , referred to collectively as proteases .
14-481: IGF may stand for: Insulin-like growth factor Independent Games Festival Internet Governance Forum Identity Governance Framework Inoki Genome Federation International Golf Federation International Genetics Federation International Graphical Federation , a former global union federation Israeli Ground Forces International Go Federation Induced gas flotation Topics referred to by
28-508: Is capable of activating the insulin receptor , it can also complement for the effects of insulin . Receptors for IGF-1 are found in vascular smooth muscle, while typical receptors for insulin are not found in vascular smooth muscle. IGF-1 and IGF-2 are regulated by a family of proteins known as the IGF-binding proteins . These proteins help to modulate IGF action in complex ways that involve both inhibiting IGF action by preventing binding to
42-481: Is different from Wikidata All article disambiguation pages All disambiguation pages Insulin-like growth factor The IGF "axis" is also commonly referred to as the Growth Hormone/IGF-1 Axis. Insulin-like growth factor 1 (commonly referred to as IGF-1 or at times using Roman numerals as IGF-I) is mainly secreted by the liver as a result of stimulation by growth hormone (GH). IGF-1
56-413: Is important for both the regulation of normal physiology, as well as a number of pathological states, including cancer . The IGF axis has been shown to play roles in the promotion of cell proliferation and the inhibition of cell death ( apoptosis ). Insulin-like growth factor 2 (IGF-2, at times IGF-II) is thought to be a primary growth factor required for early development while IGF-1 expression
70-417: Is required for achieving maximal growth. Gene knockout studies in mice have confirmed this, though other animals are likely to regulate the expression of these genes in distinct ways. While IGF-2 may be primarily fetal in action it is also essential for development and function of organs such as the brain , liver , and kidney . Factors that are thought to cause variation in the levels of GH and IGF-1 in
84-595: Is the "physiological" receptor. IGF-1 binds to it at significantly higher affinity than it binds the insulin receptor. Like the insulin receptor, the IGF-1 receptor is a receptor tyrosine kinase —meaning the receptor signals by causing the addition of a phosphate molecule on particular tyrosines. The IGF-2 receptor only binds IGF-2 and acts as a "clearance receptor"—it activates no intracellular signaling pathways, functioning only as an IGF-2 sequestering agent and preventing IGF-2 signaling. Since many distinct tissue types express
98-441: The IGF-1 receptor as well as promoting IGF action possibly through aiding in delivery to the receptor and increasing IGF half-life. Currently, there are seven characterized IGF Binding Proteins (IGFBP1 to IGFBP7). There is currently significant data suggesting that IGFBPs play important roles in addition to their ability to regulate IGFs. IGF-1 and IGFBP-3 are GH dependent, whereas IGFBP-1 is insulin regulated. IGFBP-1 production from
112-410: The IGF-1 receptor, IGF-1's effects are diverse. It acts as a neurotrophic factor, inducing the survival of neurons. It may catalyse skeletal muscle hypertrophy , by inducing protein synthesis , and by blocking muscle atrophy . It is protective for cartilage cells, and is associated with activation of osteocytes , and thus may be an anabolic factor for bone . Since at high concentrations it
126-514: The circulation include an individual's genetic make-up, the time of day, age, sex, exercise status, stress levels, nutrition level, body mass index (BMI), disease state, race, estrogen status, and xenobiotic intake. IGF-1 has an involvement in regulating neural development including neurogenesis , myelination , synaptogenesis , and dendritic branching and neuroprotection after neuronal damage. Increased serum levels of IGF-I in children have been associated with higher IQ . IGF-1 shapes
140-544: The development of the cochlea through controlling apoptosis . Its deficit can cause hearing loss. Serum level of it also underlies a correlation between short height and reduced hearing abilities particularly around 3–5 years of age, and at age 18 (late puberty ). The IGFs are known to bind the IGF-1 receptor , the insulin receptor , the IGF-2 receptor , the insulin-related receptor and possibly other receptors. The IGF-1 receptor
154-466: The liver is significantly elevated during insulinopenia while serum levels of bioactive IGF-1 is increased by insulin. Studies of recent interest show that the Insulin/IGF axis play an important role in aging . Nematodes , fruit-flies , and other organisms have an increased life span when the gene equivalent to the mammalian insulin is knocked out . It is somewhat difficult to relate this finding to
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#1732851095733168-580: The mammals, however, because in the smaller organism there are many genes (at least 37 in the nematode Caenorhabditis elegans ) that are "insulin-like" or "IGF-1-like", whereas in the mammals insulin-like proteins comprise only seven members ( insulin , IGFs, relaxins , EPIL, and relaxin-like factor). The human insulin-like genes have apparently distinct roles with some but less crosstalk presumably because there are multiple insulin-receptor-like proteins in humans. Simpler organisms typically have fewer receptors; for example, only one insulin-like receptor exists in
182-407: The nematode C. elegans . Additionally, C. elegans do not have specialized organs such as the ( Islets of Langerhans ), which sense insulin in response to glucose homeostasis. Moreover, IGF1 affects lifespan in nematodes by causing dauer formation, a developmental stage of C. elegans larva. There is no mammalian correlate. Therefore, it is an open question as to whether either IGF-1 or insulin in
196-403: The same term [REDACTED] This disambiguation page lists articles associated with the title IGF . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=IGF&oldid=1066991127 " Category : Disambiguation pages Hidden categories: Short description
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