Neuroactive Products of IGF-I and IGF-2 Gene Expression in the CNS
The insulin-like growth factors (IGFs) consist of IGF-1 and IGF-2, as well as variants arising from either alternative RNA processing or post-translational modification of the IGF precursor. In the extracellular fluid or circulating, the IGFs are associated with their carrier proteins which are believed to function as transporters, directing the IGFs to their target cells (35). The IGFs act as both endocrine hormones on distal target cells, as well as locally as paracrine or autocrine hormones. While the IGFs have long been recognized as growth and anabolic factors for a wide variety of tissues and cell types, such as cartilage, muscle, and fibroblasts, their role within the nervous system has only been widely recognized over the last several years. However, historically this can be traced back to the experiments of Stephan Zamenhof in the 1940’s, who demonstrated that crude pituitary extracts of growth hormone stimulated the growth of tadpole and rat brains. This brain growth-promoting activity was later shown to be due to a growth hormone dependent growth factor, later identified as truncated IGF-1 (32). Both IGF-1 and IGF-2 are synthesized within the central nervous system where they are believed to fulfill different functions mediated via their receptors.
KeywordsNMDA Receptor Human Fetal Brain Bovine Colostrum High Molecular Weight Form Porcine Uterus
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