Structural (PyMOL) model of IGF-1. "Protein IGF1 PDB 1bqt" by Emw - Own work. Licensed under CC BY-SA 3.0 via Commons -

Insulin-like growth factor 1 (IGF-1) is a hormone related to growth and development in animals. As the name suggests, it is closely related to insulin in terms of structure. IGF-1 binds to its own receptor, IGFR. Reductions in, or antagonism of, IGF-1 activity is associated with the wastage of organs associated with starvation and some forms of cancer¹.

IGF-1 and Muscle Growth

IGF-1, signaling through calcineurin, may have a role in the regulation of growth in muscle tissue². The expression of genes for these proteins (IGF-1 and CnAα) was found consistently in a study using duck embryos, focusing on the development of leg and breast muscle. This gene expression varied significantly over time, although it was at its highest at day 13 of embryonic development². The expression of IGF-1 and CnAα was related to type IIb fibers, but not type I or type IIa fibers². Another similar study reported that variations in the pectoralis muscles of duck chick mirrored those of MSTN (the gene for myostatin, another regulator of muscle development) and IGF-1 expression³. This indicates that IGF-1 is involved in the timing of muscle development in infant animals, and of that of the transition between muscle fiber types³.

IGF-1 and Bone Growth 

IGF-1 is also associated with the promotion of bone cell subtype (osteoclasts) proliferation. Reductions in the activity and populations of these cells are implicated in diseases that destroy bone, which include some forms of multiple myeloma⁴. The hormone may be used to confirm the osteoclastogenesis of proposed treatments such as glycosphingolipids in animal models of myeloma⁴.

IGF-1 and Neuropathic Conditions

IGF-1 is also known to be neurotrophic, or to influence the survival, function and development of neurons in the central nervous system⁵. This implies a role for this hormone in improved outcomes for animals with conditions that involve damage or death in these cells. Amyotrophic lateral sclerosis (ALS) is an example of these, in which motor neurons are affected, with an additional component of localized inflammation⁵. A study incorporating a mouse model of ALS found that the immunization of mice with a myelin-derived vaccine resulted in increases of IGF-1 in spinal tissue⁵. This led to reduced disease activity and increased survival in these animals⁵.     

References:

1. Kwon Y, Song W, Droujinine IA, Hu Y, Asara JM, Perrimon N. Systemic organ wasting induced by localized expression of the secreted insulin/IGF antagonist ImpL2. Dev Cell. 2015;33(1):36-46.

2. Shu J, Li H, Shan Y, et al. Expression profile of IGF-I-calcineurin-NFATc3-dependent pathway genes in skeletal muscle during early development between duck breeds differing in growth rates. Dev Genes Evol. 2015;225(3):139-148.

3. Hu Y, Liu H, Shan Y, et al. The relative expression levels of insulin-like growth factor 1 and myostatin mRNA in the asynchronous development of skeletal muscle in ducks during early development. Gene. 2015;567(2):235-243.

4. Ersek A, Xu K, Antonopoulos A, et al. Glycosphingolipid synthesis inhibition limits osteoclast activation and myeloma bone disease. J Clin Invest. 2015;125(6):2279-2292.

5. Kunis G, Baruch K, Miller O, Schwartz M. Immunization with a Myelin-Derived Antigen Activates the Brain's Choroid Plexus for Recruitment of Immunoregulatory Cells to the CNS and Attenuates Disease Progression in a Mouse Model of ALS. J Neurosci. 2015;35(16):6381-6393.