Studies suggest one of the most selective growth hormone (GH) boosting peptides accessible for the study is Ipamorelin, a short synthetic agonist of the growth hormone secretagogue (GHS) receptor. Ipamorelin is popular among researchers studying the effects of GHS stimulation on development, muscular function, bone development, diabetes, and postoperative ileus. The lack of more studies on Ipamorelin is puzzling, considering the peptide's properties, possible research applications, and inexpensive cost.
How Does Ipamorelin Work?
Ipamorelin, a synthetic, very specific agonist of the GHS receptor, was developed for research in the context of postoperative ileus. The natural protein ghrelin is the source of growth hormone-releasing peptide-1, from which Ipamorelin was created. The stomach secretes the hormone ghrelin, often known as the hunger hormone, to encourage food consumption. Neuropeptide Y and growth hormone levels are elevated because they stimulate cells in the anterior pituitary gland. Ghrelin is an essential hormone for energy metabolism, learning, memory, the sleep-wake cycle, and reward cognition.
Ipamorelin is a simple recombinant protein with a short sequence of five amino acids (Aib-His-D-2Nal-D-Phe-Lys). Research suggests that Ipamorelin is more selective than ghrelin and may be more practical as it keeps some of the ghrelin's characteristics but not all.
What is Ipamorelin's Purpose?
The hypothalamus and anterior pituitary gland have large levels of the GHS receptor, also called the ghrelin receptor, since ghrelin is believed to be the natural agonist. When agonists bind to the GHS-R in the pituitary gland, it triggers the anterior pituitary gland to produce growth hormone. The five amino acids that ghrelin uses most effectively to bind to GHS-R are believed to be found in Ipamorelin. As a result, this little peptide is the tiniest GHS-R agonist currently known.
Neuropeptide Y is released when GHS receptors in the hypothalamus are stimulated. Therefore, Ipamorelin's presentation has been hypothesized to also cause changes in energy metabolism, an increase in hunger signaling, and a reduction in pain perception by stimulating the production of this peptide.
Ipamorelin Peptide Research
The original intention of Ipamorelin's development was to aid in the context of postoperative ileus, an emergency characterized by the gastrointestinal system shutting down.
Researchers speculate the high selectivity of Ipamorelin is one of the reasons why it is of significant relevance in research settings. There are a lot of off-target effects with other ghrelin analogs, which means that the pituitary gland releases more hormones than only growth hormone. The unique potential of Ipamorelin is hypothesized to be not influencing the levels of any of these hormones: cortisol, luteinizing hormone, adrenocorticotrophic hormone (ACTH), prolactin, follicle-stimulating hormone, and thyroid-stimulating hormone.
Ipamorelin Peptide and Pain Perception
Investigations purport that a key function of neuropeptide Y is to potentially reduce the experience of pain, as mentioned above. So, it's not surprising that substances that trigger the production of neuropeptide Y may also have analgesic effects. Several substances, including ghrelin and its analogs, such as Ipamorelin, have been theorized to decrease the sense of pain.
Findings imply that although Ipamorelin may reduce pain wherever it goes, studies have indicated that it may work well for neuropathic pain (pain caused by malfunctioning nerves) and visceral pain (pain in the gastrointestinal system and organs). Rat studies purport Ipamorelin may lessen pain perception by a factor of two. Irritable bowel syndrome and inflammatory bowel illness are the main focus areas here. However, researchers speculate Ipamorelin may also have uses in diabetic neuropathy, degenerative disk disease, and post-stroke pain syndromes. In these contexts, Ipamorelin seems to alter pain perception in the research models of these disorders.
Ipamorelin and Bone
The fact that Ipamorelin may aid in controlling bone turnover and encouraging more mineralization of bones is perhaps the most intriguing speculation linked to it. According to rat studies, Ipamorelin appears to stimulate the production of new bone and the mineralization of existing bone, leading to increased bone formation.
Ipamorelin is speculated to counteract the effects of compounds which may weaken bones. For example, according to this study, Ipamorelin seems to halt bone loss associated with long-term corticosteroid exposure and may stimulate bone production up to four times in rats. This discovery was made by chance while studying Ipamorelin's potential to avoid the changes in body composition that are common with long-term exposure.
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References
[i] D. E. Beck, W. B. Sweeney, M. D. McCarter, and Ipamorelin 201 Study Group, “Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients,” Int. J. Colorectal Dis., vol. 29, no. 12, pp. 1527–1534, Dec. 2014, doi: 10.1007/s00384-014-2030-8.
[ii] B. Greenwood-Van Meerveld, K. Tyler, E. Mohammadi, and C. Pietra, “Efficacy of ipamorelin, a ghrelin mimetic, on gastric dysmotility in a rodent model of postoperative ileus,” J. Exp. Pharmacol., vol. 4, pp. 149–155, 2012, doi: 10.2147/JEP.S35396.
[iii] K. Raun et al., “Ipamorelin, the first selective growth hormone secretagogue,” Eur. J. Endocrinol., vol. 139, no. 5, pp. 552–561, Nov. 1998, doi: 10.1530/eje.0.1390552.
[iv] M. Alfalah, Neuropeptide Y and Related Peptides. Springer Science & Business Media, 2004.
[v] E. N Mohammadi, T. Louwies, C. Pietra, S. R. Northrup, and B. Greenwood-Van Meerveld, “Attenuation of Visceral and Somatic Nociception by Ghrelin Mimetics,” J. Exp. Pharmacol., vol. 12, pp. 267–274, 2020, doi: 10.2147/JEP.S249747.
[vi] J. Svensson et al., “The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats,” J. Endocrinol., vol. 165, pp. 569–77, Jul. 2000.
[vii] N. K. Aagaard et al., “Growth hormone and growth hormone secretagogue effects on nitrogen balance and urea synthesis in steroid treated rats,” Growth Horm. IGF Res., vol. 19, no. 5, pp. 426–431, Oct. 2009, doi: 10.1016/j.ghir.2009.01.001.
