GHRP-2 (10mg)

Description

GHRP-2 Peptide

GHRP-2, also known as Pralmorelin (also available in 5mg), is a synthetic growth hormone secretagogue that interacts with the ghrelin/growth hormone secretagogue receptor. It is a research peptide studied to evaluate growth hormone deficiency and secondary adrenal failure. GHRP-2, a pentapeptide composed of five amino acids, is similar in structure to the naturally occurring neurotransmitter met-enkephalin. However, it seems that GHRP-2 does not exhibit properties typical of neurotransmitters. Instead, it is thought to potentially interact with ghrelin receptors. Ghrelin, classified as an appetite-regulating hormone, may potentially be influenced by GHRP-2. It is suggested that this peptide may stimulate the production of growth hormone (GH) by potentially engaging with ghrelin receptors located on the pituitary gland, known as growth hormone secretagogue receptors (GHS-Rs). This interaction, however, remains speculative. Extensive research has also evaluated its role in regulating muscle cell development, the immune system, and sleep cycles.[1]

Specifications

Other Known Titles: Thymosin Beta 4

Molecular Formula: C45H55N9O6

Molecular Weight: 817.9 g/mol

Sequence: H-D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2

GHRP-2 Research

GHRP-2 and the Pituitary Gland

The primary action of GHRP-2 seems to be linked to its interaction with Growth Hormone Secretagogue Receptors (GHS-Rs), which are activated by ghrelin. These receptors are distributed in various parts of the nervous system and other tissues, including the hypothalamus and pituitary gland. It is suggested that when GHRP-2 binds to GHS-Rs, it might induce a structural change that initiates a series of intracellular signals, often mediated by G-proteins. This interaction may lead to the release of Gαq/11, a G-protein component, which may trigger further signaling events. For instance, Phospholipase C (PLC) might cleave phosphatidylinositol 4,5-bisphosphate (PIP2) into secondary messengers, IP3 and DAG (diacylglycerol). IP3 is believed to stimulate the release of calcium ions, whereas DAG may activate Protein Kinase C (PKC), thereby enhancing the signaling pathway and aiding in the secretion of growth hormone from the pituitary cells. The process might also involve the activation of cyclic AMP (cAMP), which is considered crucial for cellular signaling. An increase in cAMP levels may amplify the signaling cascade, possibly promoting the synthesis of growth hormone in the somatotroph cells of the anterior pituitary gland. However, it is theorized that GHRP-2 may cause immediate desensitization at these receptors after exposure, potentially reducing their sensitivity for up to four hours before this action reverses.[2]

GHRP-2 Peptide and Growth Hormone Synthesis

Researchers have suggested that GHRP-2 may lead to a greater increase in GH levels when introduced to somatotroph cells than the increase physiologically triggered by growth hormone-releasing hormone (GHRH). There is also some indication that GHRP-2 might raise ACTH and cortisol levels, which may also be produced by pituitary cells. Further research indicates that in laboratory settings, GHRP-2 exposure might result in a notable enhancement in peak GH levels and mean pulsatile GH secretion from anterior pituitary gland cells. It could also potentially increase the activity of mediators involved in the anabolic actions of GH, such as insulin-like growth factor-1 (IGF-1). In one study, GHRP-2 was implicated in causing up to an 181-fold surge in GH production from anterior pituitary cells compared to baseline.[3] Furthermore, IGF-1 levels reportedly rose from an average of 100mcg/l at baseline to about 180mcg/l, as reported by the scientists in another experiment. The second team of researchers also reported that this was an apparent consequence of the peptide, which was reported to have “stimulated pulsatile, rhythmic, and entropic GH secretion by more than 3-fold” compared to GHRH.[4]

GHRP-2 and Muscle Structure

Research in yaks noted that GHRP-2 peptide may have potentially stimulated the growth of muscles in two ways: enhanced protein synthesis and accumulation, and reduced protein degradation.[5] The study suggested that GHRP-2 may help overcome natural growth limitations in yaks due to food deprivation, adverse environmental conditions, and disease. The researchers also posited that “GHRP-2 enhanced muscle protein deposition mainly by up-regulating the protein synthesis pathways.” The most significant observation has been the potential action of GHRP-2 in reducing muscle atrophy through repression of atrogin-1 and MuRF1- proteins, which regulate muscle degradation pathways.

GHRP-2 and the Heart

Studies in fetal heart cell culture lines have theorized that GHRP-2 and its analogs (GHRP-1 and GHRP-6) may help to protect cardiac cells by minimizing apoptosis or programmed cell death.[6] The peptide appears to protect cardiac muscles from a reduced supply of blood and nutrients, which may induce cardiac arrest. Studies on Hexarelin, a GHRP-2 analog, have posited that these peptides associate with a specific receptor. More specifically, it is hypothesized that the receptor CD36 may play a significant role in capturing oxidized low-density lipoprotein (OxLDL). This potential interaction between GHRP-2 and CD36 might reduce the cellular uptake of OxLDL, which is believed to contribute to the development of reduced blood supply and nutrients due to atherosclerosis. The research suggests that GHRP-2 may reduce interferon-gamma levels by 66% in cultured aortic smooth muscle cells, a test model for reduced blood and nutrient levels. While the introduction of GHRP-2 did not appear to have significantly changed the extent of atherosclerotic plaque coverage, researchers suggested that it may have lowered superoxide production in the blood vessels. Moreover, GHRP-2 reportedly reduced the gene expression of 12/15-lipoxygenase by approximately 92% and also decreased the expressions of interferon-gamma and macrophage migration inhibitory factors. Observations in cultured aortic smooth muscle cells suggest that GHRP-2 might inhibit the production of peroxides induced by OxLDL, prevent the suppression of the IGF-I receptor, and possibly block apoptosis. In macrophages exposed to OxLDL, GHRP-2 was speculated to diminish lipid accumulation, further highlighting its potential antioxidative and protective actions against a reduced supply of blood and nutrients.[6]

GHRP-2 and the Immune System

GHRP-2 peptide researchers suggest the peptide may enhance the functions of the thymus, an organ considered to protect and mature certain cells of the immune system, especially the T lymphocytes.[7] T lymphocytes are considered crucial for adaptive immunity and the organism’s capacity to combat complex infections. However, the efficacy of the thymus diminishes over time, which may lead to tissue damage and diminished immunity. In such cases, GHRP-2 appears to have the potential to rejuvenate the thymus, possibly promoting the number and diversity of T-cells and also boosting general immunity.

GHRP-2 and Pain Perception

Researchers initially hypothesized that GHRP-2 may decrease pain associated with osteoarthritis in animal models through the stimulation of growth hormone production and the repair of damaged tissues. It has been suggested that GHRP-2 may induce pain relief before tissue repair, which may occur due to an action on opioid receptors. There are four known opioid receptors.[8] Other compounds studied for their impact on opioid receptors may typically mediate a universal action on all four receptors. This generic mode of action may create challenges as the receptors may have differential and diverse functions. GHRP-2 appears to be a selective opioid receptor agonist, binding uniquely to the receptors implicated in pain perception, reward system linking, and sedation.

GHRP-2 and Sleep Cycles

GHRP-2 has been suggested to influence sleep cycles. The peptide may increase the duration of stages 3 and 4 of the sleep cycles by up to 50%, as reported by researchers, as well as potentially improve the duration of REM sleep by approximately 20%.[9] It may further diminish deviation in sleeping patterns from “normal sleep.” Research is ongoing.

GHRP-2 and Appetite

It appears that by activating GHS-Rs in various parts of the nervous system, GHRP-2 may initiate a cascade of cellular processes, which may enhance the production of hunger-stimulating neuropeptides, specifically Neuropeptide Y (NPY) and Agouti-related peptide (AgRP). These peptides are considered vital for managing energy balance and appetite control. Concurrently, it is suggested that GHRP-2 may also reduce the release of melanocyte-stimulating hormone (α-MSH), an appetite-suppressant hormone, potentially leading to increased hunger and greater food consumption. Additionally, GHRP-2 might influence the mesolimbic reward system, a brain pathway important for regulating food cravings, possibly through the activation of GHSR-1a receptors. This mechanism may theoretically amplify appetite, potentially via the activation of cyclic adenosine monophosphate (cAMP) pathways, further implicating GHRP-2 in controlling feeding behavior and reward-driven eating. Research indicates that models tested with GHRP-2 consumed about 36% more food than control models, with a reported increase in food intake relative to body weight. Specifically, the energy intake per kilogram of weight appeared to be higher in the GHRP-2 group, measuring 136.0±13.0 kJ/kg compared to 101.3±10.5 kJ/kg in the control group. Additionally, increases in GH levels were observed in the GHRP-2 models compared to those given saline, with hormone levels measured as the area under the curve (AUC) reaching up to 5550±1090 μg/L/240 min versus 412±161 μg/L/240 min.[10]

Disclaimer: The products mentioned are not intended for human or animal consumption. Research chemicals are intended solely for laboratory experimentation and/or in-vitro testing. Bodily introduction of any sort is strictly prohibited by law. All purchases are limited to licensed researchers and/or qualified professionals. All information shared in this article is for educational purposes only.

References

1. Phung LT, Inoue H, Nou V, Lee HG, Vega RA, Matsunaga N, Hidaka S, Kuwayama H, Hidari H. The effects of growth hormone-releasing peptide-2 (GHRP-2) on the release of growth hormone and growth performance in swine. Domest Anim Endocrinol. 2000 Apr;18(3):279-91. doi: 10.1016/s0739-7240(00)00050-3. PMID: 10793268.
2. Sinha, D. K., Balasubramanian, A., Tatem, A. J., Rivera-Mirabal, J., Yu, J., Kovac, J., Pastuszak, A. W., & Lipshultz, L. I. (2020). Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Translational andrology and urology, 9(Suppl 2), S149–S159. https://doi.org/10.21037/tau.2019.11.30
3. Veldhuis, J. D., Keenan, D. M., Bailey, J. N., Adeniji, A. M., Miles, J. M., & Bowers, C. Y. (2009). Novel relationships of age, visceral adiposity, insulin-like growth factor (IGF)-I and IGF binding protein concentrations to growth hormone (GH) releasing-hormone and GH releasing-peptide efficacies in men during experimental hypogonadal clamp. The Journal of clinical endocrinology and metabolism, 94(6), 2137–2143. https://doi.org/10.1210/jc.2009-0136
4. Bowers, C. Y., Granda, R., Mohan, S., Kuipers, J., Baylink, D., & Veldhuis, J. D. (2004). Sustained elevation of pulsatile growth hormone (GH) secretion and insulin-like growth factor I (IGF-I), IGF-binding protein-3 (IGFBP-3), and IGFBP-5 concentrations during 30-day continuous subcutaneous infusion of GH-releasing peptide-2 in older men and women. The Journal of clinical endocrinology and metabolism, 89(5), 2290–2300. https://doi.org/10.1210/jc.2003-031799
5. Hu R, Wang Z, Peng Q, Zou H, Wang H, Yu X, Jing X, Wang Y, Cao B, Bao S, Zhang W, Zhao S, Ji H, Kong X, Niu Q. Effects of GHRP-2 and Cysteamine Administration on Growth Performance, Somatotropic Axis Hormone and Muscle Protein Deposition in Yaks (Bos grunniens) with Growth Retardation. PLoS One. 2016 Feb 19;11(2):e0149461. doi: 10.1371/journal.pone.0149461. PMID: 26894743; PMCID: PMC4760683.
6. Titterington JS, Sukhanov S, Higashi Y, Vaughn C, Bowers C, Delafontaine P. Growth hormone-releasing peptide-2 suppresses vascular oxidative stress in ApoE-/- mice but does not reduce atherosclerosis. Endocrinology. 2009 Dec;150(12):5478-87. doi: 10.1210/en.2009-0283. Epub 2009 Oct 9. PMID: 19819949; PMCID: PMC2795722.]
7. Chao YN, Sun D, Peng YC, Wu YL. Growth Hormone Releasing Peptide-2 Attenuation of Protein Kinase C-Induced Inflammation in Human Ovarian Granulosa Cells. Int J Mol Sci. 2016 Aug 19;17(8):1359. doi: 10.3390/ijms17081359. PMID: 27548147; PMCID: PMC5000754.
8. Zeng P, Li S, Zheng YH, Liu FY, Wang JL, Zhang DL, Wei J. Ghrelin receptor agonist, GHRP-2, produces antinociceptive effects at the supraspinal level via the opioid receptor in mice. Peptides. 2014 May;55:103-9. doi: 10.1016/j.peptides.2014.02.013. Epub 2014 Mar 4. PMID: 24607724.
9. Sigalos JT, Pastuszak AW. The Safety and Efficacy of Growth Hormone Secretagogues. Sex Med Rev. 2018 Jan;6(1):45-53. doi: 10.1016/j.sxmr.2017.02.004. Epub 2017 Apr 8. PMID: 28400207; PMCID: PMC5632578.
10. Laferrère, Blandine et al. “Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men.” The Journal of clinical endocrinology and metabolism vol. 90,2 (2005): 611-4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2824650/

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Dr. Usman

Dr. Usman (BSc, MBBS, MaRCP) completed his studies in medicine at the Royal College of Physicians, London. He is an avid researcher with more than 30 publications in internationally recognized peer-reviewed journals. Dr. Usman has worked as a researcher and a medical consultant for reputable pharmaceutical companies such as Johnson & Johnson and Sanofi.