GHRP-2, also known as pralmorelin, is a synthetic growth hormone secretagogue, which specifically targets ghrelin (growth hormone receptor). The significance of targeting ghrelin becomes apparent when we see what are its two main effects – growth hormone secretion and meal initiation.
GHRP-2 was a pioneering growth hormone (GH) secretagogue and is currently used to evaluate GH deficiency and secondary adrenal failure.
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GHRP-2 is a synthetic growth hormone secretagogue with a lot of potential. Modern scientific research made a lot of progress in finding the connection between this peptide and its positive effects on muscle growth, immune system regulation, and sleep cycles.
Generally speaking, growth hormone (GH) increases lean body mass, reduces fat mass, and boosts exercise tolerance during long-term sports activities. It also increases maximum oxygen uptake, enhances muscle strength, and improves linear muscle growth.
GHRP-2 belongs to the group of growth hormone-releasing peptides, which are a class of small peptides composed of 4–7 amino acids and include GHRP-1, 2, 4, 5, 6. Their mode of action is based on the imitation of the endogenous hormone ghrelin to induce the secretion of growth hormone (GH) from the pituitary.
According to several studies, GHRP-2 administration significantly increased the myofiber diameter and area of skeletal muscle. Additionally, GHRP-2 greatly enhanced the serum GH and IGF-1 levels and also increased GHR, IGF-1, and IGF-1R mRNA expression in the liver and skeletal muscle.
Furthermore, different types of research have shown that this peptide could enhance the mRNA expression of PI3K, AKt, and mTOR in the skeletal muscle. GHRP-2 administration could speed up growth performance and GH and IGF-1 secretion in cases with growth retardation. Scientists have proven that GHRP-2 could enhance muscle protein deposition mainly by up-regulating the protein synthesis.
Researchers studied the effects of growth hormone-releasing peptide-2 (GHRP-2) on the expressions of Atrogin-1 and MuRF1 in rat muscles for a long time. Application of dexamethasone increased Atrogin-1 mRNA levels in rat muscles. GHRP-2 reduced levels of MuRF1 mRNA independent of dexamethasone.
To clarify the effect of GHRP-2, in different types of studies, scientists used differentiated C2C12 myocytes. Dexamethasone increased Atrogin-1, MuRF1, and mRNA levels in C2C12 myocytes. GHRP-2 weakened dexamethasone-induced expression of them and reduced the level of MuRF1 mRNA. The GHRP-2 effect was connected with GHS-R1a. In conclusion, we can assume that GHRP-2 directly weakens Atrogin-1 and MuRF1 mRNA levels through ghrelin receptors in myocytes.
Chronic arthritis is a very challenging condition and can cause cachexia. Scientists tried using GHRP-2 as a treatment to prevent cachexia and also studied its anti-inflammatory effects.
The goal of the research was to study the effect of the growth hormone-releasing peptide (GHRP-2) in arthritic rats. Rats were administered with GHRP-2, and their condition was monitored further. Results showed that GHRP-2 application improved the external symptoms of arthritis, reducing the arthritis score and the paw volume.
Besides that, circulating IL-6 and nitrites/nitrates were increased by arthritis, and research results showed that GHRP-2 treatment decreased the levels of IL-6. To study whether the GHRP-2 is capable of lowering the level of IL-6 release directly on immune cells, scientists incubated peritoneal macrophage cultures with GHRP-2, the endogenous ligand of the growth hormone (GH) secretagogue receptor. GHRP-2 prevented endotoxin-induced IL-6 and lowered nitrite/nitrate release from macrophages.
According to these studies, GHRP-2 application could have an anti-inflammatory effect in arthritic rats, which seems to be connected by ghrelin receptors directly on immune cells.
Different groups of scientists have worked on studying seven healthy males and the connection between GHRP-2 and their sleep cycles. Results showed that intravenous boluses of GHRP-2 given during sleep increased serum levels of GH, ACTH, and cortisol. Also, the mean time spent in stage 2 sleep was increased without changing slow-wave sleep patterns.
Several other research studied how dosage and way of application affected sleep patterns and compared the sleep-endocrine effects of GHRP-2 in 7 subjects given GHRP-2 orally, in another 7 subjects given GHRP-2 intranasally, and in 9 subjects given this peptide sublingually. Scientists found no specific changes in sleep patterns for any non-intravenous GHRP-2 way of application.
A final study examined sleep cycles in 7 healthy males treated with GHRP-2 and placebo 1 week before or after GHRP-2 application. The scientists observed increases in GH and prolactin levels through the night, as well as ACTH and cortisol levels during the first half of the night. A shorter duration of stage 4 sleep was shown during the first half of the night in patients on GHRP-2, with a slight chance of extension stage 2 sleep during the second half of the night in patients on this peptide.
As an orally active, synthetic growth hormone secretagogue, GHRP-2 shows positive effects on muscle growth, immune system regulation, and sleep cycles.
However, please note that GHRP-2 peptide is available only for research purposes and is not approved for human use. Further research is expected on this peptide, which shows great potential, new applications, and uses.
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