GHRP-2 (10mg)

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]

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References