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01-07-2014, 11:26 AM #1
GHRP-2: More than just a GH secretagogue!
GHRP-2 (known as KP-102 as well) has the amino acid sequence: (D-Ala-D-beta-Nal-Ala-Trp-D-Phe-Lys-NH2). GHRP-2 is a ghrelin receptor agonist and a second generation hexapeptide that has very potent growth hormone (GH) releasing action. GHRP2 is a man-made analog of ghrelin and ghrelin is the endogenous ligand for growth hormone secretagogues. GHRP-2 is known to stimulate GH release by acting at both hypothalamic and pituitary sites. It has also been shown to induce adrenocorticotropic hormone (ACTH) release in healthy research test subjects. A "GHRP-2 test" may even be a useful tool for diagnosing secondary adrenal insufficiency or dysfunction such as a hypothalamic disorder or pituitary damage and this use is already starting to be a common trend amongst researchers.
But what the heck is GHRP-2 exactly? Where does it come from?
To get a better understanding of GHRP2 you should know a bit about its "mother" ghrelin, which is a very important compound in the body and not just for growth hormone out-put. Ghrelin and GHRP-2 have been shown to inhibit skeletal muscle proteolysis in rats with burn injuries, but the effects of ghrelin on healing had not been as thoroughly investigated until recently. In a recent study it was shown that the continuous administration of ghrelin over 24 hours "attenuated burn-induced EDL muscle proteolysis, and normalized elevated TNF(alpha); mRNA." Showing us that ghrelin itself is an important factor for other things than just hunger (what most associate ghrelin with) and that it reduces muscle cachexia produced by injury and proinflammatory cytokines and even more importantly ghrelin and its ghrelin-based compounds like GHRP2 can be very useful in treating wasting disorders under various circumstances and in many animal species.
From evolutionary studies done on animals, it has been found that the receptor and hormone have been present for at least hundreds of years. Showing us the evolutionary and functional importance of ghrelin and its related systems. Ghrelin chemical isolation and identification was first accomplished surprisingly enough from the stomach. The stomach is a major site for ghrelin, but not the only site.
The hypothalamus is also another area known for ghrelin concentration. Ghrelin was first isolated and identified by "Kojima and Kangawa et al. in 1999." The main action of GHRP-2 and its research target continues to be aimed at GH secretion and regulation, but ghrelin also has been shown to have various useful actions of its own. It has been shown to have a direct and indirect effect on nutrition and metabolism in animals, along with a few other actions which I will touch on shortly.
From 1973 to present day there have been many discoveries that have taken place regarding the existence of Ghrelin and effects of some of its analogs such as GHRP6 and GHRP2. The main discoveries were the possible isolation of somatostatin and the discovery of GHRP analogs in the early stages of research, which that are man-made and not found naturally in nature. The discovery of GHRP and GHRH synergism when combined in administration during research has also noted many times in research. During early research into GHRP-2 it was quickly noted to have an extremely increased pulsatile GH secretion effect shortly after administration.
GHRP's many positive effects have been noted around the globe thanks to many talented researchers that have looked into its possible benefits. GHRP was first seen as an analog of GHRH but from the comparison of GHRH vs. GHRPs effects between the years 1982 and1984, it was hypothesized to show the activity of a new hormone regulator of GH secretion yet to be isolated and identified. Meaning GHRP's may have an alternate route of biological effect in the body and that they should be considered in a class of their own! Or at least many felt this way, as do I.
GHRPs can have a variable chemistry that consists of three classes; peptides, partial peptides, and non-peptides. They are presumed to act via the same receptor and cellular mechanisms in the body of many animals.
GHRP-2 vs. GHRP-6:
GHRP-2 and GHRP-6 might seem pretty much the same at first glance, but their biological actions are not completely the same. It has been noted that GHRP-6 has a much more profound effect in increasing hunger response in animal research subjects and that although it is still a potent GH secretagogue, it is less effective than that of GHRP-2 in relation to GH output on a mg to mg bases.
In mice and sheep it was found that GHRP-2 (and GRF) "increased intracellular cyclic AMP (cAMP) concentrations and caused GH release in a dose-dependent manner; GHRP-6 did not increase cAMP levels." It was also shown that maximal doses of GRF and GHRP-2 caused both cAMP and GH levels to go up, while the combination of GHRP-6 and GHRP-2 only produced an additive effect on GH release only. Something very interesting to note from this study is that "the additive effect of GRF combined with GHRP-2 or GHRP-6 suggested that the three peptides may act on different receptors. In rat pituitary cell cultures, GHRP-6 had no effect on cAMP levels, but potentiated the effect of GRF on cAMP accumulation." Defiantly showing a synergistic affect which has been noted in various studies already and possibly something to consider when using these compounds for research, especially if maximising GH output is an important factor.
Data like this suggests to me that the differences in the response is probably due to different subtypes of GHRP receptors. It really makes you wonder just how many types of receptors are out there that we may not even know about yet! Very exciting data for sure and it is not the only study to show this difference in effects. Sometimes during early research into a new area of research or compound we stumble upon an undiscovered receptor we use a compound that acts a little "strange" then we expect it to, thus possibly uncovering a new receptor or even a whole new system! GHRP-2 and GHRP-6 might have a lot of similar actions but they are far from the same compound in my opinion.
GHRP-2 for screening dysfunction:
With Growth hormone secretagogues like GHRP-2 we now have a new possible GH deficiency treatment or screening option and this exact use has been increasing exponentially in popularity over the last decade. In a recent study samples from a GHRP-2/GH study corroborated the screening assay applicability with ghrp-2 and was shown to "have a detection window of approximately 4-5 hours." Although the site of GHSs action to induce secretion is not fully understood, it has been shown secretion by ghrelin or GHRP-2 is induced mainly through hypothalamic arginine vasopressin, and that NPY (neuropeptide) mediates the action here as well and that means if there is some sort of dysfunction in this area it may be uncovered with GHRP-2 administration.
There has been many research studies done on GHRP-2 for a magnitude of effects like; antioxidant, muscle building, fat-loss and of course the well-known GH boosting capabilities GHRP-2 has. Blow I will note some good examples of some research done with GHRP-2 and some very interesting findings that have come to light thanks to researchers like you:
Anti-inflammatory effects:
It has been noted recently in research that GHRP-2 has a great anti-inflammatory effect. One example of this in a study was one that used GHRP-2 and focused on liver injury in bacterial endotoxin (lipopolysaccharide=LPS) treated rats. It showed that GHRP2 "prevented an endotoxin-induced increase in transaminases and nitrite/nitrate release as well as in TNF-alpha mRNA along with an increased IGF-I mRNA from cocultures of hepatocytes and nonparenchymal cells." This shows us that GHRP-2 has an effective protective and anti-inflammatory effect on the liver and that this effect is mediated by IGF-I, TNF-alpha, and nitric oxide.
Oral administration:
Although peptides like GHRP-2 have a very poor biological availability and are usually administered via subcutaneous or IV administration, some research was done to find out if it would be an effective feed additive. Experiments were conducted to determine the effects of the administration of GHRP-2 by gavage (force feeding) and in feed on the release of GH in swine to investigate whether attenuation of the GH response occurs after short-term treatment with the peptide. It was found that "Administration of 1 mg/kg BW GHRP-2 to swine in feed failed to stimulate the release of GH, but GHRP-2 at doses of 4.5 and 9 mg/kg BW significantly.- After 3 d of treatment with GHRP-2 in feed at doses of 4.5 and 9 mg/kg BW, GH responses to the peptide were maintained." These results show that the administration of GHRP-2 orally by gavage and in feed can stimulate the release of GH in swine but that higher doses are needed to accomplish this and it is likely not the most viable option.
In other research done in swine the effects GHRP-2 on the release of GH and growth it was shown that a "single intravenous (i. v.) injection of GHRP-2 at doses of 2, 10, 30 and 100 microg/kg body weight (BW) to cross-bred castrated male swine stimulated GH release in a dose-dependent manner, with a return to the baseline by 120 min. The peak GH concentrations and GH areas under the response curves (GH AUCs) for 180 min after the injections of GHRP-2 were higher (P < 0.05) than those after the injection of saline. The GH responses to repeated i.v. injections of GHRP-2 (30 microg/kg BW) at 2-h intervals for 6 h were decreased after each injection. The chronic subcutaneous (s.c.) administration of GHRP-2 (30 microg/kg BW) once daily for 30 days consistently stimulated GH release. The GH AUCs for 300 min after the injections on d 1, 10 and 30 of treatment in GHRP-2-treated swine were higher than those in saline-treated swine. However, chronic administration of GHRP-2 caused a partial attenuation of GH response between d 1 and 10 of treatment. The chronic s.c. administration of GHRP-2 also increased average daily gain for the entire treatment period by 22.35% (P < 0.05) and feed efficiency (feed/gain) by 20.64% (P < 0.01) over the saline control values, but did not significantly affect daily feed intake." This study shows us that GHRP-2 stimulates GH release and does in fact enhance growth performance in swine even if not consuming additional food over the control group and I feel this would apply to other livestock as well.
Controversy?
It is still controversial to some researchers that the stimulation of GH secretion by GHRP-2 requires both GHRP receptor (GHRP-R) and GH-releasing hormone receptor (GHRH-R), but recent research suggests that "GHRH-R is vital for GHRH-induced GH secretion but only partially involved in GHRP-2-stimulated GH secretion under the condition of down-regulation of GHS-R gene transcription." So as mentioned earlier GHRP-2 may act on multiple pathways to induce its many positive effects.
In a rat study GHRP-2 was evaluated for "GH-releasing action under pentobarbital (PB) anesthesia in neonatally sodium-glutamate-monohydrate-treated low growth (NMSG-LG) rats" and it was found that GHRP-2 "potently stimulates the GH release by a direct or indirect antagonism of somatostatin (SRIF) and growth hormone releasing hormone (GHRH) release in the hypothalamus and by a direct action on the pituitary." A study in mice that harbor a ghrelin mutation in the GH-releasing hormone gene was shown to still maintain a "statistically significant growth hormone elevation after administration with GHRP-2." This reflects a direct, GH-independent effect on ghrelin stimulation in the remaining pituitary somatotrophs of mice.
Thermal injury and healing:
Thermal injury can cause a loss of general body weight and cause skeletal muscle wasting. GHRP-2 has been noted for enhancing muscle building capabilities as well as to speed up general healing of various types of wounds. In a recent study using mice and rats, it was shown that along with ghrelin injections stimulating food intake and growth hormone release, it also inhibited skeletal muscle proteolysis in rats with thermal injury. In this same study they also "sought to develop a lower molecular weight, stable and longer acting peptide to combat the catabolic responses caused by thermal injury." And from this they used GHRP-2 as the compound of research and it was shown that "slow in vivo release of GHRP-2 through minipump for 24h showed attenuated thermal injury-induced increase in mRNA in rat skeletal muscle and burn-induced increases in total and myofibrillar protein breakdown from rat EDL muscle were attenuated by GHRP-2." Showing us the effectiveness of GHRP-2 to minimise the catabolic responses resulting from thermal injury and yet again showing us the many protective and healing abilities of GHRP-2.
Antioxidant effect:
GHRP-2 has also been noted to bind to CD36 (a scavenger receptor for oxidized low-density lipoprotein) also known as (OxLDL). In a research aimed to determine its potential antiatherogenic (think anti-plaque) effects, it was shown that GHRP-2 (administered twice daily) for 12 weeks in mice to; "have an increased circulating IGF-1 of 1.2- to 1.6-fold and decreased circulating interferon-gamma by 66%. GHRP-2 was found not to alter atherosclerotic plaque area, but it decreased aortic production of superoxide" thus showing us that GHRP-2 does exert "antioxidant effects but does not reduce plaque burden."
Lung protection:
As mentioned earlier, GHRP-2 exerts beneficial effects on inflammatory issues and in another study looking at lipopolysaccharide-induced acute lung injury in rats it was found that "pretreatment with GHRP-2 markedly suppressed the activation of NF-kappaB in lung tissues." Which indicates that GHRP-2 attenuated LPS-induced injury and it was noted that "early protection appears to be mediated partly through the inhibition of NF-kappaB pathway activation." This study indicates that GHRP-2 can act as a possible therapeutic tool in research for treating acute lung injury and further investigating this is a worthwhile venture.
The heart:
In rabbits it was shown that pretreatment with GHRP-2 on myocardial stunning in a blood-perfused isolated rabbit heart to have "no signs of increased apoptosis" and that at 14 days of pretreatment GHRP-2 "protected selectively against the diastolic dysfunction of myocardial stunning" showing GHRP-2 to have a cardioprotective effect. In hamsters GHRP-2 was studied to Improve left ventricular dysfunction in dilated cardiomyopathic hamsters and that it was shown to "suppress the increase in the level of myocardial oxidative stress, leading to attenuation of progressive LV remodeling and dysfunction in dilated cardiomyopathic hamsters." So it helped protect the heart in this research setting as well.
GHRP-2's GH boosting, antioxidant, protective and muscle building effects are broad across many species and conditions. Although some effect might vary slightly species to species, overall the effects are about the same and well noted in many published research studies. What this allows researchers to do is use a readily available species and even research specific dysfunction that may be noted more common in one species vs. another. GHRP-2 really is an amazing compound and as noted earlier the combination of GRF or a Mod-GRF would have an even greater synergy due to acting in slightly different pathways, optimizing the GH boosting capabilities of both compounds when used in conjunction with each other.
GHRP-2 is a multi-faceted compound, it does not "just boost GH" it has some effects of its own on top of its well-known enhanced healing, fat loss and, protective and antioxidant effects. The GH boosting effects of GHRP-2 are extreme and it is what most researchers use it for, but let***8217;s not forget all the other neat little things about this peptide that makes it such a gem.
We carry only the highest quality peptides from a recombinant DNA (r-DNA) source and not a chemically synthesized source. This matters because for the highest quality and most stable and biologically active peptide it must be made from a r-DNA source! We only offer the highest quality to our researchers!
Check it out >> GHRP-2
Ref:
1) Effects of the administration of growth hormone-releasing peptide-2 (GHRP-2) orally by gavage and in feed on growth hormone release in swine. Phung LT, Sasaki A, Lee HG, Vega RA, Matsunaga N, Hidaka S, Kuwayama H, Hidari H. Effects of the administration of grow... [Domest Anim Endocrinol. 2001] - PubMed - NCBI
2) Is GHRH receptor essential to GHRP-2-induced GH secretion in primary cultured rat pituitary cells?Roh SG, Chen C, Choi KC, Shrestha Y, Sasaki S. Is GHRH receptor essential to GHRP-2-induced G... [Endocrinology. 2002] - PubMed - NCBI
3) The effect of growth hormone-releasing peptide-2 (KP102) administration on plasma insulin -like growth factor (IGF)-1 and IGF-binding proteins in Holstein steers on different planes of nutrition.Lee HG, Vega RA, Phung LT, Matsunaga N, Kuwayama H, Hidari H. The effect of growth hormone-releasin... [Domest Anim Endocrinol. 2000] - PubMed - NCBI
4) Effects of the synthesized growth hormone releasing peptide, KP-102, on growth hormone release in sodium glutamate monohydrate-treated low growth rats. Nakagawa T, Ukai K, Ohyama T, Koida M, Okamura H. Effects of the synthesized growth hormone releasing... [Life Sci. 1996] - PubMed - NCBI
5) Growth hormone releasing peptides: a comparison of the growth hormone releasing activities of GHRP-2 and GHRP-6 in rat primary pituitary cells.Cheng J, Wu TJ, Butler B, Cheng K. Growth hormone releasing peptides: a comparison of ... [Life Sci. 1997] - PubMed - NCBI
6) Attenuation of systemic morphine-induced analgesia by central administration of ghrelin and related peptides in mice.Zeng P, Chen JX, Yang B, Zhi X, Guo FX, Sun ML, Wang JL, Wei J. Attenuation of systemic morphine-induced analgesia ... [Peptides. 2013] - PubMed - NCBI
7) Growth hormone-releasing peptide-2 suppresses vascular oxidative stress in ApoE-/- mice but does not reduce atherosclerosis.Titterington JS, Sukhanov S, Higashi Y, Vaughn C, Bowers C, Delafontaine P. Growth hormone-releasing peptide-2 suppresses ... [Endocrinology. 2009] - PubMed - NCBI
8) Growth hormone releasing peptide-2, a ghrelin agonist, attenuates lipopolysaccharide-induced acute lung injury in rats.Li G, Li J, Zhou Q, Song X, Liang H, Huang L. Growth hormone releasing peptide-2, a ghrel... [Tohoku J Exp Med. 2010] - PubMed - NCBI
9) Growth hormone response to growth hormone-releasing peptide-2 in growth hormone-deficient little mice.Peroni CN, Hayashida CY, Nascimento N, Longuini VC, Toledo RA, Bartolini P, Bowers CY, Toledo SP. Growth hormone response to growth hormon... [Clinics (Sao Paulo). 2012] - PubMed - NCBI
10) Attenuation of systemic morphine-induced analgesia by central administration of ghrelin and related peptides in mice.Zeng P, Chen JX, Yang B, Zhi X, Guo FX, Sun ML, Wang JL, Wei J. Attenuation of systemic morphine-induced analgesia ... [Peptides. 2013] - PubMed - NCBILast edited by RUI-Products; 01-07-2014 at 11:45 AM.
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01-12-2014, 11:42 AM #2
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01-17-2014, 11:06 AM #3
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