GHSR/Growth hormone secretagogue receptor

The pulsatile nature of GH release is apparently regulated by alternating sequential changes in two hypothalamic hormones, GH releasing hormone (GHRH) and somatostatin. Entrainment of this pulsatility appears to involve GH-mediated negative feedback. Recently a new receptor involved in GH release was cloned. Activation of this receptor by GH-releasing peptides and MK-0677 initiates and amplifies GH pulsatility and is associated with increased Fos immunoreactivity and electrical activity in GHRH containing arcuate neurons. We show that pretreating mice with GH blocks activation of these neurons by MK-0677. Similarly, octreotide inhibited the action of MK-0677. To determine whether this GH-mediated negative feedback on GHRH neurons was direct, or by GH stimulation of somatostatin release from periventricular neurons, we selectively inactivated the gene for one of the five specific somatostatin receptor subtypes (subtype 2)[2].

Dogs treated with 5 mg/kg/day of butamoren mesylate gained statistically significant weight and had higher levels of GH and IGF-1 in their serum. On research days 7 or 15, there was no discernible rise in CSF IGF-1 or GH levels due to imitabromen mesylate [1]. Ibutamoren mesylate (50 μg, ip) could not activate these neurons in animals treated with GH prior to treatment. GH and octreotide do not block Ibutamoren mesylate's stimulation of arcuate neurons in gene-knockout mice [2]. Significant increases in GH and IGF-I levels were linked to long-term oral administration of butamoren mesylate, and these effects persisted throughout treatment. After administering ibutamoren mesylate, the GH profile exhibits sporadic elevations over controls [3]. Following oral treatment, ibutamoren mesylate dramatically raises peak GH concentrations. When taken orally or intravenously, ibutamoren mesylate is a strong GH secretagogue that can raise GH levels quickly, significantly, and persistently [4].

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Elevation in circulating GH levels results in a dose-related increase in serum insulin-like growth factor-1 (IGF-1) levels in dogs. However, it is not known whether elevations in systemic IGF-1 and GH levels contribute to the cerebrospinal fluid (CSF) levels of these hormones. Therefore, a study was designed in dogs to determine if elevated circulating GH levels was a result of a GH secretagogue (MK-0677) or if exogenous GH administration resulted in increased IGF-1 and GH levels in the CSF of dogs. A total of 12 normal, young adult male dogs were randomized to three treatment groups (4 dogs/group) based on body weight. There were 4 vehicle control dogs. A group of 4 dogs were dosed orally with MK-0677 (5 mg/kg/day) dissolved in deionized water. A third group of 4 dogs received subcutaneous injections of porcine GH (pGH) at a dose of 0.1 IU/kg/day. From all dogs, blood and CSF samples were collected prior to the initiation of treatment and on days 7 and 15 of treatment. All samples were assayed using a validated radioimmunoassay. Administration of MK-0677 or pGH resulted in a statistically significant (P < or = 0.05) increased body weight gain and increased serum IGF-1 and GH levels. In contrast, administration of MK-0677 resulted in no significant (P > 0.05) increase in CSF IGF-1 or GH levels on days 7 or 15 of the study. The CSF IGF-1 values ranged from 1.2 to 2.0 ng/ml with minimal variation among three separate samples taken during the course of the study from each dog. Similarly, the CSF GH levels were very low (< 0.98 ng/ml to 2.4 ng/ml) in all dogs irrespective of treatment group. This study has demonstrated that there is no correlation between the circulating levels of IGF-1 or GH and the levels of these hormones in the CSF of normal dogs. An approximately 100-fold difference between serum and CSF IGF-1 levels in vehicle control dogs suggest that there is a blood-brain barrier for the circulating IGF-1. Similarly, failure to see an elevation in CSF GH levels despite increases in serum GH levels shows that there is a blood-brain barrier for GH in normal dogs. These results suggest that the likely source of GH and IGF-1 in the CSF of dogs is from the CNS[2].

Compounds used were: MK-0677 (50 μg), octreotide (100 μg), and mGH (30 μg). Mice were give an initial ip injection (0.1 ml) of either saline, octreotide or mGH, followed 10 min later by an ip injection (0.1 ml) of either saline or MK-0677. Thus, the first study comprised of the following groups: saline/saline, saline/MK-0677, mGH/saline, mGH/MK-0677 saline/saline, saline/MK-0677, mGH/saline, mGH/MK-0677, and the second study of: saline/saline, saline/MK-0677, octreotide/saline, octreotide/MK-0677. Additionally, a number of mice were injected ip with hypertonic saline (0.2 ml, 1.5 M) to serve as positive controls for the immunocytochemistry. Ninety minutes after injection animals were terminally anesthetized with sodium pentobarbitone (60 mg/kg; ip) and perfused transcardially with heparinized saline followed by 4% paraformaldehyde in 0.1 M phosphate buffer (PB, pH 7.4). Brains were then removed and placed in the same solution for 24 h before being stored at− 80 C until processing. Coronal sections of forebrain (40 μm) were cut on a freezing microtome and placed in 0.1 M PB containing Triton X-100 (PB-T, pH 7.4). Sections were incubated for 24 h at 4 C in Ab-2 Fos antibody (rabbit polyclonal; 1:1000 in 1% normal sheep serum). The antibody-antigen complex was localized with a 1-h incubation in biotinylated anti-rabbit Ig (1:100), followed by a 1-h incubation in avidin, biotinylated horseradish peroxidase (1:50). The reaction product was visualized using a glucose oxidase-diaminobenzidine-nickel method, and Fos-like immunoreactivity was visualized as a dense purple-black precipitate restricted to the nucleus. The number of c-fos positive nuclei in the arcuate and periventricular nuclei (six to eight sections per mouse) were counted double-blind and a group mean calculated (mean ± SEM). Statistical analysis was performed by a two- way ANOVA followed by an all pairwise multiple comparison of data (Student-Newman-Keuls method) with significance taken as P < 0.05.[1]

[1]. Insulin-like growth factor-1 and growth hormone (GH) levels in canine cerebrospinal fluid are unaffected by GH or GH secretagogue (MK-0677) administration. Horm Metab Res. 1999 Feb-Mar;31(2-3):133-7.

[2]. Somatostatin receptor subtype 2 knockout mice are refractory to growth hormone-negative feedback on arcuate neurons. Mol Endocrinol. 1997 Oct;11(11):1709-17.

[3]. Repeat administration of the GH secretagogue MK-0677 increases and maintains elevated IGF-I levels in beagles. J Endocrinol. 1997 Feb;152(2):183-92.

[4]. MK-0677, a potent, novel, orally active growth hormone (GH) secretagogue: GH, insulin-like growth factor I, and other hormonal responses in beagles. Endocrinology. 1996 Dec;137(12):5284-9.

Ibutamoren Mesylate is the mesylate salt form of ibutamoren, an orally bioavailable, small molecule, non-peptide growth hormone secretagogue (GHS). Upon administration, ibutamoren promotes the release of growth hormone (GH) from the pituitary gland, thereby increasing plasma GH levels. This may counteract GH deficiency. GH plays an important role in many biological processes.
See also: Ibutamoren (has active moiety).

C28H40N4O8S2

624.77

624.228

C, 53.83; H, 6.45; N, 8.97; O, 20.49; S, 10.26

159752-10-0

159752-10-0 (mesylate); 159634-47-6

6450830

White to light yellow solid powder

868.9ºC at 760 mmHg

479.3ºC

3.05E-32mmHg at 25°C

4.974

3

10

8

42

1010

1

CC(C)(C(=O)N[C@H](COCC1=CC=CC=C1)C(=O)N2CCC3(CC2)CN(C4=CC=CC=C34)S(=O)(=O)C)N.CS(=O)(=O)O

DUGMCDWNXXFHDE-VZYDHVRKSA-N

InChI=1S/C27H36N4O5S.CH4O3S/c1-26(2,28)25(33)29-22(18-36-17-20-9-5-4-6-10-20)24(32)30-15-13-27(14-16-30)19-31(37(3,34)35)23-12-8-7-11-21(23)27;1-5(2,3)4/h4-12,22H,13-19,28H2,1-3H3,(H,29,33);1H3,(H,2,3,4)/t22-;/m1./s1

2-amino-2-methyl-N-[(2R)-1-(1-methylsulfonylspiro[2H-indole-3,4'-piperidine]-1'-yl)-1-oxo-3-phenylmethoxypropan-2-yl]propanamide;methanesulfonic acid

Ibutamoren mesylate; 159752-10-0; MK-677; Ibutamoren mesilate; Crescendo; Ibutamoren (Mesylate); MK-0677; MK 0677;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O: ≥ 50 mg/mL (80.03 mM)
DMSO: 50 mg/mL (80.03 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.00 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (4.00 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (4.00 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 100 mg/mL (160.06 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)