GHRP-6 Research Articles

Rikkunshito Depolarizes Pacemaker Potentials of Cultured Interstitial Cells of Cajal through Ghrelin Receptors in Murine Small Intestine

Background: Rikkunshito has been used to treat gastrointestinal (GI) disorders. The purpose of this study was to investigate the effects of Rikkunshito, a traditional Japanese herbal medicine, on the pacemaker potentials of interstitial cells of Cajal (ICCs) from the small intestines of mice. Methods: We isolated ICCs from the small intestines of mice, and the whole-cell patch-clamp configuration was used to record the pacemaker potentials in cultured ICCs and membrane currents. Results: Rikkunshito depolarized ICC pacemaker potentials in a dose-dependent manner. Pretreatment with GSK1614343 or (D-Lys3)-growth hormone-releasing peptide-6 inhibited Rikkunshito-induced depolarization of pacemaker potentials. Intracellular GDP-β-S inhibited Rikkunshito-induced effects. In Ca²⁺-free solution or in the presence of thapsigargin, Rikkunshito did not depolarize pacemaker potentials. Moreover, in the presence of U-73122 or xestospongin C, Rikkunshito-induced effects were inhibited. However, in the presence of staurosporine, Go6976 or Rottlerin, Rikkunshito depolarized pacemaker potentials. Furthermore, Rikkunshito inhibited both transient receptor potentials melastatin 7 (TRPM7) and Ca²⁺-activated Cl^– channels (ANO1) currents. Conclusion: Rikkunshito depolarized pacemaker potentials of ICCs via ghrelin receptor and G protein through internal or external Ca²⁺-, phospholipase C-, and inositol triphosphate-dependent and protein kinase C-, TRPM7-, and ANO1-independent pathways. The study shows that Rikkunshito may alleviate GI motility disorders through its depolarizing effects on ICCs.

Ghrelin, a Novel Growth Hormone-Releasing Peptide, Inhibits Inflammatory Response and Apoptosis during Ischemic Reperfusion Injury Following Murine Heart Transplantation

Purpose Ghrelin , a novel growth hormone-releasing peptide, has both anti-inflammatory and anti-apoptotic effects on human endothelial cells . Ischemic reperfusion injury (IRI) is a multi-factorial inflammatory condition and an important risk factor for cardiac allograft vasculopathy . We evaluated the protective effects of ghrelin against IRI following murine heterotopic cervical heart transplantation (HCHT). Methods Donor hearts of C57BL/6J mice, which were kept in cold saline for 60 minutes were heterotopically transplanted into C57BL/6J recipients (n = 7 each). A day prior to HCHT, donor animals received ghrelin 300 nmol/kg intraperitoneally or saline (0.3ml). Upon reperfusion and on postoperative day 1, ghrelin or saline was administered. Donor hearts were procured on postoperative day 2. Results Ghrelin injection did not result in any adverse effects on the donors. All animals (n = 7 each) in both groups successfully survived to postoperative day 2. As a measure of apoptosis , TUNEL-positive cells were significantly decreased in the ghrelin groups (0.38±0.21% vs. 5.74±3.68%; p = 0.0004). NF-kB p65 nuclear translocation was also reduced in the ghrelin groups compared to the control (3.17±1.84% vs. 19.28±13.14%; p = 0.0095). VCAM-1 (p = 0.0322), ICAM-1 (p = 0.0484) and NF-kB (p = 0.0130) levels were also significantly reduced in ghrelin-treated groups. No significant difference was observed in oxidative injury, as measured by 8-isoprostane production between groups (47.67±13.14 pg/mg vs. 95.39±28.90 pg/mg; p = 0.1267). Conclusion Ghrelin inhibits the inflammatory response and apoptosis during transplant-related IRI. This study demonstrates the protective effects of ghrelin in IRI following HCHT. A further study is warranted to investigate its long-term effects on donor hearts.

UHPLC-HRMS determination of some human growth hormone-releasing peptides in urine

Wide dissemination of growth hormone-releasing peptides for professional athletes as well as in amateur sports requires constant attention from the law enforcement agencies. However, in addition to examining the seized materials to establish their active components, it is advisable and necessary to control the growth hormone-releasing peptides in the urine at the trace concentration level since the effective doses of the use of growth hormone-releasing peptides are relatively low and the rate of their excretion from the body often does not allow the determination of native compounds and their metabolites even a few days after the administration. A procedure for the measurement of some growth hormone-releasing peptides in the urine using the ultra-high-performance liquid chromatography (UHPLC) in combination with the high-resolution mass spectrometry (HRMS) has been proposed. It was found that the highest sensitivity could be achieved by utilizing the mobile phase consisting of 0.1% solution of trifluoroacetic acid in water and acetonitrile acidified with trifluoroacetic acid (0.1%). The concentration factor using the solid-phase extraction has been established. As it could be seen from the presented data, the highest extraction efficiency was achieved using the cation-exchange sorbents, while the octadecyl sorbent, in fact, was ineffective in this case. The matrix effects were noted not to exceed 15% during the research. The use of HRMS allows for high sensitivity due to the selectivity of the method. Keywords : UHPLC-HRMS, releasing-peptides, doping, mass-spectrometry (Russian) DOI: http://dx.doi.org/10.15826/analitika.2019.23.4.008 A.Z. Temerdashev 1 , E.V. Dmitrieva 1 , A.A. Azaryan 1 , D.A. Burmikin 2 1 Kuban State University, Stavropolskaya st., 149, Krasnodar, 350055, Russian Federation 2 Bruker Ltd., Pyatnitskaya st., 50/2, Moscow, 119017, Russian Federation

Recent improvements in sports drug testing concerning the initial testing for peptidic drugs (< 2kDa) - sample preparation, mass spectrometric detection, and data review.

In this work, a novel initial testing assay based on liquid chromatography-mass spectrometry is presented, enabling the detection of peptidic drugs and drug candidates (< 2kDa) prohibited in sports. The assay covers representatives and metabolites of gonadotropin releasing hormone and its analogs (GnRHs), growth hormone secretagogues (GHS), growth hormone releasing peptides (GHRPs), and the Vasopressin-analog Desmopressin. The general objective of this work was to reduce sample preparation efforts to a minimum while preserving highest possible sensitivity and specificity of the assay, demonstrating limits of detection between 50 and 200pg/mL. Here, a "dilute-and-inject" strategy provides the simplest conceivable sample preparation procedure. Furthermore, the combination of well-established strategies for the determination of peptides, such as two-dimensional liquid chromatography, dimethyl sulfoxide (DMSO)-assisted electrospray ionization, high resolution mass spectrometric detection and a tailored reporter template, which facilitates data review enormously, provides a high-throughput initial testing assay for lower molecular mass peptidic and peptide-related analytes.

Identification of a novel growth hormone releasing peptide (a glycine analogue of GHRP-2) in a seized injection vial.

Growth hormone releasing peptides (GHRPs) are synthetic peptides with the ability to stimulate human growth hormone (hGH) secretion. Several GHRPs have been developed as drug candidates; however, only one of them, GHRP-2 (Pralmorelin), has received a clinical approval. Nevertheless, they are distributed on the black market and misused by cheating athletes, due to their performance-enhancing effects. Hence, GHRPs have been included in the World-Anti-Doping-Agency's Prohibited List as forbidden substances in sport. Predominantly, analytical methods for detection and unequivocal identification of doping substances are based on mass spectrometry. Therefore, in the present work, a qualitative analysis by liquid chromatography coupled to high-resolution tandem mass spectrometry with a quadrupole time-of-flight analyzer was performed to identify a new heptapeptide (MW=874.02Da) - a glycine analogue of GHRP-2. Structure determination using de novo sequencing is described here in detail. The results of this study may indicate a new approach to circumvent a detection of doping practices.

Differential functional selectivity and downstream signaling bias of ghrelin receptor antagonists and inverse agonists.

The ghrelin receptor [growth hormone secretagogue receptor (GHSR)-1a] represents a promising pharmacologic target for the treatment of metabolic disorders, including obesity and cachexia, via central appetite modulation. The GHSR-1a has a complex pharmacology, highlighted by G-protein-dependent and -independent downstream signaling pathways and high basal constitutive activity. The functional selectivity and signaling bias of many GHSR-1a-specific ligands has not been fully characterized. In this study, we investigated the pharmacologic properties of ghrelin, MK-0677, L692,585, and [d-Lys3]-growth hormone-releasing peptide-6 (Dlys), JMV2959, and [d-Arg(1),d-Phe(5),d-Trp(7, 9),Leu(11)]-substance P (SP-analog). We investigated their effect on basal GHSR-1a constitutive signaling, ligand-directed downstream GHSR-1a signaling, functional selectivity, and signaling bias. Dlys behaved as a partial antagonist with a strong bias toward GHSR-1a-β-arrestin signaling, whereas JMV2959 acted as a full unbiased GHSR-1a antagonist. Moreover, the SP-analog behaved as an inverse agonist increasing G-protein-dependent signaling, but only at high concentrations, whereas, at low concentrations, the SP-analog attenuated β-arrestin-dependent signaling. Considering the limited success in the clinical development of GHSR-1a-targeted drugs so far, these findings provide a novel insight into the pharmacologic characteristics of GHSR-1a ligands and their signaling bias, which has important implications in the design of novel, more selective GHSR-1a ligands with predictable functional outcome and selectivity for preclinical and clinical drug development.-Ramirez, V. T., van Oeffelen, W. E. P. A., Torres-Fuentes, C., Chruścicka, B., Druelle, C., Golubeva, A. V., van de Wouw, M., Dinan, T. G., Cryan, J. F., Schellekens, H. Differential functional selectivity and downstream signaling bias of ghrelin receptor antagonists and inverse agonists.

Evaluation of Hypothalamic-Pituitary-Adrenal Axis by the GHRP2 Test: Comparison With the Insulin Tolerance Test.

ContextGH-releasing peptide 2 (GHRP2) stimulates the hypothalamic–pituitary–adrenal axis (HPA) through the GH secretagogue receptor (GHSR) in the hypothalamus, in which ghrelin is a natural ligand. Therefore, the GHRP2 test (GHRP2T) could be used instead of the insulin tolerance test (ITT).ObjectiveCan the GHRP2T replace the ITT for evaluation of HPA?DesignThe present retrospective study analyzed the clinical features and laboratory data from 254 patients admitted for evaluation of hypopituitarism who underwent both GHRP2T and ITT. We analyzed the association between the maximum cortisol level (Fmax) during both tests. Adrenocortical insufficiency was diagnosed by ITT. The suitability of GHRP2T was examined using the receiver operating characteristic curve.ResultsA strong correlation was found between Fmax measured using both tests (r = 0.777, P < 0.0001). However, the sensitivity (64%) and specificity (79%) showed that the GHRP2T was not suitable for clinical use. Various factors influenced the correlation, probably through their effects on ghrelin and/or GHSR, including functional adenoma (P < 0.05) and sex (P < 0.05). No substantial correlation was found between Fmax measured using both tests in patients with prolactinoma (n = 30). The exclusion of patients with functional adenoma revealed no factors that affected the association in male patients; however, age and menstruation significantly influenced it in female patients (P < 0.05). Analysis of the data from male subjects without functional adenoma (n = 104) showed high sensitivity (95%) and specificity (85%) for the GHRP2T.ConclusionITT can be substituted with GHRP2T for assessment of HPA in male patients free of functional adenoma.

The CD36-PPARγ Pathway in Metabolic Disorders.

Uncovering the biological role of nuclear receptor peroxisome proliferator-activated receptors (PPARs) has greatly advanced our knowledge of the transcriptional control of glucose and energy metabolism. As such, pharmacological activation of PPARγ has emerged as an efficient approach for treating metabolic disorders with the current use of thiazolidinediones to improve insulin resistance in diabetic patients. The recent identification of growth hormone releasing peptides (GHRP) as potent inducers of PPARγ through activation of the scavenger receptor CD36 has defined a novel alternative to regulate essential aspects of lipid and energy metabolism. Recent advances on the emerging role of CD36 and GHRP hexarelin in regulating PPARγ downstream actions with benefits on atherosclerosis, hepatic cholesterol biosynthesis and fat mitochondrial biogenesis are summarized here. The response of PPARγ coactivator PGC-1 is also discussed in these effects. The identification of the GHRP-CD36-PPARγ pathway in controlling various tissue metabolic functions provides an interesting option for metabolic disorders.

Analysis of new growth promoting black market products

Detecting agents allegedly or evidently promoting growth such as human growth hormone (GH) or growth hormone releasing peptides (GHRP) in doping controls has represented a pressing issue for sports drug testing laboratories. While GH is a recombinant protein with a molecular weight of 22 kDa, the GHRPs are short (3–6 amino acids long) peptides with GH releasing properties. The endogenously produced GH (22 kDa isoform) consists of 191 amino acids and has a monoisotopic molecular mass of 22,124 Da. Within this study, a slightly modified form of GH was discovered consisting of 192 amino acids carrying an additional alanine at the N-terminus, leading to a monoisotopic mass of 22,195 Da. This was confirmed by top-down and bottom-up experiments using liquid chromatography coupled to high resolution/high accuracy mass spectrometry.Additionally, three analogues of GHRPs were identified as Gly-GHRP-6, Gly-GHRP-2 and Gly-Ipamorelin, representing the corresponding GHRP extended by a N-terminal glycine residue. The structure of these peptides was characterised by means of high resolution (tandem) mass spectrometry, and for Gly-Ipamorelin and Gly-GHRP-2 their identity was additionally confirmed by custom synthesis. Further, established in-vitro experiments provided preliminary information considering the potential metabolism after administration.

Lateral septum growth hormone secretagogue receptor affects food intake and motivation for sucrose reinforcement.

The hormone ghrelin promotes eating and is widely considered to be a hunger signal. Ghrelin receptors, growth hormone secretagogue receptors (GHSRs), are found in a number of specific regions throughout the brain, including the lateral septum (LS), an area not traditionally associated with the control of feeding. Here we investigated whether GHSRs in the LS play a role in the control of food intake. We examined the feeding effects of ghrelin and the GHSR antagonists ([d-Lys3]-growth hormone-releasing peptide-6 and JMV-2959) at doses subthreshold for effect when delivered to the lateral ventricle. Intra-LS ghrelin significantly increased chow intake during the midlight phase, suggesting that pharmacological activation of LS GHSRs promotes feeding. Conversely, GHSR antagonist delivered to the LS shortly before dark onset significantly reduced chow intake. These data support the hypothesis that exogenous and endogenous stimulation of GHSRs in the LS influence feeding. Ghrelin is known to affect motivation for food, and the dorsal subdivision of LS (dLS) has been shown to play a role in motivation. Thus, we investigated the role of dLS GHSRs in motivation for food reward by examining operant responding for sucrose on a progressive ratio (PR) schedule. Intra-dLS ghrelin increased PR responding for sucrose, whereas blockade of LS GHSRs did not affect responding in either a fed or fasted state. Together these findings for the first time substantiate the LS as a site of action for ghrelin signaling in the control of food intake.

Growth hormone-releasing peptide 6 prevents cutaneous hypertrophic scarring: early mechanistic data from a proteome study.

Hypertrophic scars (HTS) and keloids are forms of aberrant cutaneous healing with excessive extracellular matrix (ECM) deposition. Current therapies still fall short and cause undesired effects. We aimed to thoroughly evaluate the ability of growth hormone releasing peptide 6 (GHRP6) to both prevent and reverse cutaneous fibrosis and to acquire the earliest proteome data supporting GHRP6's acute impact on aesthetic wound healing. Two independent sets of experiments addressing prevention and reversion effects were conducted on the classic HTS model in rabbits. In the prevention approach, the wounds were assigned to topically receive GHRP6, triamcinolone acetonide (TA), or vehicle (1% sodium carboxy methylcellulose [CMC]) from day 1 to day 30 post-wounding. The reversion scheme was based on the infiltration of either GHRP6 or sterile saline in mature HTS for 4 consecutive weeks. The incidence and appearance of HTS were systematically monitored. The sub-epidermal fibrotic core area of HTS was ultrasonographically determined, and the scar elevation index was calculated on haematoxylin/eosin-stained, microscopic digitised images. Tissue samples were collected for proteomics after 1 hour of HTS induction and treatment with either GHRP6 or vehicle. GHRP6 prevented the onset of HTS without the untoward reactions induced by the first-line treatment triamcinolone acetonide (TA); however, it failed to significantly reverse mature HTS. The preliminary proteomic study suggests that the anti-fibrotic preventing effect exerted by GHRP6 depends on different pathways involved in lipid metabolism, cytoskeleton arrangements, epidermal cells' differentiation, and ECM dynamics. These results enlighten the potential success of GHRP6 as one of the incoming alternatives for HTS prevention.

Evaluation of growth hormone-releasing peptide-2 for diagnosis of thyrotropin-producing pituitary adenomas.

Thyrotropin (TSH)-producing adenomas are a rare cause of hyperthyroidism and are a type of functional pituitary adenoma. The diagnosis of TSH-producing adenoma is a challenging problem in clinical endocrinology. Since growth hormone-releasing peptide-2 (GHRP-2) fails to induce TSH secretion in normal subjects, the effect of GHRP-2 on TSH levels was therefore examined in patients with TSH-producing adenomas. A total of 5 patients (4 women and 1 man) referred to our departments for further evaluation of pituitary hormones were followed-up using the GHRP-2, TSH-releasing hormone (TRH), octreotide, and bromocriptine tests to examine and evaluate TSH secretory dynamics in TSH-producing adenomas. Of 5 patients, 2 (40%) showed such a significant response, defined as a >50% increase in serum TSH level above baseline in the GHRP-2 test. Additionally, 1 patient showed a 48% increase in serum TSH level. In 1 patient whose adenoma was completely removed, basal serum concentrations of TSH were sufficiently suppressed after the operation, and serum TSH levels failed to increase in response to GHRP-2 administration. In 4 patients (80%), a poor response of serum TSH levels was observed in the TRH test. In 2 out of 5 patients (40%), serum TSH levels were significantly decreased following octreotide administration. No patient demonstrated a significant response to the bromocriptine test. In addition to TRH test, the GHRP-2 test as a potential diagnostic tool for TSH-producing pituitary adenomas.

Postoperative growth hormone dynamics in clinically nonfunctioning pituitary adenoma.

Growth hormone deficiency (GHD) is an endocrine disorder characterized by insufficient production of growth hormone (GH). Non-functioning pituitary adenoma (NFPA) is one of common causes of GHD. Although most patients with NFPA have transsphenoidal surgery, the time-dependent changes in GH after operation have yet to be investigated. In this study, we analyzed patients with NFPAs that underwent transsphenoidal surgery. Postoperatively, GH secretion was evaluated in response to GH-releasing peptide-2 (GHRP2) infusion. We also investigated how several factors affected GH dynamics. Of 119 patients analyzed, 94 (79.0%) had peak GH levels less than 9.0 ng/mL and were diagnosed with severe GHD (sGHD) immediately after surgery. Of those patients, 27 (28.7%) recovered from sGHD within 1-2 years after surgery. Univariate analyses confirmed that sGHD recovery improved significantly in patients that were younger, had only undergone a single primary surgery, had not had anterior hormone deficiency except GH, and had cystic adenoma or normal insulin-like growth factor-1 (IGF1) standard deviation score (SD-S) levels immediately after surgery. Multivariate analyses confirmed that younger age and absence of hormone replacement therapy significantly predicted sGHD recovery within 1-2 years after surgery. Taken together, our results indicated that postoperative sGHD should be assessed by GHRP2 infusion, regardless of IGF1 SD-S levels. Furthermore, recovery from sGHD occurs more frequently at 1-2 years after surgery especially in younger patients and/or those with GH deficiency alone. These patients, therefore, should be reassessed for GHD by appropriate tests including GHRP2 test at 1-2 years after surgery.

Influences of Histidine-1 and Azaphenylalanine-4 on the Affinity, Anti-inflammatory, and Antiangiogenic Activities of Azapeptide Cluster of Differentiation 36 Receptor Modulators.

Azapeptide analogues of growth hormone releasing peptide-6 (GHRP-6) exhibit promising affinity, selectivity, and modulator activity on the cluster of differentiation 36 receptor (CD36). For example, [A1, azaF4]- and [azaY4]-GHRP-6 (1a and 2b) were previously shown to bind selectively to CD36 and exhibited respectively significant antiangiogenic and slight angiogenic activities in a microvascular sprouting assay using choroid explants. The influences of the 1- and 4-position residues on the affinity, anti-inflammatory, and antiangiogenic activity of these azapeptides have now been studied in detail by the synthesis and analysis of a set of 25 analogues featuring Ala1 or His1 and a variety of aromatic side chains at the aza-amino acid residue in the 4-position. Although their binding affinities differed only by a factor of 17, the analogues exhibited significant differences in ability to modulate production of nitric oxide (NO) in macrophages and choroidal neovascularization.

Growth hormone releasing peptide-6 enhanced antibody titers against subunit antigens in mice (BALB/c), tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus).

Modern subunit vaccines have excellent safety profiles and improved tolerability, but do not elicit strong immune responses without the addition of adjuvants. Developing a safe and affective adjuvant remains a challenge for peptide-based vaccine design. Growth Hormone Releasing Peptide-6 (GHRP-6) is one of the earliest-developed, synthetic, peptidyl growth hormone secretagogue receptor agonists. These compounds mimic the effect of the endogenous ligand, ghrelin. In the present study, we evaluated the ability of GHRP-6 to enhance the humoral immune response against co-injected antigens in mice, tilapia and African catfish. This peptide was able to increase the antigen-specific antibody response using heterologous proteins and peptides as antigens, which were also formulated in "water in oil" emulsions (Freund and Montanide). As long as we know there is no previous report describing any ghrelin analogous as molecular immunomodulator stimulating a humoral immune response. Further studies will be conducted to evaluate the functionality of this humoral immune response in challenge trials.

Long-term treatment with the ghrelin receptor antagonist [d-Lys3]-GHRP-6 does not improve glucose homeostasis in nonobese diabetic MKR mice.

Long-term treatment with the ghrelin receptor antagonist [d-Lys3]-GHRP-6 does not improve glucose homeostasis in nonobese diabetic MKR mice. Am J Physiol Regul Integr Comp Physiol 314: R71-R83, 2018. First published September 13, 2017; doi: 10.1152/ajpregu.00157.2017 .-Ghrelin secretion has been associated with increased caloric intake and adiposity. The expressions of ghrelin and its receptor (GHS-R1a) in the pancreas has raised the interest about the role of ghrelin in glucose homeostasis. Most of the studies showed that ghrelin promoted hyperglycemia and inhibited insulin secretion. This raised the interest in using GHS-R1a antagonists as therapeutic targets for type 2 diabetes. Available data of GHS-R antagonists are on a short-term basis. Moreover, the complexity of GHS-R1a signaling makes it difficult to understand the mechanism of action of GHS-R1a antagonists. This study examined the possible effects of long-term treatment with a GHS-R1a antagonist, [d-Lys3]-growth hormone-releasing peptide (GHRP)-6, on glucose homeostasis, food intake, and indirect calorimetric parameters in nonobese diabetic MKR mice. Our results showed that [d-Lys3]-GHRP-6 (200 nmol/mouse) reduced pulsatile growth hormone secretion and body fat mass as expected but worsened glucose and insulin intolerances and increased cumulative food intake unexpectedly. In addition, a significant increase in blood glucose and decreases in plasma insulin and C-peptide levels were observed in MKR mice following long-term [d-Lys3]-GHRP-6 treatment, suggesting a direct inhibition of insulin secretion. Immunofluorescence staining of pancreatic islets showed a proportional increase in somatostatin-positive cells and a decrease in insulin-positive cells in [d-Lys3]-GHRP-6-treated mice. Furthermore, [d-Lys3]-GHRP-6 stimulated food intake on long-term treatment via reduction of proopiomelanocortin gene expression and antagonized GH secretion via reduced growth hormone-releasing hormone gene expression in hypothalamus. These results demonstrate that [d-Lys3]-GHRP-6 is not completely opposite to ghrelin and may not be a treatment option for type 2 diabetes.

Growth Hormone Secretagogue Treatment in Hypogonadal Men Raises Serum Insulin-Like Growth Factor-1 Levels.

Realizing the reported misuse of human growth hormone (GH), investigation of a safe alternative mechanism for increasing endogenous GH is needed. Several GH secretagogues are available, including GH-releasing peptides (GHRPs) GHRP-2 and GHRP-6, and the GH-releasing hormone analog, sermorelin (SERM). Insulin-like growth factor 1 (IGF-1) serves as a surrogate marker for GH. Here, the effect of GHRP/SERM therapy on IGF-1 levels is evaluated. A retrospective review of medical records was performed for 105 men on testosterone (T) therapy seeking increases in lean body mass and fat loss who were prescribed 100 mcg of GHRP-6, GHRP-2, and SERM three times daily. Compliance with therapy was assessed, and 14 men met strict inclusion criteria. Serum hormone levels of IGF-1, T, free T (FT), estradiol (E), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were evaluated. Mean (SD) age of the cohort was 33.2 (2.9) years, and baseline IGF-1 level was 159.5 (26.7) ng/mL. Mean (SD) duration of continuous GHRP/SERM treatment was 134 (88) days. Mean posttreatment IGF-1 level was 239.0 (54.6) ng/mL (p < .0001). Three of the 14 men were on an aromatase inhibitor and/or tamoxifen prior to treatment and another 4 men were coadministered an aromatase inhibitor and/or tamoxifen during treatment. Inhibition of E production or estrogen receptor blockade resulted in smaller increases in IGF-1 levels. GHRP/SERM therapy increases serum IGF-1 levels with strict compliance to thrice-daily dosing. The results suggest that combination therapy may be beneficial in men with wasting conditions that can improve with increased GH secretion.

A polypeptide-mediated synthesis of green fluorescent gold nanoclusters for Fe3+ sensing and bioimaging

In this paper, growth hormone releasing peptide-6 (GHRP-6) is a bioactive polypeptide and acts as the reducing agent and capping ligand for synthesis of bright green fluorescent gold nanoclusters (GHRP-6-Au NCs) by a simple and environmental-friendly aqueous method, with the assistance of NaBr as the fluorescent sensitizer. The obtained GHRP-6-Au NCs had high fluorescent quantum yield (10.7%), and the fluorescence was strongly quenched by the existence of trace Fe3+. Thus, a new and highly sensitive sensor for the assay of Fe3+ was constructed based on the analyte-induced fluorescent quenching mechanism. The sensor had a low detection limit of 1.4µM (S/N=3) and a wide linear range of 2–1000µM. Besides, GHRP-6-Au NCs exhibited low cytotoxicity and high biocompatibility for cell imaging.

Hexarelin, a Growth Hormone Secretagogue, Improves Lipid Metabolic Aberrations in Nonobese Insulin-Resistant Male MKR Mice.

Despite the occurrence of dyslipidemia and its contribution to the development of insulin resistance in obese subjects, a growing number of studies have described abnormal lipid profiles among leaner persons. For example, individuals with an abnormal paucity or distribution of fat (lipodystrophy) develop severe insulin resistance, dyslipidemia, and hepatic steatosis. Deranged adipocyte metabolism and differentiation contribute to ectopic fat deposition and consequent development of insulin resistance. Growth hormone (GH) therapy has been shown to correct body composition abnormalities in some lipodystrophy patients. However, little is known about the effects of GH-releasing peptides in this regard. Hexarelin, a GH secretagogue, has recently been shown to have beneficial effects on fat metabolism via the CD36 receptor. In this study, the effects of twice daily intraperitoneal injections of hexarelin (200 μg/kg body weight) were examined in nonobese insulin-resistant MKR mice and corresponding wild-type FVB mice for 12 days. Hexarelin treatment significantly improved glucose and insulin intolerance and decreased plasma and liver triglycerides in MKR mice. These beneficial metabolic effects could be due to the improved lipid metabolism and enhanced adipocyte differentiation of white adipose tissue with hexarelin treatment. Interestingly, although food intake of hexarelin-treated MKR mice was significantly increased, this did not change total body weight. Moreover, hexarelin treatment corrected the abnormal body composition of MKR mice, as demonstrated by a decrease in fat mass and an increase in lean mass. Our results suggest a possible application of hexarelin in treatment of lipid disorders associated with the metabolic syndrome.

Laparoscopic Sleeve Gastrectomy Resolves Low GHRP-2-Stimulated Growth Hormone Levels in Obese Patients.

Because growth hormone (GH) secretion is reportedly decreased in obese patients, we examined not only the factors associated with the decreased GH secretion but also GH response to the GH-releasing peptide (GHRP)-2-load test before and after laparoscopic gastrectomy (LSG). The study comprised 28 individuals aged 19-65years [mean body mass index (BMI), 39.4±9.4kg/m2]. In the univariate analysis, GH secretion peaks correlated negatively with BMI (r=-0.59, p=0.001), visceral adipose tissue (r=-0.47, p=0.005), and subcutaneous adipose tissue (r=-0.40, p=0.04). In the two obese patients, the response to the GHRP-2-load test markedly improved by weight loss 12months after LSG. In conclusion, GH secretion was decreased in obese patients and improved by LSG.