Growth hormone-releasing hormone antagonists counteract interferon-γ - induced barrier dysfunction in bovine and human endothelial cells.

GHRH regulates the secretion of GH from the anterior pituitary gland. An emerging body of evidence suggests that the activities of that neuropeptide are not limited to the GH/IGF-I axis, but they expand towards the mediation of inflammatory processes. GHRHAnt were developed to oppose the activities of GHRH in malignancies, and have been associated with strong anti-inflammatory and anti-oxidative effects in a diverse variety of tissues, including the lungs. In the present study we report that GHRHAnt oppose interferon-γ - induced paracellular hyperpermeability and reactive oxygen species generation in bovine and human pulmonary endothelial cells; and suppress interferon-γ - triggered STAT3, cofilin and ERK1/2 activation. Our observations substantiate previous findings on the protective effects of GHRHAnt in endothelial inflammation and barrier break-down.

Growth Hormone Secretagogues as Potential Therapeutic Agents to Restore Growth Hormone Secretion in Older Subjects to Those Observed in Young Adults.

The discovery of the growth hormone secretagogues (GHS) and the reverse pharmacology leading to the discovery of GHS receptor which enabled the identification of ghrelin as the natural ligand for the receptor have opened a new horizon in growth hormone (GH) physiology, pathophysiology, and therapeutics. Major progress has been made and we now have orally active GHS which are able to restore optimal pulsatile GH secretion which cannot be overstimulated as insulin-like growth factor feedback regulates the peaks to the optimum level. This enables GH to be restored in the older to levels normally seen in 20- to 30-year-old people; this leads to an increase in fat-free mass and redistribution of fat to the limbs. As these agents are ultimately approved and investigated further, it is likely that they will be shown to restore growth in children with moderate-to-mild GH deficiency; their benefits will be investigated in other indications such as nonalcoholic fatty liver disease, frailty, anemia, osteoporosis, and immune compromise in older subjects. The exquisite regulation of GH secretion reflects the importance of GH pulsatility in the regulation of somatotroph action of GH.

Growth hormone-releasing hormone antagonists counteract hydrogen peroxide - induced paracellular hyperpermeability in endothelial cells.

Growth Hormone-Releasing Hormone (GHRH) is a hypothalamic peptide which regulates the release of Growth Hormone from the anterior pituitary gland, and has been involved in inflammatory processes. On the other hand, GHRH antagonists (GHRHAnt) were developed to counteract those effects. Herein we demonstrate for the first time that GHRHAnt can suppress hydrogen peroxide (H2O2) - induced paracellular hyperpermeability in bovine pulmonary artery endothelial cells. Increased production of reactive oxygen species (ROS) and barrier dysfunction have been associated with the development of potentially lethal disorders, including sepsis and acute respiratory distress syndrome (ARDS). Our study supports the protective actions of GHRHAnt in the impaired endothelium, and suggests that those compounds represent an exciting therapeutic possibility towards lung inflammatory disease.

Growth hormone-releasing hormone antagonists protect against hydrochloric acid-induced endothelial injury in vitro.

Growth hormone-releasing hormone (GHRH) regulates the synthesis of growth hormone from the anterior pituitary gland, and it is involved in inflammatory responses. On the other hand, GHRH antagonists (GHRHAnt) exhibit the opposite effects, resulting in endothelial barrier enhancement. Exposure to hydrochloric acid (HCL) is associated with acute and chronic lung injury. In this study, we investigate the effects of GHRHAnt in HCL-induced endothelial barrier dysfunction, utilizing commercially available bovine pulmonary artery endothelial cells (BPAEC). Cell viability was measured by utilizing 3-(4,5-dimethylthiazol2-yl)- 2,5-diphenyltetrazolium bromide (MTT) assay. Moreover, fluorescein isothiocyanate (FITC)-dextran was used to assess barrier function. Our observations suggest that GHRHAnt exert protective effects against HCL-induced endothelial breakdown, since those peptides counteract HCL-triggered paracellular hyperpermeability. Based on those findings, we propose that GHRHAnt represent a new therapeutic approach towards HCL-induced endothelial injury.

The influence of a synthetic growth hormone-releasing hormone analogue G11 and opioid peptide biphalin on selected fibroblasts parameters relevant to wound healing.

The treatment of hard-to-heal chronic wounds is still a major medical problem and an economic and social burden. In this work, we examine the proregenerative potential of two peptides, G11 (a trypsin-resistant analogue of growth hormone-releasing hormone [GHRH]) and biphalin (opioid peptide), and their combination in vitro on human fibroblasts (BJ). G11, biphalin and their combination exhibited no toxicity against BJ cells. On the contrary, these treatments significantly stimulated proliferation and migration of fibroblasts. Under inflammatory conditions (LPS-induced BJ cells), we noticed that the tested peptides decreased the levels of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and interleukin 1ß (IL-1ß). This was correlated with diminished phosphorylation levels of p38 kinase, but not those of ERK1/2. We found also that G11, biphalin and their combination activated the ERK1/2 signalling pathway, which has been previously implicated in promigratory activity of some regeneration enhancers, including opioids or GHRH analogues. Potential application of their combination requires further work, in particular in vivo experiments, in which the organism-level relevance of the discussed cell-level effects would be proven and, additionally, analgesic action of the opioid ingredient could be quantified.

Protective effects of GHRH antagonists against hydrogen peroxide-induced lung endothelial barrier disruption.

PURPOSE: Growth hormone-releasing hormone (GHRH) is a hypothalamic hormone, which regulates growth hormone release from the anterior pituitary gland. GHRH antagonists (GHRHAnt) are anticancer agents, which also exert robust anti-inflammatory activities in malignancies. GHRHAnt exhibit anti-oxidative and anti-inflammatory effects in vascular endothelial cells, indicating their potential use against disorders related to barrier dysfunction (e.g. sepsis). Herein, we aim to investigate the effects of GHRHAnt against lung endothelial hyperpermeability. METHODS: The in vitro effects of GHRHAnt in H2O2-induced endothelial barrier dysfunction were investigated in bovine pulmonary artery endothelial cells (BPAEC). Electric cell-substrate impedance sensing (ECIS) was utilized to measure transendothelial resistance, an indicator of barrier function. RESULTS: Our results demonstrate that GHRHAnt protect against H2O2-induced endothelial barrier disruption via P53 and cofilin modulation. Both proteins are crucial modulators of vascular integrity. Moreover, GHRHAnt prevent H2O2 - induced decrease in transendothelial resistance. CONCLUSIONS: GHRHAnt represent a promising therapeutic intervention towards diseases related to lung endothelial hyperpermeability, such as acute respiratory distress syndrome - related or not to COVID-19 - and sepsis. Targeted medicine for those potentially lethal disorders does not exist.

Expression of Growth Hormone-Releasing Hormone and Its Receptor Splice Variants in Primary Human Endometrial Carcinomas: Novel Therapeutic Approaches.

Antagonists of growth hormone-releasing hormone (GHRH) inhibit the growth of various tumors, including endometrial carcinomas (EC). However, tumoral receptors that mediate the antiproliferative effects of GHRH antagonists in human ECs have not been fully characterized. In this study, we investigated the expression of mRNA for GHRH and splice variants (SVs) of GHRH receptors (GHRH-R) in 39 human ECs and in 7 normal endometrial tissue samples using RT-PCR. Primers designed for the PCR amplification of mRNA for the full length GHRH-R and SVs were utilized. The PCR products were sequenced, and their specificity was confirmed. Nine ECs cancers (23%) expressed mRNA for SV1, three (7.7%) showed SV2 and eight (20.5%) revealed mRNA for SV4. The presence of SVs for GHRH-Rs could not be detected in any of the normal endometrial tissue specimens. The presence of specific, high affinity GHRH-Rs was also demonstrated in EC specimens using radioligand binding studies. Twenty-four of the investigated thirty-nine tumor samples (61.5%) and three of the seven corresponding normal endometrial tissues (42.9%) expressed mRNA for GHRH ligand. Our findings suggest the possible existence of an autocrine loop in EC based on GHRH and its tumoral SV receptors. The antiproliferative effects of GHRH antagonists on EC are likely to be exerted in part by the local SVs and GHRH system.

Effect of growth hormone releasing hormone on chondrocytes of osteoarthritis.

BACKGROUND/AIMS: To evaluate the effect and possible mechanism of growth hormone releasing hormone (GHRH) on chondrocytes of osteoarthritis (OA). METHODS: Articular chondrocytes were cultured and the expression of GHRH receptor in chondrocytes was detected. Then recombinant adenovirus GHRH (Ad-GHRH) was transfected to one group of chondrocytes. The expression of collagen type II, matrix metalloproteinase 13 (MMP-13) and signal transducer and activator of transcription 3 (STAT3) in each experimental group was determined by Western blot. RESULTS: The GHRH receptor was expressed in chondrocytes, and this provided a basis for further study of the role of GHRH in chondrocytes. Cell proliferation of the Ad-GHRH group was significantly higher than that of the OA group by CCK-8 assay. Compared with the OA-group, the protein expression of MMP­13 was decreased in the Ad-GHRH group. Compared with the OA-group, the protein expression of collagen type II, phosphorylated STAT3 (P-STAT3) were increased in the Ad-GHRH group. CONCLUSION: Our results show that the GHRH receptor is expressed in chondrocytes. GHRH can promote the proliferation of chondrocytes and the synthesis of type II collagen, and increase the extracellular matrix, which is achieved by phosphorylated STAT3 protein.

Suppression of reactive oxygen species in endothelial cells by an antagonist of growth hormone-releasing hormone.

Growth hormone-releasing hormone (GHRH) is a hypothalamic hormone, which regulates the secretion of growth hormone (GH) from the anterior pituitary gland. The effects of GHRH extend beyond the GH-insulin-like growth factor I axis, and that neuropeptide has been involved in the potentiation of several malignancies and other inflammatory disorders. The development of GHRH antagonists (GHRHAnt) delivers an exciting possibility to counteract the pathogenesis of the GHRH-related effects in human pathophysiology, especially when considered that GHRHAnt support endothelial barrier integrity. Those GHRHAnt-mediated effects are exerted at least in part due to the suppression of major inflammatory pathways, and the modulation of major cytoskeletal components. In the present study, we measured the production of reactive oxygen species (ROS) in bovine pulmonary artery endothelial cells, human cerebral microvascular endothelial cells, and human lung microvascular endothelial cells exposed to GHRH or a commercially available GHRHAnt. Our findings reveal the antioxidative effects of GHRHAnt in all three cell lines, which express GHRH receptors. The redox status of NIH/3T3 cells, which do not produce GHRH receptors, was not significantly affected by GHRH or GHRHAnt. Hence, the application of GHRHAnt in pathologies related to increased ROS production should be further investigated.

Delineating tesamorelin response pathways in HIV-associated NAFLD using a targeted proteomic and transcriptomic approach.

NAFLD is a leading comorbidity in HIV with an exaggerated course compared to the general population. Tesamorelin has been demonstrated to reduce liver fat and prevent fibrosis progression in HIV-associated NAFLD. We further showed that tesamorelin downregulated hepatic gene sets involved in inflammation, tissue repair, and cell division. Nonetheless, effects of tesamorelin on individual plasma proteins pertaining to these pathways are not known. Leveraging our prior randomized-controlled trial and transcriptomic approach, we performed a focused assessment of 9 plasma proteins corresponding to top leading edge genes within differentially modulated gene sets. Tesamorelin led to significant reductions in vascular endothelial growth factor A (VEGFA, log2-fold change - 0.20 ± 0.35 vs. 0.05 ± 0.34, P = 0.02), transforming growth factor beta 1 (TGFB1, - 0.35 ± 0.56 vs. - 0.05 ± 0.43, P = 0.05), and macrophage colony stimulating factor 1 (CSF1, - 0.17 ± 0.21 vs. 0.02 ± 0.20, P = 0.004) versus placebo. Among tesamorelin-treated participants, reductions in plasma VEGFA (r = 0.62, P = 0.006) and CSF1 (r = 0.50, P = 0.04) correlated with a decline in NAFLD activity score. Decreases in TGFB1 (r = 0.61, P = 0.009) and CSF1 (r = 0.64, P = 0.006) were associated with reduced gene-level fibrosis score. Tesamorelin suppressed key angiogenic, fibrogenic, and pro-inflammatory mediators. CSF1, a regulator of monocyte recruitment and activation, may serve as an innovative therapeutic target for NAFLD in HIV. Clinical Trials Registry Number: NCT02196831.

Protective effects of growth hormone-releasing hormone analogs in DSS-induced colitis in mice.

Besides its metabolic and endocrine effects, growth hormone (GH)-releasing hormone (GHRH) is involved in the modulation of inflammation. Recently synthetized GHRH antagonist MIA-690 and MR-409, GHRH agonist, developed by us have shown potent pharmacological effects in various experimental paradigms. However, whether their administration modify resistance to chronic inflammatory stimuli in colon is still unknown. Ex vivo results demonstrated that MIA-690 and MR-409 inhibited production of pro-inflammatory and oxidative markers induced by lipopolysaccharide on isolated mouse colon specimens. In vivo, both MIA-690 and MR-409 have also been able to decrease the responsiveness to nociceptive stimulus, in hot plate test. Additionally, both peptides also induced a decreased sensitivity to acute and persistent inflammatory stimuli in male mice, in formalin test and dextran sodium sulfate (DSS)-induced colitis model, respectively. MIA-690 and MR-409 attenuate DSS-induced colitis with particular regard to clinical manifestations, histopathological damage and release of pro-inflammatory and oxidative markers in colon specimens. Respect to MR-409, MIA-690 showed higher efficacy in inhibiting prostaglandin (PG)E2, 8-iso-PGF2α and serotonin (5-HT) levels, as well as tumor necrosis factor (TNF)-α, interleukin (IL)-6 and nitric oxide synthase gene expression in colon specimens of DSS-induced colitis. Furthermore, MIA-690 decreased serum insulin-like growth factor (IGF)-1 levels in mice DSS-treated, respect to MR-409. Thus, our findings highlight the protective effects of MIA-690 and MR-409 on inflammation stimuli. The higher antinflammatory and antioxidant activities observed with MIA-690 could be related to decreased serum IGF-1 levels.

Mice with an RGS-insensitive Gαi2 protein show growth hormone axis dysfunction.

Mice carrying an RGS-insensitive Gαi2 mutation display growth retardation early after birth. Although the growth hormone (GH)-axis is a key endocrine modulator of postnatal growth, its functional state in these mice has not been characterized. The present study was undertaken to address this issue. Results revealed that pituitary mRNA levels for GH, prolactin (PRL), somatostatin (SST), GH-releasing-hormone receptor (GHRH-R) and GH secretagogue receptor (GHS-R) were decreased in mutants compared to controls. These changes were reflected by a significant decrease in plasma levels of GH, IGF-1 and IGF-binding protein-3 (IGFBP-3). Mutants were also less responsive to GHRH and ghrelin (GhL) on GH stimulation of release from pituitary primary cell cultures. In contrast, they were more sensitive to the inhibitory effect of SST. These data provide the first evidence for an alteration of the functional state of the GH-axis in Gαi2G184S mice that likely contributes to their growth retardation.

"Non-Classical" Indication for Provocative Testing of Growth Hormone: A Retrospective Cohort Study in Adult Patients Under Replacement Therapy.

BACKGROUND: Adult growth hormone deficiency (GHD) is considered a rare condition. Current guidelines state that GH provocative test is indicated in patients affected by organic hypothalamic/ pituitary disease or with a history of head injury, irradiation, hemorrhage or hypothalamic disease with multiple pituitary deficiencies. Nevertheless, the clinical picture related to GHD may be subtle. OBJECTIVE: We have retrospectively evaluated the indication to GHRH+arginine test in our monocentric cohort of patients treated with hrGH in order to assess whether other conditions had been considered as a rationale for provocative testing. METHODS: Ninety-six patients (51 females and 45 males), aged 19-67 years were included. The GHRH+arginine test had been performed in 29 patients with organic hypothalamic/pituitary disease and in 4 patients for Childhood onset-GHD (CoGHD). In other patients, the diagnosis was suspected for "non classical" reasons in the clinical picture suspected for GHD. RESULTS: Classical indications included previously known primary empty sella (n=15), pituitary surgery (n=14), pituitary cyst (n=1), non-secreting pituitary tumors (n=3) but more than half of the patients (57.3%) had been studied for "non classical" indications: metabolic syndrome (n=25), asthenia (n=13), heart failure (n=4), osteoporosis (n=6), unexplained hypoglycaemia (n=1) and infertility (n=6). The latter represented a significant percentage in the male subgroup under 45 ys. IGF-1 levels were lower than 50th percentile in 63% of patients. Finally, among non-classical reasons, organic pituitary disease was discovered in 22 patients. CONCLUSION: Idiopathic GHD may be unrecognized due to its subtle manifestations and that an extended use of dynamic GH tests may reveal such conditions. A potential field of investigation could be to identify subsets of patients with clinical conditions caused or worsened by underlying unrecognized GHD.

The renin secretion profile under the influence of sleep deprivation and the neuropeptides CRH and GHRH.

It is already known that during normal sleep plasma renin activity (PRA) shows oscillations with decreases during rapid-eye-movement (REM) sleep and increases during non-REM (NREM) sleep. We also know that renin correlates positively with slow-wave sleep (SWS). Sleep deprivation is known to enhance significantly SWS and slow wave activity (SWA, known as δ power). Based on these findings we addressed the question whether and to which extent sleep deprivation may affect the synchronization found between PRA and REM sleep during normal sleep and whether this synchronization is affected by other sleep regulating factors. To investigate these questions we compared sleep EEG and sleep-related free renin levels in 48 normal women and men 19-69 years old between nights before and after 40 h of sleep deprivation. During the recovery night, four bolus injections of either GHRH, CRH or placebo were injected via long catheter around sleep onset. When compared to baseline after each of the treatments SWS, SWA and renin levels increased. The characteristical oscillation profiles of renin during normal sleep were also preserved after sleep deprivation. Similar to normal sleep our data support also a distinct link between nocturnal renin secretion and SWS after sleep deprivation and that independent of the applied treatments.

Effects of tesamorelin on hepatic transcriptomic signatures in HIV-associated NAFLD.

Nonalcoholic fatty liver disease (NAFLD) is a common comorbidity among people living with HIV that has a more aggressive course than NAFLD among the general population. In a recent randomized placebo-controlled trial, we demonstrated that the growth hormone-releasing hormone analog tesamorelin reduced liver fat and prevented fibrosis progression in HIV-associated NAFLD over 1 year. As such, tesamorelin is the first strategy that has shown to be effective against NAFLD among the population with HIV. The current study leveraged paired liver biopsy specimens from this trial to identify hepatic gene pathways that are differentially modulated by tesamorelin versus placebo. Using gene set enrichment analysis, we found that tesamorelin increased hepatic expression of hallmark gene sets involved in oxidative phosphorylation and decreased hepatic expression of gene sets contributing to inflammation, tissue repair, and cell division. Tesamorelin also reciprocally up- and downregulated curated gene sets associated with favorable and poor hepatocellular carcinoma prognosis, respectively. Notably, among tesamorelin-treated participants, these changes in hepatic expression correlated with improved fibrosis-related gene score. Our findings inform our knowledge of the biology of pulsatile growth hormone action and provide a mechanistic basis for the observed clinical effects of tesamorelin on the liver.

Growth hormone-releasing hormone promotes therapeutic effects of peripheral blood endothelial progenitor cells in ischemic repair.

PURPOSE: In peripheral artery disease, blockage of the blood supply to the limbs leads to blood flow attenuation and tissue ischemia. We investigated whether growth hormone-releasing hormone (GHRH) could enhance the biological functions and therapeutic effects of endothelial progenitor cells (EPCs) derived from adult human peripheral blood (PB). METHODS: EPCs were isolated from human PB (PB-EPCs) and cord blood and expanded in vitro. PB-EPCs incubated with or without GHRH were evaluated for proliferation, migration, and angiogenesis capacity and apoptosis rates under oxidative stress conditions. Activation of STAT3 and Akt pathways was evaluated using Western blot. A hind-limb ischemia (HLI) mouse model was used to study the efficacy of GHRH in improving EPC therapy in vivo. RESULTS: GHRH enhanced the proliferation, migration, and angiogenesis capacity of PB-EPCs and reduced apoptosis under H2O2 stimulation. These beneficial effects were GHRH receptor-dependent and were paralleled by increased phosphorylation of STAT3 and Akt. Transplantation of GHRH-preconditioned EPCs into HLI model mice enhanced blood flow recovery by increasing vascular formation density and enhanced tissue regeneration at the lesion site. CONCLUSION: Our studies demonstrate a novel role for GHRH in dramatically improving therapeutic angiogenesis in HLI by enhancing the biological functions of EPCs. These findings support additional studies to explore the full potential of GHRH in augmenting cell therapy for the management of ischemia.

The Growth Hormone Releasing Hormone Analogue, Tesamorelin, Decreases Muscle Fat and Increases Muscle Area in Adults with HIV.

BACKGROUND: Tesamorelin, a growth hormone-releasing hormone analogue, decreases visceral adipose tissue in people living with HIV, however, the effects on skeletal muscle fat and area are unknown. OBJECTIVES: The goals of this exploratory secondary analysis were to determine the effects of tesamorelin on muscle quality (density) and quantity (area). DESIGN: Secondary, exploratory analysis of two previously completed randomized (2:1), clinical trials. SETTING: U.S. and Canadian sites. PARTICIPANTS: People living with HIV and with abdominal obesity. Tesamorelin participants were restricted to responders (visceral adipose tissue decrease ≥8%). INTERVENTION: Tesamorelin or placebo. MEASUREMENTS: Computed tomography scans (at L4-L5) were used to quantify total and lean density (Hounsfield Units, HU) and area (centimeters2) of four trunk muscle groups using a semi-automatic segmentation image analysis program. Differences between muscle area and density before and after 26 weeks of tesamorelin or placebo treatment were compared and linear regression models were adjusted for baseline and treatment arm. RESULTS: Tesamorelin responders (n=193) and placebo (n=148) participants with available images were similar at baseline; most were Caucasian (83%) and male (87%). In models adjusted for baseline differences and treatment arm, tesamorelin was associated with significantly greater increases in density of four truncal muscle groups (coefficient 1.56-4.86 Hounsfield units; all p<0.005), and the lean anterolateral/abdominal and rectus muscles (1.39 and 1.78 Hounsfield units; both p<0.005) compared to placebo. Significant increases were also seen in total area of the rectus and psoas muscles (0.44 and 0.46 centimeters2; p<0.005), and in the lean muscle area of all four truncal muscle groups (0.64-1.08 centimeters2; p<0.005). CONCLUSIONS: Among those with clinically significant decrease in visceral adipose tissue on treatment, tesamorelin was effective in increasing skeletal muscle area and density. Long term effectiveness of tesamorelin among people with and without HIV, and the impact of these changes in daily life should be further studied.

GHRH-mediated GH release is associated with sympathoactivation and baroreflex resetting: a microneurographic study in healthy humans.

Previous research suggested substantial interactions of growth hormone (GH) and sympathetic nervous activity. This cross talk can be presumed both during physiological (e.g., slow-wave sleep) and pathological conditions of GH release. However, microneurographic studies of muscle sympathetic nerve activity (MSNA) and assessment of baroreflex function during acute GH-releasing hormone (GHRH)-mediated GH release were not conducted so far. In a balanced, double-blind crossover design, GHRH or placebo (normal saline) were intravenously administered to 11 healthy male volunteers. MSNA was assessed microneurographically and correlated with blood pressure (BP) and heart rate (HR) at rest before (pre-) and 30-45 (post-I) and 105-120 min (post-II) after respective injections. Additionally, baroreflex function was assessed via graded infusion of vasoactive drugs. GHRH increased GH serum levels as intended. Resting MSNA showed significant net increases of both burst rate and total activity from pre- to post-I and post-II following GHRH injections compared with placebo (ANOVA for treatment and time, burst rate: P = 0.028; total activity: P = 0.045), whereas BP and HR were not altered. ANCOVA revealed that the dependent variable MSNA was not affected by the independent variables mean arterial BP (MAP) or HR (MAP: P = 0.006; HR: P = 0.003). Baroreflex sensitivity at baroreflex challenge was not altered. GHRH-mediated GH release is associated with a significant sympathoactivation at central nervous sites superordinate to the simple baroreflex feedback loop because GH induced a baroreflex resetting without altering baroreflex sensitivity.

IGF-1 and somatocrinin trigger islet differentiation in human amniotic membrane derived mesenchymal stem cells.

AIM: To induce differentiation of human amniotic membrane derived mesenchymal stem cells (hAMMSCs) into insulin producing cells (IPCs) by treating with somatocrinin or growth hormone releasing hormone (GHRH) and Insulin-like growth factor-1 (IGF-1). MAIN METHOD: In this investigation, we cultivated and characterized hAMMSCs and then treated with IGF-1 and somatocrinin to find out whether this combination gives better yield of insulin producing cells. We showed that hAMMSCs can give rise to IPCs on exposure to serum-free defined media containing specific growth factors and differentiating agents in presence of IGF-1 and somatocrinin. KEY FINDING: A combination of IGF-1 and somatocrinin lead to differentiation of large number of IPCs from hAMMSCs. These IPCs were found to be positive for dithizone indicating their insulin secretory mechanism. Moreover these cells were also found to be positive for C-peptide. IPCs released insulin in response to glucose challenge. Gene expression analysis exhibited significant up-regulation of pancreatic transcription factor GLUT2 and Insulin. SIGNIFICANCE: Our data thus demonstrates for the first time that somatocrinin and IGF-1 synergistically enhance the differentiation of hAMMSCs into IPCs.

Effect of the Orally Active Growth Hormone Secretagogue MK-677 on Somatic Growth in Rats.

PURPOSE: Growth hormone secretagogues (GHSs) possess the ability to release growth hormone (GH) in the body. This study aimed to investigate the effects of MK-677, an orally active GHS, on somatic growth in rats. MATERIALS AND METHODS: The serum levels of GH were measured after oral administration of MK-677 to confirm GH stimulatory effects. Body weight, body length, tibia length, epiphyseal plate width, and serum levels of insulin-like growth factor (IGF)-I were measured after oral administration of 4 mg/kg of MK-677 for 6 weeks to investigate growth-promoting effects. RESULTS: Oral administration of MK-677 at 4 mg/kg increased peak GH concentrations by 1.8-fold, compared to baseline. However, oral administration of MK-677 for 6 weeks did not increase body growth or serum levels of IGF-I. At 6 weeks after treatment, the GH response to MK-677 was abolished. Pituitary GH mRNA and hypothalamic GH-releasing hormone mRNA, and GH secretagogue receptor (GHSR) mRNA expression in the pituitary and hypothalamus did not differ between the control and treatment group. Somatostatin (SST) mRNA expression in the hypothalamus was markedly increased in the treatment group, whereas SST receptor (SSTR)-2 mRNA expression in the pituitary gland was decreased. Protein expression of hypothalamic GHSR, SST, and pituitary SSTR-2 showed patterns similar to those for mRNA expression. CONCLUSION: Our results suggest that prolonged administration of MK-677 in rats does not promote growth despite the GH stimulatory effect of MK-677, which may be related to increased expression of SST in the hypothalamus. Further studies are needed to overcome the observed desensitization to GHS.