GHRP-6

Growth Hormone-Releasing Peptide-6 (GHRP-6) Ameliorates Post-Infarct Ventricular Remodeling and Systolic Dysfunction in a Model of Permanent Coronary Ligation.

Linlin Wang, Arielis Rodriguez-Ulloa, Jorge Berlanga-Acosta +7 more

Background/Objective: GHRP-6 is a GH secretagogue hexapeptide with expanding and promising cardioprotective effects. Having determined 0.4 mg/kg as the minimum effective dose for enhancing inotropy based on echocardiographic parameters in healthy rats, we implemented a non-reperfusion myocardial infarct model, with its consequent left ventricle wall thinning and ballooning, via permanent left descending coronary artery ligation. Methods: Rats were assigned to three groups: sham-operated/normal rats, infarcted + saline-treated control rats, and infarcted + GHRP-6-administration rats. Treatments were initiated post-surgery and continued for 7 days. On day 7, the animals were echocardiographically and histologically evaluated. For mitochondrial proteomic analysis, an additional 12 healthy rats were used. Six animals received GHRP-6 or normal saline and were observed for 6 h after the inoculation. Results: Here, we show that GHRP-6 attenuated myocardial tissue demise, reduced myocardial interstitial fibrosis/scarring, and integrally improved left ventricle physiology. The proteomic analysis indicated that the GHRP-6 cardioprotective effects may be theoretically mediated by the concerted upregulation of proteins/pathways involved in fatty acid beta-oxidation, apoptosis prevention pathways, antioxidant defenses, and mitochondrial metabolic reprogramming. Conclusions: GHRP-6 is a potent cardioprotective candidate attenuating morphological and functional outcomes caused by late ischemia.

Effect of intracerebroventricular (ICV) injection of antimicrobial peptide expressed in the body-2 (LEAP-2) and its interaction with cannabinoid and ghrelin systems on food intake in broiler chickens.

Ariana Rahmania, Morteza Zendehdel, Shahin Hassanpour

Liver-expressed antimicrobial peptide 2 (LEAP-2), initially identified as an antimicrobial peptide which endocannabinoid and ghrelin action may occur via changes in Leap2 expression. This study aimed to determine effect of ICV injection of LEAP2and its interaction with cannabinoid and ghrelin systems on food intake in broiler chickens. In the present study 4 experiments were conducted, each containing 4 experimental groups. In experiment 1, chicken injected with group 1 ICV injection of saline, group 2 with LEAP2 (0.75 nmol), group 3 with LEAP2 (1.5 nmol) and group 4 with LEAP2 (3 nmol). In experiment 2, chicken received ICV injections as group 1: saline, group 2: (D-Lys-3)-GHRP-6 (0.5 nmol), group 3: LEAP2 (3 nmol) and group 4 with co injection of the (D-Lys-3)-GHRP-6 + LEAP2. In experiment 3 chiken received ICV inejctions as: group 1: saline, group 2: SR141716A (6.25 µg), group 3: LEAP2 (3 nmol) and group 4 with co injection of the SR141716A + LEAP2. In experiment 4 chiken received ICV inejctions as: group 1: saline, group 2: AM630 (1.25 µg), group 3: LEAP2 (3 nmol) and group 4 with co injection of the AM630 + LEAP2. Immediately following the infusions, the broilers were returned to their respective boxes, where they were provided with pre-weighed meal and fresh water ad libitum. The cumulative meal consumption was subsequently measured at intervals of 30, 60, and 120 min post-administration. According to the results, ICV injection of the LEAP2 (1.5 and 3 nmol) significantly decreased food intake (P<0.05). Co-injection of the (D-Lys-3)-GHRP-6 + LEAP2 significantly decreased LEAP2-induced hypophagia (P<0.05). Co-injection of the (D-Lys-3)-GHRP-6 + LEAP2 significantly increased hypophagic effect of the LEAP2 (P<0.05). Co-injection of the SR141716A + LEAP2 significantly amplified LEAP2-induced hypophagia compared to control group (P<0.05). Co-injection of the AM630 + LEAP2 significantly amplified LEAP2-induced hypophagia compared to control group (P<0.05). These results suggested that LEAP2-induced hypophagia mediates via ghrelin and CB1 and CB2 receptors in neonatal chicken.

Oral salmon acylated ghrelin increases food intake in common carp (Cyprinus carpio) via ghrelin receptors, likely through sensory nerves rather than systemic absorption.

Minoru Kihara, Teppei Yamagiwa, Hidekazu Katayama +1 more

This study clarified the local mechanism of action and assessed the aquaculture potential of orally administered salmon acylated ghrelin (sAG) on feed intake in common carp (Cyprinus carpio). Experimental diets containing sAG (ranging from 0.001 to 13.04 µg/g) were prepared and fed to carp at 2.0 % of body weight (BW) in single-shot trials. Fish receiving diets of 0.64 µg/g (1.3 µg/100 g BW) or higher exhibited a significant, dose-dependent increase in additional feed intake, plateauing at 1.20 µg/g (2.4 µg/100 g BW). Despite this behavioral effect, plasma ghrelin levels remained unchanged, as measured by both N-terminal and salmon-specific C-terminal radioimmunoassays, confirming that sAG was not systemically absorbed. The orexigenic effect was abolished by pretreatment with the ghrelin receptor antagonist [D-Lys3]-GHRP-6 or with capsaicin, demonstrating local sAG action via growth hormone secretagogue receptor signaling and peripheral sensory neurons (likely vagal afferents). These findings provide the first evidence that fish ghrelin exerts biological activity via a non-circulatory neuroendocrine pathway. This advances our understanding of the vertebrate gut-brain axis and highlights the potential of harnessing locally acting peptides for physiological modulation in aquatic species.

Growth hormone releasing peptide-6 (GHRP-6) ameliorates acute lung injury and its subsequent evolvement to interstitial fibrosis.

Linlin Wang, Jorge Berlanga-Acosta, Haoying Yu +6 more

Acute lung injury/acute respiratory distress syndrome is a complex, characterized by acute onset, alveolar damage, and progressive hypoxemia. The subsequent proliferative phase drives to pulmonary fibrosis. Lipopolysaccharide (LPS) and zymosan (ZYM) induced lung injury are commonly used biomodels that recapitulate multiple pathogenic hallmarks. We examined the ability of growth hormone releasing peptide 6 (GHRP-6) to attenuate the pulmonary damages associated with intratracheal instillation of LPS or ZYM combined injection with platelet activating factor (PAF) in mice. For the acute scenario, mice received LPS challenge and 6 h later, assigned to normal saline (Control) or to a single administration of each GHRP-6 dose and evolved for 24 h; or mice received four ZYM tracheal instillations and 6 h after, one PAF injection assigned to normal saline (Control) or to five administrations of each GHRP-6 dose and evolved for 15 days. For the chronic scenario, mice were terminated 28 days after receiving a single LPS instillation and seven subsequent daily administrations of GHRP-6; or mice were terminated 28 days after receiving five GHRP-6 therapeutic interventions after four ZYM tracheal instillations and one PAF injection. The acute scenario, GHRP-6 reduced neutrophilic alveolitis, attenuated lung compliance failure, contributed to improve alveolar-capillary permeability, and reduced interleukin-1 beta serum levels. The chronic scenario, GHRP-6 preserved lung parenchymal integrity accounted for meager collagen accumulation. This is the first assessment on the potential protective of GHRP-6 in model of lung damages. This study therefore paves the way for future research on the potential pneumoprotective effects of GHRP-6.

Growth hormone-releasing peptide 6 (GHRP-6) hydrogel for acute kidney injury therapy via metabolic regulation.

Xiaotong Zhao, Kai Pan, Rui Li +8 more

Renal tubular epithelial cells (TECs), which are highly susceptible to injury during acute kidney injury (AKI), have notable regenerative effects on renal recovery after AKI. AKI-driven metabolic reprogramming of TECs plays a critical role in determining whether kidneys recover functionally or develop fibrosis. Targeting the metabolism of TECs offers valuable insights into AKI treatment. Growth hormone-releasing hormone (GHRH) and its analog GHRH peptide (GHRP) play beneficial roles in the field of regenerative medicine. Here, we designed a self-assembling GHRP-6 peptide hydrogel, and we hypothesized that this hydrogel could reprogram the metabolism of TECs, further enhancing recovery from AKI. Metabolomic sequencing analysis revealed that spermidine, L-glutamine, and acetyl-CoA, which are involved in amino acid and fatty acid metabolism, were highly enriched in a mouse model of AKI treated with the GHRP-6 hydrogel. Further study revealed that GHRP-6 hydrogel treatment enhanced the survival of TECs in the ischemic microenvironment by activating the mTOR-P70 pathway. In conclusion, GHRP-6 hydrogel treatment has beneficial therapeutic effects on AKI through the targeting of metabolic reprogramming, which offers a novel therapeutic strategy to protect TECs in AKI treatment.

Impact of GHRL (RS696217) and LEPR (RS1137101) gene polymorphisms on hormonal and anthropometric outcomes after bariatric surgery.

Andrii Prodan

Objective. The aim of the study was to evaluate the influence of GHRL (rs696217) and LEPR (rs1137101) gene polymorphisms on weight loss dynamics and endocrine marker changes following various bariatric procedures. Patients and Methods. A total of 76 patients undergoing laparoscopic sleeve gastrectomy (LSG), gastric plication (LGCP), and gastric artery embolization (GAE) were genotyped for GHRL (rs696217) and LEPR (rs1137101). Body mass index (BMI), total weight loss (TWL), excess weight loss (EWL), and hormonal markers (ghrelin, leptin, adiponectin, resistin, HbA1c) were assessed preoperatively and at 3, 6, and 12 months postoperatively. Results. Carriers of the T allele of GHRL (rs696217) experienced significantly greater reductions in BMI, TWL, and EWL, particularly following LSG and GAE (p<0.05). A notable reduction in total ghrelin levels was observed in T allele carriers (up to -46.75%, p<0.001) 6 months after surgery. Improvements in resistin (p=0.0002) and HbA1c (p=0.014) levels were also more pronounced in this group. LEPR (rs1137101) polymorphism showed limited impact on outcomes after LGCP, but it was associated with improved TWL and EWL in A allele carriers after LSG (p=0.006 and p=0.016, respectively). Conclusion. The T allele of GHRL (rs696217) appears to be a promising predictive marker for greater metabolic and hormonal improvement following bariatric procedures targeting the ghrelin-producing stomach zones. LEPR (rs1137101) may also influence postoperative outcomes in a procedure-specific manner. These findings support the potential role of genetic screening in optimizing patient selection and predicting surgical success.

Aza-Isotryptophan: Synthesis, Pictet-Spengler Chemistry, Incorporation and Conformational Analysis in Peptides, and Activity in Modulators of the Cluster of Differentiation-36 Receptor.

Xiaozheng Wei, Mukandila Mulumba, Sylvain Chemtob +2 more

Isotryptophan (Itr) is the rare 2-indoyl counterpart of the essential amino acid tryptophan. Considering the potential to explore novel side chain χ-space in a residue prone to adopt backbone turn conformers, azaItr has been effectively synthesized and employed in Pictet-Spengler and peptide chemistry. β-Turn geometry was characterized in model peptides of the Ala-azaItr-d-Phe triad by X-ray and NMR analyses. Moreover, azaItr analogs of growth hormone-releasing peptide 6 (GHRP-6) demonstrated a promising cluster of differentiation-36 receptor (CD36) binding affinity and modulatory effect on the inflammatory response induced by the activated complex composed of the latter coreceptor in the Toll-like receptor-2/6 heterodimer.

A novel butyrylcholinesterase inhibitor induces antidepressant, pro-cognitive, and anti-anhedonic effects in Flinders Sensitive Line rats: The role of the ghrelin-dopamine cascade.

Nadia Olivier, Brian H Harvey, Stanislav Gobec +4 more

Major depressive disorder (MDD) is often treatment resistant, particularly in addressing anhedonia and cognitive deficits. Novel pharmacological strategies are needed. While butyrylcholinesterase, ghrelin, and dopamine (DA) have been well studied in the context of stress and MDD, their interaction remains unclear.

Danshen-Chuanxiong-Honghua ameliorates neurological function and inflammation in traumatic brain injury in rats via modulating Ghrelin/GHSR.

Xiaohang Zhang, Yawen Cai, Meng Chen +7 more

Guanxin II, proposed by Chen Keji (National master of traditional Chinese medicine), possesses neuroprotective effect. Interestingly, its simplified prescription Danshen-Chuanxiong-Honghua (DCH) can also clinically ameliorate cerebral impairment and improve spatial cognitive deficits, similar to the function of original formula.

GHSR gene knockout alleviates the liver pathological response in Echinococcus granulosus infection by reducing parasite survival.

Jiang Zhu, Tanfang Zhou, Guangfeng Chen +6 more

Cystic echinococcosis (CE) is a parasitic disease caused by the larval stage of Echinococcus granulosus, and the immunosuppressive microenvironment exacerbates disease progression. Ghrelin, a peptide hormone, plays a role in modulating immune inflammation and may influence the progression of E. granulosus infection through its receptor, GHSR (growth hormone secretagogue receptor). However, whether GHSR downregulation can inhibit E. granulosus infection remains unclear. In this study, we extracted liver tissues from E. granulosus-infected mice and those treated with the GHSR antagonist [D-Lys3]-GHRP-6. Proteomic analysis revealed 341 differentially expressed proteins, of which 185 were upregulated and 156 were downregulated. Metabolomic sequencing revealed 101 differentially expressed metabolites, including 62 upregulated and 39 downregulated metabolites. KEGG pathway enrichment analysis of both proteomic and metabolomic data revealed seven key signalling pathways, 11 key proteins, and 26 key metabolites that interact through metabolic and organic system networks. Next, we examined the disease progression of E. granulosus infection in GHSR-knockout mice. Compared with the E. granulosus (Eg) group, the GHSR-KO group presented a significant reduction in the number of liver infection foci. The serum and liver ghrelin levels were significantly greater in the E. granulosus group than in the control group, along with increased secretion of proinflammatory cytokines (IL-2 and IFN-γ) and decreased secretion of anti-inflammatory cytokines (IL-4 and IL-10). In contrast, the GHSR-KO group presented significantly lower ghrelin levels in both the serum and liver, with reduced proinflammatory cytokine secretion and increased anti-inflammatory cytokine secretion, similar to those of the control group. Furthermore, ghrelin and inflammation-related factors, including MyD88, NF-κB p65, iNOS, and Arg-1, exhibited coordinated expression changes in liver lesions and surrounding areas. These findings suggest that GHSR gene knockout can ameliorate the progression of liver E. granulosus infection and associated liver inflammation.

Subchronic safety assessment of CIGB-500 in beagle dog after repeated daily dose administration over 28 days.

Jorge Castro, Imran Shaikh, Sherwin Silo +9 more

CIGB-500 is a product whose active pharmaceutical ingredient is GHRP-6, (Growth Hormone Releasing Peptide-6), a synthetic peptide that allows the rescue of cardiac mass affected during Acute Myocardial Infarction. The objective of the study was to determine the toxicity profile of CIGB-500 in dogs. As general methodology, CIGB-500 was administered daily to dogs by intravenous route for 28 consecutive days. All animals were allocated to four groups: Control, Low-Dose (300 μg/kg/day), Mid dose (1000 μg/kg/day) and High-Dose (2000 μg/μg/day). Hypersalivation, hypoactivity, reduced heart rate, changes in respiration, pale gums and erythema of the head region were observed in some animals administered at 1000 and 2000 μg/kg/day. These clinical signs were transient, and were therefore considered non-adverse. Treatment with CIGB-500 did not result in any adverse macroscopic or microscopic changes. A decrease in heart rate value was noted following CIGB-500 treatment at all dose levels an at the end of recovery period, the heart rate effects at 2000 μg/kg/day were comparable to controls. In conclusion, the daily administration of CIGB-500 at doses up to 2000 μg/kg/day was well-tolerated, findings noted were transient, minor, non-adverse and reversible, and the no observable adverse effect level (NOAEL) was considered to be 2000 μg/kg/day.

Ghrelin suppresses water intake with a different physiological significance from atrial natriuretic peptide in conscious seawater-acclimated eels.

Hiroyuki Kaiya, Shigenori Nobata, Yoshio Takei

In general, ghrelin is known as one of the orexigenic (increasing appetite or food intake) hormones in mammals. However, it has also been shown that ghrelin inhibits water intake, which appears to be inconsistent with its role in the feeding response. In this study, the effect of ghrelin on water intake was comprehensively addressed using conscious seawater-acclimated eels as an experimental model for water drinking behaviour. When injected intra-arterially, ghrelin inhibited copious drinking in a dose-dependent manner without affecting arterial pressure. This effect contrasted with the inhibitory effect of atrial natriuretic peptide (ANP) on drinking, which is synchronized with a vasodepressor effect. Similarly, intra-cerebroventricular injection of ghrelin also decreased the drinking rate without affecting arterial pressure. Continuous infusion of ghrelin from the ventral aorta also decreased the drinking rate, concomitant with an increase in plasma ghrelin concentration. The inhibitory effects of ghrelin on drinking were as potent and efficacious as those of ANP. The inhibitory action was not blocked by pre-treatment with a ghrelin receptor antagonist ([D-Lys3] GHRP-6); consistently, the agonist form (GHRP-6) injected intra-arterially did not show any inhibitory effect of ghrelin when injected peripherally. These results demonstrate that ghrelin is a potent anti-dipsogen in eels without baroreflex and ANP secretion, and it is possible that ghrelin's effect might be mediated through another type of ghrelin receptor that [D-Lys3] GHRP-6 or GHRP-6 do not bind.

Intranasal Delivery of a Ghrelin Mimetic Engages the Brain Ghrelin Signaling System in Mice.

Renée Poelman, Marie V Le May, Erik Schéle +2 more

Ghrelin, the endogenous ligand of the growth hormone secretagogue receptor (GHSR), promotes food intake and other feeding behaviors, and stimulates growth hormone (GH) release from the pituitary. Growth hormone secretagogues (GHS), such as GHRP-6 and MK-0677, are synthetic GHSR ligands that activate orexigenic neuropeptide Y neurons that coexpress agouti-related peptide (AgRP) in the arcuate nucleus of the hypothalamus when administered systemically. Systemic GHRP-6 also stimulates GH release in humans and rats. Thus, GHS and ghrelin have therapeutic relevance in patients who could benefit from its orexigenic and/or GH-releasing effects. This study examined whether intranasal delivery of ghrelin, GHRP-6, or MK-0677 engages the brain ghrelin signaling system. Effective compounds and doses were selected based on increased food intake after intranasal application in mice. Only GHRP-6 (5 mg/kg) increased food intake without adverse effects, prompting detailed analysis of meal patterns, neuronal activation in the arcuate nucleus (via Fos mapping) and neurochemical identification of c-fos messenger RNA (mRNA)-expressing neurons using RNAscope. We also assessed the effect of intranasal GHRP-6 on serum GH levels. Intranasal GHRP-6 increased food intake by increasing meal frequency and size. Fos expression in the arcuate nucleus was higher in GHRP-6-treated mice than in saline controls. When examining the neurochemical identity of c-fos-mRNA-expressing neurons, we found coexpression with 63.5 ± 1.9% Ghsr mRNA, 79 ± 6.8% Agrp mRNA, and 11.4 ± 2.5% Ghrh mRNA, demonstrating GHRP-6's ability to engage arcuate nucleus neurons involved in food intake and GH release. Additionally, intranasal GHRP-6 elevated GH serum levels. These findings suggest that intranasal GHRP-6, but not ghrelin or MK-0677, can engage the brain ghrelin signaling system.

Ghrelin promotes neurologic recovery and neurogenesis in the chronic phase after experimental stroke.

Carolin Beuker, Ulrike Schreiner, Jan-Kolja Strecker +6 more

The neuroprotective and proangiogenic potential of ghrelin in acute ischemic stroke has been demonstrated in experimental studies. However, the transferability of these results is limited as ghrelin was administered either before or very early after stroke onset and follow-up was limited to the first days after stroke. The aim of this study was therefore to close and extend this knowledge gap. To this end, we investigated the effect of ghrelin in two different translational animal models, one investigating acute and one investigating long-term structural and functional recovery after experimental stroke.

Changes in Locomotor Activity Observed During Acute Nicotine Withdrawal Can Be Attenuated by Ghrelin and GHRP-6 in Rats.

Jázmin Ayman, András Buzás, Roberta Dochnal +3 more

Background/Objectives: Ghrelin and growth hormone-releasing peptide 6 (GHRP-6) are peptides which can stimulate GH release, acting through the same receptor. Ghrelin and its receptor have been involved in reward sensation and addiction induced by natural and artificial drugs, including nicotine. The present study aimed to investigate the impacts of ghrelin and GHRP-6 on the horizontal and vertical activity in rats exposed to chronic nicotine treatment followed by acute nicotine withdrawal. Methods: Male and female Wistar rats were exposed daily to intraperitoneal (ip) injection with 2 mg/kg nicotine or saline solution for 7 days, twice a day (at 8:00 and at 20:00). In parallel, the rats were exposed daily to an intracerebroventricular (icv) injection with 1 μg/2 μL ghrelin or 1 μg/2 μL GHRP-6 or saline solution for 7 days, once a day (at 8:00). On the morning of the eighth day (12 h after the last ip administration) and the ninth day (24 h after the last ip administration), the horizontal and vertical activity were monitored in a conducta system. Results: On the eighth day, in nicotine-treated rats a significant hyperactivity was observed, that was reduced significantly by ghrelin and GHRP-6. On the ninth day, in nicotine-treated rats a significant hypoactivity was assessed that was reversed significantly by ghrelin and GHRP-6. Conclusions: Based on the present results, the changes in horizontal and vertical activity observed after 12 and 24 h of nicotine withdrawal can be attenuated by ghrelin and GHRP-6.

Novel chimeric peptides based on endomorphins and ghrelin receptor antagonist produced supraspinal antinociceptive effects with reduced acute tolerance in mice.

Bing Wu, Songxia Cheng, Fuyan Liu +6 more

It is widely recognized that developing bi- or multifunctional opioid compounds could offer a valuable approach to pain management with fewer side effects compared to single-target compounds. In this study, we designed and characterized two novel chimeric peptides, EM-1-DLS and EM-2-DLS, incorporating endomorphins (EMs) and the ghrelin receptor antagonist [D-Lys3]-GHRP-6 (DLS). Functional assays demonstrated that EM-1-DLS and EM-2-DLS acted as κ-opioid receptor (κ-OR)-preferring agonists, weak μ-opioid receptors (μ-OR) and ghrelin receptor (GHSR) agonists. Upon intracerebroventricular (i.c.v.) administration in mice, both EM-1-DLS and EM-2-DLS exhibited dose- and time-dependent antinociceptive effects in the tail withdrawal test. EM-1-DLS demonstrated the highest antinociceptive potency among the peptides, with an ED50 approximately 8-fold greater than EM-1, while EM-2-DLS showed comparable effects to EM-2. The antinociceptive actions of EM-1-DLS involved activation of GHS-R1α, μ-OR, and κ-OR, whereas EM-2-DLS acted via GHS-R1α, δ-OR, and κ-OR pathways. Additionally, acute antinociceptive tolerance was investigated, revealing that EM-1-DLS induced a tolerance ratio of 2.33-fold, significantly lower than the 5.19-fold ratio induced by EM-1. Cross-tolerance ratios between the chimeric peptides and EMs ranged from 0.92 to 1.76, indicating reduced tolerance compared to EMs alone. These findings highlight the potential of these chimeric peptides to mitigate pain with diminished tolerance development, suggesting a promising strategy for the development of new analgesic therapies with improved safety profiles.

Targeting CD36 With EP 80317 Reduces Remote Inflammatory Response to Hind Limb Ischemia-Reperfusion in Mice.

Hanan Elimam, Jade Gauvin, David N Huynh +7 more

Reperfusion of ischemic skeletal muscle triggers oxidative stress and an immediate inflammatory reaction, leading to damage of distant organs such as the lungs. The inflammatory process implicates numerous mediators, including cytokines, chemokines, and arachidonic acid metabolites. In the orchestration of the inflammatory cascade, a critical role is played by the cluster of differentiation-36 receptor (CD36), a scavenger receptor class B protein (SR-B2) which is expressed on macrophages and functions as a Toll-like receptor coreceptor. A mouse model of hind limb ischemia-reperfusion has been used to investigate the interplay between CD36 signaling and remote inflammation: leukocyte recruitment, regulation of the nucleotide-binding domain leucin-rich repeat and pyrin-containing receptor 3 (NLRP3) inflammasome, and release of nuclear factor-kappa B (NF-ĸB) and arachidonic acid metabolites. Levels of reactive oxygen species, inflammatory mediators, and gene expression were measured in blood and lung tissue samples collected from anesthetized mice on which unilateral hind limb ischemia was induced by rubber band constriction for 30 min followed by reperfusion for 3 h. The CD36 modulator EP 80317, a member of the growth hormone releasing peptide 6 family, was employed as a pharmacological agent to mitigate distant lung injury following skeletal limb ischemia-reperfusion. Targeting CD36 on monocytes/macrophages, EP 80317 abated pro-inflammatory signaling and transcriptional activity encompassing lipid and cytokine mediators. Targeting CD36 was shown to offer promise for curtailing tissue injury following hind limb ischemia-reperfusion.

Ghrelin is essential for lowering blood pressure during torpor.

Kazuma Matsui, Takanori Ida, Kanae Oishi +2 more

Daily torpor is an active hypothermic phenomenon that is observed in some mammals and birds during fasting. A decrease in blood pressure has also been observed in torpor; however, there remains a lack of knowledge of the underlying mechanism. We have previously reported that ghrelin, an orexigenic hormone, has a hypothermic effect and is essential for the induction and maintenance of torpor. It is also known that the ghrelin secretion is enhanced during fasting and that ghrelin receptors are distributed in the cardiovascular system. Therefore, this study was conducted to test the hypothesis that ghrelin is actively involved in the regulation of blood pressure during torpor induction.

Ghrelin is involved in regulating the progression of Echinococcus Granulosus-infected liver lesions through suppression of immunoinflammation and fibrosis.

Jiang Zhu, Hongqiong Zhao, Aili Aierken +6 more

Cystic Echinococcosis (CE) is a zoonotic disease causing fibrosis and necrosis of diseased livers caused by infection with Echinococcus granulosus (E.g). There is evidence that E.g is susceptible to immune escape and tolerance when host expression of immunoinflammation and fibrosis is suppressed, accelerating the progression of CE. Ghrelin has the effect of suppressing immunoinflammation and fibrosis, and whether it is involved in regulating the progression of E.g-infected liver lesions is not clear.

Ghrelin Modulates Voltage-Gated Ca2+ Channels through Voltage-Dependent and Voltage-Independent Pathways in Rat Gastric Vagal Afferent Neurons.

Hannah J Goudsward, Victor Ruiz-Velasco, Salvatore L Stella +2 more

The orexigenic gut peptide ghrelin is an endogenous ligand for the growth hormone secretagogue receptor type 1a (GHSR1a). Systemic ghrelin administration has previously been shown to increase gastric motility and emptying. While these effects are known to be mediated by the vagus nerve, the cellular mechanism underlying these effects remains unclear. Therefore, the purpose of the present study was to investigate the signaling mechanism by which GHSR1a inhibits voltage-gated Ca2+ channels in isolated rat gastric vagal afferent neurons using whole-cell patch-clamp electrophysiology. The ghrelin pharmacological profile indicated that Ca2+ currents were inhibited with a log (Ic50) = -2.10 ± 0.44 and a maximal inhibition of 42.8 ± 5.0%. Exposure to the GHSR1a receptor antagonist (D-Lys3)-GHRP-6 reduced ghrelin-mediated Ca2+ channel inhibition (29.4 ± 16.7% vs. 1.9 ± 2.5%, n = 6, P = 0.0064). Interestingly, we observed that activation of GHSR1a inhibited Ca2+ currents through both voltage-dependent and voltage-independent pathways. We also treated the gastric neurons with either pertussis toxin (PTX) or YM-254890 to examine whether the Ca2+ current inhibition was mediated by the Gα i/o or Gα q/11 family of subunits. Treatment with both PTX (Ca2+ current inhibition = 15.7 ± 10.6%, n = 8, P = 0.0327) and YM-254890 (15.2 ± 11.9%, n = 8, P = 0.0269) blocked ghrelin's effects on Ca2+ currents, as compared with control neurons (34.3 ± 18.9%, n = 8). These results indicate GHSR1a can couple to both Gα i/o and Gα q/11 in gastric vagal afferent neurons. Overall, our findings suggest GHSR1a-mediated inhibition of Ca2+ currents occurs through two distinct pathways, offering necessary insights into the cellular mechanisms underlying ghrelin's regulation of gastric vagal afferents. SIGNIFICANCE STATEMENT: This study demonstrated that in gastric vagal afferent neurons, activation of GHSR1a by ghrelin inhibits voltage-gated Ca2+ channels through both voltage-dependent and voltage-independent signaling pathways. These results provide necessary insights into the cellular mechanism underlying ghrelin regulation of gastric vagal afferent activity, which may benefit future studies investigating ghrelin mimetics to treat gastric motility disorders.

Rikkunshito improves anorexia through ghrelin- and orexin-dependent activation of the brain hypothalamus and mesolimbic dopaminergic pathway in rats.

Koji Yakabi, Naomi Yamaguchi, Kiyoshige Takayama +9 more

Rikkunshito (RKT), a traditional Japanese medicine, can relieve epigastric discomfort and anorexia in patients with functional dyspepsia. RKT enhances the orexigenic hormone, ghrelin. Ghrelin regulates food motivation by stimulating the appetite control center in the hypothalamus and the brain mesolimbic dopaminergic pathway (MDPW). However, the effect of RKT on MDPW remains unclear. Here, we aimed to investigate the central neural mechanisms underlying the orexigenic effects of RKT, focusing on the MDPW.

Transcription repression of estrogen receptor alpha by ghrelin/Gq/11/YAP signaling in granulosa cells promotes polycystic ovary syndrome.

Pengfei Zhu, Xingyu Bi, Dan Su +7 more

Polycystic ovarian syndrome (PCOS) is a prevalent endocrinological disorder affected by ghrelin. This study aimed to investigate the molecular mechanisms underlying the effects of ghrelin on PCOS manifestations in mice and to assess the therapeutic potential of ghrelin. Female C57BL/6 mice were subcutaneously injected with 6 mg/100 g dehydroepiandrosterone (DHEA) for 20 days to induce PCOS. Alterations in reproductive cycles, ovarian morphology, serum sex hormone levels, and related signaling markers were examined. Furthermore, ghrelin-induced effects on granulosa cells and the role of ghrelin/Gq/11/ Yes-associated protein (YAP) signaling were studied by silencing Gαq/11 or YAP using si-RNAs. Finally, we evaluated the therapeutic potential of anti-ghrelin antibodies in DHEA-induced PCOS mice. DHEA administration led to significant PCOS-associated changes including weight gain, disrupted estrous cycles, ovarian morphological alterations, and hormonal imbalances in mice, with elevated Gαq/11 and acylated ghrelin expression, which was also noted in PCOS patients. However, treatment with anti-ghrelin antibodies effectively managed DHEA-induced damage in PCOS mice. In vitro, ghrelin exposure resulted in granulosa cell injury and modulated estrogen receptors alpha (ERα) and YAP protein levels, whereas silencing YAP and Gαq/11 reversed ghrelin-induced detrimental effects and up-regulated ERα expression. This study revealed that DHEA-induced PCOS traits in mice could be improved by anti-ghrelin antibodies, with the ghrelin/Gq/11/YAP signaling pathway identified as a crucial mediator in granulosa cells, affecting ERα transcription to regulate PCOS. These findings suggest a potential therapeutic strategy for the treatment of PCOS.

Ghrelin induced by ultraviolet B exposure promotes the restoration of diabetic cutaneous wound healing.

Qi-Rui Fu, Sha Peng, Chang-Qing Zhu +3 more

Diabetes mellitus (DM) presents impediment to wound healing. While ultraviolet B (UVB) exposure showed therapeutic potential in various skin conditions, its capacity to mediate diabetic wound healing remains unclear. To investigate the efficacy of UVB on wound healing and its underlying basis.

Ghrelin Improves Glucolipotoxicity-Induced Pancreatic β-Cellular Dysfunction and Apoptosis by Inhibiting Endoplasmic Reticulum Stress-Induced IRE1/JNK Pathway.

Xin-Ying Li, Chun-Rong Zhong, Jin-Chan Wu +2 more

Glucose and fatty acid overload-induced glucolipid toxicity of pancreatic β-cells is associated with the development of diabetes. Endoplasmic reticulum stress (ERS) plays an essential role in this process. Ghrelin, a peptide secreted by the pancreas, negatively correlates with oxidative stress. The study aimed to investigate ghrelin's role in glycolipid-induced β-cell dysfunction and its possible mechanism.

Calorie restriction activates a gastric Notch-FOXO1 pathway to expand ghrelin cells.

Wendy M McKimpson, Sophia Spiegel, Maria Mukhanova +7 more

Calorie restriction increases lifespan. Among the tissue-specific protective effects of calorie restriction, the impact on the gastrointestinal tract remains unclear. We report increased numbers of chromogranin A-positive (+), including orexigenic ghrelin+ cells, in the stomach of calorie-restricted mice. This effect was accompanied by increased Notch target Hes1 and Notch ligand Jag1 and was reversed by blocking Notch with DAPT, a gamma-secretase inhibitor. Primary cultures and genetically modified reporter mice show that increased endocrine cell abundance is due to altered Lgr5+ stem and Neurog3+ endocrine progenitor cell proliferation. Different from the intestine, calorie restriction decreased gastric Lgr5+ stem cells, while increasing a FOXO1/Neurog3+ subpopulation of endocrine progenitors in a Notch-dependent manner. Further, activation of FOXO1 was sufficient to promote endocrine cell differentiation independent of Notch. The Notch inhibitor PF-03084014 or ghrelin receptor antagonist GHRP-6 reversed the phenotypic effects of calorie restriction in mice. Tirzepatide additionally expanded ghrelin+ cells in mice. In summary, calorie restriction promotes Notch-dependent, FOXO1-regulated gastric endocrine cell differentiation.

Growth hormone releasing peptide-6 (GHRP-6) prevents doxorubicin-induced myocardial and extra-myocardial damages by activating prosurvival mechanisms.

Jorge Berlanga-Acosta, Danay Cibrian, Juan Valiente-Mustelier +6 more

Introduction: Dilated cardiomyopathy (DCM) is a fatal myocardial condition with ventricular structural changes and functional deficits, leading to systolic dysfunction and heart failure (HF). DCM is a frequent complication in oncologic patients receiving Doxorubicin (Dox). Dox is a highly cardiotoxic drug, whereas its damaging spectrum affects most of the organs by multiple pathogenic cascades. Experimentally reproduced DCM/HF through Dox administrations has shed light on the pathogenic drivers of cardiotoxicity. Growth hormone (GH) releasing peptide 6 (GHRP-6) is a GH secretagogue with expanding and promising cardioprotective pharmacological properties. Here we examined whether GHRP-6 administration concomitant to Dox prevented the onset of DCM/HF and multiple organs damages in otherwise healthy rats. Methods: Myocardial changes were sequentially evaluated by transthoracic echocardiography. Autopsy was conducted at the end of the administration period when ventricular dilation was established. Semiquantitative histopathologic study included heart and other internal organs samples. Myocardial tissue fragments were also addressed for electron microscopy study, and characterization of the transcriptional expression ratio between Bcl-2 and Bax. Serum samples were destined for REDOX system balance assessment. Results and discussion: GHRP-6 administration in parallel to Dox prevented myocardial fibers consumption and ventricular dilation, accounting for an effective preservation of the LV systolic function. GHRP-6 also attenuated extracardiac toxicity preserving epithelial organs integrity, inhibiting interstitial fibrosis, and ultimately reducing morbidity and mortality. Mechanistically, GHRP-6 proved to sustain cellular antioxidant defense, upregulate prosurvival gene Bcl-2, and preserve cardiomyocyte mitochondrial integrity. These evidences contribute to pave potential avenues for the clinical use of GHRP-6 in Dox-treated subjects.

Ghrelin alleviates intestinal ischemia-reperfusion injury by activating the GHSR-1α/Sirt1/FOXO1 pathway.

Shi-Shi Liao, Le-le Zhang, Yi-Guo Zhang +5 more

Ischemia-reperfusion (IR) injury is primarily characterized by the restoration of blood flow perfusion and oxygen supply to ischemic tissue and organs, but it paradoxically leads to tissue injury aggravation. IR injury is a challenging pathophysiological process that is difficult to avoid clinically and frequently occurs during organ transplantation, surgery, shock resuscitation, and other processes. The major causes of IR injury include increased levels of free radicals, calcium overload, oxidative stress, and excessive inflammatory response. Ghrelin is a newly discovered brain-intestinal peptide with anti-inflammatory and antiapoptotic effects that improve blood supply. The role and mechanism of ghrelin in intestinal ischemia-reperfusion (IIR) injury remain unclear. We hypothesized that ghrelin could attenuate IIR-induced oxidative stress and apoptosis. To investigate this, we established IIR by using a non-invasive arterial clip to clamp the root of the superior mesenteric artery (SMA) in mice. Ghrelin was injected intraperitoneally at a dose of 50 μg/kg 20 min before IIR surgery, and [D-Lys3]-GHRP-6 was injected intraperitoneally at a dose of 12 nmol/kg 20 min before ghrelin injection. We mimicked the IIR process with hypoxia-reoxygenation (HR) in Caco-2 cells, which are similar to intestinal epithelial cells in structure and biochemistry. Our results showed that ghrelin inhibited IIR/HR-induced oxidative stress and apoptosis by activating GHSR-1α. Moreover, it was found that ghrelin activated the GHSR-1α/Sirt1/FOXO1 signaling pathway. We further inhibited Sirt1 and found that Sirt1 was critical for ghrelin-mediated mitigation of IIR/HR injury. Overall, our data suggest that pretreatment with ghrelin reduces oxidative stress and apoptosis to attenuate IIR/HR injury by binding with GHSR-1α to further activate Sirt1.

Differential impact of a ghrelin receptor antagonist or inverse agonist in the electrical kindling model of epilepsy.

Siamak Beheshti, Shiva Ershadi, Fatemeh Zamani +2 more

Ghrelin is a peptide, which has been shown to affect seizures. However, there is not a consensus about its real impact on the control of seizure severity. We assessed the influence of intra-amygdala injections of a ghrelin receptor (GHSR) antagonist, as well as a GHSR inverse agonist on the electrical kindling-induced seizures. Two unipolar electrodes and a tripolar electrode twisted with a guide cannula were implanted in the skull surface or the basolateral amygdala of adult male rats, respectively. A rapid electrical kindling protocol was applied for kindling epileptogenesis. The stimulations were applied until rats showed three consecutive stage five seizures. Each rat was considered as its control. D-Lys-3-GHRP-6 (1, 12.5, and 25 μg/rat) or [D-Arg, D-phe, D-Trp, heu] substance P (D-SP) (50, 500 and 5000 ng/rat) as the GHSR antagonist or inverse agonist were injected into the basolateral amygdala. Seizure parameters including after-discharge duration (ADD), stage five duration (S5D), and seizure stage (SS) were documented thirty minutes following administration of the drugs or saline. Antagonism of the GHSR in the amygdala, significantly increased seizure induction in the kindled rats, in a dose-dependent manner, and induced spontaneous seizures leading to status epilepticus. Conversely, D-SP had a dose-dependent anticonvulsant activity, indicated by decreased ADD and S5D. The results show that GHSR inverse agonism suppressed seizure severity in the rat amygdala kindling model, whereas GHSR antagonism made seizures more severe. Therefore, when considering the ghrelin system to modulate seizures, it is crucial to note the differential impact of various GHSR ligands.