Growth Hormone Secretagogue Research Articles

Characterization of growth hormone secretagogue small molecule ibutamoren (MK-0677) and its possible metabolites in thoroughbred horses for doping control.

It is important to remember that performance-enhancing agents such as non-peptide growth hormone secretagogues present a significant risk of abuse. Ibutamoren (MK-0677) is a potent, long-acting, selective non-peptide growth hormone secretagogue that can be taken orally. This study examines ibutamoren and its metabolites in thoroughbred horses after oral administration. Liquid chromatography/high-resolution mass spectrometry was used to determine the probable structures of the detected metabolites. In this study, 22 metabolites of ibutamoren were identified (17 phase I and 5 phase II). Oxidation of ibutamoren leads to hydroxylated metabolites (mono and di). The study also detected dissociated side chains (benzyl group and 2-amino-2-methylpropanamide) and hydrogenated metabolites. The glucuronic acid conjugated analogs of ibutamoren were detected during phase II of the study, but no sulfonic acid conjugated analogs were observed. The major metabolites can be detected up to 96 hours after a single dose, and ibutamoren can persist for up to 72 hours. These findings will aid in the detection of ibutamoren and the detection of its illegal use in competitive sports.

Serum Ghrelin in a Sample of Egyptian Epileptic Patients

Ghrelin is a multifunctional hormone constituted of 28 amino acids, which is the endogenous ligand of the synthetic growth hormone secretagogue receptor 1a (GHS-R) ligands. Ghrelin is expressed in different tissues including the central nervous system (CNS). In addition, circulating ghrelin can access different structures of CNS such as hippocampus and ventral tegmental area. Ghrelin has various neuroprotective properties, and it appears to be related to memory retention and formation. In Rolandic epilepsy, although many changes in the physiology of hormones in the neuroendocrine system of patients can occur, the causes of these changes have not been fully elucidated. There are also relations between seizure activity and stages of sleep, which has been shown to affect both endocrine function and sleep. The purpose of this study was to evaluate serum levels of ghrelin in a sample of Egyptian epileptic patients and to evaluate its possible correlations with clinical findings. A total of 60 patients (age: 6.5±1.9) currently receiving antiepileptic drug therapy for Rolandicepilepsy were studied. The control group consisted of 60 healthy volunteers (age: 6.6±2.1) matched for age and gender. In all participants, serum levels of ghrelin were measured using ELISA technique. In the Rolandic epilepsy patients, the mean serum ghrelin level was 175.8±49.1pg/ml, and this was significantly lower than the control group’s level of 445.7±151.4pg/ml (p < 0.001). In conclusion, the significant lower ghrelin serum level in patients with Rolandic epilepsy may support the hypothesis of ghrelin’s antiepilepticpotential and neuroprotective actions.

Fluorescent P‐Hydroxyphosphole for Peptide Labeling through P‐N Bond Formation

AbstractSynthesis of fluorescent P‐hydroxybinaphtylphosphole‐oxide or ‐sulfide was achieved by trapping a binaphtyl dianion with methyl dichlorophosphite or P‐(N,N‐diethylamino)dichlorophosphine, followed by oxidation or sulfuration of the P‐center. After saponification or acid hydrolysis, the P‐hydroxyphospholes were coupled to peptides using the coupling agent BOP, under the conditions required for the synthesis in solution or on a solid support. This new method was illustrated by the labeling of the JMV2959, a potent antagonist of the Growth Hormone Secretagogue Receptor type 1a (GHS−R1a). The labeled conjugates were used to characterize GHSR ligands by competition assays, based on Fluorescence Resonance Energy Transfer (FRET). Such P‐hydroxyphosphole‐oxide or ‐sulfide constitute a promising new class of compact fluorophores with large Stokes shift, for labeling biomolecules by grafting through the phosphorus atom.

Increased growth hormone secretagogue receptor-1a (GHSR-1a) in hypothalamus during olanzapine treatment in rats

Weight gain is the one of the most important factors which increases global burden of psychiatric disorder. Second-generation antipsychotics, olanzapine (Olz) and valproic acid (Vpa) in particular, are held responsible for weight gain. However, it is still uncertain how these drugs cause this. Thus, the rats selected for the experiment were randomly divided into 3 groups. The 1st group received only 0.5 ml saline solution intraperitoneally (n = 20, control group); the second group was given 200 mg / kg Vpa intraperitoneally (n = 20, Vpa group) and 2 mg / kg Olz was given intraperitoneally to the 3rd group (n = 20, Olz group) between 8 and 10 am for 30 days. We examined serum leptin, adiponectin, resistin, TNF-α, IL-6, ghrelin level and, the amount of ghrelin secreting cells in the stomach and growth hormone secretagogue receptor-1a (GHSR-1a, ghrelin receptor) expression in the hypothalamus. The hypothalamic GHS-1a receptor index was significantly higher in the Olz group compared with the control group and Vpa group (p = 0.036 and p = 0.016 respectively). Ghrelin immune positive cell index in stomach was statistically significantly lower in the Vpa group compared with the control and Olz groups (p = 0.028 and p = 0.013 respectively) There was no difference between the groups in terms of serum leptin, resistin, IL-6 and ghrelin levels. In the Vpa group, a statistically significant increase was found in serum adiponectin level compared with both the control group and the Olz group (p = 0009 and p = 0024 respectively) and, significant decrease was found in serum TNF-α level compared to Olz group (p = 0007). In conclusion, we found that the main cause of weight gain in Olz use was the increase in the number of hypothalamic ghrelin receptors. Investigating the mechanism by which Olz increases the number of ghrelin receptors may help to develop effective treatment strategies in preventing obesity in psychiatric patients.

Binding Domain Characterization of Growth Hormone Secretagogue Receptor.

Background and ObjectivesActivation of ghrelin receptor growth hormone secretagogue receptor (GHS-R) by endogenous or synthetic ligands amplifies pulsatile release of growth hormone (GH) and enhances food intake, very relevant to development and growth. GHS-R is a G-protein coupled receptor that has great druggable potential. Understanding the precise ligand and receptor interactions is crucial to advance the application of GHS-R.Materials and MethodsWe used radiolabeled ligand-binding assay and growth hormone release assay to assess the binding and functional characteristics of GHS-R to synthetic agonists MK-0677 and GHS-25, as well as to endogenous peptide ligand ghrelin. We analyzed the ligand-dependent activity of GHS-R by measuring aequorin-based [Ca++]i responses. To define a ligand-binding pocket of GHS-R, we generated a series of human/puffer fish GHS-R chimeras by domain swapping, as well as a series of mutants by site-directed mutagenesis.ResultsWe found that the synthetic ligands have high binding affinity to GHS-R in the in vitro competitive binding assay. Remarkably, the in vivo GH secretagogue activity is higher with the synthetic agonists MK-0677 and GHS-25 than that of ghrelin. Importantly, the activity was completely abolished in GHS-R knockout mice. In GHS-R chimera analysis, we identified the C-terminal region, particularly the transmembrane domain 6 (TM6), to be critical for the ligand-dependent activity. Our site-directed mutagenesis study further revealed that amino acid residues D99 and W276 in GHS-R are essential for ligand binding. Interestingly, critical residues distinctively interact with different ligands, MK-0677 activation depends on E124, while ghrelin and GHS-25 preferentially interact with F279.ConclusionThe ligand-binding pocket of human GHS-R is mainly defined by interactive residues in TM6 and the adjacent region of the receptor. This novel finding in GHS-R binding domains advances the structural/ functional understanding of GHS-R, which will help to select/design better GHS-R agonists/ antagonists for future therapeutic applications.

Acylation, a Conductor of Ghrelin Function in Brain Health and Disease.

Acyl-ghrelin (AG) is an orexigenic hormone that has a unique octanoyl modification on its third serine residue. It is often referred to as the “hunger hormone” due to its involvement in stimulating food intake and regulating energy homeostasis. The discovery of the enzyme ghrelin-O-acyltransferase (GOAT), which catalyses ghrelin acylation, provided further insights into the relevance of this lipidation process for the activation of the growth hormone secretagogue receptor (GHS-R) by acyl-ghrelin. Although acyl-ghrelin is predominantly linked with octanoic acid, a range of saturated fatty acids can also bind to ghrelin possibly leading to specific functions. Sources of ghrelin acylation include beta-oxidation of longer chain fatty acids, with contributions from fatty acid synthesis, the diet, and the microbiome. In addition, both acyl-ghrelin and unacyl-ghrelin (UAG) have feedback effects on lipid metabolism which in turn modulate their levels. Recently we showed that whilst acyl-ghrelin promotes adult hippocampal neurogenesis and enhances memory function, UAG inhibits these processes. As a result, we postulated that the circulating acyl-ghrelin:unacyl-ghrelin (AG:UAG) ratio might be an important regulator of neurogenesis and cognition. In this review, we discuss emerging evidence behind the relevance of ghrelin acylation in the context of brain physiology and pathology, as well as the current challenges of identifying the provenance of the acyl moiety.

Multiple roles of ghrelin in breast cancer.

Breast cancer is one of the most threatening malignant tumors in women worldwide; hence, investigators are continually performing novel research in this field. However, an accurate prediction of its prognosis and postoperative recovery remains difficult. The severity of breast cancer is patient-specific and affected by several health factors; thus, unknown mechanisms may affect its progression. This article analyzes existing literature on breast cancer, ranging from the discovery of ghrelin to its present use, and aims to provide a reference for future research into breast cancer mechanisms and treatment-plan improvement. Various parts of ghrelin have been associated with breast cancer by direct or indirect evidence. The ghrelin system may encompass the direction of expanding breast cancer treatment methods and prognostic indicators. Therefore, we compiled almost all studies on the relationship between the ghrelin system and breast cancer, including unacylated ghrelin, its GHRL gene, ghrelin O-acyltransferase, the receptor growth hormone secretagogue receptor, and several splice variants of ghrelin to lay the foundation for future research.

Growth hormone secretagogue peptide A233 upregulates Mx expression in teleost fish in vitro and in vivo.

Aquaculture constitutes an alternative source for food production and contributes to a reduction in the indiscriminate catching of aquatic organisms in their natural environment. However, high mortality during the larval state remains a challenge in this sector, mainly because of factors such as diet and diseases caused by pathogens. Therefore, growth and health management is a key strategy for sustainable aquaculture. Synthetic growth hormone secretagogues (GHSs) are a family of ligands that can stimulate pituitary growth hormone release as well as the function of ghrelin, contributing to the immune responses in a variety of vertebrates, including fish. The A233 decapeptide is a GHS with a demonstrated impact on growth, immune system function, and antioxidant defense in tilapia fish, but no antiviral activity has been described for this peptide. Here, using an in vitro model (TRG-2 cells) and two in vivo models (sea bream [Sparus aurata]) and zebrafish [Danio rerio]), we demonstrate for the first time the potential antiviral effect of A233 in teleost fish.

Effects of intracerebroventricular injection of corticotrophin releasing factor on the gene expression of ghrelin and corticotrophin releasing factor receptors in broiler chickens.

This study aimed to investigate the effects of corticotropin-releasing factor (CRF) on the feed intake of broiler chickens and explore its influencing mechanism. The study included two trials. In trial 1, 32 male broiler chickens (Arbor Acres, Gallus gallus domesticus) were given ventricle buried tubes, and they were allowed to recover for 3 days. At 8:00 AM, intracerebroventricular (ICV) injection with CRF or normal saline was performed in 10-day-old broiler chickens, which were divided into the 5, 10, and 20 μg and control (normal saline) groups according to the dose of CRF injection. In trial 2, chickens were divided into the 10 μg and control group (physiological saline) to repeat trial 1. Results of trial 1 showed that the cumulative amount of feed intake in the 10 or 20 μg groups was considerably lower than that of the control group after ICV injection with CRF. The lowest amount of feed intake was obtained with the addition of 10 μg of CRF. In trial 2, the expression of ghrelin in the hypothalamus injected with 10 μg of CRF increased significantly, but the expression of ghrelin in various sections of the small intestine considerably decreased. The expression of CRF receptor subtypes 1 (CRFR1) in the hypothalamus and some parts of the small intestine remarkably increased, and the expression of CRF receptor subtypes 2 (CRFR2) increased only in the duodenum, whereas the expression of growth hormone secretagogue receptor (GHSR-1α) in the jejunum and ileum increased considerably after ICV injection of 10 μg of CRF. The CRF at 10 μg increased ghrelin expression in the hypothalamus and CRFR1 expression in the small intestine, and this phenomenon was related to the suppressed feed intake of broiler chickens.

Design and characterization of a triazole-based growth hormone secretagogue receptor modulator inhibiting the glucoregulatory and feeding actions of ghrelin

The growth hormone secretagogue receptor (GHSR) is a G protein-coupled receptor that regulates essential physiological functions. In particular, activation of GHSR in response to its endogenous agonist ghrelin promotes food intake and blood glucose increase. Therefore, compounds aimed at blocking GHSR signaling constitute potential options against obesity-related metabolic disorders. We have previously developed potent ligands of GHSR based on a triazole scaffold. Here, we report a new 3,4,5-trisubstituted 1,2,4-triazole compound, named JMV 6616, that potently blocks GHSR activity in vitro and in vivo. Specifically, in HEK293T cells JMV 6616 behaves as an inverse agonist since it binds to GHSR and inhibits its ghrelin-independent signaling. Accordingly, using purified labeled GHSR assembled into lipid nanodiscs we found that JMV 6616 decreases GHSR-catalyzed G protein activation and stabilizes an inactive receptor conformation. Importantly, JMV 6616 also acts on native GHSR since it blocks the insulinostatic effect of ghrelin in pancreatic islets. In mice, JMV 6616 inhibits blood glucose-raising effects of ghrelin treatment and the orexigenic actions of acute ghrelin administration. Together, our data suggest that this triazole-derived modulator of GHSR holds promise to mitigate several pathological features associated with eating and metabolic disorders.

MRAP2 inhibits β-arrestin recruitment to the ghrelin receptor by preventing GHSR1a phosphorylation

The melanocortin receptor accessory protein 2 (MRAP2) is essential for several physiological functions of the ghrelin receptor growth hormone secretagogue receptor 1a (GHSR1a), including increasing appetite and suppressing insulin secretion. In the absence of MRAP2, GHSR1a displays high constitutive activity and a weak G-protein–mediated response to ghrelin and readily recruits β-arrestin. In the presence of MRAP2, however, G-protein–mediated signaling via GHSR1a is strongly dependent on ghrelin stimulation and the recruitment of β-arrestin is significantly diminished. To better understand how MRAP2 modifies GHSR1a signaling, here we investigated the role of several phosphorylation sites within the C-terminal tail and third intracellular loop of GHSR1a, as well as the mechanism behind MRAP2-mediated inhibition of β-arrestin recruitment. We show that Ser252 and Thr261 in the third intracellular loop of GHSR1a contribute to β-arrestin recruitment, whereas the C-terminal region is not essential for β-arrestin interaction. Additionally, we found that MRAP2 inhibits GHSR1a phosphorylation by blocking the interaction of GRK2 and PKC with the receptor. Taken together, these data suggest that MRAP2 alters GHSR1a signaling by directly impacting the phosphorylation state of the receptor and that the C-terminal tail of GHSR1a prevents rather than contribute to β-arrestin recruitment.

The neuropeptide cortistatin attenuates Th17 cell response through inhibition of glycolysis via GHSR1

The neuropeptide cortistatin (CST) has been reported to attenuate Th17 cell response in multiple disease models, but the mechanism of action remains obscure. Here, we show that either overexpression or exogenous addition of CST obviously restricts Th17 cell differentiation. As metabolic reprogramming plays an important role in Th17 cell development, we explore whether CST inhibits Th17 cell differentiation by regulating glycolysis. The results show that CST substantially attenuates the glycolysis during Th17 differentiation and down-regulates the mRNA expression of myelocytomatosis oncogene (Myc) and hexokinase 2 (HK2), the glycolysis rate-limiting enzyme. Following the overexpression of Myc and HK2, the inhibitory effect of CST on Th17 differentiation nearly disappears, suggesting that Myc-HK2 pathway is deeply involved. Furthermore, growth hormone secretagogue receptor 1 (GHSR1) is identified as the key receptor subtype for CST attenuating glycolysis and Th17 cell differentiation by the combined uses of CST with various receptor subtype blockers. The knockdown of GHSR1 abrogates the inhibition of CST on Th17 differentiation and glycolysis. Finally, in the colitis mice induced by dextran sulfate sodium, an intraperitoneal injection of CST markedly inhibits Th17 cell response and down-regulates the expression of HK2 in the Th17 cells, which is reversed by the combined use of GHSR1 antagonist. These findings suggest that inhibition of glycolysis is the key pathway for CST attenuating Th17 cell response, and GHSR1, Myc and HK2 are potential therapeutic targets of Th17 cell-related diseases.

Glucagon-stimulated copeptin measurements in the differential diagnosis of diabetes insipidus: a double-blind, randomized, placebo-controlled study.

The differential diagnosis of diabetes insipidus is challenging. The most reliable approaches are copeptin measurements after hypertonic saline infusion or arginine, which is a known growth hormone secretagogue but has recently also been shown to stimulate the neurohypophysis. Similar to arginine, glucagon stimulates growth hormone release, but its effect on the neurohypophysis is poorly studied. Double-blind, randomized, placebo-controlled trial including 22 healthy participants, 10 patients with central diabetes insipidus, and 10 patients with primary polydipsia at the University Hospital Basel, Switzerland. Each participant underwent the glucagon test (s.c. injection of 1 mg glucagon) and placebo test. The primary objective was to determine whether glucagon stimulates copeptin and to explore whether the copeptin response differentiates between diabetes insipidus and primary polydipsia. Copeptin levels were measured at baseline, 30, 60, 90, 120, 150, and 180 min after injection. In healthy participants, glucagon stimulated copeptin with a median increase of 7.56 (2.38; 28.03) pmol/L, while placebo had no effect (0.10 pmol/L (-0.70; 0.68); P < 0.001). In patients with diabetes insipidus, copeptin showed no relevant increase upon glucagon, with an increase of 0.55 (0.21; 1.65) pmol/L, whereas copeptin was stimulated in patients with primary polydipsia with an increase of 15.70 (5.99; 24.39) pmol/L. Using a copeptin cut-off level of 4.6pmol/L had a sensitivity of 100% (95% CI: 100-100) and a specificity of 90% (95% CI: 70-100) to discriminate between diabetes insipidus and primary polydipsia. Glucagon stimulates the neurohypophysis, and glucagon-stimulated copeptin has the potential for a safe, novel, and precise test in the differential diagnosis of diabetes insipidus.

Role of the Ghrelin System in Colorectal Cancer.

The ghrelin system contains several components (e.g., ghrelin with growing number of alternative peptides, growth hormone secretagogue receptors (GHS-Rs), and ghrelin-O-acyl-transferase (GOAT) and participates in regulation of a number of key processes of gastrointestinal (GI) tract cancer progression, including cell proliferation, migration, invasion, apoptosis, inflammation, and angiogenesis. However, its exact role in promoting or inhibiting cancer progression is still unclear. Colorectal cancer (CRC) is one of the most common human malignancies worldwide. Molecular studies suggest an autocrine/paracrine mechanism for the secretion of ghrelin in colorectal carcinogenesis and its contribution to its initial stages. However, the signalling pathways of CRC development involving the ghrelin system are poorly understood. Potential mechanisms of colon carcinogenesis involving components of the ghrelin system were previously described in an animal model and in in vitro studies. However, the diagnostic–prognostic role of serum ghrelin concentrations, tissue expression, or genetic changes of this system in various stages of CRC progression remains an open case. Thus, the aim of this study is to discuss the role of the ghrelin system in colon carcinogenesis, diagnostics and CRC prognostics, as well as the results of studies on the use of ghrelin and its analogues in the therapy of CRC-related syndromes (e.g., cachexia and sarcopenia).

GHSR controls food deprivation-induced activation of CRF neurons of the hypothalamic paraventricular nucleus in a LEAP2-dependent manner.

Prolonged fasting is a major challenge for living organisms. An appropriate metabolic response to food deprivation requires the activation of the corticotropin-releasing factor-producing neurons of the hypothalamic paraventricular nucleus (PVHCRF neurons), which are a part of the hypothalamic-pituitary-adrenal axis (HPA), as well as the growth hormone secretagogue receptor (GHSR) signaling, whose activity is up- or down-regulated, respectively, by the hormones ghrelin and the liver-expressed antimicrobial peptide 2 (LEAP2). Since ghrelin treatment potently up-regulates the HPA axis, we studied the role of GHSR in mediating food deprivation-induced activation of the PVHCRF neurons in mice. We estimated the activation of the PVHCRF neurons, using immuno-staining against CRF and the marker of neuronal activation c-Fos in brain sections, and assessed plasma levels of corticosterone and glucose in different pharmacologically or genetically manipulated mouse models exposed, or not, to a 2-day food deprivation protocol. In particular, we investigated ad libitum fed or food-deprived male mice that: (1) lacked GHSR gene expression, (2) had genetic deletion of the ghrelin gene, (3) displayed neurotoxic ablation of the hypothalamic arcuate nucleus, (4) were centrally treated with an anti-ghrelin antibody to block central ghrelin action, (5) were centrally treated with a GHSR ligand that blocks ghrelin-evoked and constitutive GHSR activities, or (6) received a continuous systemic infusion of LEAP2(1-12). We found that food deprivation results in the activation of the PVHCRF neurons and in a rise of the ghrelin/LEAP2 molar ratio. Food deprivation-induced activation of PVHCRF neurons required the presence and the signaling of GHSR at hypothalamic level, but not of ghrelin. Finally, we found that preventing the food deprivation-induced fall of LEAP2 reverses the activation of the PVHCRF neurons in food-deprived mice, although it has no effect on body weight or blood glucose. Food deprivation-induced activation of the PVHCRF neurons involves ghrelin-independent actions of GHSR at hypothalamic level and requires a decrease of plasma LEAP2 levels. We propose that the up-regulation of the actions of GHSR associated to the fall of plasma LEAP2 level are physiologically relevant neuroendocrine signals during a prolonged fasting.

Serum levels of ghrelin and LEAP2 in patients with type 2 diabetes mellitus: correlation with circulating glucose and lipids.

Objective Ghrelin regulates body weight, food intake, and blood glucose. It also regulates insulin secretion from pancreatic islet cells. LEAP2 is a newly discovered endogenous ligand of the growth hormone secretagogue’s receptor (GHSR). It not only antagonizes the stimulation of GHSR by ghrelin but also inhibits the constitutive activation of GHSR as an inverse agonist. Type 2 diabetes (T2D) patients have endocrine disorders with metabolic imbalance. Plasma levels of ghrelin and LEAP2 may be changed in obese and T2D patients. However, there is no report yet on circulating LEAP2 levels or ghrelin/LEAP2 ratio in T2D patients. In this study, fasting serum ghrelin and LEAP2 levels in healthy adults and T2D patients were assessed to clarify the association of two hormones with different clinical anthropometric and metabolic parameters.Design A total of 16 females and 40 males, ages 23–68 years old normal (n = 27), and T2D patients (n = 29) were enrolled as a cross-sectional cohort.Results Serum levels of ghrelin were lower but serum levels of LEAP2 were higher in T2D patients. Ghrelin levels were positively correlated with fasting serum insulin levels and HOMA-IR in healthy adults. LEAP2 levels were positively correlated with age and hemoglobin A1c (HbA1c) in all tested samples. Ghrelin/LEAP2 ratio was negatively correlated with age, fasting blood glucose, and HbA1c.Conclusions This study demonstrated a decrease in serum ghrelin levels and an increase in serum LEAP2 levels in T2D patients. LEAP2 levels were positively correlated with HbA1c, suggesting that LEAP2 was associated with T2D development. The ghrelin/LEAP2 ratio was closely associated with glycemic control in T2D patients showing a negative correlation with glucose and HbA1c.

Molar extraction alters gastric mucosa and ghrelin expression in rat stomach: A preliminary study

Objectives: Ghrelin is a key regulator of food intake and is considered a hunger hormone that affects cognition, memory, glucose metabolism, and antidepressant effects. Altered occlusion, such as a loss of molars, has been thought to retard digestive function. However, the association between occlusion and digestive function remains poorly understood. Here, we aimed to explore the effect of bilateral maxillary molar extraction on the gastrointestinal mucosa of growing rats and the expression of ghrelin and its receptor, growth hormone secretagogue receptor (GHSR). Material and Methods: Twenty-four male 5-week-old Wistar rats were divided into control (CON) and experimental (EXP) groups (n = 12/group). The rats in the EXP group underwent extraction of the bilateral maxillary first, second, and third molars under general anesthesia. Rats in the CON group underwent a sham operation. All rats in both the CON and EXP groups were fed a powder diet and water ad libitum. The body weight of all rats was monitored throughout the EXP period. Rats in both the CON and EXP groups were euthanized on days 14 and 28, and the stomachs were isolated and subjected to histological analysis. Paraffin serial sections were prepared using a microtome for hematoxylin-eosin and immunohistochemical staining using anti-ghrelin and anti-GHSR antibodies. The distribution and expression of ghrelin-immunopositive and GHSR cells were detected and observed under a light microscope. Data were statistically analyzed using t-tests (P &lt; 0.05). Results: There were no significant differences in body weight between the CON and EXP groups throughout the EXP period. Histological analysis showed that the area of the submucosa (ASM), and the number of ghrelinimmunopositive cells were significantly decreased in the EXP group compared with the CON group on day 14. Alternatively, there was no significant difference in the ASM and the number of ghrelin-immunopositive cells between the CON and EXP groups on day 28, whereas the number of ghrelin receptors showed no differences across groups. Furthermore, the number of eosinophilic blood cells significantly increased in the EXP group on days 14 and 28. Conclusion: Our findings suggest that bilateral maxillary molar extraction may trigger stomach mucosal changes and alter digestive function through ghrelin expression in rats. This is the first report that occlusal deficiency could alter ghrelin expression in the mucosa of the rat stomach, thus raising concerns about the consequential role of ghrelin.

Structural Insights into the Intrinsically Disordered GPCR C-Terminal Region, Major Actor in Arrestin-GPCR Interaction.

Arrestin-dependent pathways are a central component of G protein-coupled receptor (GPCRs) signaling. However, the molecular processes regulating arrestin binding are to be further illuminated, in particular with regard to the structural impact of GPCR C-terminal disordered regions. Here, we used an integrated biophysical strategy to describe the basal conformations of the C-terminal domains of three class A GPCRs, the vasopressin V2 receptor (V2R), the growth hormone secretagogue or ghrelin receptor type 1a (GHSR) and the β2-adernergic receptor (β2AR). By doing so, we revealed the presence of transient secondary structures in these regions that are potentially involved in the interaction with arrestin. These secondary structure elements differ from those described in the literature in interaction with arrestin. This suggests a mechanism where the secondary structure conformational preferences in the C-terminal regions of GPCRs could be a central feature for optimizing arrestins recognition.

Association of obesity in T2DM with differential polymorphism of ghrelin, growth hormone secretagogue receptor-1 and telomeres maintenance genes.

Although obesity and T2DM comorbidity is too frequent, the molecular basis of diabetic obesity is largely unexplained and barely investigated. Cross-sectional studies were conducted in Kingdom of Saudi Arabia (KSA) in 2013 and Kuwait in 2019. Fasting blood samples were obtained from a total of 216 T2DM patients (104 from KSA) and 193 nondiabetic subjects (93 from KSA) after their consents. Eight SNPs in 5 genes known to be associated with both obesity and T2DM, ghrelin (GHRL) and growth hormone secretagogue receptor -GHSR (KSA) and telomeres maintenance genes (Kuwait) were genotyped by rtPCR. Both patients and controls were grouped into obese and non-obese and sub-grouped into 4-BMI- grades: normal, overweight (OW), obese (OBS) and severely obese (SOBS). Showed that the only SNP which was distinguished between all groups/subgroups in all study subjects was the ACYP2 rs6713088G/C, where the common CC genotype was under-expressed in the obese compared to non-obese diabetics (17.8% vs. 40.4%, p 0.01) and between the 4-BMI-grade (p 0.025). Interestingly the same genotype was over-expressed in obese compared to non-obese non-diabetics (50% vs. 27.6%, p 0.04). Furthermore, the GHRL (rs27647C/T), GHSR (rs509030G/C) and TERC (rs12696304G/C) MAFs were significantly low in normal BMI patients; p=0.034, 0.008 and 0.011, respectively. This is the first report about the molecular distinction between the obese and non-obese diabetics, it showed the association of rs6713088G/C mutant allele with diabetic obesity, while the GHRL, GHSR and TERC SNPs were differentially expressed based on the BMI-grades.

Comparison of the effects of different calorie amounts of enteral nutrition in hypercatabolism associated with ghrelin-POMC in endotoxemic rats

BackgroundHypercatabolism often occurs in critically ill patients, and it increases infection rates and mortality in these patients. Enteral nutrition (EN) is commonly used in case of hypercatabolism. However, the effect of amount of calories in EN on hypercatabolism remains unexplored.ObjectiveHere, we compared the effect of low-calorie, medium-calorie and high-calorie EN on hypercatabolism in the acute phase of endotoxemia, which is associated with gastrointestinal hormones and hypothalamic neuropeptide proopiomelanocortin (POMC).MethodsOverall 84 adult male Sprague–Dawley rats were used for research. A set of rats were divided into 5 groups, Control (NS) and lipopolysaccharide (LPS) groups were fed a standard chow diet; LPS + L (LPS + 40 kcal/kg/day EN), LPS + M (LPS + 80 kcal/kg/day EN) and LPS + H (LPS + 120 kcal/kg/day EN) groups received EN through a gastric tube for 3 days. Another set of rats were used for parallel control experiment and divided into 5 groups: NS + F (saline + fasting) and LPS + F (LPS + fasting) groups were given no food, NS + L (saline + 40 kcal/kg/day EN), NS + M (saline + 80 kcal/kg/day EN) and NS + H (saline + 120 kcal/kg/day EN) groups received EN through a gastric tube for 3 days. Hypercatabolism was evaluated by assessing skeletal muscle protein synthesis and atrophy, insulin resistance, and corticosterone levels. Moreover, serum inflammatory factors, gastrointestinal hormones, hypothalamic ghrelin, growth hormone secretagogue receptor-1α, hypothalamic neuropeptide, and intestinal injury indicators were detected.ResultsLow-calorie EN effectively increased serum and hypothalamic ghrelin possibly due to slight intestinal barrier damage, thereby decreasing hypothalamic POMC expression; consequently, it alleviated rat insulin resistance, reduced blood cortisol levels and muscle atrophy, and improved the survival rate of rats in the acute phase of endotoxemia. Interestingly, with an increase in calories in enteral nutrition, the aforementioned effects did not increase.ConclusionsLow-calorie EN could effectively increase gastrointestinal hormone ghrelin by reducing intestinal damage and suppressing POMC expression to ameliorate hypercatabolism when compared with medium-calorie and high-calorie EN. Therefore Low-calorie EN may be preferred for providing EN in the acute stage of endotoxemia.