Regulation of ghrelin receptor by microbial and inflammatory signals in human osteoblasts

Abstract: Recently, it has been suggested that the anti-inflammatory hormone ghrelin (GHRL) and its receptor GHS-R may play a pivotal role in periodontal health and diseases. However, their exact regulation and effects in periodontitis are not known. The aim of this in-vitro study was to investigate the effect of microbial and inflammatory insults on the GHS-R1a expression in human osteoblast-like cells. MG-63 cells were exposed to interleukin (IL)-1β and Fusobacterium nucleatum in the presence and absence of GHRL for up to 2 d. Subsequently, gene expressions of GHS-R1a, inflammatory mediators and matrix metalloproteinase were analyzed by real-time PCR. GHS-R protein synthesis and NF-κB p65 nuclear translocation were assessed by immunocytochemistry and immunofluorescence microscopy, respectively. IL-1β and F. nucleatum caused a significant upregulation of GHS-R1a expression and an increase in GHS-R1a protein. Pre-incubation with a MEK1/2 inhibitor diminished the IL-1β-induced GHS-R1a upregulation. IL-1β and F. nucleatum also enhanced the expressions of cyclooxygenase 2, CC-chemokine ligand 2, IL-6, IL-8, and matrix metalloproteinase 1, but these stimulatory effects were counteracted by GHRL. By contrast, the stimulatory actions of IL-1β and F. nucleatum on the GHS-R1a expression were further enhanced by GHRL. Our study provides original evidence that IL-1β and F. nucleatum regulate the GHS-R/GHRL system in osteoblast-like cells. Furthermore, we demonstrate for the first time that the proinflammatory and proteolytic actions of IL-1β and F. nucleatum on osteoblast-like cells are inhibited by GHRL. Our study suggests that microbial and inflammatory insults upregulate GHS-R1a, which may represent a protective negative feedback mechanism in human bone.

Effect of point-moxibustion on ghrelin and GHSR-1a expressions in lateral septal nucleus of rats with diabetic gastroparesis / 针灸推拿医学（英文版）

Objective:To observe the effect of point-moxibustion on gastrointestinal motility,mRNA and protein expressions of ghrelin and growth hormone secretagogue receptor 1a (GHSR-1a) in lateral septal nucleus of rats with diabetic gastroparesis (DGP),and to investigate the central regulatory mechanism of DGP treatment with point-moxibustion.Methods:Forty SPF-grade Sprague-Dawley (SD) rats were randomly divided into a blank group,a model group,an electroacupuncture (EA) group and a point-moxibustion group,with 10 rats in each group.A DGP rat model was established by intraperitoneal injection of 2％ streptozotocin (STZ) with 8-week irregular high-sugar and high-fat diet in the model group,the EA group and the point-moxibustion group;and rats in the blank group were injected intraperitoneally with 0.1 mmoL/L (pH 4.5) citric acid-sodium citrate buffer with 8-week normal diet.Eight weeks later,rats in the EA group were treated by EA at Zusanli (ST 36),Liangmen (ST 21) and Sanyinjiao (SP 6);while rats in the point-moxibustion group were treated by point-moxibustion at Zusanli (ST 36),Liangmen (ST 21) and Sanyinjiao (SP 6) for successive 15 d.Rats in the blank group and the model group were fixed as the control without intervention.After treatment,intestinal propulsion rate and gastric emptying rate were measured.The mRNA and protein expressions of ghrelin and GHSR-1a in the lateral septal nucleus were detected by real-time polymerase chain reaction (RT-PCR) and Western blot (WB).Results:Compared with the blank group,the intestinal propulsion rate and gastric emptying rate of the model group were significantly lower (both P＜0.01);compared with the model group,the intestinal propulsion rate and gastric emptying rate of the EA group and the point-moxibustion group increased significantly (all P＜0.05).The mRNA and protein expressions of ghrelin and GHSR-1a were lower in the model group than those in the blank group (all P＜0.01).The mRNA and protein expressions of ghrelin and GHSR-1a were significantly higher in the EA group and the point-moxibustion group than those in the model group (all P＜0.05).There were no statistically significant differences between the EA group and the point-moxibustion group (all P＞0.05).Conclusion:Point-moxibustion at Zusanli (ST 36),Liangmen (ST 21) and Sanyinjiao (SP 6) can increase the intestinal propulsion rate and gastric emptying rate of DGP rats,and promote the mRNA and protein expressions of ghrelin and GHSR-1a in the central nervous system.The mechanism may be related to the activation of ghrelin pathway in hypothalamic arcuate nucleus-lateral septal nucleus.

Advances in Study on Relationship Between Ghrelin/ GHS-R Agonist,MTL/ MTL-R Agonist and Gastrointestinal Motility / 胃肠病学

Ghrelin and motilin (MTL) are mainly secreted by digestive tract,and they both can promote gastrointestinal motility. Disorder of gastrointestinal motility (DGIM)is a gastrointestinal motility or sensory disease mainly caused by neuroregulatory disorder,its main symptoms are nausea,vomiting,abdominal pain and abdominal distension. More and more studies have indicated that ghrelin,MTL and their receptor agonists are closely related to DGIM. This article reviewed the advances in studies on relationship between ghrelin/ GHS-R agonist,MTL/ MTL-R agonist and DGIM.

Leu72Met and Other Intronic Polymorphisms in the GHRL and GHSR Genes Are Not Associated with Type 2 Diabetes Mellitus, Insulin Resistance, or Serum Ghrelin Levels in a Saudi Population

BACKGROUND: Ghrelin (GHRL), a gastric peptide encoded by the GHRL gene, is known to be involved in energy homeostasis via its G protein receptor, encoded by the growth hormone secretagogue receptor (GHSR) gene. Some studies have shown associations between plasma GHRL levels and GHRL single-nucleotide polymorphisms (SNPs), namely the Leu72Met polymorphism (rs696217 TG), with type 2 diabetes mellitus (T2DM) and insulin resistance (IR), while others have not. The controversies in these associations raise the issue of ‘which SNPs in which populations.’ The aim of this study was to investigate whether SNPs in GHRL and/or GHSR genes were associated with T2DM, IR, or plasma GHRL levels among Arab Saudis. METHODS: Blood was collected from 208 Saudi subjects with (n=107) and without (n=101) T2DM. DNA samples from these subjects were analyzed by real-time polymerase chain reaction to genotype five intronic SNPs in the GHRL (rs696217 TG, rs27647 CT, rs2075356 CT, and rs4684677 AT) and GHSR (rs509030 GC) genes. In addition, plasma GHRL levels were measured by a radioimmunoassay. RESULTS: None of the SNPs were associated with T2DM, IR, or plasma GHRL levels. The frequencies of the alleles, genotypes, and haplotypes of the five SNPs were comparable between the T2DM patients and the non-diabetic subjects. A large number of the GHRL haplotypes indicates the molecular heterogeneity of the preproghrelin gene in this region. CONCLUSION: Neither the Leu72Met polymorphism nor the other intronic GHRL and GHSR SNPs were associated with T2DM, IR, or GHRL levels. Further investigations should be carried out to explain the molecular basis of the association of the GHRL peptide with T2DM and IR.

Role of Ghrelin in development and progression of nonalcoholic fatty liver disease / 临床肝胆病杂志

The incidence of nonalcoholic fatty liver disease (NAFLD) has been increasing in China year by year, and NAFLD has become the second most common liver disease after viral hepatitis. Its development is closely associated with insulin resistance and oxidative stress and NAFLD is one of the important components of metabolic syndrome. Ghrelin is a newly discovered endogenous ligand for growth hormone secretagogue and has broad biological functions. Ghrelin not only affects the metabolic process of glucose and lipids, but also plays an important role in the development and progression of NAFLD. In this review, the role of endogenous Ghrelin expression in the development and progression of NAFLD is briefly summarized and the Ghrelin regulation in the development and progression of NAFLD is pointed out, which will provide new approaches to the clinical treatment of NAFLD.

Role of Ghrelin in the Pathophysiology of Gastrointestinal Disease

Ghrelin is a 28-amino-acid peptide that plays multiple roles in humans and other mammals. The functions of ghrelin include food intake regulation, gastrointestinal (GI) motility, and acid secretion by the GI tract. Many GI disorders involving infection, inflammation, and malignancy are also correlated with altered ghrelin production and secretion. Although suppressed ghrelin responses have already been observed in various GI disorders, such as chronic gastritis, Helicobacter pylori infection, irritable bowel syndrome, functional dyspepsia, and cachexia, elevated ghrelin responses have also been reported in celiac disease and inflammatory bowel disease. Moreover, we recently reported that decreased fasting and postprandial ghrelin levels were observed in female patients with functional dyspepsia compared with healthy subjects. These alterations of ghrelin responses were significantly correlated with meal-related symptoms (bloating and early satiation) in female functional dyspepsia patients. We therefore support the notion that abnormal ghrelin responses may play important roles in various GI disorders. Furthermore, human clinical trials and animal studies involving the administration of ghrelin or its receptor agonists have shown promising improvements in gastroparesis, anorexia, and cancer. This review summarizes the impact of ghrelin, its family of peptides, and its receptors on GI diseases and proposes ghrelin modulation as a potential therapy.

Ghrelin participates in the two-way regulation of the motility of the small intestinal smooth muscle in rats / 中华普通外科杂志

Objective To investigate the effect and mechanism of Ghrelin on the contraction and relaxation of rat small intestinal smooth muscle. Methods The effect of different concentrations of Ghrelin (0;20;40;80 μg/kg) on the small intestinal transit in vagotomized rats in vivo and Ghrelin (0.01; 0.1;0.5 ; 1.0 μmol/L) on the contraction and relaxation of rat small intestinal smooth muscle strips in vitro was observed,the locations of Ghrelin receptors (GHS-R1 a) in small intestinal muscle layers were detected by immunofluorescency. Results Ghrelin dose-dependently increases small intestinal transit (( 25.4 ± 1.0)％,(33.7 ± 1.9)％,(39.3 ±2.4)％,(44.7 ±2.1)％),enhances the contraction ((67.0 ±2.4)％,(149.5 ±3.3)％,(187.1 ±4.7)％,(213.5 ±3.4)％) and relaxation ((35.3 ± 1.1)％,(62.9 ± 3.8 ) ％,( 79.6 ± 2.7 ) ％,( 94.6 ± 2.2 ) ％ ) of smooth muscle strips mediated by carbachol.Ghrelin receptors were mainly located on membrane of the nerve cells in the muscle layers,while no receptors exist on membrane of smooth muscle cells. Conclusions Ghrelin enhances the effect of contraction and relaxation of rat small intestinal smooth muscle mediated by cholinergic neurotransmitters activating nerve cells in the enteric plexus.

Effect and mechanism of Ghrelin on the colonic motility of diabetic mice / 中国现代普通外科进展

Objective:To investigate colonic motility effect and mechanism of Ghrelin in diabetic mice.Methods:In vivo,the effects of Ghrelin(50,100,200 ?g/kg)on colonic transit of diabetic mice were measured by charcoal suspension pushing test.The effects of Atropine,N?-nitro-L-arginine methylester hydrochloride(L-NAME)and D-Lys3-GHRP-6(GHS-R antagonist)on the colonic transit of Ghrelin(200 ?g/kg)were also investigated.In vitro,the effects of Ghrelin on spontaneous contraction of proximal colonic circular muscle strips of diabetic mice were studied.Results:Ghrelin accelerated colonic transit of diabetic mice with significant dose-response relationship(P