Ghrelin in gastroenteric pathophysiology

DOCK4 regulates ghrelin production in gastric X/A-like cells

PURPOSE

Ghrelin, a gastric hormone, provides a hunger signal to the central nervous system to stimulate food intake. Ghrelin also modulates neuroinflammatory and apoptotic processes. Dedicator of cytokinesis 4 (DOCK4), a guanine nucleotide exchange factor (GEF), is involved in the regulation of neuronal polarization and axon regeneration. However, the effect of DOCK4 on ghrelin production has not been explored.

METHODS

The expression of DOCK4 in human and mouse stomach was examined by immunohistochemical staining. The synthesis and secretion of ghrelin in Dock4 null mice were evaluated by real-time quantitative PCR, Western blot and ELISA. The effects of DOCK4 on ghrelin production in mHypoE-42 cells were measured by real-time quantitative PCR and Western blot.

RESULTS

We showed that DOCK4 was expressed in both human and mouse gastric ghrelin cells. The mRNA and protein levels of gastric ghrelin, as well as ghrelin secretion, were remarkably diminished in Dock4 null mice. Furthermore, we showed that overexpression of Dock4 significantly stimulated ghrelin expression, while siRNA knockdown of endogenous Dock4 resulted in a marked decrease of ghrelin in mHypoE-N42 cells.

CONCLUSIONS

Our results identify DOCK4 as a critical regulator for ghrelin production in gastric X/A-like cells.

Traditional Japanese herbal medicine rikkunshito increases food intake and plasma acylated ghrelin levels in patients with esophageal cancer treated by cisplatin-based chemotherapy

Background

Cisplatin (CDDP) is an important chemotherapeutic drug for treating esophageal cancer that often induces nausea and vomiting. Rikkunshito (RKT), a traditional Japanese herbal medicine, can increase levels of plasma ghrelin, which is an orexigenic gut hormone that can alleviate chemotherapy-induced nausea and vomiting (CINV) and anorexia.

Methods

This prospective randomized crossover study included 20 patients with esophageal cancer who were administered with CDDP-based chemotherapy. Ten of them were assigned to group A [1st course: with RKT 7.5 g/day on days 1-14; 2nd course: without RKT (control)] and 10 were assigned to group B [1st course: without RKT (control); 2nd course: with RKT 7.5 g/day on days 22-35]. Food intake and levels of plasma acylated ghrelin (AG) were compared between the control and RKT courses.

Results

Data from 18 patients were included in this analysis, as chemotherapy was immediately stopped due to deteriorating renal function in one patient and intracerebral bleeding in another. The median rate at which food intake decreased between days 4 and 6 was considerably lower in the course with, than without RKT (2% vs. 30%; P=0.02). Median levels of AG significantly increased from days 3 to 8 in patients in both courses with and without RKT (9.6 to 15.7 fmol/mL, P<0.0001; control, 10.2 to 17.8, P=0.0002). The rate at which median plasma AG levels increased from days 3 to 8 tend to be higher in the RKT, than in the control course (68% vs. 48%, P=0.08).

Conclusions

RKT can improve CDDP-induced, delayed-onset anorexia and increase plasma AG levels among patients with esophageal cancer who undergo highly emetogenic chemotherapy (HEC).

Evaluation of mTOR signaling pathway proteins in rat gastric mucosa exposed to sulfite and ghrelin

BACKGROUND/AIMS

Mammalian target of rapamycin (mTOR) signaling serves as a central regulator of cell growth, proliferation, and survival. In this study, we planned to evaluate the expressions of mTOR signaling constituents (p-p70S6K, p-mTOR, and p-Tuberin) in rat gastric mucosa and to compare the results in sulfite- and sulfite+ghrelin-exposed groups.

MATERIALS AND METHODS

Rats were divided into three groups: the control group (C), the sodium metabisulfite (Na2S2O5) (S) group, and sulfite+ghrelin (SG) group. Sodium metabisulfite at 100 mg/kg/day was administered via gavage, and ghrelin at 20 μg/kg/day was administered intraperitoneally for 35 days. We have used immunohistochemistry for mTOR signaling pathway components.

RESULTS

There were no significant differences for p-p70S6K and p-mTOR expression among the C, S, and SG groups. Tuberin expression was significantly increased in the S group compared to the C group. Furthermore, tuberin expression was found to be significantly decreased in the SG group.

CONCLUSION

This study is the first one in the literature that shows the expression of mTOR signaling proteins in gastric mucosa of rats exposed to sulfite and ghrelin. Furthermore, it demonstrates that ghrelin treatment reduces p-Tuberin expression induced by ingested sulfite.

Changes in small intestinal motility and related hormones by acupuncture stimulation at Zusanli (ST 36) in mice

OBJECTIVES

To clarify the effects of acupuncture stimulation at Zusanli (ST 36) on the hormonal changes.

METHODS

Eight-week-old male C57BL/6 mice received acupuncture stimulation at acupoint ST 36 or Quchi (LI 11) once a day for 3 or 5 days in the acupuncture-stimulated groups, but not received in the normal group (n=6 in each group). On day 3 or 5, animals were given 0.1 mL of charcoal orally with a bulbed steel needle, 30 min after the last acupuncture stimulation. Ten minutes later, mice were anesthetized, and the intestinal transit and the concentrations of vasoactive intestinal peptide (VIP), motilin, ghrelin and gastrin in the serum were measured.

RESULTS

Compared to no acupuncture stimulation, acupuncture stimulation at ST 36 for 5 days increased the intestinal transit and down-regulated the concentration of VIP and up-regulated the concentrations of motilin, ghrelin and gastrin (P<0.05 or 0.01), whereas acupuncture stimulation at LI 11 did not change them signifificantly (P>0.05).

CONCLUSION

Acupuncture stimulation at ST 36 for 5 days enhances the small intestinal motility and regulates the secretion of hormones related to small intestinal motility.

Orexin system expression in the gastrointestinal tract of pigs

The aim of the present study was to characterize the expression of both proteins and gene transcripts for orexins (OXA and OXB) and their cognate receptors (OX1R and OX2R) in the different gastrointestinal sections of pigs. Using immunohistochemistry, OXA and OXB were found to be co-expressed in the same endocrine cells localized in the basal third of the glands of the body portion of the stomach. Using double immunostaining technique, these orexin-immunoreactive (IR) cells co-stored ghrelin and gastrin. Apparently, OX1R was also expressed within the same cells, forming the tubular gastric gland which displayed positive immunostaining for orexins and the other peptides. Neurons of the enteric nervous system of the stomach were not immunolabeled. We did not find any definite OXA- or OXB-IR cells as well as any immunosignal for orexin receptors in sections of the duodenum, ileum, cecum and rectum. PPOX, OX1R, OX2R mRNA were similarly expressed in all the gastrointestinal tracts. Gastrin and ghrelin showed the highest levels of expression in the gastric mucosa, but their abundance decreased along the subsequent tracts. Thus, in pigs, orexins do not play any role in the local control of intestinal motility and secretion but may rather be involved as endocrine modulators for the regulation of feeding and metabolic homeostasis. However, the co-localization of ghrelin and gastrin with both orexins in the same endocrine cells of the gastric glands suggests that these gut peptides may collaborate in the regulation of gastric secretion, energy homeostasis, body weight and food intake.

Rapid modulation of TRH and TRH-like peptide release in rat brain and peripheral tissues by ghrelin and 3-TRP-ghrelin

Ghrelin is not only a modulator of feeding and energy expenditure but also regulates reproductive functions, CNS development and mood. Obesity and major depression are growing public health concerns which may derive, in part, from dysregulation of ghrelin feedback at brain regions regulating feeding and mood. We and others have previously reported that thyrotropin-releasing hormone (TRH, pGlu-His-Pro-NH(2)) and TRH-like peptides (pGlu-X-Pro-NH(2), where "X" can be any amino acid residue) have neuroprotective, antidepressant, anti-epileptic, analeptic, anti-ataxic, and anorectic properties. For this reason male Sprague-Dawley rats were injected ip with 0.1mg/kg rat ghrelin or 0.9mg/kg 3-Trp-rat ghrelin. Twelve brain regions: cerebellum, medulla oblongata, anterior cingulate, posterior cingulate, frontal cortex, nucleus accumbens, hypothalamus, entorhinal cortex, hippocampus, striatum, amygdala, piriform cortex and 5 peripheral tissues (adrenals, testes, epididymis, pancreas and prostate) were analyzed. Rapid and profound decreases in TRH and TRH-like peptide levels (increased release) occurred throughout brain and peripheral tissues following ip ghrelin. Because ghrelin is rapidly deacylated in vivo we also studied 3-Trp-ghrelin which cannot be deacylated. Significant increases in TRH and TRH-like peptide levels following 3-Trp-ghrelin, relative to those after ghrelin were observed in all brain regions except posterior cingulate and all peripheral tissues except prostate and testis. The rapid stimulation of TRH and TRH-like peptide release by ghrelin in contrast with the inhibition of such release by 3-Trp-TRH is consistent with TRH and TRH-like peptides modulating the downstream effects of both ghrelin and unacylated ghrelin.

Interferon-γ inhibits ghrelin expression and secretion via a somatostatin-mediated mechanism

AIM: To investigate if and how the proinflammatory cytokine interferon γ (IFNγ) affects ghrelin expression in mice.

METHODS: The plasma concentration of ghrelin, and gastric ghrelin and somatostatin expression, were examined in wild-type mice and mice infected with Helicobacter pylori (H. pylori). Furthermore, ghrelin expression was examined in two achlorhydric mouse models with varying degrees of gastritis due to bacterial overgrowth. To study the effect of IFNγ alone, mice were given a subcutaneous infusion of IFNγ for 7 d. Finally, the influence of IFNγ and somatostatin on the ghrelin promoter was characterized.

RESULTS: H. pylori infection was associated with a 50% reduction in ghrelin expression and plasma concentration. Suppression of ghrelin expression was inversely correlated with gastric inflammation in achlorhdyric mouse models. Subcutaneous infusion of IFNγ suppressed fundic ghrelin mRNA expression and plasma ghrelin concentrations. Finally, we showed that the ghrelin promoter operates under the control of somatostatin but not under that of IFNγ.

CONCLUSION: Gastric infection and inflammation is associated with increased IFNγ expression and reduced ghrelin expression. IFNγ does not directly control ghrelin expression but inhibits it indirectly via somatostatin.

Ghrelin in chronic kidney disease

Patients with chronic kidney disease (CKD) often exhibit symptoms of anorexia and cachexia, which are associated with decreased quality of life and increased mortality. Chronic inflammation may be an important mechanism for the development of anorexia, cachexia, renal osteodystrophy, and increased cardiovascular risk in CKD. Ghrelin is a gastric hormone. The biological effects of ghrelin are mediated through the growth hormone secretagogue receptor (GHSR). The salutary effects of ghrelin on food intake and meal appreciation suggest that ghrelin could be an effective treatment for anorexic CKD patients. In addition to its appetite-stimulating effects, ghrelin has been shown to possess anti-inflammatory properties. The known metabolic effects of ghrelin and the potential implications in CKD will be discussed in this review. The strength, shortcomings, and unanswered questions related to ghrelin treatment in CKD will be addressed.

Gastric ghrelin in relation to gender, stomach topography and Helicobacter pylori in dyspeptic patients

AIM: To investigate the level of gastric ghrelin in stomach mucosa of dyspeptic patients in relation to Helicobacter pylori (H pylori) infection, bacterial cytotoxicity, topography and gender.

METHODS: The study comprised 40 premenopausal women (19 H pylori positive) and 48 men (17 H pylori positive) with functional dyspepsia. All gastric biopsy specimens revealed normal mucosa or non-atrophic gastritis. Gastric ghrelin concentration was determined by Enzyme linked immunosorbent assay. The cagA and vacA strains of bacterial DNA were identified by multiplex polymerase chain reaction.

RESULTS: In general, infection with H pylori caused an increase in gastric ghrelin level regardless of gender and stomach topography. Significantly more hormone was present in both, non-infected and H pylori positive female samples, as compared to males. The distribution of bacterial strains showed cagA(+) vacA s1m1 and cagA(-) vacA s2m2 genotypes as the most common infections in the studied population. A tendency to higher ghrelin levels was observed in less cytotoxic (cagA negative) strain-containing specimens from the antrum and corpus of both gender groups (without statistical significance).

CONCLUSION: An increase in gastric ghrelin levels at the stage of non-atrophic gastritis in H pylori positive patients, especially in those infected with cagA(-) strains, can exert a gastroprotective effect.

Abnormalities in glucose metabolism in patients with schizophrenia treated with atypical antipsychotic medications

The incidence of carbohydrate intolerance and overt diabetes is increased in patients with schizophrenia treated with the newer atypical antipsychotic agents. The precise mechanism for these abnormalities remains obscure. This review examines the potential interaction between atypical antipsychotic medications and several hormones known to influence appetite regulation and carbohydrate metabolism.

Gastric sensorimotor functions and hormone profile in normal weight, overweight, and obese people

BACKGROUND & AIMS

Peptide YY (PYY) levels are reported to be decreased in obesity. The relation between gastric functions, satiation, and gut hormones in obesity is incompletely understood. The aim of this study was to compare gastric volumes, emptying, maximum tolerated volumes, postchallenge symptoms, and selected gut hormones in normal, overweight, or obese healthy volunteers.

METHODS

In 73 nonbulimic normal, overweight, or obese participants weighing less than 137 kg, we measured gastric emptying of solids and liquids by scintigraphy (gastric emptying half-time [GE t(1/2)]); gastric volumes by single-photon emission computed tomography; maximum tolerated volumes and symptoms by satiation test; and plasma leptin, ghrelin, insulin, glucagon-like peptide 1, and PYY levels. Groups were compared using 1-way analysis of covariance adjusted for sex. Univariate associations among measured responses were assessed using Spearman correlations. Multiple linear regression models, adjusting for weight and sex, assessed the independent ability of gastric functions and hormones to predict satiation volume.

RESULTS

Obese and overweight subjects had significantly lower postprandial gastric volumes, higher fasting and postprandial insulin and leptin levels, and lower fasting ghrelin and lower postprandial reduction in ghrelin levels. PYY levels were not different in obese or overweight subjects compared with controls. The GE t(1/2) was correlated inversely with postprandial PYY; increased body weight was associated with faster GE t(1/2) of solids (r(s) = 0.33, P = .005) and liquids (r(s) = 0.24, P = .04). Postprandial changes in gastric volume and PYY were independent predictors of satiation (both P = .01).

CONCLUSIONS

Overweight or obesity are associated with lower postprandial gastric volumes and normal PYY levels. Gastric emptying influences postprandial PYY levels. Postprandial PYY and gastric volume independently predict satiation volume in nonbulimic people across a wide body mass index range.

Expression of Ghrelin in nervous system and its cytoprotective action in rats

AIM: To investigate the expression of Ghrelin in brain, intestinal myenteric plexus and plasma and study its possible cytoprotective effect and mechanism on gastric mucosa against stress-induced ulcers.

METHODS: Seventy-six healthy male Wistar rats were divided into 6 groups randomly: cold-water restraint group (n = 10); intracerebroventricular (icv) injection of Ghrelin group (n = 24); icv injection of Ghrelin after subcutaneous injection of Nω-Nitro-L-arginine methylester (L-NAME) group (n = 8) and three matched control groups. The expression of Ghrelin in rat brain, intestinal myenteric plexus and plasma were detected by radio-immunoassay (RIA) and double staining of immunofluorescence and immunohistochemistry. The effect and mechanism of Ghrelin on gastric mucosa against stress-induced ulcer were analyzed using neurophysiologic methods.

RESULTS: Ghrelin-positive immunoreaction (IR) was observed in the small intestinal myenteric plexus and primarily cultured myenteric plexus neurons. Ghrelin-IR co-localized with choline acetyl transferase (ChAT), but not with nitric oxide synthase (NOS) or Calbindin (Calb) in the same myenteric plexus neurons. In comparison with that in its matched control group, the content of Ghrelin-IR in plasma was significantly decreased (198.3 ± 29.6 ng/L vs 141.7 ± 26.5 ng/L, P < 0.05), but increased in hypothalamus, medulla oblongata, pituitary and intestinal myenteric plexus (96.2 ± 18.1 pg/mg vs 153.2 ± 11.6 pg/mg, P = 0.006; 89.8 ± 16.5 pg/mg vs 144.4 ± 13.9 pg/mg, P = 0.007; 108.3 ± 11.9 pg/mg vs 198.2 ± 23.3 pg/mg, P = 0.002; 48.8 ± 12.8 pg/mg vs 86.2 ± 21.5 pg/mg, P = 0.02; respectively). The formation of stress ulcers was markedly inhibited by microinjection of Ghrelin into the ventricle with a dose-dependent manner (ulcer index: normal saline 86.7 ± 6.2; 50 ng Ghrelin 79.3 ± 10.7, P = 2.18; 500 ng Ghrelin: 61.3 ± 11.7, P = 0.04; 5 000 ng Ghrelin: 35.6 ± 10.8, P = 0.005). However, after a subcutaneous injection of L-NAME, the cytoprotective effect of Ghrelin disappeared.

CONCLUSION: Ghrelin co-localizes with ChAT in intestinal myenteric plexus neurons. The expression of Ghrelin changes in the central nerves system (CNS) and plasma while stress ulcer happens. Ghrelin in the CNS can protect gastric mucosa with a dose-dependent manner, which is probably related to the synthesis of nitric oxide.

Ghrelin-induced gastroprotection against ischemia-reperfusion injury involves an activation of sensory afferent nerves and hyperemia mediated by nitric oxide

Ghrelin has been recently identified as an endogenous ligand for growth hormone secretagogue receptor that regulates growth hormone secretion, increases appetite and contributes to energy homeostasis. Although this peptide is predominantly produced by the fasted stomach, little is known about its influence on the gastric mucosal integrity. The aim of the present study was (1) to investigate the effect of acylated ghrelin on the formation and healing of acute gastric mucosal lesions induced by ischemia-reperfusion and gastric mucosal blood flow in rats; (2) to analyse the effects of the deactivation of afferent sensory nerves with capsaicin and of the inhibition of nitric oxide (NO)-synthase by NG-nitro-l-arginine (l-NNA) on the ghrelin-induced protection; (3) to examine the influence of ghrelin on nuclear factor-kappa B (NF-kappaB) activation and on release of proinflammatory cytokines, such as tumor necrosis factor-alpha, (4) to assess the effect of ghrelin on the mRNA expression of constitutive nitric oxide synthase (cNOS), calcitonin gene related peptide (CGRP) and angiogenesis related proteins such as hypoxia inducible factor-1 alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF), and (5) to determine the effect of ischemia/reperfusion on the gastric mucosa expression of ghrelin in rats without and with administration of exogenous hormone. Wistar rats were exposed to 30 min of ischemia followed by 3 h of reperfusion. Ghrelin was administered in dose of 5, 10 or 20 mug/kg intraperitoneally (i.p.) 30 min prior exposure to ischemia/reperfusion and at 3 h after the end of ischemia, the mean lesion area was measured by planimetry and the changes in gastric blood flow were determined by hydrogen (H2)-gas clearance method. The healing of ischemia/reperfusion induced lesions was evaluated at 24 h or 6 days after the end of standard ischemia/reperfusion. The expression of cNOS, CGRP, HIF-1alpha, VEGF and ghrelin was evaluated by reverse transcription polymerase chain reaction or Western blot. Ghrelin significantly attenuated the ischemia/reperfusion-induced gastric lesions and accelerated the healing of these lesions while significantly raising the gastric blood flow. Deactivation of sensory nerves with capsaicin or inhibition of cNOS by L-NNA significantly attenuated the protective activity of ghrelin and accompanying increase in the GBF. Exogenous ghrelin significantly inhibited the activation of NF-kappaB and plasma TNF-alpha levels. The ghrelin-enhanced acceleration of healing of ischemia/perfusion induced lesions was accompanied by enhanced expression of mRNA for HIF-1alpha and by diminution of the ischemia/reperfusion induced increase in mRNA expression for TNF-alpha. We conclude that ghrelin exerts a potent protective action on the gastric mucosa and accelerates the healing of ischemia/reperfusion-induced lesions and these effects depend upon activation of sensory nerves, hyperemia mediated by NO, increased angiogenesis due to expression of YEGF and anti-inflammatory properties of this peptide.