Distribution of ghrelin-immunoreactive cells in human gastric mucosa: comparison with that of parietal cells

Protein Catabolism and the Dysregulation of Energy Intake-Related Hormones May Play a Major Role in the Worsening of Malnutrition in Hospitalized Cirrhotic Patients

Malnutrition in cirrhotic patients is extremely common and has a multifactorial aetiology, whose constitutive elements have not been completely elucidated yet. Protein depletion is particularly important and an imbalance of hormones regulating hunger and satiety may be an important additive factor. The diagnosis and treatment of malnutrition are extremely important since malnutrition is associated with higher complication rates and mortality. Our observational study aimed to study protein status and energy intake-related hormone levels in a cohort of hospitalized cirrhotic patients. We enrolled 50 hospitalized and clinically stable cirrhotic patients and assessed their nutritional status with anthropometric measurements and nitrogen balance. In a subgroup of 16 patients and 10 healthy controls, circulating ghrelin and leptin levels were studied. We observed that 60% of our patients were malnourished on the basis of the mid-arm muscle circumference values; the recorded daily protein intake was tendentially insufficient (mean protein intake of 0.7 ± 0.5 g protein/kg vs. recommended intake of 1.2–1.5 g of protein/kg/die). Cirrhotic patients had lower circulating levels of both ghrelin and leptin compared to healthy controls. In conclusion, hospitalized cirrhotic patients face a catabolic state and an imbalance in hormones regulating food intake and satiety, and these elements may play a major role in the genesis and/or the worsening of malnutrition.

Photodynamic Methylene Blue-Embedded Intragastric Satiety-Inducing Device to Treat Obesity

Bariatric surgery is the most effective treatment for weight recidivism, and endoscopic bariatric treatment has been developed for a similar effect without anatomical modification. An intragastric satiety-inducing device (ISD) is a minimally invasive approach to induce satiety by continuously pressing the stomach and stimulating ghrelin-producing cells. To enhance the therapeutic effects of ISD, photodynamic therapy (PDT) can be combined by generating singlet oxygen under laser irradiation. Methylene blue (MB), as a photosensitizer (PS), was coated on the ISD surface for singlet oxygen production to stimulate or destroy cells. Ghrelin-producing cells effectively inhibited ghrelin secretion and induced gastrointestinal satiety signals compared with the MB-uncoated device via PDT. Herein, MB-embedded ISDs were developed, and their photoresponsive abilities were demonstrated in the device itself and in vitro. PDT with an MB-embedded ISD was successfully performed in a porcine model, which had 2-fold reduced body weight gain (12% in PDT vs 24% in control) and 2-fold reduced ghrelin levels (21.2 pg/mL in PDT vs 45.1 pg/mL in control) at the first week postprocedure. The simple and unique operation extends the point of view in PDT and is expected to be a novel endoscopic bariatric therapy.

Intestinal Metaplasia Influencing the Density of Ghrelin Expressing Cells in Morbid Obese Patients

PURPOSE

The aim was to compare the density of ghrelin-expressing cells (GECs) in morbid obese patients with or without intestinal metaplasia (IM).

MATERIALS AND METHODS

The study included 48 patients out of 244 who underwent laparoscopic sleeve gastrectomy between 2015 and 2019. IM was detected in the sleeve gastrectomy specimens of 24 of these 244 patients. The study group consisted of all of the patients with IM. It was a case matched study. Matching factors were age and gender. Ghrelin was stained with a Leica semiautomatic immunohistochemical-staining machine. Stained preparations with ghrelin were subjected to light microscopic examination.

RESULTS

The number of GECs in cases with IM was significantly lower than the cases without IM (p = 0.001). The number of GECs was significantly higher in cases with chronic inactive superficial gastritis than cases with chronic active superficial gastritis (p = 0.033).

CONCLUSION

We found that there was a decrease in the number of GECs in the corpus and fundus of the stomach in cases with gastric IM as a contribution to the literature. IM cause a decrease in the number of GECs in the gastric oxyntic glands. In addition, chronic active superficial gastritis is also associated with a decrease in the number of GECs. We can say that the common feature of all of these factors may be gastric mucosal damage. Consequently, damage to the gastric mucosa appears to reduce the number of GECs.

Intragastric satiety-inducing device reduces food intake and suppresses body weight gain in a rodent model

BACKGROUND

An intragastric satiety-inducing device (ISD) (Full Sense Device; Baker, Foote, Kemmeter, Walburn, LLC, Grand Rapids, MI) is a novel weight-loss device, which may induce satiety by applying continuous pressure on the gastric cardia. This study investigated the effect of the ISD on food intake and body weight gain in a rodent model.

METHODS

Thirty-two male Sprague-Dawley rats (weight, 250-300 g) were randomly divided into four groups of eight individuals. Single-disk (SD) and double-disk (DD) group animals underwent peroral placement of a single- or double-disk ISD, respectively, under fluoroscopic guidance. The ISD comprised a 4 mm × 1.5 cm nitinol stent placed in the lower esophagus and one (single-disk) or two (double-disk) 2.5-cm-diameter star-shaped nitinol disks placed in the gastric fundus. Esophageal stent (ES) and sham-operated (SO) group animals underwent peroral placement of the ES part of the ISD and a sham operation, respectively.

RESULTS

Food intake was significantly different among the four groups over the 4-week study period (P < 0.001); food intake was significantly lower in the SD and DD groups than in the SO group (P = 0.016 and P = 0.002, respectively) but was not significantly different between the SD and DD groups (P > 0.999) and between the ES and SO groups (P = 0.677). Body weight was significantly different among the four groups by the end of the study period (P < 0.001); body weight was significantly lower in the DD group than in the SD, ES, and SO groups (P = 0.010, P < 0.001, and P < 0.001, respectively) and in the SD group than in the SO group (P = 0.001), but it was not significantly different between the ES and SO groups (P = 0.344).

CONCLUSION

ISD reduced food intake and suppressed body weight gain in a rodent model.

Early detection of gastric cancer beyond endoscopy - new methods

Early detection of gastric cancer is remaining a challenge. This review summarizes current knowledge on non-invasive methods that could be used for the purpose. The role of traditional cancer markers such as CEA, CA 72-4, CA 19-9, CA 15-3, and CA 12-5 lies mainly in therapy monitoring than early detection. Most extensive studied biomarkers (pepsinogens, ABC method) are aiming at the detection of precancerous lesions with modest sensitivity for cancer. Tests based on the detection of cancer-specific methylation patterns (PanSeer), circulating proteins and mutations in circulating tumour DNA (CancerSEEK), as well as miRNA panels have demonstrated promising results bringing those closer to practice. More extensive research is required before tests based on the detection of circulating tumour cells, extracellular vesicles and cell-free RNA could reach the practice. Detection of volatile organic compounds in the human breath is a promising development; sensor technologies for this purpose could be very attractive in screening settings.

Weight loss with or without intragastric balloon causes divergent effects on ghrelin cell expression

Objective

The mechanism of action of intragastric balloons in the treatment of obesity is not fully understood. One of the hypotheses is that balloons might have an effect on the fundus, the area of ghrelin production.

Methods

Participants were randomized to a 13‐week period of sham or balloon treatment followed by a 13‐week period of balloon therapy in everyone. Blood samples for ghrelin levels were taken in the fasting state and after a breakfast at the start, after 13 and 26 weeks. Biopsies for ghrelin cell immunohistochemistry were taken from the fundus at endoscopy.

Results

Seven participants entered the balloon–balloon (BB) group and 11 the sham–balloon (SB) group. Despite a considerable weight loss, a median −17.9 kg (interquartile ranges −23.8 to −0.5) in the BB group and −18.3 kg (−22.7 to −14.7) in the SB group, fasting ghrelin and meal‐induced ghrelin response did not change. In the SB group, the number of ghrelin cells increased significantly (p 0.001) from 110.6 (83.6–118.9) to 160.2 (128.5–223.0) while on sham treatment and returned to initial levels, 116.3 (91.7–146.9) (p 0.001), when they received their first balloon. No significant changes in ghrelin cell numbers were observed in the BB group.

Conclusion

In participants without a balloon, weight loss induced an increase in ghrelin cell numbers in the fundus, which was annulled by the subsequent placement of a balloon. The effect of a balloon might be explained by effects on ghrelin cell numbers or ghrelin cell activity.

Fructose-induced metabolic disturbances in rats and its impact on stomach endocrine cell number and smooth muscle contractility

Context: Gastric ghrelin-positive endocrine cells (GHR + EC) were most dense in the oxyntic mucosa.Objective: We evaluated ECs and contractile activity in rat stomach with metabolic disorders.Materials and methods: Male Wistar rats were divided into two groups: Control (n = 9) received tap water and Fructose (n = 9) drank 15% fructose solution for 12 weeks. Streptozotocin was applied in a dose of 20 mg/kg b.w. two weeks after the beginning of the experiment on Fructose group. Smooth-muscle strips from the stomach were influenced by Angiotensin II for analysis of parameters of contractions. Stomach samples were elaborated with immunohistochemistry for ghrelin, somatostatin, gastrin antibodies and with double immunofluorescence.Results: In treated animals, GHR + EC were significantly increased in the corpus where somatostatin-positive cells were decreased. Contractile activity was decreased.Conclusions: The increase number of GHR + EC was discussed in the context of Somatostatin and Gastrin-positive ECs variations and correlated with the decrease of smooth muscle contraction.

Bariatric Arterial Embolization with Calibrated Radiopaque Microspheres and an Antireflux Catheter Suppresses Weight Gain and Appetite-Stimulating Hormones in Swine

PURPOSE

To examine safety and efficacy of bariatric arterial embolization (BAE) with x-ray-visible embolic microspheres (XEMs) and an antireflux catheter in swine.

MATERIAL AND METHODS

BAE with selective infusion of XEMs (n = 6) or saline (n = 4, control) into gastric fundal arteries was performed under x-ray guidance. Weight and plasma hormone levels were measured at baseline and weekly for 4 weeks after embolization. Cone-beam CT images were acquired immediately after embolization and weekly for 4 weeks. Hormone-expressing cells in the stomach were assessed by immunohistochemical staining.

RESULTS

BAE pigs lost weight 1 week after embolization followed by significantly impaired weight gain relative to control animals (14.3% vs 20.9% at 4 weeks, P = .03). Plasma ghrelin levels were significantly lower in BAE pigs than in control animals (1,221.6 pg/mL vs 1,706.2 pg/mL at 4 weeks, P < .01). XEMs were visible on x-ray and cone-beam CT during embolization, and radiopacity persisted over 4 weeks (165.5 HU at week 1 vs 158.5 HU at week 4, P = .9). Superficial mucosal ulcerations were noted in 1 of 6 BAE animals. Ghrelin-expressing cell counts were significantly lower in the gastric fundus (17.7 vs 36.8, P < .00001) and antrum (24.2 vs 46.3, P < .0001) of BAE pigs compared with control animals. Gastrin-expressing cell counts were markedly reduced in BAE pigs relative to control animals (98.5 vs 127.0, P < .02). Trichrome staining demonstrated significantly more fibrosis in BAE animals compared with control animals (13.8% vs 8.7%, P < .0001).

CONCLUSIONS

XEMs enabled direct visualization of embolic material during and after embolization. BAE with XEMs and antireflux microcatheters was safe and effective.

The Effects of Low-Dose and High-Dose Decoctions of Fructus aurantii in a Rat Model of Functional Dyspepsia

BACKGROUND Fructus aurantii is a flavonoid derived from Citrus aurantium (bitter orange) that is used in traditional Chinese medicine (TCM) to treat gastric motility disorders. This study aimed to investigate the effects of low-dose and high-dose decoctions of Fructus aurantii in a rat model of functional dyspepsia (FD). MATERIAL AND METHODS Sprague-Dawley rats (n=90) were divided into nine study groups: the control group, the FD model group, the domperidone-treated (Domp) group, the low-dose raw Fructus aurantii (FA-L) group, the high-dose raw Fructus aurantii (FA-H) group, the low-dose Fructus aurantii with stir-fried wheat bran (Bran-L) group, the high-dose Fructus aurantii with stir-fried wheat bran (Bran-H) group, the low-dose Fructus aurantii with stir-fried wheat bran and honey (Honey-L) group, and the high-dose Fructus aurantii with stir-fried wheat bran and honey (Honey-H) group. The FD rat model was established by semi-starvation, followed by tail damping, stimulation, and forced exercise with fatigue. Change in weight, rate of gastric emptying and intestinal propulsion, and serum levels of leptin, motilin, vasoactive intestinal peptide (VIP), gastrin, calcitonin gene-related peptide (CGRP), ghrelin, and cholecystokinin were compared between the groups. RESULTS In the FD model group, weight, rate of gastric emptying and intestinal propulsion significantly decreased, the expression of leptin, VIP and CGRP increased, and expression of motilin, gastrin, ghrelin, and cholecystokinin significantly decreased. Treatment with low-dose Fructus aurantii with stir-fried wheat bran significantly reversed these effects. CONCLUSIONS In the rat model of FD, low-dose Fructus aurantii with stir-fried wheat bran increased gastrointestinal motility and gastrointestinal hormone levels.

Distributions and relationships of chemically defined enteroendocrine cells in the rat gastric mucosa

This paper provides quantitative data on the distributions of enteroendocrine cells (EEC), defined by the hormones they contain, patterns of colocalisation between hormones and EEC relations to nerve fibres in the rat gastric mucosa. The rat stomach has three mucosal types: non-glandular stratified squamous epithelium of the fundus and esophageal groove, a region of oxyntic glands in the corpus, and pyloric glands of the antrum and pylorus. Ghrelin and histamine were both contained in closed cells, not contacting the lumen, and were most numerous in the corpus. Gastrin cells were confined to the antrum, and 5-hydroxytryptamine (5-HT) and somatostatin cells were more frequent in the antrum than the corpus. Most somatostatin cells had basal processes that in the antrum commonly contacted gastrin cells. Peptide YY (PYY) cells were rare and mainly in the antrum. The only numerous colocalisations were 5-HT and histamine, PYY and gastrin and gastrin and histamine in the antrum, but each of these populations was small. Peptide-containing nerve fibres were found in the mucosa. One of the most common types was vasoactive intestinal peptide (VIP) fibres. High-resolution analysis showed that ghrelin cells were closely and selectively approached by VIP fibres. In contrast, gastrin cells were not selectively innervated by VIP or CGRP fibres. The study indicates that there are distinct populations of gastric EEC and selective innervation of ghrelin cells. It also shows that, in contrast to EEC of the small intestine, the majority of EEC within the stomach contained only a single hormone.

Bariatric Arterial Embolization: Effect of Microsphere Size on the Suppression of Fundal Ghrelin Expression and Weight Change in a Swine Model

Purpose To determine whether microsphere size effects ghrelin expression and weight gain after selective bariatric arterial embolization (BAE) in swine. Materials and Methods BAE was performed in 10 swine by using smaller (100-300 μm; n = 5) or larger (300-500 μm; n = 5) calibrated microspheres into gastric arteries. Nine control pigs underwent a sham procedure. Weight and fasting plasma ghrelin levels were measured at baseline and weekly for 16 weeks. Ghrelin-expressing cells (GECs) in the stomach were assessed by using immunohistochemical staining and analyzed by using the Wilcoxon rank-sum test. Results In pigs treated with smaller microspheres, mean weight gain at 16 weeks (106.9% ± 15.0) was less than in control pigs (131.9% ± 11.6) (P < .001). Mean GEC density was lower in the gastric fundus (14.8 ± 6.3 vs 25.0 ± 6.9, P < .001) and body (27.5 ± 12.3 vs 37.9 ± 11.8, P = .004) but was not significantly different in the gastric antrum (28.2 ± 16.3 vs 24.3 ± 11.6, P = .84) and duodenum (9.2 ± 3.8 vs 8.7 ± 2.9, P = .66) versus in control pigs. BAE with larger microspheres failed to suppress weight gain or GECs in any stomach part compared with results in control swine. Plasma ghrelin levels were similar between BAE pigs and control pigs, regardless of microsphere size. Week 1 endoscopic evaluation for gastric ulcers revealed none in control pigs, five ulcers in five pigs embolized by using smaller microspheres, and three ulcers in five pigs embolized by using larger microspheres. Conclusion In bariatric arterial embolization, smaller microspheres rather than larger microspheres showed greater weight gain suppression and fundal ghrelin expression with more gastric ulceration in a swine model. © RSNA, 2018.

Structural determination, distribution, and physiological actions of ghrelin in the guinea pig

We identified guinea pig ghrelin (gp-ghrelin), and examined its distribution and physiological actions in the guinea-pig. Gp-ghrelin is a 28-amino acid peptide (GASFR SPEHH SAQQR KESRK LPAKI QPR); seven amino acids are different from that of rat ghrelin at positions 2, 5, 10, 11, 19, 21, and 25, which include the conserved region known in mammals. The third serine residue is mainly modified by n-decanoyl acid. Both gp-ghrelin and rat ghrelin increased intracellular Ca²⁺ concentration of HEK293 cells expressing guinea pig growth hormone secretagogue receptor 1a (GHS-R1a), and the affinity of gp-ghrelin was slightly higher than that of rat ghrelin. In addition, gp-ghrelin was also effective in CHO cells expressing rat GHS-R1a with similar affinity to that of rat ghrelin. Gp-ghrelin mRNA was predominantly expressed in the stomach, whereas the expression levels in other organs was low. High levels of GHS-R1a mRNA expression were observed in the pituitary, medulla oblongata, and kidney, while medium levels were noted in the thalamus, pons, olfactory bulb, and heart. Immunohistochemistry identified gp-ghrelin-immunopositive cells in the gastric mucosa and pancreas. Intraperitoneal injection of gp-ghrelin increased food intake in the guinea pig. Gp-ghrelin did not cause any mechanical responses in isolated gastrointestinal smooth muscles in vitro, similar to rat ghrelin. In conclusion, the N-terminal structures that are conserved in mammals were different in gp-ghrelin. Moreover, the functional characteristics of gp-ghrelin, other than its distribution, were dissimilar from those in other Rodentia.

Serum ghrelin; a new surrogate marker of gastric mucosal alterations in upper gastrointestinal carcinogenesis

Background

A few studies have indicated inverse relationships between serum ghrelin and gastric and esophageal cancers but those associations have been restricted to specific populations, including smokers and overweight individuals. We examined the association between ghrelin and gastroesophageal cancers and atrophic gastritis in a population-based setting.

Methods

In total 220 gastroesophageal cancers, comprising non-cardia and cardia gastric cancer, esophageal adenocarcinoma, esophageal squamous cell carcinoma (SCC) and age and gender-matched controls were recruited. Serum ghrelin, pepsinogen I/II ratio (PGI/II) and anti-H.pylori IgG antibodies were measured. Relationships between ghrelin and gastroesophageal cancers, after adjustment for PGI/II ratio, H.pylori status and smoking, were tested using logistic regression. Furthermore, in 125 endoscopically normal volunteers, with and without histological atrophic gastritis, the relationship with ghrelin was compared.

Results

Serum ghrelin (lowest vs. highest quintile) was inversely associated with gastric cancer: OR (95% CI) 8.71 (1.70–44.59) for cardia and 6.58 (1.26–34.46) for non-cardia cancer. Lower serum ghrelin was also associated with esophageal SCC: OR (95% CI) 5.69 (1.36–23.78), but not with esophageal adenocarcinoma. A similar association was observed between gastric cancer (cardia and non-cardia) and esophageal SCC when serum ghrelin was analysed as a continuous scaled variable. In endoscopically-normal volunteers, extensive atrophic gastritis was associated with low serum ghrelin [OR (95% CI) 0.25 (0.10–0.64)].

Conclusion

Inverse associations between ghrelin and some gastroesophageal cancers suggest a potential role for serum ghrelin as a biomarker of upper gastrointestinal cancers and atrophic gastritis. In areas with a high incidence of gastric and/or esophageal cancer, screening might be more effectively targeted to individuals with low serum ghrelin in addition to the PGI/II ratio.

Mapping of ghrelin gene expression and cell distribution in the stomach of morbidly obese patients--a possible guide for efficient sleeve gastrectomy construction

BACKGROUND

Ghrelin is secreted mainly in the stomach and plays a role in food intake regulation. Morbidly obese (MO) individuals report a decline in appetite after sleeve gastrectomy (SG), presumably due, in part, to ghrelin cell removal. Ghrelin cell distribution and expression were determined in three areas of resected stomach specimens from MO patients subjected to SG.

METHODS

Resected stomach specimens from 20 MO patients undergoing SG were analyzed. Real-time polymerase chain reaction of ghrelin mRNA and immunohistostaining for ghrelin cells in three stomach regions (fundus, body, and pre-antral areas) were performed. Body mass index (BMI) and total plasma ghrelin levels were obtained before and 3 months postoperatively.

RESULTS

Ghrelin mRNA was detected throughout the stomach, its expression decreasing from the fundus towards the antrum. The relative quantification for ghrelin mRNA expression was 0.043, 0.026, and 0.015 at the fundus, body, and pre-antral region, respectively (P = 0.05, fundus vs. pre-antral region). Average ghrelin cell counts declined from 60 ± 40 to 45 ± 20 and 39 ± 13 cells/high power fields in the fundus, body, and pre-antral region, respectively. Three months after surgery, total plasma ghrelin levels decreased from 1,676 ± 470 to 1,179 ± 188 pg/ml (P < 0.00001) and BMI dropped from 46 ± 6 to 38 ± 5 kg/m2 (P < 0.00001).

CONCLUSIONS

Distribution and expression of ghrelin-secreting cells throughout the stomach were defined, emphasizing the importance of meticulous resection of the fundus during SG for maximal ghrelin cell removal.

Mapping analysis of ghrelin producing cells in the human stomach associated with chronic gastritis and early cancers

OBJECTIVE

The majority of ghrelin producing cells (GPC) are present in the fundic gland of the stomach and recognized as X/A like cells. The detailed distribution of GPC in the stomach is still unknown in healthy and pathological subjects.

METHODS

We investigated the detailed distribution of GPC in the stomach, especially in relation with chronic gastritis, using surgical specimens from 12 patients with early gastric cancer. Either the anterior or posterior half of the whole stomach, which was a counterpart of the tumor bearing side, was subjected for immunohistochemistry of ghrelin, and the number of total GPC were semi quantitatively evaluated as GPC score. GPC score was compared with the degree of chronic gastritis, serum ghrelin concentration and body weight.

RESULTS

GPC was not observed in the pyloric gland, but heterogeneously distributed in the fundic gland mainly in upper body and the greater curvature. The GPC score showed about nine-fold difference, which correlated well with the degree of chronic gastritis by Sydney score (r = -0.84, P < 0.001). The serum ghrelin concentration was basically determined by the GPC score (r = 0.75, P = 0.0047); however, the obese patients showed low serum ghrelin concentration in spite of the presence of abundant GPCs. In the low GPC score patients, serum ghrelin was constantly low regardless of their body weight.

CONCLUSIONS

GPC was inversely correlated with progression of chronic gastritis. Its quantification using immunohistochemistry of the whole stomach was useful to comprehensively evaluate ghrelin profile.

Distribution of ghrelin-producing cells in the gastrointestinal tract of pigs at different ages

Ghrelin is involved in many biological processes, ranging from appetite regulation and the release of growth hormone to the regulation of gastrointestinal motility and secretion processes. Ghrelin expression is not homogenously distributed throughout the gastrointestinal tract; expression is species-specific and can also depend on the animal age. This study was performed to investigate ghrelin immunolocalization in the gastrointestinal tract of pigs at different ages: 1 day (birth), 28 days (weaning), 2 months, 4 months, and 7 months (pre-puberty). Tissue samples were collected along the entire gastrointestinal tract and were examined by immunohistochemistry and double-immunofluorescence. Histometry was performed by counting the number of endocrine ghrelin immunopositive cells in the gastrointestinal mucosa. Ghrelin was found to be present along the swine alimentary canal from the stomach to the caecum. In all regions of the alimentary canal of the animals studied, ghrelin-immunoreactive (IR) cells co-localized with chromogranin-A and were therefore identified as endocrine cells. In the gastric fundus, ghrelin-immunoreactivity was partially detected in co-localization with H-K-adenosine triphosphatase and pepsinogen. Ghrelin-IR endocrine cells were abundant in the oxyntic mucosa but less present in the small intestine and rare in the large intestine. The cell density of the ghrelin-IR endocrine cells was lowest in the oxyntic mucosa of 1-day-old pigs. We can conclude that gastric ghrelin expression is not related merely to age but could also potentially be influenced by food intake.

Altered expression of gustatory-signaling elements in gastric tissue of morbidly obese patients

Objective:

Sensing of nutrients in the stomach is of crucial importance for the regulation of ingestive behavior especially in the context of metabolic dysfunctions such as obesity. Cells in the gastric mucosa with taste-signaling elements are considered as candidates for sensing the composition of ingested food and consequently modulate gastrointestinal processes. To assess whether obesity might have an impact on gastric chemosensory cells, gastric tissue samples from morbidly obese patients and normal-weight subjects were compared using a reverse transcriptase (RT)-PCR, qPCR and immunohistochemical approach.

Results:

Analysis of biopsy tissue samples from human stomach revealed that transcripts for the taste-signaling elements, including the receptor T1R3 involved in the reception of amino acids and carbohydrates, the fatty acid receptor GPR120, the G protein gustducin, the effector enzyme PLCβ2 and the ion channel TRPM5 are present in the human gastric mucosa and led to the visualization of candidate chemosensory cells in the stomach expressing gustatory marker molecules. RT-PCR and qPCR analyses indicated striking differences in the expression profiles of specimens from obese subjects compared with controls. For GPR120, gustducin, PLCβ2 and TRPM5 the expression levels were increased, whereas for T1R3 the level decreased. Using TRPM5 as an example, we found that the higher expression level was associated with a higher number of TRPM5 cells in gastric tissue samples from obese patients. This remarkable change was accompanied by an increased number of ghrelin-positive cells.

Conclusions:

Our findings argue for a relationship between the amount of food intake and/or the energy status and the number of candidate chemosensory cells in the gastric mucosa.

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 gastrointestinal disease

Enteroendocrine cells of the gastric fundus are the predominant source of ghrelin production, although ghrelin gene transcripts and ghrelin-producing cells have been identified throughout the gastrointestinal tract. Various infectious, inflammatory and malignant disorders of the gastrointestinal system have been shown to alter ghrelin production and secretion and consequently to affect endocrine ghrelin levels and activity. Animal studies have demonstrated that ghrelin and synthetic ghrelin mimetics can reduce the severity of gastric and colonic inflammation and human clinical trials are underway to determine the efficacy of ghrelin in improving motility disorders. This review summarises the impact of gastrointestinal disease on ghrelin synthesis and secretion and the potential use of ghrelin and its mimetics for the treatment of these diseases.

Helicobacter pylori infection and circulating ghrelin levels - a systematic review

BACKGROUND

The nature of the association between ghrelin, an orexigenic hormone produced mainly in the stomach, and Helicobacter pylori (H pylori), a bacterium that colonises the stomach, is still controversial. We examined available evidence to determine whether an association exists between the two; and if one exists, in what direction.

METHODS

We reviewed original English language studies on humans reporting circulating ghrelin levels in H pylori infected and un-infected participants; and circulating ghrelin levels before and after H pylori eradication. Meta-analyses were conducted for eligible studies by combining study specific estimates using the inverse variance method with weighted average for continuous outcomes in a random effects model.

RESULTS

Seventeen out of 27 papers that reported ghrelin levels in H pylori positive and negative subjects found lower circulating ghrelin levels in H pylori positive subjects; while 10 found no difference. A meta-analysis of 19 studies with a total of 1801 participants showed a significantly higher circulating ghrelin concentration in H pylori negative participants than in H pylori positive participants (Effect estimate (95%CI) = -0.48 (-0.60, -0.36)). However, eradicating H pylori did not have any significant effect on circulating ghrelin levels (Effect estimate (95% CI) = 0.08 (-0.33, 0.16); Test for overall effect: Z = 0.67 (P = 0.5)).

CONCLUSIONS

We conclude that circulating ghrelin levels are lower in H pylori infected people compared to those not infected; but the relationship between circulating ghrelin and eradication of H pylori is more complex.

Helicobacter pylori infection and circulating ghrelin levels - a systematic review

Background

The nature of the association between ghrelin, an orexigenic hormone produced mainly in the stomach, and Helicobacter pylori (H pylori), a bacterium that colonises the stomach, is still controversial. We examined available evidence to determine whether an association exists between the two; and if one exists, in what direction.

Methods

We reviewed original English language studies on humans reporting circulating ghrelin levels in H pylori infected and un-infected participants; and circulating ghrelin levels before and after H pylori eradication. Meta-analyses were conducted for eligible studies by combining study specific estimates using the inverse variance method with weighted average for continuous outcomes in a random effects model.

Results

Seventeen out of 27 papers that reported ghrelin levels in H pylori positive and negative subjects found lower circulating ghrelin levels in H pylori positive subjects; while 10 found no difference. A meta-analysis of 19 studies with a total of 1801 participants showed a significantly higher circulating ghrelin concentration in H pylori negative participants than in H pylori positive participants (Effect estimate (95%CI) = -0.48 (-0.60, -0.36)). However, eradicating H pylori did not have any significant effect on circulating ghrelin levels (Effect estimate (95% CI) = 0.08 (-0.33, 0.16); Test for overall effect: Z = 0.67 (P = 0.5)).

Conclusions

We conclude that circulating ghrelin levels are lower in H pylori infected people compared to those not infected; but the relationship between circulating ghrelin and eradication of H pylori is more complex.

Ghrelin endocrine cells in the human stomach during prenatal and early postnatal development

The aim of this study was to investigate the appearance, localization and density of ghrelin cells in the human stomach during prenatal development. For this purpose the antrum and corpus of embryos, fetuses and infants are stained immunohistochemically by the streptavidin-biotin technique. The presence of P/D1 cells at 11 weeks of fetal development, their highest density during the first detection and higher density in the corpus than in antrum, and their localization in the glandular base of stomach gland, all suggest that ghrelin plays a major role in the early stages of the developing stomach.

Immunolocalization of ghrelin in the stomach of Sprague-Dawley rat

To investigate the distribution of ghrelin in different regions of stomach in Sprague-Dawley rat, and attempt to compare with those of humans and other mammalian species in this study, the stomach of rats was divided into five sections, cardia, fundus, greater curvature, lesser curvature and pylorus. Immunohistochemistry and Western blotting were performed to investigate the ghrelin-producing cells. The immunolocalization and protein levels of ghrelin differed significantly in different regions of stomach in rats. It was present at a high level in the greater curvature of the pars glandularis, and the lesser curvature. In the fundus and pylorus, no ghrelin immunoreactive cells were detected. In this study, we elucidated the distribution of ghrelin-producing cells in different regions of rat stomach in detail for the first time. It is further considered that the differences of ghrelin distribution in stomach of different species may induce different stimulatory effects on fat accumulation and metabolism.

Ghrelin gene products and the regulation of food intake and gut motility

A breakthrough using "reverse pharmacology" identified and characterized acyl ghrelin from the stomach as the endogenous cognate ligand for the growth hormone (GH) secretagogue receptor (GHS-R) 1a. The unique post-translational modification of O-n-octanoylation at serine 3 is the first in peptide discovery history and is essential for GH-releasing ability. Des-acyl ghrelin, lacking O-n-octanoylation at serine 3, is also produced in the stomach and remains the major molecular form secreted into the circulation. The third ghrelin gene product, obestatin, a novel 23-amino acid peptide identified from rat stomach, was found by comparative genomic analysis. Three ghrelin gene products actively participate in modulating appetite, adipogenesis, gut motility, glucose metabolism, cell proliferation, immune, sleep, memory, anxiety, cognition, and stress. Knockdown or knockout of acyl ghrelin and/or GHS-R1a, and overexpression of des-acyl ghrelin show benefits in the therapy of obesity and metabolic syndrome. By contrast, agonism of acyl ghrelin and/or GHS-R1a could combat human anorexia-cachexia, including anorexia nervosa, chronic heart failure, chronic obstructive pulmonary disease, liver cirrhosis, chronic kidney disease, burn, and postsurgery recovery, as well as restore gut dysmotility, such as diabetic or neurogenic gastroparesis, and postoperative ileus. The ghrelin acyl-modifying enzyme, ghrelin O-Acyltransferase (GOAT), which attaches octanoate to serine-3 of ghrelin, has been identified and characterized also from the stomach. To date, ghrelin is the only protein to be octanylated, and inhibition of GOAT may have effects only on the stomach and is unlikely to affect the synthesis of other proteins. GOAT may provide a critical molecular target in developing novel therapeutics for obesity and type 2 diabetes.

Effect of the glycemic index of carbohydrates on day-long (10 h) profiles of plasma glucose, insulin, cholecystokinin and ghrelin

BACKGROUND

Low glycemic index (GI) carbohydrates have been linked to increased satiety. The drive to eat may be mediated by postprandial changes in glucose, insulin and gut peptides.

OBJECTIVE

To investigate the effect of a low and a high GI diet on day-long (10 h) blood concentrations of glucose, insulin, cholecystokinin (CCK) and ghrelin (GHR).

DESIGN

Subjects (n=12) consumed a high and a low GI diet in a randomized, crossover design, consisting of four meals that were matched for macronutrients and fibre, and differed only in carbohydrate quality (GI). Blood was sampled every 30-60 min and assayed for glucose, insulin, CCK and GHR.

RESULTS

The high GI diet resulted in significantly higher glucose and insulin mean incremental areas under the curve (IAUC, P=0.027 and P=0.001 respectively). CCK concentration was 59% higher during the first 7 h of the low GI diet (394+/-95 pmol/l min) vs the high GI diet (163+/-38 pmol/l min, P=0.046), but there was no difference over 10 h (P=0.224). GHR concentration was inversely correlated with insulin concentration (Pearson correlation -0.48, P=0.007), but did not differ significantly between the low and high GI diets.

CONCLUSIONS

Mixed meals of lower GI are associated with lower day-long concentrations of glucose and insulin, and higher CCK after breakfast, morning tea and lunch. This metabolic profile could mediate differences in satiety and hunger seen in some, but not all, studies.

Plasma obestatin levels in men with chronic atrophic gastritis

Obestatin is a recently discovered active peptide isolated from the stomach. The purpose of the present study was to investigate the modification of plasma obestatin levels in men with chronic atrophic gastritis. Men older than 65 years undergoing upper gastrointestinal endoscopy were included. All patients with chronic atrophic gastritis underwent multiple biopsies. Fasting plasma obestatin and ghrelin levels were examined in 50 men with chronic atrophic gastritis and 50 healthy men. Plasma obestatin levels were significantly lower in patients with chronic atrophic gastritis than in healthy subjects. Plasma ghrelin levels and ghrelin to obestatin ratio was decreased in men with chronic atrophic gastritis. There was a significant relationship between atrophy and decreased obestatin. A negative correlation was found between circulating obestatin levels and body mass index (BMI) in healthy subjects, but not in patients with chronic atrophic gastritis. The data indicated that chronic atrophic gastritis influenced plasma obestatin levels as well as ghrelin to obestatin ratio in elderly men.

Expression of ghrelin in fundus is increased after gastric banding in morbidly obese patients

BACKGROUND

Ghrelin, a 28 amino-acid acylated orexigenic peptide secreted by the stomach, acts on the hypothalamic arcuate nucleus which stimulates feeding behavior. Serum ghrelin level increases during fasting and decreases after a meal. Serum ghrelin is low in obese patients.Whether ghrelin is implicated in weight loss in obese patients after laparoscopic adjustable gastric banding (LAGB) is still debated. In this study, we assessed serum ghrelin level and gastric fundus expression before and 1 year after LAGB.

METHODS

Gastric fundus expression of ghrelin was assessed by immunohistochemistry using a rabbit anti-human ghrelin antibody simultaneously with serum total ghrelin levels (RIA) in 13 obese patients (2 men and 11 women) after an overnight fast, before LAGB and 1 year after. Immunostaining was "blindly" analyzed by a single pathologist, measuring the density of stained fundic cells near muscularis mucosa.

RESULTS

Mean age of the 13 patients was 41 years, and mean baseline BMI was 46 kg/m2. Pre- and post-LAGB gastric expression of ghrelin was analyzable in 11 patients. It was always identified, mostly with moderate or intense staining. Mean density of stained cells significantly increased 1 year after LAGB: 31/mm2 (21-38) before vs 38/mm2 (27-57) after surgery (P<0.01). This increase did not correlate with changes in BMI, nor did pre- or postoperative gastric expression of ghrelin correlate with the corresponding serum values.

CONCLUSION

We showed for the first time that ghrelin expression assessed by immunohistochemistry was present in the fundus of all 11 obese patients and that it was significantly increased 1 year after LAGB, which would exclude a pathogenetic role of ghrelin in weight loss after LAGB.

Serum ghrelin as a marker of atrophic body gastritis in patients with parietal cell antibodies

AIM

Autoimmune gastritis is frequently associated with autoimmune thyroiditis and other organ-specific autoimmune diseases, and may lead to atrophic body gastritis (ABG). We studied the diagnostic use of the measurement of serum ghrelin compared with other markers of gastric damage in predicting the presence of ABG in patients with autoimmune gastritis.

METHODS

We studied 233 patients with autoimmune gastritis and 211 control subjects. All patients and control subjects were screened for circulating parietal cell antibodies (PCAs) and were tested for serum ghrelin, gastrin, pepsinogen I and II, and anti-Helicobacter pylori antibody levels. A total of 52 patients and 28 control subjects underwent a gastric endoscopy.

RESULTS

In PCA/positive patients, mean (+/-sd) serum ghrelin levels were significantly lower (238 +/- 107 pmol/liter), and mean (+/-sd) serum gastrin levels were significantly higher (81.2 +/- 128.3 ng/ml), with respect to PCA/negative patients (282 +/- 104 pmol/liter and 20.7 +/- 13.3 ng/ml, respectively; P < 0.0001). Serum ghrelin and gastrin levels were inversely correlated (P = 0.004). A total of 40 patients had ABG documented by the gastric biopsy (90% in PCA/positive patients and 10% in PCA/negative patients). The receiver operating characteristic curve analysis revealed that a cutoff value for serum ghrelin of 188 pmol/liter was associated with the highest sensitivity and specificity (97.3 and 100%, respectively) in detecting gastric atrophy and was superior to gastrin (P = 0.012), PCA (P = 0.002), and the pepsinogen I/II ratio (P = 0.016) measurements.

CONCLUSIONS

Our study demonstrates that ghrelin secretion is negatively affected by autoimmune gastritis, and its serum level represents the most sensitive and specific noninvasive marker for selecting patients at high risk for ABG.

Immunohistochemical study of enterochromaffin-like cell in human gastric mucosa

Enterochromaffin-like (ECL) cell has been identified as the histamine-containing argyrophil cell in rat gastric mucosa and vigorously studied. However, there are few reports of the distribution of ECL cell in human stomach. The aim of the present study was to determine the precise distribution of ECL cell by immunohistochemical staining of histidine decarboxylase (HDC) and gastrin-cholecystokinin B receptor (CCK-BR) in human stomach, and the correlation between their distribution and that of parietal cells. Thirty specimens of surgically resected stomach were used. Parietal cell, Grimelius-silver-positive cell, gastrin, HDC- and CCK-BR-immunoreactive cell were studied on continuous cell counting in the restricted field along the lamina muscularis from the oral to the anal ends. The percentage of HDC-immunoreactive cells of endocrine cells was smaller (15%) than that of a previous report (35%) in the fundic region. HDC- and CCK-BR-immunoreactive cells were found not only in the fundic region, but also in the intermediate and pyloric regions. In the pyloric region, HDC- and CCK-BR-immunoreactive cells were found mainly in the mucosa with intestinal metaplasia. Double-positive cells were also found, but only in small numbers. This suggests that ECL cell, or a cell sharing its function, is present in the pyloric region.

Ghrelin and motilin are cosecreted from a prominent endocrine cell population in the small intestine

CONTEXT

Ghrelin is a novel hormone produced mainly in the gastric body. Hitherto, mapping studies of ghrelin cells covering the entire gastrointestinal (GI) tract in humans have been lacking. Furthermore, the phenotype of extragastric ghrelin cells is not known.

OBJECTIVE

The objective of the study was to perform a detailed mapping with specimens from all parts of the GI tract, and colocalization studies to phenotype ghrelin cells along the tract. In addition, mapping of ghrelin cells was performed in porcine GI tract, and the plasma profiles of ghrelin and motilin in blood from the porcine intestine were measured.

DESIGN

Biopsies from patients were obtained during gastroscopy or surgery. Ghrelin cell density and phenotyping was assessed with immunocytochemistry, in situ hybridization, and immunogold electron microscopy. Plasma ghrelin and motilin levels were measured in pigs, fitted with cannulas in the mesenteric vein.

RESULTS

The upper small intestine is unexpectedly rich in ghrelin cells, and these cells contribute to circulating ghrelin. Ghrelin and motilin are coproduced in the same cells in the duodenum and jejunum of both species, and ghrelin and motilin are stored in all secretory granules of such cells in humans, indicating cosecretion. The plasma profiles of ghrelin and motilin in pig were parallel, and a correlation between ghrelin and motilin (r(2) = 0.22; P < 0.001) was evident in intestinal blood.

CONCLUSIONS

The upper small intestine is an important source of ghrelin. The likely cosecretion of intestinal ghrelin and motilin suggests concerted actions of the two hormones. These data may have implications for understanding gut motility and clinical implications for dysmotility and bariatric surgery.

Determination of ghrelin immunoreactivity in the rat stomach after fasting and refeeding

Ghrelin is a recently discovered hormone secreted by cells of the stomach. The aim of this study was to investigate fasting and refeeding induced alterations on ghrelin immunolabelling of cells of the stomach. Thirty-six adult male Wistar rats were used in this study. Rats were divided into six groups. Group I: control group; Group II: rats fasted for 7 days; Group III: rats fed for 1 day after 7 days of fasting; Group IV: rats fed for 3 days after 7 days of fasting; Group V: rats fed for 5 days after 7 days of fasting; Group VI: rats fed for 7 days after 7 days of fasting. At the end of the experiment, rats were sacrificed and stomach tissues were processed for imunohistochemistry to localize ghrelin. Ghrelin-immunopositive cells were detected only in the mucosal lining of the stomach. After fasting for 7 days, the number of ghrelin-immunopositive cells increased significantly compared to the control rats. Following refeeding, the number of ghrelin-immunoreactive cells was reduced to a level comparable to the controls. Therefore, fasting and refeeding after fasting were observed to result in changes in ghrelin immunoreactivity in the cells of the stomach. We conclude that ghrelin is highly expressed in the stomach and that fasting increases the expression of ghrelin in the stomach, but this expression decreases after refeeding. Our results indicate that regulation of ghrelin is a process probably involved in the long-term control of nutritional states.

Biochemistry of ghrelin precursor peptides

Since its discovery in 1999, the stomach-derived hormone ghrelin has been studied intensively. Proghrelin is 94 amino acids long in mammals and this undergoes proteolytic processing to produce ghrelin [residues 1-28 of proghrelin(1-94)] and the C-terminal peptide C-ghrelin, which likely contains the entire 66 amino acids of the prohormone C-terminus. The accumulating data identifies ghrelin as having important roles in growth hormone (GH) release, appetite, metabolism, energy balance, cardiovascular function, reproduction, and bone growth. The most striking feature of ghrelin is that it can be acylated at its third amino acid residue (usually Ser), usually in the form of n-octanoyl group (C8:0). Approximately 10-20% of circulating ghrelin is acylated and this feature confers its GH releasing ability, mediated by the GH secretagogue receptor (GHSR). In contrast, the remaining 80-90% of circulating ghrelin is desacylated. Desacyl ghrelin was initially thought to be inactive, but recent in vivo and in vitro evidences have identified biological actions for this peptide, independent of GHSR. Whether C-ghrelin has bioactivity remains to be determined, but it is known that plasma concentrations of this peptide respond to endocrine and metabolic manipulations in the same fashion as ghrelin itself. A third putative proghrelin peptide, termed "obestatin" has been mooted, but confirmatory biochemical and functional evidences supporting the existence of this peptide have not been forthcoming, suggesting it to be a biochemical miscalculation. This chapter will address biochemical aspects of proghrelin peptides and point to potential avenues for future work.

Gastroduodenal mucosal defense

PURPOSE OF REVIEW

The duodenum absorbs nearly all secreted gastric acid. Carbonic anhydrases facilitate transmucosal acid movement. The upper gastrointestinal tract must resist a variety of injuries, including those caused by ingested noxious substances, acid, ischemia/reperfusion, and infections such as Helicobacter pylori. The results are similar, however, regardless of insult: inflammation, ulceration, or metaplasia/dysplasia. In the past year, there have been prominent findings suggesting that oxidative stress and the formation of reactive oxygen species may play a pivotal role in all forms of injury, and that antioxidants may be the key to injury prevention and healing.

RECENT FINDINGS

Oxidative injury may be a common mechanism by which the upper gastrointestinal mucosa responds to noxious insults. Endogenous antioxidants, such as ghrelin, L-carnitine, and annexin-1 attenuate the oxidative-stress response. Similarly, exogenous antioxidants have also been shown to decrease inflammation, upregulate free radical scavengers, and prevent the formation of reactive oxygen species.

SUMMARY

Many studies published in the past year have linked oxidative stress to a variety of upper gastrointestinal insults. Exogenous and endogenous antioxidant compounds prevent the oxidative stress response. The future holds great promise for the development of pharmaceuticals with antioxidant properties that are safe, efficacious, and inexpensive.

Ghrelin and the short- and long-term regulation of appetite and body weight

Ghrelin, an acylated upper gastrointestinal peptide, is the only known orexigenic hormone. Considerable evidence implicates ghrelin in mealtime hunger and meal initiation. Circulating levels decrease with feeding and increase before meals, achieving concentrations sufficient to stimulate hunger and food intake. Preprandial ghrelin surges occur before every meal on various fixed feeding schedules and also among individuals initiating meals voluntarily without time- or food-related cues. Ghrelin injections stimulate food intake rapidly and transiently, primarily by increasing appetitive feeding behaviors and the number of meals. Preprandial ghrelin surges are probably triggered by sympathetic nervous output. Postprandial suppression is not mediated by nutrients in the stomach or duodenum, where most ghrelin is produced. Rather, it results from post-ingestive increases in lower intestinal osmolarity (information probably relayed to the foregut via enteric nervous signaling), as well as from insulin surges. Consequently, ingested lipids suppress ghrelin poorly compared with other macronutrients. Beyond a probable role in meal initiation, ghrelin also fulfills established criteria for an adiposity-related hormone involved in long-term body-weight regulation. Ghrelin levels circulate in relation to energy stores and manifest compensatory changes in response to body-weight alterations. Ghrelin crosses the blood-brain barrier and stimulates food intake by acting on several classical body-weight regulatory centers, including the hypothalamus, hindbrain, and mesolimbic reward system. Chronic ghrelin administration increases body weight via diverse, concerted actions on food intake, energy expenditure, and fuel utilization. Congenital ablation of the ghrelin or ghrelin-receptor gene causes resistance to diet-induced obesity, and pharmacologic ghrelin blockade reduces food intake and body weight. Ghrelin levels are high in Prader-Willi syndrome and low after gastric bypass surgery, possibly contributing to body-weight alterations in these settings. Extant evidence favors roles for ghrelin in both short-term meal initiation and long-term energy homeostasis, making it an attractive target for drugs to treat obesity and/or wasting disorders.