Role of ghrelin in the pathophysiology of gastrointestinal disease

Current Concepts in Gastroparesis and Gastric Neuromuscular Disorders-Pathophysiology, Diagnosis, and Management

Upper gastrointestinal concerns including gastroparesis-like symptoms affect a large portion of the population, and determining the culprit condition can be difficult due to largely shared symptoms, clinical course, pathophysiology, and treatment pathways. The understanding of gastric neuromuscular disorders (GNDs) is emerging as a heterogeneous group encompassing conditions from gastroparesis to functional dyspepsia with chronic nausea, early satiety, bloating, or abdominal pain, irrespective of gastric emptying. This article aims to review the current concepts in gastroparesis and GNDs including pathophysiology, diagnosis, and management. While some established standards in their diagnosis and management exist, a number of novel diagnostics are becoming available. Durable therapeutic options are notably limited for such common conditions with chronic and debilitating symptoms, and neuromodulators may play a key role in symptom control, which has been previously under-recognized and underutilized. Advances in both pharmacologic treatment targets as well as noninvasive and invasive interventions and devices show promise in improving the experience of patients with gastroparesis-like symptoms. At this time, treatment of GNDs requires comprehensive multidisciplinary care from providers to achieve successful treatment outcomes.

Efficacy of B - mode and elastography ultrasound technique in the prediction of Helicobacter pylori: a prospective study

BACKGROUND

Helicobacter pylori (HP) affect nearly 50% of the world's population and can colonize the submucosal and mucosal layers of the stomach wall, causing inflammation leading to a thickening of these layers. The study aimed to evaluate the application value of transabdominal ultrasonography combined with elastography in the prediction of HP using HP Fecal Antigen Test as gold standard.

METHOD

This prospective case-control study was conducted in 174 participants classified into three groups: Group A: Symptomatic patients with thickened stomach antral and evident HP infection on fecal antigen test results, Group B: Symptomatic patients with thickened antral and no evident HP infection on fecal antigen test results, and Group C: control group of asymptomatic individuals with negative HP screening to predict the diagnostic accuracy of B-mode ultrasound and elastography in the prediction of HP pylori.

RESULTS

Positive HP patients had higher values of antral wall thickness (AWT), mucosal layer thickness (MLT), MLT/AWT ratio, SR (strain ratio), and a combination of AWT and SR: 5.57 ± 0.55 mm, 2.96 ± 0.45 mm, 0.53 ± 0.06 mm, 3.21 ± 0.43, and 8.79 ± 0.68 mm, respectively. In comparison, negative HP patients had values of 4.61 ± 0.47 mm, 2.05 ± 0.42 mm, 0.41 ± 0.08 mm, 2.51 ± 0.42 mm, and 7.13 ± 0.62 mm, respectively, and the control groups had values of 3.53 ± 0.36 mm, 1.47 ± 0.25 mm, 0.40 ± 0.06 mm, 1.81 ± 0.41, and 5.35 ± 0.55 mm, respectively (p < 0.001). The sensitivity of B-mode ultrasonography, elastography, and the combination of the two was 98%, 95.1%, and 98.4%, respectively, and the diagnostic accuracy was 98.4%, 98.3%, and 100%, respectively.

CONCLUSION

B-mode ultrasonography and elastography exhibit high discriminatory power in distinguishing symptomatic HP patients from normal individuals and differentiating + HP from - HP, with greater discriminatory power when combined both modes.

Bariatric arterial embolization slows gastric emptying and improves postprandial glycaemia in obese dogs with impaired glucose tolerance

AIM

To evaluate the effects of bariatric arterial embolization (BAE) on gastric emptying of, and the glycaemic response to, an oral glucose load in an obese canine model with impaired glucose tolerance.

METHODS

Eleven male dogs were fed a high-fat, high-fructose diet for 7 weeks before receiving BAE, which involved selective embolization of the left gastric artery (n = 5; 14.9 ± 0.8 kg), or the sham (n = 6; 12.6 ± 0.8 kg) procedure. Postprocedural body weight was measured weekly for 4 weeks. Prior to and at 4 weeks postprocedure, a glucose solution containing 13C-acetate was administered orally for evaluation of the gastric half-emptying time (T50) and the glycaemic response. The relationship between the changes in the blood glucose area under the curve over the first 60 minutes (AUC0-60min) and the T50 was also assessed.

RESULTS

At 4 weeks postprocedure, BAE reduced body weight (BAE vs. the sham procedure: -5.7% ± 0.9% vs. 3.5% ± 0.9%, P < .001), slowed gastric emptying (T50 at baseline vs. postprocedure: 75.5 ± 2.0 vs. 82.5 ± 1.8 minutes, P = .021 in the BAE group; 73.8 ± 1.8 vs. 74.3 ± 1.9 minutes in the sham group) and lowered the glycaemic response to oral glucose (AUC0-60min at baseline vs. postprocedure: 99.2 ± 13.7 vs. 67.6 ± 9.8 mmol·min/L, P = .043 in the BAE group; 100.2 ± 13.4 vs. 103.9 ± 14.6 mmol·min/L in the sham group). The change in the glucose AUC0-60min correlated inversely with that of the T50 (r = -0.711; P = .014).

CONCLUSIONS

In a canine model with impaired glucose tolerance, BAE, while reducing body weight, slowed gastric emptying and attenuated the glycaemic response to an oral glucose load.

Therapeutic potential of ghrelin/GOAT/GHSR system in gastrointestinal disorders

Ghrelin, a peptide primarily secreted in the stomach, acts via the growth hormone secretagogue receptor (GHSR). It regulates several physiological processes, such as feeding behavior, energy homeostasis, glucose and lipid metabolism, cardiovascular function, bone formation, stress response, and learning. GHSR exhibits significant expression within the central nervous system. However, numerous murine studies indicate that ghrelin is limited in its ability to enter the brain from the bloodstream and is primarily confined to specific regions, such as arcuate nucleus (ARC) and median eminence (ME). Nevertheless, the central ghrelin system plays an essential role in regulating feeding behavior. Furthermore, the role of vagal afferent fibers in regulating the functions of ghrelin remains a major topic of discussion among researchers. In recent times, numerous studies have elucidated the substantial therapeutic potential of ghrelin in most gastrointestinal (GI) diseases. This has led to the development of numerous pharmaceutical agents that target the ghrelin system, some of which are currently under examination in clinical trials. Furthermore, ghrelin is speculated to serve as a promising biomarker for GI tumors, which indicates its potential use in tumor grade and stage evaluation. This review presents a summary of recent findings in research conducted on both animals and humans, highlighting the therapeutic properties of ghrelin system in GI disorders.

Impact of Resistance and Endurance Training on Ghrelin and Plasma Leptin Levels in Overweight and Obese Subjects

Exercise training is a valuable tool for improving body weight and composition in overweight or obese adults, which leads to a negative energy balance. It is relevant to consider whether exercise can help people lose weight or prevent weight gain because any energy expended in exercise increases the severity of hunger and promotes food consumption. Over the past decade, the identification of the circulating peptide ghrelin, which alerts the brain to the body's nutritional state, has significantly expanded our understanding of this homeostatic mechanism that controls appetite and body weight. To shed more light on this issue, we decided to investigate the effects of resistance and endurance training on plasma ghrelin and leptin levels. In addition, we sought to understand the mechanisms by which acute and chronic exercise can regulate hunger. This review analyzes studies published in the last fifteen years that focused on changes suffered by ghrelin, leptin, or both after physical exercise in overweight or obese individuals. Most studies have shown a decrease in leptin levels and an increase in ghrelin levels in these cases. Exercise regimens that support weight maintenance need further investigation.

The relationship between small intestinal bacterial overgrowth and constipation in children - a comprehensive review

Small intestinal bacterial overgrowth (SIBO) is characterized by an increase in the bacterial population of the small intestine due to an imbalance between the amount of bacteria and the intestinal barrier. Pediatric SIBO presents with a wide spectrum of symptoms, ranging from mild gastrointestinal complaints to malabsorption or malnutrition. Breath tests are commonly used as noninvasive diagnostic tools for SIBO, but a standardized methodology is currently unavailable. Intestinal flora produces methane which slows intestinal transit and increases the contractile activity of small intestine. Emerging literature suggests a correlation between overgrowth of methanogenic bacteria in the intestines and constipation. Treatment of SIBO involves administration of antibacterial therapy in addition to management of underlying conditions and optimal dietary adjustments. However, research on antibiotic treatment for pediatric patients with constipation and SIBO is limited and has yielded conflicting results. In the current review, we summarize the state-of-the-art of the field and discuss previous treatment attempts and currently used regimens for SIBO patients with constipation, with a focus on pediatric populations.

Thyroid disorders and gastrointestinal dysmotility: an old association

Gastrointestinal motility symptoms may be closely related to thyroid diseases. Sometimes, such symptoms are the only thyroid disease-related clue although the degree of the symptoms may vary. The exact mechanism of action of thyroid hormones on gastrointestinal motility is not completely understood, however, a clue lies in the fact that muscle cell receptors can be directly acted upon by thyroxines. Both hypo- and hyperthyroidism can cause impairment of gastrointestinal motility, modifying structure and function of pharynx and esophagus, and regulating esophageal peristalsis through neuro-humoral interaction. In hyperthyroid patients, alterations of postprandial and basic electric rhythms have been observed at gastro-duodenal level, often resulting in slower gastric emptying. Gastric emptying may also be delayed in hypothyroidism, but an unrelated gastric mucosa-affecting chronic modification may also cause such pattern. Hyperthyroidism commonly show malabsorption and diarrhoea, while hypothyroidism frequently show constipation. In summary, it can be stated that symptoms of gastrointestinal motility dysfunction can be related to thyroid diseases, affecting any of the gastrointestinal segment. Clinically, the typical thyroid disease manifestations may be missing, borderline, or concealed because of intercurrent sicknesses. Motility-linked gastrointestinal problems may easily conceal a misdetected, underlying dysthyroidism that should be carefully analyzed. Here, we aim to elaborate on the associations between thyroid disorders and GI dysmotility and the common clinical manifestations associated with GI dysmotility.

Weight Regain after Metabolic Surgery: Beyond the Surgical Failure

Patients undergoing metabolic surgery have factors ranging from anatomo-surgical, endocrine metabolic, eating patterns and physical activity, mental health and psychological factors. Some of the latter can explain the possible pathophysiological neuroendocrine, metabolic, and adaptive mechanisms that cause the high prevalence of weight regain in postbariatric patients. Even metabolic surgery has proven to be effective in reducing excess weight in patients with obesity; some of them regain weight after this intervention. In this vein, several studies have been conducted to search factors and mechanisms involved in weight regain, to stablish strategies to manage this complication by combining metabolic surgery with either lifestyle changes, behavioral therapies, pharmacotherapy, endoscopic interventions, or finally, surgical revision. The aim of this revision is to describe certain aspects and mechanisms behind weight regain after metabolic surgery, along with preventive and therapeutic strategies for this complication.

Expression of Genes Encoding Selected Orexigenic and Anorexigenic Peptides and Their Receptors in the Organs of the Gastrointestinal Tract of Calves and Adult Domestic Cattle (Bos taurus taurus)

The regulation of food intake occurs at multiple levels, and two of the components of this process are orexigenic and anorexigenic peptides, which stimulate or inhibit appetite, respectively. The study of the function of these compounds in domestic cattle is essential for production efficiency, animal welfare, and health, as well as for economic benefits, environmental protection, and the contribution to a better understanding of physiological aspects that can be applied to other species. In this study, the real-time PCR method was utilized to determine the expression levels of GHRL, GHSR, SMIM20, GPR173, LEP, LEPR, and NUCB2 (which encode ghrelin, its receptor, phoenixin-14, its receptor, leptin, its receptor, and nesfatin-1, respectively) in the gastrointestinal tract (GIT) of Polish Holstein-Friesian breed cattle. In all analyzed GIT segments, mRNA for all the genes was present in both age groups, confirming their significance in these tissues. Gene expression levels varied distinctly across different GIT segments and between young and mature subjects. The differences between calves and adults were particularly pronounced in areas such as the forestomachs, ileum, and jejunum, indicating potential changes in peptides regulating food intake based on the developmental phase. In mature individuals, the forestomachs predominantly displayed an increase in GHRL expression, while the intestines had elevated levels of GHSR, GPR173, LEP, and NUCB2. In contrast, the forestomachs in calves showed upregulated expressions of LEP, LEPR, and NUCB2, highlighting the potential importance of peptides from these genes in bovine forestomach development.

Mechanism of gastrointestinal injury in COVID-19 and potential use of ghrelin therapy

In Corona Virus Disease 2019 (COVID-19), the most obvious symptoms occur in the respiratory and digestive systems, posing a serious threat to the health of patients. Decreased appetite is the most common digestive system symptom and is an important predictor of mortality. A large number of patients have decreased appetite after infection and do not show obvious organic disease characteristics. Currently, no drugs can directly alleviate such symptom. In order to reduce the number of severe and critically ill patients and decrease the hospitalization rate, it is very important to understand the pathogenic mechanism of appetite loss caused by COVID-19 and manage such symptom. Ghrelin is a key gastric hormone that has anti-inflammatory, neuroprotective, and antidepressant effects. In this paper, we will review the progress in the understanding of the mechanism of appetite loss associated with COVID-19, and introduce a potential therapeutic drug, ghrelin.

Cannabis sativa as a Treatment for Obesity: From Anti-Inflammatory Indirect Support to a Promising Metabolic Re-Establishment Target

Introduction: Obesity is defined as an excess of accumulation of fat that can be harmful to health. Storage of excess fat in the adipose tissue triggers an inflammatory process, which makes obesity a low-grade chronic inflammatory disease. Obesity is considered a complex and multifactorial disease; hence, no intervention strategy appears to be an ideal treatment for all individuals. Therefore, new therapeutic alternatives are often studied for the treatment of this disease. Currently, herbal medicines are gaining ground in the treatment of obesity and its comorbidities. In this context, much attention is being paid to Cannabis sativa derivatives, and their therapeutic functions are being widely studied, including in treating obesity. Objective: Highlight the pharmacological properties of Δ9-tetrahydrocannabivarin (THCV), Δ9-tetrahydrocannabidinol (THC), and cannabidiol (CBD), the predominant isolated components of Cannabis sativa, as well as its therapeutic potential in the treatment of obesity. Methods: This is a narrative review that shows the existing scientific evidence on the clinical application of Cannabis sativa as a possible treatment for obesity. Data collection was performed in the PubMed electronic database. The following word combinations were used: Cannabis and obesity, Cannabis sativa and obesity, THCV and obesity, THC and obesity, CBD and obesity, and Cannabis sativa and inflammation. Results: Evidence shows that Cannabis sativa derivatives have therapeutic potential due to their anti-inflammatory properties. In addition, people who use cannabis have a lower body mass index than those who do not, making the plant an option to reduce and reverse inflammation and comorbidities in obesity. Conclusion: It is concluded that phytocannabinoids derived from Cannabis sativa have therapeutic potential due to its anti-inflammatory, antioxidant, and neuroprotective properties, making the plant a study option to reduce and reverse inflammation and comorbidities associated with obesity.

The role of microbiota and enteroendocrine cells in maintaining homeostasis in the human digestive tract

The microbiota is a heterogeneous ecosystem consisting of diverse microorganisms unique to an individual, playing a crucial role in maintaining human body homeostasis. The microbiota, as a suggested endocrine organ, is also capable of producing and regulating hormones, playing an important role in food processing, synthesis of vitamins, pathogen displacement, and influencing functions of distant systems and organs. The efficient connections between the brain and intestines and microbiota ensure the maintenance of the digestive tract homeostasis, with the bidirectional brain and gut axis playing an important role in the regulation of digestion. Enteroendocrine cells (EECs) are a fascinating example of highly specified cells scattered throughout the gastrointestinal (GI) tract. They produce and release signaling molecules (hormones), thus modulate homeostatic functions. EECs are believed to be crucial sensors of gut microbiota or/and microbial metabolites, secreting peptide hormones and cytokines in response to them. The diet, microbiota, and EECs are inevitably dependent on one another, thus together (nutrients, microbiota, enterohormones) affect metabolism. This manuscript reviews the role of various components of the brain-gut axis in digestive and absorption processes, as well as the maintenance of digestive tract homeostasis and the consequences of disturbances in the individual components of this axis.

Gastroparesis in Parkinson Disease: Pathophysiology, and Clinical Management

Patients with Parkinson disease (PD) experience a range of non-motor symptoms, including gastrointestinal symptoms. These symptoms can be present in the prodromal phase of the disease. Recent advances in pathophysiology reveal that α-synuclein aggregates that form Lewy bodies and neurites, the hallmark of PD, are present in the enteric nervous system and may precede motor symptoms. Gastroparesis is one of the gastrointestinal involvements of PD and is characterized by delayed gastric emptying of solid food in the absence of mechanical obstruction. Gastroparesis has been reported in nearly 45% of PD. The cardinal symptoms include early satiety, postprandial fullness, nausea, and vomiting. The diagnosis requires an appropriate test to confirm delayed gastric emptying, such as gastric scintigraphy, or breath test. Gastroparesis can lead to malnutrition and impairment of quality of life. Moreover, it might interfere with the absorption of antiparkinsonian drugs. The treatment includes dietary modifications, and pharmacologic agents both to accelerate gastric emptying and relieve symptoms. Alternative treatments have been recently developed in the management of gastroparesis, and their use in patients with PD will be reported in this review.

Evaluation of Appetite-Regulating Hormones ın Young Children with Autism Spectrum Disorder

This study aimed to investigate the role of leptin, ghrelin, neuropeptide Y, and nesfatin-1 in young children with autism spectrum disorder (ASD). A total of 44 children with ASD and 44 healthy controls aged 18-60 months were included. Plasma levels of hormones were measured using commercial enzyme-linked immunosorbent assay kits. Plasma leptin and ghrelin levels were significantly higher in the ASD group than in the control group. However, no significant difference for plasma neuropeptide Y and nesfatin-1 levels was detected between the groups. No relation was found between the severity of ASD symptoms, severity of eating problems, and plasma levels of hormones. Leptin and ghrelin may play a potential role in the pathogenesis of ASD.

Knockdown of ghrelin-O-acyltransferase attenuates colitis through the modulation of inflammatory factors and tight junction proteins in the intestinal epithelium

Ghrelin-O-acyltransferase (GOAT) is a membrane-bound enzyme that attaches eight-carbon octanoate to a serine residue in ghrelin and thereby acylates inactive ghrelin to produce active ghrelin. In this study, we investigated the function of GOAT in the intestinal mucosal barrier. The intestinal mucosal barrier prevents harmful substances such as bacteria and endotoxin from entering the other tissues, organs, and blood circulation through the intestinal mucosa. Here, we established 5% dextran sodium sulfate (DSS)-induced colitis in mice and found that the body weight and colon weight were significantly decreased in these mice. Furthermore, increased inflammation and apoptosis were observed in the tissues of DSS-induced colitis mice, with increased expression of tumor necrosis factor-α, interleukin-6, phosphorylation of nuclear factor kappa B-p65 (p-NF-κB-p65), and cleaved caspase-3, and decreased expression of tight junction (TJ) proteins such as zonula occluden-1 and occludin. The knockdown of GOAT significantly attenuated colitis-induced inflammation responses and apoptosis, while GOAT overexpression significantly enhanced the induction of colitis. These results suggest that knockdown of GOAT may attenuate colitis-induced inflammation, ulcers, and fecal occult blood by decreasing the intestinal mucosal permeability via the modulation of inflammatory factors and TJ proteins.

Peptides from Natural or Rationally Designed Sources Can Be Used in Overweight, Obesity, and Type 2 Diabetes Therapies

Overweight and obesity are among the most prominent health problems in the modern world, mostly because they are either associated with or increase the risk of other diseases such as type 2 diabetes, hypertension, and/or cancer. Most professional organizations define overweight and obesity according to individual body-mass index (BMI, weight in kilograms divided by height squared in meters). Overweight is defined as individuals with BMI from 25 to 29, and obesity as individuals with BMI ≥30. Obesity is the result of genetic, behavioral, environmental, physiological, social, and cultural factors that result in energy imbalance and promote excessive fat deposition. Despite all the knowledge concerning the pathophysiology of obesity, which is considered a disease, none of the existing treatments alone or in combination can normalize blood glucose concentration and prevent debilitating complications from obesity. This review discusses some new perspectives for overweight and obesity treatments, including the use of the new orally active cannabinoid peptide Pep19, the advantage of which is the absence of undesired central nervous system effects usually experienced with other cannabinoids.

Effects of Irisin Compared with Exercise on Specific Metabolic and Obesity Parameters in Female Mice with Obesity

Objective: We aimed to analyze the changes in metabolic parameters after administration of irisin to obese female mice. Materials and Methods: Sixty mice aged 5-6 weeks were randomized into three groups as irisin, exercise, and control. The control and irisin group remained sedentary, whereas the exercise group started free wheel exercising 6 weeks after the start of the study. The irisin group received irisin after 20 weeks. All mice were sacrificed at the 22nd week of the study, and obesity-related metabolic parameters were analyzed. Results: There was no significant difference between the irisin and exercise groups in weight gain (P > 0.05). By contrast, weight gain in the control group was significantly higher compared with the irisin and exercise groups (P < 0.05). Serum bone morphogenetic protein (BMP), ghrelin, insulin, kisspeptin, leptin, and visfatin levels were statistically lower in the irisin and exercise groups compared with the control group, but no significance was detected between the irisin and exercise groups (P < 0.05 for all parameters). Conclusion: Similar to the effect of exercise, irisin injections resulted in the amelioration of certain obesity-related parameters such as the concentration of adipokines, BMP4, insulin, and ghrelin. Its role as a potential alternative to exercise needs to be further studied.

Altered Functional Connectivity of the Amygdala and Sex Differences in Functional Dyspepsia

INTRODUCTION

The influence of sex on the prevalence and clinical manifestations of functional dyspepsia (FD) has recently been a topic of increasing interest. However, brain MRI pathology based on sexual dimorphism in FD has not yet been investigated. The amygdala, which plays a vital role in processing gastrointestinal signals, may be associated with the sex-related pathophysiology of FD.

METHODS

We investigated the resting-state functional connectivity (rsFC) of amygdala subregions in patients with FD and healthy subjects as well as the sex differences between male and female FD patients.

RESULTS

The results showed that FD patients manifested altered rsFC in the basolateral amygdala (BLA) and centromedial amygdala subregions compared with HS and that female FD patients showed increased BLA rsFC with the insula (INS) and decreased BLA rsFC with the medial prefrontal cortex and dorsal lateral prefrontal cortex compared with male FD patients and female HS.

DISCUSSION

Our findings suggest that FD females tend to have more severe dysfunction of cognitive-affective processing among the brain regions associated with the salience network, central executive network, and default mode network.

Relationship between irritable bowel syndrome and plasma and tissue ghrelin levels

BACKGROUND/AIMS

This study aimed to evaluate the relationship between irritable bowel syndrome (IBS) and plasma and tissue ghrelin levels.

MATERIALS AND METHODS

Patients who had undergone gastroscopy procedure for any reason previously were enrolled in the study. Among these, patients with IBS symptoms were evaluated according to the Roma III criteria. The healthy control group comprised patients with no IBS symptom and had undergone gastroscopy procedure for another reason. The plasma ghrelin level and tissue ghrelin level obtained by immunohistochemical examination of biopsy specimens taken from the gastric antrum and corpus were evaluated in all participants.

RESULTS

The mean age of 90 participants was 43.64}12.64 years. The median value of the plasma ghrelin level was 3.29 (1.2-12.7) in the diarrhea group (IBS-D), 1.49 (0.82-7.08) in the constipation group (IBS-C), and 1.5 (0.2-3.7) in the control group. The plasma ghrelin levels between the groups were found to be significantly higher in IBS-D than in IBS-C and the control groups (p=0.001 and p=0.001, respectively). On comparing antral mucosal gland biopsy outcomes among the groups, staining intensity score was found to be significantly high in IBS-C as compared with the control group, whereas no significant difference was observed between IBS-D and the control groups (p=0.020 and p=0.429, respectively).

CONCLUSION

The plasma ghrelin level in IBS-D and the staining intensity in the antral mucosal gland in IBS-C were found to be significantly higher. In addition, there was no difference between the groups in terms of ghrelin staining intensity in the gastric corpus.

Contribution of ghrelin to functional gastrointestinal disorders' pathogenesis

Functional gastrointestinal disorders (FGID) are heterogeneous disorders with a variety of clinical manifestations, primarily defined by signs and symptoms rather than a definite underlying cause. Their pathophysiology remains obscure and, although it is expected to differ according to the specific FGID, disruptions in the brain-gut axis are now thought to be a common denominator in their pathogenesis. The hormone ghrelin is an important component of this axis, exerting a wide repertoire of physiological actions, including regulation of gastrointestinal motility and protection of mucosal tissue. Ghrelin's gene shows genetic polymorphism, while its protein product undergoes complex regulation and metabolism in the human body. Numerous studies have studied ghrelin's relation to the emergence of FGIDs, its potential value as an index of disease severity and as a predictive marker for symptom relief during attempted treatment. Despite the mixed results currently available in scientific literature, the plethora of statistically significant findings shows that disruptions in ghrelin genetics and expression are plausibly related to FGID pathogenesis. The aim of this paper is to review current literature studying these associations, in an effort to uncover certain patterns of alterations in both genetics and expression, which could delineate its true contribution to FGID emergence, either as a causative agent or as a pathogenetic intermediate.

Enhancement of ghrelin-signaling system by Rikkunshi-To attenuates teriparatide-induced pica in rats

Teriparatide is clinically used for the treatment of osteoporosis; however, nausea is often observed in patients. Its insufficient control affects the ability to continue teriparatide therapy. Rikkunshi-To (RKT), a traditional Japanese herbal medicine, improves the gastrointestinal function via activation of the ghrelin-signaling system. We investigated the therapeutic effects of RKT on teriparatide-induced nausea in rats and the involvement of ghrelin in these effects. We previously reported that ovariectomized rats showed pica (kaolin ingestion), a behavior that can be used to assess nausea in rats, after the subcutaneous administration of teriparatide; thus, the behavior was used as an index of nausea. Ovariectomized rats were fed diets with or without RKT (1%) for 2 weeks, and then they received the subcutaneous injection of teriparatide (400 μg/kg). Teriparatide significantly increased the incidence of pica, while suppressing intestinal motility and plasma ghrelin levels in rats fed normal diets; however, rats fed diets with RKT showed improvements in all of the teriparatide-induced adverse reactions. These therapeutic effects were antagonized by a ghrelin receptor antagonist ([D-Lys³]-GHRP-6; 200 nmol/rat). These findings suggest that the enhancement of ghrelin-signaling is involved in RKT's therapeutic effect, and that RKT is a potentially useful treatment for teriparatide-induced nausea.

Ghrelin and Obesity: Identifying Gaps and Dispelling Myths. A Reappraisal

The etiology of obesity is complex. Environmental and genetic causes have been implicated in the development of this disease. Ghrelin is a hormone known to stimulate appetite. There are numerous possible actions through which ghrelin exerts its effect in the body: a) Overproduction of ghrelin, b) reduced ghrelin following meals, and c) increased receptor sensitivity to ghrelin action. Sleeve gastrectomy, a bariatric procedure, leads to reduction of ghrelin levels and subsequently to weight loss. However, there are many limitations to measurement of the fasting plasma level of the active form of ghrelin. The establishment of the exact correlation between ghrelin, appetite and obesity could be vital for the fight against obesity.

Gastrointestinal neuroendocrine peptides/amines in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic recurrent condition whose etiology is unknown, and it includes ulcerative colitis, Crohn’s disease, and microscopic colitis. These three diseases differ in clinical manifestations, courses, and prognoses. IBD reduces the patients’ quality of life and is an economic burden to both the patients and society. Interactions between the gastrointestinal (GI) neuroendocrine peptides/amines (NEPA) and the immune system are believed to play an important role in the pathophysiology of IBD. Moreover, the interaction between GI NEPA and intestinal microbiota appears to play also a pivotal role in the pathophysiology of IBD. This review summarizes the available data on GI NEPA in IBD, and speculates on their possible role in the pathophysiology and the potential use of this information when developing treatments. GI NEPA serotonin, the neuropeptide Y family, and substance P are proinflammatory, while the chromogranin/secretogranin family, vasoactive intestinal peptide, somatostatin, and ghrelin are anti-inflammatory. Several innate and adaptive immune cells express these NEPA and/or have receptors to them. The GI NEPA are affected in patients with IBD and in animal models of human IBD. The GI NEPA are potentially useful for the diagnosis and follow-up of the activity of IBD, and are candidate targets for treatments of this disease.

The Gut and Nonmotor Symptoms in Parkinson's Disease

Gastrointestinal (GI) symptoms are one of the most common nonmotor symptoms (NMS) in patients with Parkinson's disease (PD) involving the whole GI tract (GIT) and being evident throughout the whole course of the disease. Furthermore, constipation serves as a risk factor for PD as well as an early prodromal NMS of PD. The gut as gateway to the environment with its enteric nervous system (ENS) plays a crucial role in the neurodegenerative process that leads to PD. Alpha-synucleinopathy as the pathological hallmark of PD could be found within the whole GIT in a rostrocaudal gradient interacting with the ENS, the gut microbiome, and enteric glial cells. Bidirectional interactions between the ENS and the central nervous system (CNS) via a brain-gut-enteric microbiota axis have been reported. As well as there is evidence out of animal, autopsy, and epidemiological studies that α-synuclein spreads via rostrocranial transmission by transsynaptic cell-to-cell transfer via the sympathetic and parasympathetic nervous system to the CNS causing the typical neuropathological changes of PD. Recognition of GI NMS as prodromal markers of PD as well as a better understanding of the brain-gut connection offers new insights in the pathophysiology of PD and might provide the opportunity of PD diagnosis before CNS involvement. Hereby the opportunity for development of neuroprotective and disease-modifying therapeutics, respectively, seem to be promising. This chapter covers the variety of GI NMS and its consequences in PD as well as the important role of the gut as part of the pathological process in PD.

The obestatin/ghrelin ratio and ghrelin genetics in adult celiac patients before and after a gluten-free diet, in irritable bowel syndrome patients and healthy individuals

BACKGROUND

Ghrelin levels and obestatin/ghrelin ratio have been proposed as activity markers in ulcerative colitis, but no data are available in celiac disease (CD) and irritable bowel syndrome (IBS). Our aims were as follows: (a) to assess obestatin and ghrelin concentrations in adult active CD patients, diarrhea-predominant IBS (IBS-d), and healthy controls (HC) in relation to intestinal permeability; (b) to evaluate the ghrelin-obestatin profile in CD patients after a 1-year gluten-free diet (GFD); and (c) to establish the impact of ghrelin genetics.

METHODS

The study included 31 CD patients, 28 IBS-d patients, and 19 HC. Intestinal permeability, assayed by high-performance liquid chromatography determination of urinary lactulose (La)/mannitol (Ma), and circulating concentrations of obestatin, ghrelin, and their ratio were evaluated at enrollment and after GFD. The ghrelin single nucleotide polymorphisms Arg51Gln (rs34911341), Leu72Met (rs696217), and Gln90Leu (rs4684677) were analyzed.

RESULTS

Intestinal permeability was impaired in CD patients and ameliorated after GFD. Ghrelin was significantly (P=0.048) higher and the obestatin/ghrelin ratio was significantly (P=0.034) lower in CD patients compared with both IBS-d and HC, and GFD reduced the peptide levels, but without reaching the concentrations in HC. Significant differences (P<0.05) were found in the Leu72Met polymorphism among groups, with the reduction of the GT genotype and the T allele in both CD and IBS-d patients compared with HC.

CONCLUSION

Intestinal permeability is altered in CD, but not in IBS-d patients, and ghrelin levels increase in CD patients as observed in other inflammatory conditions. Moreover, a role for ghrelin genetics is hypothesized in sustaining the many pathogenetic components of these different pathologies, but with a similar symptom profile.

Ghrelin upregulates PepT1 activity in the small intestine epithelium of rats with sepsis

BACKGROUND

Sepsis causes nutritional substrate malabsorption; hence, preventing gut barrier problems and improving the nutritional status in sepsis is a compelling issue.

AIMS

We tested whether ghrelin administration affects peptide transporter 1 (PepT1) activity in the intestinal epithelium of rats with sepsis.

METHODS

Sixty male Sprague-Dawley rats were randomly divided into sham-operated, sepsis, and ghrelin-treated groups. The cecum of sham-operated rats was separated after laparotomy without ligation and perforation. Sepsis group rats underwent cecal ligation and puncture (CLP). Mucosal specimens were used for immunohistochemstry, real-time PCR, and western blotting to detect PepT1 distribution, and mRNA and protein expression levels, respectively. TNF-α, IL-1β, and ghrelin levels were estimated in serum and intestinal mucosal tissue by ELISA. High-performance liquid chromatography was used to measure PepT1 uptake by the epithelial cells. Moreover, survival, body weight, and food intake of the rats were recorded during the 7-day treatment period.

RESULTS

All rats in the sham-operated group survived, and 80% of rats in the sepsis group died within 7d of CLP. Treatment with ghrelin attenuated the CLP-induced body weight loss, intestine mucosa damage, and the survival rate was better. In addition, ghrelin attenuated increases in TNF-α and IL-1β production. The expressions of PepT1 mRNA and protein were higher in ghrelin-treated group rats than in sepsis rats. Moreover, the uptake function of PepT1 was better in ghrelin-treated group rats.

CONCLUSION

Ghrelin treatment can reduce the inflammatory response and greatly upregulate the physiological function of PepT1 in intestinal epithelial cells of rats with sepsis.

The Role of H. pylori CagA in Regulating Hormones of Functional Dyspepsia Patients

Helicobacter pylori (H. pylori, Hp) colonizes the stomachs of approximately 20%–80% of humans throughout the world. The Word Healthy Organization (WHO) classified H. pylori as a group 1 carcinogenic factor in 1994. Recently, an increasing number of studies has shown an association between H. pylori infection and various extragastric diseases. Functional dyspepsia (FD) is considered a biopsychosocial disorder with multifactorial pathogenesis, and studies have shown that infection with CagA-positive H. pylori strains could explain some of the symptoms of functional dyspepsia. Moreover, CagA-positive H. pylori strains have been shown to affect the secretion of several hormones, including 5-HT, ghrelin, dopamine, and gastrin, and altered levels of these hormones might be the cause of the psychological disorders of functional dyspepsia patients. This review describes the mutual effects of H. pylori and hormones in functional dyspepsia and provides new insight into the pathogenesis of functional dyspepsia.

Chromogranin A and other enteroendocrine markers in inflammatory bowel disease

Changes in the distribution and products of enteroendocrine cells may play a role in immune activation and regulation of gut inflammation. This review aims at critically evaluating the main enteroendocrine markers in inflammatory bowel diseases (IBD). A narrative review was performed by searching inflammatory bowel diseases and enteroendocrine biomarkers in PubMed. Relevant modifications of some enteroendocrine markers, such as Chromogranin A, and their correlation with disease activity have been reported in patients with inflammatory bowel diseases. Even if data about neuroendocrine markers are sometimes contrasting, they may be potentially useful for the diagnosis and clinical management of these patients.

Functional dyspepsia and dyspepsia associated with Helicobacter pylori infection: Do they have different clinical characteristics?

BACKGROUND

Helicobacter pylori causes motor, secretory, and inflammatory gastrointestinal disorders and therefore the term "functional" has been questioned when referring to dyspepsia associated with this bacterium. Patients with dyspepsia and Helicobacter pylori infection could have clinical characteristics that differentiate them a priori from those with true functional dyspepsia.

AIMS

To determine whether there are clinical differences between patients with functional dyspepsia and Helicobacter pylori-associated dyspepsia that enable their a priori identification and to know the prevalence of Helicobacter pylori infection in patients with functional dyspepsia.

PATIENTS AND METHODS

A total of 578 patients with dyspepsia with no significant lesions detectable through endoscopy were divided into 2 groups according to the presence of Helicobacter pylori. The clinical characteristics, medical history, comorbidities, and use of health resources were compared between the two groups. A sub-analysis pairing the groups by age and sex in a 1:1 ratio was carried out to reduce bias.

RESULTS

A total of 336 patients infected with Helicobacter pylori were compared with 242 non-infected patients. The prevalence of infection in the patients with dyspeptic symptoms and no endoscopically detectable lesions was 58%. The initial analysis showed that the cases with dyspepsia and Helicobacter pylori infection were more frequently associated with overweight, obesity, high blood pressure, diabetes mellitus, and metabolic syndrome, but the paired analysis nullified all these differences.

CONCLUSIONS

The patients with dyspepsia infected with Helicobacter pylori had similar clinical characteristics to the non-infected patients and could not be differentiated a priori. The prevalence of Helicobacter pylori infection in patients with functional dyspepsia was 58% and increased with age.

Mechanisms of Electrical Activation and Conduction in the Gastrointestinal System: Lessons from Cardiac Electrophysiology

The gastrointestinal (GI) tract is an electrically excitable organ system containing multiple cell types, which coordinate electrical activity propagating through this tract. Disruption in its normal electrophysiology is observed in a number of GI motility disorders. However, this is not well characterized and the field of GI electrophysiology is much less developed compared to the cardiac field. The aim of this article is to use the established knowledge of cardiac electrophysiology to shed light on the mechanisms of electrical activation and propagation along the GI tract, and how abnormalities in these processes lead to motility disorders and suggest better treatment options based on this improved understanding. In the first part of the article, the ionic contributions to the generation of GI slow wave and the cardiac action potential (AP) are reviewed. Propagation of these electrical signals can be described by the core conductor theory in both systems. However, specifically for the GI tract, the following unique properties are observed: changes in slow wave frequency along its length, periods of quiescence, synchronization in short distances and desynchronization over long distances. These are best described by a coupled oscillator theory. Other differences include the diminished role of gap junctions in mediating this conduction in the GI tract compared to the heart. The electrophysiology of conditions such as gastroesophageal reflux disease and gastroparesis, and functional problems such as irritable bowel syndrome are discussed in detail, with reference to ion channel abnormalities and potential therapeutic targets. A deeper understanding of the molecular basis and physiological mechanisms underlying GI motility disorders will enable the development of better diagnostic and therapeutic tools and the advancement of this field.

Ghrelin and motilin receptors as drug targets for gastrointestinal disorders

The gastrointestinal tract is the major source of the related hormones ghrelin and motilin, which act on structurally similar G protein-coupled receptors. Nevertheless, selective receptor agonists are available. The primary roles of endogenous ghrelin and motilin in the digestive system are to increase appetite or hedonic eating (ghrelin) and initiate phase III of gastric migrating myoelectric complexes (motilin). Ghrelin and motilin also both inhibit nausea. In clinical trials, the motilin receptor agonist camicinal increased gastric emptying, but at lower doses reduced gastroparesis symptoms and improved appetite. Ghrelin receptor agonists have been trialled for the treatment of diabetic gastroparesis because of their ability to increase gastric emptying, but with mixed results; however, relamorelin, a ghrelin agonist, reduced nausea and vomiting in patients with this disorder. Treatment of postoperative ileus with a ghrelin receptor agonist proved unsuccessful. Centrally penetrant ghrelin receptor agonists stimulate defecation in animals and humans, although ghrelin itself does not seem to control colorectal function. Thus, the most promising uses of motilin receptor agonists are the treatment of gastroparesis or conditions with slow gastric emptying, and ghrelin receptor agonists hold potential for the reduction of nausea and vomiting, and the treatment of constipation. Therapeutic, gastrointestinal roles for receptor antagonists or inverse agonists have not been identified.

Ghrelin and Leptin Have a Complex Relationship with Risk of Barrett's Esophagus

BACKGROUND

Abdominal obesity is a risk factor for Barrett's esophagus independent of GERD symptoms, but little is understood about the biological mechanisms between obesity and the carcinogenic pathway of esophageal adenocarcinoma.

AIMS

To evaluate whether ghrelin and leptin may partially explain the association between obesity and Barrett's esophagus.

METHODS

We conducted a case-control study using patients with a new diagnosis of Barrett's esophagus (cases) and two control groups frequency matched to cases for age, gender, and geographic region: (1) patients with gastroesophageal reflux disease (GERD) and (2) a sample of the general population. We generated odds ratios using logistic regressions to evaluate quartiles of serum ghrelin or serum leptin, adjusting for known risk factors for Barrett's esophagus. We evaluated potential interaction variables using cross products and ran stratified analyses to generate stratum-specific odds ratios.

RESULTS

A total of 886 participants were included in the analysis. Higher ghrelin concentrations were associated with an increased risk of Barrett's esophagus, when compared to the population controls, but not the GERD controls. Ghrelin concentrations were not associated with the frequency of GERD symptoms, but ghrelin's relationship with Barrett's esophagus varied significantly with the frequency of GERD symptoms. Leptin concentrations were positively associated with at least weekly GERD symptoms among the population controls and were inversely associated with Barrett's esophagus only among the GERD controls. Adjusting for waist circumference did not change the main associations.

CONCLUSION

Higher levels of ghrelin were associated with an increased risk of Barrett's esophagus among the general population. In contrast, leptin was positively associated with frequent GERD symptoms, but inversely associated with the risk of Barrett's esophagus among the GERD controls.

A possible role for ghrelin, leptin, brain-derived neurotrophic factor and docosahexaenoic acid in reducing the quality of life of coeliac disease patients following a gluten-free diet

PURPOSE

A gluten-free diet (GFD) has been reported to negatively impact the quality of life (QoL) of coeliac disease (CD) patients. The gut-brain axis hormones ghrelin and leptin, with the brain-derived neurotrophic factor (BDNF), may affect QoL of CD patients undergoing GFD. Our aims were to evaluate whether: (a) the circulating concentrations of leptin, ghrelin and BDNF in CD patients were different from those in healthy subjects; (b) GFD might induce changes in their levels; (c) BDNF Val66Met polymorphism variability might affect BDNF levels; and (d) serum BDNF levels were related to dietary docosahexaenoic acid (DHA) as a neurotrophin modulator.

METHODS

Nineteen adult coeliac patients and 21 healthy controls were included. A QoL questionnaire was administered, and serum concentrations of ghrelin, leptin, BDNF and red blood cell membrane DHA levels were determined at the enrolment and after 1 year of GFD. BDNF Val66Met polymorphism was analysed.

RESULTS

Results from the questionnaire indicated a decline in QoL after GFD. Ghrelin and leptin levels were not significantly different between groups. BDNF levels were significantly (p = 0.0213) lower in patients after GFD (22.0 ± 2.4 ng/ml) compared to controls (31.2 ± 2.2 ng/ml) and patients at diagnosis (25.0 ± 2.5 ng/ml). BDNF levels correlated with DHA levels (p = 0.008, r = 0.341) and the questionnaire total score (p = 0.041, r = 0.334).

CONCLUSIONS

Ghrelin and leptin seem to not be associated with changes in QoL of patients undergoing dietetic treatment. In contrast, a link between BDNF reduction and the vulnerability of CD patients to psychological distress could be proposed, with DHA representing a possible intermediate.

Plasma ghrelin and liquid gastric emptying in children with functional dyspepsia consistent with post-prandial distress syndrome

BACKGROUND

Adult studies indicate a role for ghrelin in functional dyspepsia (FD) mediated through ghrelin's effect on gastric emptying (GE). This study examines the relationship between ghrelin, liquid GE, and pain in children with FD.

METHODS

Thirteen FD patients reporting symptoms consistent with post-prandial distress syndrome (PDS) and 17 healthy controls were enrolled. All participants received a liquid meal containing (13) C-sodium acetate. Pain severity, liquid GE utilizing exhaled (13) CO2 from the sodium acetate breath tests (ABT), plasma acyl ghrelin (AG), and des-acyl ghrelin concentrations were measured at specific intervals over 240 min following ingestion.

KEY RESULTS

FD-PDS patients demonstrated lower mean baseline AG (14.8 ± 9.7 vs 27.2 ± 14.0 fmol/mL; p = 0.013), AG Cmax (24.6 ± 8.2 vs 40.5 ± 16.8 fmol/mL; p = 0.007), and AG flux (18.2 ± 7.8 vs 32.7 ± 17.3 fmol/mL; p = 0.015) than controls. The time to reach maximum exhaled (13) CO2 concentration (T max ) was longer in FD patients than controls (47.5 ± 18.5 vs 35.8 ± 11.8 min; p = 0.046). Significant relationships between ghrelin analyte ratios and ABT parameters were largely confined to control participants.

CONCLUSIONS & INFERENCES

FD-PDS in children is associated with lower fasting and maximum AG concentrations, and dampened AG flux. These data suggest a possible role for altered ghrelin physiology in the pathogenesis of PDS.

Ghrelin administration suppresses inflammation-associated colorectal carcinogenesis in mice

Ghrelin is a 28-amino-acid peptide that stimulates the release of pituitary growth hormone. Because of its orexigenic effects, ghrelin is being developed as a therapeutic option for postoperative support and treatment of anorexia-cachexia syndrome of cancer patients. However, ghrelin has a multiplicity of physiological functions, and it also affects cell proliferation. Therefore, the effects of ghrelin administration on carcinogenesis and cancer progression in patients susceptible to cancer should be clarified. In this study, we examined the effects of ghrelin on cancer promotion in vivo using murine intestinal carcinogenesis models. Intestinal tumorigenesis was examined to determine the effects of either exogenous ghrelin administration or ghrelin deficiency following deletion of the Ghrl gene. Two murine intestinal tumorigenesis models were used. The first was the azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced inflammation-associated colon carcinogenesis model and the second was the Apc^Min/+ genetic cancer susceptibility model. In AOM/DSS-treated mice, administration of ghrelin significantly suppressed tumor formation in the colon. In contrast, ghrelin administration did not affect the number of intestinal tumors formed in Apc^Min/+ mice. The absence of endogenous ghrelin did not affect the incidence of intestinal tumors in either AOM/DSS-treated mice or Apc^Min/+ mice, though tumor size tended to be larger in Ghrl^−/− colons in the AOM/DSS model. No tumor-promoting effect was observed by ghrelin administration in either tumorigenesis model. In summary, this study provides in vivo experimental evidence for the usefulness of ghrelin administration in the chemoprevention of inflammation-associated colorectal carcinogenesis and may suggest its safety in patients under colitis-associated cancer susceptibility conditions.

Cancer cachexia, mechanism and treatment

It is estimated that half of all patients with cancer eventually develop a syndrome of cachexia, with anorexia and a progressive loss of adipose tissue and skeletal muscle mass. Cancer cachexia is characterized by systemic inflammation, negative protein and energy balance, and an involuntary loss of lean body mass. It is an insidious syndrome that not only has a dramatic impact on patient quality of life, but also is associated with poor responses to chemotherapy and decreased survival. Cachexia is still largely an underestimated and untreated condition, despite the fact that multiple mechanisms are reported to be involved in its development, with a number of cytokines postulated to play a role in the etiology of the persistent catabolic state. Existing therapies for cachexia, including orexigenic appetite stimulants, focus on palliation of symptoms and reduction of the distress of patients and families rather than prolongation of life. Recent therapies for the cachectic syndrome involve a multidisciplinary approach. Combination therapy with diet modification and/or exercise has been added to novel pharmaceutical agents, such as Megestrol acetate, medroxyprogesterone, ghrelin, omega-3-fatty acid among others. These agents are reported to have improved survival rates as well as quality of life. In this review, we will discuss the emerging understanding of the mechanisms of cancer cachexia, the current treatment options including multidisciplinary combination therapies, as well an update on new and ongoing clinical trials.

Transition of a pancreatic neuroendocrine tumor from ghrelinoma to insulinoma: a case report

Pancreatic neuroendocrine tumors (PNETs) are rare with an incidence of 1 in 100,000 populations. PNETs can present either as a functional or non-functional tumor. In functional tumors the symptoms are a result of hormones such as insulin, gastrin, glucagon and vasoactive intestinal peptide (VIP) or others. Ghrelin is a 28 amino acid peptide discovered in 1999 and is thought to be involved in various physiologic and pathologic processes. Due to relatively recent discovery of this hormone, its functions in normal homeostasis and its association with various pathologic processes are still being uncovered. PNETs are a rare entity and the natural history of disease is not well known. We have presented a first ever case of metastatic PNET which presented as a ghrelinoma and later transformed into a symptomatic insulinoma. This case gives us a glimpse into an unusual variant of metastatic PNET. It also tells us that change in functional tumor biology can sometime be more morbid than the metastatic disease itself.

Growth hormone secretagogue receptor is important in the development of experimental colitis

BACKGROUND

Growth hormone secretagogue receptor (GHSR) and its ligand, ghrelin, are important modulators in weight control and energy homeostasis. Recently, ghrelin is also involved in experimental colitis, but the role of GHSR in the development of colitis is unclear. The aim was to examine the underlying mechanism of GHSR in IBD development.

METHODS

The temporal expression of GHSR/ghrelin was determined in dextran sulphate sodium (DSS) induced colitis in Wt mice. The severity of DSS induced colitis from GHSR(-/-) and WT mice was compared at clinical/pathological levels. Furthermore, the function of macrophages was evaluated in vivo and in vitro.

RESULTS

Lack of GHSR attenuated colitis significantly at the clinical and pathological levels with reduced colonic pro-inflammatory cytokines (P < 0.05). This is consistent with the observation of less colonic macrophage infiltration and TLRs expression from DSS-treated GHSR(-/-) mice compared to WT mice (P < 0.05). Furthermore, there was significantly reduced pro-inflammatory cytokines in LPS-stimulated macrophages in vitro from GHSR(-/-) mice than WT mice (P < 0.05). Moreover, D-lys(3)-GHRP6 (a GHSR antagonist) reduced LPS-induced macrophage pro-inflammatory cytokines from WT mice in vitro.

CONCLUSIONS

GHSR contributes to development of acute DSS-induced colitis, likely via elevated pro-inflammatory cytokines and activation of macrophages. These data suggest GHSR as a potential therapeutic target for IBD.

Ghrelin: ghrelin as a regulatory Peptide in growth hormone secretion

BACKGROUND

Ghrelin is a type of growth hormone (GH) secretagogue that stimulates the release of GH. It is a first hormone linking gastrointestinal-pituitary axis.

OBJECTIVE

This review highlights the interaction of ghrelin with GHRH and somatostatin to regulate the secretion of GH and intends to explore the possible physiological role of the ghrelin-pituitary-GH axis linkage system.

OBSERVATION

Ghrelin is highly conserved among species and is classified into octanoylated (C8:0), decanoylated (C10:0), decenoylated (C10:1) and nonacylated,ghrelin. Acylated ghrelin is the major active form of human ghrelin. The primary production site of ghrelin is the stomach, and it interacts with stomach ghrelin as well as hypothalamic GHRH and somatostatin in the regulation of pituitary GH secretion. Ghrelin stimulate GH release through the GHS receptor to increase intracellular Ca2+ ([Ca2+] levels via IP3 signal transduction pathway. Ghrelin is a specific endogenous ligand for the GHS receptor and provides a definitive proof of the occurance of a GHS-GHS receptor signalling system in the regulation of GH secretion.

CONCLUSION

Studies suggests that ghrelin is a powerful pharmacological agent that exerts a potent, time-dependent stimulation of pulsatile secretion of GH.

Novel therapeutic agents in neurogastroenterology: advances in the past year

BACKGROUND

There have been significant advances in understanding the pathophysiological mechanisms in patients with neurogastroenterological disorders including irritable bowel syndrome (IBS) and functional abdominal pain, functional diarrhea, chronic constipation, gastroparesis, and functional dyspepsia. These advances have led to the development of novel pharmacological therapy of neurogastroenterological disorders.

PURPOSE

To review peer-reviewed articles or prominent preliminary communications presented in the past year regarding medications in development for functional gastrointestinal disorders or gastroparesis. The medications fall into two main categories: first, established classes of medications within established classes, such as 5-HT3 receptor antagonists and 5-HT4 receptor agonists, and second, new classes of medications such as a combined μ-opioid agonist and δ-antagonist, or a small molecule ghrelin agonist.