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

Impacts of Central Administration of the Novel Peptide, LEAP-2, in Different Food Intake Models in Conscious Rats

Liver-expressed antimicrobial peptide-2 (LEAP-2) has mutual antagonism with ghrelin, which evokes food intake under a freely fed state. Nevertheless, the impact of LEAP-2 on ghrelin under time-restricted feeding (TRF), which has benefits in the context of metabolic disease, is still unknown. This study aims to explore the impact of central administration of LEAP-2 on the ingestion behavior of rats, which was evaluated using their cumulative food intake in the TRF state. Before intracerebroventricular (ICV) administration of O-n-octanoylated ghrelin (0.1 nmol/rat), as a food-stimulatory model, the rats received various doses of LEAP-2 (0.3, 1, 3 nmol/rat, ICV). Cumulative food intake was recorded at 1, 2, 4, 8, 12, and 24 h after ICV injection under 12 h freely fed and TRF states in a light phase. In 12 h freely fed and TRF states, central administration of ghrelin alone induced feeding behavior. Pre-treatment with LEAP-2 (1 and 3 nmol/rat, ICV) suppressed ghrelin-induced food intake in a dose-dependent manner in a 12 h freely fed state instead of a TRF state, which may have disturbed the balance of ghrelin and LEAP-2. This study provides neuroendocrine-based evidence that may explain why TRF sometimes fails in fighting obesity/metabolic dysfunction-associated steatotic liver disease in clinics.

Phytomedicine Fructus Aurantii-derived two absorbed compounds unlock antidepressant and prokinetic multi-functions via modulating 5-HT3/GHSR

ETHNOPHARMACOLOGICAL RELEVANCE

Fructus Aurantii (FA), a well-known phytomedicine, has been employed to evoke antidepressant and prokinetic multi-functions. Therein, systematically identifying bioactive components and the referred mechanism is essential for FA.

AIM OF THE STUDY

This study was planned to answer "2 W" (What and Why), such as which components and pathways contribute to FA's multi-functions. We aimed to identify bioactive compounds as the key for opening the lock of FA's multi-functions, and the molecule mechanisms are their naturally matched lock cylinder.

MATERIALS AND METHODS

The phytochemical content of FA extract was determined, and the compounds were identified in rats pretreated with FA using liquid chromatography with mass spectrometry (LC-MS). The contribution strategy was used to assess bioactive compounds' efficacy (doses = their content in FA) in model rats with the mechanism. The changes in functional brain regions were determined via 7.0 T functional magnetic resonance imaging-blood oxygen level-dependent (fMRI-BOLD).

RESULT

Eight phytochemicals' content was detected, and merely six components were identified in rats in vivo. Meranzin hydrate + hesperidin (MH), as the primary contributor of FA, exerted antidepressant and prokinetic effects (improvement of indexes for immobility time, gastric emptying, intestinal transit, CRH, ghrelin, ACTH, DA, NA, 5-HT, CORT, and 5-HT3) by regulating 5-HT3/Growth hormone secretagogue receptor (GHSR) pathway. These results were validated by 5-HT2A, 5-HT3, and GHSR receptor antagonists combined with molecule docking. MH restored the excessive BOLD activation of the left accumbens nucleus, left corpus callosum and hypothalamus preoptic region.

CONCLUSION

Absorbed MH accounts for FA's anti-depressant and prokinetic efficacy in acutely-stressed rats, primarily via 5-HT3/GHSR shared regulation.

Update on Feeding Regulation by Ghrelin in Birds: Focused on Brain Network

Ghrelin is known to be a feeding stimulatory hormone in mammals, but in birds, in contrast to mammals, the feeding behavior is regulated in inhibitory manners. This is because the neuropeptides associated with the regulation in the brain are different from those in mammals, i.e., it has been shown that, in chickens, a corticotropin-releasing hormone family peptide, urocortin, which is a feeding-inhibitory peptide, is mainly involved in the inhibitory mechanism. However, feeding is also regulated by various neurotransmitters in the brain, and recently, their interaction with the mechanisms underlying feeding inhibition by ghrelin in birds has been intensively studied and clarified. This review summarizes these findings.

Genome-Wide Association and Two-Sample Mendelian Randomization Analyses of Plasma Ghrelin and Gastrointestinal Cancer Risk

BACKGROUND

Observational studies have suggested that the gut hormone ghrelin is an early marker of future risk of developing gastrointestinal cancer. However, whether ghrelin is a causal risk factor remains unclear. We conducted a genome-wide association study (GWAS) of plasma ghrelin and used Mendelian randomization (MR) to investigate the possible causal association between ghrelin and gastrointestinal cancer risk.

METHODS

Genetic variants associated with plasma ghrelin were identified in a GWAS comprising 10,742 Swedish adults in the discovery (N = 6,259) and replication (N = 4,483) cohorts. The association between ghrelin and gastrointestinal cancer was examined through a two-sample MR analysis using the identified genetic variants as instruments and GWAS data from the UK Biobank, FinnGen, and a colorectal cancer consortium.

RESULTS

GWAS found associations between multiple genetic variants within ±200 kb of the GHRL gene and plasma ghrelin. A two-sample MR analysis revealed that genetically predicted higher plasma ghrelin levels were associated with a lower risk of gastrointestinal cancer in UK Biobank and in a meta-analysis of the UK Biobank and FinnGen studies. The combined OR per approximate doubling of genetically predicted plasma ghrelin was 0.91 (95% confidence interval, 0.85-0.99; P = 0.02). Colocalization analysis revealed limited evidence of shared causal variants for plasma ghrelin and gastrointestinal cancer at the GHRL locus (posterior probability H4 = 24.5%); however, this analysis was likely underpowered.

CONCLUSIONS

Our study provides evidence in support of a possible causal association between higher plasma ghrelin levels and a reduced risk of gastrointestinal cancer.

IMPACT

Elevated plasma ghrelin levels might reduce the risk of gastrointestinal cancer.

Sleep Deprivation and Gut Microbiota Dysbiosis: Current Understandings and Implications

Gut microbiota comprises the microbial communities inhabiting our gastrointestinal (GI) tracts. Accordingly, these complex communities play a fundamental role in many host processes and are closely implicated in human health and diseases. Sleep deprivation (SD) has become increasingly common in modern society, partly owing to the rising pressure of work and the diversification of entertainment. It is well documented that sleep loss is a significant cause of various adverse outcomes on human health including immune-related and metabolic diseases. Furthermore, accumulating evidence suggests that gut microbiota dysbiosis is associated with these SD-induced human diseases. In this review, we summarize the gut microbiota dysbiosis caused by SD and the succedent diseases ranging from the immune system and metabolic system to various organs and highlight the critical roles of gut microbiota in these diseases. The implications and possible strategies to alleviate SD-related human diseases are also provided.

Leu72Met Polymorphism in Ghrelin Gene: A Potential Risk Factor for Hypertension in Type 2 Diabetes Patients

OBJECTIVE

Ghrelin (GHRL) is known to be engaged in metabolic and cardiovascular processes. There is evidence suggesting its involvement in the regulation of blood pressure and hypertension. The purpose of this preliminary case-control study was to determine the involvement of the Leu72Met (rs696217) polymorphism in the GHRL gene in type 2 diabetes (T2DM).

METHODS

The Leu72Met polymorphism was genotyped in 820 individuals with T2DM and 400 healthy subjects by the PCR-RFLP technique. The polymorphism distribution was first compared in those withT2DM and controls, then in subgroups of participants representing different clinical phenotypes.

RESULTS

No significant association was identified between Leu72Met and T2DM. The distribution of polymorphism was analyzed in subgroups of individuals with different clinical phenotypes (hypertension, diabetic nephropathy, obesity). In this analysis, rs696217 was associated with hypertension. The presence of T allele was associated with higher risk of hypertension (OR = 2.50, 95% CI 1.68-3.73, p < 0.001). When adjusted for age, gender and BMI, the association was still significant (OR = 2.62, 95% CI 1.83-3.96, p < 0.001). A post hoc power calculations based on a minor allele frequency revealed the power of 97% for comparison between HY+ and HY- subgroups.

CONCLUSION

This is the first study demonstrating that the ghrelin Leu72Met SNP is associated with hypertension in Caucasians with T2DM. If confirmed in larger studies in different populations, it may be a novel potential risk factor for hypertension in individuals withT2DM.

Impact of Metabolic Surgery on Gut Microbiota and Sera Metabolomic Patterns among Patients with Diabetes

Metabolic surgery is a promising treatment for obese individuals with type 2 diabetes mellitus (T2DM), but the mechanism is not completely understood. Current understanding of the underlying ameliorative mechanisms relies on alterations in parameters related to the gastrointestinal hormones, biochemistry, energy absorption, the relative composition of the gut microbiota, and sera metabolites. A total of 13 patients with obesity and T2DM undergoing metabolic surgery treatments were recruited. Systematic changes of critical parameters and the effects and markers after metabolic surgery, in a longitudinal manner (before surgery and three, twelve, and twenty-four months after surgery) were measured. The metabolomics pattern, gut microbiota composition, together with the hormonal and biochemical characterizations, were analyzed. Body weight, body mass index, total cholesterol, triglyceride, fasting glucose level, C-peptide, HbA1c, HOMA-IR, gamma-glutamyltransferase, and des-acyl ghrelin were significantly reduced two years after metabolic surgery. These were closely associated with the changes of sera metabolomics and gut microbiota. Significant negative associations were found between the Eubacterium eligens group and lacosamide glucuronide, UDP-L-arabinose, lanceotoxin A, pipercyclobutanamide B, and hordatine B. Negative associations were identified between Ruminococcaceae UCG-003 and orotidine, and glucose. A positive correlation was found between Enterococcus and glutamic acid, and vindoline. Metabolic surgery showed positive effects on the amelioration of diabetes and metabolic syndromes, which were closely associated with the change of sera metabolomics, the gut microbiota, and other disease-related parameters.

The Efficacy, Safety, and Pharmacology of a Ghrelin O-Acyltransferase Inhibitor for the Treatment of Prader-Willi Syndrome

CONTEXT

Acylated ghrelin (AG) stimulates appetite and is elevated compared to its unacylated (UAG) counterpart in Prader-Willi syndrome (PWS). GLWL-01 is a selective, reversible inhibitor of ghrelin O-acyltransferase (GOAT), the enzyme that converts UAG into AG.

OBJECTIVE

This work aimed to assess the efficacy, pharmacokinetics, pharmacodynamics, and safety of GLWL-01 in the treatment of PWS patients.

METHODS

A double-blind, placebo-controlled, phase 2 crossover study was conducted with 2 active treatment periods of 28 days in 19 patients (aged 16-65 years; body mass index (BMI) ≥ 28) with genetically confirmed PWS. The study took place in 7 hospital-based study centers in the United States and Canada. Patients received placebo or GLWL-01 (450 mg twice daily) orally after lead-in placebo and washout periods. The Hyperphagia Questionnaire for Clinical Trials and Caregiver Global Impression of Change were used to measure reductions in hyperphagia. Plasma concentrations of AG and UAG were evaluated as correlates.

RESULTS

Treatment resulted in statistically significant differences compared to placebo in plasma AG (P = .0002), UAG (P = .0488), and AG/UAG (P = .0003). GLWL-01 did not statistically significantly reduce hyperphagia-related behavior or bring about changes in global clinical end points, as assessed by caregivers. Anthropometric and clinical parameters correlated with obesity did not statistically significantly change in response to treatment. Less than half of patients reported a treatment-emergent adverse event (TEAE). No deaths, serious adverse events, or severe TEAEs were reported.

CONCLUSION

GLWL-01 is safe and well tolerated. Pharmacological parameters confirmed the inhibition of GOAT following administration of GLWL-01. Patients' eating behaviors, BMI, blood glucose, and total cholesterol, among other similar measures, were not modified.

MetNC: Predicting Metabolites in vivo for Natural Compounds

Natural compounds (NCs) undergo complicated biotransformation in vivo to produce diverse forms of metabolites dynamically, many of which are of high medicinal value. Predicting the profiles of chemical products may help to narrow down possible candidates, yet current computational methods for predicting biotransformation largely focus on synthetic compounds. Here, we proposed a method of MetNC, a tailor-made method for NC biotransformation prediction, after exploring the overall patterns of NC in vivo metabolism. Based on 850 pairs of the biotransformation dataset validated by comprehensive in vivo experiments with sourcing compounds from medicinal plants, MetNC was designed to produce a list of potential metabolites through simulating in vivo biotransformation and then prioritize true metabolites into the top list according to the functional groups in compound structures and steric hindrance around the reaction sites. Among the well-known peers of GLORYx and BioTransformer, MetNC gave the highest performance in both the metabolite coverage and the ability to short-list true products. More importantly, MetNC seemed to display an extra advantage in recommending the microbiota-transformed metabolites, suggesting its potential usefulness in the overall metabolism estimation. In summary, complemented to those techniques focusing on synthetic compounds, MetNC may help to fill the gap of natural compound metabolism and narrow down those products likely to be identified in vivo.

Prospective Evaluation of Ghrelin and Des-Acyl Ghrelin Plasma Levels in Children with Newly Diagnosed Epilepsy: Evidence for Reduced Ghrelin-to-Des-Acyl Ghrelin Ratio in Generalized Epilepsies

Children with epilepsy and identified as responders to antiseizure medications (ASMs) were found to present markedly higher ghrelin plasma levels when compared to drug-resistant patients. However, it was undetermined if this phenotype could be influenced by the ASMs. Here, we prospectively investigated total ghrelin and des-acyl ghrelin (DAG) plasma levels by enzyme-linked immunosorbent assay before and after ASM administration. Inclusion criteria were: (i) subject with a suspicion of epilepsy; (ii) age ranging from 0 to 16 years; and (iii) informed consent signed by parents or caregivers. Exclusion criteria were acute or chronic metabolic disorders with occasional convulsions but without epilepsy. Fifty patients were followed over a period of one year in Italian neuropediatric centers. Apart from a few exceptions, the majority of children were responsive to ASMs. No differences were found in total ghrelin and DAG levels before and after the treatment, but total ghrelin levels were significantly lower in children with generalized epilepsy compared to those with combined focal and generalized epilepsy. Moreover, the ghrelin-to-DAG ratio was also markedly lower in generalized epilepsies compared to all the other types of epilepsy. Finally, ghrelin was unchanged by ASMs, including the first (e.g., carbamazepine), second (levetiracetam), and third (lacosamide) generation of anticonvulsants.

Ghrelin mediated regulation of neurosynaptic transmitters in depressive disorders

Ghrelin is a peptide released by the endocrine cells of the stomach and the neurons in the arcuate nucleus of the hypothalamus. It modulates both peripheral and central functions. Although ghrelin has emerged as a potent stimulator of growth hormone release and as an orexigenic neuropeptide, the wealth of literature suggests its involvement in the pathophysiology of affective disorders including depression. Ghrelin exhibits a dual role through the advancement and reduction of depressive behavior with nervousness in the experimental animals. It modulates depression-related signals by forming neuronal networks with various neuropeptides and classical neurotransmitter systems. The present review emphasizes the integration and signaling of ghrelin with other neuromodulatory systems concerning depressive disorders. The role of ghrelin in the regulation of neurosynaptic transmission and depressive illnesses implies that the ghrelin system modulation can yield promising antidepressive therapies.

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Ghrelin is the orexigenic type of neuropeptide.

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It binds with the growth hormone secretagogue receptor (GHSR).

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GHSR is ubiquitously present in the various brain regions.

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Ghrelin is involved in the regulation of depression-related behavior.

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The review focuses on the neurotransmission and signaling of ghrelin in neuropsychiatric and depressive disorders.

Ghrelin octanoylation by ghrelin O-acyltransferase: protein acylation impacting metabolic and neuroendocrine signalling

The acylated peptide hormone ghrelin impacts a wide range of physiological processes but is most well known for controlling hunger and metabolic regulation. Ghrelin requires a unique posttranslational modification, serine octanoylation, to bind and activate signalling through its cognate GHS-R1a receptor. Ghrelin acylation is catalysed by ghrelin O-acyltransferase (GOAT), a member of the membrane-bound O-acyltransferase (MBOAT) enzyme family. The ghrelin/GOAT/GHS-R1a system is defined by multiple unique aspects within both protein biochemistry and endocrinology. Ghrelin serves as the only substrate for GOAT within the human proteome and, among the multiple hormones involved in energy homeostasis and metabolism such as insulin and leptin, acts as the only known hormone in circulation that directly stimulates appetite and hunger signalling. Advances in GOAT enzymology, structural modelling and inhibitor development have revolutionized our understanding of this enzyme and offered new tools for investigating ghrelin signalling at the molecular and organismal levels. In this review, we briefly summarize the current state of knowledge regarding ghrelin signalling and ghrelin/GOAT enzymology, discuss the GOAT structural model in the context of recently reported MBOAT enzyme superfamily member structures, and highlight the growing complement of GOAT inhibitors that offer options for both ghrelin signalling studies and therapeutic applications.

Ghrelin attenuates drowning injury via dual effects on damage protection and immune repression

Background

Seawater drowning is the major cause of accidental injury and death. The current treatment could not essentially block the source of the damage due to the complex etiology. Therefore, it is urgent to clarify the detailed mechanisms and find effective therapeutic approaches.

Methods

We performed in vitro experiments to evaluate the damage of seawater drowning to lung epithelial cells. FACS, immunofluorescent staining, and western blot were used to detect the apoptosis. CCK-8 assay, Ki67 staining, and cell cycle analysis were used to assess the proliferation. The cytokine expression was determined by qRT-PCR and ELISA. Western blot and reporter assay were used for regulation mechanism study. For neutrophils development, Transwell assay and FACS were used for further investigation. Besides, in vivo study was performed with the seawater drowning model in rats.

Results

In this study, we found that seawater drowning induced mitochondria damage, which further accelerated epithelial cell apoptosis and repressed cell proliferation. Administration of ghrelin attenuated the mitochondria damage via reducing ROS generation, decreasing the concentration of calcium ion and ceremide, and promoting ATP production. Besides, exogenous ghrelin also rescued the cell survival inhibited by seawater simulants. Mechanically, ghrelin retrieved the influence of seawater via inhibiting NF-κB signaling activation, and agonist of NF-κB could offset the function of ghrelin. Besides, ghrelin reduced the expression of inflammatory factors and chemokines responsible for neutrophils activation and recruitment, by which ghrelin suppressed the immune response. The further in vivo experiments also indicated that ghrelin treatment restored the apoptosis promotion and inflammation activation function of seawater simulants, and further alleviated the lung tissue injury.

Conclusions

Our study revealed the dual effect of ghrelin on seawater drowning induced lung injury via damage protection and immune repression, providing new insights into drowning injury pathogenesis and therapeutic strategies.

Gastrointestinal Motility and Gut Hormone Secretion in response to Shenhuang Plaster in a Postoperative Ileus Rat Model

Postoperative ileus (POI), a gastrointestinal function disorder, is a complication that arises from surgery. Shenhuang plaster (SHP) application to the Shenque acupoint (CV8) to promote the recovery of gastrointestinal function has achieved definite curative effects in clinical settings; however, the underlying pharmacological mechanism remains unknown. In this study, we evaluated the effects of SHP using a Sprague Dawley rat POI model. Then, gastrointestinal transit in different rat groups was evaluated by the movement of fluorescein-labelled dextran. Ghrelin, obestatin, motilin (MTL), and vasoactive intestinal peptide (VIP) plasma concentrations were measured via a radioimmunoassay. The expression of the ghrelin and obestatin receptors (GHS-R1α and GPR39) in the intestinal muscularis of rats in different groups was comparatively identified via western blotting. The results indicated that SHP application improved gastrointestinal motility in POI model rats. SHP application significantly increased ghrelin concentration and the expression of its receptor and inhibited obestatin concentration and the expression of its receptor in blood. Further, ghrelin concentration and the capability of gastrointestinal transit were positively correlated. Simultaneously, SHP application also promoted the secretion of other gastrointestinal motility hormones, such as MTL and VIP. Hence, these results provide evidence that SHP can promote the recovery of gastrointestinal transmission in POI rat models through regulation of ghrelin and other intestinal hormones.

Role of the Endocannabinoid System in the Adipose Tissue with Focus on Energy Metabolism

The endocannabinoid system is involved in a wide range of processes including the control of energy acquisition and expenditure. Endocannabinoids and their receptors are present in the central nervous system but also in peripheral tissues, notably the adipose tissues. The endocannabinoid system interacts with two main hormones regulating appetite, namely leptin and ghrelin. The inhibitory effect of the cannabinoid receptor 1 (CB₁) antagonist rimonabant on fat mass suggested that the endocannabinoid system can also have a peripheral action in addition to its effect on appetite reduction. Thus, several investigations have focused on the peripheral role of the endocannabinoid system in the regulation of metabolism. The white adipose tissue stores energy as triglycerides while the brown adipose tissue helps to dissipate energy as heat. The endocannabinoid system regulates several functions of the adipose tissues to favor energy accumulation. In this review we will describe the presence of the endocannabinoid system in the adipose tissue. We will survey the role of the endocannabinoid system in the regulation of white and brown adipose tissue metabolism and how the eCB system participates in obesity and metabolic diseases.

Bile Acids: Key Regulators and Novel Treatment Targets for Type 2 Diabetes

Type 2 diabetes mellitus (T2DM), characterized by insulin resistance and unclear pathogenesis, is a serious menace to human health. Bile acids are the end products of cholesterol catabolism and play an important role in maintaining cholesterol homeostasis. Furthermore, increasing studies suggest that bile acids may regulate glucose tolerance, insulin sensitivity, and energy metabolism, suggesting that bile acids may represent a potential therapeutic target for T2DM. This study summarizes the metabolism of bile acids and, more importantly, changes in their concentrations, constitution, and receptors in diabetes. Furthermore, we provide an overview of the mechanisms underlying the role of bile acids in glucose and lipid metabolism, as well as the occurrence and development of T2DM. Bile acid-targeted therapy may represent a valid approach for T2DM treatment.

Variation analysis of Ghrelin gene in Chinese patients with obesity, having polycystic ovarian syndrome

Association of single-nucleotide polymorphisms (SNPs) of the ghrelin gene with polycystic ovary syndrome (PCOS)is unclear. However, their correlation with PCOS-related obesity has been observed. The objective of this study was to evaluate the effects of ghrelin gene SNPs on PCOS-related obesity in Chinese women. The full-length sequence of the ghrelin gene was determined to explore the relationship of the SNPs with PCOS-related obesity in Chinese women. The gene was sequenced, including all exons, introns and exon-intron boundaries in 230 Han Chinese women with PCOS and 162 normal women. Significant genotypic and allelic differences were observed between the obese PCOS group and obese control group at rs35681 locus (p = .013 and .017). The genotypic analysis of obese and non-obese people in the PCOS group showed that the proportion of A allele in the obese PCOS group (10.9%) was higher than that of the G allele (3.6%). This study revealed that ghrelin rs35681 might be related to the occurrence of obesity associated with PCOS, and allele A was found to increase the risk of obesity in PCOS.

Hexarelin targets neuroinflammatory pathways to preserve cardiac morphology and function in a mouse model of myocardial ischemia-reperfusion

Acute myocardial ischemia and reperfusion injury (IRI) underly the detrimental effects of coronary heart disease on the myocardium. Despite the ongoing advances in reperfusion therapies, there remains a lack of effective therapeutic strategies for preventing IRI. Growth hormone secretagogues (GHS) have been demonstrated to improve cardiac function, attenuate inflammation and modulate the autonomic nervous system (ANS) in models of cardiovascular disease. Recently, we demonstrated a reduction in infarct size after administration of hexarelin (HEX), in a murine model of myocardial infarction. In the present study we employed a reperfused ischemic (IR) model, to determine whether HEX would continue to have a cardioprotective influence in a model of higher clinical relevance. Myocardial ischemia was induced by transient ligation of the left descending coronary artery (tLAD) in C57BL/6 J mice followed by HEX (0.3 mg/kg/day; n = 20) or vehicle (VEH) (n = 18) administration for 21 days, first administered immediately prior-to reperfusion. IR-injured and sham mice were subjected to high-field magnetic resonance imaging to assess left ventricular (LV) function, with HEX-treated mice demonstrating a significant improvement in LV function compared with VEH-treated mice. A significant decrease in interstitial collagen, TGF-β1 expression and myofibroblast differentiation was also seen in the HEX-treated mice after 21 days. HEX treatment shifted the ANS balance towards a parasympathetic predominance; combined with a significant decrease in cardiac troponin-I and TNF-α levels, these findings were suggestive of an anti-inflammatory action on the myocardium mediated via HEX. In this model of IR, HEX appeared to rebalance the deregulated ANS and activate vagal anti-inflammatory pathways to prevent adverse remodelling and LV dysfunction. There are limited interventions focusing on IRI that have been successful in improving clinical outcome in acute myocardial infarction (AMI) patients, this study provides compelling evidence towards the translational potential of HEX where all others have largely failed.

Expression of ghrelin and leptin in the chemosensory system of adult zebrafish

Numerous data show that the chemosensory system seems to be modulated by changes in the circulating levels of different molecules such as ghrelin, orexin, leptin, NPY, CCK. The chemosensory system of the zebrafish is represented by the taste buds (skin, oral and oropharyngeal), the olfactory rosette and the solitary chemosensorial cells (SCCs). The purpose of our study was to analyze the distribution of two peripheral hormones such as ghrelin and leptin in the chemosensory organs of the zebrafish. Our results demonstrated the presence of immunoreaction for all antibodies used in the zebrafish chemosensory organs even if with different distribution. In particular, IR was observed for ghrelin in the olfactory rosette while IR for leptin was found in the olfactory rosette, in the skin and oropharyngeal taste buds and in the gills. Both these hormones were detected in the intestine, used as a control.

Dose-dependent effects of two inulin types differing in chain length on the small intestinal morphology, contractility and proinflammatory cytokine gene expression in piglets

Inulin is a linear fructose polymer which may affect small intestinal physiology. The effects of dietary level of two inulin types on morphology, contractility and proinflammatory cytokine gene expression in the small intestine of piglets were investigated. Fifty six piglets were divided into seven groups fed diets without inulin addition or with 1%, 2% or 3% of inulin with an average degree of polymerisation of 10 (IN10) or 23 (IN23). All diets were offered from day 10 of life for 40 d. Feeding IN10 diets did not affect villous height to crypt depth ratio in the duodenum, while in the jejunum the 2% IN10 diet increased it as compared to other groups. Jejunal muscle contractions induced by electrical field stimulation were impaired by the 2% and 3% IN10 diets. The ileal expression of interleukin-12p40 was decreased by the 2% IN10 diet. There was no effect of IN23 level on villous height to crypt depth ratio in any segment of the small intestine as well as on jejunal motility. The 2% and 3% IN23 diets decreased the jejunal expression of tumour necrosis factor-α. In conclusion, IN10 is more active in the small intestine than IN23. At the 2% dietary level, it increases absorptive area in the jejunum, but may slightly impair smooth muscle contractions.

Modulatory effects of ghrelin on sperm quality alterations induced by a fructose-enriched diet

The objectives of this study were: 1) to evaluate the effects of a fructose enriched diet (FED) on rat sperm quality, epididymal function (i.e. oxidative stress and alpha-glucosidase expression) and testosterone concentrations; 2) to determine if the administration of ghrelin (Ghrl), reverses the effects induced by FED. After validating the protocol as an inductor of metabolic syndrome like-symptoms, adult male rats were assigned to one of the following treatments for 8 weeks: FED = 10% fructose enriched in water (v/v); FED + Ghrl = fructose enriched diet plus Ghrl (6 nmol/animal/day, s.c.) from week 6-8; or C = water without fructose (n = 5-10 animals/group). FED significantly decreased sperm concentration and motile sperm count/ml vs C (FED: 19.0 ± 1.6 × 10⁶sperm/ml and 834.6 ± 137.0, respectively vs C: 25.8 ± 2.8 × 10⁶ and 1300.4 ± 202.4, respectively; p < 0.05); ghrelin injection reversed this negative effect (23.5 ± 1.6 × 10⁶sperm/ml and 1381.7 ± 71.3 respectively). FED resulted in hypogonadism, but Ghrl could not normalize testosterone concentrations (C: 1.4 ± 0.1 ng/ml vs FED: 0.8 ± 0.2 ng/ml and FED + Ghrl: 0.6 ± 0.2 ng/ml; p < 0.05). Ghrelin did not reverse metabolic abnormalities secondary to FED. FED did not alter epididymal expression of antioxidants enzymes (superoxido-dismutase, catalase and glutathione peroxidases -Gpx-). Nevertheless, FED + Ghrl significantly increased the expression of Gpx3 (FED + Ghrl: 3.47 ± 0.48 vs FED: 0.69 ± 0.28 and C: 1.00 ± 0.14; p < 0.05). The expression of neutral alpha-glucosidase, which is a marker of epididymal function, did not differ between treatments. In conclusion, the administration of Ghrl modulated the negative effects of FED on sperm quality, possibly by an epididymal increase in Gpx3 expression. However, Ghrl could not neither normalize the metabolism of FED animals, nor reverse hypogonadism.

Ghrelin improves muscle function in dystrophin-deficient mdx mice by inhibiting NLRP3 inflammasome activation

AIMS

Immuno-inflammation contributes to the pathogenesis of Duchenne muscular dystrophy (DMD), characterized by progressive muscle degeneration and weakness. The nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is crucial for initiating innate immunity. Ghrelin is a circulating hormone that exerts anti-inflammatory activity in several inflammatory diseases. However, the role of ghrelin in DMD and underlying mechanism are still unstated. Therefore, we investigated the effect and potential mechanism of ghrelin on muscle morphology and muscular function of mdx mice, a mouse model of DMD.

MAIN METHODS

4-Week-old male mdx mice were injected intraperitoneally with ghrelin (100 μg/kg of body weight/day) or saline for 4 weeks. Then, muscle performance was evaluated by behavioral tests. Skeletal muscles samples were collected and relevant parameters were measured by using histopathological analysis and molecular biology techniques both in mdx muscles and primary myoblasts.

KEY FINDINGS

Ghrelin significantly improved motor performance, alleviated muscle pathology and decreased inflammatory cell infiltration in mdx mice. Importantly, ghrelin dramatically inhibited NLRP3 inflammasome activation and reduced the production of mature IL-1β both in dystrophic muscles and in lipopolysaccharide (LPS)-primed primary myoblasts induced by the NLRP3 inflammasome activator benzylated ATP (BzATP). Furthermore, the inhibition of NLRP3 inflammasome by ghrelin was partly mediated by the suppression of JAK2-STAT3 and p38 MAPK signaling pathway.

SIGNIFICANCE

Our findings reveal that ghrelin suppresses muscle inflammation and ameliorates disease phenotype through inhibition of NLRP3 inflammasome activation and the production of IL-1β in mdx mice, which suggests new therapeutic potential of ghrelin in DMD.

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.

GHRL Gene Leu72Met Polymorphism and Type 2 Diabetes Mellitus: A Meta-Analysis Involving 8,194 Participants

Background: Although many studies indicate a positive correlation between GHRL gene Leu72Met polymorphism and an increased susceptibility to type 2 diabetes mellitus (T2DM), inconsistencies between independent studies still remain. Objective: Considering the inconsistencies between them, we have performed the current meta-analysis study. The objective of this study is to better examine the correlation of the GHRL gene Leu72Met polymorphism and T2DM. Methods: The current meta-analysis, involving 8,194 participants from 11 independent studies, was performed. A fixed effect model was used to evaluate the pooled odds ratios (ORs) and the corresponding 95% confidence intervals (95% CIs). Results: A significant association was found between T2DM and GHRL gene Leu72Met polymorphism under recessive (OR: 1.33, 95% CI: 1.01-1.76, P = 0.04), and homozygous genetic models (OR: 1.34, 95% CI: 1.01-1.78, P = 0.04) in the whole population. The correlation was more distinct in our subgroup analysis of the Chinese population under recessive (OR: 1.52, 95% CI: 1.07-2.15, P = 0.02), dominant (OR: 1.70, 95% CI: 1.38-2.10, P < 0.00001), additive (OR: 1.16, 95% CI: 1.02-1.33, P = 0.02), and homozygous genetic models (OR: 1.54, 95% CI: 1.07-2.20, P = 0.02). Conclusions: In short, GHRL gene Leu72Met polymorphism was significantly correlated with increased T2DM risk, particularly in the Chinese population. Individuals carrying the Met72 allele of GHRL Leu72Met gene polymorphism, particularly those of Chinese ancestry, may be more susceptible to developing T2DM disease.

Regulation of Gastrointestinal Motility by Motilin and Ghrelin in Vertebrates

The energy balance of vertebrates is regulated by the difference in energy input and energy expenditure. Generally, most vertebrates obtain their energy from nutrients of foods through the gastrointestinal (GI) tract. Therefore, food intake and following food digestion, including motility of the GI tract, secretion and absorption, are crucial physiological events for energy homeostasis. GI motility changes depending on feeding, and GI motility is divided into fasting (interdigestive) and postprandial (digestive) contraction patterns. GI motility is controlled by contractility of smooth muscles of the GI tract, extrinsic and intrinsic neurons (motor and sensory) and some hormones. In mammals, ghrelin (GHRL) and motilin (MLN) stimulate appetite and GI motility and contribute to the regulation of energy homeostasis. GHRL and MLN are produced in the mucosal layer of the stomach and upper small intestine, respectively. GHRL is a multifunctional peptide and is involved in glucose metabolism, endocrine/exocrine functions and cardiovascular and reproductive functions, in addition to feeding and GI motility in mammals. On the other hand, the action of MLN is restricted and species such as rodentia, including mice and rats, lack MLN peptide and its receptor. From a phylogenetic point of view, GHRL and its receptor GHS-R1a have been identified in various vertebrates, and their structural features and various physiological functions have been revealed. On the other hand, MLN or MLN-like peptide (MLN-LP) and its receptors have been found only in some fish, birds and mammals. Here, we review the actions of GHRL and MLN with a focus on contractility of the GI tract of species from fish to mammals.

Effects of burns on gut motor and mucosa functions

This review analyzed the published studies on the effects of thermal injury on gastrointestinal motility and mucosal damage. Our strategy was to integrate all available evidence to provide a complete review on the prokinetic properties of variable reagents and the potential clinical treatment of mucosal damage and gastrointestinal dysmotility after thermal injury. We classified the studies into two major groups: studies on gastrointestinal dysmotility and studies on mucosal damage. We also subclassified the studies into 3 parts: stomach, small intestine, and colon. This review shows evidence that ghrelin can recover burn-induced delay in gastric emptying and small intestinal transit, and can protect the gastric mucosa from burn-induced injury. Oxytocin and β-glucan reduced the serum inflammatory mediators, and histological change and mucosal damage indicators, but did not show evidence of having the ability to recover gastrointestinal motility. Using a combination of different reagents to protect the gastrointestinal mucosa against damage and to recover gastrointestinal motility is an alternative treatment for thermal injury.

Prevalence and Factors Associated with Helicobacter Pylori in Patients Undergoing Bariatric Surgery: the SOON Cohort

PURPOSE

Helicobacter Pylori (HP) infection is systematically screened for before carrying out bariatric surgery. Criteria to determine "at risk" patients and avoid systematic screening are lacking. We evaluated the prevalence of HP infection and associated predictive factors in a population of patients with class II and III obesity volunteering for bariatric surgery.

MATERIALS AND METHODS

Observational, cross-sectional study of patients included in the severe obesity outcome network (SOON) cohort. All patients underwent HP screening. The relationship between plasma metabolic parameters and vitamin levels, medical history and socio-economic parameters, and HP infection was analyzed.

RESULTS

Data from 201 patients, median age 43 years [IQR 35; 52] (81% female) were analyzed. Forty-four patients (22%) were infected with HP and successfully treated, most with a single course of treatment, either combined antibiotics or Pylera®. HP infection was associated with social precariousness as defined by the French "Evaluation de la Précarité et des Inégalités de santé dans les Centres d'Examens de Santé" (EPICES) score (Evaluation of Poverty and Health Inequalities in Health-Assessment Centers) (OR, 1.027; 95% CI, 1.008-1.046; p < 0.004) and with higher levels of vitamin B₁₂ (OR, 1.004; 95% CI, 1.001-1.007; p < 0.007).

CONCLUSION

The prevalence of HP infection was 22% and was associated with social precariousness. Plasma glucose/insulin and lipid/lipoprotein profiles, liver enzymes or vitamin deficiencies were not associated with HP infection. The number of characteristics associated with HP infection was insufficient to define patients who do not require HP screening before bariatric surgery.

Ghrelin and acyl ghrelin levels are associated with inflammatory and nutritional markers and with cardiac and vascular dysfunction parameters in hemodialysis patients

PURPOSE

Exogenous ghrelin is associated with cardiovascular protection in experimental and human studies. Nevertheless ESRD patients have increased ghrelin levels and severe cardiovascular comorbidities. This study aims to elucidate the metabolic factors influencing endogenous ghrelin/acyl ghrelin levels and to analyze the relation between endogenous ghrelin/acyl ghrelin levels and cardiac and vascular function markers in hemodialysis patients.

METHODS

The cross-sectional study was conducted in hemodialysis patients (n = 88); 50 of them were men, mean age 61.1 ± 13.5 years, 17% had diabetes. We assessed nutritional and inflammatory status and analyzed the determinants of ghrelin/acyl ghrelin and their relation with cardiac and vascular function.

RESULTS

Ghrelin is correlated with IL-1β (r = 0.88, p < 0.0001), triglycerides, total cholesterol (TC), and Kt/V. IL-1β is the strongest predictor of ghrelin levels (p < 0.0001). Acyl ghrelin is correlated with TC (r = 0.36, p = 0.001), LDL-cholesterol, serum bicarbonate, body mass index. TC is the strongest predictor for acyl ghrelin levels (p = 0.038). Patients with high ghrelin levels had significantly decreased nitroglycerin-mediated dilation (p = 0.05) and higher IL-1β levels (p < 0.001); increased NT-proBNP is associated with lower levels of acyl ghrelin (r = - 0.33, p = 0.02) in male patients.

CONCLUSION

The inflammatory marker IL-1β is in our study the strongest predictor of ghrelin levels while the nutritional marker-total cholesterol is the strongest predictor for acyl ghrelin levels in HD patients. High endogenous ghrelin level is associated with high IL-1β and with vascular smooth muscle cell dysfunction. Low acyl ghrelin level is associated with high NT-proBNP (a cardiac dysfunction marker) in male HD patients. There is a direct correlation between endogenous ghrelin level and inflammatory markers, which is not related with cardiovascular protection.

Serum Levels of Angiopoietin-Like Protein 2 and Obestatin in Iranian Women with Polycystic Ovary Syndrome and Normal Body Mass Index

Background: Polycystic ovary syndrome (PCOS) is a common endocrine disease in women of reproduction age and a major cause of anovulatory infertility. Insulin resistance plays an important role in the development and durability of this disorder. ANGPTL2 is known as an inflammatory mediator derived from adipose tissue that links obesity to systemic insulin resistance, and obestatin has been identified as a hormone associated with insulin resistance that suppresses food reabsorption, inhibits gastric emptying and decreases weight gain. The aim of this study was to evaluate serum levels of ANGPTL2 and obestatin in PCOS women with normal body mass index (BMI). Methods: In this case-control study, 26 PCOS women based on the Rotterdam 2003 diagnostic criteria as the case group and 26 women with normal menstrual cycles as the control group were enrolled. Serum levels of ANGPTL2, obestatin, insulin and other hormone factors related with PCOS were measured by ELISA method and biochemical parameters were measured by an autoanalyzer. Data were analyzed by independent samples-T test, Chi Square, Correlation and a single sample Kolmogrov–Smirnov test using SPSS software, version 16. Results: There were no significant variations in the amount of ANGPTL2, obestatin, cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein, cholesterol, creatinine and dehydroepiandrosterone-sulfate between the two groups. There were significant increases in serum levels of fasting blood sugar (p = 0.01), insulin (p = 0.04), homeostasis model assessments of insulin resistance (p = 0.04), testosterone (p = 0.02), luteinizing hormone (p = 0.004), luteinizing hormone/follicle stimulating hormone (p = 0.006) and prolactin (p = 0.04) in case group compared to the control group. A significant positive correlation was observed between ANGPTL2 and insulin (p = 0.02), HOMA-IR (p = 0.01) and, on the other hand, a significant negative correlation was observed between obestatin and insulin (p = 0.01), HOMA-IR (p = 0.008) in PCOS group. Conclusions: In this study, no significant variations were observed in serum levels of ANGPTL2 and obestatin in PCOS women with normal BMI.

Treatment with Obestatin-A Ghrelin Gene-Encoded Peptide-Reduces the Severity of Experimental Colitis Evoked by Trinitrobenzene Sulfonic Acid

Obestatin is a 23-amino acid peptide derived from proghrelin, a common prohormone for ghrelin and obestatin. Previous studies showed that obestatin exhibited some protective and therapeutic effects in the gut. The aim of our presented study was to examine the effect of treatment with obestatin on trinitrobenzene sulfonic acid (TNBS)-induced colitis. In rats anesthetized with ketamine, colitis was induced through intrarectal administration of 25 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Obestatin was administered intraperitoneally at doses of 4, 8, or 16 nmol/kg, twice per day for four consecutive days. The first dose of obestatin was given one day before the induction of colitis, and the last one was given two days after administration of TNBS. Fourteen days after the induction of colitis, rats were anesthetized again with ketamine, and the severity of colitis was determined. The administration of obestatin had no effect on the parameters tested in rats without the induction of colitis. In rats with colitis, administration of obestatin at doses of 8 or 16 nmol/kg reduced the area of colonic damage, and improved mucosal blood flow in the colon. These effects were accompanied by a reduction in the colitis-evoked increase in the level of blood leukocytes, and mucosal concentration of pro-inflammatory interleukin-1β. Moreover, obestatin administered at doses of 8 or 16 nmol/kg reduced histological signs of colonic damage. The administration of obestatin at a dose of 4 nmol/kg failed to significantly affect the parameters tested. Overall, treatment with obestatin reduced the severity of TNBS-induced colitis in rats. This effect was associated with an improvement in mucosal blood flow in the colon, and a decrease in local and systemic inflammatory processes.

Pretreatment with obestatin inhibits the development of acetic acid-induced colitis in rats

INTRODUCTION

Obestatin is a 23-amino acid peptide derived from proghrelin, a common prohormone for ghrelin and obestatin. Previous studies have shown that obestatin exhibits some protective and therapeutic effects in the pancreas and stomach. The aim of this study was to examine the effect of pretreatment with obestatin on the development of acetic acid-induced colitis.

MATERIAL AND METHODS

Studies were performed on Wistar rats. Before induction of colitis, rats were treated intraperitoneally with saline or obestatin, administered twice at a dose of 4, 8 or 16 nmol/kg/dose. The first dose of saline or obestatin was administered 8 h before the induction of colitis, the second one 7 h after the first dose. Colitis was induced by enema with 1 ml of 4% acetic acid solution. The severity of colitis was assessed 1 or 24 h after administration of enema.

RESULTS

Pretreatment with obestatin administered at a dose of 8 or 16 nmol/kg/dose significantly reduced the area of mucosal damage evoked by enema with acetic acid (p < 0.05). This effect was accompanied by an improvement of mucosal blood flow and DNA synthesis in the colon. Moreover, obestatin administered at a dose of 8 or 16 nmol/kg/dose significantly reduced mucosal concentration of IL-1β and activity of myeloperoxidase (p < 0.05).

CONCLUSIONS

Pretreatment with obestatin exhibited a protective effect in the colon, leading to a reduction of colonic damage in acetic acid-induced colitis. This effect was associated with an improvement of mucosal blood flow, an increase in mucosal cell proliferation, and a decrease in local inflammation.

Possible association of ghrelin/obestatin balance with cardiometabolic risk in obese subjects with Helicobacter pylori

OBJECTIVES

Helicobacter pylori (H. pylori) is a common gastric infection associated with extragastric conditions. The association between H. pylori infection and obesity is unclear. H. pylori may affect gut hormones involved in food intake and energy expenditure. The aim of this study is to evaluate ghrelin/obestatin balance and leptin in obese subjects with H. pylori infection.

METHODS

Sixty healthy volunteers were divided into: obese and non-obese groups. Each group was divided into H. Pylori positive or H. pylori negative. Anthropometric parameters, H. pylori status, serum glucose, insulin level, and lipid profile were estimated with calculation of Homeostasis Model Assessment Insulin Resistance (HOMA-IR). Serum levels of ghrelin, obestatin, and leptin were evaluated.

RESULTS

Significant increase was found in serum glucose, insulin and HOMA-IR ratio in obese subjects with positive H. pylori as compared to other groups. H. pylori positive obese subjects showed significantly increased ghrelin, ghrelin/obestatin balance, and leptin with a significant decrease in obestatin as compared to negative subjects. Ghrelin/obestatin ratio positively correlated with weight, body mass index, waist, glucose, insulin, HOMA-IR, leptin, cholesterol, triglycerides, low density cholesterol and also with H. pylori antigen in the same group.

CONCLUSIONS

It can be concluded that ghrelin, obestatin, and leptin are affected by presence of H. pylori seropositivity in obese subjects. The higher ghrelin levels and ghrelin/obestatin ratio with lowered obestatin could be considered as a gastro-protective effect against inflammation induced by H. pylori.

Krüppel-like factors: Crippling and un-crippling metabolic pathways

Krüppel-like factors (KLFs) are DNA-binding transcriptional factors that regulate various pathways that control metabolism and other cellular mechanisms. Various KLF isoforms have been associated with cellular, organ or systemic metabolism. Altered expression or activation of KLFs has been linked to metabolic abnormalities, such as obesity and diabetes, as well as with heart failure. In this review article we summarize the metabolic functions of KLFs, as well as the networks of different KLF isoforms that jointly regulate metabolism in health and disease.

Helicobacter pylori infection is positively associated with an increased BMI, irrespective of socioeconomic status and other confounders: a cohort study

BACKGROUND

Data on the association of Helicobacter pylori infection and BMI are conflicting. The fact that both H. pylori infection and BMI are associated with low socioeconomic status (SES) makes this relationship difficult to characterize.

MATERIALS AND METHODS

We aimed to evaluate the association between BMI and H. pylori infection after adjusting for multiple covariates. We analyzed a cohort of 235 107 individuals aged 18 years or older, who performed a C urease breath test (C-UBT), from 2007 to 2014. Data on BMI, age, sex, SES, ethnicity, and medications were extracted from a nationwide population-based database. BMIs were classified according to the WHO recommendations: underweight (<18.5 kg/m), normal weight (18.5-24.9 kg/m), overweight (25-29.9 kg/m), obese class I (30-34.9 kg/m), and obese class II or more (>35 kg/m).

STUDY RESULTS

The positivity rate for H. pylori among underweight, normal weight, overweight, and obese class I and class II or more was 55.6, 58.5, 63.0, 64.5, and 65.5%, respectively (P<0.001, Plinear trend 0.007). The association between BMI and H. pylori infection was significant across all SES, sex, ethnicity, and age categories. After adjusting for age, sex, ethnicity, and SES, being overweight and obese class I and class II or more were associated significantly with H. pylori positivity: odds ratio 1.13 [95% confidence interval (CI): 1.11-1.15], 1.14 (95% CI: 1.11-1.17), and 1.15 (95% CI: 1.11-1.19), respectively, P value less than 0.001 for all.

CONCLUSION

Among individuals who were referred to a C-UBT by primary care physician, after adjusting for multiple covariates including SES, we found a positive association between H. pylori infection and an increased BMI.

Implications of Aquaglyceroporin 7 in Energy Metabolism

The aquaglyceroporin AQP7 is a pore-forming transmembrane protein that facilitates the transport of glycerol across cell membranes. Glycerol is utilized both in carbohydrate and lipid metabolism. It is primarily stored in white adipose tissue as part of the triglyceride molecules. During states with increased lipolysis, such as fasting and diabetes, glycerol is released from adipose tissue and metabolized in other tissues. AQP7 is expressed in adipose tissue where it facilitates the efflux of glycerol, and AQP7 deficiency has been linked to increased glycerol kinase activity and triglyceride accumulation in adipose tissue, leading to obesity and secondary development of insulin resistance. However, AQP7 is also expressed in a wide range of other tissues, including kidney, muscle, pancreatic β-cells and liver, where AQP7 also holds the potential to influence whole body energy metabolism. The aim of the review is to summarize the current knowledge on AQP7 in adipose tissue, as well as AQP7 expressed in other tissues where AQP7 might play a significant role in modulating whole body energy metabolism.

Adipokines in human breast milk

The review describes the molecular characteristics of so far detected breast milk adipokines and ranks their breast milk level compared to the respective levels in maternal and infant blood. Moreover, analytical knowledge for measurements of breast milk adipokines will be delineated. Next, we summarized data about two main potential influencing factors on adipokine concentration in breast milk, maternal weight and pasteurization of milk. Finally, associations between adipokines in breast milk and weight gain in infants as well as the putative mechanisms for effects of breast milk adipokines on food intake and weight gain in later life will debated. Our findings suggest that a source of adipokines in human breast milk cannot be uniformly defined. In dependence on the ratio between serum and breast milk levels the major quantity of these proteins may be derived from peripheral tissues, from the breast tissue itself or from both. Thus, leptin and in part adiponectin levels in breast milk are dependent on a plenty of influencing factors with an important relevance of maternal anthropometric characteristics There is some evidence that leptin, adiponectin and ghrelin levels in breast milk may be associated with growth gain of infants and even with increased risk for being overweight during infancy or childhood. We hypothesize that a dysregulation in adipokine homeostasis in early life could promote obesity and metabolic disturbance in later life.

Protective Effect of Unacylated Ghrelin on Compression-Induced Skeletal Muscle Injury Mediated by SIRT1-Signaling

Unacylated ghrelin, the predominant form of circulating ghrelin, protects myotubes from cell death, which is a known attribute of pressure ulcers. In this study, we investigated whether unacylated ghrelin protects skeletal muscle from pressure-induced deep tissue injury by abolishing necroptosis and apoptosis signaling and whether these effects were mediated by SIRT1 pathway. Fifteen adult Sprague Dawley rats were assigned to receive saline or unacylated ghrelin with or without EX527 (a SIRT1 inhibitor). Animals underwent two 6-h compression cycles with 100 mmHg static pressure applied over the mid-tibialis region of the right limb whereas the left uncompressed limb served as the intra-animal control. Muscle tissues underneath the compression region, and at the similar region of the opposite uncompressed limb, were collected for analysis. Unacylated ghrelin attenuated the compression-induced muscle pathohistological alterations including rounding contour of myofibers, extensive nucleus accumulation in the interstitial space, and increased interstitial space. Unacylated ghrelin abolished the increase in necroptosis proteins including RIP1 and RIP3 and attenuated the elevation of apoptotic proteins including p53, Bax, and AIF in the compressed muscle. Furthermore, unacylated ghrelin opposed the compression-induced phosphorylation and acetylation of p65 subunit of NF-kB. The anti-apoptotic effect of unacylated ghrelin was shown by a decrease in apoptotic DNA fragmentation and terminal dUTP nick-end labeling index in the compressed muscle. The protective effects of unacylated ghrelin vanished when co-treated with EX527. Our findings demonstrated that unacylated ghrelin protected skeletal muscle from compression-induced injury. The myoprotective effects of unacylated ghrelin on pressure-induced tissue injury were associated with SIRT1 signaling.

Ghrelin and Motilin Control Systems in GI Physiology and Therapeutics

Ghrelin and motilin are released from gastrointestinal endocrine cells during hunger, to act through G protein-coupled receptors that have closely related amino acid sequences. The actions of ghrelin are more complex than motilin because ghrelin also exists outside the GI tract, it is processed to des-acyl ghrelin which has activity, ghrelin can exist in truncated forms and retain activity, the ghrelin receptor can have constitutive activity and is subject to biased agonism and finally additional ghrelin-like and des-acyl ghrelin receptors are proposed. Both ghrelin and motilin can stimulate gastric emptying, acting via different pathways, perhaps influenced by biased agonism at the receptors, but research is revealing additional pathways of activity. For example, it is becoming apparent that reduction of nausea may be a key therapeutic target for ghrelin receptor agonists and perhaps for compounds that modulate the constitutive activity of the ghrelin receptor. Reduction of nausea may be the mechanism through which gastroparesis symptoms are reduced. Intriguingly, a potential ability of motilin to influence nausea is also becoming apparent. Ghrelin interacts with digestive function through its effects on appetite, and ghrelin antagonists may have a place in treating Prader-Willi syndrome. Unlike motilin, ghrelin receptor agonists also have the potential to treat constipation by acting at the lumbosacral defecation centres. In conclusion, agonists of both ghrelin and motilin receptors hold potential as treatments for specific subsets of digestive system disorders.

Involvement of PPARγ in the Anticonvulsant Activity of EP-80317, a Ghrelin Receptor Antagonist

Ghrelin, des-acyl ghrelin and other related peptides possess anticonvulsant activities. Although ghrelin and cognate peptides were shown to physiologically regulate only the ghrelin receptor, some of them were pharmacologically proved to activate the peroxisome proliferator-activated receptor gamma (PPARγ) through stimulation of the scavenger receptor CD36 in macrophages. In our study, we challenged the hypothesis that PPARγ could be involved in the anticonvulsant effects of EP-80317, a ghrelin receptor antagonist. For this purpose, we used the PPARγ antagonist GW9662 to evaluate the modulation of EP-80317 anticonvulsant properties in two different models. Firstly, the anticonvulsant effects of EP-80317 were studied in rats treated with pilocarpine to induce status epilepticus (SE). Secondly, the anticonvulsant activity of EP-80317 was ascertained in the repeated 6-Hz corneal stimulation model in mice. Behavioral and video electrocorticographic (ECoG) analyses were performed in both models. We also characterized levels of immunoreactivity for PPARγ in the hippocampus of 6-Hz corneally stimulated mice. EP-80317 predictably antagonized seizures in both models. Pretreatment with GW9662 counteracted almost all EP-80317 effects both in mice and rats. Only the effects of EP-80317 on power spectra of ECoGs recorded during repeated 6-Hz corneal stimulation were practically unaffected by GW9662 administration. Moreover, GW9662 alone produced a decrease in the latency of tonic-clonic seizures and accelerated the onset of SE in rats. Finally, in the hippocampus of mice treated with EP-80317 we found increased levels of PPARγ immunoreactivity. Overall, these results support the hypothesis that PPARγ is able to modulate seizures and mediates the anticonvulsant effects of EP-80317.

Changes of Ghrelin/GOAT axis and mTOR pathway in the hypothalamus after sleeve gastrectomy in obese type-2 diabetes rats

AIM

To examine the changes of the ghrelin/ghrelin O-acyltransferase (GOAT) axis and the mammalian target of rapamycin (mTOR) pathway in the hypothalamus after sleeve gastrectomy.

METHODS

A total of 30 obese type-2 diabetes Sprague-Dawley (SD) rats, 6 wk of age, fed with high-sugar and high-fat fodder for 2 mo plus intraperitoneal injection of streptozotocin were randomly divided into three groups: non-operation group (S0 group, n = 10), sham operation group (Sh group, n = 10) and sleeve gastrectomy group (SG group, n = 10). Data of body mass, food intake, oral glucose tolerance test (OGTT), acylated ghrelin (AG) and total ghrelin (TG) were collected and measured at the first day (when the rats were 6 wk old), preoperative day 3 and postoperative week 8. The mRNA expression of preproghrelin, GOAT and neuropeptide Y (NPY), and protein expression of ghrelin, GOAT, GHSR and the mTOR pathway (p-Akt, p-mTOR and p-S6) were measured in the hypothalamus.

RESULTS

SG can significantly improve metabolic symptoms by reducing body mass and food intake. The obese rats showed lower serum TG levels and no change in AG, but the ratio of AG/TG was increased. When compared with the S0 and Sh groups, the SG group showed decreased TG (1482.03 ± 26.55, 1481.49 ± 23.30 and 1206.63 ± 52.02 ng/L, respectively, P < 0.05), but unchanged AG (153.06 ± 13.74, 155.37 ± 19.30 and 144.44 ± 16.689 ng/L, respectively, P > 0.05). As a result, the ratio of AG/TG further increased in the SG group (0.103 ± 0.009, 0.105 ± 0.013 and 0.12 ± 0.016, respectively, P < 0.05). When compared with the S0 group, SG suppressed mRNA and protein levels of preproghrelin (0.63 ± 0.12 vs 0.5 ± 0.11, P < 0.05) and GOAT (0.96 ± 0.09 vs 0.87 ± 0.08, P < 0.05), but did not change NPY mRNA expression (0.61 ± 0.04 vs 0.65 ± 0.07, P > 0.05) in the hypothalamus. The protein levels of p-Akt, p-mTOR and p-S6 were higher in the SG group, which indicated that the hypothalamic mTOR pathway was activated after SG at the postoperative week 8.

CONCLUSION

The reduction of ghrelin expression and activation of the mTOR pathway might have opposite effects on food intake, as SG improves obesity and T2DM.

α-melanocyte stimulating hormone modulates the central acyl ghrelin-induced stimulation of feeding, gastrointestinal motility, and colonic secretion

Background

Acyl ghrelin-induced intake depends on hypothalamic neuropeptide Y and agouti-related protein (AgRP) neurotransmitters. Intracerebroventricular (ICV) injection of AgRP increases feeding through competitive antagonism at melanocortin receptors. ICV administration of α-melanocyte stimulating hormone (α-MSH), a natural antagonist of AgRP, may modulate the acyl ghrelin-induced orexigenic effect.

Objective

This study aimed to investigate the modulating effect of α-MSH on the central acyl ghrelin-induced food intake, gastrointestinal motility, and colonic secretion in rats.

Methods and procedures

We examined the effects of α-MSH and acyl ghrelin on food intake, gastric emptying, small intestinal transit, colonic motility, and secretion in conscious rats with a chronic implant of ICV catheters.

Results

ICV injection of O-n-octanoylated ghrelin (0.1 nmol/rat) significantly increased the cumulative food intake up to 8 h (P<0.01), enhanced non-nutrient semi-liquid gastric emptying (P<0.001), increased the geometric center and running percentage of small intestinal transit (P<0.001), accelerated colonic transit time (P<0.05), and increased fecal pellet output (P<0.01) and total fecal weight (P<0.01). Pretreatment with ICV injection of α-MSH (1.0 and 2.0 nmol/rat) attenuated the acyl ghrelin-induced hyperphagic effect, fecal pellet output, and total fecal weight, while higher dose of α-MSH (2.0 nmol/rat) attenuated the increase in the geometric center of small intestinal transit (P<0.01). However, neither dose of α-MSH altered acyl ghrelin-stimulated gastroprokinetic effect, increase in the running percentage of small intestinal transit, nor accelerated colonic transit time.

Conclusion

α-MSH is involved in central acyl ghrelin-elicited feeding, small intestinal transit, fecal pellet output, and fecal weight. α-MSH does not affect central acyl ghrelin-induced acceleration of gastric emptying and colonic transit time in rats.

Unacylated ghrelin normalizes skeletal muscle oxidative stress and prevents muscle catabolism by enhancing tissue mitophagy in experimental chronic kidney disease

Unacylated ghrelin (UnAG) may lower skeletal muscle oxidative stress, inflammation, and insulin resistance in lean and obese rodents. UnAG-induced autophagy activation may contribute to these effects, likely involving removal of dysfunctional mitochondria (mitophagy) and redox state maintenance. In chronic kidney disease (CKD) oxidative stress, inflammation and insulin resistance may negatively influence patient outcome by worsening nutritional state through muscle mass loss. Here we show in a 5/6 nephrectomy (Nx) CKD rat model that 4 d s.c. UnAG administration (200 µg twice a day) normalizes CKD-induced loss of gastrocnemius muscle mass and a cluster of high tissue mitochondrial reactive oxygen species generation, high proinflammatory cytokines, and low insulin signaling activation. Consistent with these results, human uremic serum enhanced mitochondrial reactive oxygen species generation and lowered insulin signaling activation in C2C12 myotubes while concomitant UnAG incubation completely prevented these effects. Importantly, UnAG enhanced muscle mitophagy in vivo and silencing RNA-mediated autophagy protein 5 silencing blocked UnAG activities in myotubes. UnAG therefore normalizes CKD-induced skeletal muscle oxidative stress, inflammation, and low insulin signaling as well as muscle loss. UnAG effects are mediated by autophagy activation at the mitochondrial level. UnAG administration and mitophagy activation are novel potential therapeutic strategies for skeletal muscle metabolic abnormalities and their negative clinical impact in CKD.-Gortan Cappellari, G., Semolic, A., Ruozi, G., Vinci, P., Guarnieri, G., Bortolotti, F., Barbetta, D., Zanetti, M., Giacca, M., Barazzoni, R. Unacylated ghrelin normalizes skeletal muscle oxidative stress and prevents muscle catabolism by enhancing tissue mitophagy in experimental chronic kidney disease.

Changes in appetite, energy intake, body composition, and circulating ghrelin constituents during an incremental trekking ascent to high altitude

Purpose

Circulating acylated ghrelin concentrations are associated with altitude-induced anorexia in laboratory environments, but have never been measured at terrestrial altitude. This study examined time course changes in appetite, energy intake, body composition, and ghrelin constituents during a high-altitude trek.

Methods

Twelve participants [age: 28(4) years, BMI 23.0(2.1) kg m⁻²] completed a 14-day trek in the Himalayas. Energy intake, appetite perceptions, body composition, and circulating acylated, des-acylated, and total ghrelin concentrations were assessed at baseline (113 m, 12 days prior to departure) and at three fixed research camps during the trek (3619 m, day 7; 4600 m, day 10; 5140 m, day 12).

Results

Relative to baseline, energy intake was lower at 3619 m (P = 0.038) and 5140 m (P = 0.016) and tended to be lower at 4600 m (P = 0.056). Appetite perceptions were lower at 5140 m (P = 0.027) compared with baseline. Acylated ghrelin concentrations were lower at 3619 m (P = 0.046) and 4600 m (P = 0.038), and tended to be lower at 5140 m (P = 0.070), compared with baseline. Des-acylated ghrelin concentrations did not significantly change during the trek (P = 0.177). Total ghrelin concentrations decreased from baseline to 4600 m (P = 0.045). Skinfold thickness was lower at all points during the trek compared with baseline (P ≤ 0.001) and calf girth decreased incrementally during the trek (P = 0.010).

Conclusions

Changes in plasma acylated and total ghrelin concentrations may contribute to the suppression of appetite and energy intake at altitude, but differences in the time course of these responses suggest that additional factors are also involved. Interventions are required to maintain appetite and energy balance during trekking at terrestrial altitudes.

Anti-oxidant and anti-inflammatory effects of hydrogen-rich water alleviate ethanol-induced fatty liver in mice

AIM

To investigate the effects of hydrogen-rich water (HRW) treatment on prevention of ethanol (EtOH)-induced early fatty liver in mice.

METHODS

In vitro reduction of hydrogen peroxide by HRW was determined with a chemiluminescence system. Female mice were randomly divided into five groups: control, EtOH, EtOH + silymarin, EtOH + HRW and EtOH + silymarin + HRW. Each group was fed a Lieber-DeCarli liquid diet containing EtOH or isocaloric maltose dextrin (control diet). Silymarin was used as a positive control to compare HRW efficacy against chronic EtOH-induced hepatotoxicity. HRW was freshly prepared and given at a dosage of 1.2 mL/mouse trice daily. Blood and liver tissue were collected after chronic-binge liquid-diet feeding for 12 wk.

RESULTS

The in vitro study showed that HRW directly scavenged hydrogen peroxide. The in vivo study showed that HRW increased expression of acyl ghrelin, which was correlated with food intake. HRW treatment significantly reduced EtOH-induced increases in serum alanine aminotransferase, aspartate aminotransferase, triglycerol and total cholesterol levels, hepatic lipid accumulation and inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6. HRW attenuated malondialdehyde level, restored glutathione depletion and increased superoxide dismutase, glutathione peroxidase and catalase activities in the liver. Moreover, HRW reduced TNF-α and IL-6 levels but increased IL-10 and IL-22 levels.

CONCLUSION

HRW protects against chronic EtOH-induced liver injury, possibly by inducing acyl ghrelin to suppress the pro-inflammatory cytokines TNF-α and IL-6 and induce IL-10 and IL-22, thus activating antioxidant enzymes against oxidative stress.

Obestatin stimulates glucose-induced insulin secretion through ghrelin receptor GHS-R

Orexigenic hormone ghrelin and anorexic hormone obestatin are encoded by the same preproghrelin gene. While it is known that ghrelin inhibits glucose-stimulated insulin secretion (GSIS), the effect of obestatin on GSIS is unclear. Ghrelin’s effect is mediated by its receptor Growth Hormone Secretagogue Receptor (GHS-R), but the physiologically relevant receptor of obestatin remains debatable. Here we have investigated the effect of obestatin on GSIS in vitro, in vivo and ex vivo, and tested whether obestatin regulates insulin secretion through GHS-R. We found that under hyperglycemic condition, obestatin augments GSIS in rat insulinoma cells (INS-1) and in pancreatic islets from ghrelin^−/− mice. Surprisingly, obestatin-induced GSIS was absent in β-cells in which GHS-R was suppressed. Obestatin-induced insulin secretion was abolished in the circulation of Ghsr^−/− mice, and in pancreatic islets isolated from Ghsr^−/− mice. We also found that obestatin-induced GSIS was attenuated in islets isolated from β-cell-specific Ghsr knockout MIP-Cre/ERT;Ghsr^f/f mice. Our data collectively demonstrate that obestatin is a potent insulin secretagogue under hyperglycemic condition, and obestatin’s effect on insulin secretion is mediated by GHS-R in pancreatic β-cells. Our findings reveal an intriguing insight that obestatin and ghrelin have opposing effects on insulin secretion, and both are mediated through ghrelin receptor GHS-R.

Plasma ghrelin level and plasma ghrelin/obestatin ratio are related to intestinal metaplasia in elderly patients with functional dyspepsia

Background

Whether plasma ghrelin/obestatin levels are associated with Helicobacter pylori (H. pylori) infection, subtypes of functional dyspepsia (FD), and gastric mucosal histology has not yet been established in elderly patients.

Objective

The aim of this study was to determine whether plasma ghrelin and obestatin levels are related to gastric mucosal histology, H. pylori infection, and FD subtypes in elderly patients with FD.

Methods

Ninety-two patients diagnosed with FD and older than 60 years (median age 69.4; range 60–88) were included. Clinical symptoms investigated included postprandial fullness, epigastric pain, epigastric soreness, nausea, and vomiting. According to the Rome III criteria, patients diagnosed with FD were divided into two subtypes: epigastric pain syndrome (EPS) and postprandial distress syndrome (PDS). Plasma ghrelin and obestatin levels were measured using enzyme immunoassay, and histological examination of gastric mucosa was performed. H. pylori infection was determined by histopathological examination of gastric mucosal biopsy and/or Campylobacter-like organism test.

Results

In our study, plasma ghrelin levels and plasma ghrelin/obestatin (G/O) ratio were significantly lower in subjects with intestinal metaplasia compared with those without intestinal metaplasia (ghrelin, p = 0.010; G/O ratio, p = 0.012). On the other hand, there were no significant differences in plasma ghrelin and obestatin levels between H. pylori–positive and H. pylori–negative groups. (ghrelin, p = 0.130; obestatin, p = 0.888). Similarly, no significant differences were detected between the EPS and PDS groups (ghrelin, p = 0.238; obestatin, p = 0.710).

Conclusions

Patients with intestinal metaplasia, a known precursor of gastric cancer, had significantly less plasma ghrelin levels and G/O ratio than those without intestinal metaplasia.

Comparison of consumption behavior and appetite sensations among patients with type 2 diabetes mellitus after bariatric surgery

BACKGROUND

The promising postsurgical weight loss and remission of type 2 diabetes (T2D) from bariatric surgery can be attributed to modified eating physiology after surgical procedures. We sought to investigate the changes in the parameters of consumption behaviors and appetite sensations induced by a mixed meal tolerance test, and to correlate these alterations with age, body mass index, C-peptide levels, and duration of T2D 1 year after bariatric surgery.

METHODS

A total of 16 obese patients with T2D who underwent mini-gastric bypass (GB) and 16 patients who underwent sleeve gastrectomy (SG) were enrolled in this study and evaluated using a mixed meal tolerance test one year after surgery. A visual analogue scale was used for scoring appetite sensation at different time points. The area under the curve (AUC) and the incremental or decremental AUC (ΔAUC) were compared between the two groups.

RESULTS

One year after surgery, a decreasing trend in the consumption time was observed in the GB group compared to the SG group, while the duration of T2D before surgery was negatively correlated with the post-operative consumed time in those after GB. Patients who underwent GB had significantly higher fasting scores for fullness and desire to eat, higher AUC_0'-180' of scores for desire to eat, as well as more effective post-meal suppression of hunger and desire to eat compared with those undergoing SG one year after surgery. Post-operative C-peptide levels were negatively correlated with ΔAUC_0'-180' for hunger and ΔAUC_0'-180' for desire to eat in the GB group, while negatively correlated with ΔAUC_0'-180' for fullness in the SG group.

DISCUSSION

Patients with T2D after either GB or SG exhibit distinct nutrient-induced consumption behaviors and appetite sensations post-operatively, which may account for the differential effects on weight loss and glycemic control after different surgery.

Plasma Ghrelin Levels Are Associated with Anorexia but Not Cachexia in Patients with NSCLC

Background and Aims: The ghrelin receptor is one of the new therapeutic targets in the cancer anorexia-cachexia syndrome. Previous studies revealed that plasma ghrelin levels were high in patients with anorexia nervosa and low in obese subjects. We studied to what extent ghrelin levels are related with anorexia and cachexia in patients with cancer.

Materials and Methods: Fasted ghrelin levels were determined as well as anorexia and cachexia in patients with stage III/IV non-small cell lung cancer before chemotherapy. Total plasma ghrelin was measured by radioimmunoassay. Anorexia was measured with the FAACT-A/CS questionnaire (cut-off value ≤ 37). Cachexia was determined as >5% weight loss (WL) in 6 months or >2% WL in 6 months in combination with low BMI or low muscle mass. The Kruskal-Wallis test was performed to assess differences in plasma ghrelin levels between four groups: patients with (+) or without (−) anorexia (A) or cachexia (C). Multiple regression analyses were performed to assess differences in plasma ghrelin levels between patients C+ and C− and patients with A+ and A− (adjusted for age and sex).

Results: Forty patients with stage III (33%) or stage IV (68%) were recruited, of which 50% was male. Mean age was 59.6 ± 10.3 years. Sixteen patients had no anorexia or cachexia (A−C−), seven patients had both anorexia and cachexia (A+C+), ten patients had anorexia without cachexia (A+C−) and seven patients had cachexia without anorexia (A−C+). The levels of total plasma ghrelin were significantly different between the four groups of patients with or without anorexia or cachexia (p = 0.032): the A+C− patients had significantly higher ghrelin levels [median (IQR): 1,754 (1,404–2,142) compared to the A−C+ patients 1,026 (952–1,357), p = 0.003]. A+ patients had significantly higher ghrelin levels compared A− patients (C+ and C− combined, β: 304, p = 0.020). Plasma ghrelin levels were not significantly different in C+ patients compared to C− patients (A+ and A− combined, β: −99, p = 0.450).

Conclusions: Patients with anorexia had significantly higher ghrelin levels compared to patients without anorexia. We therefore hypothesize that patients with cancer anorexia might benefit from treatment with a ghrelin receptor agonist to prevent WL and deterioration in physical functioning.