Action Of Ghrelin Research Articles

FTO variant is associated with changes in BMI, ghrelin, and brain function following bariatric surgery.

BACKGROUNDA polymorphism in the fat mass and obesity-associated gene (FTO) is linked to enhanced neural sensitivity to food cues and attenuated ghrelin suppression. Risk allele carriers regain more weight than noncarriers after bariatric surgery. It remains unclear how FTO variation affects brain function and ghrelin following surgery.METHODSResting-state functional magnetic resonance imaging and cue-reactivity functional magnetic resonance imaging with high-/low-caloric food cues were performed before surgery and at 1, 6, and 12 months after surgery to examine brain function in 16 carriers with 1 copy of the rs9939609 A allele (AT) and 26 noncarriers (TT). Behavioral assessments up to 5 years after surgery were also conducted.RESULTSThe AT group relative to the TT group had smaller BMI loss at 12-60 months after surgery and lower resting-state activity in posterior cingulate cortex following laparoscopic sleeve gastrectomy (group-by-time interaction effects). Meanwhile, the AT group relative to the TT group showed greater food cue responses in dorsolateral prefrontal cortex (DLPFC), dorsomedial prefrontal cortex (DMPFC), and insula (group effects). There were negative associations of weight loss with ghrelin and greater activation in DLPFC, DMPFC and insula in the AT but not the TT group.CONCLUSIONThese findings indicate that FTO variation is associated with the evolution of ghrelin signaling and brain function after bariatric surgery, which might hinder weight loss.TRIAL REGISTRATIONChinese Clinical Trial Registry Center, ChiCTR-OOB-15006346.FUNDINGThis work was supported by the National Natural Science Foundation of China (grant nos. 82172023, 82202252, 82302292); National Key R&D Program of China (no. 2022YFC3500603); Natural Science Basic Research Program of Shaanxi (grant nos. 2022JC-44, 2022JQ-622, 2023-JC-QN-0922, 2023-ZDLSF-07); Fundamental Research Funds for the Central Universities (grant nos. ZYTS23188, XJSJ23190, XJS221201, QTZX23093); and the Intramural Research Program of the National Institute on Alcoholism and Alcohol Abuse (grant no. Y1AA3009).

Ghrelin, Neuroinflammation, Oxidative Stress, and Mood Disorders: What Are the Connections?

Ghrelin is a gut peptide hormone associated with feeding behavior and energy homeostasis. Acylated ghrelin binds to the growth hormone secretagogue receptor 1a subtype (GHS-R1a) in the hippocampus, leading to GH release from the anterior pituitary. However, in recent years, ghrelin and its receptor have also been implicated in other processes, including the regulation of cardiomyocyte function, muscle trophism, and bone metabolism. Moreover, GHS-R1a is distributed throughout the brain and is expressed in brain areas that regulate the stress response and emotional behavior. Consistently, a growing body of evidence supports the role of ghrelin in regulating stress response and mood. Stress has consistently been shown to increase ghrelin levels, and despite some inconsistencies, both human and rodent studies suggested antidepressant effects of ghrelin. Nevertheless, the precise mechanism by which ghrelin influences stress response and mood remains largely unknown. Intriguingly, ghrelin and GHS-R1a were consistently reported to exert anti-inflammatory, antioxidant, and neurotrophic effects both in vivo and in vitro, although this has never been directly assessed in relation to psychopathology. In the present review we will discuss available literature linking ghrelin with the stress response and depressive-like behavior in animal models as well as evidence describing the interplay between ghrelin and neuroinflammation/oxidative stress. Although further studies are required to understand the mechanisms involved in the action of ghrelin on mood, we hypothesize that the antiinflammatory and anti-oxidative properties of ghrelin may give a key contribution.

Acyl modifications in bovine, porcine, and equine ghrelins.

Ghrelin is a peptide hormone with various important physiological functions. The unique feature of ghrelin is its serine 3 acyl-modification, which is essential for ghrelin activity. The major form of ghrelin is modified with n-octanoic acid (C8:0) by ghrelin O-acyltransferase. Various acyl modifications have been reported in different species. However, the underlying mechanism by which ghrelin is modified with various fatty acids remains to be elucidated. Herein, we report the purification of bovine, porcine, and equine ghrelins. The major active form of bovine ghrelin was a 27-amino acid peptide with an n-octanoyl (C8:0) modification at Ser3. The major active form of porcine and equine ghrelin was a 28-amino acid peptide. However, porcine ghrelin was modified with n-octanol (C8:0), whereas equine ghrelin was modified with n-butanol (C4:0) at Ser3. This study indicates the existence of structural divergence in ghrelin and suggests that it is necessary to measure the minor and major forms of ghrelin to fully understand its physiology.

Role of ghrelin hormone in the development of alcohol-associated liver disease

Fatty liver is the earliest response of the liver to excessive alcohol consumption. Previously we identified that chronic alcohol administration increases levels of stomach-derived hormone, ghrelin, which by reducing circulating insulin levels, ultimately contributes to the development of alcohol-associated liver disease (ALD). In addition, ghrelin directly promotes fat accumulation in hepatocytes by enhancing de novo lipogenesis. Other than promoting ALD, ghrelin is known to increase alcohol craving and intake. In this study, we used a ghrelin receptor (GHSR) knockout (KO) rat model to characterize the specific contribution of ghrelin in the development of ALD with emphasis on energy homeostasis. Male Wistar wild type (WT) and GHSR-KO rats were pair-fed the Lieber-DeCarli control or ethanol diet for 6 weeks. At the end of the feeding period, glucose tolerance test was conducted, and tissue samples were collected. We observed reduced alcohol intake by GHSR-KOs compared to a previous study where WT rats were fed ethanol diet ad libitum. Further, when the WTs were pair-fed to GHSR-KOs, the KO rats exhibited resistance to develop ALD through improving insulin secretion/sensitivity to reduce adipose lipolysis and hepatic fatty acid uptake/synthesis and increase fatty acid oxidation. Furthermore, proteomic data revealed that ethanol-fed KO exhibit less alcohol-induced mitochondrial dysfunction and oxidative stress than WT rats. Proteomic data also confirmed that the ethanol-fed KOs are insulin sensitive and are resistant to hepatic steatosis development compared to WT rats. Together, these data confirm that inhibiting ghrelin action prevent alcohol-induced liver and adipose dysfunction independent of reducing alcohol intake.

Leptin and ghrelin dynamics: unraveling their influence on food intake, energy balance, and the pathophysiology of type 2 diabetes mellitus.

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by insulin resistance and impaired glucose homeostasis. In recent years, there has been growing interest in the role of hunger and satiety hormones such as ghrelin and leptin in the development and progression of T2DM. In this context, the present literature review aims to provide a comprehensive overview of the current understanding of how ghrelin and leptin influences food intake and maintain energy balance and its implications in the pathophysiology of T2DM. A thorough literature search was performed using PubMed and Google Scholar to choose the studies that associated leptin and ghrelin with T2DM. Original articles and reviews were included, letters to editors and case reports were excluded. This narrative review article provides a comprehensive summary on mechanism of action of leptin and ghrelin, its association with obesity and T2DM, how they regulate energy and glucose homeostasis and potential therapeutic implications of leptin and ghrelin in managing T2DM. Ghrelin, known for its appetite-stimulating effects, and leptin, a hormone involved in the regulation of energy balance, have been implicated in insulin resistance and glucose metabolism. Understanding the complexities of ghrelin and leptin interactions in the context of T2DM may offer insights into novel therapeutic strategies for this prevalent metabolic disorder. Further research is warranted to elucidate the molecular mechanisms underlying these hormone actions and to explore their clinical implications for T2DM prevention and management.

Effects of Empagliflozin-Induced Glycosuria on Weight Gain, Food Intake and Metabolic Indicators in Mice Fed a High-Fat Diet.

Sodium glucose-linked transporter 2 (SGLT2) inhibitors promote glucose, and therefore calorie, excretion in the urine. Patients taking SGLT2 inhibitors typically experience mild weight loss, but the amount of weight loss falls short of what is expected based on caloric loss. Understanding the mechanisms responsible for this weight loss discrepancy is imperative, as strategies to improve weight loss could markedly improve type 2 diabetes management and overall metabolic health. Two mouse models of diet-induced obesity were administered the SGLT2 inhibitor empagliflozin in the food for 3 months. Urine glucose excretion, body weight, food intake and activity levels were monitored. In addition, serum hormone measurements were taken, and gene expression analyses were conducted. In both mouse models, mice receiving empagliflozin gained the same amount of body weight as their diet-matched controls despite marked glucose loss in the urine. No changes in food intake, serum ghrelin concentrations or activity levels were observed, but serum levels of fibroblast growth factor 21 (FGF21) decreased after treatment. A decrease in the levels of deiodinase 2 (Dio2) was also observed in the white adipose tissue, a primary target tissue of FGF21. These findings suggest that compensatory metabolic adaptations, other than increased food intake or decreased physical activity, occur in response to SGLT2 inhibitor-induced glycosuria that combats weight loss, and that reductions in FGF21, along with subsequent reductions in peripheral Dio2, may play a role.

The New Trends in Physiological and Pathological Actions of Ghrelin (Brain-Heart Axis) on the Heart and Cardiovascular System

Background: Ghrelin increased significantly the Left Ventriculus Eject Fraction and end-systolic volume after 30 minutes of intra-venous injection and without alterations heart rate and blood pressure. Ghrelin was discovered in 1999 as an only one 28 amino acid peptides (with octanoyl serine group) located on the short arm of chromosome 3 (position 3p25-26) having six exons, two are noncoding and four introns and encodes a 511 bp mRNA. Ghrelin is synthesized by the endocrine X/A-like cells located from the gastric fundus mucosa through the whole mucosa of the medium right vertical side of the stomach until to the 1 inch before anatomical pylorus. These cells are responsible to produced 80% of the whole ghrelin produced in the human body. Furthermore, other place of this production occurs at the hypothalamus, the pituitary, second portion of duodenum, pancreas, heart and other tissues. Bibliographic references also demonstrate the importance of ghrelin’s action in the main cardiovascular activities. Related to cardiovascular activities, ghrelin plays multitudinous beneficial and thereby help during cardiovascular diseases. Several studies demonstrated that ghrelin cause an anti-inflammatory activity by the inhibition of proinflammatory cytokines which can diminish inflammatory diseases in the heart, pericardium and specific innervations, for instance, vagus nerve and inhibited sympathetic nerves. Outcomes of this review emphasize these important actions of ghrelin. Methods: A systematic review of ghrelin activities over the heart and cardiovascular system with the inclusion of papers in review involved the physiological and physio pathological activities of ghrelin in vivo and in vitro studies. Results: Ghrelin is a natural tide with the growth hormone secretagogue (GHS) receptor (GHS-R) which cloned in 1996. The processes which generate this peptide and ghrelin-related peptides are transcriptional, translational and posttranslational. Homo and heterodimers of GHS-R and other yet unidentified receptors mediate the biological actions of acyl ghrelin and desacyl ghrelin. However, the main biological functions of ghrelin involve the secretion of growth hormone, stimulation of appetite and food intake at the hypothalamus, modulate acid secretion and motility, endocrine and exocrine pancreas secretion, blockaded insulin activity, heart functions and cardiovascular responses and other. Conclusion: One of the main occurrences in acute heart infarction is an increase activation of cardiac sympathetic nerve activity (CSNA) which is one of the causes of chronic cardiac dysfunction (CCD). Ghrelin is an effective for obtain a better cardiac function and by the suppression of renal sympathetic nerve activity which also have an important benefit to the acute myocardial infarction. Therefore, the physiological effects of ghrelin are very important to the body homeostasis even in the grave heart and cardiovascular diseases and in the immunological system.

Elevated Ghrelin Promotes Hippocampal Ghrelin Receptor Defects in Humanized Amyloid-β Knockin Mice During Aging.

Emerging evidence has revealed that dysregulation of the hormone ghrelin and its receptor, growth hormone secretagogue receptor (GHSR), contributes to the pathogenesis of Alzheimer's disease (AD). Specifically, defective GHSR function and resultant hippocampal ghrelin resistance are linked to hippocampal synaptic injury in AD paradigms. Also, AD patients exhibit elevated ghrelin activation. However, the detailed molecular mechanisms of hippocampal GHSR dysfunction and the relevance of ghrelin elevation to hippocampal ghrelin resistance in AD-relevant pathological settings are not fully understood. In the current study, we employed a recently established mouse line of AD risk [humanized amyloid beta knockin (hAβ KI mice), also referred to as a mouse model of late-onset AD in previous literature] to further define the role of ghrelin system dysregulation in the development of AD. We employed multidisciplinary techniques to determine the change of plasma ghrelin and the functional status of GHSR in hAβ KI mice as well as primary neuron cultures. We observed concurrent plasma ghrelin elevation and hippocampal GHSR desensitization with disease progression. Further examination excluded the possibility that ghrelin elevation is a compensatory change in response to GHSR dysfunction. In contrast, further in vitro and in vivo results show that agonist-mediated overstimulation potentiates GHSR desensitization through enhanced GHSR internalization. These findings suggest that circulating ghrelin elevation is a pathological event underlying hippocampal GHSR dysfunction, culminating in hippocampal ghrelin resistance and resultant synaptic injury in late-onset AD-related settings.

Potential Applications for Growth Hormone Secretagogues Treatment of Amyotrophic Lateral Sclerosis.

Amyotrophic lateral sclerosis (ALS) arises from neuronal death due to complex interactions of genetic, molecular, and environmental factors. Currently, only two drugs, riluzole and edaravone, have been approved to slow the progression of this disease. However, ghrelin and other ligands of the GHS-R1a receptor have demonstrated interesting neuroprotective activities that could be exploited in this pathology. Ghrelin, a 28-amino acid hormone, primarily synthesized and secreted by oxyntic cells in the stomach wall, binds to the pituitary GHS-R1a and stimulates GH secretion; in addition, ghrelin is endowed with multiple extra endocrine bioactivities. Native ghrelin requires esterification with octanoic acid for binding to the GHS-R1a receptor; however, this esterified form is very labile and represents less than 10% of circulating ghrelin. A large number of synthetic compounds, the growth hormone secretagogues (GHS) encompassing short peptides, peptoids, and non-peptidic moieties, are capable of mimicking several biological activities of ghrelin, including stimulation of GH release, appetite, and elevation of blood IGF-I levels. GHS have demonstrated neuroprotective and anticonvulsant effects in experimental models of pathologies both in vitro and in vivo. To illustrate, some GHS, currently under evaluation by regulatory agencies for the treatment of human cachexia, have a good safety profile and are safe for human use. Collectively, evidence suggests that ghrelin and cognate GHS may constitute potential therapies for ALS.

Salivary and crevicular fluid proinflammatory cytokines and advanced glycation end products in patients with different glycemic levels undergoing fixed orthodontic treatment.

To examine whether patients with different blood glycemic levels undergoing fixed orthodontic therapy demonstrate changes in the biochemical profiles of crevicular fluid and salivary advanced glycation end products (AGEs) and proinflammatory cytokine levels in comparison with nondiabetic healthy subjects. Prediabetic subjects, subjects with type 2 diabetes mellitus (T2DM), and subjects without a diabetes mellitus diagnosis undergoing fixed orthodontic therapy with MBT prescription brackets (0.022-inch brackets and 0.019 × 0.025-inch stainless steel archwires) were included in the study. The following clinical periodontal parameters were evaluated: (1) plaque score (PS), (2) probing depth (PD), (3) bleeding on probing (BOP), and (4) clinical attachment loss. Crevicular fluid and saliva specimens were collected during regular orthodontic visits. Salivary and crevicular fluid tumor necrosis factor alpha, interleukin-6, ghrelin, resistin, AGEs, and receptor activator of nuclear factor κΒ ligand were evaluated using a human magnetic Luminex multiplex assay. BOP scores were significantly higher among T2DM subjects (19.2%) than among nondiabetic subjects (11.2%) and prediabetic subjects (15.9%). Comparable values were demonstrated by all three study groups regarding PD scores and PSs. T2DM subjects demonstrated higher scores for gingival crevicular fluid (GCF) chemokines than nondiabetic and prediabetic subjects. A statistically significant difference was found in the levels of AGEs and resistin among the three study groups. The scores revealed for the levels of GCF resistin and AGEs versus periodontal BOP demonstrated a significant positive association by the Pearson correlation test. T2DM patients demonstrated significantly higher levels of GCF resistin and AGEs during fixed orthodontic therapy. Chronic hyperglycemic patients undergoing orthodontic therapy demonstrated a proinflammatory response.

Genetic insights into obesity: in silico identification of pathogenic SNPs in MBOAT4 gene and their structural molecular dynamics consequences

Membrane Bound O-Acyltransferase Domain-Containing 4 (MBOAT4) protein catalyzes ghrelin acylation, leading to prominent ghrelin activity, hence characterizing its role as an anti-obesity target. We extracted 625 exonic SNPs from the ENSEMBL database and one phenotype-based missense mutation associated with obesity (A46T) from the HGMD (Human Gene Mutation Database). These were differentiated on deleterious missense SNPs of the MBOAT4 gene through MAF (minor allele frequency: <0.01) cut-off criteria in relation to some bioinformatics-based supervised machine learning tools. We found 8 rare-coding and harmful missense SNPs. The consensus classifier (PredictSNP) tool predicted that the SNP (G57S, C: rs561065025) was the most pathogenic. Several trained in silico algorithms have predicted decreased protein stability [ΔΔG (kcal/mol)] function in the presence of these rare-coding pathogenic mutations in the MBOAT4 gene. Then, a stereochemical quality check (i.e. validation and assessment) of the 3D model was performed, followed by a blind cavity docking approach, used to search for druggable cavities and molecular interactions with citrus flavonoids of the Rutaceae family, ranked with energetic estimations. Significant interactions with Phloretin 3',5'-Di-C-Glucoside were also observed at R304, W306, N307, A311, L314 and H338 with (iGEMDOCK: −95.82 kcal/mol and AutoDock: −7.80 kcal/mol). The RMSD values and other variables of MD simulation analyses on this protein further validated its significant interactions with the above flavonoids. The MBOAT4 gene and its molecular interactions could serve as an interventional future anti-obesity target. The current study’s findings will benefit future prospects for large population-based studies and drug development, particularly for generating personalized medicine. Communicated by Ramaswamy H. Sarma

FRI074 Rise In Fasting Ghrelin Level In Response To Weight Loss Predicts Future Weight Regain In The POUNDS LOST Trial

Abstract Disclosure: J. Tong: None. Y. Heianza: None. E.A. Schur: None. F. Sacks: None. L. Qi: None. E.J. Boyko: None. Weight loss maintenance is a challenging problem commonly encountered in obesity management. The biological mechanism for weight regain following diet-induced weight loss is not well understood. The orexigenic gut hormone ghrelin increases appetite and food intake and promote positive energy balance. We aim to investigate whether weight-loss induced fasting ghrelin changes predict subsequent weight regain in the POUNDS LOST trial. Methods: This study included 244 overweight or obese adults (age: 52.9±8.8 yr; 66% female; BMI 32.4±3.9 kg/m2 [mean ± SD]) randomly assigned to 1 of 4 weight-loss diets varying in macronutrient intake who had fasting plasma total ghrelin levels measured at baseline, 6 and 24 months after the intervention. We examined associations between fasting ghrelin levels changes between baseline and 6-months (weight change: -7.1±5.3 kg) and body weight change between 12 and 24 months (3.2±3.9 kg). Results: Fasting plasma ghrelin level increased significantly at 6 months (from 487.3±251.1 to 574.0±274.5 pg/mL) and remained elevated at 24 months despite weight regain (684.0±411.0 pg/mL). Increases in ghrelin level from baseline to 6 months (86.7±167.4 pg/mL) were correlated with weight regain from 12 to 24 months (p=0.018). The association was unchanged after adjustment for age, sex, race, and diet assignment at baseline; fat and carbohydrate craving scores, hunger and fullness ratings, dietary restraint and disinhibition scores measured at 6 months, prior to onset of weight regain. Conclusions: Fasting ghrelin levels rose in response to diet-induced weight loss and persisted for 2 years despite weight regain. Ghrelin change during the weight loss phase predicts subsequent weight regain independent of appetite and craving measures. Understanding the mechanistic connection between ghrelin action and weight regain may shed light on novel approaches to weight loss maintenance. Presentation: Friday, June 16, 2023

OR12-04 LEAP2 Deletion Does Not Counteract The Effects Of Ghrelin Deletion During Insulin-Induced-Hypoglycemia

Abstract Disclosure: K. Shankar: None. S. Varshney: None. D. Gupta: None. O. Singh: None. S.B. Ogden: None. S. Osborne-Lawrence: None. N.P. Metzger: None. C.P. Richard: None. J.M. Zigman: Grant Recipient; Self; Novo Nordisk. Objective: The hormones ghrelin and LEAP2 both are endogenous ligands for the growth hormone secretagogue receptor (GHSR). Whereas ghrelin activates GHSR, LEAP2 blocks ghrelin from activating GHSR and also inhibits GHSR constitutive activity. It is via GHSR that the glucoregulatory actions of ghrelin and LEAP2 are mediated. These glucoregulatory actions are highlighted by the findings of severe hypoglycemia in ghrelin-KO mice and LEAP2-overexpressing mice when they are submitted to an acute-on-chronic caloric restriction protocol. Also, recently, our group showed that ghrelin-KO mice require a much higher glucose infusion rate (GIR) and exhibit markedly reduced elevation of counterregulatory hormones when submitted to a hyperinsulinemic-hypoglycemic clamp. In the current study, we investigated the potential of LEAP2 to protect against insulin-induced-hypoglycemia and counteract the effects of ghrelin deletion during the hypoglycemic clamp. Methods: Eight-ten week-old male wild-type (WT), Ghrelin-KO, LEAP2-KO, and LEAP2/Ghrelin-doubleKO (lacking both ghrelin and LEAP2 ) littermates were used for this study (n=7-10 per genotype). Mice were implanted with a right jugular vein catheter. Five days later, hyperinsulinemic-hypoglycemic clamps were performed in conscious, unrestrained mice. A low dose of insulin was infused at 4 mU/kg/min i.v. over 2 hr. A 20% glucose solution was simultaneously infused at a variable rate to achieve hypoglycemia (35–45 mg/dL) during the final 30 min. Blood glucose was measured via tail nicks every 5 min. Results: We were able to achieve the target hypoglycemic range in all four genotypes using this protocol. As compared to WT mice, Ghrelin-KO mice required markedly elevated (∼110% higher) GIRs (10±4 mg/kg/min in WT vs. 22±2 mg/kg/min in Ghrelin-KO mice; p=0.03) by the end of the 2-hr clamp. The GIRs required by LEAP2-KO mice were equivalent to those of WT mice (7±2 mg/kg/min in LEAP2-KO; p=n.s.). Furthermore, although during the first 60 min of the clamp, LEAP2/Ghrelin-doubleKO mice exhibited slightly lower blood glucose levels than the other genotypes and during the middle 60 min of the clamp, they required higher GIRs than the other genotypes, by the end of the 2-hr clamp, their GIRs were similar to Ghrelin-KO mice (25±3 mg/Kg/min in Ghrelin/LEAP2-doubleKO mice, p=n.s.). Conclusions: These data suggest a complex effect of LEAP2 on blood glucose. Alone, LEAP2 deletion does not impact insulin sensitivity. When coupled with ghrelin deletion, LEAP2 deletion lowers fasting blood glucose and causes greater insulin sensitivity early on during the hyperinsulinemic-hypoglycemic clamp. By the end of the clamp, this effect of LEAP2 deletion when coupled to ghrelin deletion is gone. Altogether, these results suggest that LEAP2 deletion does not counteract the effects of ghrelin deletion during insulin-induced hypoglycemia. Presentation: Friday, June 16, 2023

Ghrelin Action in the PVH of Male Mice: Accessibility, Neuronal Targets, and CRH Neurons Activation.

The hormone ghrelin displays several well-characterized functions, including some with pharmaceutical interest. The receptor for ghrelin, the growth hormone secretagogue receptor (GHSR), is expressed in the hypothalamic paraventricular nucleus (PVH), a critical hub for the integration of metabolic, neuroendocrine, autonomic, and behavioral functions. Here, we performed a neuroanatomical and functional characterization of the neuronal types mediating ghrelin actions in the PVH of male mice. We found that fluorescent ghrelin mainly labels PVH neurons immunoreactive for nitric oxide synthase 1 (NOS1), which catalyze the production of nitric oxide [NO]). Centrally injected ghrelin increases c-Fos in NOS1 PVH neurons and NOS1 phosphorylation in the PVH. We also found that a high dose of systemically injected ghrelin increases the ghrelin level in the cerebrospinal fluid and in the periventricular PVH, and induces c-Fos in NOS1 PVH neurons. Such a high dose of systemically injected ghrelin activates a subset of NOS1 PVH neurons, which do not express oxytocin, via an arcuate nucleus-independent mechanism. Finally, we found that pharmacological inhibition of NO production fully abrogates ghrelin-induced increase of calcium concentration in corticotropin-releasing hormone neurons of the PVH whereas it partially impairs ghrelin-induced increase of plasma glucocorticoid levels. Thus, plasma ghrelin can directly target a subset of NO-producing neurons of the PVH that is involved in ghrelin-induced activation of the hypothalamic-pituitary-adrenal neuroendocrine axis.

Daily rhythms of diabetogenic factors in men: role of type 2 diabetes and body weight.

Obesity is a major cause of type 2 diabetes. Transition from obesity to type 2 diabetes manifests in the dysregulation of hormones controlling glucose homeostasis and inflammation. As metabolism is a dynamic process that changes across 24 h, we assessed diurnal rhythmicity in a panel of 10 diabetes-related hormones. Plasma hormones were analysed every 2 h over 24 h in a controlled laboratory study with hourly isocaloric drinks during wake. To separate effects of body mass from type 2 diabetes, we recruited three groups of middle-aged men: an overweight (OW) group with type 2 diabetes and two control groups (lean and OW). Average daily concentrations of glucose, triacylglycerol and all the hormones except visfatin were significantly higher in the OW group compared to the lean group (P < 0.001). In type 2 diabetes, glucose, insulin, C-peptide, glucose-dependent insulinotropic peptide and glucagon-like peptide-1 increased further (P < 0.05), whereas triacylglycerol, ghrelin and plasminogen activator inhibitor-1 concentrations were significantly lower compared to the OW group (P < 0.001). Insulin, C-peptide, glucose-dependent insulinotropic peptide and leptin exhibited significant diurnal rhythms in all study groups (P < 0.05). Other hormones were only rhythmic in 1 or 2 groups. In every group, hormones associated with glucose regulation (insulin, C-peptide, glucose-dependent insulinotropic peptide, ghrelin and plasminogen activator inhibitor-1), triacylglycerol and glucose peaked in the afternoon, whereas glucagon and hormones associated with appetite and inflammation peaked at night. Thus being OW with or without type 2 diabetes significantly affected hormone concentrations but did not affect the timing of the hormonal rhythms.

Does ghrelin regulate intestinal motility in rabbits? An in vitro study using isolated duodenal strips

Rabbit duodenum has been used for examining the ability of motilin to cause muscle contraction in vitro. A motilin-related peptide, ghrelin, is known to be involved in the regulation of gastrointestinal (GI) motility in various animals, but its ability to cause rabbit GI contraction have not been well examined. The aim of this study is to clarify the action of rat ghrelin and its interaction with motilin in the rabbit duodenum. The mRNA expression of ghrelin and motilin receptors was also examined using RT-PCR. Rat ghrelin (10−9–10−6 M) did not change the contractile activity of the duodenum measured by the mean muscle tonus and area under the curve of contraction waves. In agreement with this result, the distribution of ghrelin receptor mRNA in the rabbit GI tract varied depending on the GI region from which the samples were taken; the expression level in the duodenum was negligible, but that in the esophagus or stomach was significant. On the other hand, motilin (10−10–10−6 M) caused a concentration-dependent contraction by means of increased mean muscle tonus, and consistently, motilin receptor mRNA was expressed heterogeneously depending on the GI region (esophagus = stomach = colon = rectum < duodenum = jejunum = ileum < cecum). Expression level of motilin receptor was comparable to that of ghrelin receptor in the esophagus and stomach. Pretreatment with ghrelin (10−6 M) prior to motilin did not affect the contractile activity of motilin in the duodenum. In conclusion, ghrelin does not affect muscle contractility or motilin-induced contraction in the rabbit duodenum, which is due to the lack of ghrelin receptors. The present in vitro results suggest that ghrelin might not be a regulator of intestinal motility in rabbits.

Ghrelin Amplifies the Nicotine-Induced Release of Dopamine in the Bed Nucleus of Stria Terminalis (BNST).

Ghrelin is an orexigenic neuropeptide that is known for stimulating the release of growth hormone (GH) and appetite. In addition, ghrelin has been implicated in addiction to drugs such as nicotine. Nicotine is the principal psychoactive component in tobacco and is responsible for the reward sensation produced by smoking. In our previous in vitro superfusion studies, it was demonstrated that ghrelin and nicotine stimulate equally the dopamine release in the rat amygdala, and ghrelin amplifies the nicotine-induced dopamine release in the rat striatum. However, less attention was paid to the actions of ghrelin and nicotine in the bed nucleus of the stria terminalis (BNST). Therefore, in the present study, nicotine and ghrelin were superfused to the BNST of male Wistar rats, and the dopamine release from the BNST was measured in vitro. In order to determine which receptors mediate these effects, mecamylamine, a non-selective nicotinic acetylcholine receptor (nAchR) antagonist, and GHRP-6, a selective growth hormone secretagogue receptor (GHS-R1A) antagonist, were also superfused to the rat BNST. Nicotine significantly increased the release of dopamine, and this effect was significantly inhibited by mecamylamine. Ghrelin increased dopamine release even more significantly than nicotine did, and this effect was significantly inhibited by GHRP-6. Moreover, when administered together, ghrelin significantly amplified the nicotine-induced release of dopamine in the BNST, and this additive effect was reversed partly by mecamylamine and partly by GHRP-6. Therefore, the present study provides a new base of evidence for the involvement of ghrelin in dopamine signaling implicated in nicotine addiction.

Associations of postprandial ghrelin, liver-expressed antimicrobial peptide 2 and leptin levels with body composition, disease progression and survival in patients with amyotrophic lateral sclerosis.

Loss of appetite contributes to weight loss and faster disease progression in amyotrophic lateral sclerosis (ALS). Impairment of appetite control in ALS may include altered production or action of orexigenic (i.e., ghrelin) and anorexigenic (i.e., liver-expressed antimicrobial peptide 2 [LEAP2] and leptin) hormones. We aimed to determine if postprandial circulating ghrelin levels, LEAP2 levels, LEAP2:ghrelin molar ratio and leptin levels differ in ALS patients compared to non-neurodegenerative disease controls, and whether they are associated with disease progression and body composition. In this prospective natural history study, we assessed postprandial plasma levels of ghrelin, LEAP2 and leptin in patients with ALS (cases; n = 46) and controls (controls; n = 43). For cases, measures were compared to changes in body weight, body composition and clinical outcomes. Postprandial ghrelin level was decreased by 52% in cases compared to controls (p = 0.013). LEAP2:ghrelin molar ratio was increased by 249% (p = 0.009), suggesting greater ghrelin resistance. Patients with lower LEAP2:ghrelin tended to have better functional capacity at assessment, as inferred by the ALS Functional Rating Scale-Revised (τ = -0.179, p = 0.086). Furthermore, ghrelin and LEAP2:ghrelin molar ratio correlated with diagnostic delay (ghrelin, τ = 0.223, p = 0.029; LEAP2:ghrelin, τ = -0.213, p = 0.037). Baseline ghrelin level, LEAP2 level, LEAP2:ghrelin ratio and leptin level were, however, not predictive of change in functional capacity during follow-up. Also, patients with higher postprandial ghrelin levels (hazard ratio [HR] 1.375, p = 0.048), and lower LEAP2:ghelin ratios (HR 0.828, p = 0.051) had an increased risk of earlier death. Reduced postprandial ghrelin levels, coupled with increased LEAP2:ghrelin molar ratios, suggests a loss of ghrelin action in patients with ALS. Given ghrelin's actions on appetite, metabolism and neuroprotection, reduced ghrelin and greater ghrelin resistance could contribute to impaired capacity to tolerate the physiological impact of disease. Comprehensive studies are needed to explain how ghrelin and LEAP2 contribute to body weight regulation and disease progression in ALS.

Ghrelin and obestatin can promote human ovarian granulosa cell functions and FSH effects

The aim of the present in-vitro experiments was to examine the direct influence of ghrelin and obestatin on viability, proliferation and progesterone release by human ovarian granulosa cells and their response to FSH administration. Human granulosa cells were cultured in presence of ghrelin or obestatin (both at 0, 1, 10 or 100 ng/ml) alone or in the presence of FSH (10 ng/ml). Cell viability, accumulation of proliferation markers PCNA and cyclin B1 and release of progesterone were analyzed by Trypan blue extrusion test, quantitative immunocytochemistry and ELISA. Ghrelin, obestatin and FSH up-regulated all the measured ovarian cell parameters. Moreover, both ghrelin and obestatin promoted all the stimulatory effects of FSH. The obtained results demonstrate the direct stimulatory action of ghrelin, obestatin and FSH on basic ovarian cell functions, as well as the ability of metabolic hormones to improve FSH action on human ovarian cells.

Analysis of Serum Ghrelin Levels and BMI in Obese and Non-Obese Subjects

Obesity is excessive body fat and was associated with the importance of metabolic and endocrine problems in somatotropic secretion in functional obesity. Ghrelin is an acylated peptide hormone produced by the stomach, which is a mediator of the growth hormone secretory receptor. The activity of ghrelin stimulates the release of growth hormone, and appetite and stimulates the metabolism of carbohydrates. Circulating ghrelin levels in healthy people increase during fasting and decrease after meals. This study aims to analyze the difference in ghrelin levels among obese and non-obese subjects. A cross-sectional design research was conducted in August 2022. The samples consisted of obese and non-obese subjects based on Body Mass Index (BMI). Ghrelin levels were measured using the Enzyme-Linked Immunosorbent Assay (ELISA) method. The data were statistically analyzed using the Mann-Whitney and Spearman tests. p&lt;0.05 was reported significant. The samples consisted of 80 obese and non-obese subjects, 39 males and 41 females. There was no difference in ghrelin serum levels in the obese group (1.45±2 ng/mL) compared to the non-obese group (0.67±0.25 ng/mL) with p =0.233 (p&gt;0.05). There was a positive correlation between ghrelin levels and BMI (r=0.247). There was no difference in ghrelin levels between the obese group and the non-obese group, and there was a positive correlation between ghrelin levels and BMI. A higher BMI would lead to higher ghrelin levels.