Search

Context NKX2-2 is a crucial transcription factor that enables specific β-cell gene expression. Nkx2-2(–/–) mice manifest with severe neonatal diabetes and changes in β-cell progenitor fate into ghrelin-producing cells. In humans, recessive NKX2-2 gene mutations have been recently reported as a novel etiology for neonatal diabetes, with only 3 cases known worldwide. This study describes the genetic analysis, distinctive clinical features, the therapeutic challenges, and the unique pathophysiology causing neonatal diabetes in human NKX2-2 dysfunction. Case Description An infant with very low birth weight (VLBW) and severe neonatal diabetes (NDM) presented with severe obesity and developmental delay already at age 1 year. The challenge of achieving glycemic control in a VLBW infant was unexpectedly met by a regimen of 3 daily doses of long-acting insulin analogues. Sanger sequencing of known NDM genes (such as ABCC8 and EIF2AK3) was followed by whole-exome sequencing that revealed homozygosity of a pathogenic frameshift variant, c.356delG, p.P119fs64*, in the islet cells transcription factor, NKX2-2. To elucidate the cause for the severe obesity, an oral glucose tolerance test was conducted at age 3.5 years and revealed undetectable C-peptide levels with a paradoxically unexpected 30% increase in ghrelin levels. Conclusion Recessive NKX2-2 loss of function causes severe NDM associated with VLBW, childhood obesity, and developmental delay. The severe obesity phenotype is associated with postprandial paradoxical ghrelin secretion, which may be related to human β-cell fate change to ghrelin-secreting cells, recapitulating the finding in Nkx2-2(–/–) mice islet cells.

Mechanisms underlying postprandial and obesity-associated plasma ghrelin reductions are incompletely understood. Here, using ghrelin cell-selective insulin receptor-KO (GhIRKO) mice, we tested the impact of insulin, acting via ghrelin cell-expressed insulin receptors (IRs), to suppress ghrelin secretion. Insulin reduced ghrelin secretion from cultured gastric mucosal cells of control mice but not from those of GhIRKO mice. Acute insulin challenge and insulin infusion during both hyperinsulinemic-hypoglycemic clamps and hyperinsulinemic-euglycemic clamps lowered plasma ghrelin in control mice but not GhIRKO mice. Thus, ghrelin cell-expressed IRs are required for insulin-mediated reductions in plasma ghrelin. Furthermore, interventions that naturally raise insulin (glucose gavage, refeeding following fasting, and chronic high-fat diet) also lowered plasma ghrelin only in control mice - not GhIRKO mice. Thus, meal- and obesity-associated increases in insulin, acting via ghrelin cell-expressed IRs, represent a major, direct negative modulator of ghrelin secretion in vivo, as opposed to ingested or metabolized macronutrients. Refed GhIRKO mice exhibited reduced plasma insulin, highlighting ghrelin's actions to inhibit insulin release via a feedback loop. Moreover, GhIRKO mice required reduced glucose infusion rates during hyperinsulinemic-hypoglycemic clamps, suggesting that suppressed ghrelin release resulting from direct insulin action on ghrelin cells usually limits ghrelin's full potential to protect against insulin-induced hypoglycemia.

Ghrelin, one of the most important appetite regulating peptides, is involved in the regulation of energy homeostasis. The anorexia effect of ghrelin in chickens is contrary to that of ghrelin in mammals. In the present study, the effects of feeding status and dietary energy level on plasma total ghrelin levels and expression were studied in broilers. The gene expression of ghrelin and its receptor GHS-R1a were measured in the hypothalamus, proventriculus, duodenum, liver, and abdominal fat pad. The results showed that ghrelin mRNA and GHS-R1a mRNA are moderately expressed in liver and abdominal fat. Ghrelin secretion was increased by fasting and refeeding. The gene expression of ghrelin and GHS-R1a in the hypothalamus, proventriculus, liver, and abdominal fat pad were changed by feeding status and dietary energy level. The results suggest that ghrelin is a signal of energy utilization in chickens. The abundant expression of ghrelin and GHS-R1a in liver and abdominal fat pad may be associated with energy balance.

It is known that heat stress decreases dry matter intake in cattle with impacts on milk production and fertility. Ghrelin is an orexigenic hormone with suppressive effects on reproduction. In this study, we investigated the effects of heat stress and gestational status on ghrelin secretion and its possible associations with DMI in Holstein cattle. The study was conducted in a dairy farm without any artificial cooling measures. The animals were fed a total mixed ration twice daily; each morning the leftovers were removed and weighted. Lactating cows and heifers were used during the winter and the summer; in each season 8 groups were formed as following: non-pregnant cows (n = 10) and non-pregnant heifers (n = 10) and pregnant cows (3 groups, each n = 8) and heifers (3 groups, each n = 10), being at the 1st (days 65-90), the 2nd (days 114-144) and the 3rd (dry cows, days 198-220; heifers, days 192-230) trimester of gestation. In each season the blood samples were collected from all groups on the same day, 1 h prior to morning feeding. In the winter, the Temperature Humidity Index (THI) was 58 in the winter and 73 in the summer. Normal and acidified sera were stored at -20 °C and analyzed for cortisol, total and acylated ghrelin concentrations, respectively. T-Test and Welch-Satterthwaite were performed for continuous data comparison, while two-way ANOVA to test for differences between gestation and season. Feed refusals were higher (p 0.01) during the summer compared to the winter. In cows, total ghrelin levels differed between gestation stages in winter and summer(p 0.04), while acylated ghrelin levels differed by gestation stage in winter (p 0.001) but not in summer. There was an effect of season by the gestational stage in the pattern of acylated (p 0.001) but not of total ghrelin. In heifers, the pattern of total and acylated ghrelin secretion was not affected by season or gestation stage (p 0.05). Both in cows and heifers, acylated ghrelin levels were lower in summer compared to winter, (p 0.002). During the summer months the low ghrelin levels might explain the reduced feed consumption of heat stressed animals. We infer that the lactation-induced altered metabolic status of the animals governed the different ghrelin levels at various gestational stages in cows and heifers.

Objective Ghrelin is an orexigenic peptide hormone involved in the regulation of energy homeostasis, food intake and glucose metabolism. Serum levels increase anticipating a meal and fall afterwards. Underlying genetic mechanisms of the ghrelin secretion are unknown. Methods Total serum ghrelin was measured in 1501 subjects selected from the population-based LIFE-ADULT-sample after an overnight fast. A genome-wide association study (GWAS) was performed. Gene-based expression association analyses (transcriptome-wide association study (TWAS)) are statistical tests associating genetically predicted expression to a certain trait and were done using MetaXcan. Results In the GWAS, three loci reached genome-wide significance: the WW-domain containing the oxidoreductase-gene (WWOX; P = 1.80E-10) on chromosome 16q23.3-24.1 (SNP: rs76823993); the contactin-associated protein-like 2 gene (CNTNAP2; P = 9.0E-9) on chromosome 7q35-q36 (SNP: rs192092592) and the ghrelin And obestatin prepropeptide gene (GHRL; P = 2.72E-8) on chromosome 3p25.3 (SNP: rs143729751). In the TWAS, the three genes where the expression was strongest associated with serum ghrelin levels was the ribosomal protein L36 (RPL36; P = 1.3E-06, FDR = 0.011, positively correlated), AP1B1 (P = 1.1E-5, FDR = 0.048, negatively correlated) and the GDNF family receptor alpha like (GFRAL), receptor of the anorexigenic growth differentiation factor-15 (GDF15), (P = 1.8E-05, FDR = 0.15, also negatively correlated). Conclusions The three genome-wide significant genetic loci from the GWA and the genes identified in the TWA are functionally plausible and should initiate further research.

The stomach is the primary source of the orexigenic and adiposity-promoting hormone, ghrelin. There is emerging evidence on the nutrient-mediated modulation of gastric ghrelin secretion. However, limited information is available on gastric nutrient-sensing mechanisms in high-fat diet (HFD)-induced obesity. This study investigated the impact of HFD-induced obesity on the expression of nutrient chemosensors in mouse stomach, particularly ghrelin cells. Male C57BL/6 mice were fed either a standard laboratory diet (SLD) or HFD for 12 weeks. The expression of ghrelin, enzymes involved in ghrelin production (PC1/3, GOAT) and nutrient chemosensors (CD36, FFAR2&amp, 4, GPR93, CaSR, mGluR4 and T1R3) was determined by quantitative RT-PCR in the mouse corpus and antrum. Immunohistochemistry assessed the protein expression of CaSR and ghrelin in the corpus and antrum. Antral mRNA levels of CaSR and PC1/3 were increased in HFD compared to SLD mice, while mRNA levels of all other nutrient chemosensors examined remained unchanged. CaSR immunolabelling was observed in the gastric antrum only. Nearly 80% of antral ghrelin cells expressed CaSR, with a similar cell density and co-expression in SLD and HFD mice. In conclusion, HFD-induced obesity increased CaSR mRNA expression in mouse antrum. However, the high antral co-expression of CaSR and ghrelin was unaltered in HFD compared to SLD mice.

Background The ability of the gut to detect nutrients is critical to the regulation of gut hormone secretion, food intake, and postprandial blood glucose control. Ingested nutrients are detected by specific gut chemosensors. However, knowledge of these chemosensors has primarily been derived from the intestine, while available information on gastric chemosensors is limited. This study aimed to investigate the nutrient-sensing repertoire of the mouse stomach with particular emphasis on ghrelin cells. Methods Quantitative RT-PCR was used to determine mRNA levels of nutrient chemosensors (protein: G protein-coupled receptor 93 [GPR93], calcium-sensing receptor [CaSR], metabotropic glutamate receptor type 4 [mGluR4]; fatty acids: CD36, FFAR2&4; sweet/umami taste: T1R3), taste transduction components (TRPM5, GNAT2&3), and ghrelin and ghrelin-processing enzymes (PC1/3, ghrelin O-acyltransferase [GOAT]) in the gastric corpus and antrum of adult male C57BL/6 mice. Immunohistochemistry was performed to assess protein expression of chemosensors (GPR93, T1R3, CD36, and FFAR4) and their co-localization with ghrelin. Key results Most nutrient chemosensors had higher mRNA levels in the antrum compared to the corpus, except for CD36, GNAT2, ghrelin, and GOAT. Similar regional distribution was observed at the protein level. At least 60% of ghrelin-positive cells expressed T1R3 and FFAR4, and over 80% expressed GPR93 and CD36. Conclusions and inferences The cellular mechanisms for the detection of nutrients are expressed in a region-specific manner in the mouse stomach and gastric ghrelin cells. These gastric nutrient chemosensors may play a role modulating gastrointestinal responses, such as the inhibition of ghrelin secretion following food intake.

The poor antigenicity of peptide antigens demands the selection of effective adjuvants to induce humoral immunity. The peptides obestatin and ghrelin from the pro-hormone pre-proghrelin were initially identified as antagonistic in regulating feeding behaviour, with obestatin being suppressive. The efficacy of two adjuvant systems, DEAE with the oil polysorbate emulsion of BP85: Span80 and the surfactant-oil system Montanide (ISA 50v) were therefore assessed with an obestatin-ovalbumin conjugate injected into late pregnant sows. This enabled the supply of antibodies directed against obestatin to newborn piglets through colostrum with the objective of promoting ghrelin secretion and therefore increasing feeding behaviour. Pregnant Landrace × Large White sows (n = 28) were immunised with 0.5 mg obestatin-ovalbumin in 2 mL DEAE: BP85: Span80 (DEAE; n = 14) or with 2 mL Montanide (ISA 50v: n = 14) as adjuvants at days 91 and 105 of gestation. After farrowing, piglets remained with their mothers during the lactation period and were weighed after weaning at Day 28. Antibody titres (unitless) in colostrum were assessed by ELISA as 5543 ± 2388 and 3139 ± 1151 for the DEAE and Montanide adjuvants respectively. These were associated with total IgG of 67.7 ± 3 and 82.3 ± 4.8 mg/mL respectively (P = 0.018). Piglet plasma titres were 5100 ± 1576 and 5762 ± 1688 for DEAE and Montanide respectively at Day 5 postpartum. These titres were still detectable through to Day 28 (titres of 1213 ± 389 and 665 ± 203 respectively (P = 0.176). However, sow colostral antibody titres were not related to piglet antibody concentrations on D5 (r = -0.225, P = 0.341). Sow plasma antibody titres were not related to titres at Day 28 in piglets across treatments (r = 0.198, P = 0.402). The concentration of ghrelin in colostrum was 672 ± 78 and 666 ± 39 pg/mL for the DEAE and Montanide groups, respectively, leading to piglet plasma concentrations on Day 5 of 1105 ± 164 and 530 ± 84 pg/mL (P = 0.002). Animals grew from birthweights of 1.7 ± 0.1 and 1.8 ± 0.1 (P = 0.993) to 7.7 ± 1.2 and 7.8 ± 1.0 kg (P = 0.295) at weaning, representing growth rates of 200.5 ± 52.9 and 225.5 ± 53.4 g/day (P = 0.181). There was a significant negative correlation between piglet D28 antibody titre and growth rate to weaning with the Montanide adjuvant (r = 0.116, P = 0.035) but not for the DEAE (r = -0.118, P = 0.411). Although both adjuvants were capable of generating high antibody titres, the DEAE dextran was likely to be the most effective adjuvant to induce a humoral immune response to develop further with a commercial vaccine. Refereed/Peer-reviewed

Objective: Ghrelin is an orexigenic peptide hormone involved in the regulation of energy homeostasis, food intake and glucose metabolism. Serum levels increase anticipating a meal and fall afterwards. Underlying genetic mechanisms of the ghrelin secretion are unknown. Methods: Total serum ghrelin was measured in 1501 subjects selected from the population-based LIFE-ADULT-sample after an overnight fast. A genome-wide association study (GWAS) was performed. Gene-based expression association analyses (transcriptome-wide association study (TWAS)) were done using MetaXcan. Results: In the GWAS, three loci reached genome-wide significance: the WW-domain containing the oxidoreductase-gene (WWOX; p=1.80E-10) on chromosome 16q23.3-24.1 (SNP: rs76823993); the Contactin-Associated Protein-Like 2 gene (CNTNAP2; p=9.0E-9) on chromosome 7q35-q36 (SNP: rs192092592) and the Ghrelin And Obestatin Prepropeptide gene (GHRL; p = 2.72E-8) on chromosome 3p25.3 (SNP: rs143729751). In the TWAS, serum ghrelin was negatively associated with RNA expression of the GDNF Family Receptor Alpha Like (GFRAL), receptor of the anorexigenic Growth Differentiation Factor-15 (GDF15), (z-score=-4.288, p=1.81E-05). Furthermore, ghrelin was positively associated with Ribosomal Protein L36 (RPL36; z-score=4.848, p=1.25E-06). Conclusions: Our findings provide evidence of a link between two major players of weight regulation, the ghrelin system and the GDF15/GFRAL-pathway. Funding Statement: This work was supported by LIFE − Leipzig Research Center for Civilization Diseases, University of Leipzig. LIFE is funded by means of the European Union, by means of the European Social Fund (ESF), by the European Regional Development Fund (ERDF), and by means of the Free State of Saxony within the framework of the excellence initiative. Declaration of Interests: The authors have nothing to disclose. Ethics Approval Statement: The procedures were conducted according to the Declaration of Helsinki and approved by the ethics committee of the University of Leipzig (registration-number: 263-2009-14122009).

Hunger is defined as a craving or urgent need for food. Abundant evidence now indicates that homeostatic and cognitive mechanisms promote the sensation of hunger. Communication between the gastrointestinal (GI) tract and the central nervous system (CNS) regulate both homeostatic and cognitive mechanisms to control feeding behavior. In this context the GI derived feeding peptide ghrelin, targets the CNS to promote food anticipation, learning, hedonic feeding and motivation for food. Importantly meal expectation following nutrient deprivation or satiation is associated with elevation of plasma ghrelin, highlighting the propensity of each mechanism to stimulate GI ghrelin secretion. It is well established that multiple physiological processes control ghrelin secretion from the GI tract. For example activation of descending sympathetic and parasympathetic pathways, GI feeding peptides, metabolic factors and endocannabinoid signaling mechanisms all regulate ghrelin secretion. In parallel, activation of the CNS ghrelin receptor (GHSR-1a) controls food anticipation, food-based learning, spatial learning and the rewarding properties of food. Notably GHSR-1a is expressed within a network of CNS regions that regulate diverse aspects of feeding behavior. These examples suggest a redundancy regarding mechanisms that control GI ghrelin secretion and complexity for GHSR-1a-mediated regulation of food intake. Based on this collective data, we suggest that learned information linked to the receipt of food is transmitted from the CNS to the GI tract to stimulate ghrelin release. We further postulate that GI ghrelin release and ghrelin-GHSR-1a interactions adapt over time, metabolic status and environment to direct feeding behavior.

The mycotoxin deoxynivalenol (DON) generally exists in cereals and affects human and animal health. The aim of this study is to analyze the impacts of DON in naturally contaminated feed on piglet growth performance and intestinal hormone secretion in the short term. We randomly divided 5-week-old piglets into four groups: Control, DON 1,000, DON 2,000 and DON 3,000 groups. Piglets received a feed naturally contaminated with DON (approximately 400, 1,000, 2,000 or 3,000 μg/kg) for 21 days. Body weight showed no significant difference following exposure to DON. The balance of anti-oxidation and oxidation was disrupted by DON after 21 days. The concentration of tumor necrosis factor-alpha (TNF-α) and cyclooxgenase-2 (COX-2) significantly increased (p

Aims This study investigated the nutrient-mediated modulation of total ghrelin (TG) and acyl ghrelin (AG) secretion from the mouse gastric mucosa, and the role of long-chain fatty acid chemosensors, FFAR4 and CD36, in lipid-mediated modulation of TG and AG release. Methods Ex-vivo experiments were conducted using mouse gastric mucosa to examine the effects of nutrients (D-glucose, L-phenylalanine, peptone (mixture of oligopeptides & single amino acids), D-mannitol, α-linolenic acid and fat emulsion (intralipid)) on TG and AG secretion. Additionally, inhibition of FFAR4 and CD36 on α-linolenic acid and intralipid-mediated regulation of TG and AG secretion was assessed. Results TG and AG secretion were unaffected by glucose and D-mannitol. Peptone stimulated the release of TG and AG. In contrast, L-phenylalanine reduced AG secretion only. Intralipid reduced TG secretion and stimulated AG secretion, and α-linolenic acid reduced AG release, without affecting TG mobilisation. Modulation of ghrelin secretion by lipids occurred in an FFAR4 and CD36-independent manner. Conclusion Ghrelin secretion is modulated in a nutrient-specific manner by proteins and lipids, with TG and AG displaying independent responses to the same stimuli. In addition, FFAR4 and CD36 do not participate in modulation of TG and AG secretion by α-linolenic acid and intralipid.

Some probiotics have been shown to alleviate age-related muscle atrophy via the gut-muscle axis. The aim of this study was to investigate the effects of live or heat-killed Lactobacillus paracasei PS23 (PS23) on muscle health in D-galactose-induced aging mice. Administration of D-galactose significantly reduced the strength, size, and levels of phosphorylated Akt in the muscle of mice. These effects were ameliorated by both live and heat-killed PS23 supplementation. Ghrelin is a multifaceted gut hormone with the ability to improve muscle atrophy. The levels of ghrelin in the serum and stomach of the aging mice were also significantly reduced and could be rescued by heat-killed but not live PS23. Furthermore, heat-killed PS23 greatly stimulated ghrelin secretion in the KATO III human gastric cell line. In conclusion, PS23 is a potential dietary supplement that can alleviate age-related muscle loss and dysfunction by regulating ghrelin secretion.

Ghrelin, an endogenous peptide isolated from the stomach, is known to stimulate food intake after peripheral administration. We found that the enzymatic digest of β-lactoglobulin decreases ghrelin secretion from the ghrelin-producing cell line MGN3-1. The peptides present in the digest were comprehensively analyzed using the nanoLC-OrbitrapMS. Among them, we identified that the nonapeptide LIVTQTMKG, corresponding to β-lactoglobulin(1-9), suppresses ghrelin secretion from MGN3-1 cells. We named LIVTQTMKG 'lacto-ghrestatin'. We found that lacto-ghrestatin decreases intracellular cAMP levels and mRNA expression levels of ghrelin production-related genes in MGN3-1 cells. Orally administered lacto-ghrestatin decreases plasma ghrelin levels and food intake in fasted mice. Lacto-ghrestatin is the first food-derived peptide to suppress ghrelin secretion in vitro and in vivo.

It is known that exists a relationship between listening to music and food intake. Hypothalamus appears to integrate the orexigenic properties of a novel peptide, ghrelin (Ghre) that induces food intake through neuropeptide Y (NPY). Ghre stimulates appetite by acting on the ventral hypothalamus, which controls food intake. Ghre is secreted from the stomach and circulates in the bloodstream under fasting conditions, sending a hunger signal from the periphery to the Central Nervous System. The aim of this study was to evaluate, in the rat, the effects of different musical frequencies (432 and 440 Hz) on the Ghre and NPY expression in the hypothalamic neurons through immunohistochemistry; in addition, we investigated on the different production of Ghre in the serum through Western blot assay (Wb), in relation to the body weight of animals. Ghre-immunopositive cells were counted, showing a significant increase in music-treated compared to the control (CTR) group. Similarly, music-treated rats showed increased levels of Ghre in the serum compared to CTR animals. Finally, the body weight of animals was affected by music. In particular, music exposure was able to stimulate the body weight increase and, interestingly, the increase was higher when animals were exposed to music at 440 Hz. Together, the results strongly support the hypothesis that different musical frequencies could affect food intake by modulating the hypothalamic Ghre expression and its release.

Gut hormones send information about incoming nutrients to the rest of the body and thereby control many aspects of metabolism. The secretion of ghrelin and glucagon-like protein (GLP)-1, two hormones with opposite secretory patterns and opposite actions on multiple targets, is controlled by a limited number of G-protein coupled receptors (GPCRs); half of which recognize and bind dietary nutrient metabolites, metabolites generated by gut microbiota, and metabolites of the host's intermediary metabolism. Most metabolite GPCRs controlling ghrelin secretion are inhibitory, whereas all metabolite receptors controlling GLP-1 secretion are stimulatory. This dichotomy in metabolite sensor function, which is obtained through a combination of differential expression and cell-dependent signaling bias, offers pharmacological targets to stimulate GLP-1 and inhibit ghrelin through the same mechanism.

Obesity, insulin resistance and the metabolic syndrome are associated with changes to the gut microbiota; however, the mechanism by which modifications to the gut microbiota might lead to these conditions is unknown. Here we show that increased production of acetate by an altered gut microbiota in rodents leads to activation of the parasympathetic nervous system, which, in turn, promotes increased glucose-stimulated insulin secretion, increased ghrelin secretion, hyperphagia, obesity and related sequelae. Together, these findings identify increased acetate production resulting from a nutrient-gut microbiota interaction and subsequent parasympathetic activation as possible therapeutic targets for obesity.

Ghrelin is a metabolic hormone that promotes energy conservation by regulating appetite and energy expenditure. Although some studies suggest that antagonizing ghrelin function attenuates body weight gain and glucose intolerance on a high calorie diet, there is little information about the metabolic actions of ghrelin in the obese state. In this review, we discuss the novel concept of obesity-induced central ghrelin resistance in neural circuits regulating behavior, and impaired ghrelin secretion from the stomach. Interestingly, weight loss restores ghrelin secretion and function, and we hypothesize that ghrelin resistance is a mechanism designed to protect a higher body weight set-point established during times of food availability, to maximize energy reserves during a time of food scarcity.

In this study we compare the interaction of three protein sources&mdash, insect, beef, and almond&mdash, with the gastrointestinal tract. We measured the enterohormone secretion ex vivo in human and pig intestine treated with in vitro digestions of these foods. Insect and beef were the most effective in inducing the secretion of CCK, while almond was the most effective in inducing PYY in pig duodenum. In the human colon, almond was also the most effective in inducing PYY, and GLP-1 levels were increased by insect and beef. The three digested proteins reduced ghrelin secretion in pig duodenum, while only insect reduced ghrelin secretion in human colon. We also found that food intake in rats increased in groups fed a raw insect pre-load and decreased when fed raw almond. In conclusion, the insect Alphitobius diaperinus modulates duodenal and colonic enterohormone release and increases food intake in rats. These effects differ from beef and almond.

Background. Obesity in children makes the higher risk of micronutrients deficiency, increase profile lipid, and promote cell inflammation. Some studies report that gut microbiota may have roles in body metabolism include obesity. Our study aimed to compare the number of Lactobacillus, Bifidobacteria, Escherichia coli, and Enterobacter between obese, normal, and wasted children. Methods. The study was performed in 115 healthy children in West Lombok, West Nusa Tenggara, Indonesia. The total number of bacteria was counted using a culture technique with selective media and total plate count method. Dietary intake assessed to all subjects using a semi-quantitative food frequency questionnaire. Data were analyzed using one-way ANOVA between three groups. Results. The result showed a significant difference in the number of Escherichia coli between obese, normal, and wasted children (p= 0.02), meanwhile there were no significant differences of dietary intake and the number of Lactobacillus, Enterobacter, and Bifidobacteria between the three groups. A potential mechanism by which dysbiosis may cause obesity is its ability to produce short-chain fatty acid (SCFA) by fermentation in the colon. It may increase gut permeability, ghrelin secretion, or bind to toll-like-receptor which leads to enhancement of free fatty acid, cholesterol, and adipose tissue synthesis. Conclusion. Dysbiosis often happened in obese children. Obese children tend to have an imbalance of gut microbiota. However, it needs further study to assess the effects of certain gut microbiota on dietary intake and their effects on obesity cases among children. Keywords: children, dysbiosis, gut microbiota, obesity

Ghrelin is one of the most important appetite regulating peptides, involved in the regulation of energy homeostasis. The role of ghrelin on the appetite and fat metabolism in chickens is different from that of ghrelin in mammals. Glucocorticoids and insulin are important hormones and work differently in energy regulation of body. In this study, the effects of dexamethasone (DEX, 2.0 mg/kg BW), subcutaneous insulin injection (40 µg/kg BW), and glucose load on ghrelin secretion and expression were determined in broilers. DEX treatment increased circulating ghrelin concentration in broiler fed with either a low-energy diet (11.05 MJ/kg of metabolizable energy) or a high-energy diet (14.44 MJ/kg of metabolizable energy). The expression levels of ghrelin were increased while both ghrelin and its receptor GHS-R1a expression levels were stimulated by DEX. A single subcutaneous insulin injection (40 µg/kg BW) or oral glucose infusion (2 g/kg BW) rise circulating ghrelin level. Ghrelin expression in the proventriculus was increased by insulin treatment but unchanged by glucose load. DEX had no detectable influence on ghrelin and GHS-R1a expression in the hypohtalamus, whereas insulin suppressed their expression. In conclusion, both insulin and glucocorticoid stimulate ghrelin secretion in chickens, in contrast to mammals. Glucocorticoids evoke peripheral ghrelin/GHS-R1a system while insulin increases peripheral ghrelin expression and suppress the activation of central ghrelin/GHS-R1a system. The result suggests that ghrelin involved in the modulating network of energy homeostasis in concert with glucocorticoids and insulin.

In two experiments, we studied (a) the changes of LH secretion in heifers under different feeding schedules and (b) total ghrelin concentration at oestrus in cows and heifers. In experiment one, synchronized heifers were allocated in three groups (R, regularly fed controls; F, fasted; and F-F fasted-fed). One day after the completion of the oestrous induction protocol, group F and F-F animals stayed without feed for 24 hr; thereafter, feed was provided to R and F-F cattle; 2 hr later, GnRH was administered to all animals. Blood samples were collected for ghrelin, progesterone, LH and cortisol concentrations. Fasting caused increased ghrelin concentrations in groups F and F-F, while in response to GnRH, LH surge was significantly attenuated in groups F and F-F compared to R. In experiment 2, lactating cows and heifers were used. On day 9 of a synchronized cycle, PGF2α was administered, and blood samples were collected twice daily until the third day after oestrus and analysed for progesterone, estradiol, ghrelin, glucose and BHBA concentrations. No difference was recorded between groups in steroids and BHBA concentrations. In comparison to mid-luteal values, ghrelin concentrations significantly increased at perioestrual period in cows, but not in heifers. This study provides evidence that starving-induced elevated ghrelin concentrations can have suppressing effect on LH secretion, even after ghrelin's restoration to basal values and that during oestrus, ghrelin secretion is differently regulated in cows and heifers, likely being independent from oestradiol concentrations. Further research is required to identify the determining factors that drive the different regulation of ghrelin secretion in cows and heifers.

Electroacupuncture (EA) accelerates intestinal functional recovery in sepsis. The present study investigated ghrelin and ghrelin receptor (GSH-R) levels during EA in rats with acute bowel injury (ABI). Rats were grouped into four groups: Sham, ABI, ABI+EA and ABI+GHRA+EA (n=12 per group). ABI was induced by cecal ligation and puncture (CLP). EA on bilateral Zusanli acupoints was performed following CLP. GSH-R blocker (GHRA) was used following CLP but prior to EA for ABI+GHRA+EA rats. Rats were sacrificed 12 h following CLP. Serum ghrelin, tumor necrosis factor-α (TNF-α) and high mobility group box 1 (HMGB1) levels, as well as ghrelin and GSH-R protein expression, water content, pathological changes and myeloperoxidase (MPO) and diamine oxidase (DAO) activities in the bowel tissues, were measured. ABI rats, compared with the sham rats, had significantly lower levels of ghrelin and GSH-R in the serum and bowel tissue, and higher Chiu's score (all P

Long-term treatment with the ghrelin receptor antagonist [d-Lys3]-GHRP-6 does not improve glucose homeostasis in nonobese diabetic MKR mice. Am J Physiol Regul Integr Comp Physiol 314: R71–R83, 2018. First published September 13, 2017; doi: 10.1152/ajpregu.00157.2017 .—Ghrelin secretion has been associated with increased caloric intake and adiposity. The expressions of ghrelin and its receptor (GHS-R1a) in the pancreas has raised the interest about the role of ghrelin in glucose homeostasis. Most of the studies showed that ghrelin promoted hyperglycemia and inhibited insulin secretion. This raised the interest in using GHS-R1a antagonists as therapeutic targets for type 2 diabetes. Available data of GHS-R antagonists are on a short-term basis. Moreover, the complexity of GHS-R1a signaling makes it difficult to understand the mechanism of action of GHS-R1a antagonists. This study examined the possible effects of long-term treatment with a GHS-R1a antagonist, [d-Lys3]-growth hormone-releasing peptide (GHRP)-6, on glucose homeostasis, food intake, and indirect calorimetric parameters in nonobese diabetic MKR mice. Our results showed that [d-Lys3]-GHRP-6 (200 nmol/mouse) reduced pulsatile growth hormone secretion and body fat mass as expected but worsened glucose and insulin intolerances and increased cumulative food intake unexpectedly. In addition, a significant increase in blood glucose and decreases in plasma insulin and C-peptide levels were observed in MKR mice following long-term [d-Lys3]-GHRP-6 treatment, suggesting a direct inhibition of insulin secretion. Immunofluorescence staining of pancreatic islets showed a proportional increase in somatostatin-positive cells and a decrease in insulin-positive cells in [d-Lys3]-GHRP-6-treated mice. Furthermore, [d-Lys3]-GHRP-6 stimulated food intake on long-term treatment via reduction of proopiomelanocortin gene expression and antagonized GH secretion via reduced growth hormone-releasing hormone gene expression in hypothalamus. These results demonstrate that [d-Lys3]-GHRP-6 is not completely opposite to ghrelin and may not be a treatment option for type 2 diabetes.

Ethno-pharmacological relevance Traditional Chinese medicine (TCM) is commonly provided to cancer patients, however, the patterns of prescriptions for this type of medicine in Taiwan are unclear. This study aimed to evaluate the use of traditional Chinese medicine products in colon cancer patients post-surgery in Taiwan and to research patterns of TCM. Material and Methods This was a cross-sectional study of newly diagnosed colon cancer patients who received surgery between 2004 and 2008 identified from the National Health Insurance Research Database of Taiwan. The prescription patterns and reasons for the use of TCM for colon cancer were analyzed. Results The results showed that “symptoms, signs and ill-defined conditions” (23.3%) and diseases of the digestive system (16.9%) were the most common reasons for using Chinese herbal medicine. Xiang-sha-liu-jun-zi-tang (7.1%), Bu-zhong-yi-qi-tang (4.3%), Jia-wei-xiao-yao-san (4.1%), Shen-Ling-Bai-Zhu-San (3.7%), Ban-Xia-Xie-Xin-Tang (3.4%), Gui-pi-tang (2.4%), Ping-Wei-San (2.4%), Gan-Lu-Yin (2.0%), Bao-He-Wan (1.9%), and Zhen-Ren-Huo-Ming-Yin (1.8%) were the most commonly prescribed single Chinese herbal formulae (CHF) for colon cancer patients post-surgery. Hedyotis diffusa Willd (Bai Hua She She Cao) (5.1%) and Scutellaria barbata (Ban Zhi Lian )(4.8%) were the most commonly prescribed single Chinese herbs. Conclusions This study identified patterns of TCM use in colon cancer patients post-surgery in Taiwan. The herbal ingredients were most commonly used for stimulate ghrelin secretion to increase food intake and had potential anti-tumor effect. However, further research is required to evaluate any beneficial effects which could identify leads for the development of new treatment strategies using TCM.

Carbohydrate administration decreases plasma levels of the 'hunger hormone' ghrelin. The ghrelin cell is co-localized with the sweet taste receptor subunit, TAS1R3, and the gustatory G-protein, gustducin, both involved in the sensing of sweeteners by entero-endocrine cells. This study investigated the role of gustducin-mediated sweet taste receptor signaling on ghrelin secretion in a gastric ghrelinoma cell line, tissue segments and mice. The monosaccharide d-glucose and low-intensity sweetener oligofructose (OFS) decreased (p < 0.001) ghrelin secretion while the high-intensity sweetener sucralose increased (p < 0.001) ghrelin secretion in vitro. These effects were not mediated via the sweet taste receptor or glucose transporters (the sodium-dependent glucose cotransporter SGLT-1 and GLUT2). The effect of these compounds was mimicked ex vivo in gastric and jejunal segments from both wild type (WT) and α-gustducin knockout (α-gust(-/-)) mice. In vivo, the sensing of d-glucose was polarized since intragastric but not intravenous administration of d-glucose decreased (p < 0.05) ghrelin levels in an α-gustducin independent manner which involved inhibition of duodenal ghrelin release. In contrast, neither OFS nor sucralose affected ghrelin secretion in vivo. In conclusion, α-gustducin-mediated sweet taste receptor signaling does not play a functional role in the sensing of carbohydrates, or low- or high-intensity sweeteners by the ghrelin cell. ispartof: Nutrients vol:8 issue:12 ispartof: location:Switzerland status: published

Ghrelin is a peptide hormone produced mainly in the stomach that has widespread tissue distribution and diverse hormonal, metabolic and cardiovascular activities. The circulating ghrelin concentration increases during fasting and decreases after food intake. Ghrelin secretion may thus be initiated by food intake and is possibly controlled by nutritional factors. Lean subjects have increased levels of circulating ghrelin compared with obese subjects. Recent reports show that low plasma ghrelin is associated with elevated fasting insulin levels, insulin resistance and type 2 diabetes mellitus. Factors involved in the regulation of ghrelin secretion have not yet been defined; however, it is assumed that blood glucose levels represent a significant regulator. Recent evidence indicates that ghrelin can increase myocardial contractility, enhance vasodilatation, and has protective effect from myocardial damage. It has been shown that ghrelin may improve cardiac function through growth hormone (GH)-dependent mechanisms but there is also evidence to suggest that ghrelin's cardioprotective activity is independent of GH. Recent data demonstrate that ghrelin can influence key events in atherogenesis. Thus, ghrelin may be a new target for the treatment of some cardiovascular diseases. In this review, we consider the current literature focusing on ghrelin as a potential antiatherogenic agent in the treatment of various pathophysiological conditions.

Patients with multiple system atrophy (MSA) often have evidence of compromised gastrointestinal motility. Ghrelin is a gut hormone that influences gastrointestinal motility in humans. The aim of this study was to determine whether ghrelin secretion is affected in MSA patients, and to investigate the relation between ghrelin secretion and gastrointestinal symptoms. Plasma levels of active ghrelin and unacylated ghrelin were measured in patients with MSA (n = 30), other atypical parkinsonian disorders including progressive supranuclear palsy-Richardson syndrome and corticobasal syndrome (n = 24), and control subjects (n = 24) using enzyme-linked immunosorbent assays. Gastrointestinal symptoms were quantified in all subjects using a self-report questionnaire. The ratio of active ghrelin to total ghrelin in the plasma (active ghrelin ratio) was lower in patients with MSA (mean: 8.0 %) than in patients with other atypical parkinsonian disorders (mean: 13.7 %, P = 0.001) and control subjects (mean: 13.9 %, P = 0.001). The active ghrelin ratio was correlated with the severity of gastrointestinal symptoms in MSA (r = −0.5, P = 0.004). Our observations indicate that ghrelin secretion is affected in patients with MSA. The low active ghrelin ratio may contribute to gastrointestinal symptoms in MSA.

Nutrient ingestion triggers numerous changes in gastrointestinal (GI) peptide hormone secretion that affect appetite and eating. Evidence for these effects comes from research in laboratory animals, healthy humans, and, increasingly, obese patients after Roux-en-Y gastric bypass (RYGB) surgery, which has marked effects on GI hormone function and is currently the most effective therapy for morbid obesity. Increases in cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and peptide tyrosine tyrosine (PYY) and decreases in ghrelin secretion after meals are triggered by changes in the nutrient content of the intestine. One apparent physiological function of each is to initiate a reflex-like feedback control of eating. Here we briefly review this function, with an emphasis on the controls of their secretion. Each is secreted from enteroendocrine cells that are directly or indirectly affected by caloric load, macronutrient composition, and other characteristics of ingested food such as fatty acid chain length. In addition, digestive hydrolysis is a critical mechanism that controls their secretion. Although there are relatively few data in agricultural animals, the generally consistent results across widely divergent mammals suggests that most of the processes described are also likely to be relevant to GI hormone functions and eating in agricultural animals.

Review [Abstract] The aim of this review is to summarize the physiological and pharmacological aspects of ghrelin. Obesity can be defined as an excess of body fat and is associated with significant disturbances in metabolic and endocrine function. Obesity has become a worldwide epidemic. In obesity there is a decreased growth hormone (GH) secretion, and the altered somatotroph secretion in obesity is functional. Ghrelin is a peptide that has a unique structure with 28 amino-acids and an n-octanoyl ester at its third serine residue, which is essential for its potent stimulatory activity on somatotroph secretion. The pathophysiological mechanism responsible for GH hyposecretion in obesity is probably multifactorial, and there is probably a defect in ghrelin secretion. Ghrelin is the only known circulating orexigenic factor, and has been found to be reduced in obese humans. Ghrelin levels in blood decrease during periods of feeding. Due to its orexigenic and metabolic effects, ghrelin has a potential benefit in antagonizing protein breakdown and weight loss in catabolic conditions such as cancer cachexia, renal and cardiac disease, and age-related frailty. Theoretically ghrelin receptor antagonists could be employed as anti-obesity drugs, blocking the orexigenic signal. By blocking the constitutive receptor activity, inverse agonists of the ghrelin receptor may lower the set-point for hunger, and could be used for the treatment of obesity. In summary, ghrelin secretion is reduced in obesity, and could be partly responsible for GH hyposecretion in obesity, ghrelin antagonist or partial inverse agonists should be considered for the treatment of obesity.

Serum ghrelin concentration is generally reduced in obesity. We aimed to assess whether this alteration is present in rats predisposed to obesity because of moderate undernutrition during gestation, and to explore whether this could be related with alterations in stomach sympathetic innervation, which is involved in gastric ghrelin secretion. Offspring of control and 20% gestational calorie-restricted dams (CR) exposed to normal-fat-diet from weaning onward were studied. Circulating ghrelin levels were measured at 25 days and 4 months of age. Morphometry, number of ghrelin-positive (ghrelin + ) cells, ghrelin mRNA and protein levels, and tyrosine hydroxylase (TH) protein levels in stomach were determined at 25 days. Adult CR male animals, but not females, exhibited greater body-weight (BW) than their controls, but both males and females showed lower circulating ghrelin levels. This alteration in ghrelin levels was already present at 25 days, prior to any difference in BW. At this juvenile age, no differences in gastric morphometry, number of ghrelin + cells or ghrelin mRNA/protein levels were found between control and CR animals, however, CR animals showed lower TH stomach content. These results suggest that circulating ghrelin concentration is early altered in rats prenatally programmed to develop obesity. This does not seem to be associated with lower ghrelin production capacity but with specific alterations in sympathetic drive to the stomach.

Ghrelin is a novel growth hormone-releasing peptide, originally identified in the rat stomach as the endogenous ligand for the growth hormone secretagogue-receptor (GHS-R1a). Ghrelin is involved in the regulation of GH release, but it has recently been suggested that ghrelin may have other actions, including effects on appetite, carbohydrate metabolism, heart, kidney, pancreas, gonads, and cell proliferation. The distribution of ghrelin, its functional receptor (type 1a) and the unspliced, non-functional GHS-R type 1b mRNA expression was investigated in various human tissues using classical and real-time reverse transcription and polymerase chain reaction. GHS-R1a was predominantly expressed in the pituitary and at much lower levels in the thyroid gland, pancreas, spleen, myocardium and adrenal gland. In contrast, ghrelin was found in the stomach, other parts of the gut and, indeed, in all the tissues studied (adrenal gland, atrium, breast, buccal mucosa, esophagus, Fallopian tube, fat tissue, gall bladder, human lymphocytes, ileum, kidney, left colon, liver, lung, lymph node, muscle, muscle, myocardium, ovary, pancreas, pituitary, placenta, prostate, right colon, skin, spleen, testis, thyroid, and vein). GHS-R1b expression was also widespread in all tissues studied. The significance of the widespread tissue distribution of ghrelin remains to be determined. These data suggest that ghrelin might have widespread physiological effects via different, partly unidentified, subtypes of the GHS-R in endocrine and non-endocrine tissues.

Ghrelin is a 28-amino acid (aa) stomach-derived peptide discovered in 1999 as the endogenous ligand for growth hormone secretagogue-receptor (GHS-R). Ghrelin-producing cells constitute a distinct group of endocrine cells dispersed throughout the gastric mucosa and to a lesser extent in the small intestine and the endocrine pancreas. Ghrelin plasma levels rise during fasting and chronic caloric restriction to stimulate food intake and fat storage and to prevent life-threatening falls in blood glucose. Plasma ghrelin levels decrease after a meal is consumed and in conditions of energy surplus (such as obesity). Ghrelin has emerged as a key player in the regulation of appetite and energy homeostasis. Ghrelin achieves these functions through binding the ghrelin receptor GHS-R in appetite-regulating neurons and in peripheral metabolic organs including the endocrine pancreas. Ghrelin levels are negatively correlated with body mass index (BMI) and insulin resistance. In addition, ghrelin secretion is impaired in obesity and insulin resistance. Several studies highlight an important role for ghrelin in glucose homeostasis. Genetic, immunological, and pharmacological blockade of ghrelin signaling resulted in improved glucose tolerance and insulin sensitivity. Furthermore, exogenous ghrelin administration was shown to decrease glucose-induced insulin release and increase glucose level in both humans and rodents. GHS-R was shown to be expressed in pancreatic β-cells and ghrelin suppressed insulin release via a Ca2+-mediated pathway. In this review, we provide a detailed summary of recent advances in the field that focuses on the role of insulin and insulin resistance in the regulation of ghrelin secretion and on the role of ghrelin in glucose-stimulated insulin secretion (GSIS).

Ghrelin is an orexigenic gastric peptide hormone secreted when caloric intake is limited. Ghrelin also regulates blood glucose, as emphasized by the hypoglycemia that is induced by caloric restriction in mouse models of deficient ghrelin signaling. Here, we hypothesized that activation of β1-adrenergic receptors (β1ARs) localized to ghrelin cells is required for caloric restriction-associated ghrelin release and the ensuing protective glucoregulatory response. In mice lacking the β1AR specifically in ghrelin-expressing cells, ghrelin secretion was markedly blunted, resulting in profound hypoglycemia and prevalent mortality upon severe caloric restriction. Replacement of ghrelin blocked the effects of caloric restriction in β1AR-deficient mice. We also determined that treating calorically restricted juvenile WT mice with beta blockers led to reduced plasma ghrelin and hypoglycemia, the latter of which is similar to the life-threatening, fasting-induced hypoglycemia observed in infants treated with beta blockers. These findings highlight the critical functions of ghrelin in preventing hypoglycemia and promoting survival during severe caloric restriction and the requirement for ghrelin cell-expressed β1ARs in these processes. Moreover, these results indicate a potential role for ghrelin in mediating beta blocker-associated hypoglycemia in susceptible individuals, such as young children.

To determine the comprehensive G protein-coupled receptor (GPCR) expression profile in ghrelin-producing cells and to elucidate the role of GPCR-mediated signaling in the regulation of ghrelin secretion, we determined GPCR expression profiles by RNA sequencing in the ghrelin-producing cell line MGN3-1 and analyzed the effects of ligands for highly expressed receptors on intracellular signaling and ghrelin secretion. Expression of selected GPCRs was confirmed in fluorescence-activated cell-sorted fluorescently tagged ghrelin-producing cells from ghrelin-promoter CreERT2/Rosa-CAG-LSL-ZsGreen1 mice. Expression levels of GPCRs previously suggested to regulate ghrelin secretion including adrenergic-β1 receptor, GPR81, oxytocin receptor, GPR120, and somatostatin receptor 2 were high in MGN3-1 cells. Consistent with previous reports, isoproterenol and oxytocin stimulated the Gs and Gq pathways, respectively, whereas lactate, palmitate, and somatostatin stimulated the Gi pathway, confirming the reliability of current assays. Among other highly expressed GPCRs, prostaglandin E receptor 4 agonist prostaglandin E2 significantly stimulated the Gs pathway and ghrelin secretion. Muscarine, the canonical agonist of cholinergic receptor muscarinic 4, stimulated both the Gq and Gi pathways. Although muscarine treatment alone did not affect ghrelin secretion, it did suppress forskolin-induced ghrelin secretion, suggesting that the cholinergic pathway may play a role in counterbalancing the stimulation of ghrelin by Gs (eg, by adrenaline). In addition, GPR142 ligand tryptophan stimulated ghrelin secretion. In conclusion, we determined the comprehensive expression profile of GPCRs in ghrelin-producing cells and identified two novel ghrelin regulators, prostaglandin E2 and tryptophan. These results will lead to a greater understanding of the physiology of ghrelin and facilitate the development of ghrelin-modulating drugs.

Ghrelin is a 28 amino acid acylated peptide originally characterised for its capacity to stimulate growth hormone secretion. Ghrelin is also an orexigenic and adipogenic hormone and is thought to be a signal to increase locomotor activity in anticipation of a scheduled meal. Although ghrelin is considered to be up-regulated during fasting, there are still conflicting data regarding the impact of starvation on ghrelin secretion. To test whether the secretory pattern of acylated ghrelin is altered during fasting, plasma levels were monitored every 20 min for 6 h in freelybehaving rats at the light ⁄ dark cycle transition, when animals initiate feeding and activity and use preferentially free fatty acids (FFA) as a source of energy. Rats were fed ad lib. or fasted at dark onset for 24, 48 or 72 h, with or without refeeding rate. The anticipatory rise in ghrelin levels, as well as home-cage activity at the onset of darkness, was significantly reduced from 48 h of fasting compared to ad lib. conditions. A delayed ghrelin peak, sensitive to renutrition, was observed in fasted animals. Although their motivation to eat appeared to be intact, rats fasted for 72 h showed the smallest compensatory refeeding rate after fasting, possibly reflecting altered gut function. Expression of agouti-related protein and neuropeptide Y, was significantly increased in 48- and 72-h fasted animals. Thus, following fasting, a blunted acylated ghrelin secretion at dark onset (i.e. a period when animals depend on FFA as a source of energy) is associated with reduced locomotor activity and refeeding and an up-regulation of anabolic neuropeptides. Such changes could be interpreted as compensatory mechanisms for helping to conserve energy under conditions where food is not available.

the aim of the study was to determine plasma ghrelin concentrations in rabbits. the first part of the experiment focused on plasma ghrelin concentrations in does which were at different physiological stages and received diets with different fat contents. plasma ghrelin levels were determined in 3-month-old rabbits after 12-hour feed withdrawal and 60 minutes after feed intake. the second part of the experiment investigated the effect of exogenous ghrelin administered to dams on the course of the lactation and weight gains of young rabbits from birth to weaning. the results of the first experiment show that plasma ghrelin levels vary according to the physiological stage of the does. the addition of 2% rapeseed oil to the diet of the does had an inhibitory effect on ghrelin secretion by significantly decreasing its plasma levels. analysis of plasma ghrelin levels in 3-month-old rabbits subjected to feed withdrawal and following food intake revealed that ghrelin secretion increased when both oil-enriched and unsupplemented diets were fed after feed withdrawal. ghrelin levels began to decline postprandially. the second part of the experiment demonstrated that ghrelin administered intraperitoneally to the lactating does had an effect on the milk output of the does and thus on the weight gains of the young rabbits. key words: rabbit, ghrelin, feeding, lactation Ghrelin is a 28-amino acid peptide, secreted by endocrine cells of the gut and hypothalamic neurons. Ghrelin receptors are found in different brain structures, in the pancreas, kidneys, adipose tissue, ovaries, cardiac muscle and blood vessels (Rak and Gregoraszczuk, 2009; Suzuki et al., 2010). Under physiological conditions, ghrelin stimulates growth hormone (GH) release, and increases appetite and food intake by stimulating neuropeptide Y (NPY) cells and Agouti-related (AgRP) protein in the hypothalamic arcuate nucleus (Castaneda et al., 2010). About 60–70% of ghrelin in the blood is released from oxyntic cells (X/A-like cells) in the body and fundus of the stomach, which are closely associated with a network of capillaries (Kojima et al., 1999). Ghrelin is not released into the GIT lumen. The concentration of ghrelin D. Kowalska et al. 546 in the bloodstream depends on the state of nutrition. Plasma ghrelin concentration rises during fasting (with the highest concentrations observed immediately before the meal), and decreases 90 min postprandially (Cummings et al., 2001). In animals, ghrelin stimulates the release of the adrenocorticotropic hormone (ACTH), prolactin (PRL), cortisone and aldosterone, while inhibiting the secretion of the thyroidstimulating hormone (TSH) (Wolinski et al., 2006). The mode of action of ghrelin has received the most study in rats and pigs. Nakahara et al. (2003) showed the effect of exogenous ghrelin administered to lactating rats on the course of lactation and growth of the young. Ghrelin stimulated milk synthesis by increasing the mammary gland blood flow. Analogous observations were made for the effect of ghrelin on stimulating the growth of piglets born to mothers that received ghrelin in early lactation. In birds, the first ghrelin research concerned its stimulating effect on growth hormone release. The effects of ghrelin on food intake by birds are inconsistent because the results varied according to species, mode of peptide administration, and dose size (Saito et al., 2002). Oclon and Pietras (2007, 2011) showed that in 42-day-old chickens, 24-hour feed deprivation caused a considerable increase in ghrelin concentration in the pituitary, blood plasma, stomach and adrenals. These results agree with the earlier report of Kaiya et al. (2007) that fasting has a positive effect not only on ghrelin concentration but also on the GHRL gene expression in the avian stomach. The significant increase in the pituitary concentration of ghrelin was evidence that birds exposed to fasting stress mobilize ghrelin reserves in both the peripheral and the central nervous system (CNS). Similar changes in the CNS were also found in rats deprived of feed. Geelissen et al. (2006) demonstrated that peripheral injection of 1 nmol ghrelin/100 g b.w. inhibited food intake in 7-day-old chickens, but Kaiya et al. (2007) reported no statistically significant changes in the amount of feed intake by chickens injected intravenously with 500 pmol of ghrelin. Oclon and Pietras (2011) confirmed the anorexigenic nature of ghrelin in 7-day-old chickens. The administered ghrelin doses significantly decreased the amount of feed intake, which allows a conclusion that peripheral ghrelin (administered intravenously or intraperitoneally) crosses the blood-brain barrier and penetrates the solitary tract nucleus to the central nervous system, thus inhibiting feed intake. Because only a few studies in rabbits concerned ghrelin, this study was undertaken to determine plasma ghrelin concentrations in differently fed rabbits of different ages and at different physiological states. The effect of ghrelin, administered intraperitoneally to pregnant and first lactation does, on the amount of milk secreted and weight gains of young rabbits was determined. material and methods Subjects were New Zealand White (NZW) rabbits, a typical meat breed used in farming. Females of the foundation stock were caged individually on deep litter in Effect of ghrelin on milk output in rabbits 547 a confined, unheated facility, and young rabbits were kept in tiered wire-mesh cages with 4 animals of the same sex per cage. In the first part of the experiment, animals were assigned to two feeding groups. Rabbits from group I were fed complete pelleted diet consisting of dried lucerne, wheat bran, ground barley, ground maize, soybean meal, powdered milk, ground limestone, NaCl and a mineral-vitamin mixture. The diet for group II was supplemented with 2% rapeseed oil. The compound feeds were analysed for the content of dry matter, crude protein, crude fat, crude ash, crude fibre, organic matter and N-free extractives. The determinations were performed according to AOAC procedures (1990). Two experiments were performed. The first experiment was designed to examine changes in the plasma concentration of endogenous ghrelin in female rabbits which were at different physiological stages and received different diets, as well as in young rabbits after 12-hour feed withdrawal and 60 minutes after feed intake. The animals were divided into groups according to the following scheme: Ten females fed unsupplemented diet and 10 females fed oil-enriched diet (blood collection 60 minutes after feed intake): 1. intended for reproduction at 5 months of age (before mating), 2. in the first week of pregnancy, 3. in the third week of pregnancy, 4. after kindling (day 2). Young rabbits (10 animals receiving unsupplemented diet and 10 animals fed oil-enriched diet): 1. at the age of 3 months, after 12-hour feed withdrawal, 2. at the age of 3 months, 60 minutes after feed intake. The does were fed rationed amounts of feed (150 g) during the resting period and ad libitum during pregnancy and rearing of young to 35 days of age. From weaning (day 35) to 90 days of age, young rabbits were fed ad libitum. The does and the young rabbits received different diets for 3 weeks before the experimental period. Two ml of blood was drawn from the marginal vein of the ear of each animal during the periods mentioned above. The blood was centrifuged in a type 320 Microcentrifuge for 3 minutes. Blood samples were frozen at –20°C until further analysis. Plasma ghrelin levels were determined by radioimmunoassay using a commercial RIA kit (Linco Research, ST, Charles, MO; intra assay variation of 9.5%, sensitivity of 7.8–2000 pg/ml). The aim of the second experiment was to determine the effect of giving exogenous ghrelin to pregnant and lactating does on the growth rate of rabbits from birth to 35 days of age. Two groups of females (10 does per group) were established, which were mated at 5 months of age. In the first week of pregnancy (day 6) and at 10 days of lactation, each doe from the experimental group was given intraperitoneal injections of endogenous ghrelin (3 mcg/kg b.w.) dissolved in physiological solution to 1 ml volume (CALBIOCHEM, Ghrelin, Rat, Mouse, Synthetic). On the same days, the control does were injected intraperitoneally with a placebo (1 ml of physiological solution). Litters of the does were standardized to 6 animals to exclude the effect of litter size on daily gains of the young. Young rabbits were weighed every day at the D. Kowalska et al. 548 same time (8:00 am) from birth to 35 days of age to determine daily gains, on the basis of which the does’ milk output was determined. The results were analysed statistically with analysis of variance and Duncan’s D-test, using Statistica 7 software.

Although it is known that urocortin 1 (UCN) acts on both corticotropin-releasing factor receptors (CRF1 and CRF2), the mechanisms underlying UCN-induced anorexia remain unclear. In contrast, ghrelin, the endogenous ligand for the growth hormone secretagogue receptor, stimulates food intake. In the present study, we examined the effects of CRF1 and CRF2 receptor antagonists (CRF1a and CRF2a) on ghrelin secretion and synthesis, c-fos mRNA expression in the caudal brain stem, and food intake following intracerebroventricular administration of UCN. Eight-week-old, male Sprague-Dawley rats were used after 24-h food deprivation. Acylated and des-acylated ghrelin levels were measured by enzyme-linked immunosorbent assay. The mRNA expressions of preproghrelin and c-fos were measured by real-time RT-PCR. The present study provided the following important insights into the mechanisms underlying the anorectic effects of UCN: 1) UCN increased acylated and des-acylated ghrelin levels in the gastric body and decreased their levels in the plasma; 2) UCN decreased preproghrelin mRNA levels in the gastric body; 3) UCN-induced reduction of plasma ghrelin and food intake were restored by CRF2a but not CRF1a; 4) UCN-induced increase of c-fos mRNA levels in the caudal brain stem containing the nucleus of the solitary tract (NTS) was inhibited by CRF2a; and 5) UCN-induced reduction of food intake was restored by exogenous ghrelin and rikkunshito, an endogenous ghrelin secretion regulator. Thus, UCN increases neuronal activation in the caudal brain stem containing NTS via CRF2 receptors, which may be related to UCN-induced inhibition of both ghrelin secretion and food intake.

Summary Two groups of 3-day-old Saanen goat kids (MILK and WMIX) were studied in order to investigate the effect of weaning on plasma ghrelin and insulin and on pancreatic activity. MILK kids received goat milk to age 50 days; WMIX kids were initially fed milk but started weaning at 30 days and were completely weaned by 48 days. Dry matter intake and body weights were recorded, and plasma samples were analysed for metabolites, ghrelin, insulin, leptin and α-amylase. At 50 days, all the animals were slaughtered, pancreas samples were analysed for α-amylase, zymogen, DNA and ribosomal capacity (RNA/zymogen). Seven days after the beginning of the weaning program, dry matter intake in the WMIX group began to decrease in relation to the MILK group. Nonetheless, body weight did not differ throughout the study period. Weaning significantly decreased plasma levels of glucose, amino acids, urea and insulin, but increased creatinine and ghrelin. In weaning kids ghrelin secretion may help minimize the negative consequences of the new diet on dry matter intake. Pancreatic zymogen and ribosomal capacity did not differ between the groups, whereas pancreatic amylase activity was over three times higher in MILK than WMIX kids even though the former had no dietary starch. This finding could be a consequence of lower pancreatic secretion of amylase in the MILK group due to the lack of dietary starch, resulting in pancreatic accumulation, but could also be due to higher plasma insulin in the MILK group, suggesting a role for insulin in the functional development of the pancreas in weaning goats.

Background: Ghrelin is a gastric secreted hormone deeply implicated in meal initiation and body weight regulation. This peptide is a peripheral orexigenic hormone with a nutritional status-dependent regulation showing a pre-pandrial rise and post-prandial fall pattern. A wide variety of studies have tested the effect of meal different nutrient composition over stomach mucosa ghrelin content and plasmatic ghrelin levels; nevertheless, few and non-conclusive data exist about the direct action of macronutrients on the stomach in order to regulate ghrelin secretion. The recent identification of taste receptors or chemoreceptors in the stomach mucosa would reinforce this paradigm. Aims: To investigate the individual effect of different macronutrients (l-glutamine, lipids, and glucose) over gastric ghrelin secretion by using an in vitro gastric explants model. Results: L-glutamine and intralipid emulsion act locally in the stomach decreasing ghrelin secretion, while no effect was found after glucose exposure. Conclusions: These results show for the first time that macronutrients, and specially amino acids and lipids, act directly in the stomach in order to regulate gastric ghrelin release. Consequently, the chemosensory capacity of the stomach, until now restricted to the oral cavity or intestine, is demonstrated.

Ghrelin, produced mainly in abomasum of ruminants, is a peptide with roles in the regulation of feeding. The present study assessed the alterations of plasma ghrelin in sheep fed with all forage or high-grain rations and the probable effects of altered ghrelin secretion on feed intake in animals with acidic rumen. Eight Karakul male lambs were divided into the control (n = 4) and experiment groups (n = 4) and fed individually for 20 days. The control group was fed an all forage ration for the whole study period. For the experiment group, 40% of the ration was substituted with ground barley for 10 days. For the rest of the study, 62.5% of the ration was substituted with ground barley. Signs of negative alteration of digestive functions (e.g., reduced feed intake, loose manure with reduced dry matter) were observed in the experiment group after day 10 of the experiment when ground barley was increased to 62.5% of the ration. On days 8 and 10 of each step, blood samples were collected for measuring plasma ghrelin level from jugular vein 1 hour before, and 1 and 3 hours after feeding. In the control group, plasma ghrelin increased 1 hour post-feeding (p

The roles of pancreatic polypeptide (PP) have not been determined in ruminant animals. The aim of the present study was to examine the role of PP in the regulation of ghrelin secretion in sheep. Two experiments were conducted using four 2-yr-old Suffolk wethers fed a maintenance diet of alfalfa hay cubes. In Exp. 1, the effects of feeding on blood ghrelin and PP concentrations were examined in scheduled-fed sheep. Blood samples were collected every 10 min from 30 min before to 360 min after feeding. Plasma PP concentrations were transiently increased from the preprandial average value to the values from 30 to 60 min after feeding and gradually decreased (P < 0.05) to stable values from 150 to 180 min. The values from 30 to 60 min were greater (P < 0.05) than those from 150 to 360 min. In contrast, plasma ghrelin concentrations were gradually decreased (P < 0.01) by feeding. The values from 60 to 360 min were less (P < 0.01) than the preprandial average value. In Exp. 2, the effects of continuous PP infusion on ghrelin secretion were examined in feed-deprived sheep. The animals were deprived of feed for 48 h before PP infusion. The PP-treated group intravenously received synthetic bovine PP at a rate of 10 pmol.kg(-1 )of BW.min(-1) for 180 min. Blood samples were collected every 10 min from 30 min before to 180 min after the commencement of PP infusion. Plasma PP concentrations reached a plateau within 30 min after the commencement of PP infusion. Plasma ghrelin concentrations were decreased (P = 0.002, 0.016, 0.007) by PP infusion at 160, 170, and 180 min, respectively. In conclusion, plasma ghrelin and PP concentrations were decreased and increased, respectively, in response to feeding in ruminant animals. Furthermore, PP could depress ghrelin secretion.

To establish a tool to study ghrelin production and secretion in vitro, we developed a novel ghrelin-producing cell line, MGN3–1 (mouse ghrelinoma 3-1) cells from a gastric ghrelin-producing cell tumor derived from ghrelin-promoter Simian virus 40-T-antigen transgenic mice. MGN3-1 cells preserve three essential characteristics required for the in vitro tool for ghrelin research. First, MGN3-1 cells produce a substantial amount of ghrelin at levels approximately 5000 times higher than that observed in TT cells. Second, MGN3-1 cell expressed two key enzymes for acyl modification and maturation of ghrelin, namely ghrelin O-acyltransferase for acylation and prohormone convertase 1/3 for maturation and the physiological acyl modification and maturation of ghrelin were confirmed. Third, MGN3-1 cells retain physiological regulation of ghrelin secretion, at least in regard to the suppression by somatostatin and insulin, which is well established in in vivo studies. Thus, MGN3-1 cells are the first cell line derived from a gastric ghrelin-producing cell preserving secretion of substantial amounts of ghrelin under physiological regulation. This cell line will be a useful tool for both studying the production and secretion of ghrelin and screening of ghrelin-modulating drugs.

The orexigenic hormone ghrelin is secreted from the stomach and has been implicated in the regulation of energy and glucose homeostasis. We hypothesized that ghrelin, like other gastrointestinal (GI) hormones, is present in intestinal lymph, and sampling this compartment would provide advantages for studying ghrelin secretion in rodents. Blood and lymph were sampled from catheters in the jugular vein and mesenteric lymph duct before and after intraduodenal (ID) administration of isocaloric Ensure, dextrin, or Liposyn meals or an equal volume of saline in conscious Sprague-Dawley rats. Total ghrelin levels were measured using an established radioimmunoassay. Acyl and des-acyl ghrelin were measured using two-site ELISA. Fasting ghrelin levels in lymph were significantly higher than in plasma (means ± SE: 3,307.9 ± 272.9 vs. 2,127.1 ± 115.0 pg/ml, P = 0.004). Postingestive acyl and des-acyl ghrelin levels were also significantly higher, whereas the ratio of acyl:des-acyl ghrelin was similar in lymph and plasma (0.91 ± 0.28 vs. 1.20 ± 0.36, P = 0.76). The principle enzymes responsible for deacylation of ghrelin were lower in lymph than in plasma. Following ID Ensure, maximum ghrelin suppression occurred at 2 h in lymph compared with at 1 h in plasma. The return of suppressed ghrelin levels to baseline was also delayed in lymph. Similarly, dextrin also induced significant suppression of ghrelin (two-way ANOVA: P = 0.02), whereas Liposyn did not ( P = 0.32). On the basis of these findings, it appears that intestinal lymph, which includes drainage from the interstitium of the GI mucosa, is enriched in ghrelin. Despite reduced deacylating activity in lymph, there is not a disproportionate amount of acyl ghrelin in this pool. The postprandial dynamics of ghrelin are slower in lymph than plasma, but the magnitude of change is greater. Assessing ghrelin levels in the lymph may be advantageous for studying its secretion and concentrations in the gastric mucosa.

The propensity of diets of different composition to promote obesity is a current topic in feline medicine. The effects of three meals with different protein:fat ratios on hormones (insulin, acylated ghrelin and amylin) involved in the control of food intake and glucose metabolism were compared. Five lean (two females and three males, 28·6 (sd 3·4) % body fat mass (BFM), mean body weight (BW) 4590 g) and five obese (two females and three males, 37·1 (sd 4·1) % BFM, mean BW 4670 g) adult cats were studied. Only BFM differed significantly between obese and lean cats. The cats were fed a high-protein (HP), a high-fat and a high-carbohydrate diet in a randomised cross-over design. Food intake did not differ between cats fed on the different diets, but obese cats consumed significantly more energy, expressed as per kg fat-free mass, than lean cats. After a 6-week adaptation period, a test meal was given and blood samples were collected before and 0, 30, 60 and 100 min after the meal. Baseline concentrations of glucose, amylin and acylated ghrelin were higher in obese cats than in lean cats, and obese cats showed the highest postprandial responses of glucose and amylin. The HP diet led to higher postprandial amylin concentrations than the other diets, indicating a possible effect of amino acids on β-cell secretion. Postprandial ghrelin concentrations were unaffected by diet composition. The relationship between insulin, amylin and ghrelin secretion and their relevant roles in food intake and glucose metabolism in cats require further study.

Ghrelin, a peptide predominantly produced by the stomach, was discovered as natural ligand of the Growth Hormone Secretagogue receptor type 1a (GHS-R1a) and was anticipated to play major role in the control of somatotroph function. Ghrelin progressively turned out to exert pleiotropic actions on several endocrine and non endocrine target tissues. Particular attention has focused on its central orexigenic effect and weight control, and more recently on its peripheral metabolic actions on insulin secretion and insulin sensitivity, glucose and lipid metabolism. Ghrelin circulates in two forms, acylated (AG) and unacylated (UAG). Interestingly, some metabolic actions of ghrelin are independent of its acylation, which is necessary for it to bind and activate the GHS-R1a, supporting the hypothesis of the existence of several ghrelin receptor subtypes involved in the control of metabolic functions and pancreatic cell survival. Recent data have introduced the hypothesis that the ghrelin system plays a role in polygenic obesity, type 2 diabetes, metabolic syndrome, atherogenesis, and β-cell survival in type 1 diabetes. Many experimental studies have recently tried to inhibit or amplify ghrelin secretion for the treatment of obesity and wasting syndromes, respectively. This review recapitulates what is known about ghrelin chemical structure, GHS-R1a and the putative unknown receptor subtypes, AG and UAG involvement in the control of feeding, weight, glucose and lipid metabolism, and the recently patented molecules that modulate the pleiotropic actions of the ghrelin system.

Context: Sex-steroid hormones amplify pulsatile GH secretion by unknown mechanisms. Ghrelin is the most potent natural GH secretagogue discovered to date. A plausible unifying postulate is that estradiol (E2) enhances hypothalamo-pituitary sensitivity to ghrelin (a physiological effect). The hypothesis is relevant to understanding the basis of hyposomatotropism in aging and other relatively hypogonadal states. Objective: Our objective was to test the hypothesis that E2 supplementation potentiates ghrelin’s stimulation of pulsatile GH secretion. Setting: The study was conducted at an academic medical center. Subjects: Healthy postmenopausal women (n = 20) were included in the study. Interventions: Separate-day iv infusions of saline vs. five graded doses of ghrelin were performed in volunteers prospectively randomly assigned to receive (n = 8) or not receive (n = 12) transdermal E2 for 21 d were performed. Measures: GH secretion was estimated by deconvolution analysis and abdominal visceral fat mass determined by computerized axial tomography were calculated. Results: E2 supplementation augmented ghrelin’s stimulation of basal (nonpulsatile) GH secretion by 3.6-fold (P = 0.022), increased GH responses to low-dose ghrelin by 2.9-fold (P = 0.035), did not alter ghrelin efficacy, and elicited more regular patterns of acylated ghrelin concentrations during saline infusion (P = 0.033). Abdominal visceral fat negatively determined responses to ghrelin (R = −0.346; P < 0.005). Conclusions: Transdermal E2 supplementation potentiates GH secretion stimulated by physiological but not pharmacological concentrations of acylated ghrelin, and concomitantly regularizes patterns of bioactive ghrelin secretion in postmenopausal women. Accordingly, the estrogen milieu appears to control sensitivity of the hypothalamopituitary unit to acylated ghrelin.

Ghrelin is a stomach hormone that stimulates growth hormone (GH) secretion, adiposity, and food intake. Gastric ghrelin production and secretion are regulated by caloric intake; ghrelin secretion increases during fasting, decreases with refeeding, and is reduced by diet-induced obesity. The aim of the present study was to test the hypotheses that 1) an increase in body adiposity will play an inhibitory role in the reduction of gastric ghrelin synthesis and secretion during chronic ingestion of a high-fat (HF) diet and 2) chronic ingestion of an HF diet will suppress the rise in circulating ghrelin levels in response to acute fasting. Adult male Sprague-Dawley rats were fed a standard AIN-76A (approximately 5-12% of calories from fat) or an HF (approximately 45% of calories from fat) diet. The effect of increased adiposity on gastric ghrelin homeostasis was assessed by comparison of stomach ghrelin production and plasma ghrelin levels in obese and nonobese rats fed the HF diet. HF diet-fed, nonobese rats were generated by administration of triiodothyronine to lower body fat accumulation. Our findings indicate that an increased fat mass per se does not exert an inhibitory effect on ghrelin homeostasis during ingestion of the HF diet. Additionally, the magnitude of change in plasma ghrelin in response to fasting was not blunted, indicating that a presumed, endogenous signal for activation of ingestive behavior remains intact, despite excess stored calories in HF-fed rats.

It has been reported that cannabinoids may cause overeating in humans and in laboratory animals. Although, endogenous cannabinoids and their receptors (CB1) have been found in the hypothalamus, and recently also in gastrointestinal tract, the precise mechanism of appetite control by cannabinoids remains unknown. Recently, ghrelin--a hormone secreted mainly from the stomach X/A-like cells was proposed to be an appetite stimulating agent. The aim of this study was the evaluation of the influence of a single ip injection of a stable analogue of endogenous cannabinoid--anandamide, R-(+)-methanandamide (2.5 mg/kg) and CP 55,940 (0.25 mg/kg), an exogenous agonist of CB1 receptors, on ghrelin plasma concentration and on ghrelin immunoreactivity in the gastric mucosa of male Wistar rats. Four hours after a single injection of both cannabinoids or vehicle, the animals were anaesthetized and blood was taken from the abdominal aorta to determinate plasma ghrelin concentration by RIA. Subsequently, the animals underwent resection of distal part of stomach. Immunohistochemical study of gastric mucosa, using the EnVision method and specific monoclonal antibodies against ghrelin was performed. The intensity of ghrelin immunoreactivity in X/A-like cells was analyzed using Olympus Cell D image analysis system. The attenuation of ghrelin-immunoreactivity of gastric mucosa, after a single injection of R-(+)-methanandamide and CP 55,940 was accompanied by a significant increase of ghrelin plasma concentration. These results indicate that stimulation of appetite exerted by cannabinoids may be connected with an increase of ghrelin secretion from gastric X/A-like cells.

SummaryGhrelin is a 28 amino acid, appetite-stimulating peptide hormone secreted by the food-deprived stomach. Serine-3 of ghrelin is acylated with an eight-carbon fatty acid, octanoate, which is required for its endocrine actions. Here, we identify GOAT (Ghrelin O-Acyltransferase), a polytopic membrane-bound enzyme that attaches octanoate to serine-3 of ghrelin. Analysis of the mouse genome revealed that GOAT belongs to a family of 16 hydrophobic membrane-bound acyltransferases that includes Porcupine, which attaches long-chain fatty acids to Wnt proteins. GOAT is the only member of this family that octanoylates ghrelin when coexpressed in cultured endocrine cell lines with prepro-ghrelin. GOAT activity requires catalytic asparagine and histidine residues that are conserved in this family. Consistent with its function, GOAT mRNA is largely restricted to stomach and intestine, the major ghrelin-secreting tissues. Identification of GOAT will facilitate the search for inhibitors that reduce appetite and diminish obesity in humans.