Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor (GHSR; OMIM 601898) and is involved in regulating GH release.
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.
NCBI Summary:
This gene encodes the ghrelin-obestatin preproprotein that is cleaved to yield two peptides, ghrelin and obestatin. Ghrelin is a powerful appetite stimulant and plays an important role in energy homeostasis. Its secretion is initiated when the stomach is empty, whereupon it binds to the growth hormone secretagogue receptor in the hypothalamus which results in the secretion of growth hormone (somatotropin). Ghrelin is thought to regulate multiple activities, including hunger, reward perception via the mesolimbic pathway, gastric acid secretion, gastrointestinal motility, and pancreatic glucose-stimulated insulin secretion. It was initially proposed that obestatin plays an opposing role to ghrelin by promoting satiety and thus decreasing food intake, but this action is still debated. Recent reports suggest multiple metabolic roles for obestatin, including regulating adipocyte function and glucose metabolism. Alternative splicing results in multiple transcript variants. In addition, antisense transcripts for this gene have been identified and may potentially regulate ghrelin-obestatin preproprotein expression. [provided by RefSeq, Nov 2014]
General function
Ligand, Hormone
Comment
Circulating levels of obestatin and copeptin in obese and nonobese women with polycystic ovary syndrome. Taskin MI et al. (2015) Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies, affecting 5-8% of reproductive-age women. It is associated with insulin resistance, central obesity, type 2 diabetes mellitus, dyslipidemia, and cardiovascular diseases. The current study was undertaken to evaluate serum copeptin and obestatin levels, carotid artery intima-media thickness, and brachial artery flow mediated dilatation in obese and nonobese women with PCOS and age-matched healthy controls and to investigate their relationship with each other and with clinical, metabolic, and hormonal parameters and cardiovascular risk factors. In the study population, we analyzed 60 patients with PCOS and 30 age-matched healthy women as controls. The patients with PCOS were divided into two groups based on body mass index (BMI): obese group (BMI>30kg/m(2), n=30) or nonobese group (BMI<30kg/m(2), n=30). History was obtained and a physical examination, peripheral venous blood sampling, and carotid and brachial artery ultrasonography were performed. Serum copeptin and obestatin levels, total testosterone, C-reactive protein (CRP), glucose, total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, homeostasis model assessment for insulin resistance (HOMA-IR), carotid artery intima-media thickness (CIMT), and brachial artery flow-mediated vasodilation (FMD) were determined and compared among the groups. Women with PCOS, especially obese ones, had higher triglycerides, HOMA-IR, total testosterone, CRP, systolic and diastolic blood pressure, and waist-to-hip ratio (WHR), and lower HDL. Serum obestatin levels were significantly lower in the obese PCOS group than they were in the nonobese and control groups (p<0.001). Serum copeptin levels were significantly higher in the obese PCOS group than they were in the nonobese PCOS and control groups (p<0.001). CIMT values were similar among the groups (p>0.05). Brachial artery FMD was lower in the PCOS groups than it was in the control group (p<0.001). Obestatin and FMD values were negatively correlated with cardiovascular risk factors, whereas copeptin was positively correlated. A significant positive correlation was found between copeptin, BMI, WHR, hirsutism score, total testosterone, and HOMA-IR. There was no correlation between CIMT, copeptin, obestatin, and FMD. A positive correlation was seen between CIMT, BMI, triglycerides, and HOMA-IR. Copeptin and obestatin may provide useful information regarding future cardiovascular risk in PCOS patients as copeptin was positively correlated and obestatin was negatively correlated with cardiovascular risk factors.//////////////////
Cellular localization
Secreted
Comment
candidate123
Ovarian function
Steroid metabolism, Luteinization, Oocyte maturation, Early embryo development
Comment
N-octanoylated ghrelin peptide inhibits bovine oocyte meiotic resumption. Xu XL et al. (2018) Studies have shown that ghrelin plays an important role in the mammalian reproductive system, including the central, gonadal levels, and also during in vitro maturation of oocytes; however, the functions of ghrelin in bovine oocyte meiosis require further investigation. We aimed to evaluate the effects of an n-octanoylated ghrelin peptide on oocyte meiotic resumption and the developmental competence of mature oocytes in vitro. design: The expression of GHRL (encoding ghrelin) mRNA and its receptor (the growth hormone secretagogue receptor, GHSR) in the cumulus-oocyte complex (COCs), denuded oocytes (DOs), and cumulus cells (CCs) was assessed using quantitative real-time reverse transcription PCR (qRT-PCR), and the effects of the n-octanoylated ghrelin peptide on meiotic resumption were studied at four different doses (0, 10, 50, and 100 ng/mL) in a 6 h culture system. qRT-PCR analysis showed that GHRL and GHSR mRNAs were expressed in all tested samples; however, GHRL was predominantly expressed in DOs, and GHSR was predominantly expressed in CCs. Germinal vesicle breakdown was inhibited significantly by 50 ng/mL ghrelin compared with that in the negative control (P < 0.05). Further studies showed that n-octanoylated ghrelin increased the levels of cAMP and cGMP in the CCs and DOs, which inhibited the meiotic resumption of bovine oocytes. And the inhibitory role in the developmental competence of mature oocytes were also included, ghrelin could significantly improve the cleavage rate (P < 0.05) and blastocyst rate (P < 0.05). N-octanoylated ghrelin maintained bovine oocytes meiotic arrest and further improved their developmental competence; therefore, n-octanoylated ghrelin could be considered as a potential pharmaceutical inhibitor of meiosis for the in vitro maturation of bovine oocytes.//////////////////
Alteration of ghrelin/obestatin ratio in adolescence with polycystic ovarian syndrome. Wu W et al. (2017) Ghrelin, an endoggenous for the growth hormone secretagogue receptor, has been shown to participate in the regulation of energy homeostasis and pituitary hormone secretion. Obestatin, encoded by the same gene as ghrelin, is described as a physiological opponent of ghrelin. Ghrelin and obestatin are altered in polycystic ovary syndrome (PCOS), which is characterized by insulin resistance and pituitary hormone secretion disorder. The aim of this study was to evaluate ghrelin/obestatin imbalance in relation to insulin resistance and pituitary hormone in adolescence with PCOS. This restrospective case-control study included 33 adolescence with PCOS and 38 control adolescence. Ghrelin and obestatin concentrations in serum were determined by RIA, and the serum fasting glucose and Insulin were determined by the glucose oxidase color method and INS-EASIA. The serum LH and FSH were measured by highly specific hemiluminescence immunoassays. We found that the serum ghrelin levels and ghrelin/obestatin ratio were significant lower in PCOS group than in control group, and the serum obestatin levels were significant higher in PCOS group than in control group. The ghrelin/obestatin ratios were negatively correlation with LH/FSH ratio and insulin resistant index in PCOS group. The findings of this study suggest that ghrelin/obestatin imbalance may play a role in pathogenesis of adolescent PCOS.//////////////////
Obestatin directly controls chicken ovarian cell functions. Sirotkin AV et al. (2016) The aim of the present in-vitro study was to examine the role of obestatin in the direct control of basic avian ovarian granulosa cell functions proliferation, apoptosis and secretory activity. In addition, the effects of obestatin on hormone release by cultured ovarian granulosa cells and follicular fragments (containing both granulosa and theca cells) were examined. We identified the effect of obestatin addition (0.1, 10 or 100 ng/ml medium) on the accumulation of markers of proliferation (PCNA, cyclin B1, MAPK/ERK1,2) and nuclear (TdT) and cytoplasmic (bax, caspase 3) apoptosis, as well as the release of progesterone (P), testosterone (T) and estradiol (E) by cultured chicken granulosa cells. Furthermore, the action of obestatin addition (0.1, 10 or 100 ng/ml medium) on the release of P, T, E and argininevasotocin (AVT) by cultured fragments of chicken ovarian follicles was examined. The accumulation of proliferation and apoptosis markers was assessed by immunocytochemistry and SDS PAGE-Western immunoblotting. The release of hormones was determined by an EIA. It was observed that obestatin addition could inhibit the accumulation of proliferation markers (PCNA and cyclin B1, but not of MAPK/ERK1,2), promote the expression of nuclear (TdT) and cytoplasmic (bax, caspase 3) apoptosis markers and suppress P, T, and E release by cultured granulosa cells. In cultured ovarian follicular fragments, obestatin promoted P, T, and E, but not AVT, release. These observations represent the first demonstration that (i) obestatin can directly control avian ovarian cell proliferation, apoptosis and hormone release and (ii) the interrelationship between theca and granulosa cells can determine the characteristics of obestatin action on ovarian secretory activity.//////////////////
Expression and localization of ghrelin and its receptor in ovarian follicles during different stages of development and the modulatory effect of ghrelin on granulosa cells function in buffalo. Gupta M et al. (2014) Ghrelin, a hormone predominantly found in the stomach, was recently described as a factor that controls female reproductive function. The aim of our study was to investigate the expression and localization of ghrelin and its active receptor, growth hormone secretagogue receptor type 1a (GHS-R1a) in buffalo ovarian follicles of different follicular size and to investigate role of ghrelin on estradiol (E2) secretion, aromatase (CYP19A1), proliferating cell nuclear antigen (PCNA) and apoptosis regulator Bax gene expression on granulosa cell culture. Using real time PCR and western blot, we measured gene and protein expression of examined factors. Localization was done with immunofluorescence method. Expression of ghrelin increased with follicle size with significantly highest in dominant or pre-ovulatory follicle (P<0.05). Expression of GHS-R1a was comparable in medium and large follicle but was higher than small follicles (P<0.05). Both the factors were localized in granulosa and theca cells. Pattern of intensity of immunofluorescence was similar with mRNA and protein expression. In the in vitro study granulosa cells (GCs) were cultured and treated with ghrelin each at 1, 10 and 100ng/ml concentrations for two days after obtaining 75-80 per cent confluence. Ghrelin treatment significantly (P<0.05) inhibited E2 secretion, CYP19A1 expression, apoptosis and promoted cell proliferation. In conclusion, this study provides novel evidence for the presence of ghrelin and receptor GHS-R1a in ovarian follilcles and modulatory role of ghrelin on granulosa cell function in buffalo.//////////////////
Ghrelin Accelerates In Vitro Maturation of Bovine Oocytes. Dovolou E 2014 et al.
Ghrelin, apart from its metabolic role, is nowadays considered as a basic regulator of reproductive functions of mammals, acting at central and gonadal levels. Here, we investigated for possible direct actions of ghrelin on in vitro maturation of bovine oocytes and for its effects on blastocyst yield and quality. In experiment 1, cumulus oocyte complexes (COCs) were matured in the presence of four different concentrations of ghrelin (0, 200, 800 and 2000pg/ml). In vitro fertilization and embryo culture were carried out in the absence of ghrelin, and blastocyst formation rates were examined on days 7, 8 and 9. In experiment 2, only the 800pg/ml dose of ghrelin was used. Four groups of COCs were matured for 18 or 24h (C18, Ghr18, C24 and Ghr24), and subsequently, they were examined for oocyte nuclear maturation and cumulus layer expansion; blastocysts were produced as in experiment 1. The relative mRNA abundance of various genes related to metabolism, oxidation, developmental competence and apoptosis was examined in snap-frozen cumulus cells, oocytes and day-7 blastocysts. In experiment 1, ghrelin significantly suppressed blastocyst formation rates. In experiment 2, more ghrelin-treated oocytes matured for 18h reached MII compared with controls, while no difference was observed when maturation lasted for 24h. At 18 and 24h, the cumulus layer was more expanded in ghrelin-treated COCs than in the controls. The blastocyst formation rate was higher in Ghr18 (27.72.4%) compared with Ghr24 (17.52.4%). Differences were detected in various genes' expression, indicating that in the presence of ghrelin, incubation of COCs for 24h caused over-maturation (induced ageing) of oocytes, but formed blastocysts had a higher hatching rate compared with the controls. We infer that ghrelin exerts a specific and direct role on the oocyte, accelerating its maturational process.
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Expression of ghrelin and the ghrelin receptor in different stages of porcine corpus luteum development and the inhibitory effects of ghrelin on progesterone secretion, 3?hydroxysteroid dehydrogenase (3?honestly significant difference (HSD)) activity and protein expression. Rak-Mardyla A et al. Recent studies have suggested that ghrelin plays a direct role in controlling female reproduction. The aim of the present study was to investigate the mRNA and protein expression of ghrelin and its receptor (via real time PCR, Western blot and immunohistochemistry analysis, respectively) in porcine corpora lutea (CL) collected during early (CL1: 1-2 days after ovulation), middle (CL2: 7-10 after ovulation), and late luteal phase (CL3: 13-15 after ovulation). Ghrelin expression and concentration of both acylated and unacylated forms of ghrelin significantly increased during CL development. Immunohistochemistry analysis shown localization of ghrelin protein in the cytoplasm of large luteal cells. No changes in the expression of the ghrelin receptor were observed. Direct in vitro effects of ghrelin on progesterone (P4) secretion and 3-beta-hydroxysteroid dehydrogenase (3?honestly significant difference (HSD)) activity, which were measured by the conversion of pregnenolone (P5) to P4, and 3?HSD protein expression were then analyzed. To assess 3?HSD activities, mature luteal cells were first cultured for 24 h with ghrelin at 100, 250, 500 and 1000 pg/mL with P5, or with aminoglutethimide (AMG). AMG is an inhibitor of CYP11A1-mediated hydroxylation; an addition of AMG and P5 enabled P4 production to serve as an index of 3?HSD activity. Inhibitory effects of ghrelin on P4 secretion, 3?HSD activity and protein expression were observed. In conclusion, the presence of ghrelin and its receptor in porcine corpora lutea and the direct inhibitory effects of ghrelin on luteal P4 secretion and 3?HSD suggest potential auto/paracrine regulation by ghrelin in the luteal phase of ovary function.
Ghrelin promotes antioxidant enzyme activity and reduces lipid peroxidation in the rat ovary. Kheradmand A et al. Antioxidant properties of ghrelin have been recently reported on various oxidative stresses in limited tissues. This study was set to examine the possible antioxidative effects of ghrelin in rat ovarian tissue. Twenty eight female adult Wistar rats were randomly allocated into control and treatment groups. Treatment group (n=14) received 2nmol of ghrelin as subcutaneous injection for 14 consecutive days or vehicle (physiological saline) to the control rats. The animals from both groups were equally killed on days 9 and 14 after beginning of ghrelin injection (n=7 from each group on each day) and their ovaries were taken for later antioxidant enzyme activity assays as well as measurement of glutathione content and thiobarbituric acid reactive substances (TBARS) level. Superoxide dismutase activity was significantly higher on days 9 (P<0.05) and 14 (P<0.01) in the treated group compared to the control rats. By contrast, lipid peroxidation, as TBARS value, reduced significantly on both experimental days in the ghrelin-exposed animals (P<0.05). Although, the mean activity of catalase and glutathione content was greater in the treated rats, however, the differences were not statistically significant. Slight changes were occurred in glutathione peroxidase activity during the experimental period and there were any differences neither on day 9 nor on day 14 between groups. In conclusion, the results of the present investigation indicate for the first time the novel evidences of antioxidant properties of ghrelin in the rat ovary.
Transcription factor p53 can regulate proliferation, apoptosis and secretory activity of luteinizing porcine ovarian granulosa cell cultured with and without ghrelin and FSH. Sirotkin A et al. The aim of our in vitro experiments was to examine the role of transcription factor p53 in controlling the basic functions of ovarian cells and their response to hormonal treatments. Transfection with the p53 gene construct promoted accumulation of this transcription factor within cells. It also stimulated the expression of marker of apoptosis (ASK-1). Over-expression of p53 resulted in reduced accumulation of marker of proliferation (cyclin B1), P4 and PGF secretion and increased OT and PGE secretion. Ghrelin, when added alone, did not affect p53 or P4, but reduced ASK-1 and increased PGF and PGE secretion. Over-expression of p53 reversed the effect ghrelin on OT, caused it to be inhibitory to P4 secretion, but did not modify its action on ASK-1, PGF or PGE. FSH promoted the accumulation of p53, ASK-1 and cyclin B1; these effects were unaffected by p53 transfection. These multiple effects of the p53 gene construct on luteinizing granulosa cells, cultured with and without hormones (1) demonstrate the effects of ghrelin and FSH on porcine ovarian cell apoptosis and secretory activity, (2) confirm the involvement of p53 in promoting apoptosis and inhibiting P4 secretion in these cells, (3) provide the first evidence, that p53 suppress proliferation of ovarian cells, (4) provide the first evidence that p53 is involved in the control of ovarian peptide hormone (OT) and prostaglandin (PGF and PGE) secretion, and (5) suggest that p53 can modulate, but probably not mediate the effects of ghrelin and FSH on the ovary.
Gherlin expression in women with polycystic ovary syndrome--a preliminary study Skommer J, et al .
The etiology and pathogenesis of polycystic ovary syndrome (PCOS) is still unknown. Using real-time PCR, we detected that polycystic ovaries showed almost ten times lower expression of ghrelin mRNA than normal ovaries, whereas the mRNA levels in blood cells were similar in both study groups. This suggests that the presence of ghrelin in PCOS and normal ovaries may have an autocrine/paracrine modulatory effect on ovary functions and local significance in the etiology of PCOS.
Effects of ghrelin and its analogues on chicken ovarian granulosa cells. Sirotkin AV et al. The aim of these in vitro experiments was (1) to examine the effects of ghrelin on the basic functions of ovarian cells (proliferation, apoptosis, secretory activity); (2) to determine the possible involvement of the GHS-R1a receptor and PKA- and MAPK-dependent post-receptor intracellular signalling cascades; (3) to identify the active part of the 28-amino acid molecule responsible for the effects of ghrelin on ovarian cells. We compared the effect of full-length ghrelin 1-28, a synthetic activator of GHS-R1a, GHRP6, and ghrelin molecular fragments 1-18 and 1-5 on cultured chicken ovarian cells. Indices of cell apoptosis (expression of the apoptotic peptide bax and the anti-apoptotic peptide bcl-2), proliferation (expression of proliferation-associated peptide PCNA), and expression of protein kinases (PKA and MAPK) within ovarian granulosa cells were analysed by immunocytochemistry. The secretion of progesterone (P(4)), testosterone (T), estradiol (E(2)) and arginine-vasotocin (AVT) by isolated ovarian follicular fragments was evaluated by RIA/EIA. It was observed that accumulation of bax was increased by ghrelin 1-28, GHRP6 and ghrelin 1-18, but not by ghrelin 1-5. Expression of bcl-2 was suppressed by addition of ghrelin 1-28, GHRP6 and ghrelin 1-5, but promoted by ghrelin 1-18. The occurrence of PCNA was reduced by ghrelin 1-28, GHRP6, ghrelin 1-18 and ghrelin 1-5. An increase in the expression of MAPK/ERK1, 2 was observed after addition of ghrelin 1-28, GHRP6 and ghrelin 1-18, but not ghrelin 1-5. The accumulation of PKA decreased after treatment with ghrelin 1-28 and increased after treatment with GHRP6 and ghrelin 1-18 but not ghrelin 1-5. Secretion of P(4) by ovarian follicular fragments was decreased after addition of ghrelin 1-28 or ghrelin 1-5 but stimulated by GHRP6 and ghrelin 1-18. Testosterone secretion was inhibited by ghrelins 1-28 and 1-18, but not by GHRP6 or ghrelin 1-5. Estradiol secretion was reduced after treatment with ghrelin 1-28 but stimulated by ghrelins 1-18 and 1-5; GHRP6 had no effect. AVT secretion was stimulated by ghrelin 1-28, GHRP6 and ghrelin 1-18, but inhibited by ghrelin 1-5. The comparison of the effects of the four ghrelin analogues on nine parameters of ovarian cells suggest (1) a direct effect of ghrelin on basic ovarian functions-apoptosis, proliferation, steroid and peptide hormone secretion; (2) that the majority of these effects can be mediated through GHS-R1a receptors; (3) an effect of ghrelin on MAPK- and PKA-dependent intracellular mechanisms, which can potentially mediate the action of ghrelin at the post-receptor level; (4) that ghrelin residues 5-18 may be responsible for the major effects of ghrelin on the avian ovary.
Ghrelin affects the release of luteolytic and luteotropic factors in human luteal cells. Tropea A et al. Context: Ghrelin, well-known modulator of food intake and energy balance, is a rather ubiquitous peptide involved in several endocrine and non-endocrine actions. A possible as-yet-unknown role for ghrelin in modulating luteal function has been suggested, as both ghrelin and its receptor (GRLN-R) have been immunohistochemically detected in human corpus luteum. Objective: We first investigate GRLN-R mRNA expression in mid-luteal phase human luteal cells. Ghrelin effect on basal and hCG-stimulated progesterone (P) release was then analyzed. Finally, we investigated whether ghrelin could affect luteal release of vascular endothelial growth factor (VEGF), prostaglandin (PG) E2 (PGE2) -both luteotropic factors- and PGF2alpha -luteolytic modulator. Ghrelin effect on both basal and hypoxia-stimulated VEGF luteal expression was analyzed. Methods: Human luteal cells were incubated for 24h with ghrelin (10(-13)-10(-7) M) or hCG (100 ng/ml) or CoCl2 (10 microM) -chemical hypoxia- or with hCG or CoCl2 in combination with ghrelin. Both GRLN-R mRNA and VEGF mRNA were evaluated by real-time RT-PCR. PGs and P release was assayed by RIA, while VEGF release by ELISA. Results: GRLN-R mRNA expression was demonstrated in human luteal cells. Both basal and hCG-stimulated P release was significantly decreased by ghrelin, that was able to reduce PGE2 and increase PGF2alpha luteal release. Both basal and hypoxia-stimulated VEGF release was significantly decreased by ghrelin, that did not affect VEGF mRNA luteal expression. Conclusions: The present in vitro study provides the first evidence of a direct inhibitory influence of ghrelin on human luteal function.
The effect of obestatin on porcine ovarian granulosa cells. M??sov? et al. The aim of our in vitro experiments was to investigate the role of obestatin, a newly discovered metabolic hormone produced in the stomach and other tissues, in the direct control of ovarian cell proliferation, apoptosis and secretion. Porcine granulosa cells were cultured in the presence of obestatin (0, 1, 10 and 100ng/ml medium). The expression of intracellular peptides associated with proliferation (PCNA, cyclin B1, MAP kinase), as well as markers of apoptosis (Bax, p53, Caspase 3), were detected using immunocytochemistry and Western immunoblotting. Secretion of progesterone (P(4)), testosterone (T) and estradiol (E(2)) was measured by EIA. Addition of obestatin (1-100ng/ml) to the culture medium significantly stimulated the expression of PCNA and resulted in an increase in expression of cyclin B1 and MAPK. It also significantly increased the percentage of cells containing the apoptotic and anti-proliferating peptides p53, Caspase 3 and Bax. At 10 and 100ng/ml, obestatin promoted the secretion of P(4), but not T or E(2). Our results are the first demonstration that obestatin directly controls porcine ovarian cell functions: it can stimulate proliferation (accumulation of rPCNA, cyclin B1 and MAPK), apoptosis (expression of p53, Caspase 3 and Bax) and the secretion of progesterone.
GHRELIN INHIBITS STEROID BIOSYNTHESIS BY CULTURED GRANULOSA-LUTEIN CELLS. Viani I et al. Contex: Growing evidence indicates that ghrelin may participate in the regulation of different aspects of the reproductive function. The genes encoding for this peptide and its receptor are expressed in the human ovary, but their functional role is still unknown. Objective: The aim of our study was to assess whether ghrelin has any effect on steroid synthesis by human granulosa-lutein cells, and identify the receptor isoform through which this potential effect is exerted. Design, patients and methods: Thirty five women with spontaneous ovulatory cycles undergoing in vitro fertilization for infertility due to uni- or bilateral tubal impatency or male factor were studied. Granulosa- lutein cells obtained from follicular fluid were incubated with increasing amounts of human acylated ghrelin (10(-11) to 10(-7) mol/L) either alone or together with a 1:500 concentration of a specific anti-ghrelin receptor antibody (GHS-R1a). Culture media were tested for estradiol (E2) and progesterone (P4). The expression of GHS-R1a and GHS-R1b in human granulosa-lutein cells was also studied by Real Time Quantitative PCR. Results: Estradiol and progesterone concentrations in the culture media were significantly reduced by ghrelin in a dose-dependent fashion. The maximal decrease in E2 (25%) and P4 (20%) media concentrations was obtained with the 10(-7) and 10(-8) mol/L ghrelin concentrations, respectively. The inhibitory effect of all ghrelin concentrations used was antagonized by the specific anti-ghrelin receptor-1a antibody added to the culture media and not by the specific anti-ghrelin receptor-1b antibody. Both 1a and 1b isoforms of the GHS-R were expressed in human granulosa-lutein cells, with the latter exceeding the former's expression (GHS-R1b/GHS-R1a ratio: 143.23 +/- 28.15). Conclusions: Ghrelin exerts an inhibitory effect on granulosa-lutein cells steroidogenesis by acting through its functional GHS-R1a receptor. This suggests that ghrelin may serve an autocrine-paracrine role in the control of gonadal function, and be part of a network of molecular signals responsible for the coordinated control of energy homeostasis and reproduction.
Serum and follicular fluid ghrelin levels negatively reflect human oocyte quality and in?vitro embryo development. Li L et al. OBJECTIVE: To characterize serum and follicular fluid (FF) ghrelin in women undergoing assisted reproduction and to evaluate ghrelin's impact on ovarian steroidogenesis, oocyte quality, and embryo development. DESIGN: Prospective cohort study. SETTING: University-based center for assisted reproduction. PATIENT(S): Normal weight women (n = 31) without endocrinopathies undergoing IVF. INTERVENTION(S): Fasting serum and FF from individual preovulatory follicles (n = 81) were collected. MAIN OUTCOME MEASURE(S): Ghrelin, insulin, ovarian steroids, and IVF outcomes including oocyte maturity and embryo development were assessed. RESULT(S): The FF ghrelin correlated highly with serum levels and was 13% (3%-24%) lower. Levels were not associated with body mass or exogenous gonadotropins. Serum ghrelin correlated negatively with the cleavage rate and number of viable day 3 embryos. Embryos with successful cleavage and viable morphology came from follicles with lower ghrelin-odds ratios were 3.67 (1.02-13.14) and 3.46 (1.01-11.81), respectively. The FF ghrelin correlated negatively with FF insulin and progesterone, and positively with estradiol. The FF insulin was more than 50% higher (? = 1.88 [0.31-3.45] uIU/mL) in follicles with successfully cleaved embryos. CONCLUSION(S): The FF ghrelin does not reflect ovarian production and likely represents transudation. Ghrelin in FF correlates with local steroidogenesis and FF insulin expression. Serum and FF ghrelin are reflective of embryo development, possibly through interactions with FF insulin.
Expression regulated by
Comment
Reduced serum ghrelin in a putative postmenopausal polycystic ovary syndrome phenotype. Krentz AJ et al. We measured fasting serum ghrelin concentrations in a cohort of community-dwelling postmenopausal women with a putative polycystic ovary syndrome (PCOS) phenotype. Ghrelin levels were reduced in women with the phenotype compared with nonaffected control women, supporting our hypothesis that a phenotype analogous to PCOS can be identified in postmenopausal women.
Ovarian localization
Luteal cells, Stromal cells
Comment
Expression and localization of ghrelin and its functional receptor in?corpus luteum during different stages of estrous cycle and the modulatory role of ghrelin on progesterone production in cultured luteal?cells in buffalo. Gupta M 2014 et al.
Evidence obtained during recent years provided has insight into the regulation of corpus luteum (CL) development, function, and regression by locally produced ghrelin. The present study was carried out to evaluate the expression and localization of ghrelin and its receptor (GHS-R1a) in bubaline CL during different stages of the estrous cycle and investigate the role of ghrelin on progesterone (P4) production along with messenger RNA (mRNA) expression of P4 synthesis intermediates. The mRNA and protein expression of ghrelin and GHS-R1a was significantly greater in mid- and late luteal phases. Both factors were localized in luteal cells, exclusively in the cytoplasm. Immunoreactivity of ghrelin and GHS-R1a was greater during mid- and late luteal phases. Luteal cells were cultured in?vitro and treated with ghrelin each at 1, 10, and 100?ng/mL concentrations for 48?h after obtaining 75% to 80% confluence. At a dose of 1?ng/mL, there was no significant difference in P4 secretion between control and treatment group. At 10 and 100?ng/mL, there was a decrease (P < 0.05) in P4 concentration, cytochrome P45011A1 (CYP11A1), and 3-beta-hydroxysteroid dehydrogenase mRNA expression and localization. There was no difference in mRNA expression of steroidogenic acute regulatory protein between control and treatment group. In summary, the present study provided evidence that ghrelin and its receptor are expressed in bubaline CL and are localized exclusively in the cell cytoplasm and ghrelin has an inhibitory effect on P4 production in buffalo.
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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). Gnanapavan S, et al . Caminos JE, et al 2003 reported the expression of ghrelin in the cyclic and pregnant rat ovary.
Persistent expression of ghrelin gene was demonstrated in rat ovary throughout the estrous cycle, although its relative mRNA levels varied depending on the stage of the cycle, with the lowest levels in proestrus and peak expression values on diestrous d 1, i.e. during the luteal phase of the cycle. Ghrelin immunoreactivity was predominantly located in the luteal compartment of the ovary; with intense immunostaining being detected in steroidogenic cells from corpus luteum of the current cycle as well as in all generations of regressing corpora lutea. Indeed, predominant expression of ghrelin in the corpus luteum was confirmed using a pseudopregnant rat model, where maximum ghrelin mRNA levels were detected in dissected luteal tissue. To note, the cyclicity in the profile of ovarian expression of ghrelin appeared to be tissue specific, as it was not detected in the stomach, nor was it observed in terms of circulating ghrelin levels. In addition, cyclic expression of ovarian ghrelin mRNA was disrupted by blockade of the preovulatory gonadotropin surge and ovulation by means of administration of a potent GnRH antagonist. Finally, ghrelin mRNA expression was persistently detected in rat ovary throughout pregnancy, with higher levels in early pregnancy and lower expression during the later part of gestation. In conclusion, our data provide novel evidence for the expression of ghrelin in the cyclic and pregnant rat ovary. Dynamic changes in the profile of ghrelin expression were detected during the estrous cycle and throughout pregnancy, thus suggesting a precise regulation of ovarian expression of ghrelin. Overall, our present findings may represent an additional link between body weight homeostasis and female reproductive function.
Follicle stages
Corpus luteum
Comment
Gaytan F, et al reported the immunolocalization of ghrelin and its functional receptor, the type 1a growth hormone secretagogue receptor, in the cyclic human ovary.
Ghrelin is a novel 28-amino acid peptide identified as the endogenous ligand for the GH secretagogue receptor (GHS-R). Besides its hallmark central neuroendocrine effects in the control of GH secretion and food intake, an unexpected reproductive facet of ghrelin has recently emerged because expression of this molecule and its cognate receptor has been demonstrated in rat testis. The authors assessed the presence and cellular location of ghrelin and its functional receptor, namely the type 1a GHS-R, in the cyclic human ovary by means of immunohistochemistry using specific polyclonal antibodies. Strong ghrelin immunostaining was demonstrated in ovarian hilus interstitial cells. In contrast, ghrelin signal was not detected in ovarian follicles at any developmental stage, nor was it present in newly formed corpora lutea (CL) at very early development. However, specific ghrelin immunoreactivity was clearly observed in young and mature CL, whereas expression of the peptide disappeared in regressing luteal tissue. Concerning the cognate receptor, ovarian expression of GHS-R1a protein showed a wider pattern of tissue distribution, with detectable specific signal in oocytes as well as somatic follicular cells; luteal cells from young, mature, old, and regressing CL; and interstitial hilus cells. Of particular note, follicular GHS-R1a peptide expression paralleled follicle development with stronger immunostaining in granulosa and theca layers of healthy antral follicles. In conclusion, ghrelin and its functional type 1a receptor are expressed in the cyclic human ovary with distinct patterns of cellular location. The presence of both components (ligand and receptor) of the ghrelin signaling system within the human ovary opens up the possibility of a potential regulatory role of this novel molecule in ovarian function under physiological and pathophysiological conditions.
Phenotypes
PCO (polycystic ovarian syndrome)
Mutations
2 mutations
Species: human
Mutation name: type: naturally occurring fertility: subfertile Comment: Association of -604G/A and -501A/C Ghrelin and Obestatin Prepropeptide Gene Polymorphisms with Polycystic Ovary Syndrome. Ghaleh TD et al. (2017) Ghrelin hormone has an important role in a wide range of metabolic and non-metabolic processes. Polymorphisms of ghrelin gene could be associated with a large number of diseases. The aim of this study was to evaluate the association of -604G/A and -501A/C polymorphisms in ghrelin and obestatin prepropeptide gene (GHRL) with polycystic ovary syndrome (PCOS) in a sample of Iranian women. One hundred and fifty-two women with PCOS and 162 age-matched apparently healthy women as control group were enrolled in this study. The study subjects were genotyped for polymorphisms in the ghrelin gene using polymerase chain reaction-restriction fragment length polymorphism-based methods. Biochemical parameters, serum prolactin, luteinizing hormone, follicle stimulating hormone, estradiol, and testosterone were estimated by chemiluminescence assay. Serum lipids and lipoproteins were determined by standard enzymatic methods. The association between the risk of PCOS and ghrelin gene polymorphisms was examined using Multivariate analysis. The frequency of the -604G/A and -501A/C polymorphisms was not statistically different between patients and the control group of women (p = 0.12 and p = 0.21, respectively). A significantly higher level of LDL-C was found in the wild-type AA genotype compared with CC genotype of -501A/C polymorphism (p = 0.02). Our findings indicate that neither -604G/A and nor -501A/C polymorphisms of ghrelin gene are associated with PCOS, but suggest a relation between the presence of polymorphic allele of -501A/C polymorphism and LDL-C level in a sample of Iranian women.//////////////////
Species: mouse
Mutation name: type: None fertility: subfertile Comment: Acylated Ghrelin Supports the Ovarian Transcriptome and Follicles in the Mouse: Implications for Fertility. Sominsky L et al. (2019) Ghrelin, an orexigenic gut-derived peptide, is gaining increasing attention due to its multifaceted role in a number of physiological functions, including reproduction. Ghrelin exists in circulation primarily as des-acylated and acylated ghrelin. Des-acyl ghrelin, until recently considered to be an inactive form of ghrelin, is now known to have independent physiological functionality. However, the relative contribution of acyl and des-acyl ghrelin to reproductive development and function is currently unknown. Here we used ghrelin-O-acyltransferase (GOAT) knockout (KO) mice that have no measurable levels of endogenous acyl ghrelin and chronically high levels of des-acyl ghrelin, to characterize how the developmental and life-long absence of acyl ghrelin affects ovarian development and reproductive capacity. We combined the assessment of markers of reproductive maturity and the capacity to breed with measures of ovarian morphometry, as well as with ovarian RNA sequencing analysis. Our data show that while GOAT KO mice retain the capacity to breed in young adulthood, there is a diminished number of ovarian follicles (per mm3) in the juvenile and adult ovaries, due to a significant reduction in the number of small follicles, particularly the primordial follicles. We also show pronounced specific changes in the ovarian transcriptome in the juvenile GOAT KO ovary, indicative of a potential for premature ovarian development. Collectively, these findings indicate that an absence of acyl ghrelin does not prevent reproductive success but that appropriate levels of acyl and des-acyl ghrelin may be necessary for optimal ovarian maturation.//////////////////