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1.
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2.
We have previously produced human growth hormone (hGH) transgenic (TG) rats that show low circulating levels of both hGH and endogenous rat GH. Although body length of the TG rats is normal, they develop hyperphagia and severe obesity. The present study was undertaken to elucidate the causes of hyperphagia in the TG rats by focusing on temporal changes in plasma ghrelin levels and hypothalamic neuropeptide Y (NPY) contents. In both wild-type (WT) and TG rats, the highest value of plasma ghrelin levels was observed just before the dark phase, and thereafter plasma ghrelin levels were maintained higher in the TG than WT rats. Although NPY contents also showed the peak level just before the dark phase in both the arcuate (ARC) and paraventricular nuclei (PVN) of the hypothalamus, the values in the ARC, but not the PVN, of the TG rats was always lower than those of the WT rats, suggesting increased transport of NPY from the ARC to PVN in the TG rats. In addition, treatment with antagonists for Y1 and Y5 receptors for NPY reduced food intake much more effectively in the TG than WT rats. Intermittent treatment with recombinant hGH for a week significantly decreased food consumption, adipose tissue weight and plasma triglyceride concentrations in the TG rats. These results suggest that, in the TG rats, insufficiency in circulating GH stimulates the ghrelin-NPY system with a resultant increase in food intake.  相似文献   

3.
This is a test-report of ghrelin levels in plasma and proventriculus, the glandular portion of the avian stomach, by using a specific radioimmunoassay for acylated ghrelin, as well as the expression of the ghrelin gene in the proventriculus after a 12-h fasting period followed by a 6-h feeding period with 6-day-old layer chicks. After fasting, the plasma ghrelin levels increased from 21.3 ± 4.5 to 32.9 ± 5.0 fmol/ml, but once refed it returned to the control value. After fasting, the ghrelin mRNA and the peptide levels in the proventriculus increased, and ghrelin mRNA levels remained high but once refed the ghrelin content returned to the control level. Furthermore, in order to examine the effect of increased circulating ghrelin on food intake, a bolus intravenous injection of 500 pmol of chicken ghrelin was given to 8-day-old chicks. The ghrelin injection did not cause any significant changes in food intake. These results indicate that the levels of ghrelin and its mRNA with layer chicks are altered according to the feeding state and this in a similar manner as has been observed in mammals. Unlike in mammals, an increase in circulating ghrelin does not cause the promotion of food intake in chicks.  相似文献   

4.
Ghrelin is a highly conserved peptide hormone secreted by the stomach, which is involved in the regulation of food intake and energy expenditure. Ghrelin stimulates growth hormone (GH) release, and increases appetite in a variety of mammalian and non-mammalian vertebrates, including several fish species. Studies were conducted to investigate the effect of feeding and fasting on plasma and stomach ghrelin, and the growth hormone/insulin-like growth factor I (IGF-I) axis in the Mozambique tilapia, a euryhaline teleost. No postprandial changes in plasma and stomach ghrelin levels or stomach ghrelin mRNA levels were observed. Plasma levels of GH, IGF-I and glucose all increased postprandially which agrees with the anabolic roles of these factors. Fasting for 4 and 8 d did not affect ghrelin levels in plasma or stomach. Plasma GH was elevated significantly after 4 and 8 d of fasting, while plasma IGF-I levels were reduced. Plasma ghrelin levels were elevated significantly after 2 and 4 wk of fasting, but no change was detected in stomach ghrelin mRNA levels. Four weeks of fasting did not affect plasma GH levels, although plasma IGF-I and glucose were reduced significantly, indicating that GH resistance exists during a prolonged nutrient deficit (catabolic state). These results indicate that ghrelin may not be acting as a meal-initiated signal in tilapia, although it may be acting as a long-term indicator of negative energy balance.  相似文献   

5.
Effect of intracerebroventricular orexin-B on food intake in sheep.   总被引：6，自引：0，他引：6  
Orexin is a hypothalamic neuropeptide that regulates feeding behavior in rats. Orexin-B has recently been cloned in pigs and was shown to stimulate food intake after intramuscular injection. This study was designed to determine whether intracerebroventricular (ICV) and intravenous injections of orexin could regulate appetite in sheep. Suffolk wethers were moved to indoor facilities, adapted to diets for 6 wk, and trained to stand in stanchions for 3 to 6 h each day for 2 wk before indwelling ICV cannulas were installed. These sheep were provided water and they consumed feed ad libitum. On the day before an experiment, each sheep was cannulated in a jugular vein. On the day of an experiment, sheep were placed in stanchions and allowed to stand for 1 h before use. Sheep were then monitored over a 2-h control period before i.v. injection with saline or porcine orexin-B (3 micrograms/kg BW) or ICV injection with artificial cerebrospinal fluid (CSF), orexin (0.03, 0.3, or 3 micrograms/kg BW) or in a second experiment with either orexin B (0.03, 0.3, 3 micrograms/kg BW), neuropeptide-Y (NPY; 0.3 microgram/kg BW), or orexin plus NPY. Food intake was monitored for consecutive 2-h periods. The i.v. injections of orexin did not affect food intake or metabolite or hormone concentrations. In ICV sheep, orexin increased food intake at 2 (P < 0.04) and at 4 h (P < 0.02). Food intake was greatest with the 0.3 microgram/kg BW dosage of orexin (P < 0.05). In the first 2 h after injection, orexin had an effect similar to that of NPY (0.23 kg for orexin and 0.2 kg for NPY). The combination of NPY and orexin had a greater effect on food intake (to 0.34 kg) than did either orexin (P < 0.05) or NPY (P < 0.008) alone. Differences were not apparent in the subsequent 2-h interval. No differences were noted in free fatty acid, glucose, growth hormone, luteinizing hormone, or insulin concentrations following orexin injection. There was an effect of ICV orexin treatment on plasma cortisol concentrations (P < 0.002). Cortisol was increased by orexin at the 0- to 2-h (P < 0.008) and in the 2- to 4-h (P < 0.009) intervals after orexin injection. These data indicate that central administration of orexin stimulates feed intake in sheep.  相似文献   

6.
Ghrelin, neuropeptide Y (NPY) and cholecystokinin (CCK) all have important roles in the regulation of feeding in fish and mammals. To better understand the role of the three peptides in appetite regulation in the early developmental stages of blunt snout bream (Megalobrama amblycephala), partial cDNA sequences of ghrelin, NPY and CCK genes were cloned. And then, real‐time quantitative PCR and RT‐PCR were used to detect and quantify the mRNA expressions of these genes from zygotes to larvae of 50 days after hatching (DAH). Ghrelin, NPY and CCK were all expressed throughout the embryonic and larval development stages, and the expression levels were higher in larval stages than in embryonic stages. Ghrelin and NPY mRNA expressions were upregulated at 1, 3, 5 DAH, while CCK mRNA expression was reduced significantly at 3 DAH. The mRNA expression levels of three genes in larvae varied significantly until 30 DAH. In adult fish, all three peptides were detected to be expressed in brain and several peripheral tissues. Ghrelin mRNA was mainly expressed in the intestine, whereas NPY and CCK mRNAs were mainly expressed in the brain. Taken together, these results indicate that ghrelin, NPY and CCK may have roles in early development and participate in the regulation of feeding of larvae in blunt snout bream and will be helpful for further investigation into feed intake regulation in adults of this species.  相似文献   

7.
These studies were conducted to determine whether ghrelin, a 28-amino acid peptide produced mainly by the stomach, was involved in tryptophan-mediated appetite stimulation in swine. In experiment 1, 36 crossbred (Long WhitexLarge White) barrows were used in a 2x3 factorial design to determine the effects of food intake (ad libitum versus limit fed) and tryptophan level (0.12%, 0.19% and 0.26%) on growth performance as well as ghrelin expression, plasma insulin, ghrelin and leptin levels. Ad libitum fed pigs gained more weight, but had poorer feed conversion than limit fed pigs. Weight gain, food intake and feed conversion all improved with increased ingestion of dietary tryptophan. Ad libitum feeding increased plasma insulin. Plasma insulin was unaffected by the level of dietary tryptophan. However, plasma leptin was significantly lower in pigs fed 0.19% tryptophan compared to those fed 0.12% tryptophan. Plasma ghrelin levels and ghrelin mRNA level in gastric fundus and duodenun was significantly higher in pigs fed 0.19% and 0.26% tryptophan diet compared with pigs fed 0.12%. In the second experiment, 18 crossbred barrows were divided into three treatments involving oral infusion of saline, tryptophan (40mg/kg BW) or 5-hydroxytryptophan (40mg/kg BW). Plasma ghrelin levels at 20, 40 and 60min after infusion of tryptophan were higher than after saline and 5-hydroxytryptophan infusion, 5-hydroxytryptophan infusion induced lower food intake than saline infusion, and tryptophan infusion increased food intake 2, 8 and 24h after infusion. In conclusion, oral tryptophan ingestion increased ghrelin expression in gastric fundus and plasma ghrelin level.  相似文献   

8.
The presence of neuropeptide Y (NPY) in the brain and retina of gilthead seabream (Sparus aurata L.) was investigated for the first time. For this investigation we employed an immunoperoxidase technique and the western immunoblot analysis using an antiserum raised against porcine NPY. The results showed that NPY-immunoreactivity was widely distributed in the brain of S. aurata. In particular, we have found NPY-immunoreactive (ir) neurons in the area ventralis telencephali pars centralis and pars lateralis, in the area dorsali telencephali pars centralis subdivision two and in nucleus intermedius thalami. An intense NPY-ir was detected in the telencephalon, in the optic tectum, in the thalamus, hypothalamus and in the vagal lobes. Scarce positive fibres were seen in the olfactory bulbs. NPY-ir amacrine cells were observed in the retina. The western immunoblot analysis revealed a protein band with a mobility corresponding to that of synthetic NPY. Our findings are, in general, in agreement with those obtained in other teleosts. The extensive distribution of NPY indicates for this peptide a key role in basic physiological actions, including visual and gustatory inputs processing.  相似文献   

9.
The aim of this study was to determine the distribution of Neuropeptide-Y (NPY) immunoreactive neurons and fibres in the brain and pituitary of Odontesthes bonariensis by immunohistochemical methods. A wide distribution of immunoreactive NPY (ir-NPY) cells and fibres in the forebrain and midbrain was observed. A prominent ir-NPY nucleus was found in the ventral telencephalon and other ir-NPY cells groups were recognized at the dorso-medial telencephalon. The diencephalon showed ir-NPY cells in the Nucleus entopeduncularis, the Nucleus preopticus periventricularis and in the Nucleus lateralis tuberis. Ir-NPY fibres were conspicuous in the preoptic region and the hypothalamus. There were also numerous ir-NPY fibres at the epithalamic level running ventrally to the hypothalamus and the pituitary stalk. At the rhomboencephalic level, the ir-NPY neurons were observed in the Locus coeruleus. Double-labelled immunostaining showed a close association between ir-NPY fibres that reach the adenohypophysis and growth hormone (GH)- and gonadotropin (GtH)-expressing cells. Although our results exhibit some relevant differences when compared to other fish groups, they support the existence of a conserved NPY system in teleosts.  相似文献   

10.
Glucocorticoids are known to hinder somatic growth in a number of vertebrate species. In order to better understand the mechanisms through which they may act in channel catfish, we examined the effects of feeding cortisol on the growth hormone (GH)/insulin-like growth factor-I (IGF-I)/IGF-binding protein (IGFBP) network. Fish (30.6 ± 3.0 g) were fed once daily for 4 weeks and treatments included: (1) High-cortisol (dietary cortisol provided at 400 mg/kg feed), (2) Low-cortisol (dietary cortisol provided at 200 mg/kg feed), and (3) Control (commercial catfish feed). Fish fed diets with cortisol weighed approximately 50% less than Controls. Feed intake was reduced by approximately 30% in both treatments of cortisol fed fish compared to Controls. A 20-kDa IGFBP was observed in plasma from High- and Low-treated fish while it was not detected in Control fish plasma. High-cortisol treatment increased pituitary GH mRNA expression approximately 10-fold while liver IGF-I mRNA expression was not different between cortisol-treated fish and Controls. Cortisol treatments decreased plasma levels of IGF-I. These data indicate that feeding cortisol for 4 weeks reduces weight gain, feed intake, and plasma levels of IGF-I and induces a 20-kDa IGFBP. One mechanism through which cortisol may impede growth of catfish is through an increase in a low molecular weight IGFBP which may lead to inhibitory effects on the action of IGF-I.  相似文献   

11.
ABSTRACT: Feed intake control is vital to ensuring optimal nutrition and achieving full potential for growth and development in poultry. The aim of the present study was to investigate the effects of L-leucine, L-glutamate, L-tryptophan and L-arginine on feed intake and the mRNA expression levels of hypothalamic Neuropeptide involved in feed intake regulation in broiler chicks. Leucine, glutamate, tryptophan or arginine was intra-cerebroventricularly (ICV) administrated to 4d-old broiler chicks respectively and the feed intake were recorded at various time points. Quantitative PCR was performed to determine the hypothalamic mRNA expression levels of Neuropeptide Y (NPY), agouti related protein (AgRP), pro-opiomelanocortin (POMC), melanocortin receptor 4 (MC4R) and corticotrophin releasing factor (CRF). Our results showed that ICV administration of L-leucine (0.15 or 1.5 mumol) significantly (P < 0.05) increased feed intake up to 2 h post-administration period and elevated both hypothalamic NPY and AgRP mRNA expression levels. In contrast, ICV administration of L-glutamate (1.6 mumol) significantly (P < 0.05) decreased feed intake 0.25, 0.5 and 2 h post-injection, and increased hypothalamic CRF and MC4R mRNA expression levels. Meanwhile, both L-tryptophan (10 or 100 mug) and L-arginine (20 or 200 mug) had no significant effect on feed intake. These findings suggested that L-leucine and L-glutamate could act within the hypothalamus to influence food intake, and that both orexigenic and anorexigenic Neuropeptide genes might contribute directly to these effects.  相似文献   

12.
The acute effect of leptin on the regulation of food intake was investigated in layer and broiler chickens. In an initial study, we observed that a single intraperitoneal injection of recombinant chicken leptin (1 mg/kg BW) dramatically reduced (38%) food intake in 56-day-old layer chickens, more moderately reduced (15%) food intake in 9-day-old layer chicks, and had no significant effect in 9-day-old broiler chicks. In a subsequent study, body weight and plasma concentrations of leptin were measured weekly in layer and broiler chicks from day 1 to 35 of age and brain leptin receptor and neuropeptide Y (NPY) mRNA expression were analyzed at 1, 9, and 35 days of age. At day 1 of age, peripheral concentrations of leptin were significantly greater in layer than broiler chicks. Subsequently, despite increases in body weight and differences in growth rates between layer and broiler chicks from day 8 to day 35 of age, peripheral concentrations of leptin were constant and similar in both genotypes. Leptin receptor and NPY mRNA were expressed in brain from day 1 in chicks of both genotypes and increased significantly to day 35 of age. These observations provide evidence that the inhibitory effect of leptin on the regulation of food intake in growing chicks is an age dependent process. Furthermore, acquisition of the anorectic effect of leptin is likely to be associated with greater expression of the leptin receptor and NPY mRNAs than to changes in blood levels of leptin. Finally, this study provides evidence that chickens selected for high growth rates may be less sensitive or responsive to peripheral concentrations of leptin than chickens with low growth rates (layers), suggesting that the faster growth of broiler chicks may be related to a lessened responsiveness to anorexigenic factors.  相似文献   

13.
生长激素释放肽(Ghrelin)是一种在动物体内广泛存在的生长激素促分泌素受体(GHSR)的内源性配体, Ghrelin与位于下丘脑的GHSR结合后,具有促进生长激素释放、增加食欲、调节消化系统功能及能量代谢等作用。文章就Ghrelin的结构、分布、生物学效应及在畜牧业上的应用前景等方面进行综述,以期促进Ghrelin的进一步深入研究。  相似文献   

14.
Peripheral ghrelin reduces food intake and respiratory quotient in chicken   总被引：7，自引：0，他引：7  
Ghrelin injection, either centrally or peripherally strongly stimulates feeding in human and rodents. In contrast, centrally injected ghrelin inhibits food intake in neonatal chickens. No information is available about the mechanism and its relationship with energy homeostasis in chicken. Since ghrelin is predominantly produced in the stomach, we investigated the effect of peripherally injected ghrelin (1 nmol/100g body weight) on food intake and energy expenditure as measured in respiratory cells by indirect calorimetry for 24h in one-week-old chickens. Plasma glucose, triglycerides, free fatty acids, total protein and T(3) were measured in a separate experiment until 60 min after injection. Food intake decreased until at least 1h after intravenous ghrelin administration. The respiratory quotient (RQ) in ghrelin-injected chickens was reduced until 14 h after administration whereas plasma glucose and triglycerides concentrations were not altered. Free fatty acids and total protein levels also remained unchanged. Ghrelin did not influence heat production and this was supported by the absence of changes in plasma T(3) levels when compared to the control values. In conclusion, peripheral ghrelin reduces food intake as well as RQ and might influence the type of substrate (macronutrient) that is used as metabolic fuel.  相似文献   

15.
Central regulation of food intake in the neonatal chick   总被引：3，自引：0，他引：3  
Regulating food intake is complicated in animals including domestic birds. Just after hatching, neonatal chicks find their food by themselves and they can control food intake, since domestic chicken belongs to the precocial type of avian species. Thus, domestic chickens have relatively well-developed mechanisms of food-intake control at hatching. While many aspects of food-intake regulation in chickens appear similar to that in mammals, there are some responses that are unique to chickens. For instance, some neurotransmitters such as neuropeptide Y (NPY), orexin-A, orexin-B, motilin, melanin-concentrating hormone (MCH), galanin, growth hormone releasing factor (GRF) and ghrelin stimulate feeding in mammals. Only NPY strongly stimulates food intake in birds similar to that observed in mammals; however, both orexins, motilin, MCH and galanin failed to alter food intake of the chick. Moreover, GRF and ghrelin suppressed feeding of chicks. On the other hand, cholecystokinin (CCK), gastrin, glucagon-like peptide-1 (GLP-1), corticotropin-releasing factor (CRF), histamine, α-melanocyte stimulating hormone (α-MSH), leptin and bombesin are known to suppress feeding in mammals. These responses are similar to those of mammals except for leptin. Therefore, the inhibitory mechanisms for feeding are well conserved in chicks.  相似文献   

16.
Ghrelin, an orexigenic hormone, is the endogenous ligand for the growth hormone secretagogue receptor (GHSR). Obestatin is produced from the same precursor peptide as ghrelin, and although obestatin was initially thought to promote actions opposite to those of ghrelin, many studies have failed to confirm this hypothesis. In the current study, multiparous cows were continuously infused with ghrelin (n = 10) or obestatin (n = 10) for 8 wk and compared to an untreated group (n = 10) to examine the effects of these hormones on somatotropic and liporegulatory gene expression. The expression of key genes was measured by quantitative real-time polymerase chain reaction. Growth hormone secretagogue receptor mRNA expression was altered in ghrelin- and obestatin-infused cows in a similar manner, as expression was increased at 4 wk, however it had decreased by 8 wk. Obestatin-infused cows presented with a significant decrease in the expression of ATP-binding cassette A1 (ABCA1) in adipose tissue, suggesting changes in cholesterol transport. Liver insulin-like growth factor (IGF) binding protein-3 mRNA displayed a week-by-treatment interaction, as expression was increased in control and obestatin-infused cows; however, expression decreased in ghrelin-infused cows. Adipose expression of hormone sensitive lipase (LIPE) mRNA was not altered by treatment or time, suggesting hormone infusion is not initiating lipolysis. The expression of lipogenic genes in adipose tissue increased with time in all groups, consistent with the general lactational profile of lipogenesis in dairy cows. These data indicate that continuous infusion of ghrelin or obestatin does not alter the expression of key somatotropic or liporegulatory genes in the lactating dairy cow, although obestatin infusion may alter cholesterol transport.  相似文献   

17.
生长激素释放肽(ghrelin)是在大鼠和人胃内发现的,是一种生长激素促分泌素受体(growth hormone secretagogue receptor,GHSR)的内源性配体.ghrelin与位于垂体、下丘脑的GHSR结合后,具有促进生长激素释放、增加食欲、调节消化系统功能和能量代谢等作用.本文对ghrelin的...  相似文献   

18.
The participation of peripheral peptides in the processes regulating the food intake (energy homeostasis) at the central nervous system level remains unclear. This study focuses on the role of obestatin in neuronal activity within the hypothalamic appetite‐regulating network in ruminants. The animals (n = 28) were randomly divided into two groups. The sheep in the control group received intracerebroventricular infusions of the Ringer‐Locke solution, and the sheep in obestatin group were infused with obestatin (diluted in the Ringer‐Locke solution) at 25 μg per 120 μl/hr. The series of four 1‐hr infusions on 3 consecutive days were performed, and immediately after the experiment, the sheep were decapitated. Selected brain regions were fixed in situ for further immunohistochemical analysis, while the remaining ones were frozen for real‐time RT‐qPCR analysis. Obestatin infusion elicited changes in the neuropeptide Y (NPY) neuronal network in the hypothalamus. The results obtained show that exogenous obestatin evoked an increase in npy and agrpmRNA expression in the mediobasal hypothalamus (MBH), while the immunoreactivity for NPY was decreased in the arcuate and periventricular nuclei. The increase in cart and pomcmRNA expression in the MBH was also observed. Moreover, increased levels of gpr39 receptor and npy receptor 1 mRNA expression were evident in obestatin‐infused sheep. Based on these results, it can be concluded that obestatin plays a role in the modulation of appetite‐regulating network at the central level in sheep. The results obtained suggest that the underlying mechanism may involve the modification of the activity of NPY/AgRP and CART/α‐MSH neurons in the arcuate nucleus.  相似文献   

19.
Melanin-concentrating hormone (MCH) stimulates feeding when injected intracerebroventricularly (ICV) in rats. At present it is not clear whether the function of MCH is similar in ruminants, which are species with a continuous delivery of nutrients. Therefore the current investigation sought to determine the role of MCH in sheep. In the first experiment, six, castrate male sheep were satiated and received one of four treatments [saline, 0.1, or 1.0 nmol/kg MCH, and NPY (0.1 nmol/kg)] injected ICV over 30s, then infused ICV for 6 h ( approximately 500 microl/h). Food intake was measured for 2 h before and at 2, 4, 6, 8, 12 and 24 h. In this experiment, feed intake was increased (P相似文献   

20.
The expression of activin and inhibin has been demonstrated in the hypothalamus, but their physiological roles in the brain remain to be elucidated. In the present study, involvement of activin and inhibin in the regulation of food and water intake was examined. Male rats were deprived of food or water for 12 and 60 hr, and mRNA levels of activin/inhibin alpha, betaA and betaB subunits in the hypothalamus were estimated by RT-PCR. Gene expression of alpha subunit transiently decreased at 12 hr of food deprivation, while it did not change during water deprivation. Food and water deprivation for 60 hr increased mRNA levels of betaA and betaB subunits, respectively. These results indicated that gene expression of each subunit was independently regulated. Injection of activin A (0.5 and 4.0 microg) into the third ventricle decreased food intake. Water intake was suppressed by 4.0 microg, but not 0.5 microg, of activin A. Intracerebroventricular injection of inhibin A (0.5 and 4.0 microg) decreased water intake in a dose dependent manner without affecting food intake, suggesting that inhibin could act independently of activin. Taken together, it is suggested that activin and inhibin take part in the central regulation of nutrient and fluid balance, though further study is needed to determine precise molecular species involved.  相似文献   

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