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Jönsson E, Kaiya H, Björnsson BT. Ghrelin decreases food intake in juvenile rainbow trout (Oncorhynchus mykiss) through the central anorexigenic corticotropin-releasing factor system. Gen Comp Endocrinol 2010; 166:39-46. [PMID: 19896947 DOI: 10.1016/j.ygcen.2009.11.001] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 09/11/2009] [Accepted: 11/02/2009] [Indexed: 01/25/2023]
Abstract
Ghrelin stimulates pituitary growth hormone (GH) release, and has a key role in the regulation of food intake and adiposity in vertebrates. To investigate the central effect of native rainbow trout ghrelin (rtghrelin) on food intake in rainbow trout, as well as its possible mode of action, four groups of fish received a single injection into the third brain ventricle (i.c.v. injection): (1) control group (physiological saline) (2) ghrelin-treated group (2.0 ng rtghrelin g bwt(-1)), (3) group given the corticotropin-releasing hormone receptor antagonist alpha-helical CRF 9-41 (ahCRF) (4.0 ng g bwt(-1)) and (4) group receiving the same dose of both ghrelin and ahCRF. Food intake was assessed 1h after treatment. In addition, the presence of the GHS-R (the ghrelin receptor) in the rainbow trout CNS was examined with Western blot. To investigate peripheral effects of ghrelin, rainbow trout received an intraperitoneal cholesterol-based implant with or without rtghrelin, and daily food intake was measured during 14 days. Weight and length were measured at the start and termination of the experiment and specific growth rates were calculated. Mesenteric fat stores, muscle and liver lipid content were analysed after the treatment period. Central ghrelin injections decreased food intake compared with controls, and treatment with ahCRF abolished the ghrelin-effect. Western blot analysis of the GHS-R revealed a single band at around 60 kDa in pituitary, hypothalamus, brain and stomach. Long-term peripheral ghrelin treatment decreased daily food intake compared with controls. This was reflected in a ghrelin-induced decrease in weight growth rate (p<0.06). There was no effect of ghrelin on plasma GH levels or tissue fat stores. The conclusion from this study is that the GHS-R is indicated in the CNS in rainbow trout and that ghrelin may act there as an anorexigenic hormone, through a CRF-mediated pathway. Elevated peripheral ghrelin levels also seem to lead to decreased feed intake in the longer term.
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Affiliation(s)
- Elisabeth Jönsson
- Fish Endocrinology Laboratory, Department of Zoology/Zoophysiology, University of Gothenburg, Box 463, S-405 30 Göteborg, Sweden.
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202
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Tong J, Tschöp MH, Aulinger BA, Davis HW, Yang Q, Liu J, Gaylinn BD, Thorner MO, D'Alessio D, Tso P. The intestinal lymph fistula model--a novel approach to study ghrelin secretion. Am J Physiol Gastrointest Liver Physiol 2010; 298:G474-80. [PMID: 20044509 PMCID: PMC2838510 DOI: 10.1152/ajpgi.00367.2009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
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.
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Affiliation(s)
- Jenny Tong
- Departments of Medicine, University of Cincinnati, Ohio, 45267-0547, USA.
| | - Matthias H. Tschöp
- Departments of 1Medicine, Division of Endocrinology, Diabetes and Metabolism, and
| | - Benedikt A. Aulinger
- Departments of 1Medicine, Division of Endocrinology, Diabetes and Metabolism, and
| | - Harold W. Davis
- Departments of 1Medicine, Division of Endocrinology, Diabetes and Metabolism, and
| | - Qing Yang
- 2Pathology, University of Cincinnati, Cincinnati, Ohio;
| | - Jianhua Liu
- 3Department of Medicine, Division of Endocrinology and Metabolism, University of Virginia, Charlottesville, Virginia
| | - Bruce D. Gaylinn
- 3Department of Medicine, Division of Endocrinology and Metabolism, University of Virginia, Charlottesville, Virginia
| | - Michael O. Thorner
- 3Department of Medicine, Division of Endocrinology and Metabolism, University of Virginia, Charlottesville, Virginia
| | - David D'Alessio
- Departments of 1Medicine, Division of Endocrinology, Diabetes and Metabolism, and
| | - Patrick Tso
- 2Pathology, University of Cincinnati, Cincinnati, Ohio;
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203
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Reconstruction-dependent recovery from anorexia and time-related recovery of regulatory ghrelin system in gastrectomized rats. INTERNATIONAL JOURNAL OF PEPTIDES 2010; 2010. [PMID: 20721337 PMCID: PMC2915663 DOI: 10.1155/2010/365416] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Accepted: 11/12/2009] [Indexed: 12/30/2022]
Abstract
Gastrectomy reduces food intake and body weight (BW) hampering recovery of physical conditions. It also reduces plasma levels of stomach-derived orexigenic ghrelin. This study explored changes in orexigenic ghrelin system in rats receiving total gastrectomy with Billroth II (B-II) or Roux-en-Y (R-Y) method. Feeding and BW were reduced by gastrectomy and subsequently recovered to a greater extent with R-Y than B-II while plasma ghrelin decreased similarly. At postoperative 12th week, ghrelin contents increased in the duodenum and pancreas, plasma ghrelin levels increased upon fasting, and ghrelin injection promoted feeding but not in earlier periods. In summary, gastrectomized rats partially recover feeding and BW, in a reconstruction-dependent manner. At 12th week, ghrelin is upregulated in extra-stomach tissues, plasma ghrelin levels are physiologically regulated, and orexigenic effect of exogenous ghrelin is restored. This time-related recovery of ghrelin system may provide a strategy for promoting feeding, BW, and thereby physical conditions in gastrectomized patients.
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204
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Effect of ghrelin on glucose-insulin homeostasis: therapeutic implications. INTERNATIONAL JOURNAL OF PEPTIDES 2010; 2010. [PMID: 20700401 PMCID: PMC2911604 DOI: 10.1155/2010/234709] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 11/23/2009] [Indexed: 12/17/2022]
Abstract
Ghrelin is a 28-amino-acid peptide that displays a strong growth hormone- (GH-) releasing activity through the activation of the growth hormone secretagogue receptor (GHSR). The first studies about role of ghrelin were focused on its orexigenic ability, but despite indisputable pharmacological data, the evidence for a physiological role for ghrelin in the control of appetite is much less clear. Mice with targeted deletion of either ghrelin or the GHSR exhibit an essentially normal metabolic phenotype when fed a regular chow diet, suggesting that ghrelin may have a redundant role in the regulation of food intake. RNAs for ghrelin as well as GHSR are expressed in the pancreas of rats and humans and several studies propose that ghrelin could have an important function in glucose homeostasis and insulin release, independent of GH secretion. Low plasma ghrelin levels are associated with elevated fasting insulin levels and insulin resistance, suggesting both physiological and pathophysiological roles for ghrelin. For this reason, at least theoretically, ghrelin and/or its signalling manipulation could be useful for the treatment or prevention of diseases of glucose homeostasis such as type 2 diabetes.
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205
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Carneiro BTS, Araujo JF. The food-entrainable oscillator: a network of interconnected brain structures entrained by humoral signals? Chronobiol Int 2010; 26:1273-89. [PMID: 19916831 DOI: 10.3109/07420520903404480] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Food is critical for all animal species. Its temporal availability is a relevant signal for organizing behavioral and physiological parameters. When food is restricted to a few hours per day, rats, mice, and other mammals exhibit anticipatory activity before mealtime (food-anticipatory activity). There is considerable evidence suggesting that this anticipation is mediated by a food-entrainable oscillator (FEO) with circadian properties, but located outside the suprachiasmatic nucleus of the hypothalamus (the light-entrainable oscillator). However, the locus of the FEO as well as the mechanisms by which food entrainment occurs is unclear. In this review, we summarize data about the potential input pathways to the FEO and propose a model for understanding it as a network of interconnected brain structures entrained by fluctuation of different humoral signals.
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206
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Arai Y, Gradwohl G, Kameda Y. Expression of neuropeptide Y and agouti-related peptide in the hypothalamic arcuate nucleus of newborn neurogenin3 null mutant mice. Cell Tissue Res 2010; 340:137-45. [PMID: 20127365 DOI: 10.1007/s00441-009-0925-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Accepted: 12/18/2009] [Indexed: 02/01/2023]
Abstract
Mice deficient in neurogenin 3 (Ngn3) fail to generate pancreatic endocrine cells and intestinal endocrine cells. Hypothalamic neuropeptides implicated in the control of energy homeostasis might also be affected in Ngn3 homozygous null mutant mice. We investigated the expression of two prominent orexigenic neuropeptides, neuropeptide Y (NPY) and agouti-related protein (AgRP), in the hypothalamic arcuate nucleus of newborn wild-type and Ngn3 null mutant mice. Immunohistochemical analysis demonstrated that, in Ngn3 null mutants, the number of NPY-immunoreactive neurons and nerve fibers was markedly increased in the arcuate nucleus, and the nerve fibers were widely distributed in the hypothalamic area, including the paraventricular and dorsomedial nuclei. Little increase of AgRP immunoreactivity was detected in the arcuate nucleus of mutant mice. In situ hybridization analysis confirmed the increased population of the NPY neurons in the arcuate nucleus of the mutants. The NPY mRNA level, as estimated by laser capture microdissection and real-time quantitative polymerase chain reaction, was 371% higher in Ngn3 null mutants than in wild-type mice. AgRP mRNA levels did not differ significantly between the null mutants and wild-type mice. Thus, up-regulation of the hypothalamic NPY system is probably a feature characteristic of Ngn3 null mice.
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Affiliation(s)
- Yuta Arai
- Department of Anatomy, Kitasato University School of Medicine, Kanagawa, 228-8555, Japan
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207
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Stengel A, Goebel M, Wang L, Taché Y. Ghrelin, des-acyl ghrelin and nesfatin-1 in gastric X/A-like cells: role as regulators of food intake and body weight. Peptides 2010; 31:357-69. [PMID: 19944123 PMCID: PMC3166546 DOI: 10.1016/j.peptides.2009.11.019] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 11/12/2009] [Accepted: 11/16/2009] [Indexed: 02/07/2023]
Abstract
Numerous peptides released from endocrine cells in the intestinal mucosa were established early on to be involved in the physiological regulation of food intake with a prominent role in termination of food ingestion when nutrients pass along the intestinal tract. Recently, peptides released from X/A-like endocrine cells of the gastric oxyntic mucosa were recognized as additional key players in the regulation of feeding and energy expenditure. Gastric X/A-like cells release the octanoylated peptide, ghrelin, the only known peripherally produced hormone stimulating food intake through interaction with growth hormone secretagogue 1a receptor (GHS-R1a). Additionally, non-octanoylated (des-acyl) ghrelin present in the circulation at higher levels than ghrelin is currently discussed as potential modulator of food intake by opposing ghrelin's action independent from GHS-R1a although the functional significance remains to be established. Obestatin, a ghrelin-associated peptide was initially reported as anorexigenic modulator of ghrelin's orexigenic action. However, subsequent reports did not support this contention. Interesting is the recent identification of nesfatin-1, a peptide derived from the nucleobindin2 gene prominently expressed in gastric X/A-like cells in different vesicles than ghrelin. Circulating nesfatin-1 levels vary with metabolic state and peripheral or central injection inhibits dark phase feeding in rodents. Overall, these data point to an important role of gastric X/A-like cells in food intake regulation through the expression of the orexigenic peptide ghrelin along with des-acyl ghrelin and nesfatin-1 capable of reducing food intake upon exogenous injection although their mechanisms of action and functional significance remain to be established.
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Affiliation(s)
- Andreas Stengel
- CURE: Digestive Diseases Research Center and Neurobiology of Stress, Digestive Diseases Division, David Geffen School of Medicine at University of California Los Angeles and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA.
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208
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Inhoff T, Stengel A, Peter L, Goebel M, Taché Y, Bannert N, Wiedenmann B, Klapp BF, Mönnikes H, Kobelt P. Novel insight in distribution of nesfatin-1 and phospho-mTOR in the arcuate nucleus of the hypothalamus of rats. Peptides 2010; 31:257-62. [PMID: 19961888 PMCID: PMC4043136 DOI: 10.1016/j.peptides.2009.11.024] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Revised: 11/24/2009] [Accepted: 11/24/2009] [Indexed: 11/24/2022]
Abstract
Recently, two proteins have been localized in the arcuate nucleus (ARC) and implicated in the regulation of food intake: the serine-threonine-kinase mammalian target of rapamycin (mTOR) as part of the TOR signaling complex 1 (TORC1), and nesfatin-1 derived from the precursor protein nucleobindin2. However, the exact cell types are not well described. Therefore, we performed double-labeling studies for NPY, CART, nesfatin-1 and pmTOR in the ARC. In this study, we showed that nesfatin-1 is not only intracellularly co-localized with cocaine- and amphetamine-regulated transcript (CART) peptide as reported before, but also with phospho-mTOR (pmTOR) and neuropeptide Y (NPY) in ARC neurons. Quantification revealed that 59+/-5% of the pmTOR-immunoreactive (ir) neurons were immunoreactive for nesfatin-1. Moreover, double labeling for nesfatin-1 and NPY exhibited that 19+/-5% of the NPY positive cells were also immunoreactive for nesfatin-1. Furthermore, we could also confirm results from previous studies, showing that the majority of nesfatin-1 neurons are also positive for CART peptide, whereas most of the pmTOR is co-localized with NPY and only to a lesser extent with CART.
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Affiliation(s)
- Tobias Inhoff
- Department of Medicine, Division Hepatology, Gastroenterology, and Endocrinology, Charité, Campus Virchow, Universitätsmedizin Berlin, Germany
| | - Andreas Stengel
- Department of Medicine, Division of Digestive Diseases, CURE Digestive Diseases Research Center and Center for Neurobiology of Stress, UCLA and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA
| | - Lisa Peter
- Department of Medicine, Division Hepatology, Gastroenterology, and Endocrinology, Charité, Campus Virchow, Universitätsmedizin Berlin, Germany
| | - Miriam Goebel
- Department of Medicine, Division of Digestive Diseases, CURE Digestive Diseases Research Center and Center for Neurobiology of Stress, UCLA and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA
| | - Yvette Taché
- Department of Medicine, Division of Digestive Diseases, CURE Digestive Diseases Research Center and Center for Neurobiology of Stress, UCLA and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA
| | | | - Bertram Wiedenmann
- Department of Medicine, Division Hepatology, Gastroenterology, and Endocrinology, Charité, Campus Virchow, Universitätsmedizin Berlin, Germany
| | - Burghard F. Klapp
- Department of Medicine, Division Psychosomatic Medicine and Psychotherapy, Charité, Campus Mitte, Universitätsmedizin Berlin, Luisenstraße 13 A, 10117 Berlin, Germany
| | - Hubert Mönnikes
- Department of Medicine and Institute of Neurogastroenterology, Martin-Luther-Hospital, Berlin, Germany
| | - Peter Kobelt
- Department of Medicine, Division Hepatology, Gastroenterology, and Endocrinology, Charité, Campus Virchow, Universitätsmedizin Berlin, Germany
- Department of Medicine, Division Psychosomatic Medicine and Psychotherapy, Charité, Campus Mitte, Universitätsmedizin Berlin, Luisenstraße 13 A, 10117 Berlin, Germany
- Corresponding author. Tel.: +49 30 450 559739
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209
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Crespo MA, González Matías LC, Lozano MG, Paz SF, Pérez MR, Gago EV, Ferrer FM. [Gastrointestinal hormones in food intake control]. ACTA ACUST UNITED AC 2010; 56:317-30. [PMID: 19695513 DOI: 10.1016/s1575-0922(09)71946-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Accepted: 05/25/2009] [Indexed: 12/17/2022]
Abstract
The discovery of gut hormones regulating the energy balance has aroused great interest in the scientific community. Some of these hormones modulate appetite and satiety, acting on the hypothalamus or the solitary tract nucleus in the brainstem. In general, the endocrine signals generated in the gut have direct or indirect (through the autonomous nervous system) anorexigenic effects. Only ghrelin, a gastric hormone, has been consistently associated with the initiation of food intake and is regarded as the main orexigenic signal both in animal models and humans. In this review, we provide a brief description of the major gastrointestinal hormones implicated in the regulation of food intake. Given the increased importance of food intake disturbances, especially obesity, a better understanding of the underlying mechanisms of action of the gastrointestinal hormones might contribute to the development of new molecules that could increase the therapeutic arsenal for treating obesity and its associated comorbidities.
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Affiliation(s)
- Mayte Alvarez Crespo
- Laboratorio de Endocrinología, Departamento de Biología Funcional y Ciencias de la Salud, Facultad de Biología, Universidad de Vigo, Vigo, Pontevedra, España
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210
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Interactions of gastrointestinal peptides: ghrelin and its anorexigenic antagonists. INTERNATIONAL JOURNAL OF PEPTIDES 2010; 2010. [PMID: 20798884 PMCID: PMC2925274 DOI: 10.1155/2010/817457] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 10/13/2009] [Accepted: 10/19/2009] [Indexed: 12/21/2022]
Abstract
Food intake behaviour and energy homeostasis are strongly regulated by a complex system of humoral factors and nerval structures constituting the brain-gut-axis. To date the only known peripherally produced and centrally acting peptide that stimulates food intake is ghrelin, which is mainly synthesized in the stomach. Recent data indicate that the orexigenic effect of ghrelin might be influenced by other gastrointestinal peptides such as cholecystokinin (CCK), bombesin, desacyl ghrelin, peptide YY (PYY), as well as glucagon-like peptide (GLP). Therefore, we will review on the interactions of ghrelin with several gastrointestinal factors known to be involved in appetite regulation in order to elucidate the interdependency of peripheral orexigenic and anorexigenic peptides in the control of appetite.
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211
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Castañeda TR, Tong J, Datta R, Culler M, Tschöp MH. Ghrelin in the regulation of body weight and metabolism. Front Neuroendocrinol 2010; 31:44-60. [PMID: 19896496 DOI: 10.1016/j.yfrne.2009.10.008] [Citation(s) in RCA: 241] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Revised: 10/26/2009] [Accepted: 10/26/2009] [Indexed: 12/25/2022]
Abstract
Ghrelin, a peptide hormone predominantly produced by the stomach, was isolated as the endogenous ligand for the growth hormone secretagogue receptor. Ghrelin is a potent stimulator of growth hormone (GH) secretion and is the only circulatory hormone known to potently enhance feeding and weight gain and to regulate energy homeostasis following central and systemic administration. Therapeutic intervention with ghrelin in catabolic situations may induce a combination of enhanced food intake, increased gastric emptying and nutrient storage, coupled with an increase in GH thereby linking nutrient partitioning with growth and repair processes. These qualities have fostered the idea that ghrelin-based compounds may have therapeutic utility in treating malnutrition and wasting induced by various sub-acute and chronic disorders. Conversely, compounds that inhibit ghrelin action may be useful for the prevention or treatment of metabolic syndrome components such as obesity, impaired lipid metabolism or insulin resistance. In recent years, the effects of ghrelin on glucose homeostasis, memory function and gastrointestinal motility have attracted considerable amount of attention and revealed novel therapeutic targets in treating a wide range of pathologic conditions. Furthermore, discovery of ghrelin O-acyltransferase has also opened new research opportunities that could lead to major understanding of ghrelin physiology. This review summarizes the current knowledge on ghrelin synthesis, secretion, mechanism of action and biological functions with an additional focus on potential for ghrelin-based pharmacotherapies.
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Affiliation(s)
- T R Castañeda
- Dept. of Physiology and Pharmacology, Center for Diabetes and Endocrine Research, College of Medicine, University of Toledo, Toledo, OH, USA
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212
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Das UN. Obesity: genes, brain, gut, and environment. Nutrition 2009; 26:459-73. [PMID: 20022465 DOI: 10.1016/j.nut.2009.09.020] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 09/21/2009] [Accepted: 09/27/2009] [Indexed: 01/04/2023]
Abstract
Obesity, which is assuming alarming proportions, has been attributed to genetic factors, hypothalamic dysfunction, and intestinal gut bacteria and an increase in the consumption of energy-dense food. Obesity predisposes to the development of type 2 diabetes mellitus, hypertension, coronary heart disease, and certain forms of cancer. Recent studies have shown that the intestinal bacteria in obese humans and mice differ from those in lean that could trigger a low-grade systemic inflammation. Consumption of a calorie-dense diet that initiates and perpetuates obesity could be due to failure of homeostatic mechanisms that regulate appetite, food consumption, and energy balance. Hypothalamic factors that regulate energy needs of the body, control appetite and satiety, and gut bacteria that participate in food digestion play a critical role in the onset of obesity. Incretins, cholecystokinin, brain-derived neurotrophic factor, leptin, long-chain fatty acid coenzyme A, endocannabinoids and vagal neurotransmitter acetylcholine play a role in the regulation of energy intake, glucose homeostasis, insulin secretion, and pathobiology of obesity and type 2 diabetes mellitus. Thus, there is a cross-talk among the gut, liver, pancreas, adipose tissue, and hypothalamus. Based on these evidences, it is clear that management of obesity needs a multifactorial approach.
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213
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Goto S, Nagao K, Bannai M, Takahashi M, Nakahara K, Kangawa K, Murakami N. Anorexia in rats caused by a valine-deficient diet is not ameliorated by systemic ghrelin treatment. Neuroscience 2009; 166:333-40. [PMID: 20006681 DOI: 10.1016/j.neuroscience.2009.12.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 11/26/2009] [Accepted: 12/04/2009] [Indexed: 11/28/2022]
Abstract
Rodents exhibit aversive behavior toward a diet that lacks at least one of the essential amino acids. We sought to determine whether the particular form of anorexia caused by such diets could be ameliorated by the administration of orexigenic peptides while simultaneously analyzing the neural mechanisms underlying anorexia. Rats were fed a valine-deficient diet, which induced severe anorexia (reducing food consumption by 80%). The severe anorexia was associated with a significant decrease in the cerebrospinal fluid valine concentration and hyper-ghrelinemia. Between 6 and 12 days after initiation of the valine-deficient diet, we injected rats twice daily with valine and/or an orexigenic peptide (ghrelin, neuropeptide Y, or agouti-related protein) either i.p. or i.c.v.. We then measured dietary intake. An i.c.v. valine injection allowed earlier food intake compared with an i.p valine injection and increased the density of c-Fos-positive ependymal cells lining the third ventricle. Whereas an i.c.v. injection of ghrelin or neuropeptide Y increased consumption of the valine-deficient diet, i.p injection of ghrelin or i.c.v. injection of agouti-related protein did not. Following i.c.v. administration of either valine or ghrelin, we did not observe complete recovery of consumption of the valine-deficient diet. This may be due to the ineffectiveness of peripheral ghrelin and central agouti-related protein and/or to conditioned aversion to the valine-deficient diet. Since ghrelin is known to be involved in food anticipatory activities, whether the hyper-ghrelinemia observed in valine-deficient rats play role in foraging behavior other than food intake is the future study to be investigated.
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Affiliation(s)
- S Goto
- Department of Veterinary Physiology, Miyazaki University, Miyazaki, Miyazaki 889-2192, Japan
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214
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Perboni S, Inui A. Appetite and gastrointestinal motility: role of ghrelin-family peptides. Clin Nutr 2009; 29:227-34. [PMID: 19945199 DOI: 10.1016/j.clnu.2008.10.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Revised: 09/28/2008] [Accepted: 10/30/2008] [Indexed: 12/26/2022]
Abstract
Eating disorders, obesity and cachexia endanger the lives of millions of people worldwide. Fortunately, in last decade, there has been a rapid and substantial progress toward uncovering the molecular and neural mechanisms by which energy imbalance develops. In 1999, ghrelin was identified as the first orexigenic gut-derived peptide. It stimulates appetite and controls the gastric motility and the acid secretion through the activation of the growth hormone secretagogue-receptor. After the discovery of ghrelin, other forms of ghrelin-related proteins were isolated from the rat stomach. The unmodified des-n-octanoyl form (des-acyl ghrelin) and the recent obestatin act through distinct receptors and contrarily to acyl ghrelin, show an anorexigenic activity. The finding that these three peptide hormones derive from the same precursor exert opposing physiological actions, highlights the importance of post-translational regulatory mechanisms. Further investigations are required to highlight the complexity of ghrelin physiology in order to better understand the mechanisms regulating the energy balance and provide a successful treatment of eating disorders, obesity and cachexia.
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Affiliation(s)
- Simona Perboni
- Unità Operativa Day-Hospital Area Medica, Ospedale di Manerbio, Azienda Ospedaliera di Desenzano del Garda, Brescia I-25025, Italy.
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215
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Role of brain nitric oxide in the thermoregulation of broiler chicks. Comp Biochem Physiol A Mol Integr Physiol 2009; 154:204-10. [DOI: 10.1016/j.cbpa.2009.06.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2008] [Revised: 06/06/2009] [Accepted: 06/07/2009] [Indexed: 12/11/2022]
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Sheriff S, Joshi R, Friend LA, James JH, Balasubramaniam A. Ghrelin receptor agonist, GHRP-2, attenuates burn injury-induced MuRF-1 and MAFbx expression and muscle proteolysis in rats. Peptides 2009; 30:1909-13. [PMID: 19577604 DOI: 10.1016/j.peptides.2009.06.029] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 06/24/2009] [Accepted: 06/24/2009] [Indexed: 10/20/2022]
Abstract
Thermal injury results in hypermetabolism, loss of body weight, and skeletal muscle wasting in mice and rats. Our earlier studies have demonstrated that ghrelin injection stimulates food intake and growth hormone release and inhibits skeletal muscle proteolysis in rats with thermal injury. We sought to develop a lower molecular weight, stable and longer acting peptide to combat the catabolic responses caused by thermal injury. Towards this goal, we examined the role of the hexapeptide mimetic of ghrelin, growth hormone-releasing peptide-2 (GHRP-2), on expression of E3 ubiquitin ligases and breakdown of muscle protein in rats with thermal injury. Slow in vivo release of GHRP-2 through minipump for 24h attenuated the thermal injury-induced increase in mRNA expression of IL-6 and of the E3 ubiquitin ligases, MuRF-1 and MAFbx, in rat skeletal muscle. Furthermore, burn-induced increases in total and myofibrillar protein breakdown from rat EDL muscle were attenuated by GHRP-2. These findings suggest that catabolic responses resulting from thermal injury can be attenuated by GHRP-2.
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Affiliation(s)
- Sulaiman Sheriff
- Department of Surgery, University of Cincinnati College of Medicine, and Shriners Hospital for Children, 231 Albert Sabin Way, Cincinnati, OH 45267-0558, USA
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217
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Abstract
PURPOSE OF REVIEW To evaluate the influence of Helicobacter pylori infection on the gastric regulation of food intake and body weight. RECENT FINDINGS H. pylori infection leads to a decrease of circulating ghrelin through a reduction of ghrelin-producing cells in the gastric mucosa and increases the amount of gastric leptin with no effect on circulating leptin levels. Eradication of H. pylori reverses the abnormal regulation of gastric hormone secretion. This finding is suggested to favor weight gain after H. pylori eradication and points to the potential effect of H. pylori in the pathophysiology of obesity. SUMMARY H. pylori has an influence on the release of gastric hormones and therefore plays a role in the regulation of body weight, hunger and satiety.
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Affiliation(s)
- Jochen Weigt
- Department of Gastroenterology, Hepatology and Infectious Diseases, Otto-v.-Guericke University Magdeburg, Magdeburg, Germany
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218
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Salomé N, Hansson C, Taube M, Gustafsson-Ericson L, Egecioglu E, Karlsson-Lindahl L, Fehrentz JA, Martinez J, Perrissoud D, Dickson SL. On the central mechanism underlying ghrelin's chronic pro-obesity effects in rats: new insights from studies exploiting a potent ghrelin receptor antagonist. J Neuroendocrinol 2009; 21:777-85. [PMID: 19703102 DOI: 10.1111/j.1365-2826.2009.01895.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In the present study, we explore the central nervous system mechanism underlying the chronic central effects of ghrelin with respect to increasing body weight and body fat. Specifically, using a recently developed ghrelin receptor antagonist, GHS-R1A (JMV2959), we investigate the role of GHS-R1A in mediating the effects of ghrelin on energy balance and on hypothalamic gene expression. As expected, in adult male rats, chronic central treatment with ghrelin for 14 days, when compared to vehicle-treated control rats, resulted in an increased body weight, lean mass and fat mass (assessed by dual X-ray absorptiometry), dissected white fat pad weight, cumulative food intake, food efficiency, respiratory exchange ratio and a decrease of energy expenditure. Co-administration of the ghrelin receptor antagonist JMV2959 suppressed/blocked the majority of these effects, with the notable exception of ghrelin-induced food intake and food efficiency. The hypothesis emerging from these data, namely that GHS-R1A mediates the chronic effects of ghrelin on fat accumulation, at least partly independent of food intake, is discussed in light of the accompanying data regarding the hypothalamic genes coding for peptides and receptors involved in energy balance regulation, which were found to have altered expression in these studies.
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Affiliation(s)
- N Salomé
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Sweden.
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219
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Aslan A, Yildirim M, Ayyildiz M, Güven A, Agar E. The role of nitric oxide in the inhibitory effect of ghrelin against penicillin-induced epileptiform activity in rat. Neuropeptides 2009; 43:295-302. [PMID: 19552953 DOI: 10.1016/j.npep.2009.05.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Revised: 04/10/2009] [Accepted: 05/23/2009] [Indexed: 11/25/2022]
Abstract
Ghrelin, a gastric peptide with key action on food intake, has been recently recognized as a potential antiepileptic agent. In the present study, we investigated the involvement of nitric oxide in the effect of ghrelin on penicillin-induced epileptiform activity in rat. Thirty minutes after penicillin injection, ghrelin, at doses of 0.5, 1, 2 microg, was administered intracerebroventricularly (i.c.v.). Ghrelin, at a dose of 1 microg, significantly decreased the mean frequency of epileptiform activity without changing the amplitude whereas other doses of ghrelin (0.5 and 2 microg) did not alter either the mean of frequency or amplitude of epileptiform activity. The effects of systemic administration of nitric oxide synthase (NOS) inhibitors, non-selective N(G)-nitro-l-arginine methyl ester (l-NAME), selective neuronal NOS inhibitor, 7-nitroindazole (7-NI) and NO substrate, l-arginine on the anticonvulsive effects of ghrelin were investigated. The administration of l-NAME (60 mg/kg, i.p.), 15 min before ghrelin (1microg) application, reversed the anti-epileptiform effects of ghrelin whereas 7-NI (40 mg/kg, i.p.) did not influence it. The present study provides electrophysiological evidence that the intracerebroventricular injection of ghrelin has an inhibitory effect against epileptiform activity in the penicillin model of epilepsy. The anti-epileptiform activity of ghrelin was reversed by nonspecific nitric oxide synthase inhibitor l-NAME, but not selective neuronal nitric oxide synthase inhibitor 7-NI, indicating that ghrelin requires activation of endothelial-NOS/NO route in the brain.
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Affiliation(s)
- Ali Aslan
- Department of Physiology, Faculty of Medicine, University of Ondokuz Mayis, 55139 Samsun, Turkey
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220
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Depoortere I. Targeting the ghrelin receptor to regulate food intake. ACTA ACUST UNITED AC 2009; 156:13-23. [PMID: 19362579 DOI: 10.1016/j.regpep.2009.04.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 04/05/2009] [Indexed: 01/28/2023]
Affiliation(s)
- Inge Depoortere
- Centre for Gastroenterological Research, Gasthuisberg, O&N, box 701, B-3000 Leuven, Belgium.
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221
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Perić - Mataruga V, Mirčić D, Vlahović M, Mrdaković M, Todorović D, Stevanović D, Milošević V. Effects of ghrelin on the feeding behavior of Lymantria dispar L. (Lymantriidae) caterpillars. Appetite 2009; 53:147-50. [DOI: 10.1016/j.appet.2009.05.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2009] [Accepted: 05/12/2009] [Indexed: 10/20/2022]
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222
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Kirchner H, Gutierrez JA, Solenberg PJ, Pfluger PT, Czyzyk TA, Willency JA, Schürmann A, Joost HG, Jandacek RJ, Hale JE, Heiman ML, Tschöp MH. GOAT links dietary lipids with the endocrine control of energy balance. Nat Med 2009; 15:741-5. [PMID: 19503064 PMCID: PMC2789701 DOI: 10.1038/nm.1997] [Citation(s) in RCA: 300] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Accepted: 05/29/2009] [Indexed: 12/16/2022]
Abstract
CNS nutrient sensing and afferent endocrine signalling are established as parallel systems communicating metabolic status and energy availability in vertebrates. The only afferent endocrine signal known to require modification with a fatty acid side chain is the orexigenic hormone ghrelin. We find that the ghrelin O-acyl transferase (GOAT) which is essential for ghrelin acylation, is regulated by nutrient availability, depends on specific dietary lipids as acylation substrates and modulates body fat mass in mice.
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Affiliation(s)
- Henriette Kirchner
- Departments of Psychiatry and Medicine, Obesity Research Centre & Genome Research Institute, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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223
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Abstract
Ghrelin, an endogenous ligand of the GH (growth hormone) secretagogue receptor, influences many metabolic processes including GH secretion, food intake, energy balance, insulin secretion and adipogenesis. Although ghrelin exhibits a variety of biological functions, the mechanism by which ghrelin expression is regulated is unknown. Ghrelin is expressed in the gastrointestinal tract, predominantly in the stomach, as is KLF4 (Krüppel-like factor 4). Therefore we investigated whether ghrelin expression is associated with KLF4, and found that the tissue distribution of ghrelin corresponded with that of KLF4. Furthermore, treatment with butyrate, an inducer of KLF4 expression, stimulated ghrelin expression, and fasting, which induces ghrelin expression, also increased KLF4 expression, suggesting that ghrelin expression is associated with KLF4. Then, we investigated the effects of KLF4 on the human ghrelin-promoter activity and identified a KLF4-responsive region in the promoter. KLF4 expression specifically stimulated human ghrelin-promoter activity in a dose-dependent manner in human gastric-cancer AGS cells. However, this effect was not seen in response to a mutant KLF4 construct. Transfection studies using mutant constructs containing 5'-deletions in the human ghrelin promoter revealed that the KLF4-responsive element is located between -1228 and -1105. Electrophoretic mobility shift assays using oligonucleotides containing -1165/-1146 revealed the binding of KLF4 to the human ghrelin promoter. Finally, deletion of the -1165/-1146 region abrogated KLF4-induced transactivation of the ghrelin promoter. Collectively, these results indicate that KLF4 positively regulates human ghrelin expression via binding to a KLF-responsive region in the promoter.
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224
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Abstract
AMP-dependent protein kinase (AMPK) is an evolutionarily conserved serine/threonine protein kinase central to the regulation of energy balance at both the cellular and whole-body levels. In its classical role as an intracellular metabolic stress-sensing kinase, AMPK switches on fatty acid oxidation and glucose uptake in muscle, while switching off hepatic gluconeogenesis. AMPK also has a broader role in metabolism through the control of appetite. Regulation of AMPK activity at the whole-body level is coordinated by a growing number of hormones and cytokines secreted from adipose tissue, skeletal muscle, pancreas and the gut including leptin, adiponectin, insulin, interluekin-6, resistin, TNF-alpha and ghrelin. Understanding how these secreted signalling proteins regulate AMPK activity to control fatty acid oxidation, glucose uptake, gluconeogenesis and appetite may yield therapeutic treatments for metabolic disorders such as diabetes, insulin resistance and obesity.
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Affiliation(s)
- N L Dzamko
- Protein Chemistry & Metabolism, St Vincent's Institute of Medical Research and The University of Melbourne, 9 Princes Street, Fitzroy, Victoria 3065, Australia
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225
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Sustained appetite improvement in malnourished dialysis patients by daily ghrelin treatment. Kidney Int 2009; 76:199-206. [PMID: 19387475 DOI: 10.1038/ki.2009.114] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Malnutrition is a common complication in patients on dialysis and is strongly associated with poor prognosis. Effective therapy could substantially improve morbidity and mortality, but neither enteral nor parenteral supplementation provide long-term benefit because of the strong appetite suppression seen in such patients. We performed a double-blinded randomized crossover study of a week-long treatment with daily subcutaneous ghrelin, a gut hormone that regulates hunger through the hypothalamus, in a group of 12 malnourished dialysis patients. Ghrelin administration increased ghrelin levels in circulation, modestly reduced blood pressure for up to 2 h, and immediately and significantly increased appetite, with an increase in energy intake noted at the first study meal. Persistence of this effect throughout the week was confirmed with food diaries and final study meals. Energy expenditure, measured with free-living pulse and motion monitors, was unchanged by ghrelin. Our study shows that daily treatment with ghrelin achieves a sustained positive change in energy balance in malnourished dialysis patients. Direct manipulation of appetite with ghrelin or its analogs represents an attractive and promising therapeutic strategy for this difficult clinical problem.
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226
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Abstract
Background: Ghrelin is a peptide produced predominantly in the stomach and intestines, and is a natural growth hormone (GH) secretagogue-receptor ligand. It is able to stimulate GH release, but it also exhibits an important role in conditions related to processes regulating nutrition, body composition and growth, and heart, liver, thyroid or kidney dysfunction. Drug discovery efforts initially focused on ghrelin-receptor agonists, known as GH secretagogues, to be used as anabolic agents, but none of them reached the market. Discussion: The latest developments in this field are constituted by the discovery of new nonpeptidic compounds endowed with interesting properties: oxindole agonists are able to exert an increase in the fat-free mass, while ghrelin was reported to increase the fat mass gain, and triazole- and 2,4-diaminopyrimidine-based antagonists were shown to be able to reduce food intake, without inhibition of GH secretion stimulated by an agonist to the ghrelin receptor. Other antagonist compounds (quinazolinones) were discovered as antiobesity/antidiabetic agents. Moreover, inverse agonists have been discovered that are able to reduce weight gain. Conclusions: Taking into account the great number of pathological conditions related to ghrelin, and the discovery of several compounds able to modulate the ghrelin receptor, its importance in the field of medicinal chemistry research is set to increase significantly.
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227
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Balasubramaniam A, Joshi R, Su C, Friend LA, Sheriff S, Kagan RJ, James JH. Ghrelin inhibits skeletal muscle protein breakdown in rats with thermal injury through normalizing elevated expression of E3 ubiquitin ligases MuRF1 and MAFbx. Am J Physiol Regul Integr Comp Physiol 2009; 296:R893-901. [PMID: 19211729 DOI: 10.1152/ajpregu.00015.2008] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We previously determined that ghrelin synthesis was downregulated after burn injury and that exogenous ghrelin retained its ability both to stimulate food intake and to restore plasma growth hormone levels in burned rats. These observations and the finding that anabolic hormones can attenuate skeletal muscle catabolism led us to investigate whether ghrelin could attenuate burn-induced skeletal muscle protein breakdown in rats. These studies were performed in young rats (50-60 g) 24 h after approximately 30% total body surface area burn injury. Burn injury increased total and myofibrillar protein breakdown in extensor digitorum longus (EDL) muscles assessed by in vitro tyrosine and 3-methyl-histidine release, respectively. Continuous 24-h administration of ghrelin (0.2 mg.kg(-1).h(-1)) significantly inhibited both total and myofibrillar protein breakdown in burned rats. Ghrelin significantly attenuated burn-induced changes in mRNA expression of IGFBP-1 and IGFBP-3 in liver. In EDL, ghrelin attenuated the increases in mRNA expression of the binding proteins, but had no significant effect on reduced expression of IGF-I. Ghrelin markedly reduced the elevated mRNA expression of TNF-alpha and IL-6 in EDL muscle that occurred after burn. Moreover, ghrelin normalized plasma glucocorticoid levels, which were elevated after burn. Expression of the muscle-specific ubiquitin-ligating enzyme (E3) ubiquitin ligases MuRF1 and MAFbx were markedly elevated in both EDL and gastrocnemius and were normalized by ghrelin. These results suggest that ghrelin is a powerful anticatabolic compound that reduces skeletal muscle protein breakdown through attenuating multiple burn-induced abnormalities.
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Affiliation(s)
- Ambikaipakan Balasubramaniam
- Department of Surgery, University of Cincinnati College of Medicine, 231 Albert Sabin Way, Cincinnati, OH 45267-0558.
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228
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Minor RK, Chang JW, de Cabo R. Hungry for life: How the arcuate nucleus and neuropeptide Y may play a critical role in mediating the benefits of calorie restriction. Mol Cell Endocrinol 2009; 299:79-88. [PMID: 19041366 PMCID: PMC2668104 DOI: 10.1016/j.mce.2008.10.044] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Accepted: 10/14/2008] [Indexed: 11/27/2022]
Abstract
Laboratory studies consistently demonstrate extended lifespan in animals on calorie restriction (CR), where total caloric intake is reduced by 10-40% but adequate nutrition is otherwise maintained. CR has been further shown to delay the onset and severity of chronic diseases associated with aging such as cancer, and to extend the functional health span of important faculties like cognition. Less understood are the underlying mechanisms through which CR might act to induce such alterations. One theory postulates that CR's beneficial effects are intimately tied to the neuroendocrine response to low energy availability, of which the arcuate nucleus in the hypothalamus plays a pivotal role. Neuropeptide Y (NPY), a neurotransmitter in the front line of the arcuate response to low energy availability, is the primary hunger signal affected by CR and therefore may be a critical mechanism for lifespan extension.
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Affiliation(s)
- Robin K. Minor
- Laboratory of Experimental Gerontology, Intramural Research Program, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
| | - Joy W. Chang
- Laboratory of Experimental Gerontology, Intramural Research Program, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
| | - Rafael de Cabo
- Laboratory of Experimental Gerontology, Intramural Research Program, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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229
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Sneddon AA, Rayner DV, Mitchell SE, Bashir S, Ha JH, Wahle KW, Morris AC, Williams LM. Dietary supplementation with conjugated linoleic acid plus n-3 polyunsaturated fatty acid increases food intake and brown adipose tissue in rats. Nutrients 2009; 1:178-96. [PMID: 22253977 PMCID: PMC3257602 DOI: 10.3390/nu1020178] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Accepted: 11/24/2009] [Indexed: 11/17/2022] Open
Abstract
The effect of supplementation with 1% conjugated linoleic acid and 1% n-3 long chain polyunsaturated fatty acids (CLA/n-3) was assessed in rats. Food intake increased with no difference in body weights. White adipose tissue weights were reduced whereas brown adipose tissue and uncoupling protein-1 expression were increased. Plasma adiponectin, triglyceride and cholesterol levels were reduced while leptin, ghrelin and liver weight and lipid content were unchanged. Hypothalamic gene expression measurements revealed increased expression of orexigenic and decreased expression of anorexigenic signals. Thus, CLA/n-3 increases food intake without affecting body weight potentially through increasing BAT size and up-regulating UCP-1 in rats.
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Affiliation(s)
- Alan A. Sneddon
- Vascular Health Programme, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, AB21 9SB, UK; (A.A.S.); (S.B.)
| | - D. Vernon Rayner
- Obesity and Metabolic Health Programme, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, AB21 9SB, UK; (D.V.R.); (S.E.M.); (J.-H.H.); (A.C.M.)
| | - Sharon E. Mitchell
- Obesity and Metabolic Health Programme, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, AB21 9SB, UK; (D.V.R.); (S.E.M.); (J.-H.H.); (A.C.M.)
| | - Shabina Bashir
- Vascular Health Programme, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, AB21 9SB, UK; (A.A.S.); (S.B.)
| | - Jung-Heun Ha
- Obesity and Metabolic Health Programme, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, AB21 9SB, UK; (D.V.R.); (S.E.M.); (J.-H.H.); (A.C.M.)
| | - Klaus W. Wahle
- School of Medicine and Dentistry, Cancer Medicine Research Programme, University of Aberdeen, Aberdeen, AB25 2ZD, UK;
| | - Amanda C. Morris
- Obesity and Metabolic Health Programme, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, AB21 9SB, UK; (D.V.R.); (S.E.M.); (J.-H.H.); (A.C.M.)
| | - Lynda M. Williams
- Obesity and Metabolic Health Programme, Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen, AB21 9SB, UK; (D.V.R.); (S.E.M.); (J.-H.H.); (A.C.M.)
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230
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Catalytic antibody degradation of ghrelin increases whole-body metabolic rate and reduces refeeding in fasting mice. Proc Natl Acad Sci U S A 2008; 105:17487-92. [PMID: 18981425 DOI: 10.1073/pnas.0711808105] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Obesity is a chronic, costly, and globally prevalent condition, with excess caloric intake a suspected etiologic factor. Nonsurgical treatments are modestly efficacious, and weight loss maintenance is hampered by anti-famine homeostatic mechanisms. Ghrelin, a gastric hormone linked to meal initiation, energy expenditure, and fuel partitioning, is hypothesized to facilitate weight gain and impede weight loss. Unique among known animal peptides, the serine-3 residue of ghrelin is posttranslationally acylated with an n-octanoic acid, a modification important for the peptide's active blood-brain transport and growth hormone secretagogue receptor-1 agonist activity. Pharmacological degradation of ghrelin would be hypothesized to reduce ghrelin's biological effects. To study endogenous ghrelin's role in appetite and energy expenditure, we generated antibodies that hydrolyze the octanoyl moiety of ghrelin to form des-acyl ghrelin. The most proficient antibody catalyst, GHR-11E11, was found to display a second-order rate constant of 18 M(-1) x s(-1) for the hydrolysis of ghrelin to des-acyl ghrelin. I.v. administration of GHR-11E11 (50 mg/kg) maintained a greater metabolic rate in fasting C57BL/6J mice as compared with mice receiving a control antibody and suppressed 6-h refeeding after 24 h of food deprivation. Indirect respiratory measures of metabolism after refeeding and relative fuel substrate utilization were unaffected. The results support the hypothesis that acylated ghrelin stimulates appetite and curbs energy expenditure during deficient energy intake, whereas des-acyl ghrelin does not potently share these functions. Catalytic anti-ghrelin antibodies might thereby adjunctively aid consolidation of caloric restriction-induced weight loss and might also be therapeutically relevant to Prader-Willi syndrome, characterized after infancy by hyperghrelinemia, hyperphagia, and obesity.
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231
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Triiodothyronine (T3) stimulates food intake via enhanced hypothalamic AMP-activated kinase activity. ACTA ACUST UNITED AC 2008; 151:164-9. [DOI: 10.1016/j.regpep.2008.07.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2008] [Revised: 07/22/2008] [Accepted: 07/24/2008] [Indexed: 12/21/2022]
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232
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Kim E, Seo S, Chung H, Park S. Role of Glucocorticoids in Fasting-induced Changes in Hypothalamic and Pituitary Components of the Growth Hormone (GH)-axis. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2008; 12:217-23. [PMID: 19967059 DOI: 10.4196/kjpp.2008.12.5.217] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
To directly test if elevated glucocorticoids are required for fasting-induced regulation of growth hormone (GH)-releasing hormone (GHRH), GHRH receptors (GHRH-R) and ghrelin receptors (GHS-R) expression, male rats were bilaterally adrenalectomized or sham operated. After 7 days, animals were fed ad libitum or fasted for 48 h. Bilateral adrenalectomy increased hypothalamic GHRH to 146% and decreased neuropeptide Y (NPY) mRNA to 54% of SHAM controls. Pituitary GHRH-R and GHS-R mRNA levels were decreased by adrenalectomy to 30% and 80% of sham-operated controls. In shamoperated rats, fasting suppressed hypothalamic GHRH (49%) and stimulated NPY (166%) mRNA levels, while fasting increased pituitary GHRH-R (391%) and GHS-R (218%) mRNA levels. However, in adrenalectomized rats, fasting failed to alter pituitary GHRH-R mRNA levels, while the fasting-induced suppression of GHRH and elevation of NPY and GHS-R mRNA levels remained intact. In fasted adrenalectomized rats, corticosterone replacement increased GHRH-R mRNA levels and intensified the fasting-induced decrease in GHRH, but did not alter NPY or GHS-R response. These data suggest that elevated glucocorticoids mediate the effects of fasting on hypothalamic GHRH and pituitary GHRH-R expression, while glucocorticoids are likely not the major determinant in fasting-induced increases in hypothalamic NPY and pituitary GHS-R expression.
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Affiliation(s)
- Eunhee Kim
- Department of Pharmacology and Medical Research Center for Bioreaction to ROS and Biomedical Science Institute, Kyunghee University School of Medicine, Seoul 130-701, Korea
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233
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Zhang J, Liu S, Tang M, Chen JDZ. Optimal locations and parameters of gastric electrical stimulation in altering ghrelin and oxytocin in the hypothalamus of rats. Neurosci Res 2008; 62:262-9. [PMID: 18940208 DOI: 10.1016/j.neures.2008.09.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 08/26/2008] [Accepted: 09/08/2008] [Indexed: 01/12/2023]
Abstract
UNLABELLED Gastric electric stimulation (GES) has been shown to decrease gastric tone and antrum motility, delay gastric empty, suppress appetite and induce weight loss in animal models. Our previous studies have shown that GES activates gastric-distension responsive neurons in several satiety related hypothalamic nuclei; Two hour acute GES at gastric antrum can alter the expression of anorexigenic and orexigenic peptides in the hypothalamus of rats. AIM To investigate the effects of GES with different stimulation parameters and locations on the neuronal expression of a hunger hormone, ghrelin and a satiety hormone, oxytocin (OT) in the hypothalamus of rats. METHODS With immunohistochemical technique, changes in expression of satiety-related peptides-containing (OT- and ghrelin-) neurons with GES in the rodent hypothalamus were assessed. GES was performed for 2h using six different sets of parameters at three different locations. RESULTS (1) The number of ghrelin/OT-immunoreactive (IR) neurons was significantly decreased/increased with GES of the standard parameters (pulse trains: train on-time of 2s, off-time of 3s, pulse amplitude of 6 mA, width of 0.3 ms and frequency of 40 Hz) in both the paraventricular nucleus (PVN) and the superoptical nucleus (SON) compared with the control group, but not with GES of reduced pulse amplitudes, frequencies or train-on times. (2) GES with the standard parameters at the antrum resulted in a significant decrease/increase in the expression of ghrelin/OT in the PVN and the SON. However, GES at other locations (middle of lesser curvature or greater curvature) was not effective in altering the expression of ghrelin/OT. CONCLUSIONS GES with the standard parameters delivered at the distal antrum increases/decreases oxytocin/ghrelin in the hypothalamus of rats. GES with reduced parameters or delivered at the middle of the stomach is ineffective in altering these peptides.
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Affiliation(s)
- Jing Zhang
- Veterans Research and Education Foundation, VA Medical Center, Oklahoma City, OK, United States
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234
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Abstract
The Agouti-Related Protein (AgRP) is a powerful orexigenic peptide that increases food intake when ubiquitously overexpressed or when administered centrally. AgRP-deficiency, on the other hand, leads to increased metabolic rate and a longer lifespan when mice consume a high fat diet. In humans, AgRP polymorphisms have been consistently associated with resistance to fatness in Blacks and Whites and resistance to the development of type-2 diabetes in African Blacks. Systemically administered AgRP accumulates in the liver, the adrenal gland and fat tissue while recent findings suggest that AgRP may also have inverse agonist effects, both centrally and peripherally. AgRP could thus modulate energy balance via different actions. Its absence or reduced functionality may offer a benefit both in terms of bringing about negative energy balance in obesigenic environments, as well as leading to an increased lifespan.
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Affiliation(s)
- O. Ilnytska
- Pennington Biomedical Research Center, LSU System, Baton Rouge, Louisiana, 70809 USA
| | - G. Argyropoulos
- Pennington Biomedical Research Center, LSU System, Baton Rouge, Louisiana, 70809 USA
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235
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Abstract
The endogenous ligand for growth-hormone secretagogue receptor (GHS-R) was purified from the stomach and we named it "ghrelin", after a word root ("ghre") in Proto-Indo-European languages meaning "grow", since ghrelin has potent growth hormone (GH) releasing activity. In addition, ghrelin stimulates appetite by acting on the hypothalamic arcuate nucleus, a region known to control food intake. Ghrelin is orexigenic; it is secreted from the stomach and circulates in the blood stream under fasting conditions, indicating that it transmits a hunger signal from the periphery to the central nervous system. Taking into account all these activities, ghrelin plays important roles for maintaining growth hormone release and energy homeostasis in vertebrates. The diverse functions of ghrelin raise the possibility of its clinical application for GH deficiency, eating disorder, gastrointestinal disease, cardiovascular disease, osteoporosis and aging, etc.
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236
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Korhonen T, Mustonen AM, Nieminen P, Saarela S. Effects of cold exposure, exogenous melatonin and short-day treatment on the weight-regulation and body temperature of the Siberian hamster (Phodopus sungorus). ACTA ACUST UNITED AC 2008; 149:60-6. [DOI: 10.1016/j.regpep.2007.09.033] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 09/01/2007] [Indexed: 11/29/2022]
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237
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Inhibition of ghrelin O-acyltransferase (GOAT) by octanoylated pentapeptides. Proc Natl Acad Sci U S A 2008; 105:10750-5. [PMID: 18669668 DOI: 10.1073/pnas.0805353105] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The discovery of ghrelin O-acyltransferase (GOAT) opens the way to the design of drugs that block the attachment of an octanoyl group to the appetite-stimulating peptide hormone ghrelin, potentially preventing obesity. Here, we develop a biochemical assay that uses membranes from insect cells infected with baculovirus encoding mouse GOAT. The GOAT-containing membranes transferred the [(3)H]octanoyl group from [(3)H]octanoyl CoA to recombinant proghrelin in vitro. Transfer depended on the serine at residue 3 of proghrelin, which is the known site of acylation. GOAT also transferred [(3)H]octanoyl to a pentapeptide containing only the N-terminal five amino acids of proghrelin. GOAT activity could be inhibited by an octanoylated ghrelin pentapeptide, and its potency was enhanced 45-fold when the octanoylated serine-3 was replaced by octanoylated diaminopropionic acid. The data suggest that GOAT is subjected to end-product inhibition and this inhibition is better achieved with substrates having the octanoyl group attached through an amide linkage rather than the corresponding ester. These insights may facilitate the future design of useful inhibitors of GOAT.
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238
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Alpha-conotoxin MII-sensitive nicotinic acetylcholine receptors are involved in mediating the ghrelin-induced locomotor stimulation and dopamine overflow in nucleus accumbens. Eur Neuropsychopharmacol 2008; 18:508-18. [PMID: 18343642 DOI: 10.1016/j.euroneuro.2008.02.006] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 01/23/2008] [Accepted: 02/07/2008] [Indexed: 01/28/2023]
Abstract
Previously, we have reported that the orexigenic peptide ghrelin activates the cholinergic-dopaminergic reward link, involving nicotinic acetylcholine receptors (nAChR). The alpha(3)-alpha(7) and beta(2)-beta(4) subunits of the nAChR can be combined into pentameric nAChRs, with different functional roles. The present experiments show that the locomotor stimulatory effects of ghrelin, either into laterodorsal tegmental area (LDTg) or ventral tegmental area (VTA), are mediated via ventral tegmental nAChR, but neither the alpha(4)beta(2) (using dihydro-beta-erythroidine) nor the alpha(7) (using methyllycaconitine) subtypes appears to be involved. On the other hand, the alpha(3)beta(2), beta(3) and/or alpha(6) (using alpha-conotoxin MII) subtypes in the VTA mediate the stimulatory and DA-enhancing effects of ghrelin, a pattern that ghrelin shares with ethanol (n=5-8). Radioligand-binding experiments shown that ghrelin does not interfere directly with nAChRs (n=26). We therefore suggest that the alpha(3)beta(2), beta(3) and/or alpha(6) subtypes might be pharmacological targets for treatment of addictive behaviours including compulsive overeating and alcoholism.
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239
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Strassburg S, Anker SD, Castaneda TR, Burget L, Perez-Tilve D, Pfluger PT, Nogueiras R, Halem H, Dong JZ, Culler MD, Datta R, Tschöp MH. Long-term effects of ghrelin and ghrelin receptor agonists on energy balance in rats. Am J Physiol Endocrinol Metab 2008; 295:E78-84. [PMID: 18460598 PMCID: PMC2493589 DOI: 10.1152/ajpendo.00040.2008] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ghrelin, an endogenous ligand of the growth hormone secretagogue receptor (GHS-R), is the only circulating agent to powerfully promote a positive energy balance. Such action is mediated predominantly by central nervous system pathways controlling food intake, energy expenditure, and nutrient partitioning. The ghrelin pathway may therefore offer therapeutic potential for the treatment of catabolic states. However, the potency of the endogenous hormone ghrelin is limited due to a short half-life and the fragility of its bioactivity ensuring acylation at serine 3. Therefore, we tested the metabolic effects of two recently generated GHS-R agonists, BIM-28125 and BIM-28131, compared with ghrelin. All agents were administered continuously for 1 mo in doses of 50 and 500 nmol x kg(-1) x day(-1) using implanted subcutaneous minipumps in rats. High-dose treatment with single agonists or ghrelin increased body weight gain by promoting fat mass, whereas BIM-28131 was the only one also increasing lean mass significantly. Food intake increased during treatment with BIM-28131 or ghrelin, whereas no effects on energy expenditure were detected. With the lower dose, only BIM-28131 had a significant effect on body weight. This also held true when the compound was administered by subcutaneous injection three times/day. No symptoms or signs of undesired effects were observed in any of the studies or treated groups. These results characterize BIM-28131 as a promising GHS-R agonist with an attractive action profile for the treatment of catabolic disease states such as cachexia.
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Affiliation(s)
- Sabine Strassburg
- Department of Psychiatry, Obesity Research Centre-Genome Research Institute, Univ. of Cincinnati-College of Medicine, Cincinnati, OH, USA
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240
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Pusztai P, Sarman B, Ruzicska E, Toke J, Racz K, Somogyi A, Tulassay Z. Ghrelin: a new peptide regulating the neurohormonal system, energy homeostasis and glucose metabolism. Diabetes Metab Res Rev 2008; 24:343-52. [PMID: 18350524 DOI: 10.1002/dmrr.830] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Identification of ghrelin started with the discovery of growth hormone secretagogues, continued with the description of ghrelin receptors and ended with the elucidation of the chemical structure of ghrelin. However, several issues concerning the role of ghrelin in physiological and pathophysiological processes are still under investigation. Most of the ghrelin produced in the body is secreted in the stomach, but it is also expressed in the hypothalamus, pituitary, pancreas, intestine, kidney, heart and gonads. Ghrelin stimulates growth hormone secretion via growth hormone secretagogue receptors. Ghrelin secretion in the stomach depends on both acute and chronic changes in nutritional status and energy balance. Current data support the hypothesis that the stomach, in addition to its important role in digestion, not only influences pituitary hormone secretion but, via ghrelin production, it also sends orexigenic (appetite increasing) signals to hypothalamic nuclei involved in the regulation of energy homeostasis. In addition to these main effects, ghrelin influences insulin secretion and glucose metabolism and it may exert potentially important effects on cardiovascular and gastrointestinal functions. Because of its effects on a large number of physiological functions, ghrelin may be involved in the pathomechanism of several human disorders, including disturbances of appetite, energy homeostasis and glucose metabolism. Further research might lead to a better understanding of the pathophysiology of ghrelin and might provide more effective therapy for the above disorders.
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Affiliation(s)
- Peter Pusztai
- 2nd Department of Medicine, Semmelweis University, Budapest, Hungary.
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241
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Abstract
Advances in the understanding of appetite are leading to a refined concept of disease cachexia and point to novel therapeutic strategies based on the manipulation of appetite. The complex social and psychological short-term influences on appetite obscure the fact that over the longer term appetite is tightly regulated by physiological considerations; the homeostatic control of energy balance. Like obesity, which is now viewed as a disorder of homeostasis, cachexia can be seen as an adaptive response to the disease state that becomes harmful when prolonged. Several lines of evidence implicate a disorder of appetite regulation in the pathogenesis of cachexia. As the only known circulating mediator of increased appetite the peptide hormone ghrelin has attracted attention as a potential therapy. Trials in patients with various chronic illnesses, including cancer and kidney failure, have demonstrated short-term increases in energy intake. Trials in patients with emphysema and heart failure have also shown benefits in clinical outcomes such as lean body mass and exercise capacity, and longer-term trials using oral analogues are being undertaken. As well as improving nutrition, ghrelin has a number of other actions that may be useful, including an anti-inflammatory effect; of interest since many cachexias are associated with inappropriate immune activation. The manipulation of appetite, in particular by ghrelin agonism, is emerging as an exciting potential therapy for disease cachexia. Future research should focus on the ascertainment of clinically-relevant outcomes, and further characterisation of the non-nutritional effects of this pathway.
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242
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Stevanović D, Nešić D, Milošević V, Starčević V, Severs W. Consummatory behavior and metabolic indicators after central ghrelin injections in rats. ACTA ACUST UNITED AC 2008; 147:52-9. [DOI: 10.1016/j.regpep.2008.01.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Revised: 10/23/2007] [Accepted: 01/02/2008] [Indexed: 12/01/2022]
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243
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Reed JA, Benoit SC, Pfluger PT, Tschöp MH, D'Alessio DA, Seeley RJ. Mice with chronically increased circulating ghrelin develop age-related glucose intolerance. Am J Physiol Endocrinol Metab 2008; 294:E752-60. [PMID: 18270302 DOI: 10.1152/ajpendo.00463.2007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ghrelin is a gut peptide that stimulates food intake and increases body fat mass when administered centrally or peripherally. In this study, ghrelin was overexpressed in neurons using the neuron-specific enolase (NSE) promoter sequences and mouse ghrelin cDNA (NSE-Ghr). Ghrelin expression in NSE-Ghr brain tissues was increased compared with wild-type mice. Ghrelin expression was also increased to a much smaller extent in liver of these mice, but mRNA levels in stomach or duodenum did not differ from wild-type mice. Body weight and composition was analyzed in two lines of NSE-Ghr mice, one line with increased circulating bioactive ghrelin (L43) and one line without (L73). No increases in body weight, food intake, or fat mass were found. Energy expenditure was measured in L43 mice and did not differ from wild-type controls, whereas locomotor activity was increased in NSE-Ghr mice. Young NSE-Ghr mice had normal glucose tolerance; however, L43 NSE-Ghr mice, but not L73 mice, developed glucose intolerance at 32 wk of age. Despite the impaired glucose tolerance in L43 mice, insulin levels did not differ from those of wild-type mice. These findings suggest a role for ghrelin in age-associated impairments of glucose homeostasis.
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Affiliation(s)
- Jacquelyn A Reed
- Department of Psychiatry, Genome Research Institute, University of Cincinnati, Cincinnati, OH 45237, USA
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244
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Dezaki K, Sone H, Yada T. Ghrelin is a physiological regulator of insulin release in pancreatic islets and glucose homeostasis. Pharmacol Ther 2008; 118:239-49. [PMID: 18433874 DOI: 10.1016/j.pharmthera.2008.02.008] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Accepted: 02/26/2008] [Indexed: 12/18/2022]
Abstract
Ghrelin, an acylated 28-amino acid peptide, was isolated from the stomach as the endogenous ligand for the growth hormone (GH) secretagogue receptor (GHS-R). Circulating ghrelin is produced predominantly in the oxyntic mucosa of stomach. Ghrelin potently stimulates GH release and feeding, and exhibits positive cardiovascular effects, suggesting a possible clinical application. Low plasma ghrelin levels are associated with elevated fasting insulin levels and insulin resistance, suggesting both physiological and pathophysiological roles for ghrelin in glucose metabolism. Here, we review the physiological role of ghrelin in the regulation of insulin release and glucose metabolism, and a potential therapeutic avenue to treat type 2 diabetes by manipulating ghrelin and/or its signaling. Ghrelin inhibits insulin release in mice, rats and humans. The signal transduction mechanisms of ghrelin in islet beta-cells are distinct from those utilized in GH-releasing and/or GHS-R-expressing cells. Ghrelin is expressed in pancreatic islets and released into pancreatic microcirculations. Pharmacological and genetic blockades of islet-derived ghrelin markedly augment glucose-induced insulin release in vitro. In high-fat diet-induced mildly obese mice, ghrelin-deficiency enhances insulin release and prevents impaired glucose tolerance. Thus, manipulation of insulinostatic function of ghrelin--GHS-R system, particularly that in islets, could optimize the amount of insulin release to meet the systemic demand, providing a potential therapeutic application to prevent type 2 diabetes.
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Affiliation(s)
- Katsuya Dezaki
- Division of Integrative Physiology, Department of Physiology, Jichi Medical University School of Medicine, Yakushiji 3311-1, Shimotsuke, Tochigi 329-0498, Japan.
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245
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Identification of the acyltransferase that octanoylates ghrelin, an appetite-stimulating peptide hormone. Cell 2008; 132:387-96. [PMID: 18267071 DOI: 10.1016/j.cell.2008.01.017] [Citation(s) in RCA: 850] [Impact Index Per Article: 53.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2007] [Revised: 01/08/2008] [Accepted: 01/17/2008] [Indexed: 12/22/2022]
Abstract
Ghrelin 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.
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246
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Vulliémoz NR, Xiao E, Xia-Zhang L, Rivier J, Ferin M. Astressin B, a nonselective corticotropin-releasing hormone receptor antagonist, prevents the inhibitory effect of ghrelin on luteinizing hormone pulse frequency in the ovariectomized rhesus monkey. Endocrinology 2008; 149:869-74. [PMID: 18063681 PMCID: PMC2275354 DOI: 10.1210/en.2007-1350] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Administration of ghrelin, a key peptide in the regulation of energy homeostasis, has been shown to decrease LH pulse frequency while concomitantly elevating cortisol levels. Because increased endogenous CRH release in stress is associated with an inhibition of reproductive function, we have tested here whether the pulsatile LH decrease after ghrelin may reflect an activated hypothalamic-pituitary-adrenal axis and be prevented by a CRH antagonist. After a 3-h baseline LH pulse frequency monitoring, five adult ovariectomized rhesus monkeys received a 5-h saline (protocol 1) or ghrelin (100-microg bolus followed by 100 microg/h, protocol 2) infusion. In protocols 3 and 4, animals were given astressin B, a nonspecific CRH receptor antagonist (0.45 mg/kg im) 90 min before ghrelin or saline infusion. Blood samples were taken every 15 min for LH measurements, whereas cortisol and GH were measured every 45 min. Mean LH pulse frequency during the 5-h ghrelin infusion was significantly lower than in all other treatments (P < 0.05) and when compared with the baseline period (P < 0.05). Pretreatment with astressin B prevented the decrease. Ghrelin stimulated cortisol and GH secretion, whereas astressin B pretreatment prevented the cortisol, but not the GH, release. Our data indicate that CRH release mediates the inhibitory effect of ghrelin on LH pulse frequency and suggest that the inhibitory impact of an insufficient energy balance on reproductive function may in part be mediated by the hypothalamic-pituitary-adrenal axis.
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Affiliation(s)
- Nicolas R Vulliémoz
- Department of Obstetrics and Gynecology, College of Physicians and Surgeons, Columbia University, 630 West 168th Street, New York, New York 10032, USA
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247
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Ghrelin in the CNS: from hunger to a rewarding and memorable meal? ACTA ACUST UNITED AC 2008; 58:160-70. [PMID: 18308399 DOI: 10.1016/j.brainresrev.2008.01.004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Revised: 01/20/2008] [Accepted: 01/23/2008] [Indexed: 01/19/2023]
Abstract
Ghrelin, the endogenous agonist of the growth hormone secretagogue receptor, has been shown to induce robust feeding responses in numerous experimental models. Although ghrelin comes from both peripheral and central sources, its hyperphagic properties, to a large extent, arise from activity at the brain level. The current review focuses on describing central mechanisms through which this peptide affects consumption. We address the issue of whether ghrelin serves just as a signal of energy needs of the organism or - as suggested by the most recent findings - also affects food intake via other feeding-related mechanisms, including reward and memory. Complexity of ghrelin's role in the regulation of ingestive behavior is discussed by characterizing its influence on consumption, reward and memory as well as by defining its function within the brain circuitry and interplay with other neuropeptides.
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248
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Bjursell M, Gerdin AK, Lelliott CJ, Egecioglu E, Elmgren A, Törnell J, Oscarsson J, Bohlooly-Y M. Acutely reduced locomotor activity is a major contributor to Western diet-induced obesity in mice. Am J Physiol Endocrinol Metab 2008; 294:E251-60. [PMID: 18029443 DOI: 10.1152/ajpendo.00401.2007] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The aim of the present study was to investigate the short- and long-term effects of a high-fat Western diet (WD) on intake, storage, expenditure, and fecal loss of energy as well as effects on locomotor activity and thermogenesis. WD for only 24 h resulted in a marked physiological shift in energy homeostasis, including increased body weight gain, body fat, and energy expenditure (EE) but an acutely lowered locomotor activity. The acute reduction in locomotor activity was observed after only 3-5 h on WD. The energy intake and energy absorption were increased during the first 24 h, lower after 72 h, and normalized between 7 and 14 days on WD compared with mice given chow diet. Core body temperature and EE was increased between 48 and 72 h but normalized after 21 days on WD. These changes paralleled plasma T(3) levels and uncoupling protein-1 expression in brown adipose tissue. After 21 days of WD, energy intake and absorption, EE, and body temperature were normalized. In contrast, the locomotor activity was reduced and body weight gain was increased over the entire 21-day study period on WD. Calculations based on the correlation between locomotor activity and EE in 2-h intervals at days 21-23 indicated that a large portion of the higher body weight gain in the WD group could be attributed to the reduced locomotor activity. In summary, an acute and persisting decrease in locomotor activity is most important for the effect of WD on body weight gain and obesity in mice.
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249
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Rao AA, Sridhar GR, Srinivas B, Das UN. Bioinformatics analysis of functional protein sequences reveals a role for brain-derived neurotrophic factor in obesity and type 2 diabetes mellitus. Med Hypotheses 2008; 70:424-9. [PMID: 17553627 DOI: 10.1016/j.mehy.2007.03.034] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2007] [Accepted: 03/12/2007] [Indexed: 10/23/2022]
Abstract
Using bioinformatics techniques and sequence analyses algorithms, a comparative study between human and rodents revealed similarity in the behavior of genes involved in the control of energy homeostasis. Brain-derived neurotrophic factor (BDNF) modulates the secretion and actions of insulin, leptin, ghrelin, various neurotransmitters and peptides, and pro-inflammatory cytokines involved in energy homeostasis suggesting that it (BDNF) has a significant role in the pathobiology of obesity and type 2 diabetes mellitus. Based on these evidences, we propose that obesity and type 2 diabetes could be disorders of the brain and BDNF could serve as a biomarker in predicting their development. Hence, methods developed to selectively deliver BDNF to appropriate hypothalamic neurons may form a novel approach in their treatment.
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Affiliation(s)
- Allam Appa Rao
- Department of Computer Science and Systems Engineering, Andhra University, Visakhapatnam 530 003, India
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250
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Sato T, Kurokawa M, Nakashima Y, Ida T, Takahashi T, Fukue Y, Ikawa M, Okabe M, Kangawa K, Kojima M. Ghrelin deficiency does not influence feeding performance. ACTA ACUST UNITED AC 2008; 145:7-11. [PMID: 17913260 DOI: 10.1016/j.regpep.2007.09.010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor that is synthesized predominantly in the stomach. Previous studies demonstrated that ghrelin stimulates growth hormone release and food intake. These data suggested that antagonism of ghrelin could serve as a useful treatment for eating disorders and obesity. To study the role of endogenous ghrelin in feeding performance further, we generated ghrelin-deficient (ghrl(-/-)) mice. Unexpectedly, ghrl(-/-) mice exhibited normal growth, cumulative food intake, reproduction, histological characters, and serum parameters. There were no differences in feeding patterns between ghrl(+/+) and ghrl(-/-) mice. Ghrl(-/-) mice displayed normal responses to scheduled feedings as seen for ghrl(+/+) mice. Memory-related feeding performances of ghrl(-/-) mice were indistinguishable from ghrl(+/+) littermates. These data indicate that ghrelin is not critical for feeding performance.
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Affiliation(s)
- Takahiro Sato
- Molecular genetics, Institute of Life Sciences, Kurume University, B-3, Kurume research center building, 1-1, Hyakunen-koen, Kurume, 839-0864, Japan
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