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Reproductive Neuroscience Unit (T.L.H., S.D.), Department of Obstetrics and Gynecology and Department of Neurobiology (T.L.H.), Yale Medical School, New Haven, Connecticut 06520; Department of Anatomy and Histology (P.S.), Faculty of Veterinary Science, Szent Istvan University, Budapest, Hungary 1400; and Lilly Research Laboratories (M.H., M.T.), Eli Lilly & Co., Indianapolis, Indiana 46285
Address all correspondence and requests for reprints to: Tamas Horvath, Department of Obstetrics/Gynecology, Yale Medical School, 333 Cedar Street, FMB 339, New Haven, Connecticut 06520. E-mail: tamas.horvath{at}yale.edu
| Abstract |
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| Introduction |
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| Discovery of Ghrelin |
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| Sources of Ghrelin |
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One of the most urgent and debatable hypotheses is whether ghrelin is produced in physiologically relevant amounts in the hypothalamus. This unresolved issue is the focus of several research groups. Data published or presented at recent meetings, in accordance with our own ongoing investigations, have shown ghrelin to be present in several regions of the hypothalamus through the use of immunohistochemical detection methods (8, 22). Depending on the ghrelin epitope recognized by the antibody in use, ghrelin-positive cells have been identified in varying hypothalamic areas, whereas all of these antisera have been successfully used in RIAs. Detection of hypothalamic ghrelin mRNA by use of PCR has been accomplished (8); however, this issue needs to be further investigated by the detection and regional distribution of ghrelin mRNA by in situ hybridization. At this point, it is not clear if the detection of ghrelin in the hypothalamus using immunohistochemistry reflects ghrelin peptide that is produced by hypothalamic neurons or ghrelin peptide that is derived from the stomach. It seems logical that gastric ghrelin reflects an acute nutritional state. However, even minimal ghrelin expression in the hypothalamus (8, 12) or circulating placental ghrelin during pregnancy (25) may significantly influence food intake, nutrition partitioning, and fat utilization. Regardless of the source, in the end it is most likely the modulation of hypothalamic circuits by ghrelin that mediates changes in energy homeostasis.
| Ghrelin and GH Secretion |
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| Ghrelin and Energy Balance |
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In humans, circulating ghrelin levels are decreased in chronic (obesity) (48) and acute (caloric intake) (26, 34, 47) states of positive energy balance, whereas plasma levels of ghrelin are increased by fasting (12, 34) and in cachectic patients with anorexia nervosa (26). Of course, it has yet to be proven that the rather modest changes in circulating ghrelin, in the 100 fmol range, have physiological relevance for hypothalamic receptor sites. One plausible explanation is that if ghrelin is indeed a hormone signaling the need to conserve energy (12), ghrelin secretion is triggered to counter further deficit of energy storage and to prevent starvation or cachexia. A very recent study shows a pre-meal rise of human plasma ghrelin, suggesting a possible role of ghrelin as a hunger signal triggering meal initiation (34). In rodents, fasting and hypoglycemia increase ghrelin levels, whereas intake of food, especially carbohydrates (dextrose), decreases ghrelin secretion (12, 41, 50). We speculate that this obvious connection between glucose levels, ghrelin secretion and GH secretion is likely to be involved in the physiological mechanism of diagnostic procedures such as oral glucose tolerance testing (for acromegaly) and insulin tolerance testing (for GH deficiency). Differential effects of ghrelin might be mediated by separate ghrelin (GHS-R) subtypes as recently suggested by Thorner and co-workers (51). Based on a series of elaborate studies using GHS-R antagonists ([D-Lys3]GHRP-6 and BMS-265711, also an NPY-antagonist) and an NPY-Y1-R antagonist ([D-Trp32]NPY), they showed that the orexigenic effect of ghrelin can be dissociated from its GH releasing effects, suggesting distinct GHS-R-subtypes. Based on the observation of differential orexigenic effects of hexarelin and its analogs and GH secretagogue actions at the pituitary gland (52, 53), the existence of additional subtypes of the GHS-R (16, 17, 18) had previously been hypothesized. The putative adipogenic effects of ghrelin in humans remains to be shown because it is possible that ghrelin has different effects on energy balance in humans and rodents. In addition, ghrelin-induced adiposity could be only a transient effect and the therapeutic potential of ghrelin in cachectic humans might therefore turn out to be as disappointing as the efficacy of leptin for the therapy of human obesity (5, 54). Carefully conducted clinical studies focusing on body composition as well as long-term studies on ghrelin treatment in rodents are necessary to further address this question.
| Ghrelin and Brain Centers of Energy Balance |
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-MSH (6, 7, 72) that is produced in arcuate nucleus perikarya
(73).
An important milestone to link the central regulation of metabolism
with peripheral levels of energy storage was the discovery of the
adipose hormone, leptin. Genetic mouse or rat mutants, including
db/db and ob/ob mice and fa/fa rats
become strikingly obese. Molecular analysis has shown that the primary
genetic defect in these animals relates to either abolished leptin
production (ob/ob mice) or impaired leptin receptors
(db/db mice; fa/fa rats; leptin-R) (5, 74, 75, 76, 77). Similar examples of obesity in humans have been found
and are associated with a mutation of leptin or the leptin-receptor
(78, 79, 80). Leptin is released by adipose tissue and has
been suggested to be the key-signal reflecting adipose stores. Leptin
receptors are found in the hypothalamus, particularly in the arcuate
nucleus where leptin is thought to exert its primary feedback signaling
(81, 82, 83, 84, 85, 86, 87). Recent experiments in rodents and primates have
been attempting to tie together the diverse hypothalamic peptidergic
systems with hormone receptors, including leptin receptors, to decipher
the hypothalamic signaling modality underlying the regulation of daily
energy homeostasis (81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92). A schematic illustration of
some of these interactions and the way ghrelin signaling may be
integrated into these circuits is shown on Fig. 1
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-MSH, a main anorexigen and energy
expenditure enhancer (72), and to its interrelationship
with another group of arcuate nucleus neurons that produce both NPY and
an endogenous antagonist of
-MSH, AGRP (69). The
interaction between these two distinct populations of cells is
currently considered as a primum movens in the regulation of
energy homeostasis. However, there are other peptidergic circuits
within the hypothalamus, including the lateral hypothalamic
orexin/hypocretin- and melanin concentrating hormone-producing cells,
that appear to respond to peripheral metabolic signals and alter food
intake as well as energy expenditure (65, 66, 67, 68). In light of
the aforementioned excellent reviews (2, 3, 4, 5, 6, 7), we will avoid
an in-depth description of these peptidergic systems here but will
attempt to emphasize a better appreciation of the neuronal doctrine for
the integration of emerging experimental data on ghrelin. In the brain, receptors for ghrelin were detected in multiple hypothalamic nuclei as well as in the hippocampus, substantia nigra, ventral tegmental area, and dorsal and median raphe nuclei (8, 94, 95, 96, 97, 98). In a series of experiments, Dickson and co-workers, first using synthetic GHS-R agonist, and then ghrelin, provided evidence that this novel metabolic hormone, in fact, interacts with the aforementioned hypothalamic peptidergic systems in the central regulation of metabolism (99, 100, 101, 102, 103). For example, they found that following central ghrelin administration, c-fos, an early proto-oncogen that reflects cellular activity, is induced in the medial arcuate nucleus where NPY/AGRP cells are located (103). It was also shown that Y1-receptor antagonists as well as melanocortin agonists and antisera to both NPY and AGRP may interfere with ghrelins feeding-inducing effect (42, 43, 46). However, absence of NPY in genetically engineered NPY-ko mice does not diminish ghrelin-induced feeding or adiposity suggesting a key-role for AGRP in the mediation of ghrelins effects on energy balance (12). The effect of ghrelin on metabolism seems to be the exact opposite to that of leptin (2, 3, 4, 5, 6, 7, 9, 10, 12). In obesity, when plasma leptin levels are elevated, ghrelin plasma levels are decreased indicating physiological adaptations to the positive energy balance rather than an involvement in the etiology of obesity (48, 49). Of course, it is important to note that, while ghrelin is regulated acutely like a satiety factor, leptin levels are not regulated by meals, but rather by actual increase in adipose stores.
| Ghrelins Hypothalamic Signaling Requires Synapses |
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The hypothalamus is composed of a complicated set of regulatory neurons
that in most cases cannot be identified by traditional means of cell
segregation, i.e. location, soma size, or dendritic arbor.
Therefore, to identify specific types of neurons, cytochemistry must be
used. In addition, as in all other brain areas, the primary mode of
communication between hypothalamic peptidergic circuits is via
synapses. The only reliable way for assessing synapses is by the use of
conventional electron microscopy and electrophysiology because
proximity of different cells assessed by light microscopy is not a
convincing indicator of neuronal interaction. Thus, determination of
the qualitative and quantitative synaptological relationship between
GHS-Rs, ghrelin-producing neurons, and other key hypothalamic
peptidergic systems and their receptors will be an important step for
gaining insight into the hypothalamic signaling modality of ghrelin. Of
course, the anatomical experiments alone will not be sufficient to
determine the actual involvement of the presynaptic ghrelin system in
the regulation of the postsynaptic circuit, but provides an invaluable
map that is necessary for the correct interpretation of data gathered
with other tools. In fact, anatomical studies need to be complemented
by parallel electrophysiological analyses. An elegant example of such
an approach is the recent work by Cowley and colleagues
(111), in which leptins effect was analyzed on
genetically tagged arcuate nucleus
-MSH cells and the qualitative
synaptology of these cells was simultaneously assessed. That approach
not only eliminated the pitfalls of the individual experimental
techniques but immediately provided a more comprehensive view on a
given hypothalamic neuronal system (111).
The significance in determining the spatial relationship between
different afferents using anatomical and electrophysiological tools may
further be appreciated when one considers that a synapse is more
potently able to affect postsynaptic cells when located proximally
either on the cell body or postsynaptic dendrite than when it is
located more distally. In addition, both previous electrophysiological
(111, 112, 113) and morphological observations (92, 111) indicate that an extensive interaction exists between
presynaptic terminals to affect hypothalamic cells both in the arcuate
nucleus where NPY/AGRP and
-MSH cell bodies are located and in a
model efferent target, the parvicellular paraventricular nucleus. The
impact of ghrelin on arcuate and parvicellular paraventricular nucleus
neurons will be readily dependent on their synaptic organization on the
postsynaptic cells and their interaction with other systems
presynaptically. One of the best examples to illustrate this
synaptologic interaction is the relationship between the NPY/AGRP and
-MSH systems. Electrophysiological and anatomical observations
pointed to both the arcuate and paraventricular nuclei as primary sites
for the interplay between AGRP and
-MSH systems (111, 114). Because ghrelins action appears to be mediated by the
NPY/AGRP system, it is not unlikely that ghrelin will act in the
arcuate nucleus as well as in the paraventricular nucleus to modulate
the interaction between NPY/AGRP and
-MSH. It may be that peripheral
and central ghrelin contribute equally to the regulation of both of
these hypothalamic areas, but it is also conceivable that
stomach-derived ghrelin affects the arcuate nucleus where the
blood-brain barrier is less effective, whereas hypothalamic ghrelin is
more involved in the modulation of hypothalamic sites within the
blood-brain barrier, such as the paraventricular nucleus. An
alternative and equally feasible pathway for ghrelin signaling from the
stomach is via an ascending neural network through the vagus nerve and
brain stem nuclei that ultimately reaches the hypothalamus
(43).
When electrophysiological and anatomical techniques are combined with conventional physiological and molecular biological approaches, as well as with the very recently developed revolutionary tracing technique of DeFalco et al. [(115) which allows tracing of inputs of chemically identified subpopulations of neurons], it is reasonable to expect that not only a thorough understanding of ghrelins action will be achieved at a faster pace, but great advances will be made toward the general understanding of the hypothalamic machinery in metabolism regulation.
| Acknowledgments |
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| Footnotes |
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Abbreviations: AGRP, Agouti-related protein; GHRP, GH-releasing peptide; GHS, GH-secretagogue; GHS-R, GHS receptor.
Received June 8, 2001.
Accepted for publication July 27, 2001.
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-melanocyte-stimulating
hormone an ß-endorphin (ACTH,
-MSH, ß-END) in the rat
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A. J. van der Lely, M. Tschop, M. L. Heiman, and E. Ghigo Biological, Physiological, Pathophysiological, and Pharmacological Aspects of Ghrelin Endocr. Rev., June 1, 2004; 25(3): 426 - 457. [Abstract] [Full Text] [PDF] |
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K. L. Teff, S. S. Elliott, M. Tschop, T. J. Kieffer, D. Rader, M. Heiman, R. R. Townsend, N. L. Keim, D. D'Alessio, and P. J. Havel Dietary Fructose Reduces Circulating Insulin and Leptin, Attenuates Postprandial Suppression of Ghrelin, and Increases Triglycerides in Women J. Clin. Endocrinol. Metab., June 1, 2004; 89(6): 2963 - 2972. [Abstract] [Full Text] [PDF] |
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T. L. Horvath, S. Diano, and M. Tschop Brain Circuits Regulating Energy Homeostasis Neuroscientist, June 1, 2004; 10(3): 235 - 246. [Abstract] [PDF] |
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A. Dzaja, M. A. Dalal, H. Himmerich, M. Uhr, T. Pollmacher, and A. Schuld Sleep enhances nocturnal plasma ghrelin levels in healthy subjects Am J Physiol Endocrinol Metab, June 1, 2004; 286(6): E963 - E967. [Abstract] [Full Text] [PDF] |
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C. Y. Bowers, R. Granda, S. Mohan, J. Kuipers, D. Baylink, and J. D. Veldhuis Sustained Elevation of Pulsatile Growth Hormone (GH) Secretion and Insulin-Like Growth Factor I (IGF-I), IGF-Binding Protein-3 (IGFBP-3), and IGFBP-5 Concentrations during 30-Day Continuous Subcutaneous Infusion of GH-Releasing Peptide-2 in Older Men and Women J. Clin. Endocrinol. Metab., May 1, 2004; 89(5): 2290 - 2300. [Abstract] [Full Text] [PDF] |
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S. V. Angeloni, N. Glynn, G. Ambrosini, M. J. Garant, J. Dee Higley, S. Suomi, and B. C. Hansen Characterization of the Rhesus Monkey Ghrelin Gene and Factors Influencing Ghrelin Gene Expression and Fasting Plasma Levels Endocrinology, May 1, 2004; 145(5): 2197 - 2205. [Abstract] [Full Text] [PDF] |
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Y. Lin, K. Matsumura, M. Fukuhara, S. Kagiyama, K. Fujii, and M. Iida Ghrelin Acts at the Nucleus of the Solitary Tract to Decrease Arterial Pressure in Rats Hypertension, May 1, 2004; 43(5): 977 - 982. [Abstract] [Full Text] [PDF] |
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A. INUI, A. ASAKAWA, C. Y. BOWERS, G. MANTOVANI, A. LAVIANO, M. M. MEGUID, and M. FUJIMIYA Ghrelin, appetite, and gastric motility: the emerging role of the stomach as an endocrine organ FASEB J, March 1, 2004; 18(3): 439 - 456. [Abstract] [Full Text] [PDF] |
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P. J. Havel Update on Adipocyte Hormones: Regulation of Energy Balance and Carbohydrate/Lipid Metabolism Diabetes, February 1, 2004; 53(90001): S143 - 151. [Abstract] [Full Text] |
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G. Murdolo, P. Lucidi, C. Di Loreto, N. Parlanti, A. De Cicco, C. Fatone, C. G. Fanelli, G. B. Bolli, F. Santeusanio, and P. De Feo Insulin is Required for Prandial Ghrelin Suppression in Humans Diabetes, December 1, 2003; 52(12): 2923 - 2927. [Abstract] [Full Text] [PDF] |
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Y. Sun, S. Ahmed, and R. G. Smith Deletion of Ghrelin Impairs neither Growth nor Appetite Mol. Cell. Biol., November 15, 2003; 23(22): 7973 - 7981. [Abstract] [Full Text] [PDF] |
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B. Beck, S. Richy, and A. Stricker-Krongrad Ghrelin and Body Weight Regulation in the Obese Zucker Rat in Relation to Feeding State and Dark/Light Cycle Experimental Biology and Medicine, November 1, 2003; 228(10): 1124 - 1131. [Abstract] [Full Text] [PDF] |
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Y. Ueta, Y. Ozaki, J. Saito, and T. Onaka Involvement of Novel Feeding-Related Peptides in Neuroendocrine Response to Stress Experimental Biology and Medicine, November 1, 2003; 228(10): 1168 - 1174. [Abstract] [Full Text] [PDF] |
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B. Holst, A. Cygankiewicz, T. H. Jensen, M. Ankersen, and T. W. Schwartz High Constitutive Signaling of the Ghrelin Receptor--Identification of a Potent Inverse Agonist Mol. Endocrinol., November 1, 2003; 17(11): 2201 - 2210. [Abstract] [Full Text] [PDF] |
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J. E. Caminos, R. Nogueiras, M. Blanco, L. M. Seoane, S. Bravo, C. V. Alvarez, T. Garcia-Caballero, F. F. Casanueva, and C. Dieguez Cellular Distribution and Regulation of Ghrelin Messenger Ribonucleic Acid in the Rat Pituitary Gland Endocrinology, November 1, 2003; 144(11): 5089 - 5097. [Abstract] [Full Text] [PDF] |
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A.-S. Parent, G. Teilmann, A. Juul, N. E. Skakkebaek, J. Toppari, and J.-P. Bourguignon The Timing of Normal Puberty and the Age Limits of Sexual Precocity: Variations around the World, Secular Trends, and Changes after Migration Endocr. Rev., October 1, 2003; 24(5): 668 - 693. [Abstract] [Full Text] [PDF] |
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X. Qi, J. Reed, E. W. Englander, V. Chandrashekar, A. Bartke, and G. H. Greeley Jr. Evidence That Growth Hormone Exerts a Feedback Effect on Stomach Ghrelin Production and Secretion Experimental Biology and Medicine, October 1, 2003; 228(9): 1028 - 1032. [Abstract] [Full Text] [PDF] |
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F. Broglio, C. Gottero, A. Benso, F. Prodam, S. Destefanis, C. Gauna, M. Maccario, R. Deghenghi, A. J. van der Lely, and E. Ghigo Effects of Ghrelin on the Insulin and Glycemic Responses to Glucose, Arginine, or Free Fatty Acids Load in Humans J. Clin. Endocrinol. Metab., September 1, 2003; 88(9): 4268 - 4272. [Abstract] [Full Text] [PDF] |
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J. M. Zigman and J. K. Elmquist Minireview: From Anorexia to Obesity--The Yin and Yang of Body Weight Control Endocrinology, September 1, 2003; 144(9): 3749 - 3756. [Abstract] [Full Text] [PDF] |
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J. C. Bunt, A. D. Salbe, M. H. Tschop, A. DelParigi, P. Daychild, and P. A. Tataranni Cross-Sectional and Prospective Relationships of Fasting Plasma Ghrelin Concentrations with Anthropometric Measures in Pima Indian Children J. Clin. Endocrinol. Metab., August 1, 2003; 88(8): 3756 - 3761. [Abstract] [Full Text] [PDF] |
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S. Corbetta, M. Peracchi, V. Cappiello, A. Lania, E. Lauri, L. Vago, P. Beck-Peccoz, and A. Spada Circulating Ghrelin Levels in Patients with Pancreatic and Gastrointestinal Neuroendocrine Tumors: Identification of One Pancreatic Ghrelinoma J. Clin. Endocrinol. Metab., July 1, 2003; 88(7): 3117 - 3120. [Abstract] [Full Text] [PDF] |
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C. Anderwald, G. Brabant, E. Bernroider, R. Horn, A. Brehm, W. Waldhausl, and M. Roden Insulin-Dependent Modulation of Plasma Ghrelin and Leptin Concentrations Is Less Pronounced in Type 2 Diabetic Patients Diabetes, July 1, 2003; 52(7): 1792 - 1798. [Abstract] [Full Text] [PDF] |
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K. Kawamura, N. Sato, J. Fukuda, H. Kodama, J. Kumagai, H. Tanikawa, A. Nakamura, Y. Honda, T. Sato, and T. Tanaka Ghrelin Inhibits the Development of Mouse Preimplantation Embryos in Vitro Endocrinology, June 1, 2003; 144(6): 2623 - 2633. [Abstract] [Full Text] [PDF] |
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V. Simonneaux and C. Ribelayga Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters Pharmacol. Rev., June 1, 2003; 55(2): 325 - 395. [Abstract] [Full Text] [PDF] |
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P. U. Freda, C. M. Reyes, I. M. Conwell, R. E. Sundeen, and S. L. Wardlaw Serum Ghrelin Levels in Acromegaly: Effects of Surgical and Long-Acting Octreotide Therapy J. Clin. Endocrinol. Metab., May 1, 2003; 88(5): 2037 - 2044. [Abstract] [Full Text] [PDF] |
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M. Faraj, P. J. Havel, S. Phelis, D. Blank, A. D. Sniderman, and K. Cianflone Plasma Acylation-Stimulating Protein, Adiponectin, Leptin, and Ghrelin before and after Weight Loss Induced by Gastric Bypass Surgery in Morbidly Obese Subjects J. Clin. Endocrinol. Metab., April 1, 2003; 88(4): 1594 - 1602. [Abstract] [Full Text] [PDF] |
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J. E. Caminos, M. Tena-Sempere, F. Gaytan, J. E. Sanchez-Criado, M. L. Barreiro, R. Nogueiras, F. F. Casanueva, E. Aguilar, and C. Dieguez Expression of Ghrelin in the Cyclic and Pregnant Rat Ovary Endocrinology, April 1, 2003; 144(4): 1594 - 1602. [Abstract] [Full Text] [PDF] |
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L. M. Seoane, M. Lopez, S. Tovar, F. F. Casanueva, R. Senaris, and C. Dieguez Agouti-Related Peptide, Neuropeptide Y, and Somatostatin-Producing Neurons Are Targets for Ghrelin Actions in the Rat Hypothalamus Endocrinology, February 1, 2003; 144(2): 544 - 551. [Abstract] [Full Text] [PDF] |
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J. C. Weikel, A. Wichniak, M. Ising, H. Brunner, E. Friess, K. Held, S. Mathias, D. A. Schmid, M. Uhr, and A. Steiger Ghrelin promotes slow-wave sleep in humans Am J Physiol Endocrinol Metab, February 1, 2003; 284(2): E407 - E415. [Abstract] [Full Text] [PDF] |
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K. Matsumura, T. Tsuchihashi, K. Fujii, I. Abe, and M. Iida Central Ghrelin Modulates Sympathetic Activity in Conscious Rabbits Hypertension, November 1, 2002; 40(5): 694 - 699. [Abstract] [Full Text] [PDF] |
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P. Lucidi, G. Murdolo, C. Di Loreto, A. De Cicco, N. Parlanti, C. Fanelli, F. Santeusanio, G. B. Bolli, and P. De Feo Ghrelin Is Not Necessary for Adequate Hormonal Counterregulation of Insulin-Induced Hypoglycemia Diabetes, October 1, 2002; 51(10): 2911 - 2914. [Abstract] [Full Text] [PDF] |
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H. Ariyasu, K. Takaya, H. Hosoda, H. Iwakura, K. Ebihara, K. Mori, Y. Ogawa, K. Hosoda, T. Akamizu, M. Kojima, et al. Delayed Short-Term Secretory Regulation of Ghrelin in Obese Animals: Evidenced by a Specific RIA for the Active Form of Ghrelin Endocrinology, September 1, 2002; 143(9): 3341 - 3350. [Abstract] [Full Text] [PDF] |
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H. Kaiya, S. van der Geyten, M. Kojima, H. Hosoda, Y. Kitajima, M. Matsumoto, S. Geelissen, V. M. Darras, and K. Kangawa Chicken Ghrelin: Purification, cDNA Cloning, and Biological Activity Endocrinology, September 1, 2002; 143(9): 3454 - 3463. [Abstract] [Full Text] [PDF] |
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F. Broglio, E. Arvat, A. Benso, C. Gottero, F. Prodam, S. Grottoli, M. Papotti, G. Muccioli, A. J. van der Lely, R. Deghenghi, et al. Endocrine Activities of Cortistatin-14 and Its Interaction with GHRH and Ghrelin in Humans J. Clin. Endocrinol. Metab., August 1, 2002; 87(8): 3783 - 3790. [Abstract] [Full Text] [PDF] |
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W. A. Banks, M. Tschop, S. M. Robinson, and M. L. Heiman Extent and Direction of Ghrelin Transport Across the Blood-Brain Barrier Is Determined by Its Unique Primary Structure J. Pharmacol. Exp. Ther., August 1, 2002; 302(2): 822 - 827. [Abstract] [Full Text] [PDF] |
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A. V. Turnbull, L. Ellershaw, D. J. Masters, S. Birtles, S. Boyer, D. Carroll, P. Clarkson, S. J.G. Loxham, P. McAulay, J. L. Teague, et al. Selective Antagonism of the NPY Y5 Receptor Does Not Have a Major Effect on Feeding in Rats Diabetes, August 1, 2002; 51(8): 2441 - 2449. [Abstract] [Full Text] [PDF] |
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M. G. Dube, E. Beretta, H. Dhillon, N. Ueno, P. S. Kalra, and S. P. Kalra Central Leptin Gene Therapy Blocks High-Fat Diet-Induced Weight Gain, Hyperleptinemia, and Hyperinsulinemia : Increase in Serum Ghrelin Levels Diabetes, June 1, 2002; 51(6): 1729 - 1736. [Abstract] [Full Text] [PDF] |
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