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Symposium: Ghrelin: Its Role in Energy Balance

Ghrelin: Its Role in Energy Balance¹

Department of Nutrition, University of Tennessee, Knoxville, TN 37996-1920 and ^* Department of Food Science and Nutrition, University of Minnesota, Twin Cities, St. Paul, MN 55108-6099

²To whom correspondence should be addressed. E-mail: gtruett{at}utk.edu.

Ghrelin was initially described as the endogenous ligand for growth hormone secretogogue receptors (1), which mediate the release of pituitary growth hormone through an alternative to the classical mechanisms of growth hormone release mediated by the growth hormone releasing factor (2). The unexpected observation that stomach was the source of ghrelin led Tschop et al. (3) to investigate its effects on energy balance. They demonstrated that exogenous ghrelin stimulates food intake and reduced fatty acid oxidation to promote positive energy balance.

Since these initial observations, rapid progress has been made in delineating the role of ghrelin in energy balance. The 4 papers in this symposium review recent advances in the physiological role of ghrelin in energy balance regulation. Casteneda et al. (4) show that, in addition it its effects on food intake and metabolism, ghrelin and other peptides modulate spontaneous physical activity. In general, the effects of these peptides on spontaneous physical activity are consistent with their effects on food intake. For example, ghrelin suppresses spontaneous physical activity and leptin stimulates it. Williams and Cummings (5) review the relation between ghrelin and both short- and long-term regulation of food intake. Ghrelin levels fluctuate in synchrony with meals and are influenced by the composition of the meal. The site of the nutrient sensor is likely to be intestinal, rather than in the stomach itself. Ghrelin levels also vary over the long term in response to adiposity, insulin resistance, and gastric surgeries. Geliebter et al. (6) show that ghrelin levels are also influenced by binge-eating disorder in humans. Subjects with binge-eating disorder had lower plasma ghrelin levels prior to a meal, and successful treatment for binge-eating disorder increased their plasma ghrelin levels. Finally, Kalra et al. (7) describe a reciprocal regulatory relation between ghrelin and leptin and propose that leptin suppresses ghrelin release at the periphery and also suppresses the effects of ghrelin on appetite centrally. These presentations describe a rich web of interactions among ghrelin and other central and peripheral regulators of energy balance under a variety of physiological and pathological conditions.

	FOOTNOTES

 
¹ Presented as part of the symposium "Ghrelin: Its Role in Energy Balance" given at the 2004 Experimental Biology meeting on April 19, 2004, Washington, DC. The symposium was sponsored by the American Society for Nutritional Sciences and in part by Abbott Laboratories, Linco Research, Inc., and Merck Research Laboratories. The proceedings are published as a supplement to The Journal of Nutrition. This supplement is the responsibility of the Guest Editors to whom the Editor of The Journal of Nutrition has delegated supervision of both technical conformity to the published regulations of The Journal of Nutrition and general oversight of the scientific merit of each article. The opinions expressed in this publication are those of the authors and are not attributable to the sponsors or the publisher, editor, or editorial board of The Journal of Nutrition. The views expressed herein are those of the authors and do not necessarily reflect those of Abbott Laboratories, Linco Research, Inc., and Merck Research Laboratories. The Guest Editors for the symposium publication are Gary E. Truett, Department of Nutrition, Knoxville, TN, and Elizabeth J. Parks, University of Minnesota, St. Paul, MN.

	LITERATURE CITED

TOP LITERATURE CITED

 

1. Kojima, M., Hosoda, H., Date, Y., Nakazato, M., Matsuo, H. & Kangawa, K. (1999) Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature 402:656-660.[Medline]

2. Smith, R. G., Leonard, R., Bailey, A. R., Palyha, O., Feighner, S., Tan, C., McKee, K. K., Pong, S. S., Griffin, P. & Howard, A. (2001) Growth hormone secretagogue receptor family members and ligands. Endocrine 14:9-14.[Medline]

3. Tschop, M., Smiley, D. L. & Heiman, M. L. (2000) Ghrelin induces adiposity in rodents. Nature 407:908-913.[Medline]

4. Castaneda, T. R., Jürgens, H., Wiedmer, P., Pfluger, P., Diano, S., Horvath, T. L., Tang-Christensen, M. & Tschöp, M. H. (2005) Obesity and the neuroendocrine control of energy homeostasis: The role of spontaneous locomotor activity. J. Nutr. 135:1314-1319.[Abstract/Free Full Text]

5. Williams, D. L. & Cummings, D. E. (2005) Regulation of ghrelin in physiologic and pathophysiologic states. J. Nutr. 135:1320-1325.[Abstract/Free Full Text]

6. Geliebter, A., Gluck, M. E. & Hashim, S. A. (2005) Plasma ghrelin concentrations are lower in binge eating disorder. J. Nutr. 135:1326-1330.[Abstract/Free Full Text]

7. Kalra, S. P., Ueno, N. & Kalra, P. S. (2005) Stimulation of appetite by ghrelin is regulated by leptin restraint: Peripheral and central sites of action. J. Nutr. 135:1331-1335.[Abstract/Free Full Text]

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