Horm Metab Res 2005; 37(9): 533-537
DOI: 10.1055/s-2005-870418
Review
© Georg Thieme Verlag KG Stuttgart · New York

Leptin TRH and Ghrelin: Influence on Energy Homeostasis at Rest and During Exercise

V.  Popovic1 , L.  H.  Duntas2
  • 1Neuroendocrine Unit, Institute of Endocrinology, University Clinical Center, Belgrade, Serbia
  • 2Endocrine Unit, Evgenidion Hospital, University of Athens Medical School, Athens, Greece
Further Information

Publication History

Received 16 February 2005

Accepted after Revision 21 April 2005

Publication Date:
20 September 2005 (online)

Abstract

The hypothalamus has long been recognized as a major site in the central nervous system (CNS) where a spectrum of internal and external environmental information is integrated for energy homeostasis. The isolation and sequencing of leptin in the mid 90 s, together with the demonstration of leptin administration’s ability to correct the obesity syndrome in leptin-deficient ob/ob mice and humans by suppressing food intake and weight gain in laboratory rodents, confirmed the hypothesized existence of a direct humoral signal from adipose tissue to the hypothalamus, thus integrating the energy-related signals. In the 80 s, neuropeptide Y (NPY) was identified as a potent appetite-stimulating neuropeptide produced, released and acting locally within the hypothalamus. This is recognized as a major physiological appetite transducer and central neurochemical substrate receiving, interpreting and processing incoming information on energy status. More recently, ghrelin, produced in the stomach and released into the general circulation, has drawn attention as the other limb of the feedback circuit that stimulates appetite at NPY network level. Prolonged fasting suppresses serum leptin, while suppressing TSH secretion. Intervention with leptin replacement can prevent fasting-induced changes in TSH, suggesting that leptin regulates TSH. Low leptin levels in sportsmen and sportswomen as well as in recreational runners are consistent with reduction in body fat, but are also influenced by the presence of low insulin, hypothyroxemia, and elevated cortisol levels. These metabolic adaptations to chronic energy deficits indicate a role in leptin regulation. A study within the general population found that activity levels and leptin were significantly negatively associated in both sexes. Circulating ghrelin levels, however, do not change during energy expenditure.

References

Prof. Dr. Vera Popovic M. D., Ph. D.

Neuroendocrine Unit · Institute of Endocrinology ·

University Clinical Center · Dr Subotic 13 · 11000 Belgrade · Serbia

Email: popver@eunet.yu