| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
ANIMAL GROWTH, PHYSIOLOGY, AND REPRODUCTION |
* Departments of Animal Sciences and
and
Biomedical Sciences and Veterinary Medicine and Surgery, University of Missouri, Columbia 65211; and
and
Pennington Biomedical Research Center, Baton Rouge, LA 70817
2 Correspondence: 160 Anim. Sci. Res. Center (phone: 573-882-7267; fax: 573-882-6827; e-mail: keislerd{at}missouri.edu).
Leptin is a protein hormone produced by adipose tissue that influences hypothalamic mechanisms regulating appetite and energy balance. In species tested thus far, including horses, concentrations of leptin increase as animal fat mass increases. The variables and mechanisms that influence the secretion of leptin are not well known, nor is it known in equine species how the secretion of leptin is influenced by acute alterations in energy balance, circadian patterns, and/or reproductive competence. Our objectives were to determine in horses: 1) whether plasma concentrations of leptin are secreted in a circadian and/or a pulsatile pattern; 2) whether a 48-h period of feed restriction would alter plasma concentrations of leptin, growth hormone, or insulin; and 3) whether ovariectomy and/or a melatonin implant would affect leptin. In Exp. 1, mares exposed to ambient photoperiod of visible light (11 h, 33 min to 11 h, 38 min), received treatments consisting of a 48-h feed restriction (RES) or 48 h of alfalfa hay fed ad libitum (FED). Mares were maintained in a dry lot before sampling and were tethered to a rail during sampling. Analyses revealed that leptin was not secreted in a pulsatile manner, and that mean leptin concentrations were greater (P < 0.001) in FED vs. RES mares (17.20 ± 0.41 vs. 7.29 ± 0.41 ng/mL). Plasma growth hormone was pulsatile, and mean concentrations were greater in RES than FED mares (2.15 ± 0.31 vs. 1.08 ± 0.31 ng/mL; P = 0.05). Circadian patterns of leptin secretion were observed, but only in FED mares (15.39 ± 0.58 ng/mL for morning vs. 19.00 ± 0.58 ng/mL for evening; P < 0.001). In Exp. 2, mares that were ovariectomized or intact received either a s.c. melatonin implant or a sham implant. Thereafter, blood was sampled at weekly intervals at 1000 and 1700. Concentrations of leptin in samples collected at 1700 were greater (P < 0.001) than in those collected at 1000 (28.24 ± 1.7 vs. 22.07 ± 1.7 ng/mL). Neither ovariectomy nor chronic treatment with melatonin affected plasma concentrations of leptin or the circadian pattern of secretion. These data provide evidence that plasma leptin concentrations in the equine are sensitive to acute changes in nutritional status and vary in a circadian pattern that is sensitive to fasting but not to melatonin treatment or ovariectomy.
Key Words: Equine • Feed Deprivation • Leptin • Melatonin
This article has been cited by other articles:
|
|
 |
|
  W. A. Storer, D. L. Thompson Jr., C. A. Waller, and J. A. Cartmill Hormonal patterns in normal and hyperleptinemic mares in response to three common feeding-housing regimens J Anim Sci, November 1, 2007; 85(11): 2873 - 2881. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. L. Berg, D. L. McNamara, and D. H. Keisler Endocrine profiles of periparturient mares and their foals J Anim Sci, July 1, 2007; 85(7): 1660 - 1668. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. R Buff, N. T Messer IV, A. M Cogswell, D. A Wilson, P. J Johnson, D. H Keisler, and V. K Ganjam Induction of pulsatile secretion of leptin in horses following thyroidectomy J. Endocrinol., February 1, 2007; 192(2): 353 - 359. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. R. Buff, B. R. Spader, C. D. Morrison, and D. H. Keisler Endocrine responses in mares undergoing abrupt changes in nutritional management J Anim Sci, October 1, 2006; 84(10): 2700 - 2707. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. M. Steelman, E. M. Michael-Eller, P. G. Gibbs, and G. D. Potter Meal size and feeding frequency influence serum leptin concentration in yearling horses J Anim Sci, September 1, 2006; 84(9): 2391 - 2398. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. C. Whitley, E. L. Walker, S. A. Harley, D. H. Keisler, and D. J. Jackson Correlation between blood and milk serum leptin in goats and growth of their offspring J Anim Sci, August 1, 2005; 83(8): 1854 - 1859. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
