Circulating concentrations of leptin in sheep correlate with body fatness and are affected by level of food intake and photoperiod. The present objective was to elucidate the short-term dynamics of leptin secretion. Frequent blood samples were taken over 48 h from 12 Soay rams after 16 weeks in short-day photoperiod (SD, 16 h darkness:8 h light) with freely available food, and then after 16 weeks in long days (16 h light:8 h darkness) with food freely available (LD) or restricted to 90% maintenance (LDR) (n=6/group). During the second 24 h of sampling, half were food deprived (n=6, SD and LD) and half had their meal times shifted (n=6, SD and LDR). A homologous RIA was developed, using antibodies raised in chicken against recombinant ovine leptin, to measure plasma concentrations. Simultaneous 24 h profiles of plasma insulin, glucose and non-esterified fatty acids (NEFA) were measured. Plasma leptin was higher in LD than SD, and in LD than LDR, associated with higher food intake, liveweight and body condition score (adiposity), but tended to be lower in LDR than SD, associated with lower food intake, liveweight and body condition score. There was no evidence for a circadian rhythm of plasma leptin, but clear evidence for post-prandial peaks of low amplitude (15-36%) 2-8 h after meals given at normal and shifted times. Complete food deprivation caused a dramatic fall in plasma leptin to basal levels within 24 h. There was a positive association of plasma leptin with plasma insulin, and negative association with NEFA, both between meals and during fasting. Thus, plasma leptin concentrations in sheep are sensitive to short-term changes in energy balance, as well as to long-term photoperiod-driven changes in food intake and adiposity.

This article has been cited by other articles:

				K. Zaralis, B. J. Tolkamp, J. G. M. Houdijk, A. R. G. Wylie, and I. Kyriazakis Changes in food intake and circulating leptin due to gastrointestinal parasitism in lambs of two breeds J Anim Sci, August 1, 2008; 86(8): 1891 - 1903. [Abstract] [Full Text] [PDF]

				C Letelier, F Mallo, T Encinas, J M Ros, and A Gonzalez-Bulnes Glucogenic supply increases ovulation rate by modifying follicle recruitment and subsequent development of preovulatory follicles without effects on ghrelin secretion Reproduction, July 1, 2008; 136(1): 65 - 72. [Abstract] [Full Text] [PDF]

				D. W. Miller, J. L. Harrison, E. J. Bennett, P. A. Findlay, and C. L. Adam Nutritional Influences on Reproductive Neuroendocrine Output: Insulin, Leptin, and Orexigenic Neuropeptide Signaling in the Ovine Hypothalamus Endocrinology, November 1, 2007; 148(11): 5313 - 5322. [Abstract] [Full Text] [PDF]

				P. W. Franks, R. J. F. Loos, S. Brage, S. O'Rahilly, N. J. Wareham, and U. Ekelund Physical activity energy expenditure may mediate the relationship between plasma leptin levels and worsening insulin resistance independently of adiposity J Appl Physiol, May 1, 2007; 102(5): 1921 - 1926. [Abstract] [Full Text] [PDF]

				C. Anukulkitch, A. Rao, F. R. Dunshea, D. Blache, G. A. Lincoln, and I. J. Clarke Influence of photoperiod and gonadal status on food intake, adiposity, and gene expression of hypothalamic appetite regulators in a seasonal mammal Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2007; 292(1): R242 - R252. [Abstract] [Full Text] [PDF]

				C. L. Adam, P. A. Findlay, and D. W. Miller Blood-Brain Leptin Transport and Appetite and Reproductive Neuroendocrine Responses to Intracerebroventricular Leptin Injection in Sheep: Influence of Photoperiod Endocrinology, October 1, 2006; 147(10): 4589 - 4598. [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]

				J. M. Wallace, M. Matsuzaki, J. Milne, and R. Aitken Late but Not Early Gestational Maternal Growth Hormone Treatment Increases Fetal Adiposity in Overnourished Adolescent Sheep Biol Reprod, August 1, 2006; 75(2): 231 - 239. [Abstract] [Full Text] [PDF]

				M Munoz-Gutierrez, P A Findlay, C L Adam, G Wax, B K Campbell, N R Kendall, M Khalid, M Forsberg, and R J Scaramuzzi The ovarian expression of mRNAs for aromatase, IGF-I receptor, IGF-binding protein-2, -4 and -5, leptin and leptin receptor in cycling ewes after three days of leptin infusion Reproduction, December 1, 2005; 130(6): 869 - 881. [Abstract] [Full Text] [PDF]

				M. E. Gordon and K. H. McKeever Diurnal variation of ghrelin, leptin, and adiponectin in Standardbred mares J Anim Sci, October 1, 2005; 83(10): 2365 - 2371. [Abstract] [Full Text] [PDF]

				J. A. Cartmill, D. L. Thompson Jr., W. A. Storer, J. C. Crowley, N. K. Huff, and C. A. Waller Effect of dexamethasone, feeding time, and insulin infusion on leptin concentrations in stallions J Anim Sci, August 1, 2005; 83(8): 1875 - 1881. [Abstract] [Full Text] [PDF]

				Z A Archer, S M Rhind, P A Findlay, C E Kyle, M C Barber, and C L Adam Hypothalamic responses to peripheral glucose infusion in food-restricted sheep are influenced by photoperiod J. Endocrinol., March 1, 2005; 184(3): 515 - 525. [Abstract] [Full Text] [PDF]

				C Vinoles, M Forsberg, G B Martin, C Cajarville, J Repetto, and A Meikle Short-term nutritional supplementation of ewes in low body condition affects follicle development due to an increase in glucose and metabolic hormones Reproduction, March 1, 2005; 129(3): 299 - 309. [Abstract] [Full Text] [PDF]

				P. K. Chelikani, D. H. Keisler, and J. J. Kennelly Response of Plasma Leptin Concentration to Jugular Infusion of Glucose or Lipid Is Dependent on the Stage of Lactation of Holstein Cows J. Nutr., December 1, 2003; 133(12): 4163 - 4171. [Abstract] [Full Text] [PDF]

				S. S. Block, R. P. Rhoads, D. E. Bauman, R. A. Ehrhardt, M. A. McGuire, B. A. Crooker, J. M. Griinari, T. R. Mackle, W. J. Weber, M. E. Van Amburgh, et al. Demonstration of a Role for Insulin in the Regulation of Leptin in Lactating Dairy Cows J Dairy Sci, November 1, 2003; 86(11): 3508 - 3515. [Abstract] [Full Text] [PDF]

				I. J. Clarke, A. Rao, Y. Chilliard, C. Delavaud, and G. A. Lincoln Photoperiod effects on gene expression for hypothalamic appetite-regulating peptides and food intake in the ram Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2003; 284(1): R101 - R115. [Abstract] [Full Text] [PDF]

				X. Pan, T. Terada, M. Irie, H. Saito, and K.-I. Inui Diurnal rhythm of H+-peptide cotransporter in rat small intestine Am J Physiol Gastrointest Liver Physiol, July 1, 2002; 283(1): G57 - G64. [Abstract] [Full Text] [PDF]

				R. A. Ehrhardt, A. W. Bell, and Y. R. Boisclair Spatial and developmental regulation of leptin in fetal sheep Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2002; 282(6): R1628 - R1635. [Abstract] [Full Text] [PDF]

				A. Sorensen, C. L. Adam, P. A. Findlay, M. Marie, L. Thomas, M. T. Travers, and R. G. Vernon Leptin secretion and hypothalamic neuropeptide and receptor gene expression in sheep Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2002; 282(4): R1227 - R1235. [Abstract] [Full Text] [PDF]