HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Block, S. S. Articles by Boisclair, Y. R. Search for Related Content PubMed PubMed Citation Articles by Block, S. S. Articles by Boisclair, Y. R.

Demonstration of a Role for Insulin in the Regulation of Leptin in Lactating Dairy Cows¹

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^* and Y. R. Boisclair^*

^* Department of Animal Science, Cornell University, Ithaca, NY 14853
University of Minnesota, St. Paul 55108

Corresponding author: Y. R. Boisclair; e-mail: yrb1{at}cornell.edu.

In lactating dairy cows, the onset of negative net energy balance (EB) at parturition causes a reduction in plasma leptin and is also associated with increased concentration of growth hormone (GH) and decreased concentration of insulin. These observations raise the possibility that opposite changes in plasma insulin and GH are partly responsible for reduced plasma leptin. To test this hypothesis, we first examined the effects of undernutrition without the confounding influence of parturition by using late lactating dairy cows fed 120% of their nutrient requirements or restricted to 33% of maintenance requirements. Plasma leptin was reduced within 24 h of feed restriction, and was associated with increased plasma GH and decreased plasma insulin. Complete food deprivation for 48 h caused similar changes in the plasma concentration of leptin. To determine if an elevation in GH is responsible for the fall in plasma leptin, dairy cows were treated with excipient or bovine somatotropin in early lactation or in late lactation. Growth hormone treatment had no significant effect on plasma leptin irrespective of stage of lactation. Finally, the effects of insulin were studied by performing euglycemic hyperinsulinemic clamps in mid-lactating dairy cows. After 96 h of hyperinsulinemia, plasma leptin was increased significantly. These data indicate that insulin regulates plasma leptin in lactating dairy cows. They also suggest that, in undernourished lactating dairy cows, reduced plasma insulin could account for a portion of the decline in plasma leptin but that elevated plasma GH is unlikely to have a major effect.

Key Words: leptin • insulin • GH • lactation • undernutrition

Abbreviation key: AGRP = agouti-related peptide, BCAA = branched chain amino acids, EB = energy balance, GH = growth hormone, NPY = neuropeptide Y, POMC = proopiomelanocortin, RIA = radioimmunoassay, WAT = white adipose tissue

This article has been cited by other articles:

				D. B. Carlson, N. B. Litherland, H. M. Dann, J. C. Woodworth, and J. K. Drackley Metabolic Effects of Abomasal L-Carnitine Infusion and Feed Restriction in Lactating Holstein Cows J Dairy Sci, December 1, 2006; 89(12): 4819 - 4834. [Abstract] [Full Text] [PDF]

				J. R. Roche, E. S. Kolver, and J. K. Kay Influence of Precalving Feed Allowance on Periparturient Metabolic and Hormonal Responses and Milk Production in Grazing Dairy Cows J Dairy Sci, February 1, 2005; 88(2): 677 - 689. [Abstract] [Full Text] [PDF]