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APPETITE, OBESITY AND METABOLISM

Effect of insulin and growth hormone on plasma leptin in periparturient dairy cows

¹School of Agriculture and Food Systems, Institute of Land and Food Resources, University of Melbourne, Victoria, Australia, 3010; and ²Department of Animal Science, Cornell University, Ithaca, New York 14853-4801

Submitted 11 June 2003 ; accepted in final form 22 July 2003

After parturition, dairy cows suffer from an intense energy deficit caused by the onset of copious milk secretion and an inadequate increase in voluntary food intake. We previously showed that this energy deficit contributes to a decline in plasma leptin. This decline mirrors that of plasma insulin but is reciprocal to the profile of plasma growth hormone (GH), suggesting that both hormones may regulate plasma leptin in periparturient dairy cows. To study the role of insulin, hyperinsulinemic-euglycemic clamps were performed on six dairy cows in late pregnancy (LP, 31 days prepartum) and early lactation (EL, 7 days postpartum). Infusion of insulin (1 µg·kg body wt^-1·h^-1) caused a progressive rise in the plasma concentration of leptin that reached maximum levels at 24 h during both physiological states. At steady states, the absolute increase in plasma leptin was greater in LP than in EL cows (2.4 vs. 0.4 ng/ml). Insulin infusion increased leptin mRNA in adipose tissue during LP but not during EL. During lactation, mammary epithelial cells expressed leptin mRNA but insulin did not increase milk leptin output. In contrast, a 3-day period of GH administration had no effect on plasma leptin during LP or EL. Therefore, insulin increases plasma leptin in LP by stimulating adipose tissue synthesis but has only marginal effects in EL, when cows are in negative energy balance. Other factors, such as increased response of adipose tissue to -adrenergic signals, probably contribute to the reduction of plasma leptin in early lactating dairy cows.

pregnancy; lactation; hyperinsulinemic-euglycemic clamp

This article has been cited by other articles:

				S. R. Thorn, S. Purup, W. S. Cohick, M. Vestergaard, K. Sejrsen, and Y. R. Boisclair Leptin Does Not Act Directly on Mammary Epithelial Cells in Prepubertal Dairy Heifers J Dairy Sci, May 1, 2006; 89(5): 1467 - 1477. [Abstract] [Full Text] [PDF]