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Am J Physiol Regul Integr Comp Physiol (September 24, 2008). doi:10.1152/ajpregu.90546.2008
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Submitted on June 30, 2008
Revised on August 22, 2008
Accepted on September 19, 2008

Insulin regulates hepatic leptin receptor expression in early lactating dairy cows

Stephanie R Thorn1, Richard Alan Ehrhardt2, W. Ronald Butler2, Susan M Quirk, and Yves R. Boisclair2*

1 University of Colorado
2 Cornell University

* To whom correspondence should be addressed. E-mail: yrb1{at}cornell.edu.

Energy balance controls the expression of the leptin receptor (Lepr) in the ruminant hypothalamus but whether similar regulation occurs in peripheral tissues is unknown. To address this issue, we measured Lepr expression in the liver and adipose tissue of dairy cows during the transition from late pregnancy (LP) to early lactation (EL). This period is characterized by the development of a profound state of energy insufficiency and is associated with reduced plasma insulin and leptin and with increased plasma growth hormone. Hepatic expression of the short (Lepr-a) and long (Lepr-b) isoforms was 40% higher during EL (8 days postpartum) than LP (30 days prepartum). A similar effect was observed when negative energy balance was induced in non-pregnant, late lactation dairy cows by feed restriction, implicating energy insufficiency as a specific cause in EL. The stimulation of hepatic Lepr expression was reversed after a 48 h period of hyperinsulinemic euglycemia in EL. Changes in hepatic Lepr expression during chronic elevation of plasma leptin in EL or plasma growth hormone in non pregnant, late lactation cows did not support a role for these hormones in mediating the effects of energy insufficiency on hepatic Lepr expression. In adipose tissue, Lepr expression was increased 10-fold during the transition from LP to EL. Overall, these data indicate that hypoinsulinemia is partly responsible for the induction of Lepr expression in the liver, and perhaps adipose tissue, of energy-deficient dairy cows.







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