Leptin administration to lactating rats is unable to induce changes in lipid metabolism in white adipose tissue or mammary gland

During lactation in the rat, despite hyperphagia, there are no changes in e ither the plasma levels or the gene expression of leptin. Removal of the li tter, however, results in an important increase in the circulating concentr ation of leptin. Administration of leptin to lactating rats resulted in no changes in the in vivo lipogenic rate and lipoprotein lipase (LPL) activity in either adipose tissue or mammary gland, although there was an increase in insulin levels as a consequence of leptin administration. Conversely, li tter removal resulted in an important decrease of LPL activity and lipogeni c rate in the mammary gland while an increase in these parameters took plac e in adipose tissue. It is concluded that leptin is not the signal responsi ble for the changes in lipid metabolism that take place both in adipose tis sue and mammary gland following litter removal. (C) 1999 Elsevier Science I reland Ltd. All rights reserved.