Effects of recombinant ovine leptin on in vitro lipolysis and lipogenesis in subcutaneous adipose tissue from lactating and nonlactating sheep

Direct effects of recombinant ovine leptin on adipose metabolism in sheep w ere investigated. Lipolytic and lipogenic rates were assessed following pre incubation of subcutaneous adipose tissue explants with recombinant ovine l eptin. Leptin had no consistent effect on the basal (unstimulated) lipolyti c rate in adipose tissue from wethers. Lipolytic rate measured in the prese nce of combinations of adenosine deaminase, isoprenaline, and N-6-phcnyliso propyl adenosine was unaffected by pretreatment with leptin. In lactating e wes, there was no relationship between increasing concentrations of leptin and basal lipolytic rate. Leptin had no effect on basal (unstimulated) lipo genesis, or on insulin-stimulation or growth hormone inhibition of lipogene sis in adipose tissue from wethers. Lipogenesis in adipose tissue from lact ating ewes was also unaffected by preincubation with leptin; however, at su praphysiological concentrations of leptin, there was a small reduction in t he rate of insulin-stimulated lipogenesis. Leptin failed to induce phosphor ylation of the signal transducers and activators of transcription, STAT 3 a nd STAT 5, in sheep adipocytes. These results suggest that leptin does not have a direct physiological effect on subcutaneous adipose tissue metabolis m in sheep.