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Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/23/2003 Publication Date: 7/23/2003 Citation: Ramsay, T.G. 2003. Porcine leptin inhibits lipogenesis in porcine adipocytes.Journal of Animal Science. 81(12):3008-3017. Interpretive Summary: Leptin is a hormone produced by adipose tissue that can affect feeding behavior, animal health and reproduction. Studies in rodents have demonstrated that leptin can reduce fat mass. This experiment was designed to determine if porcine leptin can alter lipid synthesis in the adipose tissue. The data in the present study indicate that leptin can directly inhibit lipogenesis in porcine adipocytes. These data also demonstrate leptin functions to promote the partitioning of energy away from lipid accretion within porcine adipose tissue, in part by reducing insulin- mediated stimulation of lipogenesis. This action of leptin may be useful in a pharmacological approach to reducing fat mass in swine. Technical Abstract: The present study examined whether or not porcine leptin can alter lipid synthesis in porcine adipocytes. Isolated cell cultures were prepared from the stromal vascular (SV) cell fraction of neonatal, porcine subcutaneous adipose tissue. Cultures were differentiated using 2.5% pig serum + 10 nM insulin + 100 nM hydrocortisone. After 7 days of lipid filling, cultures were washed and used for experiments. Acute experiments assessed U-14C- glucose metabolism in cultures exposed to porcine leptin (0 to 1000 ng/mL) for 4 h. Chronic experiments used cultures incubated with 0-1000 ng porcine leptin/ml for 44 h prior to measurements of U-14C-glucose metabolism. A third experiment determined if chronic leptin treatment alters insulin responsive glucose metabolism, by including 10 nM insulin with leptin containing incubations. Leptin had no acute effects on lipogenesis (p<0.05). Chronic exposure to leptin (100 ng/ml) reduced glucose oxidation (21%), total lipid synthesis (18%) and fatty acid synthesis (23%), (p<0.05). Insulin stimulated rates of glucose oxidation, total lipid synthesis and fatty acid synthesis (p<0.05). However, chronic exposure to 10 ng leptin/ml reduced the efficacy of 10 nM insulin by ~18- 46% (p<0.05). These data indicate that leptin promotes partitioning of energy away from lipid accretion within porcine adipose tissue by inhibiting glucose oxidation and lipogenesis indirectly, by reducing insulin-mediated stimulation of lipogenesis and by directly inhibiting fatty acid esterification. |
