PMID:14677856

Citation	Ramsay, TG (2003) Porcine leptin inhibits lipogenesis in porcine adipocytes. J. Anim. Sci. 81:3008-17
Abstract	The present study examined whether recombinant porcine leptin alters lipid synthesis in porcine adipocytes. The stromal-vascular cell fraction of neonatal pig subcutaneous adipose tissue was isolated by collagenase digestion, filtration, and subsequent centrifugation. These cells were seeded on 25-cm2 tissue culture flasks and proliferated to confluency in 10% (vol/vol) fetal bovine serum in Dulbecco's modified Eagle medium/F12 (DMEM/F12, 50:50). Cultures were differentiated using 2.5% pig serum (vol/vol), 10 nM insulin, 100 nM hydrocortisone. After 7 d of lipid filling, cultures were washed free of this medium, incubated overnight in DMEM/F12 containing 2% pig serum (vol/vol), and then used for experiments. Acute experiments assessed U-(14)C-glucose or 1-(14)C-palmitate metabolism in cultures exposed to porcine leptin (0 to 1,000 ng/mL medium) for 4 h. Chronic experiments used cultures incubated with 0 to 1,000 ng porcine leptin/mL medium for 44 h before measurements of U-(14)C-glucose and 1-(14)C-palmitate oxidation and incorporation into lipid. Another experiment examined whether chronic leptin treatment alters insulin responsiveness by including insulin (10 nM) with incubations containing leptin. Leptin had no acute effects on glucose oxidation or conversion to lipid (P > 0.05). Acute leptin treatment decreased palmitate incorporation into lipids up to 45% (P < 0.05). Chronic leptin exposure decreased glucose oxidation (21%), total lipid synthesis (18%), and fatty acid synthesis (23%) at 100 ng/mL medium (P < 0.05). Insulin increased rates of glucose oxidation, total lipid, and fatty acid synthesis (P < 0.05); however, chronic exposure to 10 ng leptin/mL medium decreased the effectiveness of 10 nM insulin to affect these measures of glucose metabolism by approximately 18 to 46% (P < 0.05). Higher concentrations of leptin inhibited all effects of insulin on glucose metabolism (P < 0.05). Chronic exposure to leptin increased palmitate oxidation by 36% (P < 0.05). Chronic leptin exposure decreased palmitate incorporation into total lipids by 40% at 100 ng/mL medium (P < 0.05). Lipoprotein lipase activity was not affected (P > 0.05) by leptin. These data indicate that leptin functions to promote partitioning of energy away from lipid accretion within porcine adipose tissue by inhibiting glucose oxidation and lipogenesis indirectly, by decreasing insulin-mediated stimulation of lipogenesis, and by stimulating fatty acid oxidation while inhibiting fatty acid esterification.
Links	PubMed Online version:10.2527/2003.81123008x
Keywords	Adipocytes/drug effects; Adipocytes/metabolism; Adipose Tissue/cytology; Adipose Tissue/drug effects; Adipose Tissue/metabolism; Animals; Carbon Radioisotopes; Cells, Cultured; Culture Media; Dose-Response Relationship, Drug; Esterification/drug effects; Fatty Acids/metabolism; Glucose/metabolism; Insulin/metabolism; Insulin/pharmacology; Leptin/pharmacology; Lipids/biosynthesis; Lipolysis/drug effects; Lipolysis/physiology; Lipoprotein Lipase/metabolism; Oxidation-Reduction/drug effects; Random Allocation; Swine/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
PIG:LEP		GO:1900534: palmitic acid catabolic process	ECO:0000314:		P		Figure 4 shows that in pigs chronic exposure to porcine leptin increases the relative rate of palmitate oxidation. Submitting new go term request for 'Positive regulation of palmitic acid catabolic process'	complete CACAO 13427
PIG:LEP		GO:0046627: glucose catabolic process	ECO:0000314:		P		Figure 1 shows that acute treatment with porcine leptin reduced the rate of glucose oxidation in pig adipocyte cultures.	complete CACAO 13431
PIG:LEP		GO:0006007: glucose catabolic process	ECO:0000314:		P		Figure 2 shows that chronic treatment with porcine leptin reduced the rate of glucose oxidation in pig adipocyte containing cultures	complete CACAO 13436
PIG:LEP		GO:0051055: negative regulation of lipid biosynthetic process	ECO:0000314:		P		Figure 6 shows that chronic leptin treatment reduce the total glucose incorporation into lipids(lipid biosynthesis) vs controls in pig adipocyte containing cultures.	complete CACAO 13437
PIG:LEP		GO:1900533: palmitic acid metabolic process	ECO:0000314:		P		Figure 7 shows that acute treatment with porcine leptin caused a decrease in palmitate esterification in pig adipocyte-containing primary cultures.	complete CACAO 13438
PIG:LEP		GO:0045717: negative regulation of fatty acid biosynthetic process	ECO:0000314:		P		Figure 10 shows that chronic treatment with porcine leptin decreased fatty acid synthesis in a dose dependent manner in pig adipocyte containing primary cultures	complete CACAO 13439
PIG:INS		GO:0045723: positive regulation of fatty acid biosynthetic process	ECO:0000314:		P		Figure 9 shows that treatment with insulin caused an increase in fatty acid synthesis in pig adipocyte-containing primary cultures.	complete CACAO 13441
PIG:INS		GO:0046889: positive regulation of lipid biosynthetic process	ECO:0000314:		P		Figure 5 shows that insulin increased the glucose incorporation into lipid(lipid biosynthesis) vs controls in porcine(pig) adipocyte culture..	complete CACAO 13442
PIG:INS		GO:0051006: positive regulation of lipoprotein lipase activity	ECO:0000314:		P		Figure 11 shows that chronic exposure to insulin stimulated an increase lipoprotein lipase activity in Pig adipocyte containing primary cultures.	complete CACAO 13443
PIG:INS		GO:0010907: glucose catabolic process	ECO:0000314:		P		Figure 1 shows that insulin tended to increase glucose oxidation in pig adipocyte cultures. Requesting new term 'Positive regulation of glucose catabolic process'	complete CACAO 13468

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