IGF-I mediated inhibition of leptin receptor expression in porcine hepatocytes.
A study was conducted to elucidate hormonal control of leptin receptor gene expression in primary cultures of porcine hepatocytes. Hepatocytes were isolated from swine and seeded into T-25 flasks. Cultures were established in medium containing fetal bovine serum for one day and switched to serum-free medium (William's E medium and 1 ng/mL insulin) for the remainder of the 3d culture period. For the final 24 h, medium was supplemented with porcine growth hormone (GH, 100 or 500 ng/mL), insulin-like growth factor 1 (IGF-1, 50 to 250 ng/mL) or triiodothyronine (T3, 100 ng/mL). RNA was extracted and relative quantitative RT-PCR was performed with primers for long form leptin receptor. Receptor expression was calculated relative to 18S rRNA. Insulin had no effect (P>0.05), while T3 increased leptin receptor mRNA abundance (P<0.05). Treatment with GH or IGF-I reduced leptin receptor expression (P<0.05). Phosphorylation of ERK1/2 in response to acute leptin treatment was inhibited by previous exposure to GH or IGF-I. Hepatocytes secreted IGF-I under basal conditions and this was enhanced by GH addition. These data suggest porcine hepatocytes may be less sensitive to leptin stimulation due to the actions of endogenous IGF-I on leptin receptor expression.
Animal Biosciences and Biotechnology Laboratory, Animal and Natural Resources Institute, USDA/ARS, Beltsville Agricultural Research Center, USDA, Beltsville, MD 20705, USA. timothy.ramsay@ars.usda.gov
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Ramsay
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Richards
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Li
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Caperna
D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D013006:Growth Hormone / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D020738:Leptin / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D054411:Receptors, Leptin / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D034421:Sus scrofa; D014284:Triiodothyronine / Q000494:pharmacology
D017077:Culture Media, Conditioned; D020738:Leptin; D012333:RNA, Messenger; D054411:Receptors, Leptin; D014284:Triiodothyronine; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3