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  • Title: IGF-I mediated inhibition of leptin receptor expression in porcine hepatocytes.
    Author: Ramsay TG, Richards MP, Li CJ, Caperna TJ.
    Journal: Comp Biochem Physiol B Biochem Mol Biol; 2010 Jan; 155(1):43-8. PubMed ID: 19786114.
    Abstract:
    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.
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