Submitted to: American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: May 31, 2004
Publication Date: June 1, 2004
Citation: Caperna, T.J., Shannon, A.E., Poch, S.M., Garrett, W.M., Richards, M.P. 2004. Hormonal regulation of leptin receptor expression in primary cultures of porcine hepatocytes [abstract]. Journal of Animal Science. 82(Suppl.1):200. Technical Abstract: Leptin, a polypeptide hormone primarily produced by fat cells, has been shown to regulate energy metabolism in monolayer cultures of rodent hepatocytes and hepatic tumor cell lines. However, in porcine hepatocytes, we and others have demonstrated that leptin plays a minimal role, if any, in cellular energetics. The goals of this study were to establish the presence of porcine hepatocyte leptin receptors, and to determine the influence of regulatory hormones on leptin receptor gene expression. Hepatocytes were prepared from 30-70 kg pigs and seeded into T-25 flasks coated with pig tail collagen. Monolayers were established in William's E medium containing fetal calf serum for one day and switched to serum-free medium with basal hormone conditions (1 ng/ml insulin and 10 nM dexamethasone) for an additional two days. For the final 24 hr, insulin or glucagon (100 ng/ml) were added in the presence or absence of 100 nM T3. RNA was extracted and quantitative RT-PCR was performed with primers specific for porcine long form and total leptin receptors. Leptin receptor expression was calculated relative to 18S rRNA expression. The expression of the long form of the leptin receptor was confirmed under basal conditions. Insulin, glucagon and recombinant human proteins at 100 ng/ml (ghrelin, GLP-1 and leptin) had no influence on leptin receptor expression, however, the addition of T3 was associated with a marked increase (P<0.001) in total and long forms of the leptin receptor, 1.6 and 2.3 fold, respectively. Despite the presence of up-regulated leptin receptor expression in T3-treated cells, addition of leptin to these cultures confirmed the lack of effect of leptin on glycogen turnover or glucagon-induced cAMP production. These data suggest that porcine hepatocytes are insensitive to leptin even when leptin receptor expression is enhanced by T3.