Research article

Leptin induces inflammation-related genes in RINm5F insulinoma cells

Paul Hekerman¹ , Julia Zeidler¹ , Stefanie Korfmacher¹ , Simone Bamberg-Lemper¹ , Holger Knobelspies¹ , Lennart Zabeau² , Jan Tavernier² and Walter Becker¹

¹  Institute of Pharmacology and Toxicology, Medical Faculty of the RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany

²  The Flanders Interuniversity Institute for Biotechnology, Department of Medical Protein Research (VIB9), Ghent University, Faculty of Medicine and Health Sciences, A. Baertsoenkaai 3, 9000 Ghent, Belgium

author email corresponding author email

BMC Molecular Biology 2007, 8:41doi:10.1186/1471-2199-8-41

Published:	23 May 2007

Abstract

Background

Leptin acts not only on hypothalamic centers to control food intake but has additional functions in peripheral tissues, e.g. inhibition of insulin secretion from pancreatic islets. The leptin receptor (LEPRb) is a class I cytokine receptor that mediates activation of STAT transcription factors. In this study, we characterise the regulation of inflammation-related genes by leptin in insulinoma cells and compare the effect of transcriptional regulation by leptin with that of other cytokines.

Results

We have used RINm5F insulinoma cells as a model system for a peripheral target cell of leptin. Six transcripts encoding inflammation-related proteins were found to be upregulated by activation of LEPRb, namely lipocalin-2, pancreatitis-associated protein, preprotachykinin-1, fibrinogen-β, tissue-type plasminogen activator (tPA) and manganese-dependent superoxide dismutase (MnSOD). Four of these transcripts (fibrinogen-β, lipocalin-2, tPA, MnSOD) were also induced by the proinflammatory cytokine interleukin-1β (IL-1β). Interferon-γ alone had no effect on the leptin-induced transcripts but enhanced the upregulation by IL-1β of lipocalin-2, tPA and MnSOD mRNA levels. Experiments with LEPRb point mutants revealed that the upregulation of the inflammation-related genes depended on the presence of tyrosine-1138 which mediates the activation of the transcription factors STAT1 and STAT3. Reporter gene assays showed that leptin induced the expression of preprotachykinin-1 and lipocalin-2 on the level of promoter regulation. Finally, leptin treatment increased caspase 3-like proteolytic activity in RINm5F cells.

Conclusion

The present data show that leptin induces a cytokine-like transcriptional response in RINm5F cells, consistent with the proposed function of leptin as a modulator of immune and inflammatory responses.