GROWTH HORMONE-STIMULATED HORMONE SENSITIVE LIPASE EXPRESSION IN RAINBOW TROUT LIVER IS MEDIATED BY ERK AND PKC
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1
North Dakota State University, Cell and Molecular Biology, United States
Growth hormone (GH) regulates several aspects of metabolism in vertebrates, including the mobilization of stored lipid. In this study, we used hepatocytes isolated from rainbow trout as a model system to elucidate the molecular signaling events that underlie GH-stimulated hepatic lipolysis. Fish were particularly advantageous for this study because their livers store significant amounts of lipid, and the lipolytic processes in their livers have been well characterized. Studies were conducted on hepatocytes isolated from fish fasted 1 week, a nutritional regime previously found to shift animals from an anabolic state to a catabolic state involving activation of lipolysis. GH-stimulated lipolysis was manifested by increased expression of the two hormone-sensitive lipase (HSL)-encoding mRNAs, HSL1 and HSL2. GH stimulated expression of HSL-encoding mRNAs in a time- and concentration-related manner. GH decreased activation of several signaling elements including JAK2 (Janus Kinase 2), STAT5 (signal transduction and activator of transcription 5), and Akt. By contrast, GH activated ERK (extracellular signal-regulated kinase) and PKC (protein kinase C). Inhibitors of JAK2, STAT5, and the PI3K (phosphatidylinositol 3-kinase)/Akt pathway had no effect on GH-stimulated HSL mRNA expression; whereas, inhibition of PLC (phospholipase C)/PKC and the ERK pathways diminished GH-stimulated HSL mRNA expression. These findings indicate that GH promotes expression of HSL1 and HSL2 by activating PKC and Erk and by deactivating JAK2, STAT5, Akt.
Acknowledgements
We would like to thank Elizabeth Ellens, Andrea Hanson, Jeffrey Kittilson, Elle Kvam, Lincoln Martin, Dillon Marquart, Lindsey Norbeck, and Chad Walock for their assistance. Prof. Akiyosi Takahasi and Dr. Shiunsuke Moriyama generously provided salmonid GH. Supported by NSF grant IOS 0920116 to M. A. Sheridan.
Keywords:
ERK,
Growth Hormone,
Hormone Sensitive Lipase,
Lipolysis,
PKC,
PLC,
rainbow trout,
Signal Transduction
Conference:
NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology, Ann Arbor, United States, 13 Jul - 16 Jul, 2011.
Presentation Type:
Poster
Topic:
Metabolism and feeding
Citation:
Bergan
HE and
Sheridan
MA
(2011). GROWTH HORMONE-STIMULATED HORMONE SENSITIVE LIPASE EXPRESSION IN RAINBOW TROUT LIVER IS MEDIATED BY ERK AND PKC.
Front. Endocrinol.
Conference Abstract:
NASCE 2011: The inaugural meeting of the North American Society for Comparative Endocrinology.
doi: 10.3389/conf.fendo.2011.04.00110
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Received:
19 Jul 2011;
Published Online:
09 Aug 2011.
*
Correspondence:
Dr. Mark A Sheridan, North Dakota State University, Cell and Molecular Biology, Fargo, North Dakota, 58108-6050, United States, mark.sheridan@ttu.edu