Exp Clin Endocrinol Diabetes 2013; 121(08): 488-493
DOI: 10.1055/s-0033-1347266
Article
© J. A. Barth Verlag in Georg Thieme Verlag KG Stuttgart · New York

Thyroid-Stimulating Hormone Induces the Secretion of Tumor Necrosis Factor-α from 3T3-L1 Adipocytes via a Protein Kinase A-Dependent Pathway

Y.-J. Zhang*
1   2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, The Key Laboratory of Hormones and Development (Ministry of Health), Metabolic Diseases Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin, China
,
W. Zhao*
1   2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, The Key Laboratory of Hormones and Development (Ministry of Health), Metabolic Diseases Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin, China
,
M.-Y. Zhu
2   College of Basic Medicine, Tianjin Medical University, China
,
S.-S. Tang
1   2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, The Key Laboratory of Hormones and Development (Ministry of Health), Metabolic Diseases Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin, China
,
H. Zhang
1   2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, The Key Laboratory of Hormones and Development (Ministry of Health), Metabolic Diseases Hospital & Tianjin Institute of Endocrinology, Tianjin Medical University, Tianjin, China
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Publikationsverlauf

received 06. März 2013
first decision 28. April 2013

accepted 17. Mai 2013

Publikationsdatum:
17. Juli 2013 (online)

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Abstract

Objective:

Numerous reports have suggested that thyroid-stimulating hormone (TSH) contributes to insulin resistance in adipocytes by directly stimulating the production of adipokines, such as tumor necrosis factor α (TNF-α). The objective of this study was to clarify how TSH regulates TNF-α secretion in 3T3-L1 adipocytes and to determine which cell signaling pathways were involved.

Methods:

Mouse 3T3-L1 preadipocytes were differentiated into adipocytes and then exposed to 0.1 mIU/ml bovine TSH. The optimal treatment duration was determined by measuring the TNF-α concentration in the medium by ELISA. Thereafter, adipocytes were treated with 0.01, 0.1, and 1.0 mIU/ml bovine TSH, and the optimal TSH dose was determined. To decrease TSHR expression, TSHR shRNA was transfected into adipocytes, and the silencing was confirmed by Western blotting. The TSH signaling pathways responsible for regulating TNF-α secretion were studied. Phospho-NF-κBp65 Ser276 was quantified by Western blotting, and co-immunopreci­pitations were performed to detect the formation of the IκBα/PKAc complex.

Results:

TNF-α secretion from adipocytes peaked 4 h after TSH treatment. TSH induced TNF-α secretion in a dose-dependent manner, which was almost completely inhibited by TSHR shRNA. There was a significant positive correlation between phospho-NF-κBp65 Ser276 levels and TNF-α secretion. H89, a cAMP-dependent protein kinase A inhibitor, significantly inhibited the effects of TSH. Bovine TSH and forskolin, which increases intracellular cAMP, simultaneously stimulated TNF-α secretion. The IκBα/PKAc complex could be detected in TSH-treated cells, but complex formation was inhibited by H89.

Conclusion:

TSH stimulated the cAMP-PKA pathway in 3T3-L1 adipocytes to increase TNF-α secretion.

* Both authors contributed equally to this study