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HIF1α/TET1 Pathway Mediates Hypoxia-Induced Adipocytokine Promoter Hypomethylation in Human Adipocytes

1
Department of Physical Therapy and Integrative Physiology Laboratory, College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
2
Department of Physical Therapy and Integrative Physiology Laboratory, College of Applied Health Sciences and Division of Endocrinology, Diabetes, and Metabolism, University of Illinois at Chicago, Chicago, IL 60612, USA
3
Department of Medicine, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
*
Author to whom correspondence should be addressed.
Cells 2020, 9(1), 134; https://doi.org/10.3390/cells9010134
Received: 23 November 2019 / Revised: 28 December 2019 / Accepted: 3 January 2020 / Published: 6 January 2020
Obesity is associated with the accumulation of dysfunctional adipose tissue that secretes several pro-inflammatory cytokines (adipocytokines). Recent studies have presented evidence that adipose tissues in obese individuals and animal models are hypoxic, which may result in upregulation and stabilization of the hypoxia inducible factor HIF1α. Epigenetic mechanisms such as DNA methylation enable the body to respond to microenvironmental changes such as hypoxia and may represent a mechanistic link between obesity-associated hypoxia and upregulated inflammatory adipocytokines. The purpose of this study was to investigate the role of hypoxia in modifying adipocytokine DNA methylation and subsequently adipocytokine expression. We suggested that this mechanism is mediated via the DNA demethylase, ten-eleven translocation-1 (TET1), transcription of which has been shown to be induced by HIF1α. To this end, we studied the effect of hypoxia (2% O2) in differentiated subcutaneous human adipocytes in the presence or absence of HIF1α stabilizer (Dimethyloxalylglycine (DMOG), 500 μM), HIF1α inhibitor (methyl 3-[[2-[4-(2-adamantyl) phenoxy] acetyl] amino]-4-hydroxybenzoate, 30 μM), or TET1-specific siRNA. Subjecting the adipocytes to hypoxia significantly induced HIF1α and TET1 protein levels. Moreover, hypoxia induced global hydroxymethylation, reduced adipocytokine DNA promoter methylation, and induced adipocytokine expression. These effects were abolished by either HIF1α inhibitor or TET1 gene silencing. The major hypoxia-responsive adipocytokines were leptin, interleukin-1 (IL6), IL1β, tumor necrosis factor α (TNFα), and interferon γ (IFNγ). Overall, these data demonstrate an activation of the hydroxymethylation pathway mediated by TET1. This pathway contributes to promoter hypomethylation and gene upregulation of the inflammatory adipocytokines in adipocytes in response to hypoxia. View Full-Text
Keywords: adipocytes; hypoxia; inflammation; DNA methylation; HIF1α; TET1; adipocytokines; epigenetics adipocytes; hypoxia; inflammation; DNA methylation; HIF1α; TET1; adipocytokines; epigenetics
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Ali, M.M.; Phillips, S.A.; Mahmoud, A.M. HIF1α/TET1 Pathway Mediates Hypoxia-Induced Adipocytokine Promoter Hypomethylation in Human Adipocytes. Cells 2020, 9, 134.

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