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Insulin regulates hypoxia-inducible factor-1α transcription by reactive oxygen species sensitive activation of Sp1 in 3T3-L1 preadipocyte.

ABSTRACT: Oxygen sensing transcription factor HIF-1 is activated due to accumulation of regulatory subunit HIF-1α by posttranslational stability mechanism during hypoxia or by several other stimuli even in normoxia. HIF-1α is also regulated by NF-kB mediated transcription mechanism. Reactive oxygen species (ROS) act as an important regulator of HIF-1 either by affecting prolyl hydroxylase activity, the critical determinant of HIF-1α stabilization or by activating NF-kB to promote HIF-1α transcription. Insulin is known to activate HIF-1 by a ROS dependent mechanism but the molecular mechanism of HIF-1α regulation is not known so far. Here we show that insulin regulates HIF-1α by a novel transcriptional mechanism by a ROS-sensitive activation of Sp1 in 3T3-L1 preadipocyte. Insulin shows little effect on HIF-1α protein stability, but increases HIF-1α promoter activity. Mutation analyses, electrophoretic mobility shift assay and chromatin immunoprecipitation assay confirm the role of Sp1 in HIF-1α transcription. We further demonstrate that insulin-induced ROS generation initiates signaling pathway involving phosphatidylinositol 3-kinase and protein kinase C for Sp1 mediated HIF-1α transcription. In summary, we reveal that insulin regulates HIF-1α by a novel transcriptional mechanism involving Sp1.

SUBMITTER: Biswas S

PROVIDER: S-EPMC3633924 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Insulin regulates hypoxia-inducible factor-1α transcription by reactive oxygen species sensitive activation of Sp1 in 3T3-L1 preadipocyte.

Biswas Sudipta S Mukherjee Reshmi R Tapryal Nisha N Singh Amit K AK Mukhopadhyay Chinmay K CK

PloS one 20130423 4

Oxygen sensing transcription factor HIF-1 is activated due to accumulation of regulatory subunit HIF-1α by posttranslational stability mechanism during hypoxia or by several other stimuli even in normoxia. HIF-1α is also regulated by NF-kB mediated transcription mechanism. Reactive oxygen species (ROS) act as an important regulator of HIF-1 either by affecting prolyl hydroxylase activity, the critical determinant of HIF-1α stabilization or by activating NF-kB to promote HIF-1α transcription. Ins ...[more]

PMID: 23626778

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Project description:Since obesity causes at least 2.8 million death each year and is a major risk factor for many diseases, it is critical to evaluate alternative treatment approaches. In this context, studies on the research of natural product-based therapeutics in the fight against obesity are increasing. In this study, it was aimed to evaluate the antiadipogenic and antiobesogenic efficacy of pterostilbene a natural phenolic compound in 3T3-L1 cells. The mature 3T3-L1 adipocytes were exposed to pterostilbene at different concentrations and half-maximum inhibitory concentrations (IC50) were determined by MTT assay. Oil-Red-O staining was applied to determine lipid accumulation. Phase contrast microscopy, Giemsa, F-actin and DAPI staining were applied to examine the efficacy of pterostilbene on the morphology of 3T3-L1 adipocyte cells. Moreover, expressions of adinopectin and glucose transporter-4 (Glut-4) in relation to insulin resistance were evaluated using immunofluorescent staining and qRT-PCR. Pterostilbene caused no significant cytotoxicity towards preadipocytes at concentrations ≤7.5 -M and the percentage of viable cells remained above about 86% for 24 h, 48 h and 72 h (p > 0.05). Therefore, pterostilbene treatment at 5 and 7.5 -M was used in the subsequent experiments as safe dosages. In addition, it was observed that pterostilbene treatment reduced lipid accumulation in adipocyte differentiation. Adipocytes treated with a dose of 7.5 -M for 14 days showed less intense lipid deposition and a more spindle-like morphology compared to the adipocytes treated with a dose of 5 -M. Especially on the 14th day, actin filaments were filamentous in adipocytes treated with pterostilbene 7.5 -M compared to the adipocytes treated with a dose of 5 -M; the filaments were similarly oriented as in preadipocytes, and chromatin condensation was observed to be quite high. Our data suggests that the pterostilbene supplementation may help weight control and the antiadipogenic and that antiobesogenic activity is mediated in part by reduction of lipid accumulation and induction of Glut-4 and Adiponectin levels.

Dataset Information

Insulin regulates hypoxia-inducible factor-1α transcription by reactive oxygen species sensitive activation of Sp1 in 3T3-L1 preadipocyte.

Publications

Insulin regulates hypoxia-inducible factor-1α transcription by reactive oxygen species sensitive activation of Sp1 in 3T3-L1 preadipocyte.

Similar Datasets

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