PPARγ Transcription Deficiency Exacerbates High-Fat Diet-Induced Adipocyte Hypertrophy and Insulin Resistance in Mice.

Shuangshuang Xu,Lihua Jin,Xing Zheng,Fusheng Guo,Yanlin Zhu,Yong Li,Ying He,Jui Tu,Yi Lu

doi:10.3389/fphar.2020.01285

Shuangshuang Xu, Lihua Jin + Show 7 more

Open Access

https://doi.org/10.3389/fphar.2020.01285

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Abstract

BackgroundThe transcriptional factor peroxisome proliferator–activated receptor γ (PPARγ) is an important therapeutic target for the treatment of type 2 diabetes. However, the role of the PPARγ transcriptional activity remains ambiguous in its metabolic regulation.MethodsBased on the crystal structure of PPARγ bound with the DNA target of PPARγ response element (PPRE), Arg134, Arg135, and Arg138, three crucial DNA binding sites for PPARγ, were mutated to alanine (3RA), respectively. In vitro AlphaScreen assay and cell-based reporter assay validated that PPARγ 3RA mutant cannot bind with PPRE and lost transcriptional activity, while can still bind ligand (rosiglitazone) and cofactors (SRC1, SRC2, and NCoR). By using CRISPR/Cas9, we created mice that were heterozygous for PPARγ-3RA (PPARγ3RA/+). The phenotypes of chow diet and high-fat diet fed PPARγ3RA/+ mice were investigated, and the molecular mechanism were analyzed by assessing the PPARγ transcriptional activity.ResultsHomozygous PPARγ-3RA mutant mice are embryonically lethal. The mRNA levels of PPARγ target genes were significantly decreased in PPARγ3RA/+ mice. PPARγ3RA/+ mice showed more severe adipocyte hypertrophy, insulin resistance, and hepatic steatosis than wild type mice when fed with high-fat diet. These phenotypes were ameliorated after the transcription activity of PPARγ was restored by rosiglitazone, a PPARγ agonist.ConclusionThe current report presents a novel mouse model for investigating the role of PPARγ transcription in physiological functions. The data demonstrate that the transcriptional activity plays an indispensable role for PPARγ in metabolic regulation.

Highlights

Obesity is a growing worldwide risk factor for many complications in health, such as type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD) (Wild et al, 2004; Golay and Ybarra, 2005; Esser et al, 2014; Byrne and Targher, 2015)
Upon the binding with ligands by its LBD, peroxisome proliferator–activated receptor g (PPARg) locates to the specific Peroxisome proliferator-activated receptors (PPARs) response element (PPRE) via its DBD as a heterodimer with retinoid X receptor (RXR), and recruits cofactors to regulate the transcription of many direct downstream target genes (Larsen et al, 2003; Jin and Li, 2010; Seale, 2010; Ahmadian et al, 2013)
Based on the crystal structure of the PPARg–RXRa complex bound to PPRE (Chandra et al, 2008), we found that the Arg134, Arg135, and Arg138 residues in PPARg form six hydrogen bonds in the major groove of the PPRE double helix (Figures 1A–C)

Summary

Introduction

Obesity is a growing worldwide risk factor for many complications in health, such as type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD) (Wild et al, 2004; Golay and Ybarra, 2005; Esser et al, 2014; Byrne and Targher, 2015). Upon the binding with ligands by its LBD, PPARg locates to the specific PPAR response element (PPRE) via its DBD as a heterodimer with retinoid X receptor (RXR), and recruits cofactors to regulate the transcription of many direct downstream target genes (Larsen et al, 2003; Jin and Li, 2010; Seale, 2010; Ahmadian et al, 2013). The role of the PPARg transcriptional activity remains ambiguous in its metabolic regulation

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Conclusion