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

ABSTRACT: Background:The transcriptional factor peroxisome proliferator-activated receptor ? (PPAR?) is an important therapeutic target for the treatment of type 2 diabetes. However, the role of the PPAR? transcriptional activity remains ambiguous in its metabolic regulation. Methods:Based on the crystal structure of PPAR? bound with the DNA target of PPAR? response element (PPRE), Arg134, Arg135, and Arg138, three crucial DNA binding sites for PPAR?, were mutated to alanine (3RA), respectively. In vitro AlphaScreen assay and cell-based reporter assay validated that PPAR? 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 PPAR?-3RA (PPAR?3RA/+). The phenotypes of chow diet and high-fat diet fed PPAR?3RA/+ mice were investigated, and the molecular mechanism were analyzed by assessing the PPAR? transcriptional activity. Results:Homozygous PPAR?-3RA mutant mice are embryonically lethal. The mRNA levels of PPAR? target genes were significantly decreased in PPAR?3RA/+ mice. PPAR?3RA/+ 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 PPAR? was restored by rosiglitazone, a PPAR? agonist. Conclusion:The current report presents a novel mouse model for investigating the role of PPAR? transcription in physiological functions. The data demonstrate that the transcriptional activity plays an indispensable role for PPAR? in metabolic regulation.

SUBMITTER: Guo F

PROVIDER: S-EPMC7466717 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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

Guo Fusheng F Xu Shuangshuang S Zhu Yanlin Y Zheng Xing X Lu Yi Y Tu Jui J He Ying Y Jin Lihua L Li Yong Y

Frontiers in pharmacology 20200819

<h4>Background</h4>The 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.<h4>Methods</h4>Based 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), respecti ...[more]

PMID: 32973516

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Project description:ObjectiveAdipose tissue relies on lipid droplet (LD) proteins in its role as a lipid-storing endocrine organ that controls whole body metabolism. Hypoxia-inducible Gene 2 (Hig2) is a recently identified LD-associated protein in hepatocytes that promotes hepatic lipid storage, but its role in the adipocyte had not been investigated. Here we tested the hypothesis that Hig2 localization to LDs in adipocytes promotes adipose tissue lipid deposition and systemic glucose homeostasis.MethodWhite and brown adipocyte-deficient (Hig2fl/fl × Adiponection cre+) and selective brown/beige adipocyte-deficient (Hig2fl/fl × Ucp1 cre+) mice were generated to investigate the role of Hig2 in adipose depots. Additionally, we used multiple housing temperatures to investigate the role of active brown/beige adipocytes in this process.ResultsHig2 localized to LDs in SGBS cells, a human adipocyte cell strain. Mice with adipocyte-specific Hig2 deficiency in all adipose depots demonstrated reduced visceral adipose tissue weight and increased glucose tolerance. This metabolic effect could be attributed to brown/beige adipocyte-specific Hig2 deficiency since Hig2fl/fl × Ucp1 cre+ mice displayed the same phenotype. Furthermore, when adipocyte-deficient Hig2 mice were moved to thermoneutral conditions in which non-shivering thermogenesis is deactivated, these improvements were abrogated and glucose intolerance ensued. Adipocyte-specific Hig2 deficient animals displayed no detectable changes in adipocyte lipolysis or energy expenditure, suggesting that Hig2 may not mediate these metabolic effects by restraining lipolysis in adipocytes.ConclusionsWe conclude that Hig2 localizes to LDs in adipocytes, promoting adipose tissue lipid deposition and that its selective deficiency in active brown/beige adipose tissue mediates improved glucose tolerance at 23 °C. Reversal of this phenotype at thermoneutrality in the absence of detectable changes in energy expenditure, adipose mass, or liver triglyceride suggests that Hig2 deficiency triggers a deleterious endocrine or neuroendocrine pathway emanating from brown/beige fat cells.

Dataset Information

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

Publications

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

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