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Uncoupling lipid metabolism from inflammation through fatty acid binding protein-dependent expression of UCP2.

ABSTRACT: Chronic inflammation in obese adipose tissue is linked to endoplasmic reticulum (ER) stress and systemic insulin resistance. Targeted deletion of the murine fatty acid binding protein (FABP4/aP2) uncouples obesity from inflammation although the mechanism underlying this finding has remained enigmatic. Here, we show that inhibition or deletion of FABP4/aP2 in macrophages results in increased intracellular free fatty acids (FFAs) and elevated expression of uncoupling protein 2 (UCP2) without concomitant increases in UCP1 or UCP3. Silencing of UCP2 mRNA in FABP4/aP2-deficient macrophages negated the protective effect of FABP loss and increased ER stress in response to palmitate or lipopolysaccharide (LPS). Pharmacologic inhibition of FABP4/aP2 with the FABP inhibitor HTS01037 also upregulated UCP2 and reduced expression of BiP, CHOP, and XBP-1s. Expression of native FABP4/aP2 (but not the non-fatty acid binding mutant R126Q) into FABP4/aP2 null cells reduced UCP2 expression, suggesting that the FABP-FFA equilibrium controls UCP2 expression. FABP4/aP2-deficient macrophages are resistant to LPS-induced mitochondrial dysfunction and exhibit decreased mitochondrial protein carbonylation and UCP2-dependent reduction in intracellular reactive oxygen species. These data demonstrate that FABP4/aP2 directly regulates intracellular FFA levels and indirectly controls macrophage inflammation and ER stress by regulating the expression of UCP2.

SUBMITTER: Xu H

PROVIDER: S-EPMC4333098 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Uncoupling lipid metabolism from inflammation through fatty acid binding protein-dependent expression of UCP2.

Xu Hongliang H Hertzel Ann V AV Steen Kaylee A KA Wang Qigui Q Suttles Jill J Bernlohr David A DA

Molecular and cellular biology 20150112 6

Chronic inflammation in obese adipose tissue is linked to endoplasmic reticulum (ER) stress and systemic insulin resistance. Targeted deletion of the murine fatty acid binding protein (FABP4/aP2) uncouples obesity from inflammation although the mechanism underlying this finding has remained enigmatic. Here, we show that inhibition or deletion of FABP4/aP2 in macrophages results in increased intracellular free fatty acids (FFAs) and elevated expression of uncoupling protein 2 (UCP2) without conco ...[more]

PMID: 25582199

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Project description:Methods: We performed mRNA sequence analysis by deep sequencing, in triplicate, using Illumina HiSeq to assess the impact of PHLPP1 knockdown in regulating gene expression in RAW 264.7 cells treated with/without OxLDL. The transcriptome libraries were constructed using the NEB adapters and were sequenced on at 150 nucleotide read length using the paired-end chemistry. The raw reads were subjected to Adapter and low-quality reads removal by Trimmomatic -0.36v. The raw reads were subjected to contamination [structural RNA / low complexity sequences] removal by mapping with bowtie 2-2.2.1. The decontaminated data set was mapped to the mouse genome. Reads mapping to gene list were counted using feature count module of sub reads package. The read counts were normalized in DESeq2-3.5, and subject to differential expression analysis. Differentially expressed genes were selected based on log2-ratio change with p-value <0.05 (Student’s t-test, unpaired). Hierarchical clustering was performed with the programs Cluster (uncentered correlation; average linkage clustering) and Treeview. Results: To gain a deeper understanding of the role of PHLPP1 in lipid metabolism in macrophages, we performed mRNA Seq analysis to assess the gene expression changes in a mouse macrophage cell line. The experiment has been carried out in triplicates. Alignment of the reads showed 97% alignment to the reference mouse genome. Identification of the differentially expressed genes were then carried out by DESeq2 version 1.2.10 with stringent criteria (FDR <0.05% with 2 fold up and down regulation) which reveals in control treated vs. control (121-down, 396-Up), Test vs. Control - (326-down, 569 Up) and Test treated vs. control treated (1314-down, 1328 up) of DEG to be altered in expression respectively. Inference: RNA-seq analysis revealed that PHLPP1 knockdown parallel with OxLDL treatment resulted in diminished expression profile of cholesterol biosynthesis and lipid metabolism genes.

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Uncoupling lipid metabolism from inflammation through fatty acid binding protein-dependent expression of UCP2.

Publications

Uncoupling lipid metabolism from inflammation through fatty acid binding protein-dependent expression of UCP2.

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