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6-Ketocholestanol suppresses lipid accumulation by decreasing FASN gene expression through SREBP-dependent regulation in HepG2 cells.

ABSTRACT: Nuclear receptors, such as liver X receptors (LXRs) and sterol regulatory element-binding proteins (SREBPs), are key regulators of lipogenic genes, including fatty acid synthase (FASN). It has been reported that several oxycholesterols (OCs) act as LXR ligands; however, it is unclear whether all OC molecular species act as ligands. We previously demonstrated that the absorption rate of dietary 6-ketocholestanol (6-keto), an oxycholesterol, is the highest of all the OCs using thoracic lymph duct-cannulated rats. However, limited information is available about the physiological significance of 6-keto. In this study, we investigated whether treatment with 6-keto increases intracellular triacylglycerol (TAG) levels through up-regulation of lipogenic gene expression in HepG2 cells. 6-Keto treatment significantly reduced intracellular TAG levels through down-regulation of lipogenic genes including FASN. Although 6-keto significantly suppressed FASN gene promoter activities, the action was completely diminished when mutations were present in the SREBP promoter site. TO901317 (TO) significantly increased FASN gene promoter activities, whereas simultaneous treatment with TO and 6-keto significantly reduced this activity. We also compared the effects of several OCs that are oxidized at the carbon-6 and -7 in the B-ring of cholesterol on FASN gene promoter activities. Similar to 6-keto, 6?-OH and 6?-OH significantly reduced the activity of the FASN gene promoter, which suggests that oxidation of carbon-6 in the B-ring may play an important role in the reduction of FASN expression. Our results indicate that 6-keto suppresses lipid accumulation by decreasing FASN gene expression through SREBP-dependent regulation in HepG2 cells.

SUBMITTER: Shirouchi B

PROVIDER: S-EPMC7002641 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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6-Ketocholestanol suppresses lipid accumulation by decreasing FASN gene expression through SREBP-dependent regulation in HepG2 cells.

Shirouchi Bungo B Yanagi Shuhei S Okawa Chinami C Koga Maiko M Sato Masao M

Cytotechnology 20200113 1

Nuclear receptors, such as liver X receptors (LXRs) and sterol regulatory element-binding proteins (SREBPs), are key regulators of lipogenic genes, including fatty acid synthase (FASN). It has been reported that several oxycholesterols (OCs) act as LXR ligands; however, it is unclear whether all OC molecular species act as ligands. We previously demonstrated that the absorption rate of dietary 6-ketocholestanol (6-keto), an oxycholesterol, is the highest of all the OCs using thoracic lymph duct- ...[more]

PMID: 31933103

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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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6-Ketocholestanol suppresses lipid accumulation by decreasing FASN gene expression through SREBP-dependent regulation in HepG2 cells.

Publications

6-Ketocholestanol suppresses lipid accumulation by decreasing FASN gene expression through SREBP-dependent regulation in HepG2 cells.

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