Selenium-dependent glutathione peroxidase 1 regulates transcription of elongase 3 in murine tissues

We have previously shown dysregulated lipid metabolism in tissues of glutathione peroxidase 1 (GPX1) overexpressing (OE) or deficient (KO) mice. This study explored underlying mechanisms of GPX1 in regulating tissue fatty acid (FA) biosynthesis. GPX1 OE, KO, and wild-type (WT) mice (n = 5, male, 3-6 months old) were fed a Se-adequate diet (0.3 mg/kg) and assayed for liver and adipose tissue FA profiles and mRNA levels of key enzymes of FA biosynthesis and redox-responsive transcriptional factors (TFs). These three genotypes of mice (n = 5) were injected intraperitoneally with diquat, ebselen, and N-acetylcysteine (NAC) at 10, 50, and 50 mg/kg of body weight, respectively, and killed at 0 and 12 h after the injections to detect mRNA levels of FA elongases and desaturases and the TFs in the liver and adipose tissue. A luciferase reporter assay with targeted deletions of mouse Elovl3 promoter was performed to determine transcriptional regulations of the gene by GPX1 mimic ebselen in HEK293T cells. Compared with WT, GPX1 OE and KO mice had 9-42% lower (p < 0.05) and 36-161% higher (p < 0.05) concentrations of C20:0, C22:0, and C24:0 in these two tissues, respectively, along with reciprocal increases and decreases (p < 0.05) of Elovl3 transcripts. Ebselen and NAC decreased (p < 0.05), whereas diquat decreased (p < 0.05), Elovl3 transcripts in the two tissues. Overexpression and knockout of GPX1 decreased (p < 0.05) and increased (p < 0.05) ELOVL3 levels in the two tissues, respectively. Three TFs (GABP, SP1, and DBP) were identified to bind the Elovl3 promoter (-1164/+33 base pairs). Deletion of DBP (-98/-86 base pairs) binding domain in the promoter attenuated (13%, p < 0.05) inhibition of ebselen on Elovl3 promoter activation. In summary, GPX1 overexpression down-regulated very long-chain FA biosynthesis via transcriptional inhibition of the Elovl3 promoter activation.