Interestingly, mRNA levels of Fsp27 in ob/ob hepatocytes and AML12 cells were not affected by FA treatment, but were significantly enhanced by PPAR agonists (Fig. 5A,B). Cideb expression was not affected by treatment with FAs or PPAR agonists (Supporting Fig. 6A,B). In addition, the expression level of Cidea (but not Fsp27 and Cideb) was up-regulated in the primary hepatocytes that were isolated from mice treated with an HFD for 2 days and incubated with saturated FAs (Fig. 5C and Supporting Fig. 6C). Consistent with increased gene expression, Cidea protein levels were higher in ob/ob hepatocytes treated with saturated FAs relative to the control cells (Fig. 5D and Supporting Fig. 6D). Fsp27
protein levels were also increased in cells treated with PPAR agonists (Fig. RG7420 price 5D and Supporting Fig. 6E). Interestingly, despite no effects on inducing Cidea mRNA level, OAs, LAs, and LNAs were able to increase Cidea and Fsp27 protein levels (Fig. 5D and Supporting Fig. 6D,E), suggesting a post-transcriptional regulation of Cidea and Fsp27 by these FAs.
find more Overall, these data indicated that gene expression of the CIDE family members was differentially regulated by dietary FAs and PPAR agonists, and that Cidea expression was specifically induced by saturated FAs. To identify the transcription factor(s) responsible for saturated FA-induced Cidea expression in hepatocytes, we checked expression levels of several key transcriptional regulators in livers of HFD-fed mice. We observed that levels of hepatic SREBP1c mRNA and its downstream target genes (i.e., FAS and ACC1) were increased in animals fed with HFDs for 2 days and continued to increase with HFD treatment (Fig. 6A
and Supporting Fig. 7A), which correlated well with the increased Cidea expression. In addition, protein levels of the mature nuclear form of SREBP1c were significantly increased in livers 上海皓元医药股份有限公司 of HFD-fed mice (Fig. 6A and Supporting Fig. 7C). mRNA levels and its nuclear form of SREBP1c were also increased in ob/ob hepatocytes treated with PAs and SAs (Fig. 6B and Supporting Fig. 7D). Hepatic expression of other transcriptional regulators, including SREBP2, PPARα, and liver X receptor alpha, were not affected by HFD treatment (Supporting Fig. 7B). The strong correlation between expression levels of SREBP1c and Cidea suggests that SREBP1c may serve as a transcriptional activator for saturated FA-induced Cidea expression. To test this hypothesis, we first overexpressed SREBP1c in AML12 cells and observed that Cidea (but not Fsp27 and Cideb) expression was significantly increased (Supporting Fig. 8A). The addition of PAs further enhanced this expression (Supporting Fig. 8A). Next, we knocked down SREBP1c in ob/ob hepatocytes (an 80% reduction in mRNA levels; Supporting Fig. 8B) and observed that mRNA levels of FAS, one of its downstream targets, were also reduced (Supporting Fig. 8B).