Figure 5. Epigenetic regulation of de novo lipogenesis by acetate is vital for cell survival under hypoxia.
(a) ACSS1/2 mediates acetate-induced palmitate and stearate production. Fractional abundance of palmitate (left) and stearate (right) isotopologues in ACSS1/2 stably double-knockdown HepG2 cells (designated as magenta) compared with that of control cells (designated as black) after 24 h of culture under hypoxia with [U-13C2]-acetate. Each histogram was presented as mean±s.d. of triplicate experiments. The inset shows the percentage of lipogenic acetyl-CoA derived from acetate carbon (**P<0.01; by Student's t-test). (b) Fractional abundance of palmitate (left panel) and stearate (middle panel) isotopologues in scramble (siscr) and siFASN HepG2 cells treat as in a. Each histogram was presented as mean±s.d. of triplicate experiments. The inset shows the percentage of lipogenic acetyl-CoA derived from acetate carbon. The knockdown efficiency was detected by PCR with reverse transcription (right panel) (**P<0.01; NS, not significant; by Student's t-test). (c)Acetate promotes cell survival under hypoxia. Viability of HepG2 cells treated with indicated concentrations of acetate under normoxia or hypoxia was determined via CCK8 assay. The results were presented as mean±s.d. of triplicate experiments (**P<0.01; ***P<0.001; NS, not significant; by Student's t-test). (d) Viability of control or siFSAN or siACACA HepG2 cells treated with or without 2.5 mM acetate under hypoxia was determined via CCK8 assay. The results were presented as mean±s.d. of triplicate experiments (***P<0.001; by Student's t-test). (e) ACSS1/2 mediates the promotion of cell survival by acetate. Viability of shscr or shACSS1/2 HepG2 stable cell lines treated as indicated was determined via CCK8 assay. The results were presented as mean±s.d. of triplicate experiments (*P<0.05; NS, not significant; by Student's t-test). (f) ACSS1/2 mediates cells growth advantage by acetate in Matrigel. Shscr or shACSS1/2 HepG2 cells were plated into the Matrigel bed and cultured with DMEM with 10% FBS, and 2% Matrigel for 12 days before the images were taken (left). Scale bar, 0.25 mm. The quantitative data were presented as mean±s.d. (n>3) (right) (***P<0.001; NS, not significant; by Student's t-test).