Figure 3.

ATF4 activation contributes to palmitate-induced CD36 upregulation in hepatocytes. A: primary mouse hepatocytes were treated with palmitate at 0.6 mM for 16 h. mRNA levels of Atf4 and Vldlr, an ATF4 target gene, were measured using real-time qPCR. Data are expressed as means ± SD, n = 4 separate experiments. Student’s t test was used for statistical evaluation (**P < 0.01; ***P < 0.001). B: primary mouse hepatocytes were treated with palmitate at 0.6 mM for 16 h. ATF4 protein was detected by Western blotting. The same loading control (actin) was used as presented in Fig. 1F as they were from the same Western blot membrane. AML-12 cells were transfected with either scramble siRNA (si-Ctrl) or Atf4 siRNA (si-Atf4) for 24 h before a 16-h palmitate exposure (0.4 mM). ATF4 expression (C and D), activity (E), and CD36 expression (F and G) were determined by real-time qPCR, Western blotting, and ELISA, respectively, and data were expressed as means ± SD, n = 4 separate experiments. Student’s t test was used for statistical evaluation (*P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001). ATF4, activating transcription factor 4; CD36, cluster of differentiation 36.