Figure 1.

Real-time PCR analysis showing decreased TTR gene transcription in HepG2 cells treated with 0.9 mM phenylalanine (A) or 1.2 mM phenylpyruvic acid (B). HepG2 cells were transfected with a reporter plasmid containing the mouse Ttr promoter region (C-F). Twenty-four hours after transfection, 0.9 mM phenylalanine (C) or 1.2 mM phenylpyruvic acid (D) were added for the indicated times. To determine whether the effects of phenylalanine and phenylpyruvic acid were dose dependent, various concentrations of phenylalanine (E) or phenylpyruvic acid (F) were added. The cells were lysed, and firefly and Renilla luciferase activities were measured. Reporter activity was calculated as the ratio of firefly luciferase activity to Renilla luciferase activity in the same sample. Values are expressed as a percentage of the reporter activity relative to that of control cells, and are plotted as the mean ± SD (n = 4-6). ^*P < 0.05, ^**P < 0.01, ^***P < 0.001 vs control cells using Student's t-test.