Here, we revealed that YY1 is critical for alteration of lipid metabolism in HCC cells by suppressing the expression of peroxisome proliferator-activated receptor gamma coactivator-1β (PGC-1β), a transcriptional activator of medium-chain acyl-CoA dehydrogenase (MCAD) and long-chain acyl-CoA dehydrogenase (LCAD) 7, 30. The gene discussed is ACADM; the disease is hepatocellular carcinoma.