To examine whether the decrease in the Mic60 or Lonp1 levels with aging is related to fat accumulation in the liver, we first transfected HepG2 human hepatoma cells with siRNAs against Immt and Lonp1. In all cases, transfection of both siRNAs led to the specific depletion of individual genes (Fig. 3a), and the cellular ATP production level and mitochondrial membrane potential gradually decreased (Supplementary Fig. 2). This evidence concerns the gene IMMT and hepatocellular carcinoma.