Effects of clevudine on mitochondrial DNA copy number and mRNA levels of mitochondria-related genes. The mitochondrial DNA copy number and the mRNA levels of mtDNA-encoded or nuclear DNA-encoded genes were measured using quantitative PCR. Clevudine reduced the expressions of mtDNA (A & D) and cytochrome c oxidase-1 (Cox-1) mRNA (B & E) in the rat clonal β-cell line INS-1E and in the human hepatoma cell line HepG2 in a dose-dependent manner. Nuclear-encoded genes related to mitochondrial biogenesis such as PPAR-γ coactivator 1α (PGC-1α), mitochondrial transcription factor A (Tfam), and nuclear respiratory factor 1 (NRF1) were upregulated by clevudine treatment (C). Succinate dehydrogenase (SDH) was also upregulated by clevudine (C). Data presented are means ± SEM. The number of experiments is shown in parenthesis. *, **, and *** denote p < 0.05, p < 0.01, and p < 0.001, respectively.