This enzyme acts through nuclear receptors (the glucocorticoid receptor, the forkhead transcription factor, and the nuclear receptor 4a) to stimulate transcription of hepatitis B. PPARGC1 is known to be up-regulated by fasting, cold temperature or stress [53], and, remarkably, it is significantly up-regulated in the mild LCMV infection but not in the virulent infection; this has been validated by quantitative PCR (Table 2). Here, PPARGC1A is linked to hepatitis B virus infection.