In relation to NAFLD, Kettner et al. demonstrated that disruption of the circadian rhythm in jet-lag-induced mice fed ad libitum resulted in metabolic syndrome and liver injury, progressing from NAFLD to nonalcoholic steatohepatitis (NASH) and fibrosis, similar to those seen in mice lacking the circadian genes Bmal1, Per1; Per2, or Cry1; Cry2 and therefore lacking a circadian clock [46]. This evidence concerns the gene PER2 and metabolic dysfunction-associated steatohepatitis.