There are marked species differences in genes and proteins associated with the absorption, distribution, metabolism, and excretion (ADME) of xenobiotics and drugs, thus the human hepatocyte chimeric mice may not only be used for increasing the safety and effectiveness of lead drugs, but may also serve as a model system to study human liver disease and assess the potency and efficacy of dual and pan PPAR agonist in preventing or delaying disease progression. The gene discussed is PPARA; the disease is liver disorder.