The present invention provides a transgenic non-human animal comprising a human-derived LXR.alpha. mutant gene to express a human LXR.alpha. mutant protein, wherein the human LXR.alpha. mutant is an isoform of LXR.alpha. involved in inhibition of normal cholesterol metabolism by normal LXR.alpha.; a nucleic acid construct which can be used to produce the transgenic non-human animal; and use thereof.