A substance preventing adverse actions of conventional fibrate-series drugs as therapeutic agents for the metabolic syndrome and dyslipidemia to enhance the therapeutic effects thereof comprises an extract from Dunaliella salina or Dunaliella bardawil, for administration in combination with the fibrate-series drugs. The substance suppresses liver hypertrophy caused by the fibrate-series drugs as PPAR-α agonists and has an action of promoting fat combustion, suppressing fat synthesis and suppressing cell proliferation, to prevent disorders of liver functions.