Acetaminophen aggravates valproate‐induced hepatic lipid accumulation and apoptosis by facilitating valproate retention

Background and Purpose Hepatic steatosis is characteristic of valproate (VPA) induced hepatotoxicity. Drug–drug interactions of VPA and acetaminophen (APAP) have been associated with liver injury, but have not attracted sufficient attention. The present study aimed to elucidate the effect of VPA and APAP co‐administration on liver lipid accumulation and apoptosis. Experimental Approach Liver lipid accumulation and apoptosis were studied in vivo and in vitro. The concentration of VPA and its metabolite 4‐ene‐VPA, as well as changes in free fatty acids (FFAs), were detected by liquid chromatography–mass spectrometry (LC–MS). Additionally, lipid accumulation and mitochondrial damage caused by VPA and 4‐ene‐VPA were evaluated in vitro. Key Results Liver lipid accumulation after VPA and APAP co‐administration appeared earlier than liver injury in mice. VPA caused fatty acid accumulation by damaging mitochondria, increased triglyceride (TG) synthesis by up‐regulating DGAT1/2 expression, and impaired TG transport by inhibiting expression of microsomal triglyceride transfer protein (MTTP). APAP inhibited the β‐oxidation process by inhibiting CPT1α. During VPA and APAP co‐administration, APAP inhibition of β‐oxidation of VPA resulted in VPA retention and production of its toxic metabolite 4‐ene‐VPA, which caused further lipid accumulation and hepatocyte apoptosis. Conclusions and Implications VPA is the main factor contributing to intrahepatic lipid accumulation, but did not induce apoptosis of hepatocytes. APAP inhibited β‐oxidation of VPA and caused VPA retention, which aggravated and prolonged the lipid accumulation and finally resulted in hepatocyte apoptosis. We provide evidence and guidance on the use of VPA and APAP in the clinic.