AIM: To elucidate the role of the peroxisome proliferator-activated receptor α (PPARα) and its target gene citine palmitoyl acyl-CoA transferase 1A (CPT1A)in the pathogenesis of hepatitis C virus (HCV) infection.METHODS: Liver samples were collected from the patients with chronic HCV infection and controls. HepG2cells were transfected with vector pEF352neo carrying.Two independent clones (clone N3 and N4) stably expressing HCV core protein were analyzed. Total RNA was extracted from cells and liver tissues. PPARα and CPT1A mRNAs were quantified by real-time polymerase chain reaction (PCR) using SYBR Green Master. Total extracted proteins were separated by polyacrylamide gel electrophoresis, and electroblotted. Membranes were incubated with the anti-PPARα antibody, then with a swine anti-rabbit IgG conjugated to horseradish peroxidase for PPARα. Protein bands were revealed by an enhanced chemiluminescence reaction for PPARα. For immunohistochemical staining of PPARα, sections were incubated with the primary goat polyclonal antibody directed against PPARα at room temperature.RESULTS: Real-time PCR indicated that the PPARα level and expression level of CPT1A gene in hepatitis C patients lowered significantly as compared with the controls (1.8±2.8 vs 13±3.4, P = 0.0002; 1.1±1.5 vs 7.4+1, ,P = 0.004). West blot results showed that the level of PPARα protein in the livers of hepatitis C patients was lower than that in controls (2.3±0.3 vs 3.6±0.2,P = 0.009). The immunohistochemical staining results in chronic hepatitis C patients indicated a decrease in PPARα staining in hepatocytes compared with those in the control livers. The in vitro studies found that in the N3 and N4 colon stably expressing HCV core protein, the PPARα mRNA levels were significantly lower than that in the controls.CONCLUSION: The impaired intrahepatic PPARα expression is associated with the pathogenic mechanism in hepatic injury during chronic HCV infection. HCV infection reduced the expression of PPARα and CPT1A at the level of not only mRNAs but also proteins. PPARα plays an important role in the pathogenesis of chronic HCV infection, but the impaired function of this nuclear receptor in HCV infection needs further studies.