PPARα gene expression correlates with severity and histological treatment response in patients with non-alcoholic steatohepatitis.

Background & Aims: Peroxisome proliferator-activated receptors (PPARs) have been implicated in non-alcoholic steatohepatitis (NASH) pathogenesis, mainly based on animal data. Gene expression data in NASH patients are scarce. We studied liver PPARα, β/δ, and γ expression in a large cohort of obese patients assessed for presence of NAFLD at baseline and 1 year follow-up.

Methods: Patients presented to the obesity clinic underwent a hepatic work-up. If NAFLD was suspected, liver biopsy was performed. Gene expression was studied by mRNA quantification. Patients were reassessed after 1 year.

Results: 125 patients were consecutively included in the study, of which 85 patients had paired liver biopsy taken at 1 year of follow-up. Liver PPARα expression negatively correlated with the presence of NASH (p=0.001) and with severity of steatosis (p=0.003), ballooning (p=0.001), NASH activity score (p=0.008) and fibrosis (p=0.003). PPARα expression was positively correlated to adiponectin (R(2)=0.345, p=0.010) and inversely correlated to visceral fat (R(2)=-0.343, p<0.001), HOMA IR (R(2)=-0.411, p<0.001) and CK18 (R(2)=-0.233, p=0.012). Liver PPARβ/δ and PPARγ expression did not correlate with any histological feature nor with glucose metabolism or serum lipids. At 1 year, correlation of PPARα expression with liver histology was confirmed. In longitudinal analysis, an increase in expression of PPARα and its target genes was significantly associated with histological improvement (p=0.008).

Conclusion: Human liver PPARα gene expression negatively correlates with NASH severity, visceral adiposity and insulin resistance and positively with adiponectin. Histological improvement is associated with an increase in expression of PPARα and its target genes. These data might suggest that PPARα is a potential therapeutic target in NASH.