CYP2E1 and Parkinson disease: On the other hand, a study of six PD patients showed a lower DNA methylation at the promoter region of CYP2E1 gene in both cortex and putamen, and an increase of mRNA levels in cortex, suggesting that epigenetic variations of this isoform may contribute to PD susceptibility, but they did not study the correlation between mRNA levels and proteins or enzymatic activity [76].