Systemic activation of the NRF2 pathway has also been demonstrated in PD [26] in a study involving 45 PD patients and 40 control subjects, revealing an increase in the mRNA levels of glutamate-cysteine ligase (GCL), (p < 0.01) as well as elevated protein levels of NQO1 (p < 0.01) detected in leukocytes (number of controls and cases, each of 38). Here, GCLC is linked to Parkinson disease.