The protein markers that were highly expressed in controls include axin interactor dorsalization-associated protein (AIDA), alpha/beta hydrolase domain-containing protein 14Bv (ABHD14B), and glutamine-dependent NAD+ synthetase (NADSYN1), while proteins highly expressed in mild PD were quinoid dihydropteridine reductase (QDPR), alcohol dehydrogenase NADP+ (AKR1A1), and cannabinoid receptor-interacting protein 1 (CNRIP1). Here, QDPR is linked to Parkinson disease.