Debrisoquine metabolism in Chinese patients with Alzheimer's and Parkinson's diseases

Genetic polymorphism and Parkinson's disease in Taiwan: study of debrisoquine 4-hydroxylase (CYP2D6)

Debrisoquine 4-hydroxylase (CYP2D6) is one of the cytochrome P450 enzyme families that catalyze the breakdown of a variety of exogenous and endogenous compounds. Previous reports have suggested that genetic polymorphisms of debrisoquine 4-hydroxylase are associated with susceptibility to Parkinson's disease (PD) in Caucasians. To determine if CYP2D6 also confers susceptibility to PD in Chinese patients, we carried out a study of genetic association using three polymorphic markers of the CYP2D6 gene, 188C/T, 1934G/A (mutant B), and 4268G/C. No differences of allele or genotype frequencies of these three polymorphisms were detected upon comparison of primary PD patients (n=53) with normal controls (n=94). The 1934A allele (mutant B), which accounts for the majority of poor metabolizers in Caucasians, is extremely rare in Chinese. Our data do not support the suggestion that the CYP2D6 gene is related to PD susceptibility in Chinese.

P450 enzymes and Parkinson's disease: the story so far

Environmental or endogenous toxins may cause nigral cell death in Parkinson's disease (PD) as a result of genetic susceptibility conferred by altered expression of P450 enzymes. Attention over the last 10 years has focused on CYP2D6 polymorphisms and susceptibility to PD. This review summarizes reports arising from both phenotypic and genotypic studies involving CYP2D6 and PD. Phenotypic studies have failed to support a link between CYP2D6 and PD. The more powerful genetic studies initially indicated a link between CYP2D6B mutations and PD, but critical analysis of the literature and recent studies emerging from independent laboratories fail to confirm this. Mutations in CYP2D6B are also not implicated in familial PD. As yet, there is no conclusive evidence to suggest that CYP2D6 polymorphisms confer susceptibility to PD. Whether polymorphisms in other P450s (for example, CYP1A1 and CYP2E1) are implicated in PD remains to be established.