The T Allele of the HNMT C314T Polymorphism Is Associated with a Reduced Risk of Idiopathic Parkinson's Disease in Mexican Patients.

Introduction: The histaminergic pathway has been implicated in Parkinson's disease (PD). Histamine is metabolized by histamine N-methyltransferase (HNMT), and the gene encoding this enzyme has a C314T polymorphism, in which cytosine is replaced by thymine. This results in reduced enzymatic activity. Objective: To analyze the C314T polymorphism of the HNMT gene in Mexican patients with idiopathic PD. Materials and Methods: In this study, peripheral blood samples were collected from patients with PD and healthy controls for genomic DNA extraction. HNMT genotyping was performed using the restriction fragment length polymorphism (RFLP) technique. Quantitative variables were compared using Student's t test, and categorical variables were compared using Pearson's χ2 test. The risk of PD was estimated using odds ratios (ORs) and 95% confidence intervals (CIs). Results: According to the results of the bivariate analysis, compared with the controls, the patients were significantly older (p = 0.001) and had a higher incidence of hypertension (p = 0.020). HNMT RFLP analysis suggested an association between the C allele and PD development, with an OR (95% CI) of 7.424 (0.866-63.646). In contrast, the T allele appeared to confer a protective effect, with an OR of 0.134. In the age-adjusted Mantel-Haenszel stratified analysis of the HNMT C314T polymorphism, the C allele was identified as a risk factor for PD development in this small cohort, with an OR (95% CI) of 12.0 (0.8-160.4; p = 0.041). Conclusions: Advanced age, hypertension, and the C allele of the HNMT gene were associated with an increased risk of PD, whereas the T allele appeared to be associated with a protective role.