The ACE deletion polymorphism is not associated with Parkinson's disease

The deletion allele (D allele) polymorphism in the angiotensin converting enzyme (ACE) gene is associated with increased levels of the neuropeptide substance P in the basal ganglia and substantia nigra. A reduction of substance P levels in the brain occurs in Parkinson's disease (PD) and has been implicated in the pathogenesis of the disease. We investigated the hypothesis that the D allele may be protective towards PD by examining the frequency of the ACE (I/D) polymorphism in 178 PD cases (male:female ratio = 1.4) and 192 controls (male:female ratio = 1.5). ACE (I/D) genotype was determined using polymerase chain reaction and 3% agarose gel electrophoresis. Unadjusted chi-square analysis revealed no significant difference between genotype frequencies (chi2 = 3.30, p > 0.10) or allele frequencies (chi2 = 2.52, p > 0.10) between patient and control groups, although PD patients were less likely to be homozygous (OR = 0.80, 95% CI = 0.49-1.29) or heterozygous (OR = 0.80, 95% CI = 0.59-1.06) for the D allele. A stepwise logistic regression analysis of the ACE deletion and risk factor data confirmed that there was no significant association between the ACE deletion (D allele) polymorphism and PD (OR = 0.62, 95% CI = 0.35-1. 10, p = 0.10). This study does not support the hypothesis that the D allele of the ACE gene confers a protective effect with respect to PD.