Journal of the Renin-Angiotensin- Aldosterone System 2015, Vol. 16(2) 428–433 © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1470320313494432 jra.sagepub.com Introduction Parkinson’s disease (PD) is a common neurodegenerative disorder clinically characterized by tremor, bradykinesia, rigidity and postural instability, and neuropathologically by the loss of dopaminergic neurons in the substantia nigra and the presence of Lewy bodies. 1 The disease is thought to result from a complex interaction between multiple predis- posing genes and environmental effects. Recent studies have shown that genetic factors play an important role in contributing to the pathogenesis of PD. The pivotal role of the angiotensin-converting enzyme (ACE) in the renin-angiotensin system lies in the conver- sion of angiotensin I to angiotensin II and degradation of bradykinin. 2 High concentrations of ACE have been detected in the nigrostriatal pathway and in basal ganglia. Thus, the ACE may be involved in the pathogenesis of PD. The ACE gene is located on chromosome 17q23 and con- sists of 26 exons and 25 introns. A functional polymor- phism has been identified in intron 16 and consists of the presence (I, insertion) or absence (D, deletion) of a 287- base pair Alu repeat sequence. 3 To date, five studies have examined the association between ACE I/D polymorphism and PD. 4–8 However, the results have been discordant. Most studies indicated a nonsignificant association in Caucasians or Latin Americans, 4,6–8 while one study suggested signifi- cant association in a Chinese population. 5 Thus, the aim of the present study using meta-analysis was to clarify the relationship between ACE I/D polymorphism and PD across different ethnic populations. Materials and methods Literature and search strategy We searched the literature databases including PubMed and Embase. The search strategy was to identify all possible studies that involved the use of the following key words: The angiotensin-converting enzyme (ACE) I/D polymorphism in Parkinson’s disease Gang Su, Hengli Dou, Limei Zhao, Hongjie Wang, Guiyang Liu, Bo Huang and Bo Peng Abstract Objective: The angiotensin-converting enzyme (ACE) may be involved in the pathogenesis of Parkinson’s disease (PD). There have been several studies investigating the association between ACE gene I/D polymorphism and PD risk, but they reported inconsistent findings. We performed a meta-analysis to investigate the association between ACE gene I/D polymorphism and PD risk. Methods: Published literature from PubMed and Embase databases were searched for eligible publications. Pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated using random- or fixed-effects models based on between-study heterogeneity. Results: A total of five studies including 606 cases and 708 controls were finally included in the meta-analysis. Meta- analysis showed that there was no obvious association between ACE gene I/D polymorphism and PD risk under the homogeneous co-dominant model (OR = 1.14, 95% CI = 0.71–1.82), heterogeneous co-dominant model (OR = 0.92, 95% CI = 0.70–1.22), dominant model (OR = 0.99, 95% CI = 0.76–1.28) or recessive model (OR = 1.07, 95% CI = 0.83–1.37). Conclusion: The meta-analysis suggests that there is no evidence for the association between ACE gene I/D polymor- phism and PD risk. Keywords Angiotensin-converting enzyme, polymorphism, Parkinson’s disease, meta-analysis Received: 14-Mar-2013 Accepted: 28-Apr-2013 Department of Neurosurgery,The Fourth People’s Hospital of Jinan, China Corresponding author: Bo Peng, Department of Neurosurgery, The Fourth People’s Hospital of Jinan, 50 Shifan Road, Jinan, 250031, China. Email: bopengjn@163.com 94432JRA 0 0 10.1177/1470320313494432Journal of the Renin-Angiotensin-Aldosterone SystemSu et al Original Article