ORIGINAL ARTICLES

Gene-environment interactions in parkinsonism and Parkinson’s disease: the Geoparkinson study

F D Dick¹, G De Palma⁴, A Ahmadi⁶, A Osborne², N W Scott³, G J Prescott³, J Bennett³, S Semple¹, S Dick¹, P Mozzoni⁵, N Haites², S Bezzina Wettinger⁸, A Mutti⁴, M Otelea⁷, A Seaton¹, P Soderkvist⁶, A Felice⁸, on behalf of the Geoparkinson Study Group

¹ Department of Environmental and Occupational Medicine, University of Aberdeen, UK
² Department of Medical Genetics, University of Aberdeen, UK
³ Department of Public Health, University of Aberdeen, UK
⁴ Department of Clinical Medicine, Nephrology and Health Science, Laboratory of Industrial Toxicology, University of Parma, Parma, Italy
⁵ ISPESL Research Centre, University of Parma, Parma, Italy
⁶ Division of Cell Biology, Department of Biomedicine and Surgery, Faculty of Health Sciences, Linköping University, Linköping, Sweden
⁷ Department of Occupational Medicine, University Hospital ‘Colentina, Bucharest, Romania
⁸ Laboratory of Molecular Genetics, Department of Physiology and Biochemistry, University of Malta, Msida, Malta

Finlay D Dick, Department of Environmental and Occupational Medicine, University of Aberdeen, Foresterhill, Aberdeen, UK; f.dick{at}abdn.ac.uk

Objectives: To investigate associations of Parkinson’s disease (PD) and parkinsonian syndromes with polymorphic genes that influence metabolism of either foreign chemical substances or dopamine and to seek evidence of gene-environment interaction effects that modify risk.

Methods: A case-control study of 959 prevalent cases of parkinsonism (767 with PD) and 1989 controls across five European centres. Occupational hygienists estimated the average annual intensity of exposure to solvents, pesticides and metals, (iron, copper, manganese), blind to disease status. CYP2D6, PON1, GSTM1, GSTT1, GSTM3, GSTP1, NQO1, CYP1B1, MAO-A, MAO-B, SOD 2, EPHX, DAT1, DRD2 and NAT2 were genotyped. Results were analysed using multiple logistic regression adjusting for key confounders.

Results: There was a modest but significant association between MAO-A polymorphism in males and disease risk (G vs T, OR 1.30, 95% CI 1.02 to 1.66, adjusted). The majority of gene-environment analyses did not show significant interaction effects. There were possible interaction effects between GSTM1 null genotype and solvent exposure (which were stronger when limited to PD cases only).

Conclusions: Many small studies have reported associations between genetic polymorphisms and PD. Fewer have examined gene-environment interactions. This large study was sufficiently powered to examine these aspects. GSTM1 null subjects heavily exposed to solvents appear to be at increased risk of PD. There was insufficient evidence that the other gene-environment combinations investigated modified disease risk, suggesting they contribute little to the burden of PD.

Abbreviations: AAI, average annual intensity; bp, base pair; CE, cumulative exposure; HWE, Hardy-Weinberg equilibrium; JEM, job exposure matrix; OEL, occupational exposure limit; OR, odds ratios; PCR, polymerase chain reaction; PD, Parkinson’s disease; RFLP, restriction fragment length polymorphism

Keywords: Parkinson’s disease; parkinsonism; genetics

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