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PLoS Med. 2013;10(6):e1001462. doi: 10.1371/journal.pmed.1001462. Epub 2013 Jun 4.

Serum iron levels and the risk of Parkinson disease: a Mendelian randomization study.

Collaborators (193)

Plagnol V, Hernandez DG, Sharma M, Sheerin UM, Saad M, Simón-Sánchez J, Schulte C, Lesage S, Arepalli S, Barker R, Ben-Shlomo Y, Berendse HW, Berg D, Bhatia K, de Bie RM, Biffi A, Bloem B, Bochdanovits Z, Bonin M, Bras JM, Brockmann K, Brooks J, Burn DJ, Charlesworth G, Chen H, Chinnery PF, Chong S, Clarke CE, Cookson MR, Cooper JM, Corvol JC, Counsell C, Damier P, Dartigues JF, Deloukas P, Deuschl G, Dexter DT, van Dijk KD, Dillman A, Durif F, Dürr A, Edkins S, Evans JR, Foltynie T, Gao J, Gardner M, Gibbs JR, Goate A, Gray E, Guerreiro R, Harris C, van Hilten JJ, Hofman A, Hollenbeck A, Holton J, Hu M, Huang X, Huber H, Hudson G, Hunt SE, Illig T, Lambert JC, Langford C, Lees A, Lichtner P, Limousin P, Lopez G, Lorenz D, McNeill A, Moorby C, Moore M, Morris HR, Morrison KE, Mudanohwo E, O'Sullivan SS, Pearson J, Perlmutter JS, Pollak P, Post B, Potter S, Ravina B, Revesz T, Riess O, Rivadeneira F, Rizzu P, Ryten M, Sawcer S, Schapira A, Scheffer H, Shaw K, Shoulson I, Sidransky E, Smith C, Spencer CC, Stockton JD, Strange A, Talbot K, Tanner CM, Tashakkori-Ghanbaria A, Trabzuni D, Traynor BJ, Uitterlinden AG, Velseboer D, Vidailhet M, Walker R, van de Warrenburg B, Wickremaratchi M, Williams N, Williams-Gray CH, Winder-Rhodes S, Martinez M, Hardy J, Heutink P, Brice A, Gasser T, Singleton AB, Wood NW, Donnelly P, Barroso I, Blackwell JM, Bramon E, Brown MA, Casas JP, Corvin A, Deloukas P, Duncanson A, Jankowski J, Markus HS, Mathew CG, Palmer CN, Plomin R, Rautanen A, Sawcer SJ, Trembath RC, Viswanathan AC, Wood NW, Spencer CC, Band G, Bellenguez C, Freeman C, Hellenthal G, Giannoulatou E, Pirinen M, Pearson R, Strange A, Su Z, Vukcevic D, Donnelly P, Langford C, Hunt SE, Edkins S, Gwilliam R, Blackburn H, Bumpstead SJ, Dronov S, Gillman M, Gray E, Hammond N, Jayakumar A, McCann OT, Liddle J, Potter SC, Ravindrarajah R, Ricketts M, Waller M, Weston P, Widaa S, Whittaker P, Barroso I, Deloukas P, McCarthy MI, Ouwehand WH, Radhakrishnan A, Sambrook J, Toniolo D, Traglia M, Camaschella C, Metspalu A, Esko T, Gieger C, Ried J, Meitinger T, Oexle K, Winkelmann J, Swinkels D, Vermeulen S, van Duijn C, Broer L, Beilby J, Hui J, Anderson D, Visscher P, Martin N.

Author information

1
Center for Biomedicine, European Academy Bozen/Bolzano (EURAC), Bolzano, Italy. irene.pichler@eurac.edu

Erratum in

  • PLoS Med. 2013 Jun;10(6). doi:10.1371/annotation/c4d81646-0c0e-4a3e-9425-b220bae2d8b6.

Abstract

BACKGROUND:

Although levels of iron are known to be increased in the brains of patients with Parkinson disease (PD), epidemiological evidence on a possible effect of iron blood levels on PD risk is inconclusive, with effects reported in opposite directions. Epidemiological studies suffer from problems of confounding and reverse causation, and mendelian randomization (MR) represents an alternative approach to provide unconfounded estimates of the effects of biomarkers on disease. We performed a MR study where genes known to modify iron levels were used as instruments to estimate the effect of iron on PD risk, based on estimates of the genetic effects on both iron and PD obtained from the largest sample meta-analyzed to date.

METHODS AND FINDINGS:

We used as instrumental variables three genetic variants influencing iron levels, HFE rs1800562, HFE rs1799945, and TMPRSS6 rs855791. Estimates of their effect on serum iron were based on a recent genome-wide meta-analysis of 21,567 individuals, while estimates of their effect on PD risk were obtained through meta-analysis of genome-wide and candidate gene studies with 20,809 PD cases and 88,892 controls. Separate MR estimates of the effect of iron on PD were obtained for each variant and pooled by meta-analysis. We investigated heterogeneity across the three estimates as an indication of possible pleiotropy and found no evidence of it. The combined MR estimate showed a statistically significant protective effect of iron, with a relative risk reduction for PD of 3% (95% CI 1%-6%; p = 0.001) per 10 µg/dl increase in serum iron.

CONCLUSIONS:

Our study suggests that increased iron levels are causally associated with a decreased risk of developing PD. Further studies are needed to understand the pathophysiological mechanism of action of serum iron on PD risk before recommendations can be made.

PMID:
23750121
PMCID:
PMC3672214
DOI:
10.1371/journal.pmed.1001462
[Indexed for MEDLINE]
Free PMC Article

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