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SCIENTIFIC LITERATURE · MED

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

Pichler I, Del Greco M F, Gögele M, Lill CM, Bertram L, Do CB, Eriksson N, Foroud T, Myers RH, PD GWAS Consortium, Nalls M, Keller MF, International Parkinson's Disease Genomics Consortium, Wellcome Trust Case Control Consortium 2, Benyamin B, Whitfield JB, Genetics of Iron Status Consortium, Pramstaller PP, Hicks AA, Thompson JR, Minelli C.

PLoS Med · 2013-06-04

DOI: 10.1371/journal.pmed.1001462PMID: 23750121

Open accessResearch Support, N.I.H., Intramural; Research Support, Non-U.S. Gov't; research-article; Research Support, U.S. Gov't, Non-P.H.S.; Journal Article; Research Support, N.I.H., ExtramuralOriginal source ↗

Research overview

The text below is the source article’s original abstract under a verified reuse license. cc by

BackgroundAlthough 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 findingsWe 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.ConclusionsOur 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.

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