Irene Pichler and her team from the multi-institution research group, EURAC, assessed studies involving more than 130,000 people in Europe, North America and Australia in coming to their conclusions.
“[Our]…study suggests a causal association between increased serum iron levels and decreased risk of developing Parkinson’s disease, suggesting that disrupted iron metabolism may be an important factor in the pathogenesis of Parkinson’s disease,” they wrote.
They said the mechanism of action remained unclear, calling on more research into that area, “before any specific treatment recommendations can be proposed.”
But, “The effect of dietary iron or drugs capable of altering the balance between serum iron and iron storage compartments, might prove to be suitable to test in experimental models.”
“The development of such disease models is therefore necessary before any public health or clinical recommendation can be made for primary prevention in subjects at high risk of developing Parkinson’s disease.”
The researchers assessed the possible link between blood iron levels and the risk of developing Parkinson´s disease by using three polymorphisms in two genes, HFE and TMPRSS6.
In arriving at their conclusions, a meta-analysis was performed for each polymorphism including 22,000 people from Europe and Australia, as well as a meta-analysis of studies investigating the genetic effect on the risk of Parkinson´s disease with 20,809 people and 88,892 people in control groups.
On the uncertainty of the mechanism of action the researchers speculated that, “Low peripheral iron levels may reduce the functioning of neuronal enzymes or receptors, since iron is a crucial cofactor of tyrosine hydroxylase, which plays a role in the synthesis of monoamine neurotransmitters, and is involved in dopaminergic neurodevelopment.”
“Furthermore, low iron levels may decrease neuronal iron storage in the form of ferritin…A reduction in ferritin could decrease neuronal iron utilization by decreasing the pool of iron available for neuronal enzymes…”
They added that tyrosine hydroxylase, “represents the rate-limiting enzyme of dopamine synthesis.”
The causes of Parkinson's disease are not yet understood.
Published online June 4 (doi:10.1371/journal.pmed.1001462)
‘Serum Iron Levels and the Risk of Parkinson Disease: A Mendelian Randomization Study’
Authors: Pichler I, Del Greco M. F, Gögele M, Lill CM, Bertram L, et al.