Does this qualify as irony? Our bodies need iron to be healthy – but too much could harm our brains by bringing on Alzheimer's disease.
If that's the case, measuring people's brain iron levels could help identify those at risk of developing the disease. And since we already have drugs that lower iron, we may be able to put the brakes on. Despite intense efforts, the mechanisms behind this form of dementia are still poorly understood. For a long time the main suspect has been a protein called beta-amyloid, which forms distinctive plaques in the brain, but drugs that dissolve it don't result in people improving.
Researchers at the University of Melbourne in Australia followed 144 older people who had mild cognitive impairment for seven years. To gauge how much iron was in their brains, they measured ferritin, a protein that binds to the metal, in their cerebrospinal fluid. For every nanogram per millilitre people had at the start of the study, they were diagnosed with Alzheimer's on average three months earlier. The team also found that the biggest risk gene for Alzheimer's, ApoE4, was strongly linked with higher iron, suggesting this is why carrying the gene makes you more vulnerable. Iron is highly reactive, so it probably subjects neurons to chemical stress, says team member Scott Ayton.
The finding by itself doesn't prove that reducing iron levels would cut people's risk of Alzheimer's but a trial of a drug that rids the body of some of its iron, carried out 24 years ago, suggests it's a hypothesis worth investigating. The drug halved the rate of Alzheimer's cognitive decline but was overlooked when the beta-amyloid theory of the disease became dominant, says Ayton. "Perhaps it's time to refocus the field on looking at iron as a target," he says. One easy way of reducing iron levels - having regular blood donations - would not be a good idea for older people as it can bring on anaemia. Also, says Ayton, "there is only a modest correlation between iron levels in the blood and in the brain." However, there is an iron-binding drug called deferiprone which gets into the brain and reduces levels of the metal there without disturbing blood levels too much. It is used to treat cases of iron poisoning and has also been found to slow the progression of Parkinson's disease, another condition in which high iron levels have been implicated.