Eating too much red meat, which raises brain levels of iron, may heighten the risk of developing Alzheimer's disease, researchers from the Semel Institute for Neuroscience and Human Behavior at UCLA reported in the Journal of Alzheimer's Disease.
As background information, the authors explained that iron can accelerate the damaging reactions of free radicals. Over time, iron builds up in brain gray matter regions and appears to contribute to the risk of developing Alzheimer's disease and other age-related illnesses.
Alzheimer's disease has been an exceptionally challenging enemy to defeat. Its number 1 risk factor is aging - something none of us can prevent.
Most scientists and specialists agree that Alzheimer's is caused by one of two proteins:
As we get older, these two proteins either disrupt signaling between neurons or kill them off.
Team leader, Dr. George Bartzokis and colleagues believe there is a third likely cause of Alzheimer's - iron accumulation.
Professor Bartzokis and team compared the hippocampus and the thalamus using sophisticated brain-imaging high- and low-field strength MRI instruments. The hippocampus is a brain region that is damaged early on in Alzheimer's, while the thalamus is only affected during the late stages.
In early stage Alzheimer's, iron has built up in the hippocampus but not the thalamus
The MRI scans showed that iron builds up over time in the hippocampus but not the thalamus. They also saw an association between iron accumulation levels in the hippocampus and tissue damage in that area.
Most scientists concentrate on the accumulation of beta-amyloid or tau that cause the hallmark plaques associated with Alzheimer's, Bartzokis explained.
For a long time, Bartzokis had been saying that the breakdown starts off much further "upstream".
Communication between neurons is disrupted when myelin, a fatty tissue that coats nerve fibers, is destroyed, promoting the accumulation of plaques. These amyloid plaques then destroy more myelin - a self-perpetuating cascade of destruction. The more the signaling is disrupted, the more the nerve cells die, and the classic signs of Alzheimer's appear.
Myelin is produced by oligodendrocytes. Oligodendrocytes are a type of brain cell. Bartzokis explained that oligodendrocytes, along with myelin, have the highest iron levels of any brain cells.
"Circumstantial evidence has long supported the possibility that brain iron levels might be a risk factor for age-related diseases like Alzheimer's," says Bartzokis.
Too much iron promotes oxidative damage
Iron is vital for cell function. However, too much of it encourages oxidative damage, something to which the brain is particularly susceptible.
Bartzokis and team set out to determine whether high tissue iron might cause the tissue breakdown associated with Alzheimer's. They focused on the hippocampus, an area of the brain that is involved in the formation of memories. They compared the hippocampus to the thalamus, which is relatively unaffected until the very late stages of the disease.
Their MRI technique was able to measure how much brain iron there was in a protein that stores iron - ferritin. The study included 31 Alzheimer's patients and 68 healthy individuals of the same age (controls).
Measuring iron in the brain is not easy if the patient has Alzheimer's, because the amount of water in the brain increases as the disease progresses. The more water there is in the brain, the harder it is to detect iron, Bartzokis explained.
Bartzokis said "It is difficult to measure iron in tissue when the tissue is already damaged. But the MRI technology we used in this study allowed us to determine that the increase in iron is occurring together with the tissue damage. We found that the amount of iron is increased in the hippocampus and is associated with tissue damage in patients with Alzheimer's but not in the healthy older individuals - or in the thalamus. So the results suggest that iron accumulation may indeed contribute to the cause of Alzheimer's disease."
The team added that the build up of iron in the brain could be the result of some modifying environmental factors, including how much red meat the person consumes, or their intake of iron dietary supplements. Another factor that can raise iron levels in the brain is having a hysterectomy before the menopause.
In an abstract in the journal, the authors concluded:
"The data shows that in AD, Hipp damage occurs in conjunction with ferritin iron accumulation. Prospective studies are needed to evaluate how increasing iron levels may influence the trajectory of tissue damage and cognitive and pathologic manifestations of AD."
Iron imbalance linked to Creutzfeldt-Jakob disease, Alzheimer's and Parkinson's
Researchers from Case Western Reserve University, Cleveland, reported in the Journal of Alzheimer's Disease (March 2013 issue) that an iron imbalance caused by prion proteins collecting in the brain is probably the cause of cell death in CJD (Creutzfeldt-Jakob disease).
The authors added that certain proteins found in the brains of patients with Alzheimer's and Parkinson's also regulate iron. They suggest that "neurotoxicity by the form of iron, called redox-active iron, may be a trait of neurodegenerative conditions in all three diseases."
Study leader, Neena Singh, said "There are many skeptics who think iron is a bystander or end-product of neuronal death and has no role to play in neurodegenerative conditions. We're not saying that iron imbalance is the only cause, but failure to maintain stable levels of iron in the brain appears to contribute significantly to neuronal death."