Posted as an early online publication of the peer-reviewed journal Neurobiology of Aging, this largest-ever study of brain iron demonstrates gender difference in brain iron levels for the first time. Until now, researchers had considered the brain blood barrier as protection against accumulating too much iron from the body. The finding suggests instead that age-related brain iron accumulation is a modifiable risk factor for degenerative brain diseases.
In addition, the study finds a nearly perfect correlation between iron levels in various brain regions of study participants measured using MRI and those reported by past post-mortem studies. The finding demonstrates the ability of MRI analysis to accurately measure iron levels in brain tissues of living patients.
Previous studies have shown that high accumulation of iron in brain tissue causes oxidative damage and formation of plaques found in age-related neurodegenerative disorders such as Alzheimer disease. In addition, past population studies show men develop such diseases about five years earlier than women but brain iron levels increase with age in both genders.
"If you can measure it and learn how to modify it, then you can fix it," said Dr. George Bartzokis, lead author and professor of neurology at the David Geffen School of Medicine at UCLA. "Alzheimer disease rates double every five years after age 60, so a modifiable risk factor assessed by non-invasive means may represent potential interventions that could halve the number of cases of AD in the United States."
The UCLA team measured iron stored in ferritin molecules in the brain tissues of living subjects with MRI by using the Field Dependent Relaxation Rate Increase (FDRI) method. Iron was measured in four subcortical tissues, three white matter regions and the hippocampus of 165 healthy adults, ages 19 to 82.
In addition to the nearly perfect correlation between published post-mortem brain iron levels and those measured by FDRI, the study found that men have significantly higher ferritin iron than women in two subcortical regions and all three white matter regions.
The team also found significant age-related increases in ferritin iron in the hippocampus and three of the four subcortical regions, and decreases in one white matter region.
The study was supported by the National Institute of Mental Health, the National Institute on Aging Alzheimer's Disease Research Center, the California Department of Health Services, the Sidell-Kagan Foundation and the Department of Veterans Affairs.
Bartzokis is professor of neurology, director of the UCLA Memory Disorders Clinic, director of the Clinical Core of the UCLA Alzheimer Disease Research Center and faculty member at the UCLA Laboratory of Neuro Imaging.
The UCLA Department of Neurology encompasses more than a dozen research, clinical and teaching programs. These programs cover brain mapping and neuroimaging, movement disorders, Alzheimer disease, multiple sclerosis, neurogenetics, nerve and muscle disorders, epilepsy, neuro-oncology, neurotology, neuropsychology, headaches and migraines, neurorehabilitation, and neurovascular disorders. The department ranks No. 2 among its peers nationwide in National Institutes of Health funding. For more information, see http://neurology.medsch.ucla.edu/.
The UCLA Alzheimer Disease Research Center (ADRC), directed by Dr. Jeffrey L. Cummings, is funded by the National Institute on Aging, the Alzheimer's Disease Research Center of California grant and the Sidell Kagan Foundation. For more information, see http://www.adc.ucla.edu/.
The UCLA Memory Disorders Clinic and the Clinical Core of the Alzheimer Disease Research Center evaluate individuals over the age of 45 who are experiencing mild but gradually progressing cognitive or memory declines that are unrelated to other brain diseases such as strokes, tumors, infection, metabolic abnormalities, psychiatric disease or trauma. For information, call (310) 825-1817.
Journal
Neurobiology of Aging