The study, led by Lisa Mosconi, Ph.D., Research Assistant Professor of Psychiatry at NYU School of Medicine, was the first to compare brain metabolism among cognitively normal people who have a father, a mother, or no relatives with Alzheimer's disease.
In the new study, analysis of 49 cognitively normal individuals, from 50 to 80 years old, were made.
The participants had undergone a battery of neuropsychological and clinical tests, and PET (positron emission tomography) scans of their brains using a technique that labels glucose, the brain's fuel, with a special chemical tracer.
Sixteen subjects had a mother with the disease, and eight had a father with Alzheimer's. The remaining subjects didn't have a family history of the disease.
The analysis found that people with a maternal history of the disease had the largest reductions in glucose metabolism in several areas of the brain, including the medial temporal lobes and the posterior cingulate cortex, two brain regions involved with memory storage and retrieval.
Brain energy metabolism was reduced by 25 percent in the posterior cingulate cortex in this group.
There weren't any reductions in brain energy metabolism in the people without a family history and in those with a father who had the disease.
The effects in glucose metabolism among subjects with a maternal history remained significant after accounting for possible risk factors for Alzheimer's, including age, gender, education, Apolipoprotein E genotype, and subjective memory complaints.
The study also showed that only individuals with an affected mother have reduced brain metabolism in the same brain regions as Alzheimer's patients.
People with an affected parent have a 4- to 10-fold higher risk compared to individuals with no family history.
"This is a preliminary study and the results have to be replicated. What we need even more is to follow subjects over time until they develop clinical symptoms, and we really need to assess whether the metabolic reductions predict and correlate with disease progression," Mosconi said.
"Energy metabolism hasn't been a major focus of research in Alzheimer's, so we hope that this study will stimulate further discussion on brain activity and disease risk, which could also be important for planning targeted therapeutic interventions," she added.
"This is an intriguing finding," said Mony de Leon, Ed.D., Professor of Psychiatry and Director of the Center for Brain Health at NYU School of Medicine.
"It points to the need for more research to investigate the mechanisms of maternal transmission of this observed glucose metabolism deficit as well as to learn of any direct or indirect relationship to Alzheimer's disease," said Leon.
Mosconi said that it is not known why people with a family history are more susceptible to the disease.
Likewise, it isn't known why individuals with a history of the disease on their mother's side are at increased risk for Alzheimer's, and this observation must be replicated in larger studies before it could be of use in the clinic to perhaps identify people who may be more vulnerable to the disease, she said.
Mosconi speculated that genes that were maternally inherited might alter brain metabolism.
The study is published in the Proceedings of the National Academy of Sciences.