Lead researcher AurielWillette, assistant professor of food science and human nutrition at
ISU, says the initial discovery of the gene TOMM40 gave the scientists
impression that it raises the risk of Alzheimer’s. But the findings were later
dismissed when several studies failed to replicate the results.
However, Willette and his colleagues weren’t convinced that
the gene was a total failure, so they decided to examine other elements that
may be producing the mixed results.
The researchers discovered a startling difference in the
gene’s effect on cognitive function, memory and risk based on a family history
of Alzheimer’s
disease and the length of a specific part of the gene.
“It was kind of a shot in the dark, but we found if you
don’t have a family history of Alzheimer’s disease, then having a longer
version of the gene is a good thing. It is related to better memory up to 10
years later and about one-fifth of the risk for developing Alzheimer’s
disease,” said Willette, who is also an adjunct assistant professor of
neurology at the University of Iowa.
“However, if your mom or dad has Alzheimer’s, then having a
long version is bad. It’s a complete polar opposite.”
The main pathological hallmarks ofAlzheimer’s disease are amyloid-β (Aβ) plaques, and neurofibrillary
tangles, caused by tau protein. These plaques and tangles around the neurons
eventually cause the neurons to die.
Outward symptoms start with mild memoryloss. As the symptoms progress, the
person finds it increasingly difficult to hold a conversation or carry out
everyday tasks such as button a shirt.
Although numerous studies being conducted worldwide are
providing new clues, scientists still do not know the exact causesof Alzheimer's disease. They think that there are various factors, and
some of these affect different people in different ways, according to the
study.
Family history of Alzheimer’s and TOMM40
The researchers designed the study to explore the magnitude to
which family history regulated the effects of TOMM40
on symptoms of Alzheimer's disease, such as thinking and memory loss.
They used data from two large studies of Alzheimer's
disease. One set of data came from 912 adults in the Wisconsin Registry for
Alzheimer's Prevention – a study which is following middle-aged adults at risk of
developing Alzheimer's and following changes in cognitive function and memory
loss, based on assessments carried out every 2 years for up to a decade.
The other set of data came from 365 participants in the
Alzheimer's Disease Neuroimaging Initiative – a study which is monitoring
similar changes in older adults with and without the disease.
The researchers found that having a family history of
Alzheimer's disease appears to make a big difference in how TOMM40 affects
memory and thinking, and that the difference depends on the length of a particular
portion of the gene. [Read more Study:Access to nature makes men and seniors sleep better]
Prof. Willette and his team found that having the longer
version of the gene, together with no family history of Alzheimer's, was linked
to around a one-fifth lower risk of developing Alzheimer's disease and better
memory up to 10 years later.
Family history was focused particularly on whether
Alzheimer’s disease was found in a participant’s parents. The researchers also discovered
a link between the family history, gene, and mitochondrial function, which produces
energy to power the cells. Age, gender and education were controlled for in the
examination of TOMM40 gene and family history in the participants.
The team is also involved in another project which is investigating factors that affect how the body makes and uses energy, such as
insulin resistance, as well as proteins and enzymes that affect energy
regulation.
Studies like these are slowly uncovering what happens to
thinking and memory when there is not enough energy for brain cells to perform
properly.
The study was published in Alzheimer’s & Dementia:
The Journal of the Alzheimer’s Association.
