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 “By altering insulin resistance in midlife, it may be possible to
reduce future risk of Alzheimer’s,” said study co-author Barbara
Bendlin, an Alzheimer’s researcher at the University of Wisconsin
School of Medicine and Public Health, in an email to Reuters Health.
Insulin resistance, the body’s failure to respond to the hormone, is
a hallmark of diabetes. Diabetes itself – a disease in which the
body can't properly use insulin to convert blood sugar into energy -
has been linked to Alzheimer’s disease, but the exact nature of the
connection isn’t as clear.
In the current study of 150 middle-aged people with normal cognitive
function, those with higher blood sugar levels had significantly
lower levels of insulin processing, or glucose metabolism, in some
regions of the brain involved in memory performance, the study
found.
“Our findings suggest that insulin resistance could increase risk
for Alzheimer’s disease by affecting glucose metabolism in the
brain,” Bendlin said.
The study participants were all part of an Alzheimer’s disease
research project in Wisconsin, and two-thirds had a parent with the
disease. About 40 percent also had a gene, APOE, which is associated
with Alzheimer’s. Seven of them had diabetes.
Bendlin and colleagues found that people with higher levels of
insulin resistance, as well as participants with some variations of
the APOE gene, had lower glucose metabolism. But having parents with
Alzheimer’s didn’t affect total glucose metabolism.
Brain PET scans showed that lower glucose metabolism was associated
with worse immediate and delayed memory performance.
The study can’t show whether insulin resistance causes Alzheimer’s,
the researchers acknowledge in JAMA Neurology. More research is
needed to assess the interactions between insulin resistance, a
parental history of Alzheimer’s and the APOE gene, the authors
added.
In the meantime, people who are concerned about developing
Alzheimer’s may benefit from lifestyle choices that are associated
with less insulin resistance, such as getting adequate exercise and
maintaining a normal weight, Bendlin said.
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These lifestyle choices may have a broader benefit because insulin
resistance is also associated with other health problems including
cancer, polycystic ovarian disease, infections and trauma, said
Fernanda De Felice, a researcher at the Federal University of Rio de
Janeiro.
“Along with other recent studies in this field, this work
importantly establishes that insulin resistance in midlife is also a
threat to the brain, causing it to be dysfunctional,” De Felice, who
wasn’t involved in the study, said by email.
Earlier research has suggested that inhaled insulin could improve
memory in healthy adults and boost cognitive function in adults
suffering from the early stages of Alzheimer’s, De Felice said. But
other forms of insulin might not reach the brain.
There isn’t enough evidence yet to suggest that otherwise healthy
people might benefit from medications designed to control blood
sugar in diabetics, De Felice cautioned.
“It is important to control blood sugar levels and fight against
insulin resistance with adequate diet, exercise and medication as
directed by your doctor,” De Felice said. “But do not use insulin
just to prevent memory decline.”
SOURCE: http://bit.ly/1HZJi9N JAMA Neurology, online July 27, 2015.
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