December 22, 2005

Low brain estrogen linked to Alzheimer’s in women

By Martha Kerr

NEW YORK (Reuters Health) - Post-mortem studies of the
brains of women with Alzheimer's disease (AD) show a much lower
estrogen content than similar women without the disorder,
researchers report.

The findings may help explain the higher prevalence of AD
in women than men, since animal experiments show brain estrogen
deficiency accelerates the brain "plaque" build-up that
characterizes the disease.

Blood estrogen analysis did not support the brain tissue
findings, since serum estrogen was low in both the AD patients
and normal subjects, Dr. Rena Li and colleagues at the
University of Chicago note in the Proceedings of the National
Academy of Sciences.

Li told Reuters Health that "brain estrogen deficiency is
more specific than blood estrogen deficiency" in the
development of AD. "That is the key finding -- the brain can't
manufacture estrogen."

To examine the correlation between brain tissue findings
and the onset and severity of AD, Li's team conducted animal
studies in which they crossed mice lacking an
estrogen-synthesizing enzyme with mice carrying a protein
related to AD plaque build-up.

The resulting animals had greatly reduced brain estrogen
levels and early onset plaque formation. By contrast, mice that
underwent ovary removal did not develop estrogen-deficient
brain disease.

Li said the findings in these "ovariectomized" mice support
the fact that not all post-menopausal women develop AD. "It is
brain-specific...and may have a genetic basis," she explained.

She said potential treatment of AD with estrogen therapy
would require drug formulations that cross the tissue barrier
that separates blood from the brain. Her team is currently
screening a number of natural estrogen products to assess their
ability to cross this barrier.

SOURCE: Proceedings of the National Academy of Sciences,
December 19, 2005.