[The title
was written by my editor. It does not represent with accuracy the research or
the news summary.]
The case study of a man lacking a gene linked to higher risk for
Alzheimer’s disease demonstrates that the gene is not essential for normal
cognitive function and may thus be targeted by new therapies.
by John
Tyburski
Copyright © Daily
Digest News, KPR Media, LLC. All rights reserved.
A variant
form of a gene involved in cholesterol transport has been known for two decades
to be a primary risk factor for developing Alzheimer’s disease. However, what
stood in the way between this discovery and targeting the apolipoprotein (APO)
E (apoE) gene variant 4, apoE4 was a concern that disruption of the protein the
gene encodes, APOE, may adversely affect neurological function. Now a report published Monday online in the journal JAMA
Neurology describes a case study that suggests the gene may yet be a viable
therapeutic target.
The case
study of a man who completely lacked the apoE gene and hence, had no APOE
function yet maintained normal cognitive and retinal (eye) function, opens up
new therapeutic possibilities for Alzheimer’s patients. The 40-year-old
California man was examined by physicians at the University of California, San
Francisco, for severe cholesterol elevation that was not responsive to
treatment. APOE is directly involved in cholesterol regulation. It is also
expressed in the central nervous system and the pigmented epithelium of the
eye, under the retinas.
“Despite
complete absence of apoE, he had normal vision, exhibited normal cognitive,
neurological, and retinal function, had normal findings on brain magnetic
resonance imaging, and had normal cerebrospinal fluid levels of β-amyloid and
tau proteins,” wrote the authors of the report. Tau and β-amyloid proteins
accumulate to form plaques in the brain cells of Alzheimer’s patients.
“Failure
of detailed neurocognitive and retinal studies to demonstrate defects in our
patient suggests either that the functions of apoE in the brain and eye are not
critical or that they can be fulfilled by a surrogate protein,” they continued.
“Surprisingly, with respect to central nervous system function, it appears that
having no apoE is better than having the apoE4 protein.”
“Despite
two decades of research into the mechanisms by which apoE4 contributes to
disease pathogenesis, a seemingly simple question remains unresolved: Is apoE
good or bad for brain health?” wrote Courtney Lane-Donovan and Joachim Herz in
an editorial that accompanied the report. “[T[he lack of
neurological findings in this patient would appear to answer the question of
whether apoE is necessary for brain function with a resounding no.”
The
authors of the report concluded by suggesting that apoE4 may be a viable
therapeutic target in treating Alzheimer’s.
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