An effective treatment for sporadic Alzheimer’s
disease rests on the translation of the disease
pathways we have discussed, as well as additional
molecular mechanisms or new risk genes (e.g.,
apolipoprotein J) defined by gene-expression profiling
and whole-genome association studies,181,182
into specific pharmacologic targets. Examples of
recently discovered proteins encoded by these
risk genes and mechanisms include apolipoprotein
J (clusterin), another Aβ chaperone,183
TOMM40, a transporter of proteins across the mitochondrial
membrane, and Sortillin-related receptor,
which functions to partition amyloid precursor
protein away from β-secretase and
γ-secretase; this is consistent with observations
that levels are reduced in the brains of patients
with Alzheimer’s disease and mild cognitive impairment.184,185
Another potential risk factor for
sporadic Alzheimer’s disease, general anesthesia,
promotes tau insolubility and Aβ oligomerization,186,187
deficiency of estrogen in the brains
of postmenopausal women,188 and chronic activation
of the glucocorticoid axis.189 However,
their underlying mechanisms are diverse, and
whether any of these factors lead to amyloid deposition
and tauopathy in humans is unknown.
Prospective studies also show that cognitive leisure
activity and training can lower the risk of
dementia190; findings from these studies provide
support for the concept of building a “cognitive
reserve.” The figure in the Supplementary Appendix
(available with the full text of this article
at NEJM.org) summarizes the heterogeneity of
pathways that could initiate and drive Alzheimer’s
disease. There is no single linear chain of
events. Complicating matters, some changes are
not pathologic but reactionary or protective.
Thus, the development of a multitargeted approach
to prevent or symptomatically treat Alzheimer’s
disease, as used in current practice for
other multigenic disorders, is needed.191 Recent
studies point to brain atrophy and other pathologic
conditions, not severe amyloid or tangle
load, in accounting for dementia in the oldest old
(persons 80 years of age or older).192 It remains
possible that many of these mechanisms, including
the amyloid hypothesis, are minor or wrong
and that some critical aging-related process is
the disease trigger.
An effective treatment for sporadic Alzheimer’sdisease rests on the translation of the diseasepathways we have discussed, as well as additionalmolecular mechanisms or new risk genes (e.g.,apolipoprotein J) defined by gene-expression profilingand whole-genome association studies,181,182into specific pharmacologic targets. Examples ofrecently discovered proteins encoded by theserisk genes and mechanisms include apolipoproteinJ (clusterin), another Aβ chaperone,183TOMM40, a transporter of proteins across the mitochondrialmembrane, and Sortillin-related receptor,which functions to partition amyloid precursorprotein away from β-secretase andγ-secretase; this is consistent with observationsthat levels are reduced in the brains of patientswith Alzheimer’s disease and mild cognitive impairment.184,185Another potential risk factor forsporadic Alzheimer’s disease, general anesthesia,promotes tau insolubility and Aβ oligomerization,186,187deficiency of estrogen in the brainsof postmenopausal women,188 and chronic activationof the glucocorticoid axis.189 However,their underlying mechanisms are diverse, andwhether any of these factors lead to amyloid depositionand tauopathy in humans is unknown.Prospective studies also show that cognitive leisureactivity and training can lower the risk ofdementia190; findings from these studies providesupport for the concept of building a “cognitivereserve.” The figure in the Supplementary Appendix(available with the full text of this articleat NEJM.org) summarizes the heterogeneity ofpathways that could initiate and drive Alzheimer’sdisease. There is no single linear chain ofevents. Complicating matters, some changes arenot pathologic but reactionary or protective.Thus, the development of a multitargeted approachto prevent or symptomatically treat Alzheimer’sdisease, as used in current practice forother multigenic disorders, is needed.191 Recentstudies point to brain atrophy and other pathologicconditions, not severe amyloid or tangleload, in accounting for dementia in the oldest old(persons 80 years of age or older).192 It remainspossible that many of these mechanisms, includingthe amyloid hypothesis, are minor or wrongand that some critical aging-related process isthe disease trigger.
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