Is aging part of Alzheimer's disease, or is Alzheimer's disease part of aging?
ABSTRACT For 70 years after Alois Alzheimer described a disorder of tangle-and-plaque dementia, Alzheimer's disease was a condition of the relatively young. Definitions of Alzheimer's disease (AD) have, however, changed over the past 30 years and under the revised view AD has truly become an age-related disease. Most now diagnosed with AD are elderly and would not have been diagnosed with AD as originally conceived. Accordingly, younger patients that qualify for a diagnosis of AD under both original and current Alzheimer's disease constructs now represent an exceptionally small percentage of the diagnosed population. The question of whether pathogenesis of the "early" and "late" onset cases is similar enough to qualify as a single disease was previously raised although not conclusively settled. Interestingly, debate on this issue has not kept pace with advancing knowledge about the molecular, biochemical and clinical underpinnings of tangle-and-plaque dementias. Since the question of whether both forms of AD share a common pathogenesis could profoundly impact diagnostic and treatment development efforts, it seems worthwhile to revisit this debate.
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ABSTRACT: Epidemiological and biochemical studies show that the sporadic forms of Alzheimer's disease (AD) are characterized by the following hallmarks: (a) An exponential increase with age; (b) Selective neuronal vulnerability; (c) Inverse cancer comorbidity. The present article appeals to these hallmarks to evaluate and contrast two competing models of AD: the amyloid hypothesis (a neuron-centric mechanism) and the Inverse Warburg hypothesis (a neuron-astrocytic mechanism). We show that these three hallmarks of AD conflict with the amyloid hypothesis, but are consistent with the Inverse Warburg hypothesis, a bioenergetic model which postulates that AD is the result of a cascade of three events-mitochondrial dysregulation, metabolic reprogramming (the Inverse Warburg effect), and natural selection. We also provide an explanation for the failures of the clinical trials based on amyloid immunization, and we propose a new class of therapeutic strategies consistent with the neuroenergetic selection model.Frontiers in Physiology 01/2014; 5:522. DOI:10.3389/fphys.2014.00522
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ABSTRACT: Use of selective in-vivo tau imaging will enable improved understanding of tau aggregation in the brain, facilitating research into causes, diagnosis, and treatment of major tauopathies such as Alzheimer's disease, progressive supranuclear palsy, corticobasal syndrome, chronic traumatic encephalopathy, and some variants of frontotemporal lobar degeneration. Neuropathological studies of Alzheimer's disease show a strong association between tau deposits, decreased cognitive function, and neurodegenerative changes. Selective tau imaging will allow the in-vivo exploration of such associations and measure the global and regional changes in tau deposits over time. Such imaging studies will comprise non-invasive assessment of the spatial and temporal pattern of tau deposition over time, providing insight into the role tau plays in ageing and helping to establish the relation between cognition, genotype, neurodegeneration, and other biomarkers. Once validated, selective tau imaging might be useful as a diagnostic, prognostic, and progression biomarker, and a surrogate marker for the monitoring of efficacy and patient recruitment for anti-tau therapeutic trials. Copyright © 2015 Elsevier Ltd. All rights reserved.The Lancet Neurology 01/2015; 14(1):114-124. DOI:10.1016/S1474-4422(14)70252-2 · 21.82 Impact Factor
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ABSTRACT: Sporadic Alzheimers disease (sAD) has not been explained by any current theories, so new hypotheses are urgently needed. We proposed that energy and Ca2+ signaling deficits are perhaps the earliest modifiable defects in brain aging underlying memory decline and tau deposits (by means of inactivating Ca2+-dependent protease calpain). Consistent with this hypothesis, we now notice that at least eight other known calpain substrates have also been reported to accumulate in aging and AD. Thus, protein accumulation or aggregation is not a pathogenic event, but occurs naturally and selectively to a peculiar family of proteins, and is best explained by calpain inactivation. Why are only calpain substrates accumulated and how can they stay for decades in the brain without being attacked by many other non-specific proteases there? We believe that these long-lasting puzzles can be explained by calpains unique properties, especially its unusual specificity and exclusivity in substrate recognition, which can protect the substrates from other proteases attacks after calpain inactivation. Interestingly, our model, in essence, may also explain tau phosphorylation and the formation of amyloid plaques. Our studies suggest that a-secretase is an energy-/Ca2+-dual dependent protease and is also the primary determinant for A beta levels. Therefore, beta- and gamma-secretases can only play secondary roles and, by biological laws, they are unlikely to be positively identified. This study thus raises serious questions for policymakers and researchers and these questions may help explain why sAD can remain an enigma today.Frontiers in Aging Neuroscience 12/2014; 6. DOI:10.3389/fnagi.2014.00329 · 2.84 Impact Factor