MRS shows abnormalities before symptoms in familial Alzheimer disease

Dementia Research Centre, Institute of Neurology, University College of London, London, UK.
Neurology (Impact Factor: 8.29). 04/2006; 66(5):718-22. DOI: 10.1212/01.wnl.0000201237.05869.df
Source: PubMed


Pathologic change in Alzheimer disease (AD) begins some years before symptoms. MRS has the potential to detect metabolic abnormalities reflecting this early pathologic change. Presenilin 1 (PS1) and amyloid precursor protein (APP) mutation carriers have a nearly 100% risk of developing AD and may be studied prior to symptom onset.
Short echo time proton MR spectra were acquired from a midline posterior cingulate voxel in presymptomatic carriers of PS1 or APP mutations ("presymptomatic mutation carriers" [PMCs]; n = 7) and age- and sex-matched control subjects (n = 6). Ratios of N-acetyl aspartate (NAA), myo-inositol (MI), and choline-containing compounds (Cho) to creatine (Cr) were measured and NAA/MI calculated. Regression analyses and t tests were performed after log transformation.
PMC and control subjects were matched for age and sex. PMC subjects were 1.7 to 21.6 years (mean 9.8 years) before expected symptom onset, predicted from family-specific mean age at onset. Age did not significantly affect metabolite ratios. Geometric mean ratios in control subjects were as follows: NAA/Cr = 1.75, MI/Cr = 0.59, and NAA/MI = 2.95. NAA/Cr and NAA/MI were significantly reduced in PMC relative to controls (NAA/Cr mean decrease 10% [95% CI 2 to 18%]; NAA/MI mean decrease 25% [95% CI 3 to 44%]). MI/Cr was increased in PMC, but the differences did not achieve significance (19% increase [95% CI 1% decrease to 41% increase]; p = 0.07)). In PMCs, reduction in NAA/MI (p = 0.001) and MI/Cr (p = 0.002) were related to proximity of expected age at onset.
Metabolic changes are detectable in presymptomatic mutation carriers years before expected onset of Alzheimer disease. Their magnitude is related to proximity of expected age at onset.

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Available from: Lisa Cipolotti, Jan 15, 2016
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    • "3. Results 3.1. Significant reductions in NAA involve a downregulation of Nat8L expression in the 5xFAD mouse brain Reductions in NAA are a feature of early pathology in animal models of AD (Lalande et al., 2014; Dedeoglu et al., 2004) and in affected humans (Godbolt et al., 2004). The 5xFAD mouse, which harbors five familial AD mutations, presents with the accumulation of soluble and insoluble Aß42 from 2 months of age, cortical and hippocampal cell loss from 6 months of age, and progressive cognitive decline from 6 months of age (Oakley et al., 2006). "
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    ABSTRACT: N-acetylaspartate (NAA) provides a non-invasive clinical index of neuronal metabolic integrity across the entire neurodegenerative spectrum. While NAA function is not comprehensively defined, reductions in the brain are associated with compromised mitochondrial metabolism and are tightly linked to ATP. We have undertaken an analysis of abnormalities in NAA during early stage pathology in the 5xFAD mouse model of familial Alzheimer's disease and show here that dysregulated expression of the gene encoding for the rate-limiting NAA synthetic enzyme (Nat8L) is associated with deficits in mitochondrial oxidative phosphorylation in this model system. Downreguation of Nat8L is particularly pronounced in the 5xFAD hippocampus, and is preceded by a significant upregulation of oligodendrocytic aspartoacylase (aspa), which encodes for the sole known NAA-catabolising enzyme in the brain. Reductions in 5xFAD NAA and Nat8L cannot be accounted for by discrepancies in either neuron content or activity of the substrate-providing malate-aspartate shuttle, thereby implicating transcriptional regulation in a coordinated response to pathological energetic crisis. A central role for ASPA in this response is supported by a parallel developmental analysis showing highly significant increases in Nat8L expression in an ASPA-null mouse model during a period of early postnatal development normally punctuated by the transcriptional upregulation of aspa. These results provide preliminary evidence of a signaling mechanism in Alzheimer's disease that involves cross talk between neurons and oligodendrocytes, and suggest ASPA acts to negatively regulate Nat8L expression. This mechanism is proposed to be a fundamental means by which the brain conserves available substrate during energy crises. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · Mar 2015 · Molecular and Cellular Neuroscience
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    • "The metabolite formula changes in preclinical familial AD families with amyloid precursor protein, presenilin 1 or 2 mutations. Asymptomatic mutation carriers demonstrated elevated mI/Cr and decreased NAA/Cr with reduction in NAA/mI correlating with nearness to age of onset.92 In addition to serving as a marker of preclinical disease, MRS has utility in monitoring disease progression. "
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    ABSTRACT: Aging is the primary risk factor for dementia. With increasing life expectancy and aging populations worldwide, dementia is becoming one of the significant public health problems of the century. The most common pathology underlying dementia in older adults is Alzheimer's disease. Proton magnetic resonance spectroscopy (MRS) may provide a window into the biochemical changes associated with the loss of neuronal integrity and other neurodegenerative pathology that involve the brain before the manifestations of cognitive impairment in patients who are at risk for Alzheimer's disease. This review focuses on proton MRS studies in normal aging, mild cognitive impairment, and dementia, and how proton MRS metabolite levels may be potential biomarkers for early diagnosis of dementia-related pathologic changes in the brain.
    Preview · Article · May 2013 · Neuropsychiatric Disease and Treatment
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    • "Clinically defined normal, MCI, and AD patients (MMSE normal = 28–30, MCI = 23–27, AD < 23) was accompanied by reduction in NAA/mI (−36% ± 0.05; P = 0.01) as previously described.5 "
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    ABSTRACT: We applied (13)C magnetic resonance spectroscopy (MRS), a nonradioactive, noninvasive brain imaging technique, to quantify the oxidation of [1-(13)C] acetate in a conventional clinical magnetic resonance imaging (MRI) scanner in five consecutive elderly subjects at various clinical stages of Alzheimer's disease (AD) progression. [1-(13)C] acetate entered the brain and was metabolized to [5-(13)C] glutamate and glutamine, as well as [1-(13)C] glutamate and glutamine, and the final glial oxidation product, (13)C bicarbonate, at a linear rate. Calculation of the initial slope was similar in a single subject, examined twice, 1 month apart (test-re-test 8%). Mean rate of cerebral bicarbonate production in this elderly group was 0.040 ± 0.01 (n = 5). Assuming that the rate of conversion of acetate to bicarbonate is a reflection of glial metabolic rate and that glial metabolic rate is a surrogate marker for 'neuroinflammation', our preliminary results suggest that [1-(13)C] MRS may provide biomarkers for diseases, believed to involve microglia and other cells of the astrocyte series. Among these is AD, for which novel drugs which ameliorate the damaging effects of neuroinflammation before symptoms of dementia appear, are in advanced development. The value of (13)C MRS as an early, noninvasive biomarker may lie in the conduct of cost-effective clinical trials.
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