Faculty Bibliography
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The recency ratio is related to CSF Amyloid Beta 1-42 levels in MCI-AD
OBJECTIVE:As anti-amyloid therapeutic interventions shift from enrolling patients with Alzheimer's disease (AD) dementia to individuals with pre-clinical disease, the need for sensitive measures that allow for non-invasive, fast, disseminable and cost-effective identification of preclinical status increases in importance. The recency ratio (Rr) is a memory measure that relies on analysis of serial position performance, which has been found to predict cognitive decline and conversion to early mild cognitive impairment (MCI). The aim of this study was to test Rr's sensitivity to cerebrospinal fluid (CSF) levels of the core AD biomarkers in individuals with MCI-AD and controls. METHODS:Baseline data from 126 (110 controls and 16 MCI-AD) participants from the Wisconsin Alzheimer's Disease Research Center were analysed. Partial correlations adjusting for demographics were carried out between CSF measure of amyloid beta (Aβ40, Aβ42 and the 40/42 ratio) and tau (total and phosphorylated), and memory measures (Rr, delayed recall and total recall) derived from the Rey's Auditory Verbal Learning Test. RESULTS:Results indicated that Rr was the most sensitive memory score to Aβ42 levels in MCI-AD, while no memory score correlated significantly with any biomarker in controls. CONCLUSIONS:This study shows that Rr is a sensitive cognitive index of underlying Amyloid β pathology in MCI-AD.
PMID: 30430632
ISSN: 1099-1166
CID: 3457562
Pathological Increases in Neuronal Hyperactivity in Selective Cholinergic and Noradrenergic Pathways May Limit the Efficacy of Amyloid-β-Based Interventions in Mild Cognitive Impairment and Alzheimer's Disease
In spite of compelling evidence linking amyloid-β (Aβ) disturbances to the pathophysiology of Alzheimer's disease (AD), Aβ-based treatments have consistently failed to produce any beneficial effects both in mild cognitive impairment (MCI) and AD, even with successful reductions of toxic aggregated and soluble Aβ species. Before abandoning both the hypothesis and approach, there is a need to examine some overlooked factors that may have contributed to the lack of efficacy, such as the potential drug-induced increases in neuronal hyperactivity leading to adverse cognitive effects. In particular, we posit that selective cholinergic and noradrenergic pathways will be especially vulnerable to this adverse effect. If confirmed, this idea could help identify a potentially preventable and treatable obstacle for enhancing the efficacy of therapeutic agents in MCI and AD.
PMID: 30480259
ISSN: 2542-4823
CID: 3500562
The recency ratio as predictor of early MCI
ABSTRACTObjectives:Individuals with Alzheimer's disease (AD) present poor immediate primacy recall accompanied by intact or exaggerated recency, which then tends to decline after a delay. Bruno et al. (Journal of Clinical and Experimental Neuropsychology, Vol. 38, 2016, pp. 967-973) have shown that higher ratio scores between immediate and delayed recency (i.e. the recency ratio; Rr) are associated with cognitive decline in high-functioning older individuals. We tested whether Rr predicted conversion to early mild cognitive impairment (early MCI) from a cognitively healthy baseline.
PMID: 29667564
ISSN: 1741-203x
CID: 3056222
18F-florbetapir Positron Emission Tomography-determined Cerebral beta-Amyloid Deposition and Neurocognitive Performance after Cardiac Surgery
BACKGROUND:Amyloid deposition is a potential contributor to postoperative cognitive dysfunction. The authors hypothesized that 6-week global cortical amyloid burden, determined by F-florbetapir positron emission tomography, would be greater in those patients manifesting cognitive dysfunction at 6 weeks postoperatively. METHODS:Amyloid deposition was evaluated in cardiac surgical patients at 6 weeks (n = 40) and 1 yr (n = 12); neurocognitive function was assessed at baseline (n = 40), 6 weeks (n = 37), 1 yr (n = 13), and 3 yr (n = 9). The association of 6-week amyloid deposition with cognitive dysfunction was assessed by multivariable regression, accounting for age, years of education, and baseline cognition. Differences between the surgical cohort with cognitive deficit and the Alzheimer's Disease Neuroimaging Initiative cohorts (normal and early/late mild cognitive impairment) was assessed, adjusting for age, education, and apolipoprotein E4 genotype. RESULTS:The authors found that 6-week abnormal global cortical amyloid deposition was not associated with cognitive dysfunction (13 of 37, 35%) at 6 weeks postoperatively (median standard uptake value ratio [interquartile range]: cognitive dysfunction 0.92 [0.89 to 1.07] vs. 0.98 [0.93 to 1.05]; P = 0.455). In post hoc analyses, global cortical amyloid was also not associated with cognitive dysfunction at 1 or 3 yr postoperatively. Amyloid deposition at 6 weeks in the surgical cohort was not different from that in normal Alzheimer's Disease Neuroimaging Initiative subjects, but increased over 1 yr in many areas at a rate greater than in controls. CONCLUSIONS:In this study, postoperative cognitive dysfunction was not associated with 6-week cortical amyloid deposition. The relationship between cognitive dysfunction and regional amyloid burden and the rate of postoperative amyloid deposition merit further investigation.
PMCID:5849499
PMID: 29389750
ISSN: 1528-1175
CID: 2994312
The recency ratio is associated with reduced CSF glutamate in late-life depression
Glutamate is the principal excitatory neurotransmitter in the central nervous system, and is thought to be involved in the process of memory encoding and storage. Glutamate disturbances have also been reported in psychiatric disorders, such as schizophrenia and major depressive disorder (MDD), and in Alzheimer's disease. In this paper, we set out to study the relationship between cerebrospinal fluid (CSF) glutamate levels and memory performance, which we believe has not been reported previously. In particular, we focused on recall performance broken down by serial position. Our prediction was that the recency ratio (Rr), a novel cognitive marker of intellectual impairment, would be linked with CSF glutamate levels. We studied data from a group of cognitively intact elderly individuals, 28 of whom had MDD, while 19 were controls. Study results indicated that Rr levels, but no other memory score, were inversely correlated with CSF glutamate levels, although this was found only in individuals with late-life MDD. For comparison, glutamine or GABA were not correlated with any memory performance measure.
PMCID:5460071
PMID: 28323201
ISSN: 1095-9564
CID: 3080692
Reduction in CSF STREM2, a biomarker of microglia activation, in elderly depressives [Meeting Abstract]
Background: Both intense microglia activation and senescence, which respectively lead to marked and reduced inflammatory responses, have each been implicated in the etiology of depression. However, to date, results from postmortem and PET studies of microglial status have been negative or inconclusive, perhaps reflecting the heterogeneity of microglia dysfunction in this disorder, and the lack of specificity of the neuroimaging ligands for microglia. Triggering receptor expressed on myeloid cells 2 (TREM2) is a transmembrane innate immune receptor of the immunoglobulin family; in brain, it is found exclusively on microglia. TREM2 variants have been associated with increased risk for AD and other degenerative disorders. It undergoes proteolytic cleavage generating a soluble form (sTREM2), found in CSF, and emerging data suggest that its levels may reflect microglia activation. These considerations prompted us to determine if elderly cognitively-intact individuals with a DSM-IV diagnosis of late-life major depression (LLMD) differ from healthy controls with respect to CSF sTREM2 and its relationship to depressive symptoms. Additionally, because of the association between depression and increased risk for AD, we also determined its relationship to CSF AD biomarkers. Methods: CSF was obtained from 47 older subjects with intact cognition having an MMSE score of at least 28 and no gross MRI abnormalities other than white matter hyperintensities (28 LLMDs, 19 Healthy controls). CSF sTREM2 was determined using an electrochemiluminescence immunoassay. Severity of depression was determined at the baseline and screening visits using the HAM-D. Results: CSF sTREM2 was significantly (p<.05) reduced in LLMD compared to controls. CSF sTREM2 was significantly (negatively) correlated with baseline HAM-D scores in the entire sample and in the depressed group separately. As previously reported in cognitively-intact populations, CSF sTREM2 was significantly (positively) correlated with CSF Abeta42, Abeta40, tau and p-tau. Antidepressant treatment and APOE-e4 status had no effect on CSF sTREM2. Conclusions: The reduction in CSF sTREM2 level in LLMD and its association with more depressive symptoms suggest that decreased rather than increased microglia activation may contribute to the pathophysiology of this disorder. Future studies should determine how lower CSF sTREM2 levels may relate to activated M1 (pro-inflammatory) or M2 (anti-inflammatory) microglia phenotypes and to inflammatory and AD brain PET biomarkers
EMBASE:619901231
ISSN: 1740-634x
CID: 2955442
Increased levels of ascorbic acid in the cerebrospinal fluid of cognitively intact elderly patients with major depression: a preliminary study
Major depressive disorder (MDD) in the elderly is a risk factor for dementia, but the precise biological basis remains unknown, hampering the search for novel biomarkers and treatments. In this study, we performed metabolomics analysis of cerebrospinal fluid (CSF) from cognitively intact elderly patients (N = 28) with MDD and age- and gender-matched healthy controls (N = 18). The CSF levels of 177 substances were measured, while 288 substances were below the detection limit. Only ascorbic acid was significantly different, with higher levels in the MDD group at baseline. There were no correlations between CSF ascorbic acid levels and clinical variables in MDD patients at baseline. At the 3-year follow-up, there was no difference of CSF ascorbic acid levels between the two groups. There was a negative correlation between CSF ascorbic acid and CSF amyloid-beta42 levels in all subjects. However, there were no correlations between ascorbic acid and other biomarkers (e.g., amyloid-beta40, total and phosphorylated tau protein). This preliminary study suggests that abnormalities in the transport and/or release of ascorbic acid might play a role in the pathogenesis of late-life depression.
PMCID:5471282
PMID: 28615661
ISSN: 2045-2322
CID: 2593722
Basal forebrain mediated increase in brain CRF is associated with increased cholinergic tone and depression
PMID: 28477491
ISSN: 1872-7123
CID: 2548752
Selective and state-dependent changes in CSF abeta42 levels in cognitively-intact elderly with late life major depression [Meeting Abstract]
Background: Numerous studies have linked depressive symptoms, or syndromal depression, to increased risk for Alzheimer's disease (AD) irrespective of its onset age. The neurobiological basis for this association, however, remains poorly understood. Studies which have examined biomarkers of AD in peripheral and central tissues in depression, including CSF Abeta42 (Abeta42) and brain amyloid using PET ligands, have provided conflicting results. These discrepant results may have been due to methodological differences across studies, including heterogeneity in study populations (e.g., inclusion of individuals with mild cognitive impairment) and the use of approaches for detecting depression (e.g., patients' self-ratings) that lack diagnostic specificity. In addition, only a few studies have employed structured interviews based on DSM diagnostic criteria or standardized pre-analytical and laboratory procedures for quantifying Abeta. Finally, all of the existing studies have been limited to cross sectional comparisons based on a single Abeta determination; thus, it is not known if these abnormalities persist over time and if depressive symptoms influence Abeta levels. The current study was conducted to address the aforementioned limitations. Methods: Our baseline sample consisted of 47 subjects aged 60 years and older; 28 with LMDD and 19 controls. Of the 47 older subjects, 31 were e4 non-carriers and 16 were e4 carriers. All subjects were cognitively-intact and had a) no evidence of dementia, b) a Mini-Mental State Exam score of at least 28, and c) no gross MRI abnormalities other than white matter hyperintensities. CSF collection was repeated after 3 years for 36 of these individuals: 19 with LLMD and 17 controls. We evaluated the effects of diagnosis and time on Abeta42 levels with 2 x 2 repeated measures ANOVA. Results: Longitudinal comparisons of controls and LLMD revealed that the LLMD group was significantly less depressed at follow up than at baseline, as determined by the HAM-D, whereas controls remained unchanged. There was a significant interaction between diagnosis and time on CSF Abeta42 levels. Importantly, the reductions in depressive symptoms observed over time were significantly correlated with increases in CSF Abeta42 levels, both in the entire cohort (r =-.451, p =.006) and within the LLMD group (r =-.547, p =.015), but not in the control group (p =.809). The same relationship was not significant with Abeta40 (Pomara et al., 2016). Performance on cognitive indices remained unchanged and was not significantly correlated with changes in AD Biomarkers. Conclusions: Cognitively-intact, elderly individuals with LLMD, who were more depressed at baseline, but less depressed at the 3 year follow-up, showed both a reduction in baseline CSF Abeta42 (Pomara et al., 2012) and elevation in Abeta42 at 3 year follow-up. In addition, changes in CSF Abeta42 were correlated with changes in depressive symptoms. Future studies should determine if these state-dependent changes in Abeta42 mediate the increased risk of AD contributed by LLMD. If this is the case, the need for more aggressive treatment of LLMD cannot be underestimated
EMBASE:613896606
ISSN: 1740-634x
CID: 2397672
The Primacy Effect in Amnestic Mild Cognitive Impairment: Associations with Hippocampal Functional Connectivity
Background: The "primacy effect," i.e., increased memory recall for the first items of a series compared to the following items, is reduced in amnestic mild cognitive impairment (aMCI). Memory task-fMRI studies demonstrated that primacy recall is associated with higher activation of the hippocampus and temporo-parietal and frontal cortical regions in healthy subjects. Functional magnetic resonance imaging (fMRI) at resting state revealed that hippocampus functional connectivity (FC) with neocortical brain areas, including regions of the default mode network (DMN), is altered in aMCI. The present study aimed to investigate whether resting state fMRI FC between the hippocampus and cortical brain regions, especially the DMN, is associated with primacy recall performance in aMCI. Methods: A number of 87 aMCI patients underwent resting state fMRI and verbal episodic memory assessment. FC between the left or right hippocampus, respectively, and all other voxels in gray matter was mapped voxel-wise and used in whole-brain regression analyses, testing whether FC values predicted delayed primacy recall score. The delayed primacy score was defined as the number of the first four words recalled on the California Verbal Learning Test. Additionally, a partial least squares (PLS) analysis was performed, using DMN regions as seeds to identify the association of their functional interactions with delayed primacy recall. Results: Voxel-based analyses indicated that delayed primacy recall was mainly (positively) associated with higher FC between the left and right hippocampus. Additionally, significant associations were found for higher FC between the left hippocampus and bilateral temporal cortex, frontal cortical regions, and for higher FC between the right hippocampus and right temporal cortex, right frontal cortical regions, left medial frontal cortex and right amygdala (p < 0.01, uncorr.). PLS analysis revealed positive associations of delayed primacy recall with FC between regions of the DMN, including the left and right hippocampus, as well as middle cingulate cortex and thalamus (p < 0.04). In conclusion, in the light of decreased hippocampus function in aMCI, inter-hemispheric hippocampus FC and hippocampal FC with brain regions predominantly included in the DMN may contribute to residual primacy recall in aMCI.
PMCID:5073133
PMID: 27818633
ISSN: 1663-4365
CID: 2312392
