As the population ages due to demographic trends and gains in life expectancy, the incidence and prevalence of dementia increases, and the need to understand the etiology and pathogenesis of dementia ...becomes ever more urgent. Alzheimer's disease (AD), the most common form of dementia, is a complex disease, the mechanisms of which are poorly understood. The more we learn about AD, the more questions are raised about our current conceptual models of disease. In the absence of a cure or the means by which to slow disease progress, it may be prudent to apply our current knowledge of the intersection between AD, cardiovascular disease, and cerebrovascular disease to foster efforts to delay or slow the onset of AD. This review discusses our current understanding of the epidemiology, genetics, and pathophysiology of AD, the intersection between AD and vascular causes of dementia, and proposes future directions for research and prevention.
We conducted a 27-month longitudinal study of mid-life adults with preclinical Alzheimer's disease (AD), using spectral domain optical coherence tomography to compare changes in volume and thickness ...in all retinal neuronal layers to those of age-matched healthy control subjects.
Fifty-six older adults (mean age = 65.36 years) with multiple risk factors for AD completed spectral domain optical coherence tomography retinal imaging and cognitive testing at baseline. Twenty-seven months later, they completed the same examinations and an 18F-florbetapir positron emission tomography imaging study.
Compared to healthy control subjects, those in the preclinical stage of AD showed a significant decrease in macular retinal nerve fiber layer (mRNFL) volume, over a 27-month follow-up interval period, as well as a decrease in outer nuclear layer and inner plexiform layer volumes and thickness in the inferior quadrant. However, only the mRNFL volume was linearly related to neocortical positron emission tomography amyloid standardized uptake value ratio after controlling for any main effects of age (R2 = 0.103; ρ = 0.017). Furthermore, the magnitude of mRNFL volume reduction was significantly correlated with performance on a task of participants' abilities to efficiently integrate visual and auditory speech information (McGurk effect).
We observed a decrease in mRNFL, outer nuclear layer, and inner plexiform layer volumes, in preclinical AD relative to controls. Moreover, the largely myelinated axonal loss in the RNFL is related to increased neocortical amyloid-β accumulation after controlling for age. Volume loss in the RNFL, during the preclinical stage, is not related to performance on measures of episodic memory or problem solving. However, this retinal change does appear to be modestly related to relative decrements in performance on a measure of audiovisual integration efficiency that has been recently advanced as a possible early cognitive marker of mild cognitive impairment.
Abstract Introduction In patients with Alzheimer's disease (AD) and mild cognitive impairment, structural changes in the retina (i.e., reduced thicknesses of the ganglion cell and retinal nerve fiber ...layers and inclusion bodies that appear to contain beta-amyloid protein Ab) have been previously reported. We sought to explore whether anatomic retinal changes are detectable in the preclinical stage of AD. Methods A cross-sectional study (as part of an ongoing longitudinal cohort study) involving 63 cognitively normal adults, all of whom have a parent with AD and subjective memory complaints. We compared neocortical amyloid aggregation (florbetapir PET imaging) to retinal spectral domain optical coherence tomography (SD-OCT) markers of possible disease burden. Retinal biomarkers, including the number and surface area of retinal inclusion bodies and the thickness of retinal neuronal layers, were compared across groups with high vs. low neocortical beta-amyloid load. Results The surface area of inclusion bodies increased as a function of cortical amyloid burden. Additionally, there was a trend toward a selective volume increase in the inner plexiform layer (IPL; a layer rich in cholinergic activity) of the retina in Aβ+ relative to Aβ− participants, and IPL volume was correlated with the surface area of retinal inclusion bodies. Discussion These initial results suggest that retinal imaging may be a potential cost-effective and noninvasive technique that can be used to identify those at-risk for AD. Layer-specific changes in the IPL and their association with surface area of inclusion bodies are discussed as a possible reflection of early inflammatory processes associated with cholinergic disruption and concurrent Ab accumulation in the neocortex.
Abstract Disruption in cholinergic neurotransmission is one of the earliest neuropathological changes in preclinical Alzheimer's disease (AD) and may be associated with abnormal beta-amyloid (Aβ) ...accumulation. Therefore, disruption of cholinergic neurotransmission with scopolamine may unmask otherwise undetectable cognitive deficits in preclinical AD. To compare the effects of low-dose (0.20 mg s.c.) scopolamine on cognition between Aβ+ and Aβ− cognitively normal (CN) older adults using the Groton Maze Learning Test (GMLT). CN older adults completed the GMLT predose and then received scopolamine (0.20 mg) subcutaneously. Participants were reassessed 1-, 3-, 5-, 7-, and 8-hours post dose. All participants underwent positron emission tomography neuroimaging for Aβ using18 F-florbetapir within 6 weeks of their baseline visit. Rhode Island Hospital Clinical Research Center, Providence, USA. CN older adults (n = 63), with a family history of AD and subjective memory complaints were enrolled (15 were classified as Aβ+ and 48 were classified as Aβ−). Cognition was assessed using the computerized GMLT at all predose and post-dose time points. At 5-hours post dose, the Aβ+ group performed significantly worse than the Aβ− group on all measures of learning efficiency and working memory and/or executive function (Cohen's d = 1.13–1.56). When participants were classified as having an abnormal response to scopolamine (based on change score at 5-hours post dose >0), 100% were correctly classified as Aβ+ and 67% as Aβ−. The results of this study suggest that diminished cholinergic tone likely occurs in preclinical AD, and as such, the use of a cholinergic stress test to perturb an already compromised neurotransmitter system may be an effective way of identifying CN older adults who are in this preclinical stage of AD.
Discontinuation and nonpublication of interventional clinical trials represents a waste of already scarce resources. We sought to identify the prevalence of discontinuation and nonpublication of ...interventional clinical trials conducted in patients afflicted by mild cognitive impairment and Alzheimer's disease.
We conducted a retrospective, cross-sectional study on mild cognitive impairment and Alzheimer's disease–based interventional clinical trials in ClinicalTrials.gov dating back to 1995. The analyzed data included trial phase, intervention type, enrollment, and funding sources. Fisher's exact and χ2 tests were used to determine any potential associations between trial characteristics and completion.
A total of 744 studies were identified, of which 502 (67%) were industry-sponsored ones. A total of 127 (17%) were discontinued prematurely. Of the 617 completed trials, 450 (73%) were not published, representing approximately 66,655 participants who incurred the risks of trial participation without subsequently contributing to the medical literature. Similarly, there were 18,246 patients from unpublished, discontinued trials. Of the 744 trials examined, 247 publications from 167 trials could be identified via PubMed/MEDLINE and EMBASE searches. Most notably, the odds of nonpublication among industry-sponsored trials were more than 75% higher than those in studies funded by academia (odds ratio = 1.78; 95% confidence interval, 1.14–2.78; P = .01). Furthermore, industry-sponsored trials had a 50% greater odds of study discontinuation compared with trials funded by academia (odds ratio = 1.50; 95% confidence interval, 1.04–2.16; P = .03).
The nonpublication of many trials and preliminary results of trials that are discontinued early dilutes the quality and decreases the comprehensive nature of the medical literature. This occurs in both industry and academia. Publication of inconclusive or negative results ensures that all research activities, regardless of outcome, contribute to global medical knowledge.
Modulation of Wnt signaling has untapped potential in regenerative medicine due to its essential functions in stem cell homeostasis. However, Wnt lipidation and Wnt-Frizzled (Fzd) cross-reactivity ...have hindered translational Wnt applications. Here, we designed and engineered water-soluble, Fzd subtype-specific “next-generation surrogate” (NGS) Wnts that hetero-dimerize Fzd and Lrp6. NGS Wnt supports long-term expansion of multiple different types of organoids, including kidney, colon, hepatocyte, ovarian, and breast. NGS Wnts are superior to Wnt3a conditioned media in organoid expansion and single-cell organoid outgrowth. Administration of Fzd subtype-specific NGS Wnt in vivo reveals that adult intestinal crypt proliferation can be promoted by agonism of Fzd5 and/or Fzd8 receptors, while a broad spectrum of Fzd receptors can induce liver zonation. Thus, NGS Wnts offer a unified organoid expansion protocol and a laboratory “tool kit” for dissecting the functions of Fzd subtypes in stem cell biology.
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•NGS Wnts activate Wnt signaling through targeted Frizzled subtype receptors•NGS Wnt supports expansion of multiple types of organoids•NGS Wnt supports single-cell-derived organoid outgrowth•NGS Wnts deconvolute Frizzled subtype receptor dependency in tissue homeostasis
Wnt is an essential cell growth factor used in organoid research. Miao et al. developed next-generation surrogate (NGS) Wnts that support organoid expansion, single-cell-derived organoid outgrowth, and long-term organoid maintenance. NGS Wnts also elicited systemic Wnt activation when administrated in vivo.
Background Abnormal beta-amyloid (Abeta) is associated with deleterious changes in central cholinergic tone in the very early stages of Alzheimer's disease (AD), which may be unmasked by a ...cholinergic antagonist (J Prev Alzheimers Dis 1:1-4, 2017). Previously, we established the scopolamine challenge test (SCT) as a "cognitive stress test" screening measure to identify individuals at risk for AD (Alzheimer's Dementia 10(2):262-7, 2014) (Neurobiol. Aging 36(10):2709-15, 2015). Here we aim to demonstrate the potential of the SCT as an indicator of cognitive change and neocortical amyloid aggregation after a 27-month follow-up interval. Methods Older adults (N = 63, aged 55-75 years) with self-reported memory difficulties and first-degree family history of AD completed the SCT and PET amyloid imaging at baseline and were then seen for cognitive testing at 9, 18, and 27 months post-baseline. Repeat PET amyloid imaging was completed at the time of the 27-month exam. Results Significant differences in both cognitive performance and in Abeta neocortical burden were observed between participants who either failed vs. passed the SCT at baseline, after a 27-month follow-up period. Conclusions Cognitive response to the SCT (Alzheimer's Dementia 10(2):262-7, 2014) at baseline is related to cognitive change and PET amyloid imaging results, over the course of 27 months, in preclinical AD. The SCT may be a clinically useful screening tool to identify individuals who are more likely to both have positive evidence of amyloidosis on PET imaging and to show measurable cognitive decline over several years. Keywords: Alzheimer disease, Preclinical Alzheimer's disease, Early detection, Cholinergic, Cognition, Biomarkers, Early diagnosis, Anticholinergic drugs, Scopolamine, Beta-amyloid protein
Abnormal beta-amyloid (Aβ) is associated with deleterious changes in central cholinergic tone in the very early stages of Alzheimer's disease (AD), which may be unmasked by a cholinergic antagonist ...(J Prev Alzheimers Dis 1:1-4, 2017). Previously, we established the scopolamine challenge test (SCT) as a "cognitive stress test" screening measure to identify individuals at risk for AD (Alzheimer's & Dementia 10(2):262-7, 2014) (Neurobiol. Aging 36(10):2709-15, 2015). Here we aim to demonstrate the potential of the SCT as an indicator of cognitive change and neocortical amyloid aggregation after a 27-month follow-up interval.
Older adults (N = 63, aged 55-75 years) with self-reported memory difficulties and first-degree family history of AD completed the SCT and PET amyloid imaging at baseline and were then seen for cognitive testing at 9, 18, and 27 months post-baseline. Repeat PET amyloid imaging was completed at the time of the 27-month exam.
Significant differences in both cognitive performance and in Aβ neocortical burden were observed between participants who either failed vs. passed the SCT at baseline, after a 27-month follow-up period.
Cognitive response to the SCT (Alzheimer's & Dementia 10(2):262-7, 2014) at baseline is related to cognitive change and PET amyloid imaging results, over the course of 27 months, in preclinical AD. The SCT may be a clinically useful screening tool to identify individuals who are more likely to both have positive evidence of amyloidosis on PET imaging and to show measurable cognitive decline over several years.
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