An early and accurate diagnosis of Alzheimer’s Disease (AD) has loaded benefits for a patient living with the disease and their families. Getting an accurate diagnosis has been a challenge for many decades due to the limitations in medical resources available for testing.

Historically, an AD diagnosis was only confirmed on autopsy by elevated levels of beta-amyloid and tau in the brain. Over the years, however, there have been ongoing medical breakthroughs to test, prevent, and slow the progression of AD.

These publications below chronicle the evolution of these breakthroughs and how the innovative biomarkers have significantly changed the testing and diagnosis of AD.

Alzheimer dementia with sparse amyloid–AD mimic or variant?

In a new study, one-quarter of individuals with clinical diagnosis of mild to moderate Alzheimer dementia had no or only sparse neuritic amyloid plaques in their brains, and most were also at low or intermediate neurofibrillary tangle stage. The findings have enormous implications for clinical trails of anti-amyloid ant anti-tau therapies.

Author of publication: Alberto Serrano-Pozo and Bradley T. Hyman
Date of publication: 10/11/2015

Early diagnostic accuracy and pathophysiologic relevance of an autopsy-confirmed Alzheimer’s disease peripheral biomarker

Treatment of Alzheimer’s disease (AD) and the discovery of promising drug candidates depend on early diagnosis. Few currently available diagnostic tests have significantly improved this early uncertainty, while the “gold standard” diagnosis continues to require clinical dementia in life and the presence of pathologic brain lesions of amyloid plaques and neurofibrillary tangles in the brain at autopsy. Here, the inflammatory agonist bradykinin, a small nano-peptide, that induces PKC-mediated phosphorylation of Erk1 and Erk2 in fibroblasts, was applied to punch biopsy-obtained human skin fibroblasts. Quantitative imaging of the phosphorylated Erk1 and Erk2 bands was then used in a ratio that is mathematically configured into an AD-Biomarker Index (AD-Index). In the population described here (N= 264), there were 64 autopsy examinations. Demented individuals were clinically diagnosed as AD with an overall accuracy of 78%. Among the 42 autopsy-confirmed cases for which there were also AD-Biomarker measurements, the overall accuracy of the AD-Biomarker was 98%. Among both the autopsy confirmed and the clinically diagnosed patients, the AD-Index values were inversely correlated with the duration of disease, i.e., the time from the onset of dementia symptoms. Among the autopsy-confirmed cases, the AD-Biomarker diagnosis showed remarkably high sensitivity (97%) and specificity (100%) compared to clinical diagnosis (sensitivity: 78% and specificity: 20%). Using autopsy validation, the clinical diagnosis was only accurate at 52% level vs. the AD-Biomarker accuracy of 100% for cases with dementia not larger than 4 years of duration. Finally, application of soluble A1–42 to the fibroblasts of normal controls induced the abnormal AD-Biomarker phenotype, suggesting the pathophysiologic relevance of this AD-Biomarker measurement. In summary, the AD-Biomarker, as confirmed by autopsy validation, showed significantly higher sensitivity and specificity than did clinical diagnosis, particularly at early stages of disease, and pathophysiological relevance was demonstrated for the mechanistic basis of the AD-Biomarker measurements.

Author of publication: Tapan Kumar Khan a, Daniel L. Alkon
Date of publication: 11/07/2008

PKC Deficits in Alzheimer’s Disease Brains and Skin Fibroblasts

In Alzheimer’s disease (AD) transgenic mice, activation of synaptogenic protein kinase C  (PKC) was found to prevent synaptotoxic amyloid- (A)-oligomer elevation, PKC deficits, early synaptic loss, cognitive deficits, and amyloid plaque formation. In humans, to study the role of PKC in the pathophysiology of AD and to evaluate its possible use as an early AD-biomarker, we examined PKC and A in the brains of autopsy-confirmed AD patients (n = 20) and age-matched controls (AC, n = 19), and in skin fibroblast samples from AD (n = 14), non-AD dementia patients (n = 14), and AC (n = 22). Intraneuronal A levels were measured immunohistochemically (using an A-specific antibody) in hippocampal pyramidal cells of human autopsy brains. PKC was significantly lower in the hippocampus and temporal pole areas of AD brains, whereas A levels were significantly higher. The ratio of PKC to A in individual CA1 pyramidal cells was markedly lower in the autopsy AD brains versus controls. PKC was inversely correlated with A levels in controls, whereas in AD patients, PKC showed no significant correlation with A. In autopsy brains, PKC decreased as the Braak score increased. Skin fibroblast samples from AD patients also demonstrated a deficit in PKC compared to controls and an AD-specific change in the A-oligomer effects on PKC. Together, these data demonstrate that the relationship between A levels and PKC is markedly altered in AD patients’ brains and skin fibroblasts, reflecting a loss of protective effect of PKC against toxic A accumulation. These changes of PKC levels in human skin fibroblasts may provide an accurate, non-invasive peripheral AD biomarker.

Author of publication: Tapan K. Khan, Abhik Sen, Jarin Hongpaisan, Chol S. Lim, Thomas J. Nelson and Daniel L. Alkon
Date of publication: 16/06/2014

An internally controlled peripheral biomarker for Alzheimer’s disease: Erk1 and Erk2 responses to the inflammatory signal bradykinin

Cognitive impairment has recently been found to correlate with changes in peripheral inflammatory signals such as TNF- and IL-1. PKC isozymes regulate levels of TNF- and IL-6 and the release of other cytokines and also show deficits in Alzheimer’s disease (AD) brains and skin fibroblasts. Here, we investigate MAPK Erk1 and Erk2 phosphorylation in response to the inflammatory agonist bradykinin, which activates PKC pathways. An internally controlled comparison of Erk1 and Erk2 produced an AD index that accurately distinguished fibroblasts of AD from those of normal controls and of non-AD dementias. This accuracy was demonstrated for Coriell Cell Repository (Coriell Institute of Medical Research, Camden, NJ) samples, as well as for samples analyzed on gels with autopsy diagnostic confirmation. AD Erk1 and Erk2 index values were inversely correlated with disease duration, suggesting maximal efficacy for early diagnosis. Finally, the results also demonstrate that, when the AD index agreed with the clinical diagnosis on the presence of AD, there was a high probability of accuracy based on autopsy validation. Thus, this peripheral molecular biomarker, based on differential Erk1 and Erk2 phosphorylation, could have important clinical utility for providing increased certainty in the positive diagnosis of AD, particularly in the early phase of disease progression.

Author of publication: Tapan K. Khan and Daniel L. Alkon
Date of publication: 29/08/2006

Association of Cognitive Function Trajectories in Centenarians With Postmortem Neuropathology, Physical Health, and Other Risk Factors for Cognitive Decline

Some individuals reach ages beyond 100 years and become centenarians with intact cognitive functions,1-5 which indicates that cognitive impairment is not inevitable at extreme ages. Cross sectional and longitudinal studies in younger age groups (20-90 years) have shown that aging is accompanied by a maintenance in language, semantic knowledge, abstract reasoning, and visuospatial functions, whereas a vulnerability is observed in domains such as processing speed, executive functions, and episodic and working memory.6-11 It is still unclear to what extent individuals who maintain cognitive health until age 100 years escape or delay decline across different cognitive domains. Based on the 40% incidence of dementia at age 100 years, and assuming a continued increase beyond 100, it is to be expected that a decline in cognitive functions will be observable in this age group.12,13 In this study, we aim to identify trajectories of cognitive performance in different domains for cognitively healthy centenarians, and to explore associations with risk factors of cognitive decline, including neuropathology associated with Alzheimer disease (AD) and factors of cognitive reserve.

Author of publication: Nina Beker, PhD; Andrea Ganz, MSc; Marc Hulsman, PhD; Thomas Klausch, PhD; Ben A. Schmand, PhD; Philip Scheltens, MD, PhD
Date of publication: 15/01/2021

Soluble f-Amyloid Induction of Alzheimer’s Phenotype for Human Fibroblast K+ Channels

Although P-amyloid is the main constituent of neurite plaques and may play a role in the pathophysiology of Alzheimer’s disease, mechanisms by which soluble P-amyloid might produce early symptoms such as memory loss before diffuse plaque deposition have not been implicated. Treatment of fibroblasts with ,B-amyloid (10 nM) induced the same potassium channel dysfunction previously shown to occur specifically in fibroblasts from patients with Alzheimer’s disease-namely, the absence of a 1 1 3-picosiemen potassium channel. A tetraethylammonium-induced increase of intracellular concentrations of calcium, [Ca2+]i, a response that depends on functional 1 1 3-picosiemen potassium channels, was also eliminated or markedly reduced by 10 nM P-amyloid. Increased [Ca2+1] induced by high concentrations of extracellular potassium and 1 66-picosiemen potassium channels were unaffected by 10 nM p-amyloid. In Alzheimer’s disease, then, P-amyloid might alter potassium channels and thus impair neuronal function to produce symptoms such as memory loss by a means other than plaque formation.

Author of publication: Rene Etcheberrigaray, Etsuro Ito, Christopher S. Kim, Daniel L. Alkont
Date of publication: 08/04/1994

Fibroblast Aggregation Rate Converges with Validated Peripheral Biomarkers for Alzheimer’s Disease

The inaccuracy of the diagnosis for Alzheimer’s disease (AD) has made its therapeutic intervention difficult, particularly early enough to prevent significant neurodegeneration and cognitive dysfunction. Here, we describe a novel, highly accurate peripheral diagnostic for AD patients based on quantitatively measured aggregation rate of human skin fibroblasts. The elevated aggregation rate with increasing cell density in AD cases is the basis of this new biomarker. The new biomarker was successfully cross-validated with two more mature assays, AD-Index, based on the imbalances of ERK1/2, and Morphology, based on network dynamics, and showed 92% overlap. A significant number of cases tested with this new biomarker were freshly obtained (n = 29), and 82% of the cases are hyper-validated cases, i.e., autopsy and/or genetically confirmed AD or non-Alzheimer’s disease demented patients (Non-ADD) and non-demented age-matched controls. Furthermore, we show that by using a simple majority rule, i.e., two out of the three assays have the same outcome, we significantly increase the agreement with clinical AD diagnosis (100%). Based on the high accuracy of this strategy, the biomarker profile appears to accurately identify AD patients for therapeutic intervention.

Author of publication: Florin V. Chirila, Tapan K. Khan and Daniel L. Alkon
Date of publication: 08/05/2014

Spatiotemporal Complexity of Fibroblast Networks Screens for Alzheimer’s Disease

Drugs to treat Alzheimer’s disease (AD) have been unsuccessful in preventing its devastating cognitive deficits and progressive neurodegeneration. The lack of a definitive diagnostic for AD has been a major obstacle to AD drug discovery. Here, we describe a novel, highly accurate peripheral diagnostic for AD patients based on quantitatively measured complexity of skin-sampled fibroblast networks. A significant number of samples were studied under double-blind conditions and had autopsy and/or genetic validation. An additional sample confirmed the diagnostic discrimination on freshly obtained skin samples. A subsample of these diagnostic differences were induced by oligomerized amyloid-1-42. Based on the accuracy of these measures that utilize physical principles such as fractal dimension and lacunarity as well as the significant correlation with disease duration,this biomarker profile appears to identify accurately AD patients for therapeutic intervention.

Author of publication: Florin V. Chirila, Tapan K. Khan and Daniel L. Alkon
Date of publication: 18/07/2012