Profiles of Alzheimer's disease-related pathology in an aging urban population sample in India

Types of memory, dementia, Alzheimer's disease, and their various pathological cascades as targets for potential pharmacological drugs

Alzheimer's disease (AD) is the most common type of dementia accounting for 90% of cases; however, frontotemporal dementia, vascular dementia, etc. prevails only in a minority of populations. The term dementia is defined as loss of memory which further takes several other categories of memories like working memory, spatial memory, fear memory, and long-term, and short-term memory into consideration. In this review, these memories have critically been elaborated based on context, duration, events, appearance, intensity, etc. The most important part and purpose of the review is the various pathological cascades as well as molecular levels of targets of AD, which have extracellular amyloid plaques and intracellular hyperphosphorylated tau protein as major disease hallmarks. There is another phenomenon that either leads to or arises from the above-mentioned hallmarks, such as oxidative stress, mitochondrial dysfunction, neuroinflammation, cholinergic dysfunction, and insulin resistance. Several potential drugs like antioxidants, anti-inflammatory drugs, acetylcholinesterase inhibitors, insulin mimetics or sensitizers, etc. studied in various previous preclinical or clinical reports were put as having the capacity to act on these pathological targets. Additionally, agents directly or indirectly targeting amyloid and tau were also discussed. This could be further investigated in future research.

Circle of Willis abnormalities and their clinical importance in ageing brains: A cadaveric anatomical and pathological study

The circle of Willis (CW) located at the base of the brain forms an important collateral network to maintain adequate cerebral perfusion, especially in clinical situations requiring compensatory changes in blood flow. Morphopathological changes in the CW may relate to the severity of the symptoms of certain neurodegenerative and cerebrovascular disorders. The purpose of this study was to investigate the CW abnormalities and their clinical importance in ageing brains. The CW was examined macroscopically in 73 formalin-fixed samples to determine the degree of stenosis of each CW component, atherosclerosis of the CW, hypoplasia (threshold diameter < 1 mm), anatomical variations and aneurysms. Age-related neurodegenerative and cerebrovascular pathologies were screened using immunohistopathological techniques on specific neuroanatomical regions based on standard guidelines. The majority of the elderly brains -93 % (68/73) presented at least a single hypoplastic CW component at death. Anatomical variations were mostly identified in communicating arteries, followed by proximal posterior and anterior cerebral arteries. Arterial bifurcations were found to be the predominant sites for cerebral aneurysms. More than 90 % of the elderly brains presented CW atherosclerosis at death. CW abnormalities did not show any strong associations with neurodegenerative pathologies except for an "at risk" significant association observed between Braak's neurofibrillary tangle (NFT) stages 1-VI and CW atherosclerosis grades ≥ mild (p = 0.05). However, a significant association was observed between microscopic infarcts in deep white matter and hypoplasia in communicating arteries with Fisher's exact test (p < 0.05). Overall, CW abnormalities were predominant in the ageing brains, however their relationships to the occurrence and severity of the symptoms of neurodegenerative pathologies were found to be low.

The Shrinking Brain: Cerebral Atrophy Following Traumatic Brain Injury

Cerebral atrophy in response to traumatic brain injury is a well-documented phenomenon in both primary investigations and review articles. Recent atrophy studies focus on exploring the region-specific patterns of cerebral atrophy; yet, there is no study that analyzes and synthesizes the emerging atrophy patterns in a single comprehensive review. Here we attempt to fill this gap in our current knowledge by integrating the current literature into a cohesive theory of preferential brain tissue loss and by identifying common risk factors for accelerated atrophy progression. Our review reveals that observations for mild traumatic brain injury remain inconclusive, whereas observations for moderate-to-severe traumatic brain injury converge towards robust patterns: brain tissue loss is on the order of 5% per year, and occurs in the form of generalized atrophy, across the entire brain, or focal atrophy, in specific brain regions. The most common regions of focal atrophy are the thalamus, hippocampus, and cerebellum in gray matter and the corpus callosum, corona radiata, and brainstem in white matter. We illustrate the differences of generalized and focal gray and white matter atrophy on emerging deformation and stress profiles across the whole brain using computational simulation. The characteristic features of our atrophy simulations-a widening of the cortical sulci, a gradual enlargement of the ventricles, and a pronounced cortical thinning-agree well with clinical observations. Understanding region-specific atrophy patterns in response to traumatic brain injury has significant implications in modeling, simulating, and predicting injury outcomes. Computational modeling of brain atrophy could open new strategies for physicians to make informed decisions for whom, how, and when to administer pharmaceutical treatment to manage the chronic loss of brain structure and function.

Top-Down Projections Direct the Gradual Progression of Alzheimer-Related Tau Pathology Throughout the Neocortex

In sporadic Alzheimer's disease (sAD), tau pathology gradually but relentlessly progresses from the transentorhinal region of the temporal lobe into both the allocortex and temporal high order association areas of the neocortex. From there, it ultimately reaches the primary sensory and motor fields of the neocortex. The brunt of the changes seen during neurofibrillary stages (NFT) I-VI is borne by top-down projection neurons that contribute to cortico-cortical connectivities between different neocortical fields. Very early changes develop in isolated pyramidal cells in layers III and V, and these cells are targets of top-down projections terminating in association areas of the first temporal gyrus or in peristriate regions of the occipital lobe. Neurofibrillary pathology in these regions is routinely associated with late NFT stages. Sequential changes occur in different cell compartments (dendritic, somatic, axonal) of these early-involved neurons. Tau pathology first develops in distal segments of basal dendrites, then in proximal dendrites, the soma, and, finally, in the axon of affected pyramidal neurons. This sequence of abnormal changes supports the concept that axons of cortico-cortical top-down neurons may carry and spread abnormal tau seeds in a focused manner (transsynaptically) into the distal dendritic segments of nerve cells directly following in the neuronal chain, thereby sustaining tau-seeded templating in sAD.

Vascular Contributions in Alzheimer's Disease-Related Neuropathological Changes: First Autopsy Evidence from a South Asian Aging Population

BACKGROUND

Evidence from various consortia on vascular contributions has been inconsistent in determining the etiology of sporadic Alzheimer's disease (AD).

OBJECTIVE

To investigate vascular risk factors and cerebrovascular pathologies associated in manifestation of AD-related neuropathological changes of an elderly population.

METHODS

Postmortem brain samples from 76 elderly subjects (≥50 years) were used to study genetic polymorphisms, intracranial atherosclerosis of the circle of Willis (IASCW), and microscopic infarcts in deep white matters. From this cohort, 50 brains (≥60 years) were subjected to neuropathological diagnosis using immunohistopathological techniques.

RESULTS

Besides the association with age, the apolipoprotein E ɛ4 allele was significantly and strongly associated with Thal amyloid-β phases ≥1 [odds ratio (OR) = 6.76, 95% confidence interval (CI) 1.37-33.45] and inversely with Braak neurofibrillary tangle (NFT) stages ≥III (0.02, 0.0-0.47). Illiterates showed a significant positive association for Braak NFT stages ≥IV (14.62, 1.21-176.73) and a significant negative association for microscopic infarcts (0.15, 0.03-0.71) in deep white matters. With respect to cerebrovascular pathologies, cerebral small vessel lesions (white matter hyperintensities and cerebral amyloid angiopathy) showed a higher degree of associations among them and with AD-related neuropathological changes (p < 0.05) compared to large vessel pathology (IASCW), which showed a significant association only with Braak NFT stages ≥I (p = 0.050).

CONCLUSION

These findings suggest that besides age, education, and genetic factors, other vascular risk factors were not associated with AD-related neuropathological changes and urge prompt actions be taken against cerebral small vessel diseases since evidence for effective prevention is still lacking.

Early stages of Alzheimer's disease are alarming signs in injury deaths caused by traffic accidents in elderly people (≥60 years of age): A neuropathological study

BACKGROUND

There is little information available in the literature concerning the contribution of dementia in injury deaths in elderly people (≥60 years).

AIM

This study was intended to investigate the extent of dementia-related pathologies in the brains of elderly people who died in traffic accidents or by suicide and to compare our findings with age- and sex-matched natural deaths in an elderly population.

MATERIALS AND METHODS

Autopsy-derived human brain samples from nine injury death victims (5 suicide and 4 traffic accidents) and nine age- and sex-matched natural death victims were screened for neurodegenerative and cerebrovascular pathologies using histopathological and immunohistochemical techniques. For the analysis, Statistical Package for the Social Sciences (SPSS) version 16.0 was used.

RESULTS

There was a greater likelihood for Alzheimer's disease (AD)-related changes in the elders who succumbed to traffic accidents (1 out of 4) compared to age- and sex-matched suicides (0 out of 5) or natural deaths (0 out of 9) as assessed by the National Institute on Aging - Alzheimer's Association guidelines. Actual burden of both neurofibrillary tangles (NFTs) and (SPs) was comparatively higher in the brains of traffic accidents, and the mean NFT counts were significantly higher in the region of entorhinal cortex (P < 0.05). However, associations obtained for other dementia-related pathologies were not statistically important.

CONCLUSION

Our findings suggest that early Alzheimer stages may be a contributing factor to injury deaths caused by traffic accidents in elderly people whereas suicidal brain neuropathologies resembled natural deaths.

The Epidemiological Scale of Alzheimer's Disease

Alzheimer's disease (AD) has increased from a few cases in a country at the beginning of the 20th century to an incidence of recording a case every 7 seconds in the world. From a rare disease it has reached the top 8 of major health problems in the world. One of the epidemiological problems of AD is the fact that authors from different countries use different reporting units. Some report numbers to 100,000 inhabitants, others to 1,000 inhabitants and others report the total number of cases in a country. Standardization of these reports is strictly necessary. The rise in incidence and prevalence with age is known, but interesting to see is that the incidence and prevalence do not rise in a parallel manner with age as simple logic would assume. Between the ages of 60 and 90, the incidence in men increases two times and in women 41 times, prevalence increase in men is 55.25-fold and in women 77-fold. Regarding the women/men ratio, the incidence is 20.5-fold increased, and prevalence is merely 1.3936-fold increased. These numbers raise concerns about the evolution of the disease. Regarding mild cognitive impairment (MCI)/AD ratio, only about 1 in 2 people get AD (raising?) issues about the pathogenic disease relatedness.

New treatment strategies for Alzheimer's disease: is there a hope?

Alzheimer's disease (AD) is a progressive and irreversible neurodegenerative disease, and corresponds to the most common cause of dementia worldwide. Although not fully understood, the pathophysiology of AD is largely represented by the neurotoxic events triggered by the beta-amyloid cascade and by cytoskeletal abnormalities subsequent to the hyperphosphorylation of microtubule-associated Tau protein in neurons. These processes lead respectively to the formation of neuritic plaques and neurofibrillary tangles, which are the pathological hallmarks of the disease. Clinical benefits of the available pharmacological treatment for AD with antidementia drugs (namely cholinesterase inhibitors and memantine) are unquestionable, although limited to a temporary, symptomatic support to cognitive and related functions. Over the past decade, substantial funding and research have been dedicated to the search and development of new pharmaceutical compounds with disease-modifying properties. The rationale of such approach is that by tackling key pathological processes in AD it may be possible to attenuate or even change its natural history. In the present review, we summarize the available evidence on the new therapeutic approaches that target amyloid and Tau pathology in AD, focusing on pharmaceutical compounds undergoing phase 2 and phase 3 randomized controlled trials.

Traumatic brain injury, neuroimaging, and neurodegeneration

Depending on severity, traumatic brain injury (TBI) induces immediate neuropathological effects that in the mildest form may be transient but as severity increases results in neural damage and degeneration. The first phase of neural degeneration is explainable by the primary acute and secondary neuropathological effects initiated by the injury; however, neuroimaging studies demonstrate a prolonged period of pathological changes that progressively occur even during the chronic phase. This review examines how neuroimaging may be used in TBI to understand (1) the dynamic changes that occur in brain development relevant to understanding the effects of TBI and how these relate to developmental stage when the brain is injured, (2) how TBI interferes with age-typical brain development and the effects of aging thereafter, and (3) how TBI results in greater frontotemporolimbic damage, results in cerebral atrophy, and is more disruptive to white matter neural connectivity. Neuroimaging quantification in TBI demonstrates degenerative effects from brain injury over time. An adverse synergistic influence of TBI with aging may predispose the brain injured individual for the development of neuropsychiatric and neurodegenerative disorders long after surviving the brain injury.

Dementia and lower blood pressure in Latin America, India, and China: a 10/66 cross-cohort study

OBJECTIVE

To study the relationship between dementia and blood pressure (BP) in 8 low- and middle-income countries.

METHODS

In identical cross-sectional surveys of older adults (aged 65 years and older) conducted in Cuba, Dominican Republic, Peru, Venezuela, Mexico, Puerto Rico, China, and India (n = 15,746), we measured systolic and diastolic BP and used the 10/66 prevalidated algorithms to adjudicate dementia diagnosis and quantify dementia severity (Clinical Dementia Rating [CDR]).

RESULTS

BP levels, dementia prevalence, and participants' sociodemographic and health characteristics varied across sites. In fixed-effect meta-analyses of site-specific linear regression coefficients adjusted for potential confounders, dementia and CDR were cross-sectionally associated with lower systolic BP (β = -1.7, 95% confidence interval [CI]: -2.8, -0.6; and β = -1.1, 95% CI: -1.5, -0.7) and diastolic BP (β = -0.4, 95% CI: -1.1, 0.2; and β = -0.4, 95% CI: -0.7, -0.2). Associations were heterogeneous across sites for both dementia (I(2) < 47%) and CDR (I(2) < 75%), and were strongest in Cuba, where prevalence of hypertension was highest. Results were robust to alternative model specifications that accounted for hypertensive status, antihypertensive treatment, and leanness (i.e., smaller waist circumference).

CONCLUSION

The association between dementia and lower BP was heterogeneous across geographically diverse samples, strongest where prevalent hypertension was highest (in Cuba), and relatively small compared with that found in Western settings. Both the mechanisms and the extent to which different levels of lifetime hypertensive disease explain this heterogeneity remain uncertain. However, because rapid increments in both dementia and hypertension are predicted in low- and middle-income countries, closer monitoring is warranted.

Characterizing cognitive deficits and dementia in an aging urban population in India

Rapid rise in the population of older adults in India will lead to the need for increased health care services related to diagnosis, management, and long-term care for those with dementia and cognitive impairment. A direct approach for service provision through memory clinics can be an effective, successful, and sustaining means of delivering specialized health care services. We have established a memory clinic in Mumbai, India by employing the diverse clinical skills available in Indian academic institutions, diagnostic and research expertise of clinicians and psychologists, and the support of the U.S. National Institutes of Health. Our project involved recruitment of patients, clinical and neuropsychological assessment, and standardized diagnostic procedures, demonstrating the feasibility of using research methods to develop a memory clinic. In this paper, we describe the development of a community-based memory clinic in urban India, including linguistic and cultural factors and present detailed results, including diagnostic characterization, on 194 subjects with various stages of cognitive deficits. Our findings support the feasibility of developing a memory clinic in a public hospital and successful use of research diagnostic criteria to categorize cognitive deficits observed in this population, which may be used to inform the development of other such clinics.

Subtypes of dementia: a study from a memory clinic in India

BACKGROUND

The clinical syndrome of dementia consists of several subtypes that are distinct in their etiology, clinical profile, management, and outcome. Limited specialized services are available for dementia patients in India. We report the profile of dementia subtypes from a clinic-based dementia registry in India.

METHODS

Consecutive dementia patients were investigated with clinical evaluation, neuropsychological tests modified for local use, and brain imaging.

RESULTS

In 347 consecutive dementia patients, Alzheimer's disease was the most common subtype of dementia (38.3%), followed by a high proportion of vascular dementia (25.4%). Frontotemporal dementia syndromes were not uncommon (18.7%). Dementia with Lewy bodies was encountered in 8.9% of the patients, and mixed dementia was found in 8.6%. The mean age of the group at presentation was 66.3 years, nearly a decade younger than in developed countries. The proportion of patients with early-onset dementia was high (49.9%).

CONCLUSIONS

Our results demonstrate that the clinical profiles of dementia subtypes in a clinic population are influenced by the population's demographic profile, cardiovascular risk factor burden, sociocultural attitudes about cognitive impairment, and possibly genetic factors.