Cardiovascular system participation in Alzheimer's disease pathogenesis

Therapeutic roles of plants for 15 hypothesised causal bases of Alzheimer's disease

Alzheimer's disease (AD) is progressive and ultimately fatal, with current drugs failing to reverse and cure it. This study aimed to find plant species which may provide therapeutic bioactivities targeted to causal agents proposed to be driving AD. A novel toolkit methodology was employed, whereby clinical symptoms were translated into categories recognized in ethnomedicine. These categories were applied to find plant species with therapeutic effects, mined from ethnomedical surveys. Survey locations were mapped to assess how this data is at risk. Bioactivities were found of therapeutic relevance to 15 hypothesised causal bases for AD. 107 species with an ethnological report of memory improvement demonstrated therapeutic activity for all these 15 causal bases. The majority of the surveys were found to reside within biodiversity hotspots (centres of high biodiversity under threat), with loss of traditional knowledge the most common threat. Our findings suggest that the documented plants provide a large resource of AD therapeutic potential. In demonstrating bioactivities targeted to these causal bases, such plants may have the capacity to reduce or reverse AD, with promise as drug leads to target multiple AD hallmarks. However, there is a need to preserve ethnomedical knowledge, and the habitats on which this knowledge depends.

The Impact of Disease Registries on Advancing Knowledge and Understanding of Dementia Globally

To help address the increasing challenges related to the provision of dementia care, dementia registries have emerged around the world as important tools to gain insights and a better understanding of the disease process. Dementia registries provide a valuable source of standardized data collected from a large number of patients. This review explores the published research relating to different dementia registries around the world and discusses how these registries have improved our knowledge and understanding of the incidence, prevalence, risk factors, mortality, diagnosis, and management of dementia. A number of the best-known dementia registries with high research output including SveDem, NACC, ReDeGi, CREDOS and PRODEM were selected to study the publication output based on their data, investigate the key findings of these registry-based studies. Registries data contributed to understanding many aspects of the disease including disease prevalence in specific areas, patient characteristics and how they differ in populations, mortality risks, as well as the disease risk factors. Registries data impacted the quality of patients’ lives through determining the best treatment strategy for a patient based on previous patient outcomes. In conclusion, registries have significantly advanced scientific knowledge and understanding of dementia and impacted policy, clinical practice care delivery.

Dynamic Effects of Aortic Arch Stiffening on Pulsatile Energy Transmission to Cerebral Vasculature as A Determinant of Brain-Heart Coupling

Aortic stiffness increases with age and is a robust predictor of brain pathology including Alzheimer’s and other dementias. Aging causes disproportionate stiffening of the aorta compared with the carotid arteries, reducing protective impedance mismatches at their interface and affecting transmission of destructive pulsatile energy to the cerebral circulation. Recent clinical studies have measured regional stiffness within the aortic arch using pulse wave velocity (PWV) and have found a stronger association with cerebrovascular events than global stiffness measures. However, effects of aortic arch PWV on the transmission of harmful excessive pulsatile energy to the brain is not well-understood. In this study, we use an energy-based analysis of hemodynamic waves to quantify the effect of aortic arch stiffening on transmitted pulsatility to cerebral vasculature, employing a computational approach using a one-dimensional model of the human vascular network. Results show there exists an optimum wave condition—occurring near normal human heart rates—that minimizes pulsatile energy transmission to the brain. This indicates the important role of aortic arch biomechanics on heart-brain coupling. Our results also suggest that energy-based indices of pulsatility combining pressure and flow data are more sensitive to increased stiffness than using flow or pressure pulsatility indices in isolation.

Comparison of ferumoxytol-based cerebral blood volume estimates using quantitative R1 and R2* relaxometry

PURPOSE

Cerebral perfusion is commonly assessed clinically with dynamic susceptibility contrast MRI using a bolus injection of gadolinium-based contrast agents, resulting in semi-quantitative values of cerebral blood volume (CBV). Steady-state imaging with ferumoxytol allows estimation of CBV with the potential for higher precision and accuracy. Prior CBV studies have focused on the signal disrupting T2* effects, but ferumoxytol also has high signal-enhancing T₁ relaxivity. The purpose of this study was to investigate and compare CBV estimation using T₁ and T2*, with the goal of understanding the contrast mechanisms and quantitative differences.

METHODS

Changes in R₁ (1/T₁ ) and R2* (1/ T2*) were measured after the administration of ferumoxytol using high-resolution quantitative approaches. Images were acquired at 3.0T and R₁ was estimated from an ultrashort echo time variable flip angle approach, while R2* was estimated from a multiple gradient echo sequence. Twenty healthy volunteers were imaged at two doses. CBV was derived and compared from relaxometry in gray and white matter using different approaches.

RESULTS

R₁ measurements showed a linear dependence of blood R₁ with respect to dose in large vessels, in contrast to the nonlinear dose-dependence of blood R2* estimates. In the brain parenchyma, R2* showed linear dose-dependency whereas R₁ showed nonlinearity. CBV calculations based on R2* changes in tissue and ferumoxytol blood concentration estimates based on R₁ relaxivity showed the lowest variability in our cohort.

CONCLUSIONS

CBV measurements were successfully derived using a combined approach of R₁ and R2* relaxometry. Magn Reson Med 79:3072-3081, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Changes in intracranial venous blood flow and pulsatility in Alzheimer's disease: A 4D flow MRI study

Cerebral blood flow, arterial pulsation, and vasomotion may be important indicators of cerebrovascular health in aging and diseases of aging such as Alzheimer's disease. Noninvasive markers that assess these characteristics may be helpful in the study of co-occurrence of these diseases and potential additive and interacting effects. In this study, 4D flow MRI was used to measure intra-cranial flow features with cardiac-gated phase contrast MRI in cranial arteries and veins. Mean blood flow and pulsatility index as well as the transit time of the peak flow from the middle cerebral artery to the superior sagittal sinus were measured in a total of 104 subjects comprising of four groups: (a) subjects with Alzheimer's disease, (b) age-matched controls, (c) subjects with mild cognitive impairment, and (d) a group of late middle-aged with parental history of sporadic Alzheimer's disease. The Alzheimer's disease group exhibited: a significant decrease in mean blood flow in the superior sagittal sinus, transverse sinus, middle cerebral artery, and internal carotid arteries; a significant decrease of the peak and end diastolic blood flow in the middle cerebral artery and superior sagittal sinus; a faster transmission of peak flow from the middle cerebral artery to the superior sagittal sinus and increased pulsatility index along the carotid siphon.

4D flow MRI for intracranial hemodynamics assessment in Alzheimer's disease

Cerebral blood flow, arterial pulsation, and vasomotion play important roles in the transport of waste metabolites out of the brain. Impaired vasomotion results in reduced driving force for the perivascular/glymphatic clearance of beta-amyloid. Noninvasive cerebrovascular characteristic features that potentially assess these transport mechanisms are mean blood flow (MBF) and pulsatility index (PI). In this study, 4D flow MRI was used to measure intra-cranial flow features, particularly MBF, PI, resistive index (RI) and cross-sectional area in patients with Alzheimer's disease (AD), mild cognitive impairment and in age matched and younger cognitively healthy controls. Three-hundred fourteen subjects participated in this study. Volumetric, time-resolved phase contrast (PC) MRI data were used to quantify hemodynamic parameters from 11 vessel segments. Anatomical variants of the Circle of Willis were also cataloged. The AD population reported a statistically significant decrease in MBF and cross-sectional area, and also an increase in PI and RI compared to age matched cognitively healthy control subjects. The 4D flow MRI technique used in this study provides quantitative measurements of intracranial vessel geometry and the velocity of flow. Cerebrovascular characteristics features of vascular health such as pulsatility index can be extracted from the 4D flow MRI data.

Heart failure and dementia: survival in relation to types of heart failure and different dementia disorders

Aims

Heart failure (HF) and dementia frequently coexist, but little is known about their types, relationships to each other and prognosis. The aims were to (i) describe patients with HF and dementia, assess (ii) the proportion of specific dementia disorders in types of HF based on ejection fraction and (iii) the prognostic role of types of HF and dementia disorders.

Methods and results

The Swedish Heart Failure Registry (RiksSvikt) and The Swedish Dementia Registry (SveDem) were record-linked. Associations between dementia disorders and HF types were assessed with multinomial logistic regression and survival was investigated with Kaplan–Meier analysis and multivariable Cox regression. We studied 775 patients found in both registries (55% men, mean age 82 years). Ejection fraction was preserved in 38% of patients, reduced in 34%, and missing in 28%. The proportions of dementia disorders were similar across HF types. Vascular dementia was the most common dementia disorder (36%), followed by other dementias (28%), mixed dementia (20%), and Alzheimer disease (16%). Over a mean follow-up of 1.5 years, 76% of patients survived 1 year. We observed no significant differences in survival with regard to HF type (P = 0.2) or dementia disorder (P = 0.5). After adjustment for baseline covariates, neither HF types nor dementia disorders were independently associated with survival.

Conclusions

Heart failure with preserved ejection fraction was the most common HF type and vascular dementia was the most common dementia disorder. The proportions of dementia disorders were similar across HF types. Neither HF types nor specific dementia disorders were associated with survival.