High serum Abeta and vascular risk factors in first-degree relatives of Alzheimer's disease patients

What Information do Systemic Pathological Changes Bring to the Diagnosis and Treatment of Alzheimer's Disease?

Alzheimer's disease (AD) is regarded as a neurodegenerative disease, and it has been proposed that AD may be a systemic disease. Studies have reported associations between non-neurological diseases and AD. The correlations between AD pathology and systemic (non-neurological) pathological changes are intricate, and the mechanisms underlying these correlations and their causality are unclear. In this article, we review the association between AD and disorders of other systems. In addition, we summarize the possible mechanisms associated with AD and disorders of other systems, mainly from the perspective of AD pathology. Regarding the relationship between AD and systemic pathological changes, we aim to provide a new outlook on the early warning signs and treatment of AD, such as establishing a diagnostic and screening system based on more accessible peripheral samples.

Hypertension moderates the relationship between plasma beta-amyloid and cognitive impairment: a cross-sectional study in Xi'an, China

Background

Plasma beta-amyloid (Aβ) are important biomarkers for Alzheimer's disease and cognitive impairment (CI), but results are controversial. It remains unclear whether hypertension modulates their relationship. This cross-sectional study investigates whether hypertension moderates the relationship between plasma Aβ and cognitive impairment (CI).

Methods

This cross-sectional study included 1488 subjects ≥ 40 years from rural areas of northwestern China. CI was defined as a Mini-Mental State Examination score lower than the cutoff. Firstly, plasma Aβ40, Aβ42, Aβ42/Aβ40 were analyzed as restricted cubic spline. Then, categories of combined plasma Aβ were created by making bisection of plasma Aβ according to average and combining them as L-Aβ40 and L-Aβ42, H-Aβ40 and L-Aβ42, L-Aβ40 and H-Aβ42, H-Aβ40 and H-Aβ42. Decreased plasma Aβ40 was defined as < 25th percentile. Multivariate logistic regression examined the relationship between plasma Aβ and CI in total population, the hypertension subgroup and the non-hypertension subgroup.

Results

737 participants (49.5%) had hypertension and 189 participants (12.7%) had CI. Simultaneously elevated plasma Aβ40 and Aβ42 was associated with CI in hypertension (H-Aβ40 and H-Aβ42 vs. L-Aβ40 and L-Aβ42, 21.1% vs.10.7%, P = 0.033; OR = 1.984 [95% CI, 1.067-3.691], P = 0.030) but not in the non-hypertension. Decreased plasma Aβ40 was associated with CI in the non-hypertension (14.9% vs. 9.2%, P = 0.026; OR = 1.728 [95% CI, 1.018-2.931], P = 0.043) but not in the hypertension.

Conclusion

Hypertension is an important modulator in the relationship between plasma Aβ and CI. Simultaneously elevated plasma Aβ40 and Aβ42 in the hypertension, and decreased plasma Aβ40 in the non-hypertension, may be risk factors for CI. These findings emphasize the need to consider hypertension in CI detection.

Serum amyloid beta 42 levels correlated with metabolic syndrome and its components

Introduction

Beta-amyloid accumulation in the brain appears to be a key initiating event in Alzheimer's disease (AD), and factors associated with increased deposition of beta-amyloid are of great interest. Enhanced deposition of amyloid-β peptides is due to an imbalance between their production and elimination. Previous studies show that diminished levels of CSF amyloid beta 42 (Aβ42) is a biomarker in AD; however, the role of serum Aβ42 in AD is contradictory. BMI and obesity have been reported to be related to increased serum Aβ42 levels. Therefore, we aimed to investigate the relation between metabolic syndrome (MetS), its clinical measures (abdominal obesity, high glucose, high triglyceride, low high-density lipoprotein cholesterol level, and hypertension), and serum Aβ42 levels.

Methods

A total of 1261 subjects, aged 18-89 years in Chengdu, China, were enrolled from January 2020 to January 2021 to explore the correlation of serum Aβ42 levels with body mass index (BMI), blood lipids, and blood pressure. Furthermore, as the risk of MetS is closely related to age, 1,212 participants (N = 49 with age ≥ 80 years old were excluded) were analyzed for the correlation of serum Aβ42 level and MetS clinical measures.

Results

The results showed that log-transformed serum Aβ42 level was positively correlated with BMI (R = 0.29; p < 0.001), log-transformed triglyceride (R = 0.14; p < 0.001), and diastolic blood pressure (DBP) (R = 0.12; p < 0.001) and negatively correlated with high-density lipoprotein (HDL-c) (R = -0.18; p < 0.001). After adjusting for age, sex, and other covariates, elevated serum Aβ42 level was correlated with higher values of BMI (βmodel1 = 2.694, βmodel2 = 2.703) and DBP (βmodel1 = 0.541, βmodel2 = 0.546) but a lower level of HDL-c (βmodel2 = -1.741). Furthermore, serum Aβ42 level was positively correlated with MetS and its clinical measures, including BMI and DBP, and negatively correlated with HDL-c level in the Han Chinese population. However, the level of serum Aβ42 did not show a significant correlation with high glucose or high triglyceride.

Discussion

These observations indicate that MetS and its components are associated with higher levels of serum Aβ42 and hence limit the potential of serum Aβ42 as a suitable diagnostic biomarker for AD. As such, we recommend serum Aβ42 serve as a direct risk biomarker for MetS rather than for AD.

Blood Triglyceride and High-Density Lipoprotein Levels Are Associated with Plasma Amyloid-β Transport: A Population-Based Cross-Sectional Study

BACKGROUND

Studies have found that blood lipids are associated with plasma amyloid-β (Aβ) levels, but the underlying mechanism is still unclear. Two Aβ transporters, soluble form of low-density lipoprotein receptor related protein-1 (sLRP1) and soluble receptor of advanced glycation end products (sRAGE), are crucial in peripheral Aβ transport.

OBJECTIVE

The aim was to investigate the effects of lipids on the relationships between plasma Aβ and transporter levels.

METHODS

This study included 1,436 adults aged 40 to 88 years old. Blood Aβ, sLRP1, sRAGE, and lipid levels were measured. Univariate and multivariate analyses were used to analyze the relationships between lipids and plasma Aβ, sLRP1, and sRAGE.

RESULTS

After adjusting for all possible covariates, high-density lipoprotein (HDL-c) was positively associated with plasma Aβ42 and sRAGE (β= 6.158, p = 0.049; β= 121.156, p < 0.001, respectively), while triglyceride (TG) was negatively associated with plasma Aβ40, Aβ42, and sRAGE (β= -48.389, p = 0.017; β= -11.142, p = 0.020; β= -147.937, p = 0.003, respectively). Additionally, positive correlations were found between plasma Aβ and sRAGE in the normal TG (Aβ40: β= 0.034, p = 0.005; Aβ42: β= 0.010, p = 0.001) and HDL-c groups (Aβ40: β= 0.023, p = 0.033; Aβ42: β= 0.008, p = 0.002) but not in the high TG and low HDL-c groups.

CONCLUSION

Abnormal levels of TG and HDL-c are associated with decreased Aβ and sRAGE levels. Positive correlations between plasma Aβ and sRAGE were only found in the normal TG and HDL-c groups but not in the high TG and low HDL-c groups. These results indicated that dyslipidemia contributing to plasma Aβ levels might also be involved in peripheral Aβ clearance.

Blood Pressure Level Is Associated With Changes in Plasma Aβ1 -40 and Aβ1-42 Levels: A Cross-sectional Study Conducted in the Suburbs of Xi'an, China

Objectives: Amyloid-β (Aβ) deposition in the brain is the hallmark of Alzheimer’s disease (AD) pathology. Hypertension is a risk factor for AD, but the effects of hypertension on Aβ deposition are not fully determined. Considering peripheral Aβ closely relates to Aβ deposition in the brain, we investigated the relationships between blood pressure (BP) level and plasma Aβ concentrations.

Methods: One-thousand and sixty-nine participants (age above 45) from a village in the suburbs of Xi’an, China were enrolled. Questionnaires and validated Chinese versions of the Mini-Mental State Examination (MMSE) were used to collect information about vascular risk factors and assess cognition function. The apolipoprotein E (ApoE) genotype was detected using PCR and sequencing. Plasma Aβ levels were measured using ELISA. The associations between BP and plasma Aβ levels were analyzed by using multivariate linear regression.

Results: Plasma Aβ_1–40 level was higher in high BP group than that in normal BP group (53.34 ± 8.50 pg/ml vs. 51.98 ± 8.96 pg/ml, P = 0.013), in high SBP group than that in normal SBP group (53.68 ± 8.69 pg/ml vs. 51.88 ± 8.80 pg/ml, P = 0.001) and in high MABP group than that in normal MABP group (54.05 ± 8.78 pg/ml vs. 52.04 ± 8.75 pg/ml, P = 0.001). After controlling for the confounding factors, SBP (b = 0.078, P < 0.001), DBP (b = 0.090, P = 0.008) and MABP (b = 0.104, P < 0.001) correlated with plasma Aβ_1–40 level positively in ApoE ε4 non-carriers, but not ApoE ε4 carriers.

Conclusions: Elevated BP levels were associated with increased plasma Aβ_1–40 levels in middle-aged and elderly ApoE ε4 non-carriers.

The relationship between blood lipids and plasma amyloid beta is depend on blood pressure: a population-based cross-sectional study

Background

It is believed that deposition of amyloid beta (Aβ) in the brain is the central pathological changes of Alzheimer’s disease (AD), which triggers a series of pathological processes. However, the relationship between dyslipidemia and AD is uncertain. Considering the peripheral Aβ levels are related to brain Aβ deposition, we explore the relationships between blood lipids and plasma Aβ.

Methods

Participants who lived in the selected village of Xi’an for more than 3 years were enrolled, aged 40–85 years (n = 1282, 37.9% male). Fasting blood lipid, plasma Aβ levels, basic information and living habits were measured. Multiple linear regressions were used.

Results

In total population, blood lipids were not associated with plasma Aβ. After stratified by blood pressure, serum total cholesterol (TC) and low-density lipoprotein (LDL-c) were positively associated with plasma Aβ₄₂ levels (β_TC = 0.666, P_TC = 0.024; β_LDL-c = 0.743, P_LDL-c = 0.011, respectively) in normal blood pressure. LDL-c was negatively associated with plasma Aβ₄₀ levels (β = − 0.986, P = 0.037) in high blood pressure.

Conclusion

Elevated plasma Aβ₄₂ levels are associated with higher TC and LDL-c in normal blood pressure. Elevated plasma Aβ₄₀ levels are associated with lower LDL-c in high blood pressure. This indicated that the relationships between blood lipids and plasma Aβ were confounded by blood pressure.

European multicentre double-blind placebo-controlled trial of Nilvadipine in mild-to-moderate Alzheimer's disease-the substudy protocols: NILVAD frailty; NILVAD blood and genetic biomarkers; NILVAD cerebrospinal fluid biomarkers; NILVAD cerebral blood flow

INTRODUCTION

In conjunction with the NILVAD trial, a European Multicentre Double-Blind Placebo Controlled trial of Nilvadipine in Mild-to-Moderate Alzheimer's disease (AD), there are four NILVAD substudies in which eligible NILVAD patients are also invited to participate. The main NILVAD protocol was previously published in BMJ Open (2014). The objectives of the NILVAD substudies are to determine whether frailty, cerebrospinal fluid (CSF), blood biomarker profile and Apolipoprotein E (APOE) status predict response to Nilvadipine, and to investigate the effect of Nilvadipine on cerebral blood flow and blood biomarkers.

METHODS AND ANALYSIS

All participants who fulfil criteria for the main NILVAD study are eligible for participation in the NILVAD substudies. Participation is subject to informed consent and whether the substudy is available at a particular NILVAD study site. Each substudy entails extra measurements during the course of the main NILVAD study. For example, in the blood and genetic biomarkers substudy, extra blood (30 mL) will be collected at week 0, week 13, week 52 and week 78, while in the cerebral blood flow substudy, participants will receive an MRI and transcranial Doppler measurements at week 0, week 26 and week 78. In the CSF substudy, 10 mL CSF is collected at week 0 and week 78.

ETHICS AND DISSEMINATION

All NILVAD substudies and all subsequent amendments have received ethical approval within each participating country, according to national regulations. Each participant provides written consent to participate. All participants remain anonymised throughout and the results of each substudy will be published in an international peer reviewed journal.

TRIAL REGISTRATION NUMBER

EUDRACT 2012-002764-27; Pre-results.

Obesity and Hepatic Steatosis Are Associated with Elevated Serum Amyloid Beta in Metabolically Stressed APPswe/PS1dE9 Mice

Diabesity-associated metabolic stresses modulate the development of Alzheimer's disease (AD). For further insights into the underlying mechanisms, we examine whether the genetic background of APPswe/PS1dE9 at the prodromal stage of AD affects peripheral metabolism in the context of diabesity. We characterized APPswe/PS1dE9 transgenic mice treated with a combination of high-fat diet with streptozotocin (HFSTZ) in the early stage of AD. HFSTZ-treated APPswe/PS1dE9 transgenic mice exhibited worse metabolic stresses related to diabesity, while serum β-amyloid levels were elevated and hepatic steatosis became apparent. Importantly, two-way analysis of variance shows a significant interaction between HFSTZ and genetic background of AD, indicating that APPswe/PS1dE9 transgenic mice are more vulnerable to HFSTZ treatment. In addition, body weight gain, high hepatic triglyceride, and hyperglycemia were positively associated with serum β-amyloid, as validated by Pearson's correlation analysis. Our data suggests that the interplay between genetic background of AD and HFSTZ-induced metabolic stresses contributes to the development of obesity and hepatic steatosis. Alleviating metabolic stresses including dysglycemia, obesity, and hepatic steatosis could be critical to prevent peripheral β-amyloid accumulation at the early stage of AD.

Effect of stent-assisted angioplasty on cognitive status and serum levels of amyloid beta in patients with intracranial and/or extracranial artery stenosis

AIM

The study reported here aimed to examine how stent-assisted angioplasty affects cognitive status and serum levels of amyloid betas (Aβs) 1-40 and 1-42 in patients with cerebral arterial stenosis.

METHODS

Patients with cerebral arterial stenosis were given stent-assisted angioplasty plus conventional treatment (stent-assisted angioplasty group) or conventional treatment alone (control group). Cognitive status and Aβ1-40 and Aβ1-42 serum levels were determined before treatment and at 4 and 8 weeks after treatment.

RESULTS

At 4 weeks after treatment, cognitive status in patients with stent-assisted angioplasty had clearly improved. Aβ1-42 serum levels changed insignificantly in all patients. However, Aβ1-40 serum levels and Aβ1-40/Aβ1-42 ratio decreased further in patients with stent-assisted angioplasty than in patients who received conventional treatment (controls). Eight weeks after treatment, cognitive status in patients who had undergone stent-assisted angioplasty were continuing to improve, Aβ1-42 serum levels had begun to increase dramatically, and Aβ1-40 serum levels and Aβ1-40/Aβ1-42 ratio had declined further.

CONCLUSION

Stent-assisted angioplasty could improve cognitive status and decrease Aβ1-40 serum levels and Aβ1-40/Aβ1-42 ratio.

Association between white matter microstructure, executive functions, and processing speed in older adults: the impact of vascular health

Cerebral white matter damage is not only a commonly reported consequence of healthy aging, but is also associated with cognitive decline and dementia. The aetiology of this damage is unclear; however, individuals with hypertension have a greater burden of white matter signal abnormalities (WMSA) on MR imaging than those without hypertension. It is therefore possible that elevated blood pressure (BP) impacts white matter tissue structure which in turn has a negative impact on cognition. However, little information exists about whether vascular health indexed by BP mediates the relationship between cognition and white matter tissue structure. We used diffusion tensor imaging to examine the impact of vascular health on regional associations between white matter integrity and cognition in healthy older adults spanning the normotensive to moderate-severe hypertensive BP range (43-87 years; N = 128). We examined how white matter structure was associated with performance on tests of two cognitive domains, executive functioning (EF) and processing speed (PS), and how patterns of regional associations were modified by BP and WMSA. Multiple linear regression and structural equation models demonstrated associations between tissue structure, EF and PS in frontal, temporal, parietal, and occipital white matter regions. Radial diffusivity was more prominently associated with performance than axial diffusivity. BP only minimally influenced the relationship between white matter integrity, EF and PS. However, WMSA volume had a major impact on neurocognitive associations. This suggests that, although BP and WMSA are causally related, these differential metrics of vascular health may act via independent pathways to influence brain structure, EF and PS.

Feasibility of Predicting MCI/AD Using Neuropsychological Tests and Serum β-Amyloid

We examined the usefulness of brief neuropsychological tests and serum Aβ as a predictive test for detecting MCI/AD in older adults. Serum Aβ levels were measured from 208 subjects who were cognitively normal at enrollment and blood draw. Twenty-eight of the subjects subsequently developed MCI (n = 18) or AD (n = 10) over the follow-up period. Baseline measures of global cognition, memory, language fluency, and serum Aβ(1-42) and the ratio of serum Aβ(1-42)/Aβ(1-40) were significant predictors for future MCI/AD using Cox regression with demographic variables, APOE ε4, vascular risk factors, and specific medication as covariates. An optimal sensitivity of 85.2% and specificity of 86.5% for predicting MCI/AD was achieved using ROC analyses. Brief neuropsychological tests and measurements of Aβ(1-42) obtained via blood warrants further study as a practical and cost effective method for wide-scale screening for identifying older adults who may be at-risk for pathological cognitive decline.

Association of plasma Aß peptides with blood pressure in the elderly

Background

Aß peptides are often considered as catabolic by-products of the amyloid ß protein precursor (APP), with unknown physiological functions. However, several biological properties have been tentatively attributed to these peptides, including a role in vasomotion.

We assess whether plasma Aß peptide levels might be associated with systolic and diastolic blood pressure values (SBP and DBP, respectively).

Methodology/Principal Findings

Plasma Aß_1-40 and Aß_1-42 levels were measured using an xMAP-based assay in 1,972 individuals (none of whom were taking antihypertensive drugs) from 3 independent studies: the French population-based 3C and MONA-LISA (Lille) studies (n = 627 and n = 769, respectively) and the Australian, longitudinal AIBL study (n = 576). In the combined sample, the Aß_1-42/ Aß_1-40 ratio was significantly and inversely associated with SBP (p = 0.03) and a similar trend was observed for DBP (p = 0.06). Using the median age (69) as a cut-off, the Aß_1-42/Aß_1-40 ratio was strongly associated with both SBP and DBP in elderly individuals (p = 0.002 and p = 0.03, respectively). Consistently, a high Aß_1-42/ Aß_1-40 ratio was associated with a lower risk of hypertension in both the combined whole sample (odds ratio [OR], 0.71; 95% confidence interval [CI], 0.56-0.90) and (to an even greater extent) in the elderly subjects (OR, 0.53; 95% CI, 0.37–0.75). Lastly, all these associations appeared to be primarily driven by the level of plasma Aß_1-40.

Conclusion

The plasma Aß_1-42/Aß_1-40 ratio is inversely associated with SBP, DBP and the risk of hypertension in elderly subjects, suggesting that Aß peptides affect blood pressure in vivo. These results may be particularly relevant in Alzheimer's disease, in which a high Aß_1-42/Aß_1-40 plasma ratio is reportedly associated with a decreased risk of incident disease.

Ganglioside metabolism in a transgenic mouse model of Alzheimer's disease: expression of Chol-1α antigens in the brain

The accumulation of Aβ (amyloid β-protein) is one of the major pathological hallmarks in AD (Alzheimer's disease). Gangliosides, sialic acid-containing glycosphingolipids enriched in the nervous system and frequently used as biomarkers associated with the biochemical pathology of neurological disorders, have been suggested to be involved in the initial aggregation of Aβ. In the present study, we have examined ganglioside metabolism in the brain of a double-Tg (transgenic) mouse model of AD that co-expresses mouse/human chimaeric APP (amyloid precursor protein) with the Swedish mutation and human presenilin-1 with a deletion of exon 9. Although accumulation of Aβ was confirmed in the double-Tg mouse brains and sera, no statistically significant change was detected in the concentration and composition of major ganglio-N-tetraosyl-series gangliosides in the double-Tg brain. Most interestingly, Chol-1α antigens (cholinergic neuron-specific gangliosides), such as GT1aα and GQ1bα, which are minor species in the brain, were found to be increased in the double-Tg mouse brain. We interpret that the occurrence of these gangliosides may represent evidence for generation of cholinergic neurons in the AD brain, as a result of compensatory neurogenesis activated by the presence of Aβ.

Anti-Tumoral Activity of a Short Decapeptide Fragment of the Alzheimer's Abeta Peptide

The inhibition of angiogenesis is regarded as a promising avenue for cancer treatment. Although some antiangiogenic compounds are in the process of development and testing, these often prove ineffective in vivo, therefore the search for new inhibitors is critical. We have recently identified a ten amino acid fragment of the Alzheimer Abeta peptide that is anti-angiogenic both in vitro and in vivo. In the present study, we investigated the antitumoral potential of this decapeptide using human MCF-7 breast carcinoma xenografts nude mice. We observed that this decapeptide was able to suppress MCF-7 tumor growth more potently than the antiestrogen tamoxifen. Inhibition of tumor vascularization as determined by PECAM-1 immunostaining and decreased tumor cell proliferation as determined by Ki67 immunostaining were observed following treatment with the Abeta fragment. In vitro, this peptide had no direct impact on MCF-7 tumor cell proliferation and survival suggesting that the inhibition of tumor growth and tumor cell proliferation observed in vivo is related to the antiangiogenic activity of the peptide. Taken together these data suggest that this short Abeta derivative peptide may constitute a new antitumoral agent.

Serum Abeta levels as predictors of conversion to mild cognitive impairment/Alzheimer disease in an ADAPT subcohort

Recent evidence suggests an association of beta-amyloid (Abeta) with vascular risk factors and the medications to treat them, which could potentially obfuscate the usefulness of Abeta for prediction of mild cognitive impairment (MCI) or Alzheimer disease (AD). In a subcohort from the Alzheimer's Disease Anti-inflammatory Prevention Trial (enriched for family history of AD), we investigated whether systolic blood pressure, total cholesterol, triglycerides, serum creatinine, apolipoprotein E, and use of statins and antihypertensives influenced the predictive value of serum Abeta for MCI/AD during a 2-year period. We collected blood samples to quantify serum Abeta from cognitively normal participants (n = 203) at baseline and ascertained the outcome of MCI/AD (n = 24) for a period of approximately 2 years. In an unadjusted model, the lowest quartile of Abeta(1-42) (hazard ratio [HR] = 2.93, 95% CI [1.02-8.32], P = 0.04) and of the Abeta(1-42)/Abeta(1-40) ratio (HR = 3.53, 95% CI [1.24-10.07], P = 0.02), compared with the highest quartile, predicted conversion to MCI/AD, but no impact of Abeta(1-40) was observed. No relationship between nonsteroidal antiinflammatory drug interventions and Abeta on MCI/AD risk was evident. Once data were adjusted for potential confounders (age, sex, and education), vascular risk factors, and the medications listed above, the lowest quartiles of Abeta(1-42) (HR = 4.47, 95% CI [1.39-14.39], P = 0.01), and of the Abeta(1-42/)Abeta(1-40) ratio (HR 4.87, 95% CI [1.50-15.87], P = 0.01) became strong predictors of conversion to MCI/AD. In this subcohort of individuals at risk for AD, the association of Abeta with vascular risk factors and medications to treat these conditions did not interfere with Abeta's predictive value for MCI/AD.