Establishment of combined diagnostic models of Alzheimer's disease in a Chinese cohort: the Chongqing Ageing & Dementia Study (CADS)

A New Strategy for Ultrasensitive Detection Based on Target microRNA-Triggered Rolling Circle Amplification in the Early Diagnosis of Alzheimer's Disease

There is an urgent need to accurately quantify microRNA (miRNA)-based Alzheimer's disease (AD) biomarkers, which have emerged as promising diagnostic biomarkers. In this study, we present a rapid and universal approach to establishing a target miRNA-triggered rolling circle amplification (RCA) detection strategy, which achieves ultrasensitive detection of several targets, including miR-let7a-5p, miR-34a-5p, miR-206-3p, miR-9-5p, miR-132-3p, miR-146a-5p, and miR-21-5p. Herein, the padlock probe contains three repeated signal strand binding regions and a target miRNA-specific region. The target miRNA-specific region captures miRNA, and then the padlock probe is circularized with the addition of T4 DNA ligase. Subsequently, an RCA reaction is triggered, and RCA products containing multiple signal strand binding regions are generated to trap abundant fluorescein-labeled signal strands. The addition of exonuclease III (Exo III) causes signal strand digestion and leads to RCA product recycling and liberation of fluorescein. Ultimately, graphene oxide (GO) does not absorb the liberated fluorescein because of poor mutual interaction. This method exhibited high specificity, sensitivity, repeatability, and stability toward let-7a, with a detection limit of 19.35 fM and a linear range of 50 fM to 5 nM. Moreover, it showed excellent applicability for recovering miRNAs in normal human serum. Our strategy was applied to detect miRNAs in the plasma of APP/PS1 mice, demonstrating its potential in the diagnosis of miRNA-associated disease and biochemical research.

Pathophysiology characterization of Alzheimer's disease in South China's aging population: for the Greater-Bay-Area Healthy Aging Brain Study (GHABS)

INTRODUCTION

The Guangdong-Hong Kong-Macao Greater-Bay-Area of South China has an 86 million population and faces a significant challenge of Alzheimer's disease (AD). However, the characteristics and prevalence of AD in this area are still unclear due to the rarely available community-based neuroimaging AD cohort.

METHODS

Following the standard protocols of the Alzheimer's Disease Neuroimaging Initiative, the Greater-Bay-Area Healthy Aging Brain Study (GHABS) was initiated in 2021. GHABS participants completed clinical assessments, plasma biomarkers, genotyping, magnetic resonance imaging (MRI), β-amyloid (Aβ) positron emission tomography (PET) imaging, and tau PET imaging. The GHABS cohort focuses on pathophysiology characterization and early AD detection in the Guangdong-Hong Kong-Macao Greater Bay Area. In this study, we analyzed plasma Aβ42/Aβ40 (A), p-Tau181 (T), neurofilament light, and GFAP by Simoa in 470 Chinese older adults, and 301, 195, and 70 had MRI, Aβ PET, and tau PET, respectively. Plasma biomarkers, Aβ PET, tau PET, hippocampal volume, and temporal-metaROI cortical thickness were compared between normal control (NC), subjective cognitive decline (SCD), mild cognitive impairment (MCI), and dementia groups, controlling for age, sex, and APOE-ε4. The prevalence of plasma A/T profiles and Aβ PET positivity were also determined in different diagnostic groups.

RESULTS

The aims, study design, data collection, and potential applications of GHABS are summarized. SCD individuals had significantly higher plasma p-Tau181 and plasma GFAP than the NC individuals. MCI and dementia patients showed more abnormal changes in all the plasma and neuroimaging biomarkers than NC and SCD individuals. The frequencies of plasma A+/T+ (NC; 5.9%, SCD: 8.2%, MCI: 25.3%, dementia: 64.9%) and Aβ PET positivity (NC: 25.6%, SCD: 22.5%, MCI: 47.7%, dementia: 89.3%) were reported.

DISCUSSION

The GHABS cohort may provide helpful guidance toward designing standard AD community cohorts in South China. This study, for the first time, reported the pathophysiology characterization of plasma biomarkers, Aβ PET, tau PET, hippocampal atrophy, and AD-signature cortical thinning, as well as the prevalence of Aβ PET positivity in the Guangdong-Hong Kong-Macao Greater Bay Area of China. These findings provide novel insights into understanding the characteristics of abnormal AD pathological changes in South China's older population.

Case of Autosomal Dominant Alzheimer Disease With Negative Findings From PiB-PET Examination

Background and Objectives

This study reports an uncommon case of autosomal dominant Alzheimer disease (AD) with negative PiB-PET findings.

Methods

A 55-year-old woman was admitted to the hospital due to a progressive cognitive decline for over 9 years, along with a possible dementia family history. The patient underwent routine laboratory tests, neuropsychological assessments, and neuroimaging examinations. Additionally, the cerebrospinal fluid sample was analyzed for AD biomarkers using the Single Molecular Array (Simoa) technique. A targeted Next-Generation-Sequencing (NGS) panel screening was also conducted.

Results

Routine blood and CSF laboratory tests, as well as CSF tap test, yielded negative results. Cranial MRI showed atrophy of the whole brain. PiB-PET scanning indicated that PiB was merely retained in her brain with an overall standard uptake value ratio (SUVR) <1.0. Simoa analysis showed an increase in the level of CSF t-tau and a decrease in that of CSF Aβ42. NGS panel screening detected a c.G2032A (p.D678N) heterozygous mutation in APP. Consequently, the patient was diagnosed with autosomal dominant AD.

Discussion

We have reported an uncommon case of autosomal dominant AD carrying p.D678N variant in APP with negative PiB-PET results. The diagnosis of AD should not be directly excluded solely based on the negative PiB-PET results.

Association between plasma CTRPs with cognitive impairment and neurodegeneration of Alzheimer's disease

AIMS

Recent evidence indicated the biological basis of complement 1q (C1q)/tumor necrosis factor (TNF)-related protein (CTRP) 3, 4, and 14 for affecting brain structure and cognitive function. Thus, we aimed to investigate the association between plasma CTRPs with Alzheimer's disease (AD).

METHODS

A multicenter, cross-sectional study recruited patients with AD (n = 137) and cognitively normal (CN) controls (n = 140). After the data collection of demographic characteristics, lifestyle risk factors, and medical history, plasma levels of tau phosphorylated at threonine 217 (pT217), pT181, neurofilament light (NfL), CTRP3, 4, and 14 were examined and compared. Multivariate logistic regression analysis was applied to determine associations of plasma CTPRs with the presence of AD. The correlation analysis was used to explore correlations between plasma CTPRs with scores of Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Activities of Daily Living (ADL) scale, and Clinical Dementia Rating Sum of Boxes (CDR-SB), and levels of plasma pT217, pT181, and NfL. Receiver-operating characteristic (ROC) analysis and Delong's test were used to determine the diagnostic power of plasma CTPRs.

RESULTS

Plasma levels of CTRP3, 4, and 14 were higher in AD group than those in CN group. After adjusting for conventional risk factors, CTRP3, CTRP4, and CTRP14 were associated with the presence of AD. In AD patients, CTRP3 was negatively correlated with scores of MMSE and MoCA, while positively correlated with ADL score, CDR-SB score, pT217, and pT181; CTRP4 was positively correlated with CDR-SB score, pT181, and NfL; CTRP14 was negatively correlated with MMSE score, while positively correlated with CDR-SB score, pT217, and NfL. An independent addition of CTRP3 and 4 to the basic model combining age, sex, years of education, APOE4 status, BMI, TG, and HDL-C led to a significant improvement in diagnostic power for AD, respectively.

CONCLUSIONS

All the findings preliminarily uncovered associations between plasma CTRPs and AD and suggested the potential of CTRPs as a blood-derived biomarker for AD.

Alzheimer's disease, aging, and cannabidiol treatment: a promising path to promote brain health and delay aging

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by progressive memory loss, neurodegeneration, and cognitive decline. Aging is one of the risk factors for AD. Although the mechanisms underlying aging and the incidence rate of AD are unclear, aging and AD share some hallmarks, such as oxidative stress and chronic inflammation. Cannabidiol (CBD), the major non-psychoactive phytocannabinoid extracted from Cannabis sativa, has recently emerged as a potential candidate for delaying aging and a valuable therapeutic tool for the treatment of aging-related neurodegenerative diseases due to its antioxidant and anti-inflammation properties. This article reviews the relevant literature on AD, CBD treatment for AD, cellular senescence, aging, and CBD treatment for aging in recent years. By analyzing these published data, we attempt to explore the complex correlation between cellular senescence, aging, and Alzheimer's disease, clarify the positive feedback effect between the senescence of neurocytes and Alzheimer's disease, and summarize the role and possible molecular mechanisms of CBD in preventing aging and treating AD. These data may provide new ideas on how to effectively prevent and delay aging, and develop effective treatment strategies for age-related diseases such as Alzheimer's disease.

Associations Between Plasma Klotho with Renal Function and Cerebrospinal Fluid Amyloid-β Levels in Alzheimer's Disease: The Chongqing Ageing & Dementia Study

BACKGROUND

The kidney-brain crosstalk has been involved in Alzheimer's disease (AD) with the mechanism remaining unclear. The anti-aging factor Klotho was reported to attenuate both kidney injury and AD pathologies.

OBJECTIVE

To investigate whether plasma Klotho participated in kidney-brain crosstalk in AD.

METHODS

We enrolled 33 PiB-PET-positive AD patients and 33 amyloid-β (Aβ)-negative age- and sex-matched cognitively normal (CN) controls from the Chongqing Ageing & Dementia Study (CADS). The levels of plasma Klotho, Aβ, and tau in the cerebrospinal fluid (CSF) were measured by enzyme-linked immunosorbent assay.

RESULTS

We found higher plasma Klotho and lower estimated glomerular filtration rate (eGFR) levels in AD patients compared with CN. The eGFR were positively associated with Aβ 42, Aβ 40 levels in CSF and negatively associated with CSF T-tau levels. Plasma Klotho levels were both negatively correlated with CSF Aβ 42 and eGFR. Mediation analysis showed that plasma Klotho mediated 24.96% of the association between eGFR and CSF Aβ 42.

CONCLUSION

Renal function impacts brain Aβ metabolism via the kidney-brain crosstalk, in which the plasma klotho may be involved as a mediator. Targeting Klotho to regulate the kidney-brain crosstalk provides potential therapeutic approaches for AD.