Selective neuronal vulnerability in Alzheimer's disease

Association of rs2062323 in the TREM1 gene with Alzheimer's disease and cerebrospinal fluid-soluble TREM2

INTRODUCTION AND AIMS

Genetic variations play a significant role in determining an individual's AD susceptibility. Research on the connection between AD and TREM1 gene polymorphisms (SNPs) remained lacking. We sought to examine the associations between TREM1 SNPs and AD.

METHODS

Based on the 1000 Genomes Project data, linkage disequilibrium (LD) analyses were utilized to screen for candidate SNPs in the TREM1 gene. AD cases (1081) and healthy control subjects (870) were collected and genotyped, and the associations between candidate SNPs and AD risk were analyzed. We explored the associations between target SNP and AD biomarkers. Moreover, 842 individuals from ADNI were selected to verify these results. Linear mixed models were used to estimate associations between the target SNP and longitudinal cognitive changes.

RESULTS

The rs2062323 was identified to be associated with AD risk in the Han population, and rs2062323T carriers had a lower AD risk (co-dominant model: OR, 0.67, 95% CI, 0.51-0.88, p = 0.0037; additive model: OR, 0.82, 95% CI, 0.72-0.94, p = 0.0032). Cerebrospinal fluid (CSF) sTREM2 levels were significantly increased in middle-aged rs2062323T carriers (additive model: β = 0.18, p = 0.0348). We also found significantly elevated levels of CSF sTREM2 in the ADNI. The rate of cognitive decline slowed down in rs2062323T carriers.

CONCLUSIONS

This study is the first to identify significant associations between TREM1 rs2062323 and AD risk. The rs2062323T may be involved in AD by regulating the expression of TREM1, TREML1, TREM2, and sTREM2. The TREM family is expected to be a potential therapeutic target for AD.

Ergothioneine and its prospects as an anti-ageing compound

Healthy ageing is a crucial process that needs to be highlighted as it affects the quality of lifespan. An increase in oxidative stress along with ageing is the major factor related to the age-associated diseases, especially neurodegenerative disorders. An antioxidant-rich diet has been proven to play a significant role in the ageing process. Targeting ageing mechanisms could be a worthwhile approach to improving health standards. Ergothioneine (EGT), a hydrophilic compound with specific transporter known as OCTN1, has been shown to exert anti-ageing properties. In addition to its antioxidant effect, EGT has been reported to have anti-senescence, anti-inflammatory and anti-neurodegenerative properties. This review aims to define the pivotal role of EGT in major signalling pathways in ageing such as insulin/insulin-like growth factor (IGF) signalling (IIS), sirtuin 6 (SIRT6) and mammalian target of rapamycin complex (mTOR) pathways. The review further discusses evidence of EGT on neurodegeneration in its therapeutic context in various model organisms, providing new insights into improving health. In conclusion, an ergothioneine-rich diet may be beneficial in preventing age-related diseases, resulting in a healthy ageing population.

Regional heterogeneity in mitochondrial function underlies region specific vulnerability in human brain ageing: Implications for neurodegeneration

Selective neuronal vulnerability (SNV) of specific neuroanatomical regions such as frontal cortex (FC) and hippocampus (HC) is characteristic of age-associated neurodegenerative diseases (NDDs), although its pathogenetic basis remains unresolved. We hypothesized that physiological differences in mitochondrial function in neuroanatomical regions could contribute to SNV. To investigate this, we evaluated mitochondrial function in human brains (age range:1-90 y) in FC, striatum (ST), HC, cerebellum (CB) and medulla oblongata (MD), using enzyme assays and quantitative proteomics. Striking differences were noted in resistant regions- MD and CB compared to the vulnerable regions- FC, HC and ST. At younger age (25 ± 5 y), higher activity of electron transport chain enzymes and upregulation of metabolic and antioxidant proteins were noted in MD compared to FC and HC, that was sustained with increasing age (≥65 y). In contrast, the expression of synaptic proteins was higher in FC, HC and ST (vs. MD). In line with this, quantitative phospho-proteomics revealed activation of upstream regulators (ERS, PPARα) of mitochondrial metabolism and inhibition of synaptic pathways in MD. Microtubule Associated Protein Tau (MAPT) showed overexpression in FC, HC and ST both in young and older age (vs. MD). MAPT hyperphosphorylation and the activation of its kinases were noted in FC and HC with age. Our study demonstrates that regional heterogeneity in mitochondrial and other cellular functions contribute to SNV and protect regions such as MD, while rendering FC and HC vulnerable to NDDs. The findings also support the "last in, first out" hypothesis of ageing, wherein regions such as FC, that are the most recent to develop phylogenetically and ontogenetically, are the first to be affected in ageing and NDDs.

Tau Toxicity in Neurodegeneration

Tau is a microtubule-associated protein widely distributed in the central nervous system (CNS). The main function of tau is to promote the assembly of microtubules and stabilize their structure. After a long period of research on neurodegenerative diseases, the function and dysfunction of the microtubule-associated protein tau in neurodegenerative diseases and tau neurotoxicity have attracted increasing attention. Tauopathies are a series of progressive neurodegenerative diseases caused by pathological changes in tau, such as abnormal phosphorylation. The pathological features of tauopathies are the deposition of abnormally phosphorylated tau proteins and the aggregation of tau proteins in neurons. This article first describes the normal physiological function and dysfunction of tau proteins and then discusses the enzymes and proteins involved in tau phosphorylation and dephosphorylation, the role of tau in cell dysfunction, and the relationships between tau and several neurodegenerative diseases. The study of tau neurotoxicity provides new directions for the treatment of tauopathies.

Associations of the cerebrospinal fluid hepatocyte growth factor with Alzheimer's disease pathology and cognitive function

Background

Hepatocyte growth factor (HGF) plays a role in neuronal survival and development, and has been implicated in neurodegenerative diseases. We sought to examine the associations of the CSF HGF with Alzheimer’s disease (AD) pathology and cognitive function.

Methods

A total of 238 participants (including 90 cognitively normal (CN) and 148 mild cognitive impairment (MCI)) who had measurements of CSF HGF were included from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database. Multiple linear regression models were utilized to explore the cross-sectional associations of CSF HGF with AD biomarkers (including Aβ42, pTau, and tTau proteins) in non-demented participants. Moreover, linear mixed-effects regression models were utilized to explore the longitudinal associations of HGF subgroups with cognitive function. Mediation analyses were utilized to explore the mediation effects of AD markers.

Results

MCI individuals had significantly increased CSF HGF compared with the CN individuals. Results of multiple linear regressions showed significant correlations of CSF HGF with CSF Aβ42, pTau, and tTau in non-demented participants. Higher level of baseline CSF HGF was associated with faster cognitive decline. Influences of the baseline CSF HGF on cognition were partially mediated by Aβ42, pTau, and tTau pathologies.

Conclusions

High concentrations of HGF in CSF may be related to faster cognitive decline. The cognitive consequences of higher CSF HGF partly stem from AD pathology, which suggests that the CSF HGF may be an attractive biomarker candidate to track AD progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02356-9.

Disease-specific interactome alterations via epichaperomics: the case for Alzheimer's disease

The increasingly appreciated prevalence of complicated stressor-to-phenotype associations in human disease requires a greater understanding of how specific stressors affect systems or interactome properties. Many currently untreatable diseases arise due to variations in, and through a combination of, multiple stressors of genetic, epigenetic, and environmental nature. Unfortunately, how such stressors lead to a specific disease phenotype or inflict a vulnerability to some cells and tissues but not others remains largely unknown and unsatisfactorily addressed. Analysis of cell- and tissue-specific interactome networks may shed light on organization of biological systems and subsequently to disease vulnerabilities. However, deriving human interactomes across different cell and disease contexts remains a challenge. To this end, this opinion article links stressor-induced protein interactome network perturbations to the formation of pathologic scaffolds termed epichaperomes, revealing a viable and reproducible experimental solution to obtaining rigorous context-dependent interactomes. This article presents our views on how a specialized 'omics platform called epichaperomics may complement and enhance the currently available conventional approaches and aid the scientific community in defining, understanding, and ultimately controlling interactome networks of complex diseases such as Alzheimer's disease. Ultimately, this approach may aid the transition from a limited single-alteration perspective in disease to a comprehensive network-based mindset, which we posit will result in precision medicine paradigms for disease diagnosis and treatment.