Advances in Amyloid-β Clearance in the Brain and Periphery: Implications for Neurodegenerative Diseases

Interplay Between Vascular Dysfunction and Neurodegenerative Pathology: New Insights into Molecular Mechanisms and Management

Vascular dysfunction frequently coexists with neurodegenerative disorders such as dementia and Alzheimer's disease (AD) in older individuals; however, the cause-and-effect relationship remains unclear. While AD is primarily characterized by neural tissue degeneration, emerging evidence suggests that aging-induced vascular dysfunction contributes to both the onset and progression of cognitive impairment and dementia by decreasing cerebral blood flow (CBF) and disrupting the blood-brain barrier (BBB). This challenges the traditional notion and underscores vascular dysfunction as an early pathogenic stimulus; thus, targeting vascular pathologies could be a promising strategy to slow dementia progression and potentially prevent AD. Conversely, aging-related neurodegeneration exacerbates vascular dysfunction, accelerating dementia pathology through oxidative stress and inflammation as well as deposition of neurotoxic substances such as beta-amyloid (Aβ) and tau in vascular walls. This bidirectional interaction creates a vicious cycle that worsens cognitive decline, underscoring the complexity of these diseases. This review aims to highlight recent advances in research on the mechanisms of aging-related vascular dysfunction in neurodegenerative diseases, focusing on vascular contributions to cognitive impairment and dementia (VCID) and AD. Additionally, we will explore the reciprocal effects and intricate relationship between vascular dysfunction and neurodegenerative pathologies, enhancing our understanding of relative disease pathogenesis and guiding the development of innovative prevention and treatment strategies.

The Promising Role of Selenium and Yeast in the Fight Against Protein Amyloidosis

In recent years, increasing attention has been paid to research on diseases related to the deposition of misfolded proteins (amyloids) in various organs. Moreover, modern scientists emphasise the importance of selenium as a bioelement necessary for the proper functioning of living organisms. The inorganic form of selenium-sodium selenite (redox-active)-can prevent the formation of an insoluble polymer in proteins. It is very important to undertake tasks aimed at understanding the mechanisms of action of this element in inhibiting the formation of various types of amyloid. Furthermore, yeast cells play an important role in this matter as a eukaryotic model organism, which is intensively used in molecular research on protein amyloidosis. Due to the lack of appropriate treatment in the general population, the problem of amyloidosis remains unsolved. This extracellular accumulation of amyloid is one of the main factors responsible for the occurrence of Alzheimer's disease. The review presented here contains scientific information discussing a brief description of the possibility of amyloid formation in cells and the use of selenium as a factor preventing the formation of these protein aggregates. Recent studies have shown that the yeast model can be successfully used as a eukaryotic organism in biotechnological research aimed at understanding the essence of the entire amyloidosis process. Understanding the mechanisms that regulate the reaction of yeast to selenium and the phenomenon of amyloidosis is important in the aetiology and pathogenesis of various disease states. Therefore, it is imperative to conduct further research and analysis aimed at explaining and confirming the role of selenium in the processes of protein misfolding disorders. The rest of the article discusses the characteristics of food protein amyloidosis and their use in the food industry. During such tests, their toxicity is checked because not all food proteins can produce amyloid that is toxic to cells. It should also be noted that a moderate diet is beneficial for the corresponding disease relief caused by amyloidosis.

Could Blood Transfusion Increase the Risk of Alzheimer's Disease? A Narrative Review

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease, and its pathogenesis is complex. In addition to amyloid-β and phosphorylated tau, inflammation and microbial infections also play a role in the development of AD. Currently, there is no effective clinical intervention to cure AD or completely halt its progression. Blood transfusion, a critical life-saving medical procedure widely employed in modern healthcare, faces growing demand due to global population aging. However, whether blood transfusion could increase the risk of AD is still not clear. Aβ and tau play major roles in the pathogenesis of AD and may possess the potential for transmission through blood transfusion. Iron overload and chronic inflammation, which can independently influence AD pathogenesis, may result from repeated transfusions. Additionally, herpesvirus, known to accelerate AD progression, can also be potentially transmitted by blood transfusion. In this study, recent advances in the associations between blood transfusion and the occurrence and development of AD were reviewed, and whether blood transfusion could increase the risk of AD was discussed. Furthermore, the related proposals for blood management and future research were advanced to provide references for the prevention and control of AD.

The role of insulin resistance and APOE genotype on blood-brain barrier integrity in Alzheimer's disease

INTRODUCTION

Growing evidence suggests a connection between insulin resistance and apolipoprotein E (APOE) genotype in Alzheimer's disease (AD) pathogenesis, but the mechanisms are unclear. We examined effects of insulin resistance and APOE genotype on blood-brain barrier (BBB) integrity in AD.

METHODS

BBB integrity was measured in 196 biologically-confirmed non-diabetic patients with AD evaluating CSF/serum albumin ratio, kappa and lambda free light chains (FLCs). Insulin resistance was assessed using triglyceride-glucose index (TyG). The impact of TyG on BBB integrity, and its interaction with APOE genotypes, was analyzed using multivariate models.

RESULTS

Sixty-four percent of patients with AD showed altered TyG, with the 21.8% classified as high TyG. TyG subgroups were associated with BBB abnormalities, with similar AD clinical and biomarkers profile. A significant interaction between TyG and APOE ε4/ε4 genotype on BBB permeability was found in multivariate analyses.

DISCUSSION

Insulin resistance is a common feature in non-diabetic AD and correlates with altered BBB permeability, interacting synergistically with APOE genotype.

HIGHLIGHTS

Insulin resistance and apolipoprotein E (APOE) genotype are well-recognized risk factors for Alzheimer's disease (AD). Insulin resistance shows high prevalence in patients with AD. Insulin resistance is related to damage in blood-brain barrier (BBB) integrity. The association between the triglyceride-glucose (TyG) index and BBB permeability varies in relation to APOE genotype; patients with the APOE ε4/ε4 displayed higher BBB permeability.

Pharmacological inhibition of receptor protein tyrosine phosphatase β/ζ decreases Aβ plaques and neuroinflammation in the hippocampus of APP/PS1 mice

Alzheimer's disease (AD) is a major neurodegenerative disorder that courses with chronic neuroinflammation. Pleiotrophin (PTN) is an endogenous inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ which is upregulated in different neuroinflammatory disorders of diverse origin, including AD. To investigate the role of RPTPβ/ζ in neuroinflammation and neurodegeneration, we used eight-to ten-month-old APP/PS1 AD mouse model. They were administered intragastrically with MY10, an inhibitor of RPTPβ/ζ, at different doses (60 and 90 mg/kg) every day for 14 days. Treatment with 90 mg/kg MY10 significantly reduced the number and size of amyloid beta (Aβ) plaques in the dorsal subiculum of the hippocampus of APP/PS1 mice. In addition, we observed a significant decrease in the number and size of astrocytes in both sexes and in the number of microglial cells in a sex-dependent manner. This suggests that RPTPβ/ζ plays an important role in modulating Aβ plaque formation and influences glial responses, which may contribute to improved Aβ clearance. In addition, MY10 treatment decreased the interaction of glial cells with Aβ plaques in the hippocampus of APP/PS1 mice. Furthermore, the analysis of proinflammatory markers in the hippocampus revealed that MY10 treatment decreased the mRNA levels of Tnfa and Hmgb1. Notably, treatment with MY10 increased Bace1 mRNA expression, which could be involved in enhancing Aβ degradation, and it decreased Mmp9 levels, which might reflect changes in the neuroinflammatory environment and impact Aβ plaque dynamics. These results support the therapeutic potential of inhibition of RPTPβ/ζ in modulating Aβ pathology and neuroinflammation in AD.

Effects silymarin and rosuvastatin on amyloid-carriers level in dyslipidemic Alzheimer's patients: A double-blind placebo-controlled randomized clinical trial

Purpose

The production/excretion rate of Amyloid-β (Aβ) is the basis of the plaque burden in alzheimer's disease (AD), which depends on both central and peripheral clearance. In this study, the effect of silymarin and rosuvastatin on serum markers and clinical outcomes in dyslipidemic AD patients was investigated.

Methods

Participants (n=36) were randomized to silymarin (140 mg), placebo, and rosuvastatin 10 mg orally three times a day for 6 months. Serum collection and clinical outcome tests were performed at baseline and after completion of treatment. Lipid profile markers, oxidative stress markers, Aβ1-42/Aβ1-40 ratio, and Soluble Low-density lipoprotein receptor-Related Protein-1 (sLRP1)/Soluble Receptor for Advanced Glycation End Products (sRAGE) ratio were measured.

Results

There was a statistically significant increase in Δ-high density lipoprotein (ΔHDL) between silymarin and placebo (P<0.000) and also between rosuvastatin and placebo (p=0.044). The level of Δ-triglycerides (ΔTG) in the silymarin group has a significant decrease compared to both the placebo and the rosuvastatin group (p<0.000 and p=0.036, respectively). The Δ-superoxide dismutase (ΔSOD) level in the silymarin group compared to placebo and rosuvastatin had a significant increase (p<0.000 and p=0.008, respectively). The ΔAβ1-42/Aβ1-40 in the silymarin group compared to both the placebo and rosuvastatin groups had a significant increase (p<0.05). There was an inverse relationship between ΔTG and ΔAβ1-42/Aβ1-40 (p=-0.493 and p=0.004). ΔAβ1-42/Aβ1-40 has a direct statistical relationship with ΔSOD marker (p=0.388 and p=0.031). Also, there was a direct correlation between the level of ΔAβ1-42/Aβ1-40 and ΔsLRP1/sRAGE (p=0.491 and p=0.005).

Conclusion

Our study showed the relationship between plasma lipids, especially ΔTG and ΔHDL, with ΔAβ1-42/Aβ1-40 in dyslipidemic AD patients, and modulation of these lipid factors can be used to monitor the response to treatments.

Effect of Sacubitril/Valsartan on Cognitive Function in Patients With Heart Failure With Preserved Ejection Fraction: A Prespecified Analysis of PARAGON-HF

BACKGROUND

A hypothetical concern has been raised that sacubitril/valsartan might cause cognitive impairment because neprilysin is one of several enzymes degrading amyloid-β peptides in the brain, some of which are neurotoxic and linked to Alzheimer-type dementia. To address this, we examined the effect of sacubitril/valsartan compared with valsartan on cognitive function in patients with heart failure with preserved ejection fraction in a prespecified substudy of PARAGON-HF (Prospective Comparison of Angiotensin Receptor Neprilysin Inhibitor With Angiotensin Receptor Blocker Global Outcomes in Heart Failure With Preserved Ejection Fraction).

METHODS

In PARAGON-HF, serial assessment of cognitive function was conducted in a subset of patients with the Mini-Mental State Examination (MMSE; score range, 0-30, with lower scores reflecting worse cognitive function). The prespecified primary analysis of this substudy was the change from baseline in MMSE score at 96 weeks. Other post hoc analyses included cognitive decline (fall in MMSE score of ≥3 points), cognitive impairment (MMSE score <24), or the occurrence of dementia-related adverse events.

RESULTS

Among 2895 patients included in the MMSE substudy with baseline MMSE score measured, 1453 patients were assigned to sacubitril/valsartan and 1442 to valsartan. Their mean age was 73 years, and the median follow-up was 32 months. The mean±SD MMSE score at randomization was 27.4±3.0 in the sacubitril/valsartan group, with 10% having an MMSE score <24; the corresponding numbers were nearly identical in the valsartan group. The mean change from baseline to 96 weeks in the sacubitril/valsartan group was -0.05 (SE, 0.07); the corresponding change in the valsartan group was -0.04 (0.07). The mean between-treatment difference at week 96 was -0.01 (95% CI, -0.20 to 0.19; P=0.95). Analyses of a ≥3-point decline in MMSE, decrease to a score <24, dementia-related adverse events, and combinations of these showed no difference between sacubitril/valsartan and valsartan. No difference was found in the subgroup of patients tested for apolipoprotein E ε4 allele genotype.

CONCLUSIONS

Patients with heart failure with preserved ejection fraction in PARAGON-HF had relatively low baseline MMSE scores. Cognitive change, measured by MMSE, did not differ between treatment with sacubitril/valsartan and treatment with valsartan in patients with heart failure with preserved ejection fraction.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT01920711.

The Interplay of Protein Aggregation, Genetics, and Oxidative Stress in Alzheimer's Disease: Role for Natural Antioxidants and Immunotherapeutics

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that comprises amyloid-beta protein (Aβ) as a main component of neuritic plaques. Its deposition is considered a trigger for AD pathogenesis, progression, and the clinical symptoms of cognitive impairment. Some distinct pathological features of AD include phosphorylation of tau protein, oxidative stress, and mitochondrial dysfunction. These pathological consequences tend to produce reactive oxygen species (ROS), resulting in the dysregulation of various signaling pathways of neuroinflammation and neurodegeneration. The relationship between the Aβ cascade and oxidative stress in AD pathogenesis is like a "chicken and egg" story, with the etiology of the disease regarding these two factors remaining a question of "which comes first." However, in this review, we have tried our best to clarify the interconnection between these two mechanisms and to show the precise cause-and-effect relationship. Based on the above hallmarks of AD, several therapeutic strategies using natural antioxidants, monoclonal antibodies, and vaccines are employed as anti-Aβ therapy to decrease ROS, Aβ burden, chronic neuroinflammation, and synaptic failure. These natural antioxidants and immunotherapeutics have demonstrated significant neuroprotective effects and symptomatic relief in various in vitro and in vivo models, as well as in clinical trials for AD. However, none of them have received final approval to enter the drug market for mitigating AD. In this review, we extensively elaborate on the pitfalls, assurances, and important crosstalk between oxidative stress and Aβ concerning current anti-Aβ therapy. Additionally, we discuss future strategies for the development of more Aβ-targeted approaches and the optimization of AD treatment and mitigation.

Consequences of Amyloid-β Deficiency for the Liver

The hepatic content of amyloid beta (Aβ) decreases drastically in human and rodent cirrhosis highlighting the importance of understanding the consequences of Aβ deficiency in the liver. This is especially relevant in view of recent advances in anti-Aβ therapies for Alzheimer's disease (AD). Here, it is shown that partial hepatic loss of Aβ in transgenic AD mice immunized with Aβ antibody 3D6 and its absence in amyloid precursor protein (APP) knockout mice (APP-KO), as well as in human liver spheroids with APP knockdown upregulates classical hallmarks of fibrosis, smooth muscle alpha-actin, and collagen type I. Aβ absence in APP-KO and deficiency in immunized mice lead to strong activation of transforming growth factor-β (TGFβ), alpha secretases, NOTCH pathway, inflammation, decreased permeability of liver sinusoids, and epithelial-mesenchymal transition. Inversely, increased systemic and intrahepatic levels of Aβ42 in transgenic AD mice and neprilysin inhibitor LBQ657-treated wild-type mice protect the liver against carbon tetrachloride (CCl4)-induced injury. Transcriptomic analysis of CCl4-treated transgenic AD mouse livers uncovers the regulatory effects of Aβ42 on mitochondrial function, lipid metabolism, and its onco-suppressive effects accompanied by reduced synthesis of extracellular matrix proteins. Combined, these data reveal Aβ as an indispensable regulator of cell-cell interactions in healthy liver and a powerful protector against liver fibrosis.

Minding the Gap: Exploring Neuroinflammatory and Microglial Sex Differences in Alzheimer's Disease

Research into Alzheimer's Disease (AD) describes a link between AD and the resident immune cells of the brain, the microglia. Further, this suspected link is thought to have underlying sex effects, although the mechanisms of these effects are only just beginning to be understood. Many of these insights are the result of policies put in place by funding agencies such as the National Institutes of Health (NIH) to consider sex as a biological variable (SABV) and the move towards precision medicine due to continued lackluster therapeutic options. The purpose of this review is to provide an updated assessment of the current research that summarizes sex differences and the research pertaining to microglia and their varied responses in AD.