Current Alzheimer Research - Volume 21, Issue 4, 2024

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disorder, with a significant burden on global health. AD is characterized by a progressive cognitive decline and memory loss. Emerging research suggests a potential link between periodontitis, specifically the presence of oral bacteria such as Porphyromonas gingivalis (P. gingivalis), and AD progression. P. gingivalis produces an enzyme, Agmatine deiminase (AgD), which converts agmatine to N-carbamoyl putrescine (NCP), serving as a precursor to essential polyamines. Recent studies have confirmed the correlation between disruptions in polyamine metabolism and cognitive impairment.

This study aims to investigate the dysregulation of P. gingivalis Agmatine deiminase (PgAgD) in the context of AD.

Saliva samples were collected from a total of 54 individuals, including 27 AD patients and 27 healthy controls. The expression of the PgAgD gene was analyzed using quantitative Real-Time PCR.

The results showed a significant decrease in PgAgD gene expression in the saliva samples of AD patients compared to healthy controls. This downregulation was found in AD patients with advanced stages of periodontitis. Additionally, a correlation was observed between the decrease in PgAgD expression and the 30-item Mini-Mental State Examination (MMSE) score.

These findings suggest that measuring PgAgD expression in saliva could be a noninvasive tool for monitoring AD progression and aid in the early diagnosis of patients with periodontitis. Further research is needed to validate our results and explore the underlying mechanisms linking periodontitis, PgAgD expression, and AD pathophysiology.

Neurodegenerative disorders like Alzheimer's disease (AD) involve the abnormal aggregation of tau protein, which forms toxic oligomers and amyloid deposits. The structure of tau protein is influenced by the conformational states of distinct proline residues, which are regulated by peptidyl-prolyl isomerases (PPIases). However, there has been no research on the impact of human cyclophilin A (CypA) as a PPIase on (non-phosphorylated) tau protein aggregation.

On the basis of these explanations, we used various spectroscopic techniques to explore the effects of CypA on tau protein aggregation behavior.

We demonstrated the role of the isomerization activity of CypA in promoting the formation of tau protein amyloid fibrils with well-defined and highly ordered cross-β structures. According to the “cistauosis hypothesis,” CypA's ability to enhance tau protein fibril formation in AD is attributed to the isomerization of specific proline residues from the trans to cis configuration. To corroborate this theory, we conducted refolding experiments using lysozyme as a model protein. The presence of CypA increased lysozyme aggregation and impeded its refolding process. It is known that proper refolding of lysozyme relies on the correct (trans) isomerization of two critical proline residues.

Thus, our findings confirmed that CypA induces the trans-to-cis isomerization of specific proline residues, ultimately leading to increased aggregation. Overall, this study highlights the emerging role of isomerization in tau protein pathogenesis in AD.

The aim of the study was to investigate the factors that underpin neuropsychiatric symptoms and how they might evolve over time in people with Mild Cognitive Impairment (MCI) and Alzheimer’s disease (AD) dementia.

Neuropsychiatric symptoms are psychiatric and behavioural manifestations that occur in people with AD. These are highly prevalent along the continuum of the disease, including at the stage of MCI, as well as before cognitive decline. Various small- and large-scale projects have investigated the underlying factors that underpin these symptoms; however, the identification of clear clusters is still a matter of debate; furthermore, no study has investigated how the clusters might change across the development of AD pathology by comparing different time points.

Our objective was to investigate the factors that underpin neuropsychiatric symptoms in Alzheimer’s disease (AD) and Mild Cognitive Impairment (MCI) and to assess how the loadings might differ based on considerations such as the disease stage of the samples.

Data was obtained from the Alzheimer’s Disease Neuroimaging Initiative database (adni.loni.usc.edu), using scores from the Neuropsychiatric Inventory, followed up yearly from baseline until month 72. Participant groups included those with MCI or AD dementia, or a mixture of both, with all participants presenting with at least one neuropsychiatric symptom. A series of exploratory Principal Component and Factor (Principal Axis) Analyses were performed using Direct Oblimin rotation.

The best-fitting structure was interpreted for each time point. A consistent, unique structure could not be identified, as the factors were unstable over time, both within the MCI and AD groups. However, some symptoms showed a tendency to load on the same factors across most measurements (i.e., agitation with irritability, depression with anxiety, elation with disinhibition, delusions with hallucinations).

Although the analyses revealed some degree of co-occurrence of neuropsychiatric symptoms across time points/samples, there was also considerable variation. In the AD group, more discrete syndromes were evident at the early time points, whereas a more complex picture of co-occurring symptoms, with differences likely reflecting disease staging, was seen at later time points. As a clear and distinctive factor structure was not consistently identified across time points/samples, this highlights the potential importance of sample selection (e.g., disease stage and/or heterogeneity) when studying, for example, the neurobiological underpinnings of neuropsychiatric symptoms.

Alzheimer's disease (AD) affects approximately 50 million people globally and is expected to triple by 2050. Arctiin is a lignan found in the Arctium lappa L. plant. Arctiin possesses anti-proliferative, antioxidative and anti-adipogenic.

We aimed to explore the potential therapeutic effects of Arctiin on rats with AD by evaluating the expression of TLR4, NLRP3, STAT3, TGF-β, cyclin D1, and CDK2.

AD was induced in rats by administering 70 mg/kg of aluminum chloride through intraperitoneal injection daily for six weeks. After inducing AD, some rats were treated with 25 mg/kg of Arctiin daily for three weeks through oral gavage. Furthermore, to examine the brain tissue structure, hippocampal sections were stained with hematoxylin/eosin and anti-TLR4 antibodies. The collected samples were analyzed for gene expression and protein levels of TLR4, NLRP3, STAT3, TGF-β, cyclin D1, and CDK2.

In behavioral tests, rats showed a significant improvement in their behavior when treated with Arctiin. Microimages stained with hematoxylin/eosin showed that Arctiin helped to improve the structure and cohesion of the hippocampus, which was previously impaired by AD. Furthermore, Arctiin reduced the expression of TLR4, NLRP3, STAT3, TGF-β, cyclin D1, and CDK2.

Arctiin can enhance rats’ behavior and structure of the hippocampus in AD rats. This is achieved through its ability to reduce the expression of both TLR4 and NLRP3, hence inhibiting the inflammasome pathway. Furthermore, Arctiin can improve tissue fibrosis by regulating STAT3 and TGF-β. Lastly, it can block the cell cycle proteins cyclin D1 and CDK2.

The Corpus Callosum (CC) is the largest commissural tract in the nervous system. Few studies have examined the extent of CC in Alzheimer's disease (AD) patients, and these studies have reported conflicting findings.

The study was performed using 176 brain MRI images of 88 Alzheimer's patients (55 women-32 men) and 88 healthy individuals (44 women-44 men).

In our study, 7 different parameters of the CC were measured, and their average values were determined. We measured each parameter separately in AD patients and healthy individuals and compared them with each other.

CC has an important place not only in Patients with AD but also in other neurodegenerative diseases. We consider that our study will be useful in the evaluation of Patients with AD.