Spatial cognition is associated with levels of phosphorylated-tau and β-amyloid in clinically normal older adults

Network pharmacology and experimental verification to explore the molecular mechanisms of Astragaloside IV against diabetic encephalopathy

PURPOSE

Diabetic encephalopathy (DE) is a neurological complication caused by diabetes mellitus, and its underlying mechanism has not been fully clarified. Astragaloside IV (AS-IV) has been demonstrated to have treatment effects on multiple neurologic diseases. The objective of this research is to explore the role and underlying mechanism of AS-IV in the treatment of DE, utilizing the methods of network pharmacology and experimental validation.

METHODS

Multiple public databases were used to search for the targets of AS-IV. Gene Expression Omnibus (GEO) dataset (GSE16135) was analyzed to identify differentially expressed genes (DEGs) in DE. The Venn diagram was employed to determine the intersecting genes. These genes were considered potential therapeutic targets of AS-IV in DE and were annotated using bioinformatics techniques. Subsequently, a protein-protein interaction (PPI) network was constructed utilizing Cytoscape software to identify the core targets of action. Additionally, molecular docking was conducted to validate the binding affinity of AS-IV to the main targets. Finally, we validated the predictive outcomes of network pharmacology in a DE rat model induced by intraperitoneal injection of streptozotocin (STZ).

RESULTS

Through the application of network pharmacology and bioinformatics analyses, we discovered the top two hub targets (EGFR and JAK2). Subsequent molecular docking analysis showed that AS-IV was precisely located within the binding sites of both EGFR and JAK2, with binding energies of -8.18 kJ/mol and -10.94 kJ/mol, respectively. Behavioral experiments demonstrated that the treated rats showed improvements in cognitive impairment. Following AS-IV treatment, there was a significant reduction in amyloid-β (Aβ) plaques deposition and neurofibrillary tangles in the hippocampal tissue of DE rats. Furthermore, TUNEL staining and Western blot analyses demonstrated that AS-IV suppressed neuronal apoptosis and inhibited the activation of the EGFR/JAK2/STAT3 signaling pathway.

CONCLUSION

These results demonstrated that the AS-IV has the potential to improve cognitive impairment in DE rats by mitigating neuronal apoptosis through the EGFR/JAK2/STAT3 signaling pathway, which provides important implications for the treatment of DE.

Association of hippocampal atrophy with tau pathology of temporal regions in preclinical Alzheimer's disease

BackgroundHippocampal atrophy is linked to memory and cognitive deficits, preceding clinical diagnosis of mild cognitive impairment (MCI) by decades. Morphometry changes in the hippocampal formation (HF) and their relationship to tau deposition in non-demented individuals remains unclear.ObjectiveTo investigate morphometry changes in the HF and their association with tau deposition in a non-demented cohort.MethodsEighty-three subjects from the Alzheimer's Disease Neuroimaging Initiative (ADNI) underwent T1-weighted MRI and Tau-PET scans at baseline and longitudinal follow-up. Participants were divided into amyloid-negative (Aβ-) and amyloid-positive (Aβ+) groups. Hippocampal volume/thickness were measured, and associations with tau deposition in temporal regions were examined using multivariable linear regression.ResultsNo significant association was found between the hippocampal volume/thickness and tau deposition of temporal regions for the Aβ- group. For the Aβ+ group, the hippocampal thickness was significantly associated with tau deposition of entorhinal cortex (ERC) for both hemispheres, and temporal pole, inferior temporal, and middle temporal regions for right hippocampi with the longitudinal follow up scans, while no significant association with the baseline scans. It was interesting that there was strong association between the baseline tau deposition of ERC and temporal pole and the longitudinal follow up thickness of left hippocampi, while the associated regions for the right hemisphere were ERC, temporal pole, and inferior temporal regions.ConclusionsHippocampal atrophy may precede cognitive symptoms, with tau deposition in adjacent temporal regions contributing to hippocampal changes. The right HF appears more vulnerable than the left, indicating hemispheric differences in pathology.

Rotation errors in path integration are associated with Alzheimer's disease tau pathology: a cross-sectional study

BACKGROUND

Early Alzheimer's disease diagnosis is crucial for preventive therapy development. Standard neuropsychological evaluation does not identify clinically normal individuals with brain amyloidosis, the first stage of the pathology, defined as preclinical Alzheimer's disease. Spatial navigation assessment, in particular path integration, appears promising to detect preclinical symptoms, as the medial temporal lobe plays a key role in navigation and is the first cortical region affected by tau pathology.

METHODS

We have conducted a cross-sectional study. We related the path integration performance of 102 individuals without dementia, aged over 50, to amyloid and tau pathologies, measured using positron emission tomography. We included 75 clinically normal individuals (19 with brain amyloidosis, 56 without) and 27 individuals with mild cognitive impairment (18 with brain amyloidosis, 9 without). We fitted linear mixed models to predict the path integration performances according to amyloid status or tau pathology in the medial temporal lobal, adjusting for age, gender, cognitive status, education, and video game experience. We decomposed the error into rotation and distance errors.

RESULTS

We observed that clinically normal adults with brain amyloidosis (preclinical Alzheimer's disease) had spatial navigation deficits when relying only on self-motion cues. However, they were able to use a landmark to reduce their errors. Individuals with mild cognitive impairment had deficits in path integration that did not improve when a landmark was added in the environment. The amyloid status did not influence performance among individuals with mild cognitive impairment. Among all individuals, rotation, but not distance, errors increased with the level of tau pathology in the medial temporal lobe.

CONCLUSION

Our results suggest that path integration performance in an environment without external cues allows identifying individuals with preclinical Alzheimer's disease, before overt episodic memory impairment is noticeable. Specifically, we demonstrated that poor angular estimation is an early cognitive marker of tau pathology, whereas distance estimation relates to older ages, not to Alzheimer's disease.

TRIAL REGISTRATION

Eudra-CT 2018-003473-94.

An experimental framework for conjoint measures of olfaction, navigation, and motion as pre-clinical biomarkers of Alzheimer's disease

Elucidating Alzheimer's disease (AD) prodromal symptoms can resolve the outstanding challenge of early diagnosis. Based on intrinsically related substrates of olfaction and spatial navigation, we propose a novel experimental framework for their conjoint study. Artificial intelligence-driven multimodal study combining self-collected olfactory and motion data with available big clinical datasets can potentially promote high-precision early clinical screenings to facilitate timely interventions targeting neurodegenerative progression.

Entorhinal-based path integration selectively predicts midlife risk of Alzheimer's disease

INTRODUCTION

Entorhinal cortex (EC) is the first cortical region to exhibit neurodegeneration in Alzheimer's disease (AD), associated with EC grid cell dysfunction. Given the role of grid cells in path integration (PI)-based spatial behaviors, we predicted that PI impairment would represent the first behavioral change in adults at risk of AD.

METHODS

We compared immersive virtual reality (VR) PI ability to other cognitive domains in 100 asymptomatic midlife adults stratified by hereditary and physiological AD risk factors. In some participants, behavioral data were compared to 7T magnetic resonance imaging (MRI) measures of brain structure and function.

RESULTS

Midlife PI impairments predicted both hereditary and physiological AD risk, with no corresponding multi-risk impairment in episodic memory or other spatial behaviors. Impairments associated with altered functional MRI signal in the posterior-medial EC.

DISCUSSION

Altered PI may represent the transition point from at-risk state to disease manifestation in AD, prior to impairment in other cognitive domains.