Vascular Risk Factors and Alzheimer's Disease: Blood-Brain Barrier Disruption, Metabolic Syndromes, and Molecular Links

Hypertension and Cognitive Disorders

Systemic hypertension is possibly the most important modifiable risk factor for the development of cognitive decline, both for mild cognitive impairment (MCI) and dementia. For effective blood pressure (BP) control, it requires proper assessment, using brachial, central, and ambulatory measurements, and monitoring with a focus on different BP parameters. Different BP parameters like pulse pressure, mean arterial pressure, BP variability, and circadian parameters, like nondippers and early morning surge, should be considered in the evaluation for the risk of cognitive decline due to hypertension in middle age and older adults. Chronic hypertension causes vascular remodeling in the brain and leads to brain failure or cognitive decline. Achieving specific BP goals can improve clinical outcomes and possibly slow down cognitive decline for patients with comorbid hypertension and cognitive impairment.

Association of preoperative to postoperative change in cerebrospinal fluid fibrinogen with postoperative delirium

Background

We aimed to assess perioperative changes in fibrinogen in the cerebrospinal fluid (CSF), their association with markers of blood-brain barrier breakdown and neuroinflammation, and their association with postoperative delirium severity.

Methods

We conducted a secondary analysis of the Interventions for Postoperative Delirium-Biomarker 2 (IPOD-B2, NCT02926417) study, a prospective observational cohort study. We included 24 patients aged >21 yr undergoing aortic aneurysm repair. CSF samples were obtained before (n=24) and after surgery (n=13), with some participants having multiple postoperative samples. Our primary outcome was the perioperative change in CSF fibrinogen. Delirium was assessed using the Delirium Rating Scale-Revised-98.

Results

CSF fibrinogen increased after surgery (P<0.001), and this was associated with an increase in CSF/plasma albumin ratio (β=1.09, 95% CI 0.47-1.71, P=0.004). The peak change in CSF fibrinogen was associated with the change in CSF interleukin (IL)-10 and IL-12p70. The peak change in CSF fibrinogen was associated with the change in CSF total tau (β=0.47, 95% CI 0.24-0.71, P=0.002); however, we did not observe an association with postoperative delirium severity (incidence rate ratio = 1.20, 95% CI 0.66-2.17, P=0.540).

Conclusions

Our preliminary findings support the hypothesis that fibrinogen enters the brain via blood-brain barrier disruption, promoting neuroinflammation and neuronal injury. However, we did not observe an association between cerebrospinal fluid fibrinogen and peak delirium severity in this limited cohort.

Age of onset moderates the effects of Vascular Risk Factors on Neurodegeneration, Blood-Brain-Barrier permeability, and cognitive decline in Alzheimer's Disease

BACKGROUND

The role of Vascular risk factors (VRFs) in the progression of Alzheimer's Disease (AD) and cognitive decline remains to be elucidated, with previous studies resulting in conflicting findings. The possible impact of age-specific mechanisms of resilience/vulnerability is an under addressed issue. We evaluated the association of VRFs with markers of amyloid deposition, neurodegeneration, and blood-brain-barrier (BBB) permeability (Albumin quotient, Qalb), stratifying patients into early-onset (< 65, EOAD), classic late-onset (65-75, cLOAD) and very late-onset (> 75, vLOAD), to evaluate the moderating effect of age of onset. Moreover, we explored the effects of VRFs on cognitive decline at one year follow-up (ΔMMSE).

METHODS

For 368 patients with biologically confirmed AD, we computed eight risk factors in a composite measure of cumulative vascular risk (vascular score, VS). Stratifying patients according to age of onset, we regressed VS and main individual VRFs on p-tau/Aβ42, t-tau and Qalb, and used bootstrapped mediation analysis to test direct and indirect associations of VS with t-tau, using Qalb as mediator. In a subset of 105 patients, we performed multivariate backward regressions to assess the effects of sex, APOE, Qalb, VS, p-tau/Aβ42 and t-tau on ΔMMSE.

RESULTS

VS was positively associated with CSF t-tau in more vulnerable groups burdened by more aggressive disease progression (EOAD: β = 0.256, p = 0.019) or aging (vLOAD: β = 0.007, p < 0.001). Conversely, in patients with classic age of onset VS was associated with higher BBB permeability (cLOAD: β = 0.173, p = 0.015), which simultaneously causes the decrease of CSF t-tau, as a possible resilience response. Cognitive decline was not associated with VS in any of the subgroups. Instead, it was affected by both higher CSF t-tau and increased Qalb values in those with very early or very late onset (EOAD and vLOAD), but by Qalb alone in patients with classic age of onset, where CSF t-tau levels might be buffered by BBB permeability.

CONCLUSIONS

Our results show that age of onset weighs on the heterogeneous effects played by VRFs in AD, which do not seem to have direct impact on cognitive decline. These findings stress the importance of a tailored patient-centered approach to the application of vascular prevention strategies in AD.

The Predictive Value of PKC and ET-1 Levels in Cerebrospinal Fluid for Vasospasm and Prognosis in Patients with Aneurysmal Subarachnoid Hemorrhage

Objective

To analyze the predictive value of protein kinase C (PKC) and endothelin-1 (ET-1) in cerebrospinal fluid for vasospasm and prognosis in patients with aneurysmal subarachnoid hemorrhage (ASH).

Methods

One hundred and forty-eight ASH patients hospitalized in our hospital during February 2019 to February 2022 were optioned as observation subjects. These subjects were graded into good prognosis group (mRS score 0-2, n = 102) and poor prognosis group (mRS score 3-6, n = 46) according to the Rankin Revised Scale Score (mRS) after 6 months of follow-up. Cerebrospinal fluid was collected from patients to detect the content of ET-1 and PKC. The prognostic factors were analyzed using multifactorial logistic regression. The predictive value was assessed using receiver operating characteristic (ROC) curve.

Results

The patients with poor prognosis had a higher age level and a higher proportion of ≥2 aneurysms, aneurysm diameter ≥6 mm, cerebral vasospasm, and Hunt-Hess grade ≥III than those with good prognosis (P < 0.05). The patients with poor prognosis had higher content of PKC and ET-1 than those with good prognosis (P < 0.05). Age, aneurysm diameter ≥6 mm, cerebral vasospasm, Hunt-Hess classification ≥grade III, PKC and ET-1 were all risk factors related to the prognosis of ASH (P < 0.05). The area under the curve (AUC) of PKC and ET-1 for diagnosing poor prognosis of ASH was 0.803 and 0.720, respectively. The AUC of the combined detection was 0.873 (P < 0.05). Patients with cerebrovascular spasm had higher content of PKC and ET-1 than those without (P < 0.05). The AUC of PKC and ET-1 for diagnosing cerebral vasospasm in ASH was 0.891 and 0.816, respectively, which was 0.932 for combined detection (P < 0.05).

Conclusion

The combination of PKC and ET-1 in cerebrospinal fluid had certain value in predicting the poor prognosis of patients with ASH.

Loss of the APP regulator RHBDL4 preserves memory in an Alzheimer's disease mouse model

Characteristic cerebral pathological changes of Alzheimer's disease (AD) such as glucose hypometabolism or the accumulation of cleavage products of the amyloid precursor protein (APP), known as Aβ peptides, lead to sustained endoplasmic reticulum (ER) stress and neurodegeneration. To preserve ER homeostasis, cells activate their unfolded protein response (UPR). The rhomboid-like-protease 4 (RHBDL4) is an enzyme that participates in the UPR by targeting proteins for proteasomal degradation. We demonstrated previously that RHBLD4 cleaves APP in HEK293T cells, leading to decreased total APP and Aβ. More recently, we showed that RHBDL4 processes APP in mouse primary mixed cortical cultures as well. Here, we aim to examine the physiological relevance of RHBDL4 in the brain. We first found that brain samples from AD patients and an AD mouse model (APPtg) showed increased RHBDL4 mRNA and protein expression. To determine the effects of RHBDL4's absence on APP physiology in vivo, we crossed APPtg mice to a RHBDL4 knockout (R4-/-) model. RHBDL4 deficiency in APPtg mice led to increased total cerebral APP and amyloidogenic processing when compared to APPtg controls. Contrary to expectations, as assessed by cognitive tests, RHBDL4 absence rescued cognition in 5-month-old female APPtg mice. Informed by unbiased RNAseq data, we demonstrated in vitro and in vivo that RHBDL4 absence leads to greater levels of active β-catenin due to decreased proteasomal clearance. Decreased β-catenin activity is known to underlie cognitive defects in APPtg mice and AD. Our work suggests that RHBDL4's increased expression in AD, in addition to regulating APP levels, leads to aberrant degradation of β-catenin, contributing to cognitive impairment.

The vascular contribution of apolipoprotein E to Alzheimer's disease

Alzheimer's disease, the most prevalent form of dementia, imposes a substantial societal burden. The persistent inadequacy of disease-modifying drugs targeting amyloid plaques and neurofibrillary tangles suggests the contribution of alternative pathogenic mechanisms. A frequently overlooked aspect is cerebrovascular dysfunction, which may manifest early in the progression of Alzheimer's disease pathology. Mounting evidence underscores the pivotal role of the apolipoprotein E gene, particularly the apolipoprotein ε4 allele as the strongest genetic risk factor for late-onset Alzheimer's disease, in the cerebrovascular pathology associated with Alzheimer's disease. In this review, we examine the evidence elucidating the cerebrovascular impact of both central and peripheral apolipoprotein E on the pathogenesis of Alzheimer's disease. We present a novel three-hit hypothesis, outlining potential mechanisms that shed light on the intricate relationship among different pathogenic events. Finally, we discuss prospective therapeutics targeting the cerebrovascular pathology associated with apolipoprotein E and explore their implications for future research endeavours.

Quantitative transport mapping of multi-delay arterial spin labeling MRI detects early blood perfusion alterations in Alzheimer's disease

BACKGROUND

Quantitative transport mapping (QTM) of blood velocity, based on the transport equation has been demonstrated higher accuracy and sensitivity of perfusion quantification than the traditional Kety's method-based cerebral blood flow (CBF). This study aimed to investigate the associations between QTM velocity and cognitive function in Alzheimer's disease (AD) using multiple post-labeling delay arterial spin labeling (ASL) MRI.

METHODS

A total of 128 subjects (21 normal controls (NC), 80 patients with mild cognitive impairment (MCI), and 27 AD) were recruited prospectively. All participants underwent MRI examination and neuropsychological evaluation. QTM velocity and traditional CBF maps were computed from multiple delay ASL. Regional quantitative perfusion measurements were performed and compared to study group differences. We tested the hypothesis that cognition declines with reduced cerebral blood perfusion with consideration of age and gender effects.

RESULTS

In cortical gray matter (GM) and the hippocampus, QTM velocity and CBF showed decreased values in the AD group compared to NC and MCI groups; QTM velocity, but not CBF, showed a significant difference between MCI and NC groups. QTM velocity and CBF showed values decreasing with age; QTM velocity, but not CBF, showed a significant gender difference between male and female. QTM velocity and CBF in the hippocampus were positively correlated with cognition, including global cognition, memory, executive function, and language function.

CONCLUSION

This study demonstrated an increased sensitivity of QTM velocity as compared with the traditional Kety's method-based CBF. Specifically, we observed only in QTM velocity, reduced perfusion velocity in GM and the hippocampus in MCI compared with NC. Both QTM velocity and CBF demonstrated a reduction in AD vs. controls. Decreased QTM velocity and CBF in the hippocampus were correlated with poor cognitive measures. These findings suggest QTM velocity as potential biomarker for early AD blood perfusion alterations and it could provide an avenue for early intervention of AD.

Retinal peri-arteriolar versus peri-venular amyloidosis, hippocampal atrophy, and cognitive impairment: exploratory trial

The relationship between amyloidosis and vasculature in cognitive impairment and Alzheimer's disease (AD) pathogenesis is increasingly acknowledged. We conducted a quantitative and topographic assessment of retinal perivascular amyloid plaque (AP) distribution in individuals with both normal and impaired cognition. Using a retrospective dataset of scanning laser ophthalmoscopy fluorescence images from twenty-eight subjects with varying cognitive states, we developed a novel image processing method to examine retinal peri-arteriolar and peri-venular curcumin-positive AP burden. We further correlated retinal perivascular amyloidosis with neuroimaging measures and neurocognitive scores. Our study unveiled that peri-arteriolar AP counts surpassed peri-venular counts throughout the entire cohort (P < 0.0001), irrespective of the primary, secondary, or tertiary vascular branch location, with a notable increase among cognitively impaired individuals. Moreover, secondary branch peri-venular AP count was elevated in the cognitively impaired (P < 0.01). Significantly, peri-venular AP count, particularly in secondary and tertiary venules, exhibited a strong correlation with clinical dementia rating, Montreal cognitive assessment score, hippocampal volume, and white matter hyperintensity count. In conclusion, our exploratory analysis detected greater peri-arteriolar versus peri-venular amyloidosis and a marked elevation of amyloid deposition in secondary branch peri-venular regions among cognitively impaired subjects. These findings underscore the potential feasibility of retinal perivascular amyloid imaging in predicting cognitive decline and AD progression. Larger longitudinal studies encompassing diverse populations and AD-biomarker confirmation are warranted to delineate the temporal-spatial dynamics of retinal perivascular amyloid deposition in cognitive impairment and the AD continuum.

No Replication of Alzheimer's Disease Genetics as a Moderator of Combat Exposure's Association with PTSD risk in 138,592 Combat Veterans

Large-scale cohort and epidemiological studies suggest that posttraumatic stress disorder (PTSD) confers risk for late-onset Alzheimer's disease (AD) and related dementias (ADRD); however, the basis for this association remains unclear. Several prior studies of military Veterans have reported that carriers of the apolipoprotein E (APOE) ε4 gene variant are at heightened risk for the development of PTSD following combat exposure, suggesting that PTSD and ADRD may share some genetic risk. This cohort study was designed to further examine the hypothesis that ADRD genetic risk also confers risk for PTSD. To do so, we examined APOE ε4 and ε2 genotypes, an AD polygenic risk score (PRS), and other Veteran-relevant risk factors for PTSD in age-stratified groups of individuals of European (n = 123,372) and African (n = 15,220) ancestry in the US Department of Veterans Affairs' Million Veteran Program. Analyses revealed no significant main effect associations between the APOE ε4 (or ε2) genotype or the AD PRS on PTSD severity or diagnosis. There were also no significant interactions between measures of AD genetic risk and either combat exposure severity or history of head injury in association with PTSD in any age group. We conclude that the association between PTSD and the primary ADRD genetic risk factor, APOE ε4, that was reported previously was not replicable in the largest relevant dataset in the world. Thus, the epidemiological association between PTSD and ADRD is not likely to be driven by the major genetic factors underlying ADRD risk.

Constitutive NOS Production Is Modulated by Alzheimer's Disease Pathology Depending on APOE Genotype

Both the endothelial (eNOS) and the neuronal (nNOS) isoforms of constitutive Nitric Oxide Synthase have been implicated in vascular dysfunctions in Alzheimer's disease (AD). We aimed to explore the relationship between amyloid pathology and NO dynamics by comparing the cerebrospinal fluid (CSF) levels of nNOS and eNOS of 8 healthy controls (HC) and 27 patients with a clinical diagnosis of Alzheimer's disease and isolated CSF amyloid changes, stratified according to APOE ε genotype (APOE ε3 = 13, APOE ε4 = 14). Moreover, we explored the associations between NOS isoforms, CSF AD biomarkers, age, sex, cognitive decline, and blood-brain barrier permeability. In our cohort, both eNOS and nNOS levels were increased in APOE ε3 with respect to HC and APOE ε4. CSF eNOS inversely correlated with CSF Amyloid-β42 selectively in carriers of APOE ε3; CSF nNOS was negatively associated with age and CSF p-tau only in the APOE ε4 subgroup. Increased eNOS could represent compensative vasodilation to face progressive Aβ-induced vasoconstriction in APOE ε3, while nNOS could represent the activation of NO-mediated plasticity strategies in the same group. Our results confirm previous findings that the APOE genotype is linked with different vascular responses to AD pathology.

Quantitative transport mapping of multi-delay arterial spin labeling MRI detects early blood perfusion alteration in Alzheimer's disease

Background

Quantitative transport mapping (QTM) of blood velocity, based on the transport equation has been demonstrated higher accuracy and sensitivity of perfusion quantification than the traditional Kety's method-based blood flow (Kety flow). This study aimed to investigate the associations between QTM velocity and cognitive function in Alzheimer's disease (AD) using multiple post-labeling delay arterial spin labeling (ASL) MRI.

Methods

A total of 128 subjects (21 normal controls (NC), 80 patients with mild cognitive impairment (MCI), and 27 AD) were recruited prospectively. All participants underwent MRI examination and neuropsychological evaluation. QTM velocity and traditional Kety flow maps were computed from multiple delay ASL. Regional quantitative perfusion measurements were performed and compared to study group differences. We tested the hypothesis that cognition declines with reduced cerebral blood flow with consideration of age and gender effects.

Results

In cortical gray matter (GM) and the hippocampus, QTM velocity and Kety flow showed decreased values in AD group compared to NC and MCI groups; QTM velocity, but not Kety flow, showed a significant difference between MCI and NC groups. QTM velocity and Kety flow showed values decreasing with age; QTM velocity, but not Kety flow, showed a significant gender difference between male and female. QTM velocity and Kety flow in the hippocampus were positively correlated with cognition, including global cognition, memory, executive function, and language function.

Conclusion

This study demonstrated an increased sensitivity of QTM velocity as compared with the traditional Kety flow. Specifically, we observed only in QTM velocity, reduced perfusion velocity in GM and the hippocampus in MCI compared with NC. Both QTM velocity and Kety flow demonstrated reduction in AD vs controls. Decreased QTM velocity and Kety flow in the hippocampus were correlated with cognitive measures. These findings suggest QTM velocity as an improved biomarker for early AD blood flow alterations.

Distinctive retinal peri-arteriolar versus peri-venular amyloid plaque distribution correlates with the cognitive performance

Introduction

The vascular contribution to Alzheimer's disease (AD) is tightly connected to cognitive performance across the AD continuum. We topographically describe retinal perivascular amyloid plaque (AP) burden in subjects with normal or impaired cognition.

Methods

Using scanning laser ophthalmoscopy, we quantified retinal peri-arteriolar and peri-venular curcumin-positive APs in the first, secondary and tertiary branches in twenty-eight subjects. Perivascular AP burden among cognitive states was correlated with neuroimaging and cognitive measures.

Results

Peri-arteriolar exceeded peri-venular AP count (p<0.0001). Secondary branch AP count was significantly higher in cognitively impaired (p<0.01). Secondary small and tertiary peri-venular AP count strongly correlated with clinical dementia rating, hippocampal volumes, and white matter hyperintensity count.

Discussion

Our topographic analysis indicates greater retinal amyloid accumulation in the retinal peri-arteriolar regions overall, and distal peri-venular regions in cognitively impaired individuals. Larger longitudinal studies are warranted to understand the temporal-spatial relationship between vascular dysfunction and perivascular amyloid deposition in AD.

Highlights

Retinal peri-arteriolar region exhibits more amyloid compared with peri-venular regions.Secondary retinal vascular branches have significantly higher perivascular amyloid burden in subjects with impaired cognition, consistent across sexes.Cognitively impaired individuals have significantly greater retinal peri-venular amyloid deposits in the distal small branches, that correlate with CDR and hippocampal volumes.

Effect of Vascular Risk Factors on Blood-Brain Barrier and Cerebrospinal Fluid Biomarkers Along the Alzheimer's Disease Continuum: A Retrospective Observational Study

BACKGROUND

Blood-brain barrier (BBB) dysfunction could favor the pathogenesis and progression of Alzheimer's disease (AD). Vascular risk factors (VRF) could worsen BBB integrity, thus promoting neurode generation.

OBJECTIVE

To investigate BBB permeability and its relation with VRF along the AD continuum (ADc). Cerebrospinal fluid (CSF) Amyloid (A) and p-tau (T) levels were used to stratify patients.

METHODS

We compared CSF/plasma albumin ratio (QAlb) of 131 AD patients and 24 healthy controls (HC). APOE genotype and VRF were evaluated for each patient. Spearman's Rho correlation was used to investigate the associations between Qalb and CSF AD biomarkers. Multivariate regression analyses were conducted to explore the relationship between Qalb and AD biomarkers, sex, age, cognitive status, and VRF.

RESULTS

QAlb levels did not show significant difference between ADc patients and HC (p = 0.984). However, QAlb was significantly higher in A + T-compared to A + T+ (p = 0.021). In ADc, CSF p-tau demonstrated an inverse correlation with QAlb, a finding confirmed in APOE4 carriers (p = 0.002), but not in APOE3. Furthermore, in APOE4 carriers, sex, hypertension, and hypercholesterolemia were associated with QAlb (p = 0.004, p = 0.038, p = 0.038, respectively), whereas only sex showed an association in APOE3 carriers (p = 0.026).

CONCLUSIONS

BBB integrity is preserved in ADc. Among AT categories, A + T-have a more permeable BBB than A + T+. In APOE4 carriers, CSF p-tau levels display an inverse association with BBB permeability, which in turn, seems to be affected by VRF. These data suggest a possible relationship between BBB efficiency, VRF and CSF p-tau levels depending on APOE genotype.

Alzheimer's Disease: Novel Targets and Investigational Drugs for Disease Modification

Novel agents addressing non-amyloid, non-tau targets in Alzheimer's Disease (AD) comprise 70% of the AD drug development pipeline of agents currently in clinical trials. Most of the target processes identified in the Common Alzheimer's Disease Research Ontology (CADRO) are represented by novel agents in trials. Inflammation and synaptic plasticity/neuroprotection are the CADRO categories with the largest number of novel candidate therapies. Within these categories, there are few overlapping targets among the test agents. Additional categories being evaluated include apolipoprotein E [Formula: see text] 4 (APOE4) effects, lipids and lipoprotein receptors, neurogenesis, oxidative stress, bioenergetics and metabolism, vascular factors, cell death, growth factors and hormones, circadian rhythm, and epigenetic regulators. We highlight current drugs being tested within these categories and their mechanisms. Trials will be informative regarding which targets can be modulated to produce a slowing of clinical decline. Possible therapeutic combinations of agents may be suggested by trial outcomes. Biomarkers are evolving in concert with new targets and novel agents, and biomarker outcomes offer a means of supporting disease modification by the putative treatment. Identification of novel targets and development of corresponding therapeutics offer an important means of advancing new treatments for AD.

Microbiota dysbiosis caused by dietetic patterns as a promoter of Alzheimer's disease through metabolic syndrome mechanisms

Microbiota dysbiosis and metabolic syndrome, consequences of a non-adequate diet, generate a feedback pathogenic state implicated in Alzheimer's disease development. The lower production of short chain fatty acids (SCFAs) under dysbiosis status leads to lipid homeostasis deregulation and decreases Angptl4 release and AMPK activation in the adipose tissue, promoting higher lipid storage (adipocyte hypertrophy) and cholesterol levels. Also, low SCFA generation reduces GPR41 and GPR43 receptor activation at the adipose tissue (increasing leptin release and leptin receptor resistance) and intestinal levels, reducing the release of GLP-1 and YPP. Therefore, lower satiety sensation and energy expenditure occur, promoting a weight gaining environment mediated by higher food intake and lipid storage, developing dyslipemia. In this context, higher glucose levels, together with higher free fatty acids in the bloodstream, promote glycolipotoxicity, provoking a reduction in insulin released, insulin receptor resistance, advanced glycation products (AGEs) and type 2 diabetes. Intestinal dysbiosis and low SCFAs reduce bacterial biodiversity, increasing lipopolysaccharide (LPS)-producing bacteria and intestinal barrier permeability. Higher amounts of LPS pass to the bloodstream (endotoxemia), causing a low-grade chronic inflammatory state characterized by higher levels of leptin, IL-1β, IL-6 and TNF-α, together with a reduced release of adiponectin and IL-10. At the brain and neuronal levels, the generated insulin resistance, low-grade chronic inflammation, leptin resistance, AGE production and LPS increase directly impact the secretase enzymes and tau hyperphosphorylation, creating an enabling environment for β-amyloid senile plaque and tau tangled formations and, as a consequence, Alzheimer's initiation, development and maintenance.

Effect of Refined Edible Oils on Neurodegenerative Disorders

Neurodegenerative diseases are comprise a prominent class of neurological diseases. Generally, neurodegenerative diseases cannot be cured, and the available treatments can only regulate the symptoms or delay the disease progression. Among the several factors which could clarify the possible pathogenesis of neurodegenerative diseases, next to aging as the main risk, the dietary related diseases are the most important. Vegetable oils, which are composed of triacyclglycerols as the main components and several other components in a trace amount, are the main part of our diet. This review aims to study the effect of refined or unrefined vegetable oil consumption as a preventive or aiding strategy to slow or halt the progression of neurodegenerative diseases. In the refining process, owing to the chemical materials or severe temperatures of the refining process, removal of the desirable minor components is sometimes unavoidable and thus a worrisome issue affecting physical and neurological health.

Antioxidant evaluation and computational prediction of prospective drug-like compounds from polyphenolic-rich extract of Hibiscus cannabinus L. seed as antidiabetic and neuroprotective targets: assessment through in vitro and in silico studies

BACKGROUND

Reports have implicated diabetes mellitus (DM) and Alzheimer's disease (AD) as some of the global persistent health challenges with no lasting solutions, despite of significant inputs of modern-day pharmaceutical firms. This study therefore, aimed to appraise the in vitro antioxidant potential, enzymes inhibitory activities, and as well carry out in silico study on bioactive compounds from polyphenolic-rich extract of Hibiscus cannabinus seed (PEHc).

METHODS

In vitro antioxidant assays were performed on PEHc using standard methods while the identification of phytoconstituents was carried out with high performance liquid chromatography (HPLC). For the in silico molecular docking using Schrodinger's Grid-based ligand docking with energetics software, seven target proteins were retrieved from the database ( https://www.rcsb.org/ ).

RESULTS

HPLC technique identified twelve chemical compounds in PEHc, while antioxidant quantification revealed higher total phenolic contents (243.5 ± 0.71 mg GAE/g) than total flavonoid contents (54.06 ± 0.09 mg QE/g) with a significant (p < 0.05) inhibition of ABTS (IC₅₀ = 218.30 ± 0.87 µg/ml) and 1, 1-diphenyl-2-picrylhydrazyl free radicals (IC₅₀ = 227.79 ± 0.74 µg/ml). In a similar manner, the extract demonstrated a significant (p < 0.05) inhibitory activity against α-amylase (IC₅₀ = 256.88 ± 6.15 µg/ml) and α-glucosidase (IC₅₀ = 183.19 ± 0.23 µg/ml) as well as acetylcholinesterase (IC₅₀ = 262.95 ± 1.47 µg/ml) and butyrylcholinesterase (IC₅₀ = 189.97 ± 0.82 µg/ml), respectively. Furthermore, In silico study showed that hibiscetin (a lead) revealed a very strong binding affinity energies for DPP-4, (PDB ID: 1RWQ) and α-amylase (PDB ID: 1SMD), gamma-tocopherol ( for peptide-1 receptor; PDB ID: 3C59, AChE; PDB ID: 4EY7 and BChE; PDB ID: 7B04), cianidanol for α-glucosidase; PDB ID: 7KBJ and kaempferol for Poly [ADP-ribose] polymerase 1 (PARP-1); PDB ID: 6BHV, respectively. More so, ADMET scores revealed drug-like potentials of the lead compounds identified in PEHc.

CONCLUSION

As a result, the findings of this study point to potential drug-able compounds in PEHc that could be useful for the management of DM and AD.

Evaluating the effect of acute diesel exhaust particle exposure on P-glycoprotein efflux transporter in the blood-brain barrier co-cultured with microglia

A growing public health concern, chronic Diesel Exhaust Particle (DEP) exposure is a heavy risk factor for the development of neurodegenerative diseases like Alzheimer's (AD). Considered the brain's first line of defense, the Blood-Brain Barrier (BBB) and perivascular microglia work in tandem to protect the brain from circulating neurotoxic molecules like DEP. Importantly, there is a strong association between AD and BBB dysfunction, particularly in the Aβ transporter and multidrug resistant pump, P-glycoprotein (P-gp). However, the response of this efflux transporter is not well understood in the context of environmental exposures, such as to DEP. Moreover, microglia are seldom included in in vitro BBB models, despite their significance in neurovascular health and disease. Therefore, the goal of this study was to evaluate the effect of acute (24 hr.) DEP exposure (2000 μg/ml) on P-gp expression and function, paracellular permeability, and inflammation profiles of the human in vitro BBB model (hCMEC/D3) with and without microglia (hMC3). Our results suggested that DEP exposure can decrease both the expression and function of P-gp in the BBB, and corroborated that DEP exposure impairs BBB integrity (i.e. increased permeability), a response that was significantly worsened by the influence of microglia in co-culture. Interestingly, DEP exposure seemed to produce atypical inflammation profiles and an unexpected general downregulation in inflammatory markers in both the monoculture and co-culture, which differentially expressed IL-1β and GM-CSF. Interestingly, the microglia in co-culture did not appear to influence the response of the BBB, save in the permeability assay, where it worsened the BBB's response. Overall, our study is important because it is the first (to our knowledge) to investigate the effect of acute DEP exposure on P-gp in the in vitro human BBB, while also investigating the influence of microglia on the BBB's responses to this environmental chemical.

Beyond Neighborhood Disadvantage: Local Resources, Green Space, Pollution, and Crime as Residential Community Correlates of Cardiovascular Risk and Brain Morphology in Midlife Adults

OBJECTIVE

Residing in communities characterized by socioeconomic disadvantage confers risk of cardiometabolic diseases. Residing in disadvantaged communities may also confer the risk of neurodegenerative brain changes via cardiometabolic pathways. This study tested whether features of communities-apart from conventional socioeconomic characteristics-relate not only to cardiometabolic risk but also to relative tissue reductions in the cerebral cortex and hippocampus.

METHODS

Participants were 699 adults aged 30 to 54 years (340 women; 22.5% non-White) whose addresses were geocoded to compute community indicators of socioeconomic disadvantage, as well as air and toxic chemical pollutant exposures, homicide rates, concentration of employment opportunities, land use (green space), and availability of supermarkets and local resources. Participants also underwent assessments of cortical and hippocampal volumes and cardiometabolic risk factors (adiposity, blood pressure, fasting glucose, and lipids).

RESULTS

Multilevel structural equation modeling demonstrated that cardiometabolic risk was associated with community disadvantage ( β = 0.10, 95% confidence interval [CI] = 0.01 to 0.18), as well as chemical pollution ( β = 0.11, 95% CI = 0.02 to 0.19), homicide rates ( β = 0.10, 95% CI = 0.01 to 0.18), employment opportunities ( β = -0.16, 95% CI = -0.27 to -0.04), and green space ( β = -0.12, 95% CI = -0.20 to -0.04). Moreover, cardiometabolic risk indirectly mediated the associations of several of these community features and brain tissue volumes. Some associations were nonlinear, and none were explained by participants' individual-level socioeconomic characteristics.

CONCLUSIONS

Features of communities other than conventional indicators of socioeconomic disadvantage may represent nonredundant correlates of cardiometabolic risk and brain tissue morphology in midlife.

Pathophysiological Association of Alzheimer's Disease and Hypertension: A Clinical Concern for Elderly Population

Alzheimer's disease (AD), the most common cause of dementia and the fifth leading cause of death in the adult population has a complex pathophysiological link with hypertension (HTN). A growing volume of published literature on a parallel elevation of blood pressure (BP), amyloid plaques, and neurofibrillary tangles formation in post-middle of human brain cells has developed new, widely accepting foundations on this association. In particular, HTN in elderly life mediates cerebral blood flow dysfunction, neuronal dysfunction, and significant decline in cognitive impairment, primarily in the late-life populace, governing the onset of AD. Thus, HTN is an established risk factor for AD. Considering the impact of AD, 1.89 million deaths annually, and the failure of palliative therapies to cure AD, the scientific research community is looking to adopt integrated approaches to target early modified risk factors like HTN to reduce AD burden. The current review highlights the significance and impact of HTN-based prevention in lowering the AD burden in the elderly by providing a comprehensive overview of the physiological relationship between AD and HTN with an in-detail explanation of the role and applications of pathological biomarkers in this clinical association. The review will gain worth in presenting new insights and providing inclusive discussion on the correlation between HTN and cognitive impairment. It will increase across a wider scientific audience to expand understanding of this pathophysiological association.

Relationship between glycemic control and cognitive impairment: A systematic review and meta-analysis

Background

Diabetes mellitus, or hyperglycemia, is an independent risk factor for cognitive impairment. Here we systematically analyzed whether glycemic control could improve cognitive impairment in patients with diabetes mellitus (DM), hyperglycemia, or insulin resistance.

Methods

Three databases (PubMed, EMBASE, and Cochrane Library) and ClinicalTrials.gov were searched for randomized controlled trials analyzing the relationship between glycemic control and cognitive function assessments, published from database inception to June 2022. Patients in experimental groups were treated with antidiabetic drugs, while control groups were treated with a placebo or alternative antidiabetic drugs. Data analysis was conducted using RevMan 5.3 and StataSE-64, and standardized mean difference (SMD) and 95% confidence intervals (CIs) were calculated.

Results

Thirteen studies comprising 19,314 participants were included. Analysis revealed that glycemic control significantly attenuated the degree of decline in cognitive function assessment scores (SMD  =  0.15; 95% CI 0.05, 0.26; p  <  0.00001), and funnel plots confirmed no publication bias. Seven studies used Mini-Mental State Examination as the primary cognitive function assessment, showing that glycemic control significantly delayed the degree of decline in cognitive function assessment scores (SMD  =  0.18; 95% CI 0.03, 0.34; p  =  0.02). Similar results were seen in two studies using the Montreal Cognitive Assessment scale, but without significant difference (SMD  =  0.05; 95% CI-0.10, 0.21; p  =  0.51). One study using Auditory Word Learning Test (AVLT) showed that glycemic control significantly delayed the decline in cognitive function assessment scores (SMD  =  0.52; 95% CI 0.11,0.93; p  =  0.01), and another used Wechsler Memory Scale Revised, showing similar results (SMD  =  1.45; 95% CI 0.86, 2.04; p  <  0.00001). Likewise, a study that used Modified Mini-Mental State scale showed that glycemic control significantly delayed the decline in cognitive function assessment scores (SMD  =  -0.10; 95% CI-0.16, -0.03; p  =  0.005). Lastly, one study used AVLT subtests to show that glycemic control delayed the decline in cognitive function assessment scores, although not statistically significant (SMD  =  0.09; 95% CI-0.53, 0.71; p  =  0.78).

Conclusion

Glycemic control through antidiabetic treatment correlates with the improvement of cognitive impairment in patients with DM, hyperglycemia or insulin resistance. However, further studies are needed to validate the results of this study.

Systematic Review Registration

PROSPERO, identifier CRD42022342260.

Association between Apolipoprotein E genotype and functional outcome in acute ischemic stroke

This study aims to determine whether APOE alleles would affect the functional outcome in acute ischemic stroke (AIS) and whether the relationship between inflammation and stroke-related disability varies according to APOE genotypes. We retrospectively collected the demographic and clinical data of AIS patients within one week of symptom-onset through medical records review. The primary outcome was dependence or death, defined as modified Rankin scale (mRS) score of 2-6, which was assessed at 3 months. Among 1929 enrolled patients, the prevalence of APOE ε4 carriers was 17.73% (342/1929). There were 394 AIS patients (394/1929, 20.43%) showed poor function outcome of 90-day mRS (2-6), of whom 147 (147/342, 42.98%) were APOE ε4 carriers and 247 (247/1587, 15.56%) were non-ε4 carriers. There was a significant increased probability of poor functional outcome after AIS among APOE ε4 carriers versus non-ε4 carriers (adjusted-OR 4.62, 95% CI 3.51 to 6.09, P < 0.001). Among ε4 carriers, high neutrophil-to-lymphocyte ratio (NLR) was significantly associated with stroke-related disability (Ptrend = 0.035); however, no significant association was observed among non-ε4 carriers. Our study showed that the APOE ε4 carriers had worse functional outcome after AIS as compared with non-ε4 carriers. APOE genotype may modify the relationship between NLR and 3-month stroke outcome.

The markers to delineate different phenotypes of macrophages related to metabolic disorders

Macrophages have a wide variety of roles in physiological and pathological conditions, making them promising diagnostic and therapeutic targets in diseases, especially metabolic disorders, which have attracted considerable attention in recent years. Owing to their heterogeneity and polarization, the phenotypes and functions of macrophages related to metabolic disorders are diverse and complicated. In the past three decades, the rapid progress of macrophage research has benefited from the emergence of specific molecular markers to delineate different phenotypes of macrophages and elucidate their role in metabolic disorders. In this review, we analyze the functions and applications of commonly used and novel markers of macrophages related to metabolic disorders, facilitating the better use of these macrophage markers in metabolic disorder research.

Association of ApoE gene polymorphisms with serum lipid levels and the risk of type 2 diabetes mellitus in the Chinese Han population of central China

Background

Apolipoprotein E (ApoE) is involved in lipid transformation and metabolism. Although some studies have examined the association between ApoE polymorphisms and the risk of type 2 diabetes mellitus (T2DM), the findings differ depending on the location and population.

Methods

A total of 1,738 participants, including 743 patients with T2DM and 995 controls without T2DM, were enrolled from central China, and ApoE polymorphisms, 388T > C (rs429358) and 526C > T (rs7412), were genotyped. The association between ApoE alleles and T2DM and blood lipid levels was analyzed. Logistic regression analysis was performed to evaluate the interactions between ApoE polymorphisms and various factors, such as age, sex, and prevalence of hypertension in patients with T2DM.

Results

The genotype ɛ3/ɛ4 and ɛ4 alleles of ApoE were associated with T2DM risk in the Chinese Han population in central China. Moreover, in patients with T2DM, participants in the E4 (ɛ3/ɛ4, ɛ4/ɛ4) group had significantly higher lipid profiles than those in the E3 (ɛ3/ɛ3) group, whereas participants in the E2 group (ɛ2/ɛ2, ɛ2/ɛ3) showed lower total cholesterol, low-density lipoprotein cholesterol, and ApoE-A1 levels than those in the E3 (ɛ3/ɛ3) group. The results from the current study may help in understanding ApoE polymorphisms and lipid profiles in the Chinese Han population.

Ischemia as a common trigger for Alzheimer’s disease

Alzheimer’s disease has various potential etiologies, all culminating in the accumulation of beta -amyloid derivatives and significant cognitive decline. Vascular-related pathology is one of the more frequent etiologies, especially in persons older than 65 years, as vascular risk factors are linked to both cerebrovascular disease and the development of AD. The vascular patho-mechanism includes atherosclerosis, large and small vessel arteriosclerosis, cortical and subcortical infarcts, white matter lesions, and microbleeds. These insults cause hypoperfusion, tissue ischemia, chronic inflammation, neuronal death, gliosis, cerebral atrophy, and accumulation of beta-amyloid and phosphorylated tau proteins. In preclinical studies, hyperbaric oxygen therapy has been shown to reverse brain ischemia, and thus alleviate inflammation, reverse the accumulation of beta-amyloid, induce regeneration of axonal white matter, stimulate axonal growth, promote blood–brain barrier integrity, reduce inflammatory reactions, and improve brain performance. In this perspective article we will summarize the patho-mechanisms induced by brain ischemia and their contribution to the development of AD. We will also review the potential role of interventions that aim to reverse brain ischemia, and discuss their relevance for clinical practice.

Targeting neuronal calcium channels and GSK3β for Alzheimer's disease with naturally-inspired Diels-Alder adducts

The complexity of neurodegenerative diseases, among which Alzheimer's disease plays a pivotal role, poses one of the tough therapeutic challenges of present time. In this perspective, a multitarget approach appears as a promising strategy to simultaneously interfere with different defective pathways. In this paper, a structural simplification plan was performed on our previously reported multipotent polycyclic compounds, in order to obtain a simpler pharmacophoric central core with improved pharmacokinetic properties, while maintaining the modulating activity on neuronal calcium channels and glycogen synthase kinase 3-beta (GSK-3β), as validated targets to combat Alzheimer's disease. The molecular pruning approach applied here led to tetrahydroisoindole-dione (1), tetrahydromethanoisoindole-dione (2) and tetrahydroepoxyisoindole-dione (3) structures, easily affordable by Diels-Alder cycloaddition. Preliminary data indicated structure 3 as the most appropriate, thus a SAR study was performed by introducing different substituents, selected on the basis of the commercial availability of the furan derivatives required for the synthetic procedure. The results indicated compound 10 as a promising, structurally atypical, safe and BBB-penetrating Ca_v modulator, inhibiting both L- and N-calcium channels, likely responsible for the Ca²⁺ overload observed in Alzheimer's disease. In a multitarget perspective, compound 11 appeared as an effective prototype, endowed with improved Ca_v inhibitory activity, with respect to the reference drug nifedipine, and encouraging modulating activity on GSK-3β.

The Relationship Between Cardiovascular Disease Risk Score and Postoperative Delirium: The PNDABLE Study

Objective

We aimed to investigate the relationship between Framingham Heart Study general cardiovascular disease risk score (FHS–CVD risk score) and postoperative delirium (POD) among patients who had unilateral total knee arthroplasty performed under epidural anesthesia. Furthermore, we examined whether such a hypothesized relationship was mediated by the cerebrospinal fluid (CSF) biomarkers.

Methods

A total of 750 participants were included in the current study. And the data were drawn from the database obtained from the Perioperative Neurocognitive Disorder And Biomarker Lifestyle (PNDABLE) study. The preoperative cognitive function of participants was measured by using Mini-Mental State Examination (MMSE). The incidence of POD was assessed using the Confusion Assessment Method (CAM). The POD severity was measured using the Memorial Delirium Assessment Scale (MDAS). The POD CSF biomarkers included in the current study were: Aβ42, T-tau, P-tau, Aβ42/T-tau, and Aβ42/P-tau. The level of the CSF biomarkers was measured using the enzyme-linked immune-sorbent assay (ELISA) in the PNDABLE study. Linear regression analysis was performed to examine the relationship between the FHS–CVD risk score and the POD CSF biomarkers. Logistic regression was used to analyze the relationship between FHS–CVD risk score, POD CSF biomarkers, and POD incidence. The proposed mediating effect of CSF biomarkers was evaluated using Mediation Analysis with 10,000 bootstrapped iterations. The receiver operating characteristic (ROC) curve is chosen as the evaluation metric for assessing the efficacy of the FHS–CVD risk score in predicting POD.

Results

In the PNDABLE study, the overall incidence of POD was 22.9% with 37.2% in the higher vascular risk group and 7.9% in the lower vascular risk group. Multiple linear regression models showed that a higher preoperative FHS–CVD risk score was positively correlated with CSF T-tau (β = 0.218, P = 0.015) and P-tau level (β = 0.309, P &lt; 0.001) in the higher vascular risk group. After adjusting for age (40–90 years), gender, education, MMSE, smoking history, drinking history, hypertension, diabetes, and the presence of CHD (cardiovascular heart disease), the results of the logistic regression analysis demonstrated the effect of Aβ42 (OR = 0.994, 95% CI 0.992–0.996, P &lt; 0.001), Aβ42/T-tau (OR = 0.353, 95% CI 0.254–0.491, P &lt; 0.001), and Aβ42/P-tau (OR = 0.744, 95% CI 0.684–0.809, P &lt; 0.001) in protecting patients against POD. However, the FHS–CVD risk score (OR = 1.142, 95% CI 1.017–1.282, P = 0.025) and the remaining two biomarkers: T-tau (OR = 1.005, 95% CI 1.004–1.007, P &lt; 0.001) and P-tau (OR = 1.045, 95%CI 1.029–1.062, P &lt; 0.001) were identified as the risk factors. Mediation analyses revealed that the association between FHS–CVD risk score and POD was partially mediated by T-tau (proportion: 31.6%) and P-tau (proportion: 23.6%). The predictive power of the FHS–CVD risk score was validated by the ROC curve with an AUC of 0.7364.

Conclusion

Higher vascular risk score is one of the preoperative risk factors for POD, which is partly mediated by CSF biomarker tau protein.

Clinical Trial Registration

[www.clinicaltrials.gov], identifier [ChiCTR2000033439].

Synergic effect of metabolic syndrome and lipodystrophy on oxidative stress and inflammation process in treated HIV-patients

The aim of this study was to assess the effect of lipodystrophy (LD) associated to metabolic syndrome (MS) on oxidative stress and inflammation in a cohort of 243 HIV-infected patients with MS, all of them under three different antiretroviral regimens. We collected immunovirological, biochemical and metabolic data, as well as anthropometric measurements. In addition, cardiovascular risk was also assessed by means of Atherogenic Index of Plasma (API) and Framingham Risk Score. The MS-LD patient set was characterized by a lower initial lymphocyte CD4 count and CD4/CD8 ratio and a higher initial viral load than the group without LD. We also found worse lipidic and glycaemic profiles (with lower HDL-cholesterol and higher triglyceride and glucose levels) in the MS-LD group. BMI, systolic blood pressure and Framingham score were significantly increased compared to MS-Non LD. In addition, patients with MS and LD had significantly higher levels of carbonylated proteins, lipid peroxidation, IL-6 and IL-8, as well as a significant decrease in the levels of leptin, adiponectin and antioxidant activities of catalase, super oxide dismutase and glutathione associated enzymes. In MS-LD HIV-1 patients, a significant negative correlation was found between Framingham Risk Score and the antioxidant biomarkers, however a positive association was found between API and protein-C reactive and carbonylated proteins. Segregating by ART, the above-mentioned conditions were worse within the MS-LD group whose treatment contained protease inhibitors, such as lopinavir. In conclusion, HIV-1 infected patients treated for at least six months, especially with regimens including PIs, showed a worsening of inflammatory process and oxidative stress.

Keap1 as Target of Genistein on Nrf2 Signaling Pathway Antagonizing Aβ induced Oxidative Damage of Cerebrovascular Endothelial Cells

BACKGROUND

β-amyloid peptides (Aβ) induced oxidative damage contributes to the pathogenesis of neurodegenerative diseases and cerebrovascular system is more vulnerable to oxidative stress. Our earlier study showed a clue that Genistein (Gen) might activate Nf-E2 related factor 2 (Nrf2) pathway to protect cerebrovascular cells from oxidative damage induced by Aβ, but the specific mechanisms and regulation targets are unclear.

OBJECTIVE

In this study, the anti-oxidative effects and the possible targets of Gen on regulating Nrf2 pathway in bEnd.3 cells were investigated. Cells were divided into control, Aβ25-35, Gen and Gen+Aβ25-35 groups.

METHODS

Cell viability, levels of malondialdehyde (MDA), Superoxide Dismutase (SOD) activity and nitrotyrosine were evaluated. Moreover, mRNA and/or protein expressions of Nrf2 and kelch-like ECH-associated protein 1 (Keap1) were measured. Then we transfected Keap1 over-expressed plasmid into bEnd.3 cells and measured the protein expressions of Nrf2 pathway related factors. Data showed that Gen could inhibit the over-production of MDA and nitrotyrosine and activate SOD activity. Besides we got the phenomenon that Gen could up-regulate the mRNA and protein expressions of Nrf2 and down-regulate Keap1 protein expression, the Keap1 over-expressed plasmid study indicated that the up-regulation of Nrf2 protein expression induced by pretreatment of Gen could be blocked by the transfection of Keap1 over-expressed plasmid, and the same results also occurred in Nrf2 downstream factors.

CONCLUSION

Gen could alleviate the cerebrovascular cells oxidative damage induced by Aβ25-35 through regulating Nrf2 pathway, and Keap1 might be one of the targets of Gen on activating Nrf2 pathway.

Alzheimer’s Disease: An Update and Insights Into Pathophysiology

Alzheimer’s disease (AD) is an irreversible brain disorder associated with slow, progressive loss of brain functions mostly in older people. The disease processes start years before the symptoms are manifested at which point most therapies may not be as effective. In the hippocampus, the key proteins involved in the JAK2/STAT3 signaling pathway, such as p-JAK2-Tyr1007 and p-STAT3-Tyr705 were found to be elevated in various models of AD. In addition to neurons, glial cells such as astrocytes also play a crucial role in the progression of AD. Without having a significant effect on tau and amyloid pathologies, the JAK2/STAT3 pathway in reactive astrocytes exhibits a behavioral impact in the experimental models of AD. Cholinergic atrophy in AD has been traced to a trophic failure in the NGF metabolic pathway, which is essential for the survival and maintenance of basal forebrain cholinergic neurons (BFCN). In AD, there is an alteration in the conversion of the proNGF to mature NGF (mNGF), in addition to an increase in degradation of the biologically active mNGF. Thus, the application of exogenous mNGF in experimental studies was shown to improve the recovery of atrophic BFCN. Furthermore, it is now coming to light that the FGF7/FGFR2/PI3K/Akt signaling pathway mediated by microRNA-107 is also involved in AD pathogenesis. Vascular dysfunction has long been associated with cognitive decline and increased risk of AD. Vascular risk factors are associated with higher tau and cerebral beta-amyloid (Aβ) burden, while synergistically acting with Aβ to induce cognitive decline. The apolipoprotein E4 polymorphism is not just one of the vascular risk factors, but also the most prevalent genetic risk factor of AD. More recently, the research focus on AD shifted toward metabolisms of various neurotransmitters, major and minor nutrients, thus giving rise to metabolomics, the most important “omics” tool for the diagnosis and prognosis of neurodegenerative diseases based on an individual’s metabolome. This review will therefore proffer a better understanding of novel signaling pathways associated with neural and glial mechanisms involved in AD, elaborate potential links between vascular dysfunction and AD, and recent developments in “omics”-based biomarkers in AD.

Addressing Blood–Brain Barrier Impairment in Alzheimer’s Disease

The blood–brain barrier (BBB) plays a vital role in maintaining the specialized microenvironment of the brain tissue. It facilitates communication while separating the peripheral circulation system from the brain parenchyma. However, normal aging and neurodegenerative diseases can alter and damage the physiological properties of the BBB. In this review, we first briefly present the essential pathways maintaining and regulating BBB integrity, and further review the mechanisms of BBB breakdown associated with normal aging and peripheral inflammation-causing neurodegeneration and cognitive impairments. We also discuss how BBB disruption can cause or contribute to Alzheimer’s disease (AD), the most common form of dementia and a devastating neurological disorder. Next, we document overlaps between AD and vascular dementia (VaD) and briefly sum up the techniques for identifying biomarkers linked to BBB deterioration. Finally, we conclude that BBB breakdown could be used as a biomarker to help diagnose cognitive impairment associated with normal aging and neurodegenerative diseases such as AD.

Sex and APOE ε4 modify the effect of cardiovascular risk on tau in cognitively normal older adults

The interaction between APOE ε4 and vascular risk factors on cognitive function is stronger in women than in men. These effects may be mediated by the amount of tau pathology in the brain. Therefore, we examined whether APOE ε4 and sex modify cross-sectional associations between cardiovascular risk and tau deposition in cognitively normal older adults from the Alzheimer’s Disease Neuroimaging Initiative. We calculated the Framingham Heart Study cardiovascular disease risk score for 141 participants (74 women, 47 APOE ε4 carriers) with complete medical history data, processed tau PET data and a Clinical Dementia Rating global score of 0.0 at the time of the tau PET scan, implying no significant cognitive or functional impairment. We used linear regression models to examine the effects of sex, APOE ε4, cardiovascular risk and their interactions on tau deposition in the entorhinal cortex, inferior temporal cortex and a composite meta-region of interest of temporal lobe areas. We found a significant three-way interaction among sex, APOE ε4 status, and cardiovascular disease risk on tau deposition in the entorhinal cortex (β = 0.04; 95% CI, 0.01 to 0.07; P =0.008), inferior temporal cortex (β = 0.02; 95% CI, 0.0 to 0.05; P =0.029) and meta-region (β = 0.02; 95% CI, 0.0–0.04; P = 0.042). After stratifying by APOE ε4 status to examine interactions between sex and cardiovascular disease risk on tau in APOE ε4 carriers and non-carriers, we found a significant two-way interaction between sex and cardiovascular disease risk on tau in the entorhinal cortex (β = 0.05; 95% CI, 0.02 to 0.08; P =0.001), inferior temporal cortex (β = 0.03; 95% CI, 0.01 to 0.05; P =0.009) and meta-region (β = 0.02; 95% CI, 0.01 to 0.04; P =0.008) only among APOE ε4 carriers. In analyses stratified by sex, higher cardiovascular risk scores were associated with higher levels of tau in the entorhinal cortex (β = 0.05; 95% CI, 0.02 to 0.08; P =0.002), inferior temporal cortex (β = 0.02; 95% CI, 0.0 to 0.05; P =0.023) and meta-region (β = 0.02; 95% CI, 0.01 to 0.04; P =0.013) in female APOE ε4 carriers but not in male carriers. Our findings suggest that cognitively normal older women carrying at least one APOE ε4 allele, may be particularly vulnerable to the effects of cardiovascular disease risk on early tau deposition.

Retinal Venular Tortuosity Jointly with Retinal Amyloid Burden Correlates with Verbal Memory Loss: A Pilot Study

Introduction: Retinal imaging is a non-invasive tool to study both retinal vasculature and neurodegeneration. In this exploratory retinal curcumin-fluorescence imaging (RFI) study, we sought to determine whether retinal vascular features combined with retinal amyloid burden correlate with the neurocognitive status. Methods: We used quantitative RFI in a cohort of patients with cognitive impairment to automatically compute retinal amyloid burden. Retinal blood vessels were segmented, and the vessel tortuosity index (VTI), inflection index, and branching angle were quantified. We assessed the correlations between retinal vascular and amyloid parameters, and cognitive domain Z-scores using linear regression models. Results: Thirty-four subjects were enrolled and twenty-nine (55% female, mean age 64 ± 6 years) were included in the combined retinal amyloid and vascular analysis. Eleven subjects had normal cognition and 18 had impaired cognition. Retinal VTI was discriminated among cognitive scores. The combined proximal mid-periphery amyloid count and venous VTI index exhibited significant differences between cognitively impaired and cognitively normal subjects (0.49 ± 1.1 vs. 0.91 ± 1.4, p = 0.006), and correlated with both the Wechsler Memory Scale-IV and SF-36 mental component score Z-scores (p < 0.05). Conclusion: This pilot study showed that retinal venular VTI combined with the proximal mid-periphery amyloid count could predict verbal memory loss. Future research is needed to finesse the clinical application of this retinal imaging-based technology.

Associations of Vascular Risk with Cognition, Brain Glucose Metabolism, and Clinical Progression in Cognitively Intact Elders

BACKGROUND

Increasing evidence supports an important role of vascular risk in cognitive decline and dementia.

OBJECTIVE

This study aimed to examine whether vascular risk was associated with cognitive decline, cerebral hypometabolism, and clinical progression in cognitively intact elders.

METHODS

Vascular risk was assessed by the Framingham Heart Study general Cardiovascular disease (FHS-CVD) risk score. The cross-sectional and longitudinal associations of FHS-CVD risk score with cognition and brain glucose metabolism were explored using multivariate linear regression and linear mixed effects models, respectively. The risk of clinical progression conversion was assessed using Kaplan-Meier survival curves and multivariate Cox proportional hazard models.

RESULTS

A total of 491 cognitively intact elders were included from Alzheimer's Disease Neuroimaging Initiative (ADNI) database. Participants with high FHS-CVD risk scores had lower baseline Mini-Mental State Examination (MMSE) (p = 0.009), executive function (EF) (p < 0.001), memory function (MEM) (p < 0.001) scores, and F18-fluorodeoxyglucose positron emission tomography (FDG-PET) uptake (p < 0.001) than those with low FHS-CVD risk scores. In longitudinal analyses, individuals with higher FHS-CVD risk scores had greater longitudinal declines in MMSE (p = 0.043), EF (p = 0.029) scores, and FDG-PET uptake (p = 0.035). Besides, individuals with a higher vascular risk had an increased risk of clinical progression (p = 0.004).

CONCLUSION

These findings indicated effects of vascular risk on cognitive decline, cerebral hypometabolism, and clinical progression. Early detection and management of vascular risk factors might be useful in the prevention of dementia.

Western diet as a trigger of Alzheimer's disease: From metabolic syndrome and systemic inflammation to neuroinflammation and neurodegeneration

An excess of saturated fatty acids and simple sugars in the diet is a known environmental risk factor of Alzheimer's disease (AD) but the holistic view of the interacting processes through which such diet may contribute to AD pathogenesis is missing. We addressed this need through extensive analysis of published studies investigating the effects of western diet (WD) on AD development in humans and laboratory animals. We reviewed WD-induced systemic alterations comprising metabolic changes, induction of obesity and adipose tissue inflammation, gut microbiota dysbiosis and acceleration of systemic low-grade inflammation. Next we provide an overview of the evidence demonstrating that WD-associated systemic alterations drive impairment of the blood-brain barrier (BBB) and development of neuroinflammation paralleled by accumulation of toxic amyloid. Later these changes are followed by dysfunction of synaptic transmission, neurodegeneration and finally memory and cognitive impairment. We conclude that WD can trigger AD by acceleration of inflammaging, and that BBB impairment induced by metabolic and systemic inflammation play the central role in this process. Moreover, the concurrence of neuroinflammation and Aβ dyshomeostasis, which by reciprocal interactions drive the vicious cycle of neurodegeneration, contradicts Aβ as the primary trigger of AD. Given that in 2019 the World Health Organization recommended focusing on modifiable risk factors in AD prevention, this overview of the sequential, complex pathomechanisms initiated by WD, which can lead from peripheral disturbances to neurodegeneration, can support future prevention strategies.

Diabetes and Alzheimer's Disease: Might Mitochondrial Dysfunction Help Deciphering the Common Path?

A growing number of clinical and epidemiological studies support the hypothesis of a tight correlation between type 2 diabetes mellitus (T2DM) and the development risk of Alzheimer's disease (AD). Indeed, the proposed definition of Alzheimer's disease as type 3 diabetes (T3D) underlines the key role played by deranged insulin signaling to accumulation of aggregated amyloid beta (Aβ) peptides in the senile plaques of the brain. Metabolic disturbances such as hyperglycemia, peripheral hyperinsulinemia, dysregulated lipid metabolism, and chronic inflammation associated with T2DM are responsible for an inefficient transport of insulin to the brain, producing a neuronal insulin resistance that triggers an enhanced production and deposition of Aβ and concomitantly contributes to impairment in the micro-tubule-associated protein Tau, leading to neural degeneration and cognitive decline. Furthermore, the reduced antioxidant capacity observed in T2DM patients, together with the impairment of cerebral glucose metabolism and the decreased performance of mitochondrial activity, suggests the existence of a relationship between oxidative damage, mitochondrial impairment, and cognitive dysfunction that could further reinforce the common pathophysiology of T2DM and AD. In this review, we discuss the molecular mechanisms by which insulin-signaling dysregulation in T2DM can contribute to the pathogenesis and progression of AD, deepening the analysis of complex mechanisms involved in reactive oxygen species (ROS) production under oxidative stress and their possible influence in AD and T2DM. In addition, the role of current therapies as tools for prevention or treatment of damage induced by oxidative stress in T2DM and AD will be debated.

Relationship Between Amyloid-β Deposition and Blood-Brain Barrier Dysfunction in Alzheimer's Disease

Amyloid-β (Aβ) is the predominant pathologic protein in Alzheimer's disease (AD). The production and deposition of Aβ are important factors affecting AD progression and prognosis. The deposition of neurotoxic Aβ contributes to damage of the blood-brain barrier. However, the BBB is also crucial in maintaining the normal metabolism of Aβ, and dysfunction of the BBB aggravates Aβ deposition. This review characterizes Aβ deposition and BBB damage in AD, summarizes their interactions, and details their respective mechanisms.

Role of Neuron and Glia in Alzheimer's Disease and Associated Vascular Dysfunction

Amyloidogenicity and vascular dysfunction are the key players in the pathogenesis of Alzheimer’s disease (AD), involving dysregulated cellular interactions. An intricate balance between neurons, astrocytes, microglia, oligodendrocytes and vascular cells sustains the normal neuronal circuits. Conversely, cerebrovascular diseases overlap neuropathologically with AD, and glial dyshomeostasis promotes AD-associated neurodegenerative cascade. While pathological hallmarks of AD primarily include amyloid-β (Aβ) plaques and neurofibrillary tangles, microvascular disorders, altered cerebral blood flow (CBF), and blood-brain barrier (BBB) permeability induce neuronal loss and synaptic atrophy. Accordingly, microglia-mediated inflammation and astrogliosis disrupt the homeostasis of the neuro-vascular unit and stimulate infiltration of circulating leukocytes into the brain. Large-scale genetic and epidemiological studies demonstrate a critical role of cellular crosstalk for altered immune response, metabolism, and vasculature in AD. The glia associated genetic risk factors include APOE, TREM2, CD33, PGRN, CR1, and NLRP3, which correlate with the deposition and altered phagocytosis of Aβ. Moreover, aging-dependent downregulation of astrocyte and microglial Aβ-degrading enzymes limits the neurotrophic and neurogenic role of glial cells and inhibits lysosomal degradation and clearance of Aβ. Microglial cells secrete IGF-1, and neurons show a reduced responsiveness to the neurotrophic IGF-1R/IRS-2/PI3K signaling pathway, generating amyloidogenic and vascular dyshomeostasis in AD. Glial signals connect to neural stem cells, and a shift in glial phenotype over the AD trajectory even affects adult neurogenesis and the neurovascular niche. Overall, the current review informs about the interaction of neuronal and glial cell types in AD pathogenesis and its critical association with cerebrovascular dysfunction.

Biphasic Effects of Ethanol Exposure on Waste Metabolites Clearance in the CNS

We have shown that the effects of low-dose ethanol promote the clearance of waste metabolites, such as amyloid-beta (Aβ) proteins, from the brain through the perivascular space (PVS). We demonstrated that dilative reactivity of arterial smooth muscle and endothelial cells regulate this clearance. These findings indicate the importance of blood-brain barrier (BBB) transvascular clearance of large size metabolites from the central nervous system (CNS), where the lymphatic clearance system is absent. We next examined the contrasting effects of acute low-dose and chronic moderate ethanol exposure on BBB-associated perivascular clearance. We injected a high molecular weight fluorescent dye into the interstitial space or directly into the cerebrospinal fluid (CSF). Bio-distribution of this tracer was then examined in different brain regions by multiphoton imaging and whole brain tissue section scanning. Ethanol-induced molecular/cellular mechanisms that drive the increase or decrease in movement of the fluorescent tracer were correlated to BBB integrity and arterial vessel reactivity. We found that activation of endothelial nitric oxide synthase (eNOS) under low-dose ethanol conditions with a shift to activation of inducible NOS (iNOS) under chronic high ethanol exposure conditions, which appeared to regulate these contrasting effects. We validated these observations by qualitative and quantitative investigation of eNOS, iNOS, BBB integrity, and perivascular clearance of waste metabolites. We concluded that the effects of low-dose ethanol increased the diffusive movement of waste metabolites via eNOS-derived NO, which increased the arterial endothelial-smooth muscle cell dilative reactivity without affecting BBB integrity, whereas a prolonged induction of iNOS under chronic ethanol exposure conditions caused oxidative damage of the arterial endothelial-smooth muscle layers resulting in cerebral amyloid-like angiopathy. This led to dysfunction of the BBB, dilative reactivity, and impaired waste metabolites movement from the interstitial space or subarachnoid space (SAS) through perivascular clearance.

Synergic effect of metabolic syndrome and lipodystrophy on oxidative stress and inflammation process in treated HIV-patients

The aim of this study was to assess the effect of lipodystrophy (LD) associated to metabolic syndrome (MS) on oxidative stress and inflammation in a cohort of 243 HIV-infected patients with MS, all of them under three different antiretroviral regimens. We collected immunovirological, biochemical and metabolic data, as well as anthropometric measurements. In addition, cardiovascular risk was also assessed by means of Atherogenic Index of Plasma (API) and Framingham Risk Score. The MS-LD patient set was characterized by a lower initial lymphocyte CD4 count and CD4/CD8 ratio and a higher initial viral load than the group without LD. We also found worse lipidic and glycaemic profiles (with lower HDL-cholesterol and higher triglyceride and glucose levels) in the MS-LD group. BMI, systolic blood pressure and Framingham score were significantly increased compared to MS-Non LD. In addition, patients with MS and LD had significantly higher levels of carbonylated proteins, lipid peroxidation, IL-6 and IL-8, as well as a significant decrease in the levels of leptin, adiponectin and antioxidant activities of catalase, super oxide dismutase and glutathione associated enzymes. In MS-LD HIV-1 patients, a significant negative correlation was found between Framingham Risk Score and the antioxidant biomarkers, however a positive association was found between API and protein-C reactive and carbonylated proteins. Segregating by ART, the above-mentioned conditions were worse within the MS-LD group whose treatment contained protease inhibitors, such as lopinavir. In conclusion, HIV-1 infected patients treated for at least six months, especially with regimens including PIs, showed a worsening of inflammatory process and oxidative stress.

Exposure to Traffic-Generated Pollutants Exacerbates the Expression of Factors Associated with the Pathophysiology of Alzheimer’s Disease in Aged C57BL/6 Wild-Type Mice

Background: Multiple studies report a strong correlation between traffic-generated air pollution-exposure and detrimental outcomes in the central nervous system (CNS), including Alzheimer’s disease (AD). Incidence of AD is rapidly increasing and, worldwide, many live in regions where pollutants exceed regulatory standards. Thus, it is imperative to identify environmental pollutants that contribute to AD, and the mechanisms involved. Objective: We investigated the effects of mixed gasoline and diesel engine emissions (MVE) on the expression of factors involved in progression of AD in the hippocampus and cerebrum in a young versus aged mouse model. Methods: Young (2 months old) and aged (18 months old) male C57BL/6 mice were exposed to either MVE (300μg/m3 PM) or filtered air (FA) for 6 h/d, 7 d/wk, for 50 d. Immunofluorescence and RT-qPCR were used to quantify oxidative stress (8-OHdG) and expression of amyloid-β protein precursor (AβPP), β secretase (BACE1), amyloid-β (Aβ), aryl hydrocarbon receptor (AhR), cytochrome P450 (CYP) 1B1, angiotensin-converting enzyme (ACE1), and angiotensin II type 1 (AT1) receptor in the cerebrum and hippocampus, in addition to cerebral microvascular tight junction (TJ) protein expression. Results: We observed age-related increases in oxidative stress, AhR, CYP1B1, Aβ, BACE1, and AT1 receptor in the CA1 region of the hippocampus, and elevation of cerebral AβPP, AhR, and CYP1B1 mRNA, associated with decreased cerebral microvascular TJ protein claudin-5. MVE-exposure resulted in further promotion of oxidative stress, and significant increases in AhR, CYP1B1, BACE1, ACE1, and Aβ, compared to the young and aged FA-exposed mice. Conclusion: Such findings suggest that MVE-exposure exacerbates the expression of factors in the CNS associated with AD pathogenesis in aged populations.

Retinal biomarkers for Alzheimer's disease and vascular cognitive impairment and dementia (VCID): implication for early diagnosis and prognosis

Cognitive impairment and dementia are major medical, social, and economic public health issues worldwide with significant implications for life quality in older adults. The leading causes are Alzheimer's disease (AD) and vascular cognitive impairment/dementia (VCID). In both conditions, pathological alterations of the cerebral microcirculation play a critical pathogenic role. Currently, the main pathological biomarkers of AD-β-amyloid peptide and hyperphosphorylated tau proteins-are detected either through cerebrospinal fluid (CSF) or PET examination. Nevertheless, given that they are invasive and expensive procedures, their availability is limited. Being part of the central nervous system, the retina offers a unique and easy method to study both neurodegenerative disorders and cerebral small vessel diseases in vivo. Over the past few decades, a number of novel approaches in retinal imaging have been developed that may allow physicians and researchers to gain insights into the genesis and progression of cerebromicrovascular pathologies. Optical coherence tomography (OCT), OCT angiography, fundus photography, and dynamic vessel analyzer (DVA) are new imaging methods providing quantitative assessment of retinal structural and vascular indicators-such as thickness of the inner retinal layers, retinal vessel density, foveal avascular zone area, tortuosity and fractal dimension of retinal vessels, and microvascular dysfunction-for cognitive impairment and dementia. Should further studies need to be conducted, these retinal alterations may prove to be useful biomarkers for screening and monitoring dementia progression in clinical routine. In this review, we seek to highlight recent findings and current knowledge regarding the application of retinal biomarkers in dementia assessment.

A Chronological Review of Potential Disease-Modifying Therapeutic Strategies for Alzheimer's Disease

Late-onset Alzheimer's disease (LOAD) is a neurodegenerative disorder that has become a worldwide health problem. This pathology has been classically characterized for its affectation on cognitive function and the presence of depositions of extracellular amyloid β-protein (Aβ) and intracellular neurofibrillary tangles (NFT) composed of hyperphosphorylated Tau protein. To this day, no effective treatment has been developed. Multiple strategies have been proposed over the years with the aim of finding new therapeutic approaches, such as the sequestration of Aβ in plasma or the administration of anti-inflammatory drugs. Also, given the significant role of the insulin receptor in the brain in the proper maintenance of cognitive function, drugs focused on the amelioration of insulin resistance have been proposed as potentially useful and effective in the treatment of AD. In the present review, taking into account the molecular complexity of the disease, it has been proposed that the most appropriate therapeutic strategy is a combinatory treatment of several drugs that will regulate a wide spectrum of the described altered pathological pathways.

Acute Traumatic Brain Injury-Induced Neuroinflammatory Response and Neurovascular Disorders in the Brain

Acute traumatic brain injury (TBI) leads to neuroinflammation, neurodegeneration, cognitive decline, psychological disorders, increased blood-brain barrier (BBB) permeability, and microvascular damage in the brain. Inflammatory mediators secreted from activated glial cells, neurons, and mast cells are implicated in the pathogenesis of TBI through secondary brain damage. Abnormalities or damage to the neurovascular unit is the indication of secondary injuries in the brain after TBI. However, the precise mechanisms of molecular and ultrastructural neurovascular alterations involved in the pathogenesis of acute TBI are not yet clearly understood. Moreover, currently, there are no precision-targeted effective treatment options to prevent the sequelae of TBI. In this study, mice were subjected to closed head weight-drop-induced acute TBI and evaluated neuroinflammatory and neurovascular alterations in the brain by immunofluorescence staining or quantitation by enzyme-linked immunosorbent assay (ELISA) procedure. Mast cell stabilizer drug cromolyn was administered to inhibit the neuroinflammatory response of TBI. Results indicate decreased level of pericyte marker platelet-derived growth factor receptor-beta (PDGFR-β) and BBB-associated tight junction proteins junctional adhesion molecule-A (JAM-A) and zonula occludens-1 (ZO-1) in the brains 7 days after weight-drop-induced acute TBI as compared with the brains from sham control mice indicating acute TBI-associated BBB/tight junction protein disruption. Further, the administration of cromolyn drug significantly inhibited acute TBI-associated decrease of PDGFR-β, JAM-A, and ZO-1 in the brain. These findings suggest that acute TBI causes BBB/tight junction damage and that cromolyn administration could protect this acute TBI-induced brain damage as well as its long-time consequences.

Central nervous system diseases associated with blood brain barrier breakdown - A Comprehensive update of existing literatures

Blood vessels that supply and feed the central nervous system (CNS) possess unique and exclusive properties, named as blood–brain barrier (BBB). It is responsible for tight regulation of the movement of ions, molecules, and cells between the blood and the brain thereby maintaining controlled chemical composition of the neuronal milieu required for appropriate functioning. It also protects the neural tissue from toxic plasma components, blood cells and pathogens from entering the brain. In this review the importance of BBB and its disruption causing brain pathology and progression to different neurological diseases like Alzheimer’s disease (AD), Parkinson’s disease (PD), Amyotrophic lateral sclerosis (ALS), Huntington’s disease (HD) etc. will be discussed.

Common Protective Strategies in Neurodegenerative Disease: Focusing on Risk Factors to Target the Cellular Redox System

Neurodegenerative disease is an umbrella term for different conditions which primarily affect the neurons in the human brain. In the last century, significant research has been focused on mechanisms and risk factors relevant to the multifaceted etiopathogenesis of neurodegenerative diseases. Currently, neurodegenerative diseases are incurable, and the treatments available only control the symptoms or delay the progression of the disease. This review is aimed at characterizing the complex network of molecular mechanisms underpinning acute and chronic neurodegeneration, focusing on the disturbance in redox homeostasis, as a common mechanism behind five pivotal risk factors: aging, oxidative stress, inflammation, glycation, and vascular injury. Considering the complex multifactorial nature of neurodegenerative diseases, a preventive strategy able to simultaneously target multiple risk factors and disease mechanisms at an early stage is most likely to be effective to slow/halt the progression of neurodegenerative diseases.