Update on the Neurobiology of Vascular Cognitive Impairment: From Lab to Clinic

Past, Present, and Future of Non-invasive Brain Stimulation Approaches to Treat Cognitive Impairment in Neurodegenerative Diseases: Time for a Comprehensive Critical Review

Low birth rates and increasing life expectancy experienced by developed societies have placed an unprecedented pressure on governments and the health system to deal effectively with the human, social and financial burden associated to aging-related diseases. At present, ∼24 million people worldwide suffer from cognitive neurodegenerative diseases, a prevalence that doubles every five years. Pharmacological therapies and cognitive training/rehabilitation have generated temporary hope and, occasionally, proof of mild relief. Nonetheless, these approaches are yet to demonstrate a meaningful therapeutic impact and changes in prognosis. We here review evidence gathered for nearly a decade on non-invasive brain stimulation (NIBS), a less known therapeutic strategy aiming to limit cognitive decline associated with neurodegenerative conditions. Transcranial Magnetic Stimulation and Transcranial Direct Current Stimulation, two of the most popular NIBS technologies, use electrical fields generated non-invasively in the brain to long-lastingly enhance the excitability/activity of key brain regions contributing to relevant cognitive processes. The current comprehensive critical review presents proof-of-concept evidence and meaningful cognitive outcomes of NIBS in eight of the most prevalent neurodegenerative pathologies affecting cognition: Alzheimer's Disease, Parkinson's Disease, Dementia with Lewy Bodies, Primary Progressive Aphasias (PPA), behavioral variant of Frontotemporal Dementia, Corticobasal Syndrome, Progressive Supranuclear Palsy, and Posterior Cortical Atrophy. We analyzed a total of 70 internationally published studies: 33 focusing on Alzheimer's disease, 19 on PPA and 18 on the remaining neurodegenerative pathologies. The therapeutic benefit and clinical significance of NIBS remains inconclusive, in particular given the lack of a sufficient number of double-blind placebo-controlled randomized clinical trials using multiday stimulation regimes, the heterogeneity of the protocols, and adequate behavioral and neuroimaging response biomarkers, able to show lasting effects and an impact on prognosis. The field remains promising but, to make further progress, research efforts need to take in account the latest evidence of the anatomical and neurophysiological features underlying cognitive deficits in these patient populations. Moreover, as the development of in vivo biomarkers are ongoing, allowing for an early diagnosis of these neuro-cognitive conditions, one could consider a scenario in which NIBS treatment will be personalized and made part of a cognitive rehabilitation program, or useful as a potential adjunct to drug therapies since the earliest stages of suh diseases. Research should also integrate novel knowledge on the mechanisms and constraints guiding the impact of electrical and magnetic fields on cerebral tissues and brain activity, and incorporate the principles of information-based neurostimulation.

Preserved central cholinergic functioning to transcranial magnetic stimulation in de novo patients with celiac disease

BACKGROUND

Celiac disease (CD) is now viewed as a systemic disease with multifaceted clinical manifestations. Among the extra-intestinal features, neurological and neuropsychiatric symptoms are still a diagnostic challenge, since they can precede or follow the diagnosis of CD. In particular, it is well known that some adults with CD may complain of cognitive symptoms, that improve when the gluten-free diet (GFD) is started, although they may re-appear after incidental gluten intake. Among the neurophysiological techniques, motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) can non-invasively probe in vivo the excitation state of cortical areas and cortico-spinal conductivity, being also able to unveil preclinical impairment in several neurological and psychiatric disorders, as well as in some systemic diseases affecting the central nervous system (CNS), such as CD. We previously demonstrated an intracortical disinhibition and hyperfacilitation of MEP responses to TMS in newly diagnosed patients. However, no data are available on the central cholinergic functioning indexed by specific TMS measures, such as the short-latency afferent inhibition (SAI), which might represent the neurophysiological correlate of cognitive changes in CD patients, also at the preclinical level.

METHODS

Cognitive and depressive symptoms were screened by means of the Montreal Cognitive Assessment (MoCA) and the 17-item Hamilton Depression Rating Scale (HDRS), respectively, in 15 consecutive de novo CD patients and 15 healthy controls. All patients were on normal diet at the time of the enrolment. Brain computed tomography (CT) was performed in all patients. SAI, recorded at two interstimulus intervals (2 and 8 ms), was assessed as the percentage amplitude ratio between the conditioned and the unconditioned MEP response. Resting motor threshold, MEP amplitude and latency, and central motor conduction time were also measured.

RESULTS

The two groups were comparable for age, sex, anthropometric features, and educational level. Brain CT ruled out intracranial calcifications and clear radiological abnormalities in all patients. Scores at MoCA and HDRS were significantly worse in patients than in controls. The comparison of TMS data between the two groups revealed no statistically significant difference for all measures, including SAI at both interstimulus intervals.

CONCLUSIONS

Central cholinergic functioning explored by the SAI of the motor cortex resulted to be not affected in these de novo CD patients compared to age-matched healthy controls. Although the statistically significant difference in MoCA, an overt cognitive impairment was not clinically evident in CD patients. Coherently, to date, no study based on TMS or other diagnostic techniques has shown any involvement of the central acetylcholine or the cholinergic fibers within the CNS in CD. This finding might add support to the vascular inflammation hypothesis underlying the so-called "gluten encephalopathy", which seems to be due to an aetiology different from that of the cholinergic dysfunction. Longitudinal studies correlating clinical, TMS, and neuroimaging data, both before and after GFD, are needed.

Fluoxetine May Enhance VEGF, BDNF and Cognition in Patients with Vascular Cognitive Impairment No Dementia: An Open-Label Randomized Clinical Study

PURPOSE

Selective serotonin reuptake inhibitors (SSRIs) enhance angiogenesis and neurogenesis. Brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) play an important role in neurogenesis and angiogenesis. However, the effect of SSRIs on cognition and serum BDNF and VEGF in patients with vascular cognitive impairment no dementia (VCIND) is largely unknown.

PATIENTS AND METHODS

It was an open label study. Fifty VCIND patients were randomly allocated to receive fluoxetine (20 mg/d; n = 25) or no fluoxetine (control group; n = 25) for 12 weeks. VCIND patients received fluoxetine 20 mg/d and secondary prevention of stroke for 12 weeks in the fluoxetine group, whereas the control group received only secondary prevention of stroke for 12 weeks. The primary outcome and secondary outcome were of assessment of Alzheimer's Disease Assessment Scale cognitive subscale (ADAS-cog) score, Ten Point Clock drawing test score (TPC), Verbal Fluency Test (VFT), Trail Making Test form a (TMTa), Trail Making Test form b (TMTb) and Digit Span Test score at baseline and week 12 in the both groups. And serum concentration of BDNF and VEGF was also tested at baseline and week 12 in both groups.

RESULTS

After 12 weeks, TPC scores increased more significantly in the fluoxetine group than in the control group, while TMTa score and TMTb score were decreased more significantly in the fluoxetine group than in the control group. We also found that the serum concentration of BDNF and VEGF in the fluoxetine group increased more significantly than in the control group. However, we found no significant differences in mean change from baseline between fluoxetine and control group in ADAS-Cog score, Digit Span Test score and VFT score.

CONCLUSION

Fluoxetine may enhance cognition in certain cognitive domains and serum concentration of BDNF and VEGF in patients with VCIND.

Biopsychosocial Predictors of Cognitive Impairment in the Elderly: A Case-control Study

Background:

Cognitive impairment is one of the most common diseases in the elderly. Several studies have already been conducted to identify related factors, but few have explored all the factors involved in the development of cognitive problems.

Objective:

The present study aimed to identify significant biopsychosocial predictors of cognitive impairment.

Methods::

This case-control study was conducted on 535 elderly people referred to Shafa Clinic in the city of Tehran in 2017. The biological factors including serum cholesterol, fasting blood sugar, systolic and diastolic blood pressure, vitamin D, vitamin B12, serum folate, serum homocysteine, height, and weight were measured. The psychological variable in this study was a history of depression that was extracted from the medical records. Social network and social support were measured by LSNS-6 and MOS-SSS questionnaires. The SPSS version 25 was used to analyze the data.

Results:

The mean age of the control group was 68.4 years (SD = 5.89) and of the case group was 71.5 years (SD = 7.37). The results of multiple logistic regression analysis showed age (AOR=1.05; CI:1.089-1.016, p≤0.05,), Secondary education (AOR=0.51; CI:0.266-0.990, p<0.05,), Tertiary education (AOR=0.41; CI:0.212-0.810, p<0.01,), hypertension (AOR=2.16; CI:3.671-1.266, p<0.01) homocysteine level (AOR=1.09; CI:1.147-1.045, p<0.001,), Hypothyroidism (AOR=0.43; CI: 0.226 0.820, p<0.001,), and depression (AOR=4.5; CI:7.163-2.822, p<0.001) to be significant predictors of cognitive impairment.

Conclusion:

Results of this study showed that low education level, high blood pressure, high level of homocysteine and depression likely increase the risk of cognitive impairment; also, it was implied that timely screening can identify people at risk. The novelty of the present study is that it used a combination of the biopsychosocial factors to predict unique predictors of cognitive impairment.

Evaluation and Treatment of Vascular Cognitive Impairment by Transcranial Magnetic Stimulation

The exact relationship between cognitive functioning, cortical excitability, and synaptic plasticity in dementia is not completely understood. Vascular cognitive impairment (VCI) is deemed to be the most common cognitive disorder in the elderly since it encompasses any degree of vascular-based cognitive decline. In different cognitive disorders, including VCI, transcranial magnetic stimulation (TMS) can be exploited as a noninvasive tool able to evaluate in vivo the cortical excitability, the propension to undergo neural plastic phenomena, and the underlying transmission pathways. Overall, TMS in VCI revealed enhanced cortical excitability and synaptic plasticity that seem to correlate with the disease process and progression. In some patients, such plasticity may be considered as an adaptive response to disease progression, thus allowing the preservation of motor programming and execution. Recent findings also point out the possibility to employ TMS to predict cognitive deterioration in the so-called "brains at risk" for dementia, which may be those patients who benefit more of disease-modifying drugs and rehabilitative or neuromodulatory approaches, such as those based on repetitive TMS (rTMS). Finally, TMS can be exploited to select the responders to specific drugs in the attempt to maximize the response and to restore maladaptive plasticity. While no single TMS index owns enough specificity, a panel of TMS-derived measures can support VCI diagnosis and identify early markers of progression into dementia. This work reviews all TMS and rTMS studies on VCI. The aim is to evaluate how cortical excitability, plasticity, and connectivity interact in the pathophysiology of the impairment and to provide a translational perspective towards novel treatments of these patients. Current pitfalls and limitations of both studies and techniques are also discussed, together with possible solutions and future research agenda.

The Influence of Nonpharmacological Complex Therapy Conducted at a Community Day-Care Center on Cognitive function and Mood in Older Adults

Introduction

Nonpharmacological interventions in the elderly may lead to the reduction of cognitive and depressive symptoms. The aim of the study was to evaluate changes in cognitive functions and mood in older adults participating in therapy, conducted in the community day-care center (CD-CC).

Patients and Methods

The study group (SG) included 46 elderly adults (21 M, 25 W), the control group (CG) included 45 adults (12 M, 33 W), who participated in the activities of the University of the Third Age. The following measuring tools were used: Mini-Mental State Examination, Clock-Drawing Test, Verbal Fluency Test, Digit Span Test, Stroop Color and Word Test, Beck’s Depression Inventory, and Hospital Anxiety and Depression Scale. The intervention consisted of CD-CC 6-month nonpharmacological therapy.

Results

In the SG, compared to the CG, the scores on all the cognitive tests were significantly lower, Beck’s Depression Inventory was significantly higher. After intervention, the SG and the CG did not show substantial differences in their scores on the Mini-Mental State Examination, Clock-Drawing Test, and Beck’s Depression Inventory. In the SG, a significant improvement was reported on the Verbal Fluency Test, Beck’s Depression Inventory and Hospital Anxiety and Depression Scale scores.

Conclusion

The CD-CC complex therapy can be helpful for cognitive and emotional elderly functioning.

A Customized Next-Generation Sequencing-Based Panel to Identify Novel Genetic Variants in Dementing Disorders: A Pilot Study

Purpose

The advancements in the next-generation sequencing (NGS) techniques have allowed for rapid, efficient, and cost-time-effective genetic variant detection. However, in both clinical practice and research setting, sequencing is still often limited to the use of gene panels clinically targeted on the genes underlying the disease of interest.

Methods

We performed a neurogenetic study through an ad hoc NGS-based custom sequencing gene panel in order to screen 16 genes in 8 patients with different types of degenerative cognitive disorders (Alzheimer's disease, mild cognitive impairment, frontotemporal dementia, and dementia associated with Parkinson's disease). The study protocol was based on previous evidence showing a high sensitivity and specificity of the technique even when the panel is limited to some hotspot exons.

Results

We found variants of the TREM2 and APP genes in three patients; these have been previously identified as pathogenic or likely pathogenic and, therefore, considered "disease causing." In the remaining subjects, the pathogenicity was evaluated according to the guidelines of the American College of Medical Genetics (ACMG). In one patient, the p.R205W variant in the CHMP2B gene was found to be likely pathogenic of the disease. A variant in the CSF1R and SERPINI1 genes found in two patients was classified as benign, whereas the other two (in the GRN and APP genes) were classified as likely pathogenic according to the ACMG.

Conclusions

Notwithstanding the preliminary value of this study, some rare genetic variants with a probable disease association were detected. Although future application of NGS-based sensors and further replication of these experimental data are needed, this approach seems to offer promising translational perspectives in the diagnosis and management of a wide range of neurodegenerative disorders.

Yuzu and Hesperidin Ameliorate Blood-Brain Barrier Disruption during Hypoxia via Antioxidant Activity

Yuzu and its main component, hesperidin (HSP), have several health benefits owing to their anti-inflammatory and antioxidant properties. We examined the effects of yuzu and HSP on blood-brain barrier (BBB) dysfunction during ischemia/hypoxia in an in vivo animal model and an in vitro BBB endothelial cell model, and also investigated the underlying mechanisms. In an in vitro BBB endothelial cell model, BBB permeability was determined by measurement of Evans blue extravasation in vivo and in vitro. The expression of tight junction proteins, such as claudin-5 and zonula occludens-1 (ZO-1), was detected by immunochemistry and western blotting, and the reactive oxygen species (ROS) level was measured by 2'7'-dichlorofluorescein diacetate intensity. Yuzu and HSP significantly ameliorated the increase in BBB permeability and the disruption of claudin-5 and ZO-1 in both in vivo and in vitro models. In bEnd.3 cells, yuzu and HSP were shown to inhibit the disruption of claudin-5 and ZO-1 during hypoxia, and the protective effects of yuzu and HSP on claudin-5 degradation seemed to be mediated by Forkhead box O 3a (FoxO3a) and matrix metalloproteinase (MMP)-3/9. In addition, well-known antioxidants, trolox and N-acetyl cysteine, significantly attenuated the BBB permeability increase, disruption of claudin-5 and ZO-1, and FoxO3a activation during hypoxia, suggesting that ROS are important mediators of BBB dysfunction during hypoxia. Collectively, these results indicate that yuzu and HSP protect the BBB against dysfunction via maintaining integrity of claudin-5 and ZO-1, and these effects of yuzu and HSP appear to be a facet of their antioxidant properties. Our findings may contribute to therapeutic strategies for BBB-associated neurodegenerative diseases.

Cognitive and emotional impairment in patients with chronic cerebrovascular insufficiency

Cerebrovascular disease is one of the most important problems of clinical neurology, which is a significant cause of cognitive impairment and depression. Chronic forms of cerebrovascular insufficiency are most often associated with cerebral microangiopathy or a disease of small vessels, which is characterized by the presence of lacunae, microinfarction and microbleeding, leukoaraiosis and dilated perivascular spaces. One of the main and most common clinical symptoms is vascular cognitive impairment. They are characterized by extremely variable cognitive deficits, highly dependent on the location and severity of vascular damage. However, clinical manifestations associated with impaired frontal circulation are usually observed. Recent international criteria for vascular cognitive impairment presented by the VASCOG (International Society for Vascular Behavioral and Cognitive Disorders) working group emphasize the particular importance of impaired information processing speed, attention, and/or frontal regulatory functions, often in combination with personality or emotional disorders. The frequency of vascular depression in chronic cerebrovascular insufficiency reaches 70%. The addition of affective disorders significantly aggravates the existing cognitive deficit, increases the risk of dementia. This is due to the fact that depression itself leads to the development of cognitive impairment, causes multiple functional disorders of cerebral microcirculation and a number of other mechanisms. The presence of cerebral microangiopathy underlying this pathology makes the use of drugs with vascular effects in the treatment of these patients. The use of preparations with multimodal action, in particular the combined drug and, is most preferable.

The Future of Targeted Gene-Based Treatment Strategies and Biomarkers in Parkinson's Disease

Biomarkers and disease-modifying therapies are both urgent unmet medical needs in the treatment of Parkinson's disease (PD) and must be developed concurrently because of their interdependent relationship: biomarkers for the early detection of disease (i.e., prior to overt neurodegeneration) are necessary in order for patients to receive maximal therapeutic benefit and vice versa; disease-modifying therapies must become available for patients whose potential for disease diagnosis and prognosis can be predicted with biomarkers. This review provides an overview of the milestones achieved to date in the therapeutic strategy development of disease-modifying therapies and biomarkers for PD, with a focus on the most common and advanced genetically linked targets alpha-synuclein (SNCA), leucine-rich repeat kinase-2 (LRRK2) and glucocerebrosidase (GBA1). Furthermore, we discuss the convergence of the different pathways and the importance of patient stratification and how these advances may apply more broadly to idiopathic PD. The heterogeneity of PD poses a challenge for therapeutic and biomarker development, however, the one gene- one target approach has brought us closer than ever before to an unprecedented number of clinical trials and biomarker advancements.

[The role of oxidative stress in the development of vascular cognitive disorders]

Vascular cognitive impairment (VCI) is one of the most serious problems of clinical neurology, being the second most common cause of dementia. VCI covers a range of disorders in which vascular factors cause or contribute to cognitive decline. Among the main risk factors for VCI are old age and vascular factors, which lead to endothelial dysfunction and damage, which, in turn, can cause neurovascular dysfunction, increased permeability of the blood-brain barrier, and microvascular thrombosis. Oxidative stress is one of the most important mechanisms for the development of VCI that indicates the need for the use of agents with antioxidant activity. One of these drugs is ethylmethylhydroxypyridine succinate (mexidol). Mexidol is a drug with marked antioxidant and antihypoxic activities. The clinical efficacy of mexidol in relation to VCI has been demonstrated in many studies.

A Customized Next-Generation Sequencing-Based Panel to Identify Novel Genetic Variants in Dementing Disorders: A Pilot Study

PURPOSE

The advancements in the next-generation sequencing (NGS) techniques have allowed for rapid, efficient, and cost-time-effective genetic variant detection. However, in both clinical practice and research setting, sequencing is still often limited to the use of gene panels clinically targeted on the genes underlying the disease of interest.

METHODS

We performed a neurogenetic study through an ad hoc NGS-based custom sequencing gene panel in order to screen 16 genes in 8 patients with different types of degenerative cognitive disorders (Alzheimer's disease, mild cognitive impairment, frontotemporal dementia, and dementia associated with Parkinson's disease). The study protocol was based on previous evidence showing a high sensitivity and specificity of the technique even when the panel is limited to some hotspot exons.

RESULTS

We found variants of the TREM2 and APP genes in three patients; these have been previously identified as pathogenic or likely pathogenic and, therefore, considered "disease causing." In the remaining subjects, the pathogenicity was evaluated according to the guidelines of the American College of Medical Genetics (ACMG). In one patient, the p.R205W variant in the CHMP2B gene was found to be likely pathogenic of the disease. A variant in the CSF1R and SERPINI1 genes found in two patients was classified as benign, whereas the other two (in the GRN and APP genes) were classified as likely pathogenic according to the ACMG.

CONCLUSIONS

Notwithstanding the preliminary value of this study, some rare genetic variants with a probable disease association were detected. Although future application of NGS-based sensors and further replication of these experimental data are needed, this approach seems to offer promising translational perspectives in the diagnosis and management of a wide range of neurodegenerative disorders.

Evaluation and Treatment of Vascular Cognitive Impairment by Transcranial Magnetic Stimulation

The exact relationship between cognitive functioning, cortical excitability, and synaptic plasticity in dementia is not completely understood. Vascular cognitive impairment (VCI) is deemed to be the most common cognitive disorder in the elderly since it encompasses any degree of vascular-based cognitive decline. In different cognitive disorders, including VCI, transcranial magnetic stimulation (TMS) can be exploited as a noninvasive tool able to evaluate in vivo the cortical excitability, the propension to undergo neural plastic phenomena, and the underlying transmission pathways. Overall, TMS in VCI revealed enhanced cortical excitability and synaptic plasticity that seem to correlate with the disease process and progression. In some patients, such plasticity may be considered as an adaptive response to disease progression, thus allowing the preservation of motor programming and execution. Recent findings also point out the possibility to employ TMS to predict cognitive deterioration in the so-called "brains at risk" for dementia, which may be those patients who benefit more of disease-modifying drugs and rehabilitative or neuromodulatory approaches, such as those based on repetitive TMS (rTMS). Finally, TMS can be exploited to select the responders to specific drugs in the attempt to maximize the response and to restore maladaptive plasticity. While no single TMS index owns enough specificity, a panel of TMS-derived measures can support VCI diagnosis and identify early markers of progression into dementia. This work reviews all TMS and rTMS studies on VCI. The aim is to evaluate how cortical excitability, plasticity, and connectivity interact in the pathophysiology of the impairment and to provide a translational perspective towards novel treatments of these patients. Current pitfalls and limitations of both studies and techniques are also discussed, together with possible solutions and future research agenda.