Remote ischemic conditioning of the brain in dementia patients:protocol for a crossover non-pharmaceutical intervention study

Christos Voucharas

1st Department of Neurology,School of Medicine,Aristotle University of Thessaloniki,Thessaloniki,Greece

Abstract

Key words:cognitive impairment；dementia；ischemic conditioning；neuroprotection；perconditioning；postconditioning；remote ischemia

INTRODUCTION

Tolerance of an organ or tissue to ischemia/reperfusion injury is an endogenous phenomenon that can be provoked by preceded nonfatal ischemia.Ischemic preconditioning is the first discovered form of tolerance to ischemia；it occurs widely in many animal species and in humans and in various organs including the brain and spinal cord.1,2

Brain ischemia is postulated as a main reason for vascular dementia；moreover it plays a significant role in all other forms of dementia.

Ischemic conditioning (IC) refers to repetitive,transient and sublethal series of ischemia/reperfusion (I/R) bursts that can trigger endogenous protection and tolerance against subsequent ischemic threats.1,2

Remote ischemic conditioning (RIC) that is a brief,repetitive and sublethal I/R injury applied to an organ or tissue far from the target organ,may benefit multiple organs of the body at the same time,such as heart,brain,spinal cord,kidney,lung,liver and skin.RIC has advantage over classic IC since it does not compromise vital organs such as the myocardium or the brain.3Remote conditioning of the brain regarding transient ischemia/reperfusion caused to another organ or tissue far from the cerebrum,has advantage over classic ischemic conditioning,since it does not compromise the brain with irreversible neuronal damage.The brain's protection by remote condition can be ahead of (preconditioning) or during (perconditioning)or following (postconditioning) the influence of the harmful stimulus.3,4It seems to be a promising non-pharmaceutical and non-invasive therapy for preventing and treating age-related systemic vascular diseases such as combined lesions in the brain and also arteriosclerosis-induced neurodegenerative disorders.4

The possible underlying mechanisms are correlated with several aspects,mainly including neuronal,humoral and immune-inflammatory (complement reaction) pathways,all of which also display inseparable interactions with each other.The role of epigenetics remains to be clarified.5

There are three methods of RIC intervention based on timing of RIC in relation to I/R injury,including remote ischemic preconditioning (RIPreC,initiated before I/R injury),remote ischemic perconditioning (RIPerC,initiated during ischemia continuation) and remote ischemic postconditioning (RIPostC,initiated after ischemia has been established).6The three methods of IC correspond to the three human subgroups experiencing a) normal cognitive function,b) mild cognitive impairment and c) mild or moderate dementia,accordingly.

Previous experimental work in humans applied pressure cuff on the upper limp in order to induce ischemia of a remote organ.The method carries a lot of disadvantages such as discomfort for the individual,risk for deep vein thrombosis,not extended ischemia,controversy relating to the degree,the duration and the number of the pressure cycles.In fact there is a paucity of clinical data comparing the effectiveness of different RIC protocols,and no convincing evidence of the most favorable conditioning strategy has been established.7

Peripheral arteriopathy leading to intermittent claudication is frequently seen in the older adults as a result of progressive atherosclerosis,diabetes mellitus,coronary and great vessels of the neck insufficiency.

Limp ischemia caused by promoting exercise to the point of claudication guaranties extended ischemia of one or even both limps.Not only is the exercise completely harmless for the individual suffering from lower limp arteriopathy,but it is highly recommended by the angiologists as well.We have designed our investigation to include individuals with potential claudication,who usually avoid the discomfort of muscular cramps and pain in everyday life,encouraging them to follow a structured physical exercise program.

The incidence of RIC has already been investigated in acute ischemic stroke,8,9chronic cerebral ischemia,10-13subarachnoid hemorrhage,14-19carotid endarterectomy and stenting,20,21cerebral small-vessel disease,22,23and traumatic brain injury.24

Whether RIC is efficient enough against cerebral I/R injury is controversial and further research will expand our knowledge in the field of cerebral protection.25-28Our investigation institutes the first time worldwide that RIC will be studied in different stages of dementia.

METHODS/DESIGN

Study design

The individuals that will be enrolled in this crossover study will be chosen among the “Alzheimer Hellas” association's cohort (https://www.alzheimer-hellas.gr/index.php/en/),approximately 10,000 people that are under the association's attention and care (Figure1).The protocol design is based on the Standard Protocol Items:Recommendations for Interventional Trials (SPIRIT) guidelines (Additional file 1).

The whole study will be under the supervision of the 1stNeurology Department of the Aristotle University of Thessaloniki and the “Alzheimer Hellas” (Head - Professor Magda Tsolaki,ORCID 0000-0002-2072-8010).

Eligible criteria

Figure1:Study flowchart.

People with severe peripheral arteriopathy can potentially experience intermittent claudication after structured aerobic exercise.They all will be subjects of Fontaine's stage IIb or Rutherford's category 3 of chronic arteriopathy.29,30This means they will experience claudication in less than 200 meters walking distance.Severe dementia patients are excluded the design because they cannot follow the exercise program (postconditioning group).Individuals that will not be able to follow the exercise program for more than 2 days for any reason will also be excluded.

Recruitment

The considered subgroups will be built as below:

Group A,patients with arteriopathy and mild cognitive dysfunction,30 individuals (perconditioning)；

Group B,patients with arteriopathy and mild dementia,30 individuals (postconditioning)；

Group C,patients with arteriopathy and moderate dementia,30 individuals (postconditioning).

Each of the groups A,B and C will be compared to each self from the baseline to the end of the investigation.Additional examination will be held 6 months later to examine if the potent result is permanent or is lost.

Blinding

Only the psychologists that will carry out the cognitive scales will be blinded；unblinding is not permissible.

Baseline measures

A full medical history as well as duplex ultrasonography of the lower extremity vessels will be used to document the peripheral arteriopathy.The level of cerebral function will be checked at baseline with cognitive tests,electroencephalography,magnetic resonance imaging,blood tests,immunological examinations,event-related potentials and level of proteins of cerebrospinal fluid.

Intervention

Duplex ultrasonography of the lower extremity vessels as well as the vessels of the neck will be used to document the peripheral arteriopathy.People with arteriopathy will be encouraged to exercise everyday for a month's duration to the extent of claudication appearance.All three groups have to transact the same scheduled exercise.They have to walk to the extent of maximum 200 meters distance or equivalent,with a rhythm relating to their physical situation or concomi-tant disorders.All participants are supposed to have severe peripheral arteriopathy,so they easily experience claudication on exercise.In case of experiencing any discomfort due to fatigue,myocardial ischemia,insufficient cerebral perfusion(chest pain or dizziness),they have to terminate the walking effort.If claudication does not appear,the exercise should be stopped after 200 meters walking distance.

Outcome measures

Primary outcome measure is the change in cognitive function from the baseline to the end of the study,which will be assessed by cognitive scales (at least three different tests will confirm the documentation,Mini Mental State Examination,Change Test and Global Deterioration Scale).

Secondary outcome measures are electroencephalography,magnetic resonance imaging (white matter hyperintensities volume),blood tests (plasma total cholesterol,triglyceride,low density lipoprotein,homocysteine) and immunological examinations (including DNA methylation),cognitive induced potentials and cerebrospinal fluid examination (only at baseline),at the beginning and at the end of the study.All patients will be over the age of 65,since dementia is rare in younger ages.A complete medical history of every person participating in the study will be kept and all co-morbidities will be recorded.

The assessment schedule is shown in Table1.

Data collection,management,and monitoring

We will collect demographic data including patient's name,gender,and age.Case report form (CRF) will be written in a unified format,including patient's details,personal history,physical examination,special examination,laboratory examination,and patient signature.Data will be input into a computer database.All participant data will maintain personal privacy.The full names of the subjects will not be present in records or documents.Only their abbreviated names will be displayed.Clinical trial data will include written data and electronic data；all data will be accessible only by the author (administrator).

Sample size

For each of the three groups we will use a two-tailed test.We will accept aP＜ 0.05 as acceptable and a study with 80%power.The standard deviation in the common population variance is approximately 0.7.The intervention is expected(hypothesis) to improve cognitive function by 60% at minimum.According to the calculation the sample size for each group should be at least 21 individuals.31,32

Statistical analysis

Mental test scores will be expressed as the mean ± SEM.Two-tailed unpairedt-test will be used to compare the values before and after the procedure.Data in every separate group will have to pass normality test and differences between SEMs in compared groups (raw data) will have to be due to random sampling.A difference will be considered statistically significant ifP＜ 0.05.The results of the remaining tests will confirm the potent statistic differences.

Ethics and dissemination

All individuals will be informed about the design and the purpose of the study and will be given informed consent(Additional file 2).The study was approved by the Ethical Committee of the “Greek Association of Alzheimer's Disease and Related Disorders” (Alzheimer Hellas) (Pr Nr 250 / 2019 AI) on November 8,2019 (Additional file 3).

This study will conduct in accordance with theDeclaration of Helsinki,formulated by the World Medical Association.The findings of this study will be submitted to an open-access peer-reviewed journal.

DISCUSSION

The aim of our study is to determine whether there is a beneficial effect after applying remote ischemic conditioning to individuals with different stages of dementia.Our investigation does not intent to suggest methods of provoking remote transient ischemia；in fact a small proportion of the elderly has intermittent claudication；however if evidence exists that RIC is effective,and the mechanism is not mild or ambiguous,then the scientists efforts will focus mainly in a way to achieve remote ischemia；for example an invasive or a non invasive technique that could temporarily obstruct the iliac or the femoral artery.

As the average human lifespan has increased markedly over the past decades,the mounting incidence of ageing-related dis-orders in the elderly and the related economic and social burden urge scientists all over the world to develop novel strategies to slow down or prevent these disorders.More well designed and comprehensive experimental work or clinical trials are warranted in future research to confirm whether RIC could be utilized as a non-invasive,inexpensive and efficient adjunct therapeutic intervention method for dementia confrontation.

Table1:Study assessment schedule

Expected deliverables

We are going to introduce a novel strategy to induce efficient limp ischemia in humans.This kind of ischemia not only does avail the limp of the individual and provokes neo-angiogenesis,but it induces ischemic preconditioning to many organ of the body as well.We study an endogenous mechanism in humans(IC) that is costless and easily applicable.We hope that remote ischemic conditioning applies successfully to prevention or deceleration of dementia.

TRIAL STATUS

Patient recruitment will begin in January 2020.Cognitive status and peripheral arterial disease estimation will begin in March 2020.Structured exercise will begin in May 2020.The post intervention cognitive status estimation will begin in June 2020.The late cognitive status estimation will begin in September 2020.The analysis of primary outcome measures will be completed in August 2021,and the study will finish up to December 2021 (dissemination of the results).

Additional files

Additional file 1:SPIRIT checklist.

Additional file 2:Model consent form.

Additional file 3:Ethical approval documentation.

Author contributions

Study concept and design,manuscript drafting:VC.The author gave final approval for publication.

Conflicts of interest

None declared.

Financial support

None.

Institutional review board statement

The study was approved by the Ethical Committee of the “Greek Association of Alzheimer's Disease and Related Disorders” (Alzheimer Hellas) (Pr Nr 250 / 2019 AI) on November 8,2019.

Declaration of patient consent

The author certify that all appropriate patient consent forms will be obtained.In the forms the patients will give their consent for their images and other clinical information to be reported in the journal.The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity,but anonymity cannot be guaranteed.

Reporting statement

This manuscript was prepared according to Standard Protocol Items:Recommendations for Interventional Trials (SPIRIT) statement.

Biostatistics statement

The statistical methods of this study were reviewed by the biostatistician of Aristotle University of Thessaloniki,Greece.

Copyright license agreement

The Copyright License Agreement has been signed by the author before publication.

Data sharing statement

Individual participant data that underlie the results reported in this article,after de-identification (text,tables,figures,and appendices)will be shared.Study protocol and informed consent form will also be available.Data will be available (start and end dates) immediately following publication,no end date,with investigations whose proposed use of the data has been approved by an independent review committee identified for this purpose,and for any purpose types of analysis.Proposals should be directed to voucharas@gmail.com.To gain access,data requestors will need to sign a data access agreement.

Plagiarism check

Checked twice by iThenticate.

Peer review

Externally peer reviewed.

Open access statement

This is an open access journal,and articles are distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License,which allows others to remix,tweak,and build upon the work non-commercially,as long as appropriate credit is given and the new creations are licensed under the identical terms.