The Resilient Brain. Imaging Biomarkers of Brain Metabolic Reserve

Lead Research Organisation: Royal Veterinary College
Department Name: Comparative Biomedical Sciences CBS

Abstract

This proposal aims to validate two innovative biomarkers of brain resilience to ageing. The biomarkers use two well-known and widely available imaging technologies, magnetic resonance imaging (MRI) and positron emission tomography (PET) that are presently used both in animals and humans.
The quest for biomarkers of ageing is a difficult one as their necessary requirement is prediction power - ideally, when studying an intervention aimed at modulating the ageing process, we would like to know its effect on the ageing trajectory as soon as possible without having to wait for the ageing process to eventually happen. In the case of brain, this can be achieved if we can measure its resilience - and the one relevant biological parameter determining the ability to withhold cellular pathology is its metabolic reserve.
Why metabolism? In the average adult human, the brain represents about 2% of the total body weight yet it accounts for 20% of all the energy consumed, 10 times that predicted by its weight alone. Note that this very high rate of energy consumption is required only by its resting state while the additional energy associated with any mental activity is remarkably small, often less than 5% of the baseline.
In this highly energetic organ, metabolic reserve is the amount of energy reserve that brain cells can still use to fight all those pathological phenomena that we call ageing. Big metabolic reserve will then mean great resilience to ageing, poor or no reserve means little or no resilience.
When measuring energy reserve we wish to target the functioning of small cellular organelles called mitochondria. There are two key observations about mitochondria.
1)They are the fundamental elements of the cellular machine performing aerobic respiration e.g. using oxygen to oxidise the products of glucose and convert them into energy.
2) The process of mitochondria maintenance is highly dynamic with a constant turnover of these components particularly the older and damaged ones.
We have focused on these two key aspects of mitochondrial function and devised two measures.
1) MEASURE 1 - We wish to measure mitochondrial respiratory reserve capacity by measuring oxygen cellular metabolism with MRI before and after a challenge with Methylene Blue (MB). MB is a compound, already authorized for human use, that induces substantial increases (>40%) in cell respiration. Using MB we can expand mitochondrial capacity to its limit, far more than using any mental task that requires very little incremental energy and is far less controllable in an experimental or clinical setting.
2) MEASURE 2 - We wish to measure the level of expression of one particular mitochondrial protein, called the 18Kd translocator protein or TSPO. TSPO regulates mitochondrial turnover and acts as a quality controller driving the process that removes defective mitochondria following damage or stress. Importantly TSPO levels can be measured in-vivo by PET in both animals and humans.
We will validate these measures by following through time two groups of rats. One group of rats will be submitted to an intervention which is known to benefit the brain ageing process and mitochondria function in particular. The treatment will consist in environmental enrichment and dietary restriction by which we will mimic human healthy lifestyle. During their lifetime, we will continuously monitor their cognitive ability using appropriate tests and we will verify whether our measures, taken early on, predict their mental decline.
Once validated, these measures will be extremely powerful tools for ageing research. They will shorten timings in experimental settings and will allow an optimal use of animals as they do not require animal sacrifice. They will be immediately translated to humans as both imaging technologies and the pharmacological challenge used have been separately validated and authorized for human use.

Technical Summary

The great challenge of ageing research stays in its inherent time-scale where the ideal biomarkers are those that can qualify treatments at baseline without having to wait for the degenerative process to take place. Here we are concerned with brain ageing and focusing on metabolism as the brain has, by far, the highest energy demands of any organ based on its size. Importantly, the brain works at the border of its energy envelope as the majority of this energy is used to support neuronal activity and functional processes and is little affected by task performance. The metabolic reserve theory indeed proposes that a brain that is metabolic efficient is more resilient to declining cognition. It is now established that lifestyle determinants of metabolic reserve promote neuroprotection by increasing brain metabolic efficiency and creating an energetic buffer that can be used by the cell to fight pathology.
Mitochondria are fundamental to the maintenance of cellular health but with age they lose capacity for efficient ATP generation. Damaged mitochondria are generally cleared by mitophagy and protects from ageing-associated degeneration. This leads us to propose two in-vivo measures of brain metabolic reserve:
1) Cerebral Oxygen Metabolic Reserve obtained by measuring oxygen metabolism with quantitative BOLD MRI before and after administration of methylene blue (MB), an inducer of metabolic respiration already approved for use in man. The use of MB will allow us to tap into cellular energetic buffers that would not be otherwise accessed by experimental tasks (e.g. sensory stimulation).
2) Density expression of the 18K Translocator Protein (TSPO). TSPO is a mitochondrial protein with a fundamental role in mitochondrial quality control that in man is visualized using Positron Emission Tomography.
Measures will be validated in a longitudinal setting to determine their potential to predict cognitive resilience in well-characterized models of healthy ageing.

Planned Impact

This proposal focuses on the validation of two novel measurements of brain metabolic reserve to be used in the study of ageing and neurodegenerative disorders in animal and, in the future, human models. This project, if successful, will have substantial and lasting impact.
The increasingly large ageing population places great pressure on the HEALTH AND SOCIAL CARE SYSTEMS. Currently 16% of the European population is over 65, with this figure to reach 25% by 2030. Effective and predictive biomarkers are key to develop therapies and products aimed at improving lifelong health and wellbeing. Effective biomarkers will allow INDUSTRIES to effectively accelerate the development of products aimed at the ageing population market and enable REGULATORY AGENCIES to test the anti-ageing treatments that are now flooding the market. These include, for example, some poorly validated interventions such as improving antioxidant status and hormone replacement therapies, including growth hormone, testosterone, dehydroepiandrosterone, and melatonin (Butler et al, Journal of Gerontology: Biological Sciences, 2004, Vol. 59A, No. 6, 560-567).
It is easy to predict the immediate translation of these methodologies also to the study of neurodegenerative disorders. These are conditions that result in the progressive degeneration or death of nerve cells. They include Alzheimer's disease and other dementias, Parkinson's disease, Huntington's disease, motor neuron disease and multiple sclerosis. In the UK it has been estimated that dementia alone costs the ECONOMY £17 billion pounds a year, hence any effective development in this area will impact not only patients but also CARERS, HEALTH PROFESSIONALS and SOCIETY AT LARGE.
The methodologies proposed are destined to be used on MRI and PET scanners for animal and human use. If effective, they will expand their number and their use of these existing technologies in research, industry and in the clinic making them more economically viable. Hencethey will have direct impact on MEDICAL DIAGNOSTICS INDUSTRIES (General Electric, Siemens, Phillips, Bruker etc.).
Importantly, by targeting in-vivo biomarkers of mitochondrial function, we are working in a largely un-explored area of the neurosciences. In the recent past, concerns have existed about the growing number of companies disinvesting from neuroscience research in the UK. This has negatively impacted JOBS in this area and the UK ECONOMY at large. The tide has been turning recently with companies with long heritage in brain research such as Lily, Johnson and Johnson, Lundbeck and GSK supporting innovative programmes such as One Mind for research (1mind4research.org) to create a united effort to advance translational research for mental health between GOVERNMENT, ACADEMIA and INDUSTRY. We are already part of one Wellcome supported consortium that unites the organizations above for a strategic award in the area of dementias and mood disorders, all related to ageing, where the need for effective markers of brain bioenergetics is strongly felt.
Finally, it is worth remarking the unique nature of the proposing team with members working in an original setting that stretches from cellular biology to pharmacology, brain energetics, physics, engineering, nuclear imaging and psychology. The scientists and RAs working in this project will have a unique opportunity to expand their KNOWLEDGE BASE from cell biology to cognition, increasing their SKILL-SET in unprecedented fashion. As academics we will be able to communicate the hopefully successful return of this investment to our student population and to the PUBLIC.

Publications

10 25 50
 
Description The major findings from the work developed till now regard the parallel between mitochondrial import of cholesterol and oxysterols which are involved in neurodegenerative phenotypes. The work developed in the past year lead to a revolution in our understanding of intracellular pathways of communications based on the priming by cholesterol fluxes. Specifically it has been corroborated how the lipid, trafficked by TSPO, may become a signalling molecule key for the communication with the nucleus and hence by framing the retrograde response at the basis of cellular adaption to pathological cues. This is therefore applicable not just to the homeostasis of neuronal cells but to other cell types undergoing metabolic stress of hormonal nature leading to uncontrolled proliferation. Nonetheless cholesterol accumulates on specific points of contact between mitochondria and nucleus which establish a physical interaction between the two organelles which has never been reported before. To further characterize the impact of this novel signalling cascade on neuronal metabolic reservoir, we generated a TSPO KO SH-SY5Y cell line via CRISPR/Cas9-mediated genome editing, and carried out an RNAseq analysis to identify alterations in pathways regulating metabolic stress sensing and adaptation.
Exploitation Route These are likely to deliver both an academic and applicative outcome. One major research paper is currently being finalised with the hope to see it published in this academic year and discussions with companies are currently ongoing to learn how to translate this into a deliverable bearing a positive impact to the society.
Sectors Chemicals,Education,Healthcare,Pharmaceuticals and Medical Biotechnology

URL https://www.biorxiv.org/content/10.1101/445411v2.full.pdf
 
Description 3i Case Panel Memmbership BBSRC London Interdisciplinary Biosciences PhD Consortium
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Participation in a advisory committee
 
Description BBSRC London Interdisciplinary Biosciences PhD Consortium
Amount £100,000 (GBP)
Funding ID Flirting In The Little Space: Homeostatic Regulation of The Mitochondria and Cytoskeleton Interplay via The Tubulin-­Vdac-­Tspo Pathway 
Organisation Bloomsbury Colleges 
Sector Academic/University
Country United Kingdom
Start 10/2016 
End 10/2020
 
Description BBSRC Project Grant
Amount £450,000 (GBP)
Funding ID BB/N007042/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 09/2016 
End 08/2019
 
Description BBSRC iCase Studentship
Amount £150,000 (GBP)
Funding ID Bioactive targets of mitochondrial quality control and function. 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 10/2016 
End 09/2020
 
Description BBSRC-LiDo Studentship
Amount £105,000 (GBP)
Funding ID Imaging the Ageing Brain: Cellular and PET Tracing of the Neuroinflammatory Protein TSPO 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 10/2014 
End 09/2018
 
Description BBSRC-iCase Studentship
Amount £150,000 (GBP)
Funding ID Focusing on the mitochondrial expression of TSPO as a marker and promoter of neuroinflammation 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 10/2015 
End 09/2019
 
Description Form and Function of the Mitochondrial Retrograde Response
Amount £1,400,000 (GBP)
Funding ID European Research Council Consolidator Grant 
Organisation European Research Council (ERC) 
Sector Public
Country Belgium
Start 11/2019 
End 11/2024
 
Description Research Grant
Amount £87,000 (GBP)
Funding ID Chemo-targeting of TSPO to validate Endocrine Therapy in Canine Mammary Tumours 
Organisation Petplan Charitable Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2017 
End 03/2019
 
Title Cancer Biomarker 
Description We are devising a way via which we can score tumor stages in animals by checking TSPO expression 
Type Of Material Biological samples 
Provided To Others? No  
Impact A potential way to image diagnostically tumor stage and progression via TSPO 
 
Title Mitophagy Inducer 
Description A new tool to physiologically activate mitophagy which we called PMI as working via the p62 pathway. 
Type Of Material Technology assay or reagent 
Provided To Others? No  
Impact Mitochondrial quality control is a fundamental process in cellular homeostasis, and its deficiency is linked to several neurodegenerative diseases and cancers. Despite this, the discrete mechanisms, regulatory pathways, and impact oncellular physiology are still far from being elucidated. The current canonical methods to trigger mitophagy in vitro typically involve the abrupt depolarization of mitochondrial membrane potential (DYm) using ionophores such as carbonyl cyanide m-chlorophenyl hydraz 
 
Title TSPO marking to detect mito-nuclear contact sites 
Description TSPO is found to be required for the establishment of contact sites between mitochondria and nucleus, This has allowed us to enrol the protein to assess the frequency of these contacts. 
Type Of Material Model of mechanisms or symptoms - in vitro 
Year Produced 2018 
Provided To Others? No  
Impact Impact is potentially multiple given the ground-breaking nature of the discovery and ability gained to map this interaction which bears implications for inter-organelles communication and core functions regulation. 
 
Description Elucidate the Neuronal Cell Biology of the Neuroimaging Tool TSPO 
Organisation King's College London
Department Brain Bank
Country United Kingdom 
Sector Academic/University 
PI Contribution Coordination of the research work on functional role of the PET tracer TSPO in neuronal cell physiology and toxicity determination.
Collaborator Contribution Research Grant Share to support a PDRA and consumable.
Impact A manuscript is now submitted for final revision which will outline TSPO role in neurotoxicity besides characterising its function in cell signalling homeostasis.
Start Year 2014
 
Description TSPO role in Hormonal Chemotherapy Resistance 
Organisation Imperial College London
Country United Kingdom 
Sector Academic/University 
PI Contribution We are defining the link between cholesterol mediated resistance to hormonal chemotherapy and TSPO triggered expression in mammary cancer models.
Collaborator Contribution The main goal is trap the definition of pro-survival genes transcription mediated by TSPO and its potential intracellular relocation from mitochondrial outer membrane when pathologically overexpressed. Concomitantly TSPO ligands are being tested as pharmacological means to facilitate/promote chemotherapy induced cell death and prevent long-term resistance.
Impact Grants is being drafted
Start Year 2016
 
Description Testing mitochondrial mechanisms as early marker of Drugs Attrition 
Organisation Royal Veterinary College (RVC)
Country United Kingdom 
Sector Academic/University 
PI Contribution The Royal Veterinary, University of London
Collaborator Contribution By the work on TSPO we succeeded in devising a suitable protocol via which we could detect mitochondrial toxicity and therefore provide early detection of pharmaceuticals which might reveal in vivo toxicity.
Impact We hope to gain sufficient evidences to secure valuable Intellectual Property.
Start Year 2018
 
Description Testing of the antipsychotic drugs on TSPO 
Organisation King's College London
Department Brain Bank
Country United Kingdom 
Sector Academic/University 
PI Contribution Research Group of Dr. Anthony Vernon (King's College London Institute of Psychiatric)
Collaborator Contribution Expertise in clinical pharmacology, sharing of reagents.
Impact Clarification of TSPO role in trafficking neuro specific drugs, affecting their performance and outcome.
Start Year 2017
 
Description Invited Seminar Talk at specialised audience 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Invited Seminar at the Beatson Institute for Cancer Research on September the 6th 2018
Year(s) Of Engagement Activity 2018
 
Description Invited Talk 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited Talk to deliver updates on our work of TSPO in neuronal models.
Year(s) Of Engagement Activity 2018
URL http://www.biophysics.org/Membership/Subgroups/Bioenergetics/tabid/506/Default.aspx
 
Description Invited Talk at Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Audience of industrial experts in the field of drug discovery.
Year(s) Of Engagement Activity 2018
 
Description Invited Talk at the Redox Society of Medicine and Biology Annual Meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Update on our work on the interpay between stress response mecchanims and redox stress
Year(s) Of Engagement Activity 2019
 
Description Invited Talk in conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Invited presentation on mitochondrial regulation of inflammation and new regulatory mechanisms we have unveiled.
Year(s) Of Engagement Activity 2018
 
Description Lay article 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Blog articles in Connected Health Quarterly
Year(s) Of Engagement Activity 2015,2016,2017
URL http://www.connectedhealthquarterly.com/category/dr-radha-desai/
 
Description Meeting with experts 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Chairing a focused workshop session on the meaning in Physiology and Pathology of Mitochondrial Biology
Year(s) Of Engagement Activity 2017
 
Description New Scientist Live 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Participation in New Scientist Live as part of the Society of Biology's 'Ask a Biologist' initiative
Year(s) Of Engagement Activity 2017
URL https://www.youtube.com/watch?v=d9K5r4j2PcY&t=5s
 
Description Oral Presentation on mito-nuclear contact sites at the EMBO workshop on on Membranes Contact Sites in Health and Diseases 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Oral presentation on our original research in energy balance and cross-organelles communication.
Year(s) Of Engagement Activity 2018
 
Description Presentation to a group of patients 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Patients, carers and/or patient groups
Results and Impact Illustrate how our activities could inform new ways of treatments and handling of neurodegenerative conditions.
Year(s) Of Engagement Activity 2018