Targeting the aspartic protease BACE1 for inhibition in order to increase hypothalamic leptin sensitivity and reverse obesity.

Lead Research Organisation: University of Dundee
Department Name: Cardiovascular and Diabetes Medicine

Abstract

Chronic obesity is currently at epidemic levels in the UK and many other countries worldwide and is having a major adverse impact on our society. It is estimated that more 25% of the adult population are obese and around two thirds are either overweight or obese. Worryingly over the last 20 years there has been a ~3 fold increase in the number of children and adolescents who are obese or overweight. This trend is alarming, as chronic obesity is associated with increased risk of a number of diseases such as diabetes, cardiovascular disease, Alzheimer's and a number of cancers. It is clear that our society is on a trajectory that will see significant increases in the proportion of individuals entering or in old age with severe chronic health issues. This places an enormous burden on the NHS and society generally, which is likely to worsen over the next 10-20 years if effective actions are not taken soon.

The hormone, leptin, plays an important role in the maintenance of long term body weight and fat levels in animals and humans, It acts in the brain, in an area called the hypothalamus, to decrease feeding and increase energy expenditure. However, leptin's effects on appetite and energy expenditure are diminished in aged and obese individuals, despite increased circulating levels of the hormone. This phenomenon is known as leptin resistance and is thought to be due to reduced transport of leptin into the brain and/or a loss of the ability of leptin to alter the function of cells in the hypothalamus. Thus in non-obese individuals leptin alters the amount of certain neurotransmitters within neurons, their release onto nearby cells and their actions on these cells. These effects are lost or diminished through diet-induced obesity in both humans and animal models of obesity. Presently there are few effective drug treatments for obesity and none that overcome leptin resistance in the hypothalamus.

The enzyme, BACE1 cuts a larger protein known as amyloid precursor protein resulting in smaller protein fragments, some of which are thought to be toxic and responsible for the pathology associated with Alzheimer's Disease (AD). Indeed, excessive activity of BACE1 in the brain is thought to be the primary driver for the neurodegeneration and cognitive dysfunction associated with AD. The amount and activity of BACE1 increases with age and following pathological stresses such as hypoxia, oxidative stress (e.g. free radicals) and physical brain injury, thus increasing the risk of AD. Features common to AD and to diabetes and obesity are the loss of function of important metabolic hormones such as insulin and leptin and the reduced ability of cells to take up and use glucose.

Consequently, we hypothesised that BACE1 plays an important role that connects cell stresses (metabolic, oxidative and inflammatory) with glucose and fat metabolism. To date our work has shown that removing or decreasing BACE1 in mice causes them to be lean, resistant to weight (fat) gain on a high fat (calorie) diet and to improve their ability to deal with increased amounts of glucose in the blood (as occurs after a meal). In other words, these mice appear resistant to obesity and diabetes normally induced by chronic excess caloric intake. In a pilot study we show that by reducing the amount of BACE1, leptin is more effective in the hypothalamus and remains so even when animals become obese (i.e obesity is reversible by increasing the amount of leptin in the blood). This information suggests that reducing BACE1 prevents or reverses leptin resistance. Importantly our recent experiments show that giving obese mice (which are resistant to endogenous leptin) a drug that inhibits BACE1 causes significant weight loss. We now wish to confirm and extend these preliminary findings by studying a larger number of animals made obese by high fat diet and to try to define what has changed in the hypothalamus to circumvent leptin resistance.

Technical Summary

Part 1: We will perform a comparative study of C57BL/6 BACE1-/-, BACE1+/-, and wild type littermate (BACE1+/+) mice, in which all three genotypes will be fed on regular or high fat diet for 20 (or longer for BACE1+/- mice) weeks (for HF diet sufficient time to induce DIO in wild type mice). In this longitudinal study we will determine how loss (BACE1-/- mice), reduction (BACE1+/- mice) and increased (via high fat diet) BACE1 affects RMR, body composition, food intake (basal and MTII modified) and plasma glucose and hormone (leptin, insulin) levels. At the end of the dietary period all three genotypes will be injected with leptin to explore the role of BACE1 on hypothalamic leptin sensitivity (measuring changes in food intake, hypothalamic neuropeptide expression and signalling strength of various leptin receptor-mediated pathways). These will be compared using peripheral and central routes of leptin administration.

Part 2: We will use the same criteria set out above to test the prediction that reduction of BACE1 activity in DIO wild type mice results in loss of body weight (reduced adiposity) concomitant with recovery of hypothalamic leptin sensitivity (i.e. reversal of high fat diet induced hypothalamic leptin resistance). Inhibition of BACE1 activity in mice will be induced through pharmacological inhibition by infusion or oral administration of small molecule non-peptide BACE1 inhibitors.

Part 3: We will determine whether the effects of BACE1 inhibition require the presence of leptin by oral administration of BACE1 inhibitor to ob/ob mice using the same output measures described above. Additionally, we will analyse dietary-modified leptin- and BACE1 inhibitor-treated hypothalamic tissue for evidence of BACE1-mediated alterations in signalling pathway networks associated with obesity and diabetes and/or known components of leptin signalling pathways. Peripheral tissues will be examined for evidence of altered levels of energy expenditure markers.

Planned Impact

There is strong evidence to show that our modern (westernized) lifestyles have caused an epidemic of metabolic disease, notably through the large increase in diabetes associated with soaring levels of obesity. Indeed, around a quarter of all adults in the UK are obese, and over 60% are overweight or obese. Similar figures or trends are reported in other westernised countries. These changes are closely linked to lifestyle factors such as increasingly inactive occupations and daily routines and poor diet. Importantly chronic obesity has a severe impact on the health of individuals, increasing the risk of Type 2 diabetes (80% of T2D patients are obese), some cancers and liver and heart disease. Diabetes and obesity have also been shown to be significant risk factors in the development of forms of dementia such as Alzheimer's disease. Worryingly, the incidence of these diseases is expected to increase dramatically over the next 10 - 20 years (as we live longer), increasing the proportion of individuals entering or in old age with severe chronic health issues. Given this impact on long-term health this places a significant burden on the NHS (and similar health care providers elsewhere in the world). UK direct costs (medical, social and economic) are put at £16 billion per year. More alarmingly, this cost is predicted to rise steeply over the next 30-40 years, and is likely to seriously undermine the prosperity of current and future generations.

At present there is no long-term effective treatment for obesity, and none that have been demonstrated biologically to reverse the state of hypothalamic leptin resistance, which is thought to drive this steady-state increased level of body fat. In this context it is clear that alternative strategies to reverse/treat the obese state are urgently required and would be of great benefit to the UK population (medical, social and economic), by enhancing long-term health and improved quality of life for the individual. The preliminar studies performed in our laboratory provide strong support for a role for BACE1 inhibition in the reversal of the obese state in an animal model of diet-induced obesity. The current project aims to build on this exciting data and will directly test the hypothesis that hypothalamic BACE1 levels/activity markedly influences hypothalamic leptin sensitivity and susceptibility to obesity. Most excitingly, in recent years a number of companies have begun testing small molecule BACE1 inhibitors (for Alzheimer's disease treatment). Assuming our hypothesis is correct, a clear opportunity exists to intervene pharmacologically to inhibit BACE1 and reverse hypothalamic leptin resistance resulting in increased energy expenditure and reduced adiposity. Within our research collaboration grouping, clinical colleagues are well placed through running Diabetes outpatient clinics and through the Dundee Clinical Research Centre to conduct small-scale human trials with appropriate BACE1 inhibitors. As numerous BACE1 inhibitors are becoming available we expect a rapid translation of our experimental findings into human disease.

In summary, the work described herein may result in outcomes that:

(i) offer potential pharmacological-based treatments for obesity, which can be fast-tracked into small clinical trials, with the strong possibility that better drugs may be rapidly developed in association with Pharmaceutical companies.

(ii) enhance the quality of life (and should extend life) for a substantial proportion of the adult (and perhaps adolescent/child) population

(iii) improve the effectiveness of NHS care and treatment, reduced NHS and other governmental costs associated with obesity and its co-morbidities.

Publications

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Botteri G (2018) The BACE1 product sAPPß induces ER stress and inflammation and impairs insulin signaling. in Metabolism: clinical and experimental

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Hardie DG (2014) AMPK: regulating energy balance at the cellular and whole body levels. in Physiology (Bethesda, Md.)

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Meakin P. J. (2017) Beta-amyloid promotes diabetes-like vascular dysfunction in mice in DIABETIC MEDICINE

 
Description European Union Horizon 2020 Research and Innovation Programme Innovative Medicines Initiative 2
Amount € 18,000,000 (EUR)
Funding ID 807015 
Organisation European Union 
Sector Public
Country European Union (EU)
Start 01/2019 
End 12/2021
 
Description Project Grant
Amount £289,872 (GBP)
Funding ID PG/15/44/31574 
Organisation British Heart Foundation (BHF) 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2015 
End 09/2018
 
Description Pump Priming
Amount £19,664 (GBP)
Organisation The Diabetes Research & Wellness Foundation 
Sector Charity/Non Profit
Country United Kingdom
Start 02/2017 
End 09/2017
 
Description Translational Medical Research Fund
Amount £19,829 (GBP)
Organisation University of Dundee 
Sector Academic/University
Country United Kingdom
Start 08/2014 
End 07/2015
 
Description Translational Medical Research Fund
Amount £10,000 (GBP)
Organisation University of Dundee 
Sector Academic/University
Country United Kingdom
Start 06/2014 
End 05/2015
 
Description Translational Medical Research Fund
Amount £93,000 (GBP)
Organisation University of Dundee 
Sector Academic/University
Country United Kingdom
Start 09/2013 
End 08/2015
 
Description Insulin Receptor is a substrate for BACE1 
Organisation Aix-Marseille University
Country France 
Sector Academic/University 
PI Contribution Provision of materials from BACE1KO mice and obese mice treated with Bace1 inhibitor; data from studies investigating insulin signalling in liver explants from Bace1KO and control mice
Collaborator Contribution Peiretti lab demonstrated that the insulin receptor in a substrate for Bace1 in cell-based overexpression studies and in some mouse transgenic model. Peiretti lab is lead on the collabortation, with my post-doc (Paul Meakin) as first author on manuscript in preparation.
Impact Manuscript accepted for publication in Nature Communications Disciplines: Molecular Biology, biochemistry, physiology
Start Year 2015
 
Description Careers week School Visit - Craigowl Primary 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Two members of my research team visited a local primary school as part of a careers week where they discussed their roles as scientists and in particular our interest in obesity and type II diabetes. The session included interactive learning games accompanied a short lay talk. These sessions were delivered to two different classes: primary 2/3 and primary 3/4 with a total of around 50 children attending. The sessions were very well received with plenty of enthusiasm from both the pupils and the teachers alongside positive feedback from the deputy head teacher.
Year(s) Of Engagement Activity 2017
 
Description Dementia under the microscope - Part of Dundee Science Festival 2016 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact This event ran from 18.00 until ~21.30 on Thursday 27th October 2016. For the first hour or so there were three formal talks.each with a Q & A session. Following this we organised Lab tours for those interested (small groups (~ six in each) visited four laboratory sites where they saw work demonstrated and explained (additional support from PhD students and other academic staff). 44 people attended the Lab tours, which resulted in us over-running the event (meant to finish at 20.00) and generated lots of questions and interest in basic and translational research into connections between metabolic disease (obesity, diabetes, CVD) and dementia.
Year(s) Of Engagement Activity 2016
 
Description Diabetes Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Health professionals
Results and Impact Diabetes UP Annual Professional Conference. Invited Talk in Session - Diabetes and the Brain - with attendance. Stimulated discussion with numerous questions following talk. Two members of my team present, who also presented talks and/or posters at this meeting, which stimulated interest and discussion.

Raised awareness of our research work with health professionals and pharmaceutical companies
Year(s) Of Engagement Activity 2014
 
Description Doors Open Dundee Weekend 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Around 50 people (mix of adults and children) attended as part of an open day in the Medical School. The team were asked numerous questions about diabetes and obesity and links to dementia. Feedback on the day and afterwords by e-mail was universally positive. Can you please do this again etc..
Year(s) Of Engagement Activity 2017
 
Description Dundee Science Festival 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Contribution to the Dundee Science Festival under the structured theme of Medicine and Health - our contribution was a full day (Saturday) of science based activities and information with a focus on diabetes and alzheimer's disease. Engagement with well over 100 people (adults, families etc) over the day - many reporting that they thoroughly enjoyed the experience and now have a better understanding of the scientific research effort in the area we promoted.
Year(s) Of Engagement Activity 2016
 
Description Dundee Science Festival - Dementia Research under the Microscope 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact This activity was very successful; we had a great deal of questions and discussion - particularly during and following the lab tours. The lab tours allowed members of the public to gain a better understanding of the research work being produced from the University of Dundee and also of the tools available to researchers for improving understanding of the diseases under investigation

Requests for additional information about the issues raised and discussions about donating to Alzheimer's research.
Year(s) Of Engagement Activity 2014
 
Description Dundee Science Festival - Family Fun day 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Interaction with the children often sparked more in depth conversation with parents or other members of the public, helping to dispel common misconceptions and increase understanding of the science behind neurodegenerative and metabolic diseases and what clinical options are currently available.

Increased awareness of how the brain works and what goes wrong in dementia to the general public. Members of the public left armed with more information and many said they had been able to answer queries that had been concerning them, especially if they had already had first hand experience of the disease.
Year(s) Of Engagement Activity 2014
URL http://www.dundeesciencecentre.org.uk/local/registration/DSF-report.pdf
 
Description Lab tour 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact High School class visit for a tour of various labs, including ours. Thet were very interested to see cell in culture.
Year(s) Of Engagement Activity 2018
 
Description MRC Festival 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact An open day (MRC Festival) run by School of Life Sciences, University of Dundee. Two of my PhD students ran a diabetes stall. A talk was also given on the connection between diabetes and Alzheimer's disease
Year(s) Of Engagement Activity 2018
URL https://www.youtube.com/watch?v=1wWYB92uAyk
 
Description Medical School open day 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact PhD students and staff ran various stalls to explain diabetes and vascular disease, with demonstrations.
Year(s) Of Engagement Activity 2018
 
Description Public engagement at Dundee observatory (Observatory's Wednesday Wonders) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact My team members were preset to explain diabetes and obesity and relevance to modern living, as well as indicating link to dementia. Attended by at least 50 people (mostly children - out of school summer clubs)
Year(s) Of Engagement Activity 2017
 
Description School visit 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact One of my PhD students presented a short description of our research and main findings as these relate to Diabetes and Dementia to a local primary school assemply - there was also a presentation of a cheque for diabetes-based research from the School to the Research unit at the University. There was some additional discussion with a small group of senior pupils and staff about research into diabetes and dementia, more generally. The school has asked for a copy of our Newsletter as a follow-up to this visit.
Year(s) Of Engagement Activity 2016
 
Description School visit (Dundee) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Primary school visit (32 pupils and 1 teacher). My PhD student, along with 2 others visited the class to talk about research activities in the areas of diabetes, cancer and Alzheimer's, with games played to try to explain the basic science
Year(s) Of Engagement Activity 2018