REVing-down: targeting the circadian clock in metabolic disease

Lead Research Organisation: University of Manchester
Department Name: Life Sciences

Abstract

Obesity and diabetes are major threats to public health, and the incidence of both conditions continues to rise. Non-surgical intervention strategies including lifestyle modification are generally ineffective due to poor compliance, and current pharmacological options are plagued by poor efficacy and adverse side effects. Novel strategies and therapeutic targets are needed. Human and animal studies have shown that adipose tissue inflammation is driving factor in the progress of obesity to life-threatening conditions, such as diabetes and cardiovascular disease. White adipose tissue (WAT) is an essential energy buffer, balancing energy storage and release during natural cycles of fasting and feeding. Chronic positive energy balance leads to expansion (hypertrophy) of the tissue, and this state can result in adipocyte dysfunction. Consequential to WAT hypertrophy there is a major shift in the immune system within the adipose tissue; where immune cells which are normally beneficial to adipocyte function (eg iNKT and ILC2 cells) are replaced by pro-inflammatory immune cells, such as inflammatory monocytes and macrophages. It is this inflammatory state which perpetuates WAT dysfunction, and drives dyslipidaemia, insulin resistance and adipocyte cell death. The challenge is to identify events that signal the transition from normal 'healthy' fat storage to adipose dysfunction and inflammation.

We have recently demonstrated in mice that lack of the protein REVERBa predisposes to efficient adipocyte function and resulting WAT hypertrophy. Strikingly, although fat mass is increased they do not show the expected reduced insulin sensitivity or high levels of adipose tissue inflammation normally associated hypertrophic adipose tissue. The mice also show an elevated production of adiponectin - a hormone produced by healthy adipose tissue, and known to have many beneficial metabolic effects in humans. This indicates that REVERBa plays an important role in the adaption of WAT during obesity. In this project, we want to understand how REVERBa controls WAT function, and in particular elucidate how REVERB acting in adipocytes, regulates WAT immune function to attenuate obesity-related inflammation and insulin resistance.

To achieve this, we will use novel genetic targeting in mice to manipulate REVERBa expression and activity specifically in adipocytes. This will allow us to define how REVERBa drives adipocyte function under normal circumstances and during obesity to promote/attenuate the development of tissue inflammation and insulin-resistance. We will also define mechanisms though which REVERBa controls adiponectin production (a valuable therapeutic target).

Exploiting this unique model, we will next characterize how immune cell dynamics differ between mice that develop obesity related inflammation and insulin resistance, with those that remain insulin-sensitive in the face of obesity. Using state-of-the-art imaging, cell sorting and genomic techniques, we will not only identify and quantify immune populations, but also determine their relative state of activation. This is important as it goes beyond the immediate impact of REVERBa to identify cells/events that signal more broadly, the development of WAT dysfunction.

Alongside animal models, we will similarly define adipose-immune dynamics in visceral adipose collected from obese patients undergoing bariatric surgery and normal weight controls. This will determine which cells and events are common in the progression of obese WAT to an inflamed insulin-resistant state in both humans and mice. Importantly, we will determine whether target pathways are amenable to pharmacological manipulation in human WAT using drugs that increase or decrease REVERBa activity. The parallel nature of these studies will allow important pathways to be cross validated between human and mouse tissues, and greatly increase our ability to identify new strategies in the fight against obesity-related disease.

Technical Summary

In obesity, white adipose tissue (WAT) hypertrophy is associated with a shift in local immune cell populations, with displacement of beneficial cells by pro-inflammatory immune cells (eg M1 macrophages). From human and animal studies, we know that this inflammatory state drives WAT dysfunction, dyslipidaemia, and insulin resistance. What remain unclear are the events that signal the transition from efficient fat storage to WAT dysfunction and inflammation.

REVERBa-/- mice are profoundly obese; yet do not exhibit loss of insulin sensitivity or exacerbation of WAT inflammation. A role for REVERBa in lipid metabolism and within the immune system is already well established. REVERB typically inhibits macrophage inflammatory response. This led us to hypothesise that loss of REVERBa in adipocytes circumvents inappropriate programs of lipolysis and adipocyte stress which normally accompany WAT hypertrophy, and signals a selective preservation of distinct immune cell populations in the tissue (M2 macrophages, iNKT and ILC2 cells) even amid pronounced obesity.

To test these hypotheses, we will:
- Selectively delete REVERBa, or its DNA-binding domain (thereby segregating REVERBa control over metabolic and inflammatory processes) in adipocytes, and define the consequences of obesity in the mice.
- Identify, isolate and phenotype WAT immune populations during the development of obesity in normal (inflamed/insulin resistant) and transgenic (insulin sensitive) mice.

We will similarly define immune populations in WAT of obese and normal weight patients, to reveal common cells and events that define the inflamed insulin-resistant WAT in humans and mice, and use pharmacological manipulation of REVERBa to validate candidate pathways in cultured WAT. These studies will bring new understanding of WAT function and identify new strategies in the fight against obesity-related diseases.

Planned Impact

The research questions posed within this proposal are of major interest to ACADEMIC GROUPINGS in Biological, BioMedical, and Clinical Sciences. The academic community will benefit from elucidation of mechanisms involved in energy homeostasis, adipose tissue function, inflammation and obesity-related pathology. Understanding these pathways and identifying potential targets for intervention in obesity presents clear implication to human health and welfare. As such, research findings will impact greatly on the HEALTH CARE COMMUNITY. We will disseminate findings by publishing primary papers and reviews in high impact journals, and presenting work at national and international meetings. We anticipate that the proposed work will produce 2-4 high-quality primary research papers.

Our findings will be of interest to the GENERAL PUBLIC due to the prevalence of obesity and diabetes. At its most basic, the work will engage sections of the populous who wish to learn about their health and human physiology. This work also has potential to inform the general public about the pathogenesis of obesity and diabetes. Research findings will be delivered to the general public through public engagement activities (e.g. brain awareness week), as well as through mass media. For example, our recent article in Curr Biol was reported widely in national and international newspapers, on local radio, and on the internet.

The proposed research is of interest to PHARMACEUTICAL COMPANIES due to direct implications for human metabolic disease. Pharmaceutical industry investment into circadian biology is rapidly growing due to the fact that circadian dysfunction has been linked to sleep disorders, mental health disorders, cancer, inflammation, and aging. In the context of "building partnerships to enhance take-up and impact, thereby contributing to the economic competitiveness of the United Kingdom", our laboratories are currently involved in collaborations with Pfizer and GSK on circadian-related projects, and regular communication with these companies will ensure research findings are taken-up by and impact upon industrial beneficiaries. The REV-ERB compounds to be used are provided through collaboration with GSK, and thus demonstrate directly stakeholder interest. UoM has taken a strong proactive role in developing links with major pharmaceutical companies, as well as identification and development of commercialisation opportunities.

Benefits of this research to the UK ECONOMY are not guaranteed. However, metabolic disorders (obesity, cardiovascular disease, diabetes etc) are, and will continue to be, a massive burden on the national health care service. This will only increase with the aging population, in which circadian and metabolic disturbance is common. Thus, future economic benefits may be substantial.

This proposal also offers a unique and significant opportunity for high level in vivo training of the associated post-doctoral scientist, and any PhD students joining for related work. This is a significant benefit as a lack of in vivo research training has been highlighted as a weakness in UK bioscience. Numerous undergraduate and Master's degree students will be exposed to my research and gain valuable research skills through lab based projects.

Although beyond the limits of this grant, our ultimate goal is to deliver novel therapies which have real benefit for patients. Patients suffering with the associated co-morbidities of obesity, including type II diabetes urgently require new thinking to inform treatment development. Within the proposal, there are numerous pathways where therapeutic interest is already clear (e.g. adiponectin production, macrophage polarisation, WAT inflammation). Nevertheless, by incorporating non-biased and targeted approaches, mouse and human models, and adipose in different pathological states, this work is almost certain to identify novel and robust targets.
 
Description Bioinformatics research collaboration 
Organisation Qiagen
Country Netherlands 
Sector Private 
PI Contribution We have providing access to comics data sets.
Collaborator Contribution Qiagen is providing access to propriety aspects of their analysis platform IPA (Ingenuity Pathway Analysis) and scientific expertise in statistic and bioinformatics
Impact none yet
Start Year 2018
 
Description Research partnership with Pfizer 
Organisation Pfizer Global R & D
Country United States 
Sector Private 
PI Contribution My research team undertook research funded by Pfizer Global R&D. We undertook the experiments (rescuing rhythms in disrupted circadian clock models, visualisation of peripheral clock rhythms, and modulation of metabolic/cardiac outcomes).
Collaborator Contribution Pfizer Global R&D funded the project and supplied small molecule modulators of the circadian clock for the work.
Impact No outcome yet. Manuscript is being prepared.
Start Year 2017
 
Description Conference presentation (EBRS, Amsterdam) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact This was a conference presentation to scientists and postgraduate students in the circadian field. The presentation sparked questions and debate.
Year(s) Of Engagement Activity 2017
 
Description Conference presentation by a PhD student 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact My PhD student presented work derived from our research on obesity, adipose tissue function and reverbalpha to an international audience. There were questions and debate after the presentation.
Year(s) Of Engagement Activity 2017
 
Description Federation of Nutritional Societies of Europe (FENS) annual conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Major conference for nutritional science. The audience included academics, clinicians, food industry leaders, and students. My session discussed chrononutrition specifically and lead to discussion and debate.
Year(s) Of Engagement Activity 2019
 
Description National (PhysSoc) conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact A seminar presentation in a sponsored Physiological Society meeting in Manchester, UK. There were questions and debate after the talk.
Year(s) Of Engagement Activity 2017
 
Description School Visit (Manchester) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact This was a talk to 3 secondary schools in our local area (approx 40 students and teachers attended from the 3 schools). The primary goal was to inform the students about the circadian clock and research in my lab. There was a great deal of discussion and the students were very engaged. The feedback on the day was very good.
Year(s) Of Engagement Activity 2018