Evaluation of Rgs7 as a key regulator of adipocyte function
Lead Research Organisation:
University of Warwick
Department Name: Warwick Medical School
Abstract
Excessive fat storage results from an imbalance between energy intake and energy expenditure. Mammals store excess energy in the form of fat, predominantly in adipocytes. Research over the past 15 years has transformed our view of adipose tissue from a fat-storage depot to an active, multi-hormone producing organ that communicates with a myriad of other tissues including muscle, liver, pancreas, heart, and the brain. Although the majority of fat is normally stored in white adipose tissue, another specialised type of adipose tissue known as brown adipose tissue exists which can convert fat into heat at a very high rate. The ability of brown adipose tissue to effectively burn fat means that it could prove highly effective for treating obesity if fully activated. Although it has recently been demonstrated that most adult humans possess brown adipose tissue it appears to be largely inactive in most individuals under normal conditions. To use brown fat to treat obesity we need to understand more fully the molecules and pathways that control its activation. In this project, we will look at the role of a factor that could have essential actions in controlling the hormonal pathways that affect brown fat activity, energy balance and the conversion of white to brown fat.
Brown fat cells express a unique set of genes that determine the fundamental differences between brown and white fat cells. Rgs7 (Regulator of G protein signalling 7) is a gene that we found was present at high levels in brown fat cells. Furthermore, it was increased in white fat upon prolonged cold exposure, a treatment which induces the appearance of brown fat cells within white fat depots. Importantly, genetic analysis has revealed the RGS7 gene is associated with obesity and diabetes in humans. Rgs7 controls the activity of hormone signalling pathways in cells. As these pathways are essential for the gene regulation required for brown and white fat function, regulators such as Rgs7 are likely to have a vital role in the physiology of fat and the control of energy balance. We will investigate, for the first time, the role of Rgs7 in whole body energy metabolism and fat cell biology by addressing its effects on brown fat activation due to cold exposure and susceptibility to obesity due to high fat diet. We will study how hormone receptor pathways are modulated by Rgs7 in fat cells and how the metabolic function of the cell is affected.
This project proposal to study the metabolic role of Rgs7 is timely given the nature of the obesity epidemic, identification of functional human brown fat as a weight loss target, and our recent study that identified it among genes specifically expressed in brown fat. As obesity and associated metabolic diseases are an increasing health concern the fundamental questions to be addressed in this proposal closely align with the BBSRC's strategic aim to increase understanding of the biology of normal healthy ageing, to improve lifelong health and wellbeing. The targeting of Rgs7 represents a novel approach to modulate receptor-mediated signalling pathways that regulate processes for controlling energy balance. Increasing energy dissipation through signal transduction modulation in adipose tissues has the potential to promote weight loss to assist in treating and preventing metabolic diseases.
Brown fat cells express a unique set of genes that determine the fundamental differences between brown and white fat cells. Rgs7 (Regulator of G protein signalling 7) is a gene that we found was present at high levels in brown fat cells. Furthermore, it was increased in white fat upon prolonged cold exposure, a treatment which induces the appearance of brown fat cells within white fat depots. Importantly, genetic analysis has revealed the RGS7 gene is associated with obesity and diabetes in humans. Rgs7 controls the activity of hormone signalling pathways in cells. As these pathways are essential for the gene regulation required for brown and white fat function, regulators such as Rgs7 are likely to have a vital role in the physiology of fat and the control of energy balance. We will investigate, for the first time, the role of Rgs7 in whole body energy metabolism and fat cell biology by addressing its effects on brown fat activation due to cold exposure and susceptibility to obesity due to high fat diet. We will study how hormone receptor pathways are modulated by Rgs7 in fat cells and how the metabolic function of the cell is affected.
This project proposal to study the metabolic role of Rgs7 is timely given the nature of the obesity epidemic, identification of functional human brown fat as a weight loss target, and our recent study that identified it among genes specifically expressed in brown fat. As obesity and associated metabolic diseases are an increasing health concern the fundamental questions to be addressed in this proposal closely align with the BBSRC's strategic aim to increase understanding of the biology of normal healthy ageing, to improve lifelong health and wellbeing. The targeting of Rgs7 represents a novel approach to modulate receptor-mediated signalling pathways that regulate processes for controlling energy balance. Increasing energy dissipation through signal transduction modulation in adipose tissues has the potential to promote weight loss to assist in treating and preventing metabolic diseases.
Technical Summary
Receptor-mediated signal transduction pathways control essential metabolic processes that modulate whole body energy balance. We have discovered that the gene Regulator of G protein Signalling 7 (Rgs7) is highly expressed in BAT and is induced during the "browning" of WAT by cold exposure. RGS proteins determine the duration of signalling downstream of G protein-coupled receptor (GPCR) activation. As GPCRs serve essential actions in adipocytes including the stimulation of processes such as thermogenesis and lipolysis, Rgs7 has the potential to affect these key G protein-controlled pathways to control adipocyte metabolism.
With increasing rates of obesity and the associated diseases of type 2 diabetes and cardiovascular heart disease, it is important to identify novel approaches to improve metabolic health. Brown adipose tissue (BAT) is recognized as a target to combat obesity and diabetes due to the re-discovery of functional BAT in adult humans and its ability to burn fat and therefore aid weight loss. Adipocytes can be subdivided into two distinct categories; brown adipocytes dissipate energy in the form of heat whereas white adipocytes are specialized in the storage of chemical energy in white adipose tissue (WAT). Adipose tissues are remarkably dynamic in nature and stimuli such as prolonged cold exposure results in the presence of brown adipocytes within WAT depots.
We will determine the pathways that are modulated by Rgs7 in adipocytes and the functional consequences of its actions. The role of Rgs7 in whole body metabolism will be investigated and its actions in brown fat responses to cold exposure and weight gain due to high fat feeding. Rgs7 represents a novel target to modulate the processes that control energy balance. Increasing energy dissipation through signal transduction modulation in adipose tissues has the potential to promote weight loss to assist in treating and preventing metabolic diseases.
With increasing rates of obesity and the associated diseases of type 2 diabetes and cardiovascular heart disease, it is important to identify novel approaches to improve metabolic health. Brown adipose tissue (BAT) is recognized as a target to combat obesity and diabetes due to the re-discovery of functional BAT in adult humans and its ability to burn fat and therefore aid weight loss. Adipocytes can be subdivided into two distinct categories; brown adipocytes dissipate energy in the form of heat whereas white adipocytes are specialized in the storage of chemical energy in white adipose tissue (WAT). Adipose tissues are remarkably dynamic in nature and stimuli such as prolonged cold exposure results in the presence of brown adipocytes within WAT depots.
We will determine the pathways that are modulated by Rgs7 in adipocytes and the functional consequences of its actions. The role of Rgs7 in whole body metabolism will be investigated and its actions in brown fat responses to cold exposure and weight gain due to high fat feeding. Rgs7 represents a novel target to modulate the processes that control energy balance. Increasing energy dissipation through signal transduction modulation in adipose tissues has the potential to promote weight loss to assist in treating and preventing metabolic diseases.
Planned Impact
The impact of this research program will come from the advancement of knowledge of the molecular mechanisms that control energy homeostasis. This will have a major impact for diverse groups and applications in six main ways:
1-Basic research underpinning health:
The proposed research has potential implications in the field of metabolic wellbeing that could contribute to enhance the quality of life and nation's health. New basic science findings in the signalling mechanisms that affect energy storage are of great interest to this sector. This project will provide new understanding of the signalling pathways that control activation of brown and white adipose tissue. There is a link between absence of detectable brown adipose tissue and obesity. The direct costs to the NHS and other health care providers for treating obesity and related conditions is currently around £10 billion per year (approx. 10% of the NHS budget). Because elevated fat storage in diseases such as obesity and fatty liver disease is linked with increased risk of diabetes, high blood pressure, heart disease and certain cancers, this work will be of importance to the health sector and to the general public, either from a general science education benefit, or for those who are directly impacted by these diseases.
2-Innovative healthcare solutions:
The ability to regulate energy balance has implications not only relevant to obesity, but also to clinical applications associated with weight loss in providing new approaches to treat metabolic disorders including lipodystrophy and cancer cachexia.
3-Biotechnology:
Identification of the molecular role of Rgs7 in adipocytes will be of great interest to the pharmaceutical industry due to the potential for fine-tuning signal transduction pathways or modulating ligand bias to regulate drug action and control which pathways are switched on or off.
4-Education and training:
The bioscience research carried out in the proposed project will contribute towards maintaining the high standard of academic excellence currently enjoyed by the University of Warwick and Cambridge University. This will impact on the ability to offer educational opportunities for undergraduate and post-graduate student training. This is a multidisciplinary project involving groups with renowned expertise in adipocyte biology, in vivo metabolism, cell signalling, gene regulation, bioinformatics, and systems biology. The interactions between researcher partners will facilitate transferable professional, analytical and communication skills, as well as specific scientific and technical skills that will contribute to their development and future prospects.
5-UK international competitiveness:
This research program will contribute to deliver the BBSRC's mission especially the strategic research priority 3 - Bioscience for Health as well as supporting the general UK strategy for combating increased incidence in obesity.
6-Science communication:
The conceptual advances and material (e.g. pictures and illustrations) generated to present the results of the proposed research will add to the resources used during outreach activities such as school open days and available for visitors to Warwick Medical School. We will raise awareness of the latest advances in the fields of metabolic medicine amongst diverse audiences within the general public and to educate and inspire interest in scientific careers in secondary school students. The pathway towards academic impact will be based on the classical instruments of scientific communication. Publication of our results in peer reviewed journals and presentations at international scientific meetings of relevance to the field will be the preferred means of communicating our results and conclusions.
1-Basic research underpinning health:
The proposed research has potential implications in the field of metabolic wellbeing that could contribute to enhance the quality of life and nation's health. New basic science findings in the signalling mechanisms that affect energy storage are of great interest to this sector. This project will provide new understanding of the signalling pathways that control activation of brown and white adipose tissue. There is a link between absence of detectable brown adipose tissue and obesity. The direct costs to the NHS and other health care providers for treating obesity and related conditions is currently around £10 billion per year (approx. 10% of the NHS budget). Because elevated fat storage in diseases such as obesity and fatty liver disease is linked with increased risk of diabetes, high blood pressure, heart disease and certain cancers, this work will be of importance to the health sector and to the general public, either from a general science education benefit, or for those who are directly impacted by these diseases.
2-Innovative healthcare solutions:
The ability to regulate energy balance has implications not only relevant to obesity, but also to clinical applications associated with weight loss in providing new approaches to treat metabolic disorders including lipodystrophy and cancer cachexia.
3-Biotechnology:
Identification of the molecular role of Rgs7 in adipocytes will be of great interest to the pharmaceutical industry due to the potential for fine-tuning signal transduction pathways or modulating ligand bias to regulate drug action and control which pathways are switched on or off.
4-Education and training:
The bioscience research carried out in the proposed project will contribute towards maintaining the high standard of academic excellence currently enjoyed by the University of Warwick and Cambridge University. This will impact on the ability to offer educational opportunities for undergraduate and post-graduate student training. This is a multidisciplinary project involving groups with renowned expertise in adipocyte biology, in vivo metabolism, cell signalling, gene regulation, bioinformatics, and systems biology. The interactions between researcher partners will facilitate transferable professional, analytical and communication skills, as well as specific scientific and technical skills that will contribute to their development and future prospects.
5-UK international competitiveness:
This research program will contribute to deliver the BBSRC's mission especially the strategic research priority 3 - Bioscience for Health as well as supporting the general UK strategy for combating increased incidence in obesity.
6-Science communication:
The conceptual advances and material (e.g. pictures and illustrations) generated to present the results of the proposed research will add to the resources used during outreach activities such as school open days and available for visitors to Warwick Medical School. We will raise awareness of the latest advances in the fields of metabolic medicine amongst diverse audiences within the general public and to educate and inspire interest in scientific careers in secondary school students. The pathway towards academic impact will be based on the classical instruments of scientific communication. Publication of our results in peer reviewed journals and presentations at international scientific meetings of relevance to the field will be the preferred means of communicating our results and conclusions.
Publications
Christian M
(2020)
Elucidation of the roles of brown and brite fat genes: GPR120 is a modulator of brown adipose tissue function.
in Experimental physiology
Schilperoort M
(2018)
The GPR120 agonist TUG-891 promotes metabolic health by stimulating mitochondrial respiration in brown fat.
in EMBO molecular medicine
Wang Z
(2023)
Food phenolics stimulate adipocyte browning via regulating gut microecology.
in Critical reviews in food science and nutrition
| Description | Fat consumption in brown adipose tissue is activated by ligands that stimulate receptors present on adipocytes. Ligands in addition to activating cell surface receptors to affect signaling pathways also directly activates the protein UCP1 to increase energy consumption. Rgs7 is a key regulator of the g protein signaling pathway. Loss of Rgs7 is associated with lower body weight and fat mass. Analysis of Rgs7 knockout mice has revealed that lack of this gene results in lower body weight. This appears to be due to changes in the adipose tissue as the amounts of both brown and white (subcutaneous and visceral) adipose tissue are reduced. To determine the changes associated with reduced adipose tissue mass we have profiled the transcriptome in brown and white adipose tissues by RNAseq. This analysis has identified differences in response to cold in brown and white adipose tissue with ablation of Rgs7. Importantly, our analysis shows that brown and white adipose tissue, at the gene expression level, is activated in the absence of Rgs7 in male mice. However, although brown fat-associated gene expression is increased at thermoneutrality in Rgs7KO male mice the maximum thermogenic capacity is actually perturbed by ablation of the Rgs7 gene. In addition to this, we have investigated the role of Rgs7 in weight gain due to high fat diet. Rgs7KO male mice are protected from weight gain when exposed to a high fat diet (60% fat). Furthermore, the absence of Rgs7 enhances insulin sensitivity in males following exposure to high fat diet. Loss of Rgs7 enhances brown adipocyte responses We have assessed the role of Rgs7 in adipocyte differentiation and function. Loss of Rgs7 does not affect the process of adipogenesis. However, Rgs7 ablation results in increased expression of genes associated with brown fat function including UCP1 and CIDEA. Furthermore, stimulus with a b3-adrenergic agonist enhanced the expression of UCP1 and Gpr120 to a much greater extent in KO compared to wild type brown adipocytes. This is indicative that Rgs7 has a repressive function in brown fat gene expression. The role of Rgs7 in repressing brown fat genes is supported by cell metabolism analysis. We found that Rgs7 knockout brown adipocytes consumed more oxygen than wild type cells. Furthermore, b3-adrenergic stimulus increased oxygen consumption. In wild type cells this increase was more rapid than in knockout cells which showed a more progressive and sustained increase in oxygen consumption. Constitutive re-expression of Rgs7 in knockout brown adipocytes blocked b3-stimulated increases in oxygen consumption. These data reveal that Rgs7 is a key effector of b3-adrenergic signaling in brown adipocytes and is also supported by analysis of mouse tissues. The gene expression in Rgs7 knockout brown adipose tissue at thermoneutrality is similar that of wild type exposed to cold. This indicates that absence of Rgs7 in vivo leads to a constitutive activation of brown adipose tissue, likely through the b3-adrenergic pathway. We have investigated the subcellular localisation of Rgs7 in brown adipocytes using confocal microscopy. Surprisingly, Rgs7 seems to be both cytoplasmic and nuclear. Our hypothesis was that since Rgs7 regulates G protein signaling it would be present only in the cytoplasm, possibly with some localisation near the plasma membrane. However, the nuclear localisation indicates that it has additional molecular functions. A role for Rgs7 in processes outside GPCR signalling is supported by our Mass Spectrometry analysis of Rgs7-interacting proteins. This has revealed interactions with Tmed family members which have cell signaling and protein trafficking actions. Interaction was also found with DLC1. This protein has previously been reported to be essential for brown adipocyte function. Overall this investigation has determined that Rgs7 has a key role in regulating metabolic function of adipocytes. Absence of Rgs7 protects from weight gain on high fat diet and is associated with constitutive activation of brown adipocytes and the browning of white adipocytes. The data is now being prepared for publication. |
| Exploitation Route | Our project aims to advance fundamental understanding of how signaling pathway regulators affect adipose tissue biology and whole body energy metabolism with immediate relevance in metabolic health. This project thus fulfils the remit of UKRI's mission to support basic research underpinning health. Our cohesive research program contributes towards maintaining world class UK bioscience by supporting Systems and multidisciplinary approaches that will enable others to develop innovative ideas beyond their specific area of scientific expertise. To maximise the impact of our research we will continue to engage and disseminate information to stakeholders across the full spectrum of relevant activities: professionals (scientists, graduate, and undergraduate students), enthusiastic public (self-motivated lay enthusiasts) and, general public (without a regular interest in life sciences). Longer term strategies include small molecular targeting of Rgs7 to enhance brown fat function to promote weight loss and ligand development for treatment of obesity/diabetes. |
| Sectors | Healthcare,Pharmaceuticals and Medical Biotechnology |
| Description | UK economic competitiveness is facilitated by training and skills acquisition. The project has succeeded in providing an excellent training of the appointed Post Doc Federica Dimitri. She developed the molecular tools used in the study. The wide range of skills acquired from the project (e.g. time management, problem solving, information technology, presentation skills, record keeping, budgeting, innovative thinking and mentoring) are applicable to career progression both within and outside academia. Thus, Federica has benefitted as an individual from the training, and the sector where she applies his skills and training will benefit. Federica is continuing her scientific career in an industrial setting at Orbit Discover, Oxford. With this project, we have contributed to increasing awareness and understanding of science. This was undertaken through teaching and training of students. We have contributed to changing perceptions of brown adipose tissue, which is currently limited and increased understanding of the importance of brown fat in health. The international multidisciplinary collaboration network (UK-USA) established through this project has served to enhance the research capacity and skills base. The management skills involved in coordinating a multicentre collaboration are important on a personal development perspective and are applicable to economic advancement. The network has served to raise the profile of UK research with a group of influential scientists and policy makers within their different fields. The impact of COVID has led to new approaches to address research questions as well as resilience. |
| First Year Of Impact | 2021 |
| Sector | Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology |
| Impact Types | Economic |
| Title | Generation of Conditionally Immortalised Rgs7 knockout cell lines |
| Description | Cell lines were generated from brown adipose tissue, gonadal white adipose tissue and subcutaneous white adipose tissue. Both Rgs7 knockout and wild type cell lines were generated from the three adipose tissue depots. |
| Type Of Material | Cell line |
| Year Produced | 2018 |
| Provided To Others? | No |
| Impact | The application of these cell lines allows us to investigate the role of Rgs7 in adipocytes and serves to reduce the requirement of animals in this research path. |
| Description | In vivo and in vitro investigation of Rgs7 in metabolism |
| Organisation | Scripps Research Institute |
| Country | United States |
| Sector | Charity/Non Profit |
| PI Contribution | Expertise on metabolism and identification of importance of Rgs7 in brown adipose tissue |
| Collaborator Contribution | Kirill Martemyanov has provided Rgs7 KO mice that will be used to investigate the in vivo role of Rgs7 in metabolism. In addition primary cultures will be prepared to investigate in vitro cell autonomous actions of Rgs7. |
| Impact | There are no outputs as yet. The mice are currently being re-derived. |
| Start Year | 2017 |
| Description | In vivo metabolic phenotyping |
| Organisation | University of Cambridge |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Expertise in planning and concept of in vivo studies |
| Collaborator Contribution | Rgs7 KO mice are presently being re-derived in Cambridge to be taken into the Phenotyping unit where the experiments will be performed. |
| Impact | No impact yet |
| Start Year | 2017 |
| Description | Mass Spectrometry Identification of Rgs-interacting proteins |
| Organisation | Nottingham Trent University |
| Department | School of Science and Technology |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Epitope-tagged Rgs7 was expressed in brown adipocytes knockout for Rgs7. Protein was extracted from both knockout and Rgs-expressing cells. The proteins were bound to Ni-beads, washed and eluted. The eluted sample contained Rgs7 and interacting proteins which were provided for Mass Spectrometry Analysis. |
| Collaborator Contribution | David Boocock and his team processed the samples to identify proteins in brown adipocytes that interact with Rgs7. The mass spectrometry and data analysis were undertaken. |
| Impact | N/A |
| Start Year | 2020 |
| Description | Student Engagement Activity |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Postgraduate students |
| Results and Impact | The purpose was to introduce students to brown adipose tissue research with a specific focus on Rgs7. This was to raise the profile and interest in this area of research. Presentation of protocols used to investigate the role of Rgs7 in adipocytes and data analysis. This was to a group of Postgraduate students undergoing practical training. Students highly engaged and after the presentation we discussed one to one the importance of research in this area. It was clear that the presentation had impacted the students knowledge of the key functions of brown adipocytes. |
| Year(s) Of Engagement Activity | 2020,2021 |