Functional analysis and pathophysiology of glucose transporters

Lead Research Organisation: University of Bath
Department Name: Biology and Biochemistry

Abstract

The health problem of type 2 diabetes is now huge with approximately 3% of the UK population (1.4 million people) suffering from the disease. This was once considered an adult onset disease but now teenagers are developing the disease. Sugars are abundant components of diet but their abnormal disposal is associated with type 2 diabetes. Improved understanding of glucose disposal by key body tissues is therefore needed.
Diabetes is one of the major contributors to death from coronary heart disease. The uptake of sugars in heart is insulin stimulated but this process can be inhibited if the interior of the heart cells becomes too acidic. We plan to study the mechanism of heart cell pH maintenance and investigate the means by which this is linked to impaired glucose uptake and utilisation. Improved understanding will aid in the development of heart disease therapies.
The increasing prevalence of type 2 diabetes is thought to be in part related to poor diets, and in part due to lack of exercise. We plan to study these two inter-related problems by focussing part of our programme on the processes in heart and skeletal muscle that govern the exposure of glucose uptake protein to the cell surface. This exposure can be driven by both insulin and by changes in the cell energy level resulting from exercise. We plan to utilise newly developed tools and reagents to study how the latter pathway can lead to alleviation of the poor insulin-stimulated glucose disposal found in type 2 diabetic persons. Integrating these related aspects of our investigation in the key tissues of fat, heart and muscle should add to the understanding of the delicate balance between our dietary sugar needs and excesses and this should lead to improved therapies that rebalance body chemistry.

Technical Summary

Sugars are abundant components of diet but their abnormal disposal gives rise to diseases that include obesity and type 2 diabetes. Sugar disposal occurs via uptake into selective tissues that utilise specialised membrane tranporters or GLUTs. Recent genome analysis has indicated that the GLUT family of proteins includes some new un-characterised isoforms. We plan to examine the substrate specificity of the newly discovered GLUT8 and to analyse the extent to which it may rate limit sugar uptake in its target tissues. The extent to which GLUT8 contributes to glucose disposal will be examined by characterising GLUT8 in normal placenta and in placenta from animals which have been subjected to dietary and genetic modification. Such studies are relevant to dietary recommendations in diabetic pregnancies and the programming of adult onset syndrome X phenotypes.
In insulin responsive tissues GLUT4 distribution is particularly important for regulation of blood glucose levels. In type 2 diabetes, there is impaired insulin-stimulated GLUT4 recruitment from its intracellular storage compartment to the cell surface. We plan to investigate the role of cell pH maintenance in the subcellular movement of GLUT4. The localisation of cellular pH maintenance machinery will be examined. There will be emphasis on pH regulation in heart as the cell alkalinising and glucose disposal effects of insulin may be cardioprotective during ischemia. We plan to resolve the extent to which GLUT4 vesicle coating and fusion reactions are dependent on insulin?s action on pH and the extent to which the pH within GLUT4 vesicles is regulated..
In addition to insulin, the hypoxia/exercise pathway leads to stimulation of glucose transport in heart and skeletal muscle. We plan to examine GLUT4 trafficking kinetics, compartmentalisation and phosphorylation in response to these stimuli. We plan to examine the extent to which the hypoxia/exercise pathway can partially mimic and compensate for impaired insulin action on GLUT4 subcellular trafficking. These mechanisms will be studied in human muscle from healthy and type 2 diabetic persons.

Publications

10 25 50

 
Description Diabetes UK, Project Grant
Amount £143,425 (GBP)
Organisation Diabetes UK 
Sector Charity/Non Profit
Country United Kingdom
Start 06/2008 
End 07/2010
 
Description Wellcome Trust Project Grant (Convergence of insulin signalling and GLUT4 trafficking at a regulated membrane fusion step)
Amount £213,961 (GBP)
Funding ID 081168/Z/06/Z 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2007 
End 02/2010
 
Title Isotope tags on GTP photolabels 
Description C13 isotope tags on GTP photolabel. For use inproteomic analysis of GTP binding proteins 
Type Of Material Technology assay or reagent 
Year Produced 2013 
Provided To Others? Yes  
Impact Unpublished data 
 
Title Photochemical reagent for analysis of GLUT4 translocation 
Description We have developed a photoaffinity labelling reagent which can be used to study glucose transporters at the surface of cells. We have used it to determine the extent to which the glucose transporter GLUT4 is translocated in response to insulin and how this process is impaired in type 2 diabetes 
Type Of Material Technology assay or reagent 
Year Produced 2006 
Provided To Others? Yes  
Impact Used with clinical samples including muscle from type 2 diabetes patients. This was a collaborative study with a group at the Karolinska Institute, Stockholm, Sweden 
 
Title Photolabel for GTP binding proteins 
Description A GTP analogue that can detect the activation of GTP-binding proteins. This is being used to detect the activation of GTPase (mainly of the Rab family) that are relevant to insulin action in insulin responsive tissues such as adipose, heart and skeletal muscle 
Type Of Material Technology assay or reagent 
Year Produced 2012 
Provided To Others? Yes  
Impact Patent 
 
Description Breakfast project 
Organisation University of Bath
Department School of Health Bath
Country United Kingdom 
Sector Academic/University 
PI Contribution Setting up assays for determining insulin sensitivity in adipose tissue
Collaborator Contribution Application of insulin sensitivity assays to human subjects under varying fasting regimes
Impact Publication in Trials
Start Year 2009
 
Description CASE1 
Organisation AstraZeneca
Country United Kingdom 
Sector Private 
PI Contribution Setting up of assays for measuring GLUT4 translocation in a muscle cell line
Collaborator Contribution shared expertise
Impact Publication ID 19915010
Start Year 2006
 
Description Diabetes Institute, Dusseldorf 
Organisation University Hospital Düsseldorf
Department German Diabetes Center
Country Germany 
Sector Academic/University 
PI Contribution Generation of a new reagent for labelling the substrates of TBC1D1 and TBC1D4. These proteins are Rab GAPs
Collaborator Contribution Collaboratively we are studying the GTPase labelling in knockout animals with deletions in TBC1D1 and TBC1D4 that have been generated by the Dr Hadi Al Hasani at the German Diabetes Center
Impact Unpublished data Sabbatical visit to the German Diabetes Centre in 2013 sponsored by DAAD
Start Year 2011
 
Description Proteomics of insulin action on GLUT4 
Organisation The Garvan Institute for Medical Research
Country Australia 
Sector Hospitals 
PI Contribution Supply of material for analysis
Collaborator Contribution Proteomic analysis
Impact New data
Start Year 2012
 
Title Reagent 
Description Reagent for binding to activated form of GTPases 
IP Reference WO2012049464 
Protection Patent application published
Year Protection Granted 2012
Licensed No
Impact Collaborative research with German Diabetes Center, Dusseldorf has been initiated
 
Description Presentation at fundraisers meeting of Diabetes UK 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact about 30 Diabetes UK fundraisers attended

Discussions with audience and group occurred after presentation
Year(s) Of Engagement Activity 2010
 
Description Web site 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact General account of activities of our research on a web site that is publically accessible

Contacts from lay public
Year(s) Of Engagement Activity 2006,2007,2008,2009,2010