EMRAMIR · Extracellular Matrix Remodeling and Muscle Insulin Resistance: Role of Hyaluronan-CD44 Interaction

Extracellular Matrix Remodeling and Muscle Insulin Resistance: Role of Hyaluronan-CD44 Interaction

Skeletal muscle insulin resistance is a hallmark of Type 2 Diabetes and its associated metabolic disorders (1). Proteins and molecules (e.g. collagens and hyaluronan) outside the muscle cells accumulate in insulin resistance and vascular glucose and insulin delivery through the extracellular matrix (ECM) is a major barrier to muscle glucose uptake in insulin resistance (2-6). The overall objective of the project is to study specifically the muscle ECM component hyaluronan and its interaction with receptor CD44 in regulating muscle insulin resistance and test the role of endothelial dysfunction in the sequelae. Our previous studies have demonstrated that ECM hyaluronan content is increased in the skeletal muscle of insulin-resistant mice and normalisation of hyaluronan in the muscle by long-acting pegylated human recombinant PH-20 hyaluronidase (PEGPH20) reverses high-fat diet-induced muscle insulin resistance (7). The current project follows up on these promising results and further demonstrates that CD44, the main cell surface receptor for hyaluronan may be associated with the action of hyaluronan accumulation leading to insulin resistance. We found that genetic deletion of CD44 did not affect insulin sensitivity in mice during low fat diet feeding, but improved muscle insulin resistance on a high fat diet. In vivo insulin sensitivity was measured in chronically catheterised conscious mice by the hyperinsulinaemic-euglycaemic clamp. We are currently characterising the underlying mechanisms including the measurements of muscle insulin signalling, muscle capillarization and muscle ECM deposition. Our preliminary data have suggested that increased insulin signalling and capillarization in the muscle may contribute to improved muscle insulin resistance in high fat-fed CD44 null mice. Due to limited funding for consumables and animal costs, unfortunately we were unable to take these studies any further. However, these current studies have provided a strong foundation and promising preliminary data for subsequent funding applications. The current project has created a functional link between hyaluronan and CD44 interaction in the regulation of muscle insulin resistance. We have now obtained funding to further study whether CD44 on the endothelium is the main receptor responsible for the relationship. Apart from the research on hyaluronan and CD44, Dr Kang has continued, collaborated and provided research effort in the following areas: 1) role of muscle integrin linked kinase in skeletal muscle metabolic regulation during high fat diet feeding in mice, 2) role of adipose ECM remodelling in insulin resistance, 3) association of cardiac ECM deposition and capillarization with impaired insulin-stimulated glucose utilization in the heart, and 4) role of integrin β2 in maintaining glucose homeostasis in high fat-fed insulin-resistant mice. Dr Kang has gained a wide range of knowledge and developed valuable collaborations through these projects with the results either published in refereed journals or presented at scientific conferences. The prestigious International Incoming Fellowship has allowed Dr Kang to relocate from Vanderbilt University in the United States to University of Dundee to establish her own research group. Under the close supervision of Professors Ashford and McCrimmon, Dr Kang’s group is growing and has attracted major funding to support her research in the field of ECM remodelling in insulin resistance. Dr Kang together with Professors Ashford and McCrimmon and Dr Faisel Khan have just recently been awarded a research project grant from Diabetes UK, one of the major charity organisations in supporting Diabetes research. This award is developed based on the current Marie Curie Fellowship project and is the next phase of the work. In the past two years, Dr Kang continued and extended her national and international collaborations. Dr Kang has been selected to participate two networking programmes for outstanding young scientists, Scottish Crucible from the Royal Society of Edinburgh and Innovators in Diabetes from Diabetes UK. Both programmes are highly competitive and have allowed Dr Kang to form new collaborations and network with other scientists at similar-stage as well as senior scientists in her field and from multiple disciplines such as arts and engineering. These programmes have also inspired Dr Kang to think creatively and innovatively about her own research aims and projects. Type 2 Diabetes is now one of the major health disorders affecting western and developing societies and is associated with significant impacts on individual well-being and economic cost to society. Current therapeutic options are limited because of an incomplete understanding of the underlying pathophysiology. The current work suggests that a high caloric intake leads to a previously unrecognised change in the physical structure of the environment surrounding muscle cells, e.g. hyaluronan. This in turn reduces the ability of muscle cells to respond to insulin and contributes to the symptoms and complications of diabetes. Our findings could open up a new area of research in Type 2 Diabetes and offer the potential for the development of novel therapies, such as PEGPH20. REFERENCES 1. DeFronzo, R. A. (1992) Pathogenesis of type 2 (non-insulin dependent) diabetes mellitus: a balanced overview. Diabetologia 35, 389-397 2. Ayala, J. E., Bracy, D. P., Julien, B. M., Rottman, J. N., Fueger, P. T., and Wasserman, D. H. (2007) Chronic treatment with sildenafil improves energy balance and insulin action in high fat-fed conscious mice. Diabetes 56, 1025-1033 3. Fueger, P. T., Hess, H. S., Bracy, D. P., Pencek, R. R., Posey, K. A., Charron, M. J., and Wasserman, D. H. (2004) Regulation of insulin-stimulated muscle glucose uptake in the conscious mouse: role of glucose transport is dependent on glucose phosphorylation capacity. Endocrinology 145, 4912-4916 4. Fueger, P. T., Bracy, D. P., Malabanan, C. M., Pencek, R. R., Granner, D. K., and Wasserman, D. H. (2004) Hexokinase II overexpression improves exercise-stimulated but not insulin-stimulated muscle glucose uptake in high-fat-fed C57BL/6J mice. Diabetes 53, 306-314 5. Halseth, A. E., Bracy, D. P., and Wasserman, D. H. (1998) Limitations to exercise- and maximal insulin-stimulated muscle glucose uptake. J Appl Physiol 85, 2305-2313 6. Halseth, A. E., Bracy, D. P., and Wasserman, D. H. (2000) Limitations to basal and insulin-stimulated skeletal muscle glucose uptake in the high-fat-fed rat. Am J Physiol Endocrinol Metab 279, E1064-1071 7. Kang, L., Lantier, L., Kennedy, A., Bonner, J. S., Mayes, W. H., Bracy, D. P., Bookbinder, L. H., Hasty, A. H., Thompson, C. B., and Wasserman, D. H. (2013) Hyaluronan accumulates with high-fat feeding and contributes to insulin resistance. Diabetes 62, 1888-1896

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