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Title: The modulation of insulin-sensitivity: a cell-based model approach
Author: Gillings, Annette Susan
ISNI:       0000 0001 3500 2071
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2007
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Advances in the development ofnew therapeutics for the treatment oftype 2 diabetes have been hampered by a lack of complete understanding of the events involved in ' insulin-stimulated glucose uptake and the aberrant processes involved in insulin resistance, due in part to a lack of suitable cell-based models of all the insulinsensitive peripheral tissues involved. This study aimed' to characterise immortal muscle cell-lines and investigate the mechanisms involved in the modulation of insulin-sensitivity. Key components of the insulin signalling pathway were found to be. expressed in differentiated H-2Kb-tsA58 myotubes and HL-1 cardiomYocytes. Despite this, both cell-lines were found to be relatively insensitive to the effects of insulin in terms of increases in glucose uptake and GLUT4 translocation to the plasma membrane. In addition, H-2Kb-tsA58 myotubes exhibited high levels of basal glucose uptake, which may have resulted fro~ aberrant signalling through phosphatidylinositol 3;.kinase (pI3K). HL-1' cells showed consistent and significant increases in glucose uptake and GLUT4 translocation in response to insulin, but unphysiologically high doses of insulin were required to elicit this response. Treatment of HL-1 cardiomyocytes with TNF-a, a potential contributor of the pathogenic effects of obesity, resulted in significant decreases in insulin-stimulated glucose uptake and GLUT4 translocation. In addition, 96-well plate screening assays for the identification of.compounds able to alleviate the TNF-a induced insulin resistance in both 3T3-L1 adipocytes and HL-1 cardiomyocytes were developed. Exploitation of mechanisms enabling insulin-independent glucose uptake is another approach for the development of novel antidiabetic therapeutics. Inhibition or deletion of the voltage-gated potassium channel Kv1.3 has been reported to increase insulin-sensitivity, via a mechanism found to be independent from PI3K activity. The present study aimed to further investigate the link between Kvl.3 channels and insulin sensitivity in primary and cultured cells. Kvl.3 was not found to be expressed in·3T3-L1 adipocytes or HL-1 cardiomyocytes, whereas, expressiOIi was observed in primary rat adipocytes and cardiomyocytes arid in the H-2Kb-tsA58 skeletal muscle cell-line. Despite confIrmation that selected Kv1.3 inhibitors were .active against human Kv1.3, these present studies have shown minimal direct effects of these inhibitors on insulin-sensitivity, glucose uptake or GLUT4 translocation, within the limits of currently available cell-based models of insulin-sensitive tissues.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available