Leonard, Siobhan (2015) Therapeutic Approaches to Insulin Resistance and Type 2 Diabetes. PhD thesis, National University of Ireland Maynooth.
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Abstract
Type 2 diabetes is a chronic metabolic disorder primarily caused by a systemic insulin
resistant state to which obesity is a major contributor. Increasing visceral adipose tissue
augments adipokine secretion provoking an enduring low-grade inflammatory response
that negatively impacts on the insulin signalling cascade. In an intervention study of a
murine diet-induced model of type 2 diabetes, a novel compound, RTC-1, designed to
reduce serum levels of one such adipokine, RBP, improved glucose handling and
prevented weight gain. This compound also had a direct positive effect on glucose
uptake in vitro, independent of its predicted mode of action. Through cellular analysis
this study has established the mechanism by which this is achieved. RTC-1 was found
to inhibit complex I of the mitochondrial respiratory chain (NADH:ubiquinone
oxidoreductase), leading to a likely increase in the AMP to ATP ratio and the
consequential activation of the cellular energy regulator, AMPK. This in turn
stimulated the signalling pathway which enhanced the incorporation of the glucose
transporter, GLUT4, into the plasma membrane. RTC-1 was also found to prevent
adipogenesis and induced osteogenesis in an AMPK dependent manner. Additionally,
RTC-1 was observed to provoke an increase in insulin sensitivity.
In a separate project, the signalling capabilities of an orphan GPCR, GPR21, were
investigated. Knockout studies have suggested a role for this receptor in macrophage
infiltration into adipose tissue to augment insulin resistance through an unknown
mechanism. Overexpression studies revealed GPR21 to be a constitutively active
receptor, which couples Gαq type G proteins leading to the activation of the MAP
kinases. Overexpression of GPR21 markedly attenuated insulin signalling and
promoted macrophage migration. Interestingly, the effect of GPR21 on insulin
signalling lessened in the presence of increasing concentrations of serum, inferring the
possibility of a native regulatory ligand. Homology modelling and ligand docking
studies led to the identification of a novel compound that interacted with GPR21. Its
effects offered the potential as an anti-diabetic therapy as it was found to regulate
GPR21-induced macrophage migration and to counteract the influence of GPR21 on the
insulin signalling pathway.
Item Type: | Thesis (PhD) |
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Keywords: | Therapeutic Approaches; Insulin Resistance; Type 2 Diabetes; |
Academic Unit: | Faculty of Science and Engineering > Biology |
Item ID: | 10411 |
Depositing User: | IR eTheses |
Date Deposited: | 09 Jan 2019 10:07 |
URI: | https://mural.maynoothuniversity.ie/id/eprint/10411 |
Use Licence: | This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here |
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