Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.806668
Title: Cytoprotective effects of epoxyeicosatrienoic acids in pancreatic beta cells
Author: Grimes, Daniel
Awarding Body: Keele University
Current Institution: Keele University
Date of Award: 2020
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Abstract:
Pro-inflammatory cytokines and glucolipotoxicity are known mediators of beta cell death and dysfunction in the pathogenesis of type 1 and type 2 diabetes mellitus (DM). In contrast to the pro-apoptotic effects of long-chain saturated fatty acids in beta cells, mono- and poly- unsaturated species, including arachidonic acid (AA), are well-tolerated and can attenuate the effects of cytoxocity. AA-drived eicosanoids are well-studied in context to beta cell biology, with established contributions of cyclooxygenase (COX) and lipoxygenase (LOX) products in cytotoxicity studies, though comparatively less is known about the role of cytochrome P450-derived epoxyeicostrienoic acids (EETs) in this context, despite reported anti-inflammatory activity in other models. Therefore the aim of this thesis was to investigate the cytoprotective actions of EETs and their corresponding diol products of soluble epoxide hydrolase metabolism; dihydroxyeicosatrienoic acids (DHETs) in the rat pancreatic beta cell line BRIN-BD11. Preliminary investigations confirmed the cytotoxicity exerted by pro-inflammatory cytokines and palmtiate in reducing cell viability and increasing apoptosis. These effects were attenuated by co-incubation of 8(9)-EET, 11(12)-EET and 14(15)-EET isomers, a novel observation in a beta cell model. In contrast, DHETs failed to ameliorate palmitate toxicity however, 8(9)-DHET remarkably produced comparable effects to that of EETs against cytokine toxicity. These effects were associated with a reduction in cytokine-induced NF-κB activation and, in the case of EETs, decreased nitrite production. Futhermore, in these models EET effects were PPARγ-independent, with a wider range of PPAR and GPR antagonists failing to identify a single high affinity receptor site mediating EET actions against palmitate toxicity. Similarly, whilst alterations in gene expression of enzymes involved in palmitate oxidation and triglyceride synthesis were observed in repsonse to EET treatments, with a modest increase in intracellular lipid droplets, pharmacological inhibition of these pathways suggests these are not required in mediating EET actions. This was further supported by the attentuation of toxicity exerted with the poorly metabolisable palmitate analogue, 2-Bromopalmitate, by EETs. Therefore, whilst mechanisms of actions remain poorly defined, this thesis provides the first direct evidence for the cytoprotective actions of EETs and DHETs in a beta cell model, establishing a foundation for future work to explore the manipulation of endogenous EETs in pancreatic beta cells and to further define their mode of action in models of type 1 and 2 DM.
Supervisor: Watson, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.806668  DOI: Not available
Keywords: QH301 Biology
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