Novel mechanisms of glucolipotoxic pancreatic beta cell death

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Hanna, K, 2018. Novel mechanisms of glucolipotoxic pancreatic beta cell death. PhD, Nottingham Trent University.

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Abstract

Glucolipotoxicity (GLT) is the term given to the combined and damaging effect of increased glucose and fatty acid levels on pancreatic beta cells (β-cells) (Poitout et al, 2010). There is mounting evidence that glucolipotoxicity is the cause of the decline in β-cell function found in type 2 diabetes (T2D). T2D is a chronic metabolic disorder characterised by sustained elevated blood glucose and free fatty acids, with a continuously increasing prevalence (Olokoba et al, 2012). It is estimated 415 million people currently are living with diabetes and 193 million are undiagnosed, of those 90% are T2D cases. (chatterjee et al, 2017).

There are multiple aims in this thesis including the identification of GLT-induced inflammatory pathways of the pancreatic β-cell resulting from NF-κB activation. To identify novel transcription factors associated with GLT-induced reduction in insulin secretion and insulin gene expression and whether their expression is associated with the presence CD40. To observe whether the addition of carnosine to cultured cells can prevent/reverse the up-regulation in GLT-induced factors which potentially result in β-cell damage. Finally, to observed whether GLT can induce histone modifications resulting from disruption in the TCA cycle.

To mimic GLT conditions INS-1 rat pancreatic β-cells were cultured in media supplemented with 28mM glucose, 200µM palmitic acid and 200µM oleic acid. The results showed following 5-day incubation ±GLT, there was an increase in TNF receptor CD40 and a CD40-dependent increase in NF-κB. Further to this exposure of INS-1 cells to GLT conditions resulted in a 3.7-fold increase in iNOS mRNA and increased 4-HNE and 3-NT adduct formation (43.4% and 33% respectively) indicating potential GLT-induced β-cell damage. The addition of 10mM carnosine was able to prevent/reverse the up-regulation of GLT-induced NF-κB activity, iNOS protein expression and 4-HNE and 3-NT adduction, identifying it as a potential therapeutic strategy for T2D.

GLT-induced up-regulation of CD40 is also shown to be involved in the modulation of various genes, including insulin. siRNA down-regulation of CD40 resulted in increased insulin gene expression via modulation of ID4. Independent of CD40, a protein usually associated with MODY is observed. GLT results in 33.3% down-regulation of HNF4α, which has a knock-on effect on Rab protein expression resulting in down-regulation of insulin secretion. There by indicating that HNF4α is important in normal insulin secretion.

This research found that GLT can result in acetylation of histones H3 and H4, subsequent to TCA cycle dysregulation and disruption to fatty acid synthesis and cholesterol biosynthesis pathways, indicating that GLT can affect gene transcription.

Item Type:	Thesis
Creators:	Hanna, K.
Date:	July 2018
Rights:	This work is the intellectual property of the author. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed to the owner(s) of the Intellectual Property Rights.
Divisions:	Schools > School of Science and Technology
Record created by:	Linda Sullivan
Date Added:	17 Dec 2018 14:16
Last Modified:	17 Dec 2018 14:17
URI:	https://irep.ntu.ac.uk/id/eprint/35356