Alhusaini, S. (Saif) (2011) The role of endoplasmic reticulum in human adipose tissue. PhD thesis, University of Warwick.

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Abstract

Adipose tissue plays a central role in the regulation of metabolic homeostasis. In
obesity adipocytes are challenged by many insults: surplus energy, inflammation,
insulin resistance and considerable endoplasmic reticulum (ER) stress. ER stress has
been casually linked to increased inflammation and insulin resistance. Also, obesity
linked type 2 diabetes is associated with hyperglycaemia, lipotoxicity and
endotoxemia. Therefore, the aims of this thesis briefly were to 1) characterise human
pre-adipocytes during differentiation, as a suitable primary cellular model to examine
intracellular pathways, 2) investigate the role of glucose and fatty acids on ER stress
pathway; as these primary insults are considered to have clear impact on
inflammation, insulin resistance (IR) status and diabetes pathogenesis 3) to examine
the role of lipopolysaccharide (LPS), a gut derived bacterial fragment, on ER stress;
as LPS is now considered a systemic circulating factor raised in conditions of IR, 4)
the role of salicylate, known to have anti-inflammatory properties which may negate
or at least attenuate the effects of ER stress.
Components of the ER stress pathways were studied in human abdominal
subcutaneous (AbSc) adipose tissue (AT) from obese and lean subjects. Following
characterisation, culture and differentiation of primary human pre-adipocytes, these
adipocytes were treated with lipopolysaccharide (LPS), high glucose (HG),
tunicamycin (Tun) and saturated fatty acids (SFA) either alone or in combination with
sodium salicylate (Sal). Quantitative RT-PCR, western blotting, adipokine analysis
were used to assess expression levels.
Markers of ER stress were significantly increased in AbSc AT from subjects with
obesity (P<0.001). Differentiated primary human adipocytes treated with LPS, Tun,
HG and SFA showed significant activation of p-eIF2α and ATF6 and their downstream
targets (P<0.05). This effect was alleviated in the presence of Sal. There was
also significant activation of AktSer473 during ER stress (P<0.05).
This thesis presents important evidence that firstly, there is increased ER stress in
human adipose tissue of obese individuals, secondly, LPS, hyperglycaemia and
saturated fatty acids induce significant ER stress in primary human adipocytes and
finally that induction is alleviated by salicylate. Taken together these studies
highlights that ER stress occurs in human differentiated pre-adipocytes is exacerbated
in conditions of high glucose, high saturated fatty acids and LPS, as well as
determining that such primary insults can be reduced by salicylates providing initial
evidence that therapeutic agents have the potential capacity to alleviate ER stress in
human adipose tissue.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QP Physiology
Library of Congress Subject Headings (LCSH):	Endoplasmic reticulum -- Effect of stress on, Adipose tissues, Endotoxins -- Physiological effect, Salicylates -- Physiological effect
Official Date:	March 2011
Dates:	Date Event March 2011 Submitted
Institution:	University of Warwick
Theses Department:	Warwick Medical School
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Tripathi, Gyanendra ; Kumar, Sudhesh
Extent:	xxx, 218 leaves : ill., charts
Language:	eng

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