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Title: Adiponectin as a regulator of vascular redox state in human atherosclerosis
Author: Margaritis, Marios
ISNI:       0000 0004 6495 8090
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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Atherosclerotic cardiovascular disease is a leading cause of death worldwide. Dysregulation of vascular redox state plays a crucial role in the atherosclerotic process. Increased production of vascular superoxide (O2·-) and other reactive oxygen species (ROS) leads to endothelial dysfunction, a key early step in atherogenesis. Adipose tissue is a source of vasoactive, hormone-like molecules which are termed adipokines. One of the most important adipokines is adiponectin. Adiponectin has been shown to have antioxidant, anti-atherosclerotic effects in cell culture studies and animal models. However, its role in human cardiovascular disease has not been extensively investigated. More specifically, its effects on the human vascular wall and the mechanisms regulating its synthesis in adipose tissue have not been studied before in humans. The aim of my thesis is to explore the role of adiponectin in human atherosclerosis. This was achieved through use of the Oxford CABG Bioresource: a well-phenotyped cohort and tissue bank of patients undergoing cardiac surgery. By employing a range of in vivo and ex vivo techniques, I demonstrate for the first time in humans that adiponectin has direct antioxidant effects in the vascular wall, by directly suppressing pro-oxidant vascular enzymes and restoring redox balance. These effects persist in type 2 diabetes, presence of which is linked to reduced circulating adiponectin levels. Indeed, a variety of stimuli affect adiponectin synthesis in human adipose tissue, with brain natriuretic peptide being a major driver of adiponectin synthesis. However, different adipose tissue depots demonstrate diverse responses to stimuli affecting adiponectin synthesis, owing to their functional and morphological differences. Of particular interest is the fact that synthesis of adiponectin in perivascular adipose tissue is driven by the oxidative stress status of the underlying vessel. This observation led me to document for the first time in humans the existence of a reciprocal, two-way interaction between perivascular adipose tissue and the vascular wall: high vascular oxidative stress leads to release of factors with the ability to up-regulate adiponectin expression in perivascular adipose tissue, acting as a local paracrine defence mechanism attempting to restore vascular redox state. My thesis provides proof-of-concept for this novel cross-talk between adipose tissue and the vascular wall. This can have significant impact in designing new therapeutic strategies against atherosclerosis.
Supervisor: Casadei, Barbara ; Antoniades, Charalambos ; Channon, Keith M. Sponsor: British Heart Foundation ; Medical Research Council ; Research Council UK
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Atherosclerosis ; Vascular biology ; Adipose tissue biology ; Adipokines ; Adiponectin ; Oxidative stress