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The effects of light at night and/or melatonin on hormones, metabo- lites, appetite control, vascular function, and behavioural responses.

Albreiki, Mohammed S. (2017) The effects of light at night and/or melatonin on hormones, metabo- lites, appetite control, vascular function, and behavioural responses. Doctoral thesis, University of Surrey.

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Light at night (LAN) is a major factor in disruption of SCN function, including melatonin suppression. Melatonin has been linked to a variety of biological processes such as lipid and glucose metabolism, vascular parameters, appetite, and behaviour. However, few human studies have investigated the effect of LAN and suppressed melatonin prior to and after an evening meal. The current thesis aims to investigate the impact of light at night and/or mela- tonin on hormones, metabolites, appetite, vascular function, and behaviour prior to and after an evening test meal in healthy participants. The first study investigated the effect of dim or bright light conditions on hor- mones, metabolites, appetite, vascular function and behavioural responses. Glucose tolerance and insulin sensitivity were reduced, lipid profiles altered and salivary melatonin suppressed under bright light compared to dim light conditions. Subjec- tive mood was improved and appetite scores increased in bright light. No differences were seen in vascular parameters. Although clear differences were apparent it could not be determined whether the effects were due to the light at night, the absence of melatonin or a combination of the two. The second study involved three conditions with the administration of exogenous melatonin 90 mins before the evening test meal under bright and dim light conditions compared to bright light alone with the consequent melatonin suppression. Glucose tolerance and insulin sensitivity were reduced and lipid profile altered in bright light when melatonin was suppressed compared to the two conditions with exogenous melatonin. Mood was improved and appetite increased with lower leptin levels and elevated wrist temperature with bright light and suppressed melatonin. Statistical analysis showed that the major effects were due to melatonin. These studies demonstrate a possible role for melatonin in glucose tolerance, insulin sensitivity and lipid metabolism when eating late at night which may have implications for shift-workers.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Albreiki, Mohammed S.
Date : 31 August 2017
Funders : Abu Dhabi Health service company "SEHA"
Copyright Disclaimer : This thesis and the work to which it refers are the results of my own efforts. Any ideas, data, images or text resulting from the work of others (whether published or unpublished) are fully identified as such within the work and attributed to their originator in the text, bibliography or in footnotes. This thesis has not been submit- ted in whole or in part for any other academic degree or professional qualification.I certify that the intellectual content of this thesis is the product of my own work and that all the assistance received in preparing this thesis and sources have been acknowledged. I agree that the University has the right to submit my work to the plagiarism detection service Turnitin UK for originality checks. Whether or not drafts have been so-assessed, the University reserves the right to require an electronic version of the final document (as submitted) for assessment as above. ii June 2017 Mohammed S Albreiki
Contributors :
Depositing User : Mohammed Al Breiki
Date Deposited : 07 Sep 2017 09:13
Last Modified : 31 Oct 2017 19:25

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