Exercise and Oxidative Stress: Implications in Health and Disease

This thesis presents studies investigating the effects of exercise on free radical production as measured by <i>ex vivo</i> Electron Spin Resonance (ESR) spectroscopy and the by-products of lipid peroxidation.<br/><br/>It has been proposed that exercising in hypoxia may increase free radical production. Thus study one investigated the effects of aerobic exercise performed in normobaric hypoxia (F₁O₂ = 16%) on free radical production. Results demonstrate that hypoxic exercise does not increase (<i>time x group, P </i>&gt; 0.05) systemic free radical levels. However, exercise performed at 55% <i>V̇O</i>_2peak markedly increased (<i>rest vs. exercise, P</i> &lt; 0.05) the concentration of free radical species and lipid hydroperoxides (LH) in systemic blood. This increase was related to an exercise-induced increase (<i>rest vs. exercise, P</i> &lt; 0.05) in oxygen consumption, implicating the mitochondria as a potential source of free radicals.<br/><br/>Type 1 diabetes is a disorder characterised by compromised antioxidant defences and increased oxidative stress. Study two investigated the effects of exhaustive exercise on these parameters in type 1 diabetic patients. No selective exercise difference (<i>time x group, P </i>&gt; 0.05) was observed in free radical production between groups, although, diabetic patients had a higher systemic concentration of free radicals and LH (<i>diabetic vs. control, P</i> &lt; 0.05). In addition, exhaustive exercise increased overall free radical and LH concentration (<i>rest vs. exercise, P</i> &lt; 0.05). These changes may be related to glucose auto-oxidation and mitochondrial electron '<i>leakage</i>' as potential sources of increased free radical production.<br/><br/>Study three determined the effects of exercise and ascorbic acid supplementation on free radical production in these patients. Ascorbic acid supplementation did not selectively decrease free radical production in type 1 diabetic patients (<i>group x treatment, P</i> &gt; 0.05), however, ascorbic acid supplementation decreased overall oxidative stress levels (<i>ascorbic acid vs. placebo, P </i>&lt; 0.05) and free radicals post-exercise (<i>time x treatment, P</i> &lt; 0.05). This research demonstrates that ascorbic acid is an effective antioxidant in decreasing oxidative stress in human blood.<br/><br/>A series of <i>in vitro </i>studies were performed in order to attempt to identify the origin of the free radical species. These results suggest that the free radicals are oxygen-centred and derived from the oxidation of phospholipid membranes. This work demonstrates that (1) physical exercise<i> per se</i> can increase oxygen-centred free radical production, (2) type 1 diabetic patients are more susceptible to oxidative stress, and (3) ascorbic acid is effective in attenuating oxidative stress levels in humans.

Name dc:type.qualificationname

Doctoral Thesis

Level dc:type.qualificationlevel

Student thesis

Year dc:date.issued

2002

Author dc:creator

• Davison , Gareth

Language dc:language

eng

Identifier

oai:pure.atira.dk:studenttheses/2008d4c5-2f73-472b-bd8d-c9dda79733eb

OAI identifier oai:identifier

oai:pure.atira.dk:studenttheses/2008d4c5-2f73-472b-bd8d-c9dda79733eb