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Title: Effect of antioxidant supplementation on the ability of lymphocytes from older people to respond to oxidative stress
Author: Huang, Va-Wen J.
ISNI:       0000 0001 3583 2825
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2006
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Progressive impairment in the ability to adapt to environmental changes or stressors is seen as a characteristic feature of ageing. One of the major components of this adaptive response, the ability of cells to produce heat shock proteins (HSPs) following stress is severely reduced in cells of old individuals. The mechanisms by which this adaptive response is reduced are unclear, but age-related increases in the .production of Reactive Oxygen Species and accumulation of oxidation products have been implicated. The study hypothesis was that antioxidant supplementation might be beneficial to the older people by returning the oxidative environment of the cell closer to that of an adult subject, thus providing the correct cellular environment for a successful stress response. Fifty healthy subjects aged over 65 years were supplemented for 8 weeks with either placebo, vitamin C (500mg/day), vitamin E (200 mg/day), selenium (100Jlg/day), or all three. A four-day food diary was obtained from each subject to analyse dietary antioxidant intakes. Blood was taken before and after supplementation. Plasma concentrations of vitamin C, vitamin E and selenium were analysed. Lymphocytes were treated with 25JlM H20 2. which is known to result in increased HSP content in lymphocytes from adult subjects. Cells were analysed for content ofHSP60, HSC70 and HSP70 at various time points following treatment with H202. Data demonstrated that the dietary antioxidant intakes of this cohort of healthy older people were within the nonnal recommended range and· corresponding plasma antioxidant levels were also nonnal, and comparable to those values of young adults in previous studies from our laboratory. Compliance was demonstrated by the significant increase in mean plasma vitamin and selenium concentrations post-supplementation. Prior to supplementation, there was no evidence of an increase in HSPs content of lymphocytes following treatment with H202, in contrast to previous studies in healthy younger adult subjects. Following 8 weeks of supplementation, no effect was seen on HSPs induction in lymphocytes upon exposure of H202 treatment although supplementation with vitamin C alone resulted in a significant rise in baseline HSP60 content and mixed antioxidants supplementation resulted in a significant rise in baseline HSP60 and HSP70 content in lymphocytes without treatment with H202. In conclusion, lymphocytes from this cohort of elderly subjects demonstrated a severe reduction in the ability to produce HSPs following oxidative stress regardless of adequate dietary antioxidant intakes and biochemical status. Supplementation to healthy older people with vitamin C, vitamin E, selenium or a mixture of all three had no . beneficial effect on the ability of lymphocytes to produce HSPs in response to oxidative stress, thus suggesting that increase oxidative stress may not be the primary mechanism responsible for the reduced stress response. The potential protective effect of increased baseline HSPs of lymphocytes as result from supplementation with antioxidants warrants further study.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available