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Title: The metabolism and biokinetics of vitamin E in healthy human beings and those at increased risk of cardiovascular disease
Author: Jeanes, Yvonne Margaret
ISNI:       0000 0001 3589 6423
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2003
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Vitamin E has been shown to be beneficial in the prevention of cardiovascular disease (CVD). The following research is concerned with assessing vitamin E status in healthy people and those with increased risk of CVD, who may have an altered vitamin E status. To understand the relationship between vitamin E intake, blood concentrations and metabolism healthy subjects were given varying single doses of RRR alpha-tocopheryl acetate (alpha-TA) up to 780 mg (n=20). There was a greater uptake of alpha-tocopherol in plasma and erythrocytes compared with platelets and lymphocytes. No dose-response relationship was observed, however there was a positive correlation between percentage increase in a-tocopherol concentration in plasma and erythrocyte with mg urinary alpha-carboxyethylhydroxychroman (alpha-CEHC) excreted. Less than 1% of alpha-TA was excreted as urinary a-CEHC. Research into the absorption of deuterium labelled (d6) alpha-TA showed a greater uptake into plasma and chylomicrons over 9 h when d6 alpha-TA was ingested with 17.5 g fat compared with 2.7 g fat (n=8). Furthermore, there was a greater uptake into chylomicrons over 9 h when d6 alpha-TA was ingested with toast and butter compared with cereal, cream and milk, both containing 17.5 g fat. This indicates the fat content and physical properties of a meal affect a-tocopherol absorption. The biokinetics of newly absorbed d6 alpha-tocopherol into plasma, lipoproteins and blood cells was investigated in healthy subjects (n=12). d6 alpha-Tocopherol firstly entered the chylomicrons, followed by VLDL, then LDL and HDL. In platelets and lymphocytes there was a gradual increase in d6 alpha-tocopherol concentration. A third of subjects exhibited a biphasic uptake of d6 alpha-tocopherol in platelets, with an initial peak at 6 h. Hypercholesterolemics are at increased risk of CVD and have altered lipoprotein metabolism therefore they may have altered vitamin E biokinetics. To investigate this, hypercholesterolemic and normolipidemic males ingested 150 mg d6 alpha-TA (n=16). The d6 alpha-tocopherol uptake into plasma was similar but there was a lower uptake of d6 alpha-tocopherol in low-density lipoprotein per g protein in hypercholesterolemics compared with normolipidemics. There was also a trend towards a lower uptake of d6 alpha-tocopherol into erythrocytes, platelets and lymphocytes in hypercholesterolemics. A greater percentage of hypercholesterolemics exhibited a biphasic profile in the uptake of d6 alpha-tocopherol into platelets compared with normolipidemics. Cigarette smokers are subjected to increased free radical exposure and therefore may utilise more vitamin E. Steady-state vitamin E status was measured in cigarette smokers and non-smokers (n=30). Plasma and erythrocyte alpha and gamma-tocopherol levels were similar, however cigarette smokers had a lower concentration of alpha-tocopherol in platelets and alpha- and gamma-tocopherol concentrations were lower in lymphocytes. Cigarette smokers excreted similar amounts of urinary alpha-CEHC, but more gamma-CEHC compared with non- smokers.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available