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The primary goal of my studies was to elucidate the mechanisms for the well-recognized interaction between two nutrients, vitamins E and K. The outcomes from my studies assess mechanisms for adverse effects of vitamin E and provide novel information on mechanisms for vitamin K homeostasis. These findings will provide information relevant for assessing optimal intakes of vitamins E and K. This dissertation presents studies aimed at evaluating three different mechanisms by which vitamin K status could be decreased by increases in whole body vitamin E concentrations in rats supplemented with vitamin E by subcutaneous injections (100 mg α-tocopherol (α-T)/ kg body weight per day), the model system developed in the Traber lab. The tested mechanisms by which vitamin E leads to reduced vitamin K status were: 1) increasing vitamin K metabolism, 2) decreasing menaquinone-4 (MK-4) synthesis from dietary phylloquinone (PK) and 3) potentiating vitamin K excretion through xenobiotic pathways. Two approaches were undertaken to evaluate the hypothesis that vitamin E increases vitamin K metabolism. In Aim 1.1, the in vitro omega-hydroxylation of vitamin K by human cytochrome P450 CYP4F2 (expressed in insect microsomes) was tested because CYP4F2 is considered the limiting step in the catabolism of both vitamins. Chapter 2 shows that CYP4F2 more rapidly hydroxylated vitamin K compared with vitamin E. Moreover, vitamin E did not stimulate vitamin K metabolism in vitro. Thus, it is unlikely vitamin E stimulates vitamin K metabolism in vivo by direct interaction with the CYP4F2 enzyme-substrate complex. In Aim 1.2, the in vivo urinary and biliary excretion of vitamin K metabolites was investigated. Chapter 3 shows that α-T-injected rats significantly increased urinary excretion of vitamin E catabolites, but no increases in urinary vitamin K catabolites were found. Chapter 4 shows that α-T-injected rats increased biliary excretion of 5C-aglycone, a major vitamin K catabolite shared by MK-4 and PK. However, the overall in vivo excretion of vitamin K catabolites was not changed when urinary excretion was also taken into account. Aim 2 evaluated the hypothesis that α-T interferes with the conversion of PK to MK-4 because α-T and PK have similar side-chains. In Aim 2.1, conversion of PK or MN to MK-4 was tested in vivo. Rats were fed semi-purified diets containing equimolar concentrations of either PK or MN for 10 days, then α-T injections were undertaken. Chapter 3 shows that extra-hepatic tissues from α-T injected rats contained significantly lower MK-4 concentrations irrespective of whether the rats were fed PK or MN. These findings show that if vitamin E is interfering with the metabolic mechanism of MK-4 synthesis, then it is not specific to the cleavage of PK's side chain. In Aim 2.2, conversion of deuterium-labeled PK (d₄-PK) to d₄-MK-4 was used to evaluate the extra-hepatic tissue uptake of d₄-PK in α-T-injected rats. Rats were fed semi-purified diets containing equimolar concentrations of d₄-PK similar to my previous study for 10 days then α-T injections were undertaken for 7 days. Chapter 5 shows that total (labeled and unlabeled) vitamin K concentrations decreased in extra-hepatic tissues from α-T injected rats fed d₄-PK. Both d₄-MK-4 and d₄-PK concentrations decreased, suggesting that MK-4 concentrations were dependent upon those of d₄-PK. These findings suggest that PK, and not MN, is the primary substrate for MK-4 synthesis in extra-hepatic tissues. Moreover, both d₄-MK-4 and d₄-PK decreased in α-T-injected rats demonstrating that vitamin E's untoward effect on vitamin K status is likely a mechanism that is shared by both vitamin K forms and not specific to MK-4 synthesis. Recycling of vitamin K from the epoxide was not examined in this study and interference with the recycling mechanism for either PK or MK-4 in α-T injected rats has not been examined. Vitamin E metabolism is greatly increased in α-T-injected rats by increasing various xenobiotic pathways. Thus, vitamin K status was hypothesized to decrease in α-T-injected rats as a result of the up-regulation of these pathways. As shown in Aim 1, urinary vitamin K metabolite excretion was not increased in α-T-injected rats. In Aim 3.1, the biliary excretion of vitamins E and K were examined to evaluate whether the increased expression in biliary transporters, such as MDR1, led to increased vitamin K and E excretion via the bile. Chapter 4 shows that α-T increased in bile over the week of vitamin E injections and α-CEHC was the major vitamin E form excreted in bile. Although biliary PK secretion was unchanged and biliary MK-4 was undetectable, increased excretion of a major catabolite of both PK and MK-4, 5C-aglycone, was observed. In Aim, 3.2, the gene expression of enzymes and transporters in liver and extra-hepatic tissues as mechanisms involved in regulating their concentrations in these tissues was assessed. In Chapters 3 and 5, increased expression of biliary transporters were observed, one of which is known to bind the vitamin K intermediate MN as its substrate. It is possible other vitamin K catabolites, in addition to 5C-and 7C-aglycone, may have been excreted that were unaccounted for, e.g. MN or vitamin K epoxide metabolites. In summary, my studies have shown vitamin K status is decreased in α-T-injected rats because PK and MK-4 concentrations are decreased in many extra-hepatic tissues. Although metabolism of vitamin K was not stimulated in response to α-T injections, increased excretion of a vitamin K catabolite was measured in the bile; however it may not account for all of the vitamin K loss observed in tissues. Alternatively, transport of PK and MN to extra-hepatic tissues or MK-4 recycling may have been inhibited in response to vitamin E. Further studies are needed to distinguish between these mechanisms. / Graduation date: 2013

No description available.

Call number: LD2668 .T4 1952 C6 / Master of Science

This purpose of this study was to determine the effects of vitamin E and/or resistance exercise on insulin resistance and glucose uptake. Nine subjects, who were currently active but not strength training, were assigned to either the vitamin E or placebo group based on their prescreening measurements. Subjects underwent a 3-week vitamin E washout period before testing. At baseline testing subjects were given a 75-gram glucose load and blood was drawn every 15-minutes for 2-hours to analyze insulin and glucose response. Another oral glucose tolerance test (OGTT) was performed 45minutes after a 50-minute full body progressive resistance training session to determine insulin and glucose response to exercise. Subjects ingested either the placebo (3 capsules of olive oil) or 1200 IU vitamin E (3 capsules) for 9-weeks. After 3-weeks of supplementation the subjects returned for another exercising OGTT. After this session the subjects began a 6-week progressive resistance exercise program, in which they performed another OGTT after the last session. Both groups showed a significant increase in strength gains pre and post resistance training. The statistical analysis failed to demonstrate any differences between groups in insulin or glucose response in any of the four OGTT trials, but there were multiple trends present. Combining vitamin E supplementation with resistance training increased insulin sensitivity and the disposal of glucose. Both groups also had significant strength gains from pre to post study. Future research is needed for verification of these trends. / School of Physical Education

Graduation date: 1991

The aim of this study was to examine whether vitamins E (200 IU) and C (1 g) in combination would influence exercise-induced lipid peroxidation to a greater extent than vitamin E (400 IU) alone. A placebo-controlled study was carried out on 7 collegiate cyclists who were supplemented with 1) vitamin C (1 g); 2) vitamins E (200 IU) and C (1 g); and vitamin E (400 IU) during 3 treatments, each 3 weeks in duration. The serum concentrations of hematocrit and MDA, one marker of lipid peroxidation, were measured immediately before, immediately after, and 24 hours after each exercise bout. After the vitamin C treatment, MDA serum concentration of the athletes (n=7) increased 85% above the baseline values of the placebo values, the vitamin E/C treatment showed a 29% increase, and the vitamin E treatment showed a 39% decrease. Pre- to post-exercise serum MDA levels increased 64% in the placebo group, a 29% increase in the vitamin C treatment group, a 23.2% increase in the vitamins E/C treatment group, and a 46.9% increase in the vitamin E treatment group. It is concluded that exercise-induced lipid peroxidation is more greatly influenced post-exercise by a combination of vitamins E (200 IU) and C (1 g), than by either vitamin C (1 g) alone, or vitamin E (400 IU) alone. / Department of Family and Consumer Sciences

Call number: LD2668 .T4 1953 R62 / Master of Science

published_or_final_version / Biochemistry / Master / Master of Philosophy

To determine whether extreme endurance exercise induces lipid peroxidation, we studied 14 athletes (5 females: 9 males) during a 50 km ultramarathon (trial 1) and during a sedentary protocol (trial 2) one month later. At dinner the evening before the race (or sedentary trial), subjects consumed vitamin E labeled with stable isotopes (75 mg each d₃-RRR and d₆-all rac-α-tocopheryl acetates). Blood samples were taken at baseline, 30 minutes pre-race, mid-race, post-race, 1 h post-race, 24 h post-race, and at corresponding times for each individual during trial 2. During the sedentary day of trial 2, subjects consumed the same amounts of race day foods, including ergogenic aids, that they had consumed in trial 1; vitamin E intakes were 77 ± 40 mg, and vitamin C 406 ± 169 mg. All 14 subjects completed the race; average time to completion was 390 ± 67 minutes. Plasma F₂-isoprostanes (F₂-I), labeled and unlabeled α-tocopherol, and ascorbic acid (AA) were measured. F₂-I increased from 76 ± 24 pg/ml pg/ml at pre-race to 117.4 ± 38.0 pg/ml (p<0.0008) at mid-race to 130 ± 54 pg/ml (p<0.0001) at post-race, then returned to baseline at 24 hours post-race; F₂-I were unchanged during trial 2. Deuterated d₃ α-tocopheryl (d₃ α-Toc) disappearance rates were faster (2.8x10⁻⁴ ± 0.5x10⁻⁴) during the race compared to the sedentary trial (2.3x10⁻⁴ ± 0.6x10⁻⁴; p < 0.03). Plasma AA increased from 75.2 ± 11.2 μM at pre-race to 157.7 ± 36.2 μM at race end (p<0.0001) and decreased to below baseline concentrations at 24 h post-race (40.4 ± 5.2 μM p<0.0001). AA levels also increased during trial 2. Despite increased plasma AA, F2-I increased during exercise, but not during the sedentary period. Additionally, vitamin E disappeared faster during the run compared to the sedentary protocol. Thus, extreme endurance exercise results in the generation of lipid peroxidation and increased vitamin E utilization. / Graduation date: 2001