Vitamin E kinetics in smokers
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: The purpose of this study is to measure how much vitamin E humans utilize daily and whether people who smoke cigarettes use more vitamin E.Why should cigarette smoking use up vitamin E? Both smokers and non-smokers have similar vitamin E concentrations in their blood (plasma). So it would seem that smoking has no effect on plasma vitamin E levels. However, if plasma is directly exposed to smoke in a test tube, the vitamin E is used up. This seems contradictory - how can cigarette smoke destroy the vitamin E in test tubes, but not in people? This study focuses on this paradox. Thc answer may be that cigarette smoking actually uses up the vitamin E in the body, but the body replaces it from its stores.The specific questions to be addressed in this project are as follows: does cigarette smoking increase the use of plasma vitamin E in vivo? Are there regulatory mechanisms that increase plasma vitamin E in response to oxidative stress? Do different forms of vitamin E have different susceptibilities to cigarette smoke in vivo?The rate of vitamin E use will be measured in smokers and non-smokers in two different trials. In the first trial, non-smokers and smokers will be given vitamin E labeled with deuterium, a stable (non-radioactive) isotope of hydrogen. This will allow us to track how much vitamin E comes in and goes out of the circulation. Thc labeled vitamin E will be taken daily for 1 week; and blood samples will be taken daily during vitamin E administration and for the subsequent week, then biweekly for 30 days. In the second trial, non-smokers and smokers will be given three different forms of vitamin E with differing amounts of deuterium, administered with breakfast in a single gelatin capsule: a natural form of alpha-tocopherol, a synthetic form of alpha-tocopherol; and a natural form of alpha-tocopherol. This second trial will investigate in detail the ability of the liver to maintain plasma vitamin E levels. In addition, we will test whether smoking specifically destroys alpha-tocopherol. Urine samples will be collected in both trials to measure vitamin E metabolites. The appearance and disappearance of the deuterated tocopherols from plasma will be calculated using computer-assisted models. Statistical comparisons will be made between smokers and non-smokers for each of the forms of Vitamin E.We expect that if there is increased "oxidative stress" in smokers, then vitamin E use should be higher in smokers than in non-smokers. This will be tested in trial 1. In trial 2, different forms of vitamin E will be used to measure the release of vitamin E (stored in the liver) into the circulation. In addition, this second trial will measure how much alpha-tocopherol the body uses. This is important because alpha-tocopherol is a major dietary form of vitamin E and alpha-tocopherol has been shown to be a precursor of a kidney hormone. The information obtained from this study will indicate the daily requirements for vitamin E in normal subjects and will demonstrate if cigarette smoking increases the daily requirement for vitamin E. The data will also indicate if dietary supplementation is warranted for smokers.