Oxidative Stress, Gamma-tocopherol and Colorectal Adenoma Open Access

Huang, Dina (2015)

Permanent URL: https://etd.library.emory.edu/concern/etds/1g05fc21z?locale=en
Published

Abstract

Background:
Oxidative stress is considered both the initiator and promoter of colorectal carcinogenesis. In this study we examined the use of gamma-tocopherol, a major isoform of vitamin E, as an oxidative biomarker and assessed its association with incident, sporadic colorectal adenoma. We conducted these analyses because the blood levels gamma-tocopherol serve as a reflection of metabolic response to oxidative stress and inflammation rather than a reflection of vitamin E intake. We also extended our analyses by assessing the associations of gamma-tocopherol with oxidative balance score (OBS), and several other biomarkers of oxidative stress and inflammation including F2-isoprostanes (FIP), fluorescent oxidation products (FOP), and C-reactive protein (CRP).

Methods:
The research data were obtained from two previous case-control studies of incident, sporadic colorectal adenoma conducted several years apart using similar protocols in two different U.S. states. Gamma-tocopherol levels were categorized into tertile intervals, and OBS was divided into three equal intervals. Gamma-tocopherol and biomarker levels were also dichotomized based on median values among controls. Unconditional logistic regression was used to calculate adjusted odds ratios (ORs) and corresponding 95% Confidence Intervals (95% CIs).

Results:
There were no significant associations between gamma-tocopherol (used as a continuous, dichotomized, or three-level variable) and incident, sporadic colorectal adenoma. In the analysis of the association between OBS and gamma-tocopherol, the OR for the middle vs. lowest OBS interval was 0.57 (95% CI: 0.31- 1.04), and the corresponding OR for the highest vs. lowest interval was 0.17 (95% CI: 0.07-0.41; P trend<0.001). FIP was significantly associated with plasma concentrations of gamma-tocopherol; and adjusted ORs for the medium and high levels of gamma-tocopherol were 1.51 (95% CI: 0.79-2.87) and 3.28 (95% CI: 1.58, 6.80) compared to low gamma-tocopherol concentration. None of the corresponding estimates for FOP and CRP were significantly different from the null value.

Conclusion:
Although gamma-tocopherol was not associated with colorectal adenoma directly, the significant associations between gamma-tocopherol and OBS/FIP indicate that gamma-tocopehrol may be capable of reflecting oxidation levels. A cohort study is needed to further evaluate this issue.

Table of Contents

Introduction ......................................................................................................................1
Oxidative stress and carcinogenesis .......................................................................................1
Markers of oxidative stress and inflammation and their association with colorectal tumors .................2
Gamma-tocopherol ..............................................................................................................4
ocopherols and colon tumors in human population studies ...........................................................5
Oxidative Balance Score .......................................................................................................6
Methods ............................................................................................................................7
Study population .................................................................................................................7
Data collection and laboratory analyses ...................................................................................7
Oxidative Balance Score ........................................................................................................9
Statistical analysis ..............................................................................................................10
Results .............................................................................................................................11
Discussion .........................................................................................................................13
References ........................................................................................................................16
Tables ..............................................................................................................................23

About this Master's Thesis

Rights statement
  • Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.
School
Department
Degree
Submission
Language
  • English
Research field
Keyword
Committee Chair / Thesis Advisor
Partnering Agencies
Last modified

Primary PDF

Supplemental Files