Gender difference in oxidative stress and its genesis by analysis of serum alpha-tocopherol concentrations in a Japanese population

Associations between Plasma Tocopherols and Lung Cancer Risk: Results from the Southern Community Cohort Study

BACKGROUND

Despite the various anticancer activities of tocopherols, little is known about tocopherols associated with lung cancer risk among low-income African Americans (AA) and European Americans (EA) who are disproportionately affected by the disease.

METHODS

We conducted a nested case-control study that included 209 incident lung cancer cases and 406 matched controls within the Southern Community Cohort Study. Using biospecimens collected at cohort enrollment, plasma levels of α-, β/γ-, δ-, and total-tocopherols were measured by high-performance liquid chromatography with photodiode array detection. Conditional logistic regression was used to estimate ORs and 95% confidence intervals (CI) for lung cancer risk after adjusting for potential confounders. Stratified analyses were also conducted.

RESULTS

Plasma levels of total-tocopherols were inversely associated with lung cancer risk overall [OR (95% CI) for the highest vs. lowest tertile = 0.51 (0.30-0.90)]. The inverse association remained significant among EAs [0.20 (0.06-0.65)], men [0.43 (0.21-0.90)], current smokers [0.49 (0.26-0.93)], and cases diagnosed within 2 years of blood draw [0.36 (0.15-0.86)], though we did not find a significant risk reduction among AAs [0.75 (0.39-1.45)]. Notably, we found significant interactions between α-tocopherol and race after controlling the FDR to correct for multiple comparisons (Pinteraction = 0.02).

CONCLUSIONS

Our results indicate that plasma total-tocopherols are inversely associated with lung cancer risk, but the association may differ across specific isomeric forms of tocopherols, race, or other individuals' characteristics. Further large-scale studies are warranted to confirm our findings.

IMPACT

Recommendations on tocopherols for lung cancer prevention should take isomers, race, and smoking behaviors into consideration.

Complexity of vitamin E metabolism

Bioavailability of vitamin E is influenced by several factors, most are highlighted in this review. While gender, age and genetic constitution influence vitamin E bioavailability but cannot be modified, life-style and intake of vitamin E can be. Numerous factors must be taken into account however, i.e., when vitamin E is orally administrated, the food matrix may contain competing nutrients. The complex metabolic processes comprise intestinal absorption, vascular transport, hepatic sorting by intracellular binding proteins, such as the significant α-tocopherol-transfer protein, and hepatic metabolism. The coordinated changes involved in the hepatic metabolism of vitamin E provide an effective physiological pathway to protect tissues against the excessive accumulation of, in particular, non-α-tocopherol forms. Metabolism of vitamin E begins with one cycle of CYP4F2/CYP3A4-dependent ω-hydroxylation followed by five cycles of subsequent β-oxidation, and forms the water-soluble end-product carboxyethylhydroxychroman. All known hepatic metabolites can be conjugated and are excreted, depending on the length of their side-chain, either via urine or feces. The physiological handling of vitamin E underlies kinetics which vary between the different vitamin E forms. Here, saturation of the side-chain and also substitution of the chromanol ring system are important. Most of the metabolic reactions and processes that are involved with vitamin E are also shared by other fat soluble vitamins. Influencing interactions with other nutrients such as vitamin K or pharmaceuticals are also covered by this review. All these processes modulate the formation of vitamin E metabolites and their concentrations in tissues and body fluids. Differences in metabolism might be responsible for the discrepancies that have been observed in studies performed in vivo and in vitro using vitamin E as a supplement or nutrient. To evaluate individual vitamin E status, the analytical procedures used for detecting and quantifying vitamin E and its metabolites are crucial. The latest methods in analytics are presented.

The association between vitamin E intake and hypertension: results from the re-analysis of the National Health and Nutrition Survey

Recently, there has been an increasing concern about noncommunicable diseases (NCDs), in which oxidative damage plays a role. In this paper, we have re-analyzed the data from the National Health and Nutrition Survey (NHNS) 2007 to study the relationship between an NCD (e.g. hypertension) and the dietary intake of vitamin E, a potent anti-oxidative vitamin. The inclusion criteria were those aged 40 and over, excluding pregnant or lactating women, and data from 1,405 males and 2,102 females were analyzed. The mean ages were 63.5 and 62.4, respectively. Nutrients intake was evaluated from a semi-weighted, 1-d household dietary record. When the subjects were categorized into tertiles based on their vitamin E intake, higher vitamin E intake was associated with a lower percentage of subjects with hypertension (p for trend=0.01). Subjects with higher vitamin E intake had higher energy intake-adjusted intake of other nutrients which have been considered to be related to hypertension such as potassium, magnesium, and vitamin C. Logistic regression analysis was done with the low tertile of vitamin E intake as the reference. The medium and high tertiles of vitamin E intake were associated with a significantly lower odds ratio for hypertension, 0.73 (95% CI; 0.62-0.87) for the former and 0.81 (95% CI; 0.69-0.96) for the latter. Additional analyses, one adjusted for the indices associated with hypertension and one excluding the subjects with vitamin E supplementation, have yielded the similar results. In summary, re-analysis of data from NHNS has revealed that higher vitamin E intake was significantly associated with lower prevalence of hypertension.

Fluctuation of serum vitamin E (alpha-tocopherol) concentrations during exacerbation and remission phases in patients with chronic fatigue syndrome

The etiology of chronic fatigue syndrome remains unknown. Oxidative stress may be involved in its pathogenesis. Vitamin E is a major endogenous lipid-soluble antioxidative substance, and is consumed during the lipid peroxidation process. We studied a population comprising 27 patients with chronic fatigue syndrome (10 men and 17 women, 29 +/- 6 years of age) and 27 age- and sex-matched control subjects. Serum vitamin E (alpha-tocopherol) concentrations were determined and expressed as mg/g total lipids (total cholesterol and triglyceride) to evaluate oxidative stress. Serum alpha-tocopherol concentrations (mg/g lipids) were significantly (P < 0.001) lower in the patients with chronic fatigue syndrome (2.81 +/- 0.73) than in the control subjects (3.88 +/- 0.65). The patients with chronic fatigue syndrome were re-examined during a follow-up interval. After 8 +/- 2 months, 16 patients exhibited a status that warranted re-examination during remission of the symptoms at a regular visit to our hospital (Group 1), while the remaining 11 did not (Group 2). The serum alpha-tocopherol levels were significantly elevated during remission as compared with those at baseline in Group 1 (2.71 +/- 0.62 --> 3.24 +/- 0.83, P < 0.001). The levels did not significantly change after the interval in Group 2 (2.97 +/- 0.86 --> 2.85 +/- 0.73, not significant). In conclusion, serum alpha-tocopherol concentrations were significantly lower in the patients with chronic fatigue syndrome as compared with the control subjects, suggesting increased oxidative stress in the former. The low level of serum alpha-tocopherol was ameliorated during the remission phase as compared with the exacerbation phase in the patients with chronic fatigue syndrome, suggesting that increased oxidative stress may be involved in the pathogenesis of chronic fatigue syndrome and might also be directly related to the severity of the symptoms of chronic fatigue syndrome.