J Am Geriatr Soc. 2014 (Feb); 62 (2): 222–229 ~ FULL TEXT
Sen A, Marsche G, Freudenberger P, Schallert M, Toeglhofer AM,
Nagl C, Schmidt R, Launer LJ, Schmidt H.
Research Unit for Genetic Epidemiology,
Institute of Molecular Biology and Biochemistry,
Center of Molecular Medicine,
Medical University of Graz,
OBJECTIVES: To examine the association between plasma concentrations of antioxidative micronutrients and leukocyte telomere length (LTL) in elderly adults.
DESIGN: Cross-sectional cohort study.
SETTING: Austrian Stroke Prevention Study, a population-based cohort study on brain aging.
PARTICIPANTS: Individuals with a mean age of 66 ± 7 (n = 786; 58% female).
MEASUREMENTS: Concentrations of vitamin C, lutein, zeaxanthin, β-cryptoxanthin, canthaxanthin, lycopene, α- and γ-tocopherol, α- and β-carotene, and retinol in plasma, advanced oxidation protein products as a measure of oxidative stress in serum, and LTL were measured. Vitamins and carotenoids were measured using high-performance liquid chromatography, advanced oxidation protein products using spectrophotometry, and telomere length using quantitative real-time polymerase chain reaction.
RESULTS: Multiple linear regression analyses with adjustment for age and sex demonstrated that higher lutein, zeaxanthin, and vitamin C concentrations were strongly associated with longer telomere length. The associations were independent of body mass index, maximum oxygen uptake, and vascular risk factors and were not mediated by advanced oxidation protein products content.
CONCLUSION: This study provides first evidence that higher lutein, zeaxanthin, and vitamin C concentrations in plasma are associated with longer LTL in normal elderly persons and suggest a protective role of these vitamins in telomere maintenance.
From the FULL TEXT Article:
Progressive shortening of telomere length with each cell division is associated with cellular senescence and apoptosis.  Shorter leukocyte telomere length (LTL) is linked to aging [2, 3] and age-related diseases such as cardiac disease, [4, 5] diabetes mellitus, [6, 7] hypertension, [8, 7] increased cancer,  and mortality.  Heritability of LTL ranges from 36% to 84% depending on population.  Environmental and lifestyle factors such as body mass index (BMI), [5, 12] smoking,  socioeconomic status,  and dietary habits  influence LTL. Shorter LTL is associated with oxidative stress. [15, 16] Evidence from previous in vitro,  in vivo,  and clinical studies [4, 7, 18] suggests that an imbalance between free oxygen radicals and antioxidant concentration in the cellular environment contributes to telomere attrition. Epidemiological studies report an inverse association between dietary micronutrients and oxidative stress,  which suggests that dietary micronutrients may exert protective effects on telomere shortening through antioxidative properties. A limited number of studies have investigated the association between dietary antioxidants and LTL by administering self-reported questionnaires. [14, 20] To the knowledge of the authors of the current study, no study has investigated the association between directly measured plasma levels of antioxidative micronutrients and LTL. The current study was designed to test the hypothesis that higher plasma concentrations of vitamin C, lutein and zeaxanthin (Lu~Zx), β-cryptoxanthin, canthaxanthin, lycopene, α- and γ-tocopherol, α- and β-carotene, and retinol are associated with longer LTL. In addition to assessment of the independent effect of individual micronutrients on LTL, the pooled effects of micronutrients in the provitamin A, non-provitamin A, and vitamin E subgroups and total antioxidant status were evaluated. Whether low oxidative stress, as measured according to advanced oxidation protein product (AOPP) content in serum, mediated a favorable effect of the micronutrients on LTL was further explored.  The study was performed in 786 participants of the Austrian Stroke Prevention Study (ASPS), a population-based cohort study in elderly adults.
This is the first study to investigate the association between plasma levels of antioxidative micronutrients such as Lu~Zx, vitamin C, β-cryptoxanthin, canthaxanthin, lycopene, α- and γ-tocopherol, α- and β-carotene, and retinol and LTL in a population-based elderly cohort. A strong and highly significant protective effect of Lu~Zx and vitamin C on LTL was found. No other antioxidants or the pooled subgroups of provitamin A, non-provitamin A, vitamin E, and total antioxidant status of all micronutrients were associated with telomere length. The proportion of LTL variability that was explained by Lu~Zx was 0.6%, and for vitamin C, it was 4%. It was observed that serum AOPP content did not mediate the effects of Lu~Zx and vitamin C on LTL.
Results in Relation to Other Studies
Several studies have reported that eating fruits and vegetables rich in vitamin C and Lu~Zx reduce the incidence of age-related chronic disease [30, 31] and total mortality. [32, 33] Other studies have demonstrated that LTL is associated with survival  and chronic diseases. [5, 6, 8, 7] The current study investigated whether antioxidant status modified LTL. The findings are consistent with those of the cross-sectional Sisters Study of 586 middle aged to elderly women. The authors reported that higher intake of vitamin C from foods and multivitamin supplements was associated with longer telomere length,  but another study found no association between plasma vitamin C and LTL in a homogeneous population of 4,441 middle aged to elderly women.  The fact that the first study included only women might have been responsible for the discrepant findings between that study  and the current one, which included men and women. Consistent with the previous study's findings, the sex-stratified analysis in the current investigation also showed that the association between vitamin C concentration and LTL was weaker in women. A significant association was observed only in men. The same was true for the relationship between Lu~Zx and LTL. A relationship between vitamin D and LTL has also been reported.  Higher concentrations of vitamin D were associated with longer telomere length in a study of 2,160 women aged 18 to 79 from a large population-based cohort of twins. Vitamin D was not measured in the current study cohort.
Antioxidative Properties of Lutein and Zeaxanthin (Lu~Zx) and Vitamin C
Lu~Zx and vitamin C may protect LTL through their antioxidative properties by improving intracellular redox status. Oxidative stress is considered to be one of the major causes of DNA damage and LTL shortening. Several in vitro and in vivo studies have shown that Lu~Zx [36, 37] and vitamin C  prevent DNA breakage and modulate DNA repair through their antioxidative activity. Studies have also shown that the antioxidative action of vitamin C protects telomeres from attrition in cell culture.  In the context of the current study findings, previous in vitro, in vivo, and clinical studies suggested that non-provitamin A carotenoids have greater protective effects against DNA damage than provitamin A carotenoids.  This is consistent with the finding of the current study that lutein and zeaxanthin, which are non-provitamin A carotenoids, were directly related to LTL, whereas no such association was seen for the provitamin A carotenoids retinol, β-carotene, α-carotene, and β-cryptoxanthin.
Indirect Mechanisms of Lutein and Zeaxanthin (Lu~Zx) and Vitamin C
Other mechanistic properties by which Lu~Zx and vitamin C may slow telomere attrition are immune-modulatory actions, [40, 41] anti-inflammatory activity, [42, 43] modulation of apoptosis, [44, 45] and lymphocyte proliferation.  Of particular interest are data demonstrating that saturated vitamin C levels in endothelial cells are necessary to protect tetrahydrobiopterin from oxidation and to provide optimal conditions for cellular nitric oxide synthesis.  Endothelium-derived nitric oxide is a potent signaling molecule in the cardiovascular system, participating in many processes such as vascular relaxation, inhibition of platelet aggregation, and preservation of normal vessel wall structure.  Endothelial nitric oxide synthase activity has been reported to regulate telomerase activity and delay endothelial cell senescence. [49, 50]
Higher Lu~Zx and vitamin C levels may be a marker of a healthy lifestyle. Therefore, their association with LTL may solely reflect the protective role of healthy lifestyle on biological aging. [33, 51]
Strength and Limitations
There are several limitations of the current study. First, the measurement of micronutrients, LTL, and AOPP content at a single time point limits causal inferences. Further insights can be expected from longitudinal studies. Second, AOPP content was measured as a single marker of oxidative stress. It is conceivable that a wider panel of lipid and especially DNA oxidative stress markers, such as urinary 8-hydroxy deoxyguanosine, would provide more information on possible oxidative stress-related actions of Lu~Zx and vitamin C on LTL. Third, although multiple confounders were adjusted for, the possibility that residual confounding may at least partially explain the findings cannot be fully excluded.
This study has several strengths. Actual plasma concentrations of carotenoids and vitamins were used, in contrast to information based on self-reported questionnaires. [14, 20] This approach should have resulted in less bias and imprecision than with self-reported dietary data. Another strength of the study is its large sample size and the extensive diagnostic examination of study participants. All DNA, plasma, and serum samples were obtained in a standardized fashion and were frozen at -80°C before measurements. Measuring each DNA sample in quadruplicate, the low intra- and interassay variability, and the established correlation (r= 0.61) between the real-time PCR and the southern blot method ensured the quality of the LTL measurements. Previously reported inverse associations between age and LTL were replicated. [2, 3] Mixed results were obtained for BMI, [4, 12] hypertension, [8, 7, 14] diabetes mellitus, [4, 6] cardiac disease, [4, 5] smoking, [4, 12, 34] and high-sensitivity CRP. [4, 13] In line with previous findings, inverse but statistically nonsignificant associations were found between diabetes mellitus, hypertension, cardiac disease, CRP level, and LTL.
Conclusion and Implications
The findings of a strong association between the antioxidative micronutrients Lu~Zx, vitamin C, and LTL may have important preventive implications. LTL shortening is associated with advancing age and with age-related diseases such as stroke, diabetes mellitus, cardiovascular diseases, and cancer. If these associations are causal, one might assume that Lu~Zx– and vitamin C–related LTL protection has the potential to prevent or modify the course of numerous widespread diseases that are among the major contributors to mortality and morbidity in aging societies.