Systemic oxidative stress and cognitive performance in the population-based EVA study. Etude du Vieillissement Artériel

Cognitive impairment and kidney transplantation- underestimated, underrecognized but clinically relevant problem

BACKGROUND

Chronic kidney disease (CKD) affects the crosstalk between organs in the body and vast majority of studies were devoted to the interactions between the kidneys and the cardiovascular system. As of today, there is more evidence of the kidney and the central nervous system connections.

SUMMARY

Indeed, CKD and in particular dialysis therapy is linked to the increased prevalence of neurological complications, such as cerebrovascular disorders, movement disorders, cognitive impairment, and depression. Both traditional cardiovascular risk factors (such as diabetes, hypertension, and lipid disorders), non-traditional risk factors (such as uremic toxins, anemia, secondary hyperparathyroidism) may predispose CKD patients to neurological disorders. Likewise, cognitive problems occur more commonly in kidney transplant recipients, regardless of age, than in the general population, but the prevalence is still understudied. Cognitive impairment is associated with a higher risk of hospitalization, mortality, decreased quality of life or health care costs in kidney transplant recipients. Here, we review (i) the potential clinical impact of kidney transplantation on cerebrovascular and neurological complications, (ii) evaluation of patients with cognitive impairment for kidney transplantation (iii) the potential impact cognitive impairment on waitlisted and transplanted patients on patient care, and (iv) unmet medical needs.

KEY MESSAGES

• Cognitive impairment in kidney transplant recipients is underestimated, underrecognized but clinically relevant problem. • The screening for cognitive declines after kidney transplantation is not yet a routine practice. • Several prospective and cross-sectional studies reported improvement across some of the assessed cognitive domains after transplantation.

A systematic review of existing peripheral biomarkers of cognitive aging: Is there enough evidence for biomarker proxies in behavioral modification interventions?: An initiative in association with the nutrition, exercise and lifestyle team of the Canadian Consortium on Neurodegeneration in Aging

Peripheral biomarkers have shown significant value in predicting brain health and may serve as a useful proxy measurement in the assessment of evidence-based lifestyle behavior modification programs, including physical activity and nutrition programs, that aim to maintain cognitive function in late life. The aim of this systematic review was to elucidate which peripheral biomarkers are robustly associated with cognitive function among relatively healthy non-demented older adults. Following the standards for systematic reviews (PICO, PRIMSA), and employing MEDLINE and Scopus search engines, 222 articles were included in the review. Based on the review of biomarker proxies of cognitive health, it is recommended that a comprehensive biomarker panel, or biomarker signature, be developed as a clinical end point for behavior modification trials aimed at enhancing cognitive function in late life. The biomarker signature should take a multisystemic approach, including lipid, immune/inflammatory, and metabolic biomarkers in the biological signature index of cognitive health.

Carotenoids and Markers of Oxidative Stress in Human Observational Studies and Intervention Trials: Implications for Chronic Diseases

Carotenoids include C30, C40 and C50 terpenoid-based molecules, many of which constitute coloured pigments. However, >1100 of these are known to occur in nature and only about a dozen are known to play a role in our daily diet. Carotenoids have received much attention due to their proposed health benefits, including reducing the incidence of chronic diseases, such as cardiovascular disease and diabetes. Many of these diseases are characterized by chronic inflammation co-occurring with oxidative stress, characterized by, for example, enhanced plasma F2-isoprostane concentrations, malondialdehyde, and 8-hydroxyguanosine. Though carotenoids can act as direct antioxidants, quenching, for example, singlet oxygen and peroxide radicals, an important biological function appears to rest also in the activation of the body's own antioxidant defence system, related to superoxide-dismutase, catalase, and glutathione-peroxidase expression, likely due to the interaction with transcription factors, such as nuclear-factor erythroid 2-related factor 2 (Nrf-2). Though mostly based on small-scale and observational studies which do not allow for drawing conclusions regarding causality, several supplementation trials with isolated carotenoids or food items suggest positive health effects. However, negative effects have also been reported, especially regarding beta-carotene for smokers. This review is aimed at summarizing the results from human observational studies/intervention trials targeting carotenoids in relation to chronic diseases characterized by oxidative stress and markers thereof.

Glycerophospholipid Supplementation as a Potential Intervention for Supporting Cerebral Structure in Older Adults

Modifying nutritional intake through supplementation may be efficacious for altering the trajectory of cerebral structural decline evident with increasing age. To date, there have been a number of clinical trials in older adults whereby chronic supplementation with B vitamins, omega-3 fatty acids, or resveratrol, has been observed to either slow the rate of decline or repair cerebral tissue. There is also some evidence from animal studies indicating that supplementation with glycerophospholipids (GPL) may benefit cerebral structure, though these effects have not yet been investigated in adult humans. Despite this paucity of research, there are a number of factors predicting poorer cerebral structure in older humans, which GPL supplementation appears to beneficially modify or protect against. These include elevated concentrations of homocysteine, unbalanced activity of reactive oxygen species both increasing the risk of oxidative stress, increased concentrations of pro-inflammatory messengers, as well as poorer cardio- and cerebrovascular function. As such, it is hypothesized that GPL supplementation will support cerebral structure in older adults. These cerebral effects may influence cognitive function. The current review aims to provide a theoretical basis for future clinical trials investigating the effects of GPL supplementation on cerebral structural integrity in older adults.

Oxidative stress and cognition amongst adults without dementia or stroke: Implications for mechanistic and therapeutic research in psychiatric disorders

Oxidative stress has been implicated in cognitive deficits in disease states such as dementia and stroke. However, growing evidence shows similar associations in individuals without these conditions. We therefore set out to systematically review the literature on this topic. MEDLINE searches were conducted of medical subject-headings neuropsychology, cognition, cognition disorders, or neuropsychological tests, cross-referenced with oxidative stress, or superoxide. Exclusion criteria were dementia and stroke studies, absence of human subjects, and absence of quantifiable oxidative stress/cognition measures. The search yielded 883 results, of which 19 studies (consisting of 3662 total subjects) were included in this review. The majority of studies indicated that frontal cognitive functions were most often impaired, and lipid peroxidation was most commonly associated with impairments. Literature on learning, memory, and general cognitive function was less robust. A substantial proportion of the literature on this topic is based on psychiatric populations. Frontal-executive dysfunction implicates frontal brain regions, which are known to be susceptible to oxidative damage. Further studies are needed, and those examining psychiatric populations may be especially fruitful. Focusing on youth may yield enhanced signal detection. Further study is needed to identify which antioxidant interventions work best for which cognitive functions and for which patients.

Neuropathogenesis of delirium: review of current etiologic theories and common pathways

Delirium is a neurobehavioral syndrome caused by dysregulation of neuronal activity secondary to systemic disturbances. Over time, a number of theories have been proposed in an attempt to explain the processes leading to the development of delirium. Each proposed theory has focused on a specific mechanism or pathologic process (e.g., dopamine excess or acetylcholine deficiency theories), observational and experiential evidence (e.g., sleep deprivation, aging), or empirical data (e.g., specific pharmacologic agents' association with postoperative delirium, intraoperative hypoxia). This article represents a review of published literature and summarizes the top seven proposed theories and their interrelation. This review includes the "neuroinflammatory," "neuronal aging," "oxidative stress," "neurotransmitter deficiency," "neuroendocrine," "diurnal dysregulation," and "network disconnectivity" hypotheses. Most of these theories are complementary, rather than competing, with many areas of intersection and reciprocal influence. The literature suggests that many factors or mechanisms included in these theories lead to a final common outcome associated with an alteration in neurotransmitter synthesis, function, and/or availability that mediates the complex behavioral and cognitive changes observed in delirium. In general, the most commonly described neurotransmitter changes associated with delirium include deficiencies in acetylcholine and/or melatonin availability; excess in dopamine, norepinephrine, and/or glutamate release; and variable alterations (e.g., either a decreased or increased activity, depending on delirium presentation and cause) in serotonin, histamine, and/or γ-aminobutyric acid. In the end, it is unlikely that any one of these theories is fully capable of explaining the etiology or phenomenologic manifestations of delirium but rather that two or more of these, if not all, act together to lead to the biochemical derangement and, ultimately, to the complex cognitive and behavioral changes characteristic of delirium.

Selenium alters miRNA profile in an intestinal cell line: evidence that miR-185 regulates expression of GPX2 and SEPSH2

SCOPE

Intake of the essential micronutrient selenium (Se) has health implications. This work addressed whether some effects of Se on gene expression are exerted through microRNAs (miRNA).

METHODS AND RESULTS

Human colon adenocarcinoma cells (Caco-2) were grown in Se-deficient or Se-adequate medium for 72 h. RNA was extracted and subjected to analysis of 737 miRNA using microarray technology. One hundred and forty-five miRNA were found to be expressed in Caco-2 cells. Twelve miRNA showed altered expression after Se depletion: miR-625, miR-492, miR-373*, miR-22, miR-532-5p, miR-106b, miR-30b, miR-185, miR-203, miR1308, miR-28-5p, miR-10b. These changes were validated by quantitative real-time PCR (RT-qPCR). Transcriptomic analysis showed that Se depletion altered expression of 50 genes including selenoproteins GPX1, SELW, GPX3, SEPN1, SELK, SEPSH2 and GPX4. Pathway analysis identified arachidonic acid metabolism, glutathione metabolism, oxidative stress, positive acute phase response proteins and respiration of mitochondria as Se-sensitive pathways. Bioinformatic analysis identified 13 transcripts as targets for the Se-sensitive miRNA; three were predicted to be recognised by miR-185. Silencing of miR-185 increased GPX2 and SEPSH2 expression.

CONCLUSIONS

We propose that miR-185 plays a role in up-regulation of GPX2 and SEPHS2 expression. In the case of SEPHS2 this may contribute to maintaining selenoprotein synthesis. The data indicate that micronutrient supply can regulate the cell miRNA expression profile.

Memory improvements in elderly women following 16 weeks treatment with a combined multivitamin, mineral and herbal supplement: A randomized controlled trial

RATIONALE

There is potential for multivitamin supplementation to improve cognition in the elderly. This randomized, double-blind, placebo-controlled trial was conducted to investigate the effects of 16 weeks multivitamin supplementation (Swisse Women's 50+ Ultivite ®) on cognition in elderly women.

METHODS

Participants in this study were 56 community dwelling, elderly women, with subjective complaints of memory loss. Cognition was assessed using a computerized battery of memory and attention tasks designed to be sensitive to age-related declines to fluid intelligence, and a measure of verbal recall. Biochemical measures of selected nutrients, homocysteine, markers of inflammation, oxidative stress, and blood safety parameters were also collected. All cognitive and haematological parameters were assessed at baseline and 16 weeks post-treatment.

RESULTS

The multivitamin improved speed of response on a measure of spatial working memory, however benefits to other cognitive processes were not observed. Multivitamin supplementation decreased levels of homocysteine and increased levels of vitamin B(6) and B(12), with a trend for vitamin E to increase. There were no hepatotoxic effects of the multivitamin formula indicating this supplement was safe for everyday usage in the elderly.

CONCLUSION

Sixteen weeks ssupplementation with a combined multivitamin, mineral and herbal formula may benefit working memory in elderly women at risk of cognitive decline.

Selenium and cognitive impairment: a brief-review based on results from the EVA study

Preventing cognitive impairment and dementia in the elderly is a major public health challenge for our century and all hypotheses should be explored. Selenium (Se) is one of the factors that may affect the risk of cognitive decline. Its importance in the health and aging process has been documented. Because of the potential of selenoproteins to protect against oxidative stress, Se raises significant expectations for the prevention of chronic diseases including cancer, cardiovascular disease, and type 2 diabetes conditions commonly associated with oxidative stress. Thus, the relationships between Se and cognitive impairment or dementia can be examined through vascular risk factors for dementia, with particular interest in diabetes and dyslipidemia. In addition, in cases of Se deficiency, the brain is the organ that remains Se replete the longest suggesting that Se plays an important role in brain functions. This article presents results obtained in the frame of a longitudinal study on Se and cognitive impairment. They are consistent with the hypothesis that low Se status is a risk factor for cognitive decline even after taking into account vascular risk factors. The concomitant evolution between plasma Se decrease over a 9-year period and cognitive decline suggested that optimal Se status is potentially important to maintain neuropsychological functions in aging people. However, as our understanding of Se biology is incomplete, epidemiological studies are needed to define the groups of population that could benefit from Se supplementation.

Biomarkers for cognitive aging part II: oxidative stress, cognitive assessments, and medication adherence

The purpose of this study was to further examine potential biomarkers of cognitive aging by looking at the associations among oxidative stress, cognitive abilities, and medication adherence in a community-based sample of middle-aged and older adults (n = 42; mean age = 69 years) prescribed at least one medication for hypertension. In addition to measures described in Part I, "Biomarkers for Cognitive Aging," a 12-hr urine collection for F(2)-isoprostanes served as an indicator of oxidative stress. Participants completed a battery of cognitive assessments and 8 weeks of electronic medication monitoring for adherence to one antihypertensive agent. Oxidative stress was significantly associated with logical memory, immediate (r = -.38, p < .01) and delayed recall (r = -.42, p < .01), and recognition memory (r = -.42, p < .01) from the Wechsler Memory Scale III, number of perseveration errors (r = .26, p < .05) and categories achieved (r = -.26, p < .01) on the Wisconsin Card Sorting Test (WSCT), and medication adherence (r = -.34, p <.05). Findings indicate that a biomarker of oxidative stress, F(2)-isoprostanes corrected for vitamin E, is significantly associated with cognitive measures and a functional outcome.

Plasma selenium and risk of dysglycemia in an elderly French population: results from the prospective Epidemiology of Vascular Ageing Study

Background

A preventive role of selenium on the risk of diabetes has been reported and ascribed to the "insulin-like" activity of selenium and the antioxidant properties of the selenoenzymes. By contrast, data from cross-sectional studies and clinical trials have suggested an adverse effect of high selenium status and selenium supplementation on type-2 diabetes risk. Given these controversial results, we investigated prospectively the relationship between baseline plasma selenium concentration and occurrence of dysglycemia (impaired fasting glucose or type 2 diabetes) in an elderly French cohort.

Methods

The Epidemiology of Vascular Ageing (EVA) study (n = 1389, 59-71 years) is a 9-year longitudinal study in which, fasting plasma glucose was measured at baseline, 2, 4 and 9 years. Analyses were performed on 1162 participants with complete data.

Results

At baseline plasma selenium mean levels were 1.08 (0.21) μmol/l in men and 1.10 (0.20) μmol/l in women. During the 9-year follow-up, 127 cases of dysglycemia occurred. A significant interaction was found between plasma selenium and sex. Risk of dysglycemia was significantly lower in men with plasma selenium in the highest tertile (T3:1.19-1.97) compared to those in the lowest tertile (T1:0.18-1.00) [HR = 0.48 (0.25-0.92)], but no significant relationship was observed in women. After controlling for socio-demographic factors, lifestyle factors, cardiovascular diseases, body mass index, hypertension and lipid profile, plasma selenium remained marginally significantly associated with occurrence of dysglycemia in men [T3 vs. T1, HR = 0.50 (0.24-1.04)] and unrelated in women.

Conclusions

This prospective study suggests a sex-specific protective effect of higher selenium status at baseline on later occurrence of dysglycemia.

Antiatherogenic effects of vitamin E: the search for the Holy Grail

Vitamin E, a naturally occurring antioxidant, has been found to reduce atherosclerotic lesion formation in animal models as well as cardiovascular morbidity in several observational studies. However, a number of case-control and prospective cohort studies failed to confirm its value in the primary and secondary prevention of morbidity and mortality from coronary artery disease. Several small or larger randomized interventional trials completed to date failed to resolve the conflict. Notably, even in large, well-conducted prospective epidemiologic studies, the potential effects of residual confounding may be on the same order of magnitude as the reported benefit. The response to vitamin E supplementation in specific patient subpopulations with chronic inflammation and/or higher degrees of oxidative stress has not been studied as yet. Therefore, further large randomized interventional trials are warranted to clarify accurately the role of vitamin E in the primary and secondary prevention of atherosclerotic coronary disease in these patient groups.

Oxidative stress in cerebrospinal fluid of patients with aseptic and bacterial meningitis

This study aimed to determine whether patients with aseptic and bacterial meningitis presented alterations in oxidative stress parameters of cerebrospinal fluid (CSF). A total of 30 patients were used in the research. The CSF oxidative stress status has been evaluated through many parameters, such as lipid peroxidation through thiobarbituric acid reactive substances (TBARS) and antioxidant defense systems such as superoxide dismutase (SOD), glutathione S-transferase (GST), reduced glutathione (GSH) and ascorbic acid. TBARS levels, SOD and GST activity increase in aseptic meningitis and in bacterial meningitis. The ascorbic acid concentration increased significantly in patients with both meningitis types. The reduced glutathione levels were reduced in CSF of patients with aseptic and bacterial meningitis. In present study we may conclude that oxidative stress contributes at least in part to the severe neurological dysfunction found in meningitis.

Fibrates but not statins increase plasma selenium in dyslipidemic aged patients--the EVA study

This secondary analysis of "Etude du Vieillissement Artériel" (EVA) study reports the effect of fibrates and statins on plasma selenium concentration and its 9-year change in free-living dyslipidemic elderly. Dyslipidemic patients were categorized in three sub-groups according to final low-density lipoprotein (LDL)-cholesterol level or hypolipidemic treatment: non-treated dyslipidemic (LDL-cholesterol >4.41 mmol/L, n=84); dyslipidemics who were treated exclusively by fibrates (n=47) or by statins (n=25) whatever their serum LDL-cholesterol concentration. The influence of lipid-lowering treatments on plasma selenium concentrations and its 9-year change was evaluated by analysis of variance (ANOVA) and multivariate linear regression models taking into account cardiovascular risk and changes in lipid-profile parameters. Multivariate linear regression indicated that the plasma selenium decline was associated with the longitudinal variation in LDL (beta=-0.039+/-0.019, p=0.04) and high-density lipoprotein (HDL)-cholesterol concentrations (beta=0.187+/-0.059, p=0.002) but not with triglycerides (beta=-0.018+/-0.031, p=0.57). During the 9-year follow-up, similar plasma selenium declines were observed in all the sub-groups (p=0.33) despite plasma selenium levels being higher in fibrate users and lower in statin users (p=0.0004). The mechanisms underlying these data are not yet totally understood, but considering the risk of selenium deficiency in the elderly and its relationship with poor health status further clinical trial is needed to verify the proposed hypotheses.

Increased selenium intake in elderly high fish consumers may account for health benefits previously ascribed to omega-3 fatty acids

OBJECTIVE

To examine relationships between fish consumption and plasma selenium (Se) and red blood-cell fatty acid (RBC FA) profile in aged subjects. We hypothesised that the importance of Se has been underestimated when interpreting the beneficial effect of fish consumption on health.

DESIGN

Cross-sectional analysis of data from a prospective cohort study.

SETTING

The EVA study in Nantes, France (1991-2002).

SUBJECTS

200 subjects aged > or = 69 y with information on RBC FAs, plasma Se and completed food frequency questionnaires.

METHODS

We examined correlations between the most abundant FAs, Se and number of fish meals per week. Linear regression models were used.

RESULTS

Plasma Se was negatively correlated with RBC omega6 poly-unsaturated FA (PUFAs) and positively with omega3 PUFAs. Plasma Se, RBC omega3 PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) increased with fish consumption. Conversely, levels of omega6 PUFAs were lower in the highest fish consumption group. All associations between plasma Se and fish consumption remained significant when adjusting for omega6 PUFAs alone or additionally for age, sex, education, diabetes, hypertension, dyslipidemia, cardiovascular diseases, and broad food categories (meat, eggs, dairy products, cereals, fruit and vegetable). Associations between omega3 PUFAs and fish also remained significant in the same model independently of Se. In linear regression models adjusted for demographic indicators, fish consumption explained only 2.6% of the variance in RBC omega3 FAs (6.2% for omega6) but as much as 15% of the variance in plasma selenium.

CONCLUSIONS

The observed health benefits of fish consumption in the elderly could be related not only to the increase in omega3 FA intake but also to other nutrients such as selenium. It is important to consider this observation when interpreting associations between fish consumption and health status in the elderly, particularly with regard to brain function.

An examination of the effects of the antioxidant Pycnogenol on cognitive performance, serum lipid profile, endocrinological and oxidative stress biomarkers in an elderly population

The study examines the effects of the antioxidant flavonoid Pycnogenol on a range of cognitive and biochemical measures in healthy elderly individuals. The study used a double-blind, placebo-controlled, matched-pair design, with 101 elderly participants (60-85 years) consuming a daily dose of 150 mg of Pycnogenol for a three-month treatment period. Participants were assessed at baseline, then at 1, 2, and 3 months of the treatment. The control (placebo) and Pycnogenol groups were matched by age, sex, body mass index, micronutrient intake, and intelligence. The cognitive tasks comprised measures of attention, working memory, episodic memory, and psychomotor performance. The biological measures comprised levels of clinical hepatic enzymes, serum lipid profile, human growth hormone, and lipid peroxidation products. Statistically significant interactions were found for memory-based cognitive variables and lipid peroxidation products, with the Pycnogenol group displaying improved working memory and decreased concentrations of F2-isoprostanes relative to the control group.

Plasma carotenoids and onset of dysglycemia in an elderly population: results of the Epidemiology of Vascular Ageing Study

OBJECTIVE

The hypothesis of carotenoid having a preventive role in diabetes is suggested by their antioxidant properties. In this report, we investigated the relationship between baseline total plasma carotenoid levels and 9-year onset of dysglycemia (impaired fasting glucose or type 2 diabetes) in a healthy elderly population.

RESEARCH DESIGN AND METHODS

The Epidemiology of Vascular Ageing Study is a 9-year longitudinal study including 1,389 volunteers aged 59-71 years. Fasting plasma glucose was measured at baseline and at 2, 4, and 9 years after inclusion. The relationship between plasma carotenoid at baseline and incidence of dysglycemia was determined by Cox proportional hazards regression analysis adjusting for potential confounders.

RESULTS

At 9 years, 127 incident cases of dysglycemia had occurred. Risk of dysglycemia was significantly lower in participants with plasma carotenoid in the highest quartile (Q4) compared with participants in the lowest quartile (Q1) (Q4 vs. Q1: relative risk 0.26 [95% CI 0.14-0.49], P < 10(-4); Q3 vs. Q1: 0.55 [0.34-0.89], P = 0.01; and Q2 vs. Q1: 0.82 [0.51-1.31], P = 0.40). After controlling for sociodemographic variables, lifestyle habits, cardiovascular disease, blood pressure, BMI, and lipid profile, risk of dysglycemia remained significantly lower in participants in the highest quartile of total plasma carotenoid compared with participants in the lowest quartile (Q4 vs. Q1: 0.42 [0.22-0.82], P = 0.01; Q3 vs. Q1: 0.69 [0.41-1.15], P = 0.16; and Q2 vs. Q1: 0.80 [0.48-1.32], P = 0.38).

CONCLUSIONS

This study prospectively confirms that plasma carotenoid levels have an independent relationship to onset of dysglycemia.

Total plasma carotenoids and mortality in the elderly: results of the Epidemiology of Vascular Ageing (EVA) study

Carotenoids are pigments found in fruits and vegetables. While high intakes of fruits and vegetables have been found to be associated with lower mortality, our objective is to investigate if total plasma carotenoids, via their antioxidant properties, are associated with mortality risk in a free-living elderly population. The 'Epidemiology of Vascular Ageing' (EVA) study (n 1389; 59-71 years) is a 9-year longitudinal study with six waves of follow-up. The association between baseline total plasma carotenoids and mortality was determined by Cox proportional hazards regression analyses. Low total plasma carotenoid level was significantly associated with all-cause mortality in men but not in women. After controlling for potential confounding factors, mortality risk increased significantly in men (P = 0.03) with plasma carotenoids in the lowest quintile compared with men with plasma carotenoids in the highest (relative risk 2.94 (95% CI 1.21, 7.17)). A significant association between mortality by cancer and low plasma carotenoid level variable was also found in men (unit = 1 micromol/l; relative risk 1.72 (95% CI 1.02, 2.86); P = 0.01). Associations between total plasma carotenoids and mortality risk remained statistically significant after taking into account: (1) plasma Se level, which previously was found associated with mortality in this population and (2) thiobarbituric acid-reactive substances level considered as an indicator of oxidative stress. By showing, prospectively, in a general healthy elderly population, that total plasma carotenoid levels were independently associated with mortality risk in men, the present study suggests that total plasma carotenoid levels could be a health indicator in elderly populations.

Effects of chronic and acute ozone exposure on lipid peroxidation and antioxidant capacity in healthy young adults

BACKGROUND

There is growing evidence for the role of oxidative damage in chronic diseases. Although ozone (O3) is an oxidant pollutant to which many people are exposed, few studies have examined whether O3 induces oxidative stress in humans.

OBJECTIVES

This study was designed to assess the effect of short-and long-term O(3) exposures on biomarkers of oxidative stress in healthy individuals.

METHODS

Biomarkers of lipid peroxidation, 8-isoprostane (8-iso-PGF), and antioxidant capacity ferric reducing ability of plasma (FRAP) were analyzed in two groups of healthy college students with broad ranges of ambient O3 exposure during their lifetimes and previous summer recess either in Los Angeles (LA, n = 59) or the San Francisco Bay Area (SF, n = 61).

RESULTS

Estimated 2-week, 1-month, and lifetime O3 exposures were significantly correlated with elevated 8-iso-PGF. Elevated summertime exposures resulted in the LA group having higher levels of 8-iso-PGF than the SF group (p = 0.02). Within each location, males and females had similar 8-iso-PGF. No regional difference in FRAP was observed, with significantly higher FRAP in males in both groups (SF: p = 0.002; LA: p = 0.004). An exposure chamber substudy (n = 15) also showed a significant increase in 8-iso-PGF as well as an inhibition of FRAP immediately after a 4-hr exposure to 200 ppb O3, with near normalization by 18 hr in both biomarkers.

CONCLUSIONS

Long-term exposure to O3 is associated with elevated 8-iso-PGF, which suggests that 8-iso-PGF is a good biomarker of oxidative damage related to air pollution.

Prevention of Alzheimer's disease

The already considerable public health burden of Alzheimer's disease will likely worsen as populations around the world age. As a result, there is considerable motivation to develop effective strategies for preventing the disease. A wide variety of such strategies are under investigation and include pharmaceuticals, nutriceuticals, diet, physical activity and cognitive activity. We review here the most promising candidates and the epidemiologic evidence for their efficacy. Although none of these have yet to be definitively shown to prevent Alzheimer's disease, further research should help to clarify what role they may play in reducing the burden of this disease.

Is antioxidant therapy a viable alternative for mild cognitive impairment? Examination of the evidence

Therapeutic interventions for the prodromal stages of dementia are currently being sought with a view to delaying if not preventing disease onset. Uncertainty as to whether cognitive disorder in a given individual will progress towards dementia and adverse drug side effects has led to hesitancy on the part of drug regulators to instigate preventive pharmacotherapies. In this context, antioxidant therapies may provide a low-risk alternative, targeting very early biological changes. While a growing body of knowledge demonstrates both the importance of oxidative stress in the aetiology of dementia and the efficacy of antioxidant treatment in animal and cellular models, studies in humans are presently inconclusive. While some antioxidants, notably flavonoid- or vitamin-rich diets, appear to lower the relative risk for Alzheimer's disease in humans in observational studies, these results must be interpreted in the light of the biological complexity of the relationship between oxidative stress and neurodegeneration, and the methodological and theoretical shortcomings of studies conducted to date. A clearer understanding of these factors will assist in the interpretation of the results of the intervention studies which are now being undertaken; these studies being the only current means of establishing efficacy for preventive drug treatment of Alzheimer's disease.

Selenium level and cognitive function in rural elderly Chinese

Selenium is a trace element associated with antioxidant activity and is considered to be a protective agent against free radicals through enhanced enzyme activity. Studies on selenium and cognitive function or Alzheimer's disease have yielded inconsistent results. A cross-sectional survey of 2,000 rural Chinese aged 65 years or older from two provinces in the People's Republic of China was conducted from December 2003 to May 2005 by use of the Community Screening Instrument for Dementia, the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word List Learning Test, the Indiana University Story Recall Test, the Animal Fluency Test, and the Indiana University Token Test. Over 70% of the study participants have lived in the same village since birth. Nail samples were collected and analyzed for selenium contents. Analysis-of-covariance models were used to estimate the association between quintile selenium levels measured in nail samples and cognitive test scores, with adjustment for other covariates. Lower selenium levels measured in nail samples were significantly associated with lower cognitive scores (p < 0.0087 for all tests) except the Animal Fluency Test (p = 0.4378). A dose-response effect of selenium quintiles was also seen for those significant associations. Results in this geographically stable cohort support the hypothesis that a lifelong low selenium level is associated with lower cognitive function.

The role of oxidative stress in postoperative delirium

AIM

This study aimed to determine a marker that predicts delirium using preoperative oxidative processes in patients undergoing cardiopulmonary bypass surgery.

METHOD

Twelve of the 50 patients included in the study showed signs of delirium during postoperative follow-up. The Delirium Rating Scale was used in patients with delirium according to DSM-IV-TR in the postoperative period. Venous blood samples were obtained from the patients the day before and the day after the surgery to determine plasma antioxidant enzyme levels.

RESULTS

While there were no differences in preoperative superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and malondialdehyde (MDA) levels in both groups, catalase (CAT) levels were significantly lower in the delirium group. Postoperative SOD and MDA levels were also higher in the delirium group, while the GSH-Px levels were found to be lower when compared with those during the preoperative period. In the nondelirium group, the postoperative MDA and GSH-Px levels were found to be lower than preoperative levels, and postoperative SOD levels were found to be higher than preoperative levels. CAT levels were lower in the delirium group when the pre- and postoperative levels were compared in both groups. The postoperative levels of SOD, GSH-Px and CAT in the nondelirium group and MDA in the delirium group were significantly higher than preoperative levels.

CONCLUSION

Patients with low preoperative CAT levels appeared to be more susceptible to delirium than patients with higher CAT levels.

Memory decline of aging reduced by extracellular superoxide dismutase overexpression

Extracellular superoxide dismutase (EC-SOD) plays an important role in controlling oxidative stress as well as intercellular signaling. In the current study, we tested the effect of EC-SOD overexpression over the lifespan of a set of mice and their wild-type controls to determine the time scale over which EC-SOD overexpression might attenuate aging-induced memory impairment. Mice with overexpression of EC-SOD and wild-type controls were initially trained on the radial-arm maze as young adults (3-5 months) and then retrained during middle age (12-14 months) and retested in old age at 27 and 30 months. There was little EC-SOD effect during the young adult middle age periods. EC-SOD overexpression prevented the decline in choice accuracy when the mice were 27-30 months of age. The EC-SOD overexpressing mice maintained their performance, while the wild-type mice declined to naïve levels of performance by 30 months of age. Enhancement of EC-SOD activity appears to improve memory performance specifically in aging mice. EC-SOD mimetic treatment during the course of aging may hold promise for aging-induced cognitive impairment.

Selenium and mortality in the elderly: results from the EVA study

BACKGROUND

Inadequate plasma selenium can adversely affect the maintenance of optimal health; therefore, reported decreases in plasma selenium in an aging population are cause for concern. To further examine this hypothesis, we explored the relationships between plasma selenium and mortality in an elderly population: the EVA (Etude du Vieillissement Artériel) study.

METHODS

The EVA study was a 9-year longitudinal study with 6 periods of follow-up. During the 2-year period from 1991 to 1993 (EVA0), 1389 men and women born between 1922 and 1932 were recruited. The effects of plasma selenium at baseline on mortality were determined by Cox proportional hazards regression analysis, adjusting for the following variables: sociodemographic characteristics, dietary habits, health, and cognitive factors.

RESULTS

During the 9-year follow-up, 101 study participants died. Baseline plasma selenium was higher in individuals who were alive at the end of follow-up [mean (SD), 1.10 (0.20) micromol/L] than in those who died during the follow-up [1.01 (0.20) micromol/L; P <10(-4)]. Mortality rates were significantly higher in individuals with low selenium [increments = 0.2 micromol/L; relative risk (RR) = 1.56 (95% confidence interval, 1.28-1.89)]. After we controlled for various potential confounding factors, this association remained significant [RR = 1.54 (1.25-1.88)]. When the underlying causes of death were considered, we found an association with cancer-related mortality [adjusted RR = 1.79 (1.32-2.44)].

CONCLUSIONS

Even if it is premature to present selenium as a longevity indicator in an elderly population, our results are in accordance those of large, interventional, randomized trials with selenium, which suggest that this essential trace element plays a role in health maintenance in aging individuals.

Cognitive performance in relation to vitamin status in healthy elderly German women-the effect of 6-month multivitamin supplementation

BACKGROUND

Prior investigations have reported a link between poor status of antioxidants, folate, and cobalamin resulting in elevated total plasma homocysteine (tHcy) and methylmalonic acid (MMA) concentrations with an increased risk for reduced cognitive performance. The aim of the study was to evaluate the effect of a 6-month multivitamin supplementation on the cognitive performance of female seniors and to assess cognitive functioning in relation to vitamin status, tHcy, and MMA values at baseline.

METHODS

The study was performed as a randomized placebo-controlled double-blind trial. 220 healthy, free-living women (aged 60-91 years) were included. Blood drawings and cognitive tests were performed at the Institute of Food Science of the University of Hanover, Germany. Vitamin and cognitive status have been evaluated prior to and 6 months after supplementation. Plasma ascorbic acid, serum concentrations of alpha-tocopherol, beta-carotene, and coenzyme Q10, serum and erythrocyte folate as well as serum cobalamin, serum MMA, and plasma tHcy concentrations were measured. Activity coefficient of erythrocyte alpha aspartic aminotransferase was used as functional index for vitamin B(6) status. The cognitive performance was assessed by the Symbol Search test, a subtest of the Wechsler Adult Intelligence Scale (WAIS-III) and the pattern-recognition test. Intelligence as assessed by the 'Kurztest für Allgemeine Intelligenz' (KAI) was a further variable.

RESULTS

No significant differences in pattern-recognition and intelligence score were observed between vitamin and placebo group prior to and after multivitamin supplementation. In the Symbol Search test, the vitamin group exhibited better test results than the placebo group at both measure points. One-way ANOVA showed a marginally significant linear trend between the baseline tHcy concentration and the pattern-recognition score (P = 0.051) in the total sample. Multiple backward regression revealed only a significant influence of the school graduation on baseline cognitive function test results. A general linear model showed that the changes in cognitive function scores could not be explained by the type of treatment or blood parameters.

CONCLUSIONS

Our data indicate that 6 months supplementation of physiological dosages of antioxidants and B vitamins have no effect on cognitive performance in presumedly healthy and well-nourished female seniors. An intervention period of only 6 months may be too short for improving cognitive performance in well-educated elderly women without dementia.

Dietary factors and Alzheimer's disease

Alzheimer's disease (AD) is increasing in prevalence, and environmental risk factors have not been identified with certainty. There is evidence that oxidative stress, homocysteine-related vitamins, fats, and alcohol have a role in the pathogenesis of AD. Few large epidemiological studies have explored the associations between nutrients and AD, and there has been only one trial of vitamin E in the prevention of AD. Some studies suggest that high intake of vitamins C, E, B6, and B12, and folate, unsaturated fatty acids, and fish are related to a low risk of AD, but reports are inconsistent. Modest to moderate alcohol intake, particularly wine, may be related to a low risk of AD. Available data do not permit definitive conclusions regarding diet and AD or specific recommendations on diet modification for the prevention of AD.

Effects of lipid peroxidation and antioxidant status on peak flow in a population aged 59-71 years: the EVA study

Oxidative stress is implicated in age-related diseases and is a possible determinant in the loss of lung function. The aim of our study was to examine the association between blood indicators of oxidative metabolism and lung function in an old population. The relationships of three antioxidant indicators (selenium, total carotenoids and alpha-tocopherol) and of a marker of lipid peroxidation (thiobarbituric acid-reactive substances (TBARs)) with age and height-adjusted PEF were assessed in 688 subjects aged 59-71 years (61% never smokers, 30% ex-smokers, 9% current smokers). Stratified analyses according to gender and smoking were performed. Gender, age, tobacco and alcohol consumption, educational level and body mass index were taken into account as potential confounders. Regarding antioxidant markers, PEF was significantly positively associated with total carotenoids in the whole group (P = 0.03), and with selenium among ex-smokers only (P = 0.008). Regarding lipid peroxidation, PEF was significantly negatively associated with TBARs in men only (P = 0.02). Consistent results were observed when analyzing quantitative values and quartiles of biological markers. Results are consistent with the hypothesis of the role of both oxidants and antioxidants on lung function in elderly. Research is needed to better understand the effect of former smoking in the surviving elderly subjects.

Selenium intake, mood and other aspects of psychological functioning

Selenium is an essential trace element although the level of selenium in food items reflects the soil in which they were grown and thus varies markedly between different parts of the world. The metabolism of selenium by the brain differs from other organs in that at times of deficiency the brain retains selenium to a greater extent. The preferential retention of selenium in the brain suggests that it plays important functions. To date mood is the clearest example of an aspect of psychological functioning that is modified by selenium intake. Five studies have reported that a low selenium intake was associated with poorer mood. The underlying mechanism is unclear although a response to supplementation was found with doses greater than those needed to produce maximal activity of the selenoprotein glutathione peroxidase. Although the functions of many selenoproteins are unknown some play important roles in anti-oxidant mechanisms. As there are suggestions that oxidative injury plays a role in normal aging, schizophrenia, Parkinson's and Alzheimer's disease, the possible role of selenium is considered. Although there is evidence that supplementation with anti-oxidant vitamins shown some promise with Alzheimer's patients, and in preventing the development of tardive dyskinesia in schizophrenics taking neuroleptics, a role for selenium has been little considered.

Biochemical markers related to Alzheimer's dementia in serum and cerebrospinal fluid

The diagnosis of Alzheimer's disease (AD) is currently based on clinical and neuropsychological examination. To date there is no blood test available that can discriminate dementia patients from healthy individuals. In the present paper, an overview of the current state of knowledge on biologic markers in serum (plasma) and CSF is presented. The combination of characteristic plaque markers tau and amyloid bèta may constitute a specific and sensitive CSF marker for AD. Glial fibrillary acidic protein and antibodies in CSF may be a marker for severe neurodegeneration. CSF concentrations of the oxidative stress markers 3-nitrotyrosine, 8-hydroxy-2'-deoxyguanosine and isoprostanes are increased in AD patients. Serum 24S-OH-cholesterol may be an early whereas glial fibrillary acidic protein autoantibody level may be a late marker for neurodegeneration. To date, serum alpha(1)-Antichymotripsin concentration is the most convincing marker for CNS inflammation. Increased serum homocysteine concentrations have also been consistently reported in AD. In summary, a large overlap in mean concentrations has been observed in studies comparing AD patients with healthy controls for single markers. These studies together support the theory of testing several serum markers in combination for the diagnosis of AD.

Is pharmacological prevention of Alzheimer's a realistic goal?

A growing body of evidence suggests that several classes of drugs marketed for other indications may be effective in the prevention of Alzheimer's disease. Among the most promising of these are nonsteroidal anti-inflammatory agents, oestrogens (oestrogen replacement therapy) and antioxidant vitamins. Other less well-established candidates include histamine H(2) receptor antagonists (H(2) blockers) and 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins). For each of these, we discuss possible mechanisms for their postulated neuroprotective effects and review the studies suggesting their benefits in Alzheimer's disease. We conclude that nonsteroidal anti-inflammatory drugs and oestrogen replacement therapies may be effective in preventing Alzheimer's disease only if taken during the latent phase of the disease several years prior to the appearance of disturbances. Antioxidants may also prevent Alzheimer's disease, but unlike nonsteroidal anti-inflammatory drugs and oestrogen replacement therapies, they may continue to have beneficial effects even after the clinical onset of the disease. The only way to demonstrate the efficacy of these agents will be through randomised, controlled prevention trials. Such trials are currently underway but conclusive results may not be available for several years. Although intriguing, more studies on the neuroprotective effects of statins and H(2) blockers are needed before trials of these agents are initiated. Finally, there are other classes of pharmacological compounds emerging on the horizon, including folic acid, anti-beta-sheet conformational agents, secretase inhibitors and vaccines, that may soon prove to be effective for the prevention of Alzheimer's disease.

A possible emerging role of phytochemicals in improving age-related neurological dysfunctions: a multiplicity of effects

It is rare to see a day pass in which we are not told through some popular medium that the population is becoming older. Along with this information comes the "new" revelation that as we enter the next millennium there will be increases in age-associated diseases (e.g., cancer, cardiovascular disease) including the most devastating of these, which involve the nervous system (e.g., Alzheimer's disease [AD] and Parkinson's disease [PD]). It is estimated that within the next 50 years approximately 30% of the population will be aged 65 years or older. Of those between 75 and 84 years of age, 6 million will exhibit some form of AD symptoms, and of those older than 85 years, over 12 million will have some form of dementia associated with AD. What appears more ominous is that many cognitive changes occur even in the absence of specific age-related neurodegenerative diseases. Common components thought to contribute to the manifestation of these disorders and normal age-related declines in brain performance are increased susceptibility to long-term effects of oxidative stress (OS) and inflammatory insults. Unless some means is found to reduce these age-related decrements in neuronal function, health care costs will continue to rise exponentially. Thus, it is extremely important to explore methods to retard or reverse age-related neuronal deficits as well as their subsequent, behavioral manifestations. Fortunately, the growth of knowledge in the biochemistry of cell viability has opened new avenues of research focused at identifying new therapeutic agents that could potentially disrupt the perpetual cycle of events involved in the decrements associated with these detrimental processes. In this regard, a new role in which certain dietary components may play important roles in alleviating certain disorders are beginning to receive increased attention, in particular those involving phytochemicals found in fruits and vegetables.

A healthy body, a healthy mind: long-term impact of diet on mood and cognitive function

Certain dietary risk factors for physical ill health are also risk factors for depression and cognitive impairment. Although cholesterol lowering has been suggested to increase vulnerability to depression, there is better support for an alternative hypothesis that intake of n-3 long-chain polyunsaturated fatty acids can affect mood (and aggression). Possible mechanisms for such effects include modification of neuronal cell membrane fluidity and consequent impact on neurotransmitter function. Stronger evidence exists concerning a role for diet in influencing cognitive impairment and cognitive decline in older age, in particular through its impact on vascular disease. For example, cognitive impairment is associated with atherosclerosis, type 2 diabetes and hypertension, and findings from a broad range of studies show significant relationships between cognitive function and intakes of various nutrients, including long-chain polyunsaturated fatty acids, antioxidant vitamins, and folate and vitamin B12. Further support is provided by data on nutrient status and cognitive function. Almost all this evidence, however, comes from epidemiological and correlational studies. Given the problem of separating cause and effect from such evidence, and the fact that cognitive impairment and cognitive decline (and depression) are very likely to be significant factors contributing to the consumption of a poor diet, greater emphasis should now be placed on conducting intervention studies. An efficient approach to this problem could be to include assessments of mood and cognitive function as outcome measures in studies designed primarily to investigate the impact of dietary interventions on markers of physical health.

Cognitive decline is associated with systemic oxidative stress: the EVA study. Etude du Vieillissement Artériel

OBJECTIVE

To determine whether systemic oxidative stress status is associated with cognitive decline.

DESIGN

A longitudinal population-based study.

SETTING

A cohort study of older subjects in Nantes, France.

PARTICIPANTS

A total of 1166 high cognitive functioning subjects aged 60 to 70 in the Etude du Vieillissement Arteriel (EVA) cohort with a 4 year follow-up.

MEASUREMENTS

Subjects completed a baseline interview and a global cognitive test (Mini-Mental Status Examination (MMSE)). Blood samples were obtained at baseline to determine plasma levels of selenium, carotenoids, thiobarbituric acid reactant substances (TBARS), an indicator of lipoperoxidation, and red blood cell vitamin E. Risk of cognitive decline, defined as a loss of 3 points in MMSE score between baseline and the 4 year follow-up, was assessed by oxidative stress level.

RESULTS

Subjects with the highest levels of TBARS show an increased risk of cognitive decline (adjusted odds ratio (OR) = 2.25; confidence interval (CI) 95% = 1.26-4.02). This result is reinforced in the lower antioxidant status subgroup. Subjects with low levels of selenium have an increased risk of cognitive decline (OR = 1.58; CI 95% = 1.08-2.31) after adjustment for various confounding factors.

CONCLUSIONS

These results suggest that increased levels of oxidative stress and/or antioxidant deficiencies may pose risk factors for cognitive decline. The direct implication of oxidative stress in vascular and neurodegenerative mechanisms that lead to cognitive impairment should be further explored.

Cognitive impairment and oxidative stress in the elderly: results of epidemiological studies

Cognitive impairment is a major component of age-related dementing diseases and it has been suggested that it could share the same pathological pathways with neurodegenerative processes and cerebrovascular lesions. The free radical theory of ageing could be one of these pathways. Implication of free radical damage in processes related to cerebral ageing is a good argument in favour of the hypothesis that antioxidants may protect against cognitive impairment. Observational studies (mostly cross-sectional) of relationships between cognitive impairment and antioxidant status are based on the evaluation of dietary intake or on the levels of carotenoids, selenium and vitamins A, C and E in plasma or red blood cells. More convincing results were obtained on vitamin C and carotenoids. Despite some limitations, the comparison between results obtained in various populations is becoming increasingly informative and these studies argue for a protective effect of antioxidants on cognitive performance.

beta-carotene does not change markers of enzymatic and nonenzymatic antioxidant activity in human blood

In vitamin A-replete populations, increased concentrations of serum carotenoids have been associated with a decreased risk of degenerative diseases. The mechanism of action of carotenoids in determining antioxidant activity is largely unknown. The aim of the study was to examine the effect of carotenoid supplementation and spinach intake on erythrocyte enzyme antioxidant activities, serum or plasma nonenzymatic antioxidant concentrations, and concentrations of oxidatively damaged amino acids in plasma. Subjects received for 3 wk a basic diet (n = 10), a basic diet with a carotenoid supplement (n = 12) or with a spinach product (n = 12 per group), i.e., whole-leaf, minced, liquefied or liquefied spinach plus added dietary fiber. After 3 wk of dietary intervention, changes in serum or plasma concentrations of ascorbic acid, alpha-tocopherol, FRAP (ferric reducing ability of plasma) and uric acid and erythrocyte enzyme activities were assessed, and differences among experimental groups were tested. Consumption of spinach resulted in greater (P < 0.01) erythrocyte glutathione reductase activity and lower (P < 0.05) erythrocyte catalase activity and serum alpha-tocopherol concentration compared with the control group. Consumption of the carotenoid supplement led to lower alpha-tocopherol responses (P = 0.02) compared with the basic diet only. Our data suggest that the short-term changes in erythrocyte glutathione reductase activity and serum alpha-tocopherol concentration can be attributed to an increased carotenoid (lutein and zeaxanthin) intake, but beta-carotene is unlikely to be a causative factor. Lower erythrocyte catalase activity after intervention with spinach products may be related to other constituents in spinach such as flavonoids.

Micronutrients and ageing: intakes and requirements

Ageing (and related diseases) may be described as a process which results from impaired immunological, genetic, neurological or endocrinological functions. Oxidative mechanisms may play an important role in the ageing process. It is important, therefore, to emphasize the relationship between health and nutrition in the elderly, particularly with regard to antioxidant micronutrient requirements. Indeed, accelerated ageing may be related to a deficit in the intakes of antioxidant vitamins (tocopherols, carotenoids and vitamin C) and trace elements (Zn and Se), as well as to an impaired adaptative mechanism against oxidative stress. Physiological modifications occurring during the lifetime and environmental influences are significant factors contributing to the impairment of micronutrient status, and these factors have to be considered when defining the specific requirements of the elderly. For Fe there is no evidence of benefit of supplementation in healthy subjects, but in the present state of knowledge combined supplementation, including Zn, Se, vitamins C and E and carotenoids, could be the best way to prevent accelerated ageing and reduce the risk of several common age-related diseases.