Racial group differences in plasma concentrations of antioxidant vitamins and carotenoids in hemodialysis patients

Race, ethnicity, and racism in the nutrition literature: an update for 2020

Social disparities in the US and elsewhere have been terribly highlighted by the current COVID-19 pandemic but also an outbreak of state-sponsored violence. The field of nutrition, like other areas of science, has commonly used 'race' to describe research participants and populations, without the recognition that race is a social, not a biologic, construct. We review the limitations of classifying participants by race, and recommend a series of steps for authors, researchers and policymakers to consider when producing and reading the nutrition literature. We recommend that biomedical researchers, especially those in the field of nutrition, abandon the use of racial categories to explain biologic phenomena but instead rely on a more comprehensive framework of ethnicity; that authors consider not just race and ethnicity but many social determinants of health, including experienced racism; that race and ethnicity not be conflated; that dietary pattern descriptions inform ethnicity descriptions; and that depersonalizating language be avoided.

The effect of hemodialysis, peritoneal dialysis and renal transplantation on nutritional status and serum micronutrient levels in patients with end-stage renal disease; Multicenter, 6-month period, longitudinal study

PURPOSE

Nutritional status and micronutrient levels of end stage renal disease (ESRD) patients may vary depending on the mode of renal replacement therapy (RRT). We aimed to compare the effects of hemodialysis, peritoneal dialysis (PD) and renal transplantation (RT) on micronutrient levels and nutritional status in ESRD patients.

PATIENTS AND METHODS

A total of 77 ESRD patients who had not received RRT were included in this prospective longitudinal study. All ESRD patients underwent a blood serum analysis that assessed the micronutrients such as selenium, copper, zinc, chromium, retinol, thiamine and vitamin B6 as well as a nutritional status assessment. After the baseline assessments and the initiation of RRT was accomplished, all patients were followed for 6 months.

RESULTS

The study showed significant improvements in subjective global assessment scores (percentage increases in score A were 26.6 and 36.6; p = 0.039 and p = 0.001; respectively), mid-arm circumference and the skin-fold thicknesses (p < 0.001, p < 0.001; respectively) in the RT and hemodialysis groups. The examinations at sixth month revealed a significant increase in body weight (4.8 kg; p = 0.002) and albumin levels (0.6 g/dL; p < 0.001) in only RT group. Zinc, thiamin and vitamin B6 were the most deficient micronutrients (44.1 %, 24.7 % and 35.1 %; respectively) in ESRD patients. There was a significant increase in selenium and retinol levels (p = 0.020 and p < 0.001; respectively) but a significant decrease in thiamin levels (p = 0.041) in RT patients. A significant increase in retinol levels (p = 0.028) and a significant decrease in thiamin levels (p = 0.022) was observed in the hemodialysis patients. However, no significant change in micronutrient levels was observed in the PD patients.

CONCLUSION

The results support the recommendation that ESRD patients should be supplemented with water-soluble vitamins, especially thiamine and vitamin B6, and trace elements, especially zinc. RT appears to be superior to other modes of RRT when examining SGA score, anthropometric measurements, albumin and micronutrient levels.

Inequalities and outcomes: end stage kidney disease in ethnic minorities

Background

The international evidence about outcomes of End Stage Kidney Disease (ESKD) for ethnic minorities was reviewed to identify gaps and make recommendations for researchers and policy makers.

Methods

Nine databases were searched systematically with 112 studies from 14 different countries included and analysed to produce a thematic map of the literature.

Results

Reviews (n = 26) highlighted different mortality rates and specific causes between ethnic groups and by stage of kidney disease associated with individual, genetic, social and environmental factors. Primary studies focussing on uptake of treatment modalities (n = 19) found ethnic differences in access. Research evaluating intermediate outcomes and quality of care in different treatment phases (n = 35) e.g. dialysis adequacy, transplant evaluation and immunosuppression showed ethnic minorities were disadvantaged. This is despite a survival paradox for some ethnic minorities on dialysis seen in studies of longer term outcomes (n = 29) e.g. in survival time post-transplant and mortality. There were few studies which focussed on end of life care (n = 3) and ethnicity.

Gaps identified were: limited evidence from all stages of the ESKD pathway, particularly end of life care; a lack of system oriented studies with a reliance on national routine datasets which are limited in scope; a dearth of qualitative studies; and a lack studies from many countries with limited cross country comparison and learning.

Conclusions

Differences between ethnic groups occur at various points and in a variety of outcomes throughout the kidney care system. The combination of individual factors and system related variables affect ethnic groups differently indicating a need for culturally intelligent policy informed by research to prevent disadvantage.

An Evidence-Based Systematic Review of Lutein by the Natural Standard Research Collaboration

An evidence-based systematic review of lutein by the Natural Standard Research Collaboration consolidates the safety and efficacy data available in the scientific literature using a validated, reproducible grading rationale. This article includes written and statistical analysis of clinical trials, plus a compilation of expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

Is routine multivitamin supplementation necessary in US chronic adult hemodialysis patients? A systematic review

Because of concern that United States (US) chronic hemodialysis patients are at high risk for the development of vitamin deficiencies, the great majority of such patients are routinely supplemented with a multivitamin. This policy is supported by major US dialysis providers and nonprofit organizations. Yet routine multivitamin supplementation expands hemodialysis patients' already large pill burden, probably accounts for many millions of dollars in annual costs, and in light of previous reports may even carry with it the possibility of increased risk of adverse outcomes. An analysis of the benefits of routine multivitamin supplementation in US patients is therefore in order. We performed a systematic review of the medical literature between 1970 and 2014 using the Ovid MEDLINE database to address this question. We conclude that there is insufficient evidence to support routine multivitamin use and recommend that the decision to supplement be made on an individual basis.

Reactive oxygen species, vascular Noxs, and hypertension: focus on translational and clinical research

SIGNIFICANCE

Reactive oxygen species (ROS) are signaling molecules that are important in physiological processes, including host defense, aging, and cellular homeostasis. Increased ROS bioavailability and altered redox signaling (oxidative stress) have been implicated in the onset and/or progression of chronic diseases, including hypertension.

RECENT ADVANCES

Although oxidative stress may not be the only cause of hypertension, it amplifies blood pressure elevation in the presence of other pro-hypertensive factors, such as salt loading, activation of the renin-angiotensin-aldosterone system, and sympathetic hyperactivity, at least in experimental models. A major source for ROS in the cardiovascular-renal system is a family of nicotinamide adenine dinucleotide phosphate oxidases (Noxs), including the prototypic Nox2-based Nox, and Nox family members: Nox1, Nox4, and Nox5.

CRITICAL ISSUES

Although extensive experimental data support a role for increased ROS levels and altered redox signaling in the pathogenesis of hypertension, the role in clinical hypertension is unclear, as a direct causative role of ROS in blood pressure elevation has yet to be demonstrated in humans. Nevertheless, what is becoming increasingly evident is that abnormal ROS regulation and aberrant signaling through redox-sensitive pathways are important in the pathophysiological processes which is associated with vascular injury and target-organ damage in hypertension.

FUTURE DIRECTIONS

There is a paucity of clinical information related to the mechanisms of oxidative stress and blood pressure elevation, and a few assays accurately measure ROS directly in patients. Such further ROS research is needed in humans and in the development of adequately validated analytical methods to accurately assess oxidative stress in the clinic.

The relationships between exogenous and endogenous antioxidants with the lipid profile and oxidative damage in hemodialysis patients

Background

We sought to investigate the relationships among the plasma levels of carotenoids, tocopherols, endogenous antioxidants, oxidative damage and lipid profiles and their possible effects on the cardiovascular risk associated with hemodialysis (HD) patients.

Methods

The study groups were divided into HD and healthy subjects. Plasma carotenoid, tocopherol and malondialdehyde (MDA) levels, as well as erythrocyte reduced glutathione (GSH), were measured by HPLC. Blood antioxidant enzymes, kidney function biomarkers and the lipid profiles were analyzed by spectrophotometric methods.

Results

Plasma lycopene levels and blood glutathione peroxidase (GPx) activity were significantly decreased in HD patients compared with healthy subjects. Total cholesterol, low-density lipoprotein cholesterol (LDL-c), creatinine, urea, MDA, GSH, superoxide dismutase (SOD) and catalase (CAT) were significantly increased in HD (p < 0.05). Lycopene levels were correlated with MDA (r = -0.50; p < 0.01), LDL-c (r = -0.38; p = 0.01) levels, the LDL-c/HDL-c index (r = -0.33; p = 0.03) and GPx activity (r = 0.30; p = 0.03). Regression models showed that lycopene levels were correlated with LDL-c (β estimated = -31.59; p = 0.04), while gender was correlated with the TC/HDL-c index and triglycerides. Age did not present a correlation with the parameters evaluated. GPx activity was negatively correlated with MDA levels and with the LDL-c/HDL-c and CT/HDL-c indexes.

Conclusions

Lycopene may represent an additional factor that contributes to reduced lipid peroxidation and atherogenesis in hemodialysis patients.

Increasing the vegetable intake dose is associated with a rise in plasma carotenoids without modifying oxidative stress or inflammation in overweight or obese postmenopausal women

The optimal amount of vegetable consumption required to reduce chronic disease risk is widely debated. Intervention trials evaluating biological activity of vegetables at various doses are limited. We conducted a 3-dose, crossover feeding trial to test the hypothesis that vegetable intake is associated in a dose-dependent manner with increased plasma carotenoids and subsequently reduced oxidative stress and inflammation in 49 overweight, postmenopausal women. Participants were assigned in random order to 2 (130 g), 5 (287 g), and 10 (614 g) daily servings of fresh, greenhouse-grown vegetables for 3-wk intervals with a 4-wk washout period between treatments. Plasma total carotenoids significantly increased from 1.63 to 2.07 μmol/L with a dose of 2 vegetable servings, from 1.49 to 2.84 μmol/L with a dose of 5 vegetable servings, and from 1.40 to 4.42 μmol/L with a dose of 10 vegetable servings (pre-post paired ttests, all P < 0.001). The change during each feeding period increased with each dose level (P < 0.001). Urine concentrations of 8-isoprostane F2α, hexanoyl lysine, and serum high sensitivity C-reactive protein were not affected by any administered vegetable dose. In this variable-dose vegetable study, a dose-response for plasma carotenoids was demonstrated without significant change in oxidative stress and inflammation in overweight, postmenopausal women.

Effect of n-3 fatty acid enriched eggs and organic eggs on serum lutein in free-living lacto-ovo vegetarians

BACKGROUND/OBJECTIVE

Lutein is a xanthophyll found in the chloroplasts of dark green leafy vegetables, chromoplasts of fruits, and egg yolk. Dietary, serum and macular lutein are inversely related to the risk of age-related macular degeneration. Although the lutein from egg is known to be more bioavailable than that from spinach, not much is known about lutein bioavailability from n-3 fatty acid enriched eggs and organic eggs, both of which are increasingly available to consumers.

SUBJECTS/METHODS

We determined the effects of feeding n-3 fatty acid-enriched eggs and organic eggs on serum lutein, zeaxanthin and β-carotene in 20 healthy lacto-ovo-vegetarian (LOV) adults using a single-blind, randomized, crossover study design with a 4-week washout between treatments: six organic eggs or six n-3 fatty acid enriched eggs per week or no egg control for 8 weeks each.

RESULTS

Serum lutein was significantly higher in both egg treatments (P<0.009) compared with the control, but was not different between the two egg treatments. Serum β-carotene was also higher in the egg groups compared with control but only approached significance (P=0.066). Serum zeaxanthin increased in both egg treatments compared with control but did not reach statistical significance (P=0.139).

CONCLUSION

n-3 fatty acid enriched eggs and organic eggs may both significantly increase serum lutein in healthy LOV consuming a predominately plant-based diet.

An Evaluation of Plasma Antioxidant Levels and the Risk of Breast Cancer: A Pilot Case Control Study

Antioxidant micronutrients found in fruits and vegetables have been shown in numerous studies to be protective against cancer. There is limited information on the relationship between blood antioxidant micronutrient levels and cancer among ethnic minorities. We conducted a pilot case-control study to evaluate the potential for accrual to a study of the association of plasma levels of beta-carotene, retinol, lycopene, alpha-tocopherol, and gamma-tocopherol with breast cancer risk among African American and Caucasian women seen at a large university medical center in Detroit. Cases included women with newly diagnosed invasive breast cancer who had not yet had any cancer-related therapy and who were age-matched to controls within 5 years. Plasma levels of micronutrients were analyzed by high-pressure liquid chromatography. Compared to the expected accrual based on cancer registry data, only 26% (11/42) of African American women with breast cancer enrolled, while 100% (16/16) of Caucasian cases enrolled. Control women were quickly accrued with only a 6% refusal rate. Among African American women, there was a weak inverse association between plasma lycopene levels and breast cancer risk, with a mean level of 0.17 &mgr;mol/L (SD = 0.18) among cases, and 0.24 &mgr;mol/L (SD = 0.18) among controls (p = 0.09). There was a weak direct association between plasma retinol levels and breast cancer risk among African American women, with a mean retinol level of 2.37 &mgr;mol/L (SD = 0.73) among cases and 1.98 &mgr;mol/L (SD = 0.49) among controls (p = 0.132). The interaction effect of race and lycopene was statistically significant (p = 0.048). Among the lowest lycopene tertile, the risk of breast cancer among Caucasian women was 0.76 and the risk of breast cancer among African American women was 2.29, although these odds ratios were not statistically significant. Our recruitment efforts were largely successful among Caucasian cases and controls, and African American controls, but were unsuccessful among African American cases. The results suggest a possible relationship between plasma lycopene level and breast cancer among African American women, but these results should be confirmed by a larger, more definitive study.

Plasma carotenoids and diabetic retinopathy

Diabetic retinopathy increases with duration of diabetes and may be associated with carotenoid status. Carotenoids alter the pro-oxidation/antioxidation balance, and circulating levels depend largely on dietary intake. Lower levels have been reported in diabetes and age-related macular degeneration; however, little is known of the relationship between carotenoids and diabetic complications. Consequently, the purpose of the present study was to evaluate the relationship between plasma carotenoids and diabetic retinopathy. We assessed the carotenoid-retinopathy relationship in 111 individuals with type 2 diabetes in a community-based, cross-sectional study. We photodocumented retinal status and used HPLC to measure plasma carotenoid concentrations. Data for clinical and demographic variables and risk factors for diabetic retinopathy were obtained from 24 h urine and fasting blood samples, and an interviewer-assisted lifestyle questionnaire. We found that the combined lycopene and lutein/zeaxanthin (non-pro-vitamin A (non-PVA) carotenoid) concentration when compared with the pro-vitamin A (PVA) carotenoids (alpha-carotene, beta-carotene and beta-cryptoxanthin) was significantly lower in the retinopathy than non-retinopathy group (OR 1.2 (95% CI 1.0, 1.4) v. 1.6 (95% CI 1.4, 1.7), respectively; P=0.009). A higher non-PVA:PVA ratio also predicted a lower risk of diabetic retinopathy, after adjustment for potential confounders (OR 0.33 (95% CI 0.12, 0.95); P=0.039). Finally, a higher concentration of PVA carotenoids was associated with greater odds of diabetic retinopathy, after adjustment for risk factors (P=0.049). We suggest synergies between carotenoids are implicated in diabetic retinopathy, independent of established risk factors. Importantly, our observations indicate dietary modulation of retinopathy risk may be possible by increasing intakes of lutein- and lycopene-rich foods.

γ-Tocopherol as a possible marker for nutrition-related risk: results from four National Diet and Nutrition Surveys in Britain

Relationships between vitamin E status (α and γ-tocopherol and their ratio in plasma), anthropometric and biochemical indices, and food and nutrient intakes, were studied in four British National Diet and Nutrition Surveys: children aged 1·5–4·5 years, young people aged 4·0–18·0 years, adults 19·0–64·0 years and adults aged ≥65·0 years. γ-Tocopherol:α-tocopherol ratio declined with age. In older women γ-tocopherol and γ-tocopherol:α-tocopherol ratios were directly related to indices of obesity. In young men α- and γ-tocopherols were directly correlated with obesity, but γ-tocopherol:α-tocopherol ratio was not. For young people and toddlers, fewer obesity indices were available and relationships were weaker. Other fat- and water-soluble vitamin indices correlated directly with α-tocopherol and inversely with γ-tocopherol and γ-tocopherol:α-tocopherol ratio. Whereas α-tocopherol correlated directly with ‘healthy’ nutrient choices (such as intrinsic sugars, dietary fibre, vitamins and potassium) and inversely with ‘unhealthy’ choices (extrinsic sugars and monounsaturated fats, i.e. avoidance of polyunsaturated fat), γ-tocopherol and the γ-tocopherol:α-tocopherol ratio related inversely with ‘healthy’ choices. Food groups had analogous relationships; thus, α-tocopherol related directly to use of polyunsaturated fats, fresh fruits and fruit juices, and inversely to non-polyunsaturated fats and extrinsic sugar. The reverse was true for γ-tocopherol and γ-tocopherol:α-tocopherol ratio. Although the mechanisms underlying these relationships are obscure, the γ-tocopherol:α-tocopherol ratio may reveal poor dietary choices, status predictors and a propensity for obesity in later life, especially in women.

Differential associations for menopause and age in measures of vitamin K, osteocalcin, and bone density

OBJECTIVE

To distinguish the effects of midlife aging from early postmenopause on vitamin K measures, bone formation biomarkers, and bone density.

DESIGN

Cycling older volunteers (CO; 40-52 years, n = 19) were compared to cycling young (CY; 20-30 years, n = 21) and untreated, age-matched women in the early postmenopause years (EPM; 40-52 years, mean years PM = 2.8 +/- 0.5, n = 19). We assessed sex steroids, vitamin status (phylloquinone, 25-hydroxyvitamin D, retinol), osteocalcin (OC), percentage of undercarboxylated osteocalcin (%ucOC), and bone mineral density (BMD) at the spine and hip with dual-energy x-ray absorptiometry.

RESULTS

CO women had similar estradiol and vitamin status as CY women, but lower OC (0.64 +/- 0.04 vs 0.97 +/- 0.08 nmol/L, P = 0.01) and BMD at the total hip (1.0038 +/- 0.032 vs 1.1126 +/- 0.030 g/cm2, P = 0.02). In the two older groups, BMD was similar at all sites, but OC was elevated in the EPM women (1.10 +/- 0.10 vs 0.64 +/- 0.04 nmol/L, EPM vs CO, P = 0.001). Although phylloquinone was highest in the EPM women, %ucOC was also higher when compared with all cycling women (21.9 +/- 1.7% vs 17.4 +/- 0.9%, n = 40; P = 0.02).

CONCLUSIONS

Premenopausal women show reduced BMD despite normal estrogen profiles. %ucOC may be a specific bone marker of the early postmenopause in healthy women.

The Effects of Exercise on Markers of Lipid Peroxidation in Renal Dialysis Patients Compared with Control Subjects

PURPOSE

The purpose of this study was to compare the susceptibility to exercise-induced lipid peroxidation of patients on chronic maintenance dialysis (CMD) and non-CMD control subjects.

DESIGN

Cross-sectional comparison of exercise-induced changes in breath ethane and pentane flux between patients on CMD (group A) and an age-, gender-, medical diagnosis-, smoking-, and ethanol consumption-matched comparison group (group B). Breath ethane and pentane were measured at rest before exercise, during cardiopulmonary exercise stress testing (CPX) at lactic acidosis threshold (Vo2lat), and 5 minutes after CPX.

RESULTS

Group comparisons of clinical characteristics reveal that the groups were similar in terms of age, ethnicity, comorbid diagnoses, prevalence of medication use, BMI, measurements of aerobic exercise capacity, cigarette smoking and ethanol consumption behaviors. All subjects successfully completed the CPX protocol achieving Vo2lat. There were significant differences in breath ethane flux between group A and B subjects, with greater pre-exercise, Vo2lat, and postexercise ethane levels in group A compared with group B subjects, and significant group differences, with lower breath ethane/pentane flux ratios at rest, Vo2lat, and recovery with lower ratios in group B than group A subjects.

DISCUSSION/CONCLUSIONS

This study shows that patients on CMD have greater lipid peroxidation compared with control subjects at rest and during and after physical exercise. In addition, compared with control subjects, patients on CMD preferentially peroxidize n-3 polyunsaturated fatty acids at rest and during physical exercise and recovery. The lipid peroxidation profile may result in an unfavorable endoperoxide shift and should be evaluated further, along with modalities to reduce oxidative stress among patients on CMD.

Alpha and gamma tocopherol metabolism in healthy subjects and patients with end-stage renal disease

BACKGROUND

The metabolism of alpha and gamma tocopherol, the major components of vitamin E, have not been studied in uremic patients. The major pathway of tocopherol metabolism is via phytyl side chain oxidation, leaving carboxyethyl-hydroxychromans (CEHC) as metabolites. Alpha and gamma CEHC are water soluble, renally excreted, with known potent anti-inflammatory and antioxidative properties.

METHODS

We examined serum alpha and gamma tocopherol and respective CEHC concentrations in 15 healthy subjects and 15 chronic hemodialysis patients.

RESULTS

Serum alpha tocopherol levels were similar in hemodialysis patients (12.03 +/- 1.34 microg/mL) and healthy subjects (11.21 +/- 0.20 microg/mL), while serum gamma tocopherol levels were significantly greater in hemodialysis patients (3.17 +/- 0.37 microg/mL) compared to healthy subjects (1.08 +/- 0.06 microg/mL, P < 0.0001). Serum alpha and gamma CEHC levels were tenfold and sixfold higher in hemodialysis patients compared to healthy subjects, respectively (both P < 0.0001). Serum alpha and gamma tocopherol levels and CEHC metabolites were also measured after supplementation of alpha- or gamma-enriched mixed tocopherols in both hemodialysis patients and healthy subjects. Tocopherol administration resulted in modest or nonsignificant changes in serum tocopherol concentrations, while markedly increasing serum CEHC concentrations in both healthy subjects and hemodialysis patients. Hemodialysis resulted in no change in the serum alpha or gamma tocopherol concentrations while decreasing serum alpha CEHC and gamma CEHC levels by 63% and 53%, respectively (both P = 0.001 versus predialysis). Fourteen-day administration of gamma-enriched but not alpha tocopherols lowered median C-reactive protein (CRP) significantly in hemodialysis patients (4.4 to 2.1 mg/L, P < 0.02).

CONCLUSION

First, serum alpha and gamma CEHC accumulate in uremic patients compared to healthy subjects; second, supplementation with tocopherols dramatically increases serum CEHC levels in both healthy subjects and hemodialysis patients; and, finally, CEHC accumulation may mediate anti-inflammatory and antioxidative effects of tocopherols in hemodialysis patients.

Inflammatory markers are unrelated to physical activity, performance, and functioning in hemodialysis

OBJECTIVE

To determine the associations among dietary intake and inflammatory cytokines with physical activity, function, and performance in maintenance dialysis patients.

DESIGN

Cross-sectional analysis of cohort study.

SETTING

University-affiliated dialysis units, general clinical research center.

SUBJECTS

Multiethnic cohort of maintenance hemodialysis patients.

MAIN OUTCOME MEASURES

Physical activity by accelerometry; physical performance by gait speed, stair climbing, and chair raising; physical functioning by the Medical Outcomes Study Short Form 36-item questionnaire subscale scores; and maximal and adjusted activity scores of human activity profile.

RESULTS

Levels of inflammatory cytokines were uniformly high. Tumor necrosis factor-alpha was directly correlated with dietary protein and energy intake; no other cytokines were directly or inversely correlated with intake. Dietary intake was associated with physical activity, as expected, and not significantly associated with performance or function (with the exception of gait speed). There were no significant associations among inflammatory cytokines and physical activity, performance, or function.

CONCLUSION

Although dietary intake and inflammation may independently influence traditional proxies of nutritional status, this analysis provides no evidence for a link between cytokines and physical activity, performance, or function in hemodialysis patients. More research is required to understand the role of cytokines in protein energy malnutrition and the mechanisms of wasting and functional decline in the dialysis population.

Variations in plasma lycopene and specific isomers over time in a cohort of U.S. men

Epidemiologic and laboratory studies suggest a possible role for tomato products, a rich source of the carotenoid lycopene, in the prevention of certain cancers and cardiovascular disease. Lycopene is consumed primarily as the all-trans-isomer, but the majority of lycopene in blood and tissue exists as a variety of cis-isomers. Specific isomers may be involved in different biological reactions, and patterns of isomers may provide insight into the risk or pathogenesis of disease processes. Total lycopene concentration and the concentrations of the cis- and trans-lycopene isomers were measured by HPLC in plasma samples taken 3-4 y apart from 144 mostly nonsmoking male participants in the Health Professionals Follow-up Study. Correlations between plasma concentrations determined 3-4 y apart ranged from 0.55 (all-trans-isomer) to 0.70 (cis-isomer 5 -cis) (P < 0.001). For total lycopene, the correlation was 0.63 (P < 0.001). Total cis-lycopene contributed approximately 67% of total lycopene (range 50-79%). At each time point, the various lycopene isomer concentrations were highly correlated with one another with Spearman correlation coefficients ranging from 0.90 to 0.99 (P < 0.001). Plasma concentrations of total lycopene and its most abundant isomers in samples taken 3-4 y apart were strongly correlated, indicating that dietary patterns and metabolic processes defining lycopene concentrations are stable over time. Because the patterns of lycopene isomers showed limited between-person variability, our results suggest that measuring specific lycopene isomers in epidemiologic studies may not provide additional information beyond that provided by total lycopene concentration. Single plasma samples quantitating plasma lycopene are a valid predictor of long-term exposure for epidemiologic studies.

Nutritional abnormalities contributing to cachexia in chronic illness

Cachexia is a common consequence of chronic illness. The nutritional abnormalities contributing to the clinical picture are often a composite of reduced appetite, dietary factors including protein, energy and micronutrient intake, malabsorption and increased consumption or loss of nutrients. In this article, using chronic heart failure as an example, we have reviewed the potential influences of chronic disease on each of these and how they might lead to the relentless progression of wasting and the poor prognosis associated with it.

Inflammatory markers are unrelated to physical activity, performance, and functioning in hemodialysis

OBJECTIVE

To determine the associations among dietary intake and inflammatory cytokines with physical activity, function, and performance in maintenance dialysis patients.

DESIGN

Cross-sectional analysis of cohort study.

SETTING

University-affiliated dialysis units, general clinical research center.

SUBJECTS

Multiethnic cohort of maintenance hemodialysis patients.

MAIN OUTCOME MEASURES

Physical activity by accelerometry; physical performance by gait speed, stair climbing, and chair raising; physical functioning by the Medical Outcomes Study Short Form 36-item questionnaire subscale scores; and maximal and adjusted activity scores of human activity profile.

RESULTS

Levels of inflammatory cytokines were uniformly high. Tumor necrosis factor-alpha was directly correlated with dietary protein and energy intake; no other cytokines were directly or inversely correlated with intake. Dietary intake was associated with physical activity, as expected, and not significantly associated with performance or function (with the exception of gait speed). There were no significant associations among inflammatory cytokines and physical activity, performance, or function.

CONCLUSION

Although dietary intake and inflammation may independently influence traditional proxies of nutritional status, this analysis provides no evidence for a link between cytokines and physical activity, performance, or function in hemodialysis patients. More research is required to understand the role of cytokines in protein energy malnutrition and the mechanisms of wasting and functional decline in the dialysis population.

Oxidative stress and cardiovascular disease in type 2 diabetes: the role of antioxidants and pro-oxidants

Oxidative stress occurs when there is an imbalance between free radical production and antioxidant capacity. This may be due to increased free radical formation in the body and/or loss of normal antioxidant defenses. Oxidative stress has been associated with the development of cardiovascular disease. The role of antioxidants in the primary and secondary prevention of coronary heart disease is currently under study. Although epidemiologic evidence indicates that antioxidants may decrease cardiovascular risk, clinical trial data are not conclusive. Information regarding the use and benefits of antioxidants in persons with diabetes is limited. Persons with diabetes may be more prone to oxidative stress because hyperglycemia depletes natural antioxidants and facilitates the production of free radicals. In addition, other factors such as homocysteine, insulin resistance, and aging may be contributory. This article highlights landmark clinical trials that have examined the cardioprotective effect of antioxidants. Because these trials have not been designed to study persons with diabetes, and clinical trial data for this group are not available, correlational studies are also presented. Finally, the concept of oxidative stress, the antioxidant and pro-oxidant factors that may contribute to oxidative stress, and the consequences of oxidative stress in persons with type 2 diabetes are presented. Key words: antioxidants, clinical trials,

Elevated plasma F2-isoprostanes in patients on long-term hemodialysis

BACKGROUND

End-stage renal disease (ESRD) patients on long-term hemodialysis (HD) may be under increased oxidative stress, caused by either HD or renal failure. Plasma F2-isoprostanes have been established as an important indicator of in vivo oxidative stress.

METHODS

Plasma esterified F2-isoprostanes were measured in 25 HD patients and 23 controls with normal renal function, employing gas chromatography-mass spectrometry with negative chemical ionization (GC-MS-NCI). C-reactive protein (CRP) was determined concurrently in patients and controls by enzyme-linked immunosorbent assay (ELISA). alpha-Tocopherol, retinol, albumin and creatinine were also determined.

RESULTS

The average total esterified F2-isoprostanes in the ESRD patients was 1.62 +/- 0.73 vs. 0.27 +/- 0.10 ng/mL in controls (P < 0.001), with no overlap between patients and controls. Plasma F2-isoprostanes in diabetic ESRD patients were similar to F2-isoprostanes in patients with other causes for renal failure. In a subset of 10 of these ESRD patients evaluated eight months after the initial measurement, plasma-esterified F2-isoprostanes were not altered by an individual dialysis session. Average plasma CRP values were also higher in HD patients (P < 0.02), but some patients had CRP values that were similar to controls. In the HD patients, total plasma F2-isoprostanes and plasma CRP were correlated (r = 0.48, P = 0.015). Plasma alpha-tocopherol did not differ between patients and controls, but plasma retinol was higher in patients (3.15 +/- 1.71 micromol/L) than in controls (1.97 +/- 0.51 micromol/L, P < 0.05).

CONCLUSIONS

These results are consistent with the hypothesis that oxidative stress in ESRD patients contributes to increased values of esterified plasma F2-isoprostanes, with concurrent increases in plasma CRP levels in some patients. Impaired clearance of esterified F2-isoprostanes may contribute to the elevated levels in renal failure. Plasma esterified F2-isoprostanes may be a useful indicator to evaluate effectiveness of interventions to decrease oxidative stress and associated inflammation.

Vitamin E attenuates oxidative stress induced by intravenous iron in patients on hemodialysis

Intravenous iron application to anemic patients on hemodialysis leads to an "oversaturation" of transferrin. As a result, non-transferrin-bound, redox-active iron might induce lipid peroxidation. To test the hypothesis that vitamin E attenuates lipid peroxidation in patients receiving 100 mg of iron(III) hydroxide sucrose complex intravenously during a hemodialysis session, 22 patients were investigated in a randomized cross-over design, either with or without a single oral dose of 1200 IU of all-rac-alpha-tocopheryl acetate taken 6 h before the hemodialysis session. Blood was drawn before and 30, 60, 90, 135, and 180 min after the start of the iron infusion, and areas under the curve (AUC0-180 min) of ratios of plasma malondialdehyde (MDA) to cholesterol and plasma total peroxides to cholesterol (two markers of lipid peroxidation) were determined as the outcome variables. At baseline of the session without vitamin E supplementation, plasma alpha-tocopherol concentrations (27.6 +/- 1.8 micromol/L) and ratios of alpha-tocopherol to cholesterol (5.88 +/- 1.09 mmol/mol) were normal, plasma MDA concentrations were above normal (1.20 +/- 0.28 micromol/ L), and bleomycin-detectable iron (BDI), indicating the presence of redox-active iron, was not detectable. Upon iron infusion, BDI and MDA concentrations increased significantly (P < 0.001). BDI concentrations explained the increase over baseline in MDA concentrations (MDA = 1.29 +/- 0.075 x BDI). Vitamin E supplementation, leading to a 68% increase in plasma alpha-tocopherol concentrations, significantly reduced the AUC0-180 min of MDA to cholesterol (P = 0.004) and peroxides to cholesterol (P = 0.002). These data demonstrate that a single oral dose of vitamin E attenuates lipid peroxidation in patients on hemodialysis receiving intravenous iron. Given that intravenous iron is applied repeatedly to patients on hemodialysis, this therapeutic approach may protect against oxidative stress-related degenerative disease in the long term.

Bioavailability and bioconversion of carotenoids

Factors that influence the bioavailability of carotenoids and their bioconversion to retinol are species of carotenoids, molecular linkage, amount of carotenoids consumed in a meal, matrix in which the carotenoid is incorporated, effectors of absorption and bioconversion, nutrient status of the host, genetic factors, host related factors, and mathematical interactions. In this paper, current knowledge of these factors is examined. Although data are not sufficiently comparable to allow an extensive systematic comparison of results, a number of conclusions can be drawn from the information available.