Dietary antioxidants modulation of aging and immune-endothelial cell interaction

Oxidative damage by free radicals, which is the basis for the free radical theory of aging, has been well investigated within the context of oxidant/antioxidant balance. Age-associated disorders are believed to be associated with the time-dependent shift in the antioxidant/prooxidant balance in favor of oxidative stress. In this brief review, the importance of dietary antioxidant intervention on longevity and age-associated changes in bodily functions and diseases are discussed. Evidence has indicated that increasing the endogenous antioxidants defense system and modulation of free radical production by dietary restrictions contribute to increased longevity in animal models. Thus, increasing dietary intake of antioxidants is believed to increase longevity. Earlier studies have shown some increase in median life span in animal models. It was found that supplementing middle-aged (18 months) C57/BL mice with various antioxidants (vitamin E, glutathione, melatonin, and strawberry extract) had no effect on longevity as measured by the average age of death. Therefore, dietary antioxidant supplementation seems unlikely to increase longevity when begun in middle age; supplementation started in early life might be more effective. However, in middle-aged mice, vitamin E was effective in reducing lung viral titer when animals were exposed to influenza virus. Vitamin E supplementation improves cell-mediated immunity in mice and in humans. In addition to modulating the oxidation of low-density lipoproteins, vitamin E can modulate immune/endothelial cells interactions, thus reducing the risk of cardiovascular disease (CVD), a major cause of morbidity and mortality in elderly. Thus, antioxidants such as vitamin E from food sources or supplements appear to be promising for successful aging by improving immune function, and reducing the risk of several age-associated chronic diseases, such as CVD.

Effect of dietary supplementation with black currant seed oil on the immune response of healthy elderly subjects

BACKGROUND

We have shown that the age-associated increase in prostaglandin E(2) production contributes to the decline in T cell-mediated function with age. Black currant seed oil (BCSO), rich in both gamma-linolenic (18:3n-6) and alpha-linolenic (18:3n-3) acids, has been shown to modulate membrane lipid composition and eicosanoid production.

OBJECTIVE

Our objectives were to 1) test whether dietary supplementation with BCSO can improve the immune response of healthy elderly subjects, and 2) determine whether the altered immune response is mediated by a change in the factors closely associated with T cell activation.

DESIGN

A randomized, double-blind, placebo-controlled (soybean oil) study was conducted to examine the effect of 2 mo of BCSO supplementation on the immune response of 40 healthy subjects aged >/=65 y. In vivo immune function was determined by delayed-type hypersensitivity skin response. Peripheral blood mononuclear cells (PBMCs) were tested for in vitro immune response.

RESULTS

In subjects supplemented with BCSO, the total diameter of induration at 24 h and individual responses to tetanus toxoid and Trichophyton mentagrophytes were significantly higher than their baseline values. The change in response to tetanus toxoid was significantly different from that of the placebo group. The BCSO group showed a significant increase in proliferative response of PBMCs to the T cell mitogen phytohemagglutinin that was not significantly different from that observed in the placebo group. BCSO had no effect on concanavalin A-induced mitogenic response, interleukin 2 and -1beta production, and PBMC membrane fluidity. Prostaglandin E(2) production was significantly reduced in the BCSO-supplemented group, and this change was significantly different from that of the placebo group.

CONCLUSION

BCSO has a moderate immune-enhancing effect attributable to its ability to reduce prostaglandin E(2) production.

The effects of dietary antioxidants on psychomotor performance in aged mice

Male C57BL/6NIA mice were provided one of six different antioxidant diets: vitamin E, glutathione, vitamin E plus glutathione, melatonin, strawberry extract, or control, beginning at 18 months of age. A battery of motor tests--rod walk, wire hang, plank walk, and inclined screen-was administered either: 1) before dietary treatment and then 6 months later at 24 months of age: or 2) only after 6 months of dietary treatment at age 24 months. An untreated group of 4-month-old mice served as young controls. Psychomotor performance was lower in 18-month-old mice compared with 4-month-old mice in the rod walk, wire hang, and inclined screen tests; however, no further decline was seen from 18 to 24 months on any measure. Chronic dietary antioxidant treatments were not effective in reversing age-related deficits in psychomotor behavior, except for the glutathione diet on inclined screen performance. It seems that motor performance deteriorates profoundly with age, because deficits at 18 months of age were as severe as they were at 24 months, and these age-associated motor deficits may be difficult to reverse, even with antioxidant treatment.

Effect of dietary fish oil, vitamin E, and probucol on renal injury in the rat

Dietary fish oil, vitamin E, and probucol have been considered in a variety of human and experimental models of kidney disease. Using subtotal nephrectomized cholesterol-fed rats as a model for progressive kidney disease, we examined the effect of 5% dietary fish oil, or a combination of 5% dietary fish oil with 500 IU vitamin E/kg diet or 1% probucol on renal injury. Three-month-old Sprague Dawley rats were fed a control diet (C group) or a cholesterol supplemented (2%) diet (Ch group) containing either fish oil (FO group) or fish oil plus vitamin E (FO+E group) or fish oil plus probucol (FO+P group). After 4 weeks of dietary treatment, the right kidney was electrocoagulated and the left kidney nephrectomized. After 8 weeks, 24-hour urine was collected before sacrifice. No effect of the dietary treatments was noted on serum creatinine, blood urea nitrogen, or proteinuria, except that proteinuria was highest in FO+P group. Rats receiving the cholesterol diets had higher serum low density lipoprotein (LDL) + very low density lipoprotein (VLDL) cholesterol (P < 0.05). In contrast, rats in the FO+P group had the lowest serum total cholesterol and LDL+VLDL cholesterol among all groups. The FO group had 26% lower kidney alpha-tocopherol concentrations than the C group. However, inclusion of vitamin E in the diet (FO+E group) increased the kidney alpha-tocopherol status to a level comparable to that in the C group, whereas inclusion of probucol in fish oil diet (FO+P group) did not improve the kidney alpha-tocopherol status. Rats fed the cholesterol diet had a 2.5-fold higher glomerular segmental sclerosis (GSS) score and 1.5-fold higher glomerular macrophage (GM) subpopulation than the C group. These effects of the cholesterol diet were ameliorated by a fish oil diet (FO group: GSS by 30%, GM by 24%). The inclusion of vitamin E in the fish oil diet (FO+E group) did not further improve the GSS score or GM subpopulation. However, inclusion of probucol in fish oil diet (FO+P group) lowered the GSS score by 73% and reduced GM subpopulation by 83% compared with the Ch group. These remarkable changes can be attributed to the powerful hypocholesterolemic activity of probucol. Our findings indicate that progression of glomerular sclerosis in the rat remnant kidney model of progressive kidney disease can be significantly modulated with fish oil treatment.

Effect of age, breed and dietary omega-6 (n-6): omega-3 (n-3) fatty acid ratio on immune function, eicosanoid production, and lipid peroxidation in young and aged dogs

The focus of this study was to examine the influence of age and diet on various parameters of immune function in young and old Fox Terriers and Labrador Retrievers. Eighteen young and old dogs were utilized for this study. Young and old dogs were fed a basal diet containing an (n-6):(n-3) ratio of 25:1 for sixty days (Phase I). Half of the dogs were then switched to a diet with an (n-6):(n-3) ratio of 5:1, and all were maintained on their respective diets for an additional sixty days (Phase II). Results from these studies revealed an age-associated decline in several immune parameters measured. Both these breeds demonstrated a reduction in sheep red blood cell titers, as well as in their ability to respond to different mitogens. Interestingly, this decline was greater in Fox Terriers, suggesting a decrease in cellular proliferative capacity in lymphocytes isolated from the larger breed. Neither cytokine production or DTH response was affected by age. Diet and breed interactions resulted in a significant increase in T- and B-cell mitogen responsiveness. In contrast, supplementation with n-3 fatty acids did not affect IL-1, IL-6 or TNF-alpha production. Supplementation with n-3 fatty acids resulted in increased PGE3 production from peritoneal macrophages but had no effect on PGE2 production from peripheral blood mononuclear cells or peritoneal macrophages. The n-3 fatty acid supplementation did not influence alpha-tocopherol status although older dogs had significantly lower serum alpha-tocopherol concentrations. Oxidative status of these dogs was assessed by serum levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Feeding an n-3-enriched diet did not affect 4-HNE levels but significantly decreased MDA levels in old dogs. In summary, this study indicates that feeding a diet containing an (n-6):(n-3) fatty acid ratio of 5:1 had a positive, rather than a negative, effect on the immune response of young or geriatric dogs.

Vitamin E treatment of experimental glomerular disease in rats

BACKGROUND

Kidney mesangial cells (MCs) and vascular smooth muscle cells (VSMCs) are closely related in terms of origin, microscopic anatomy, histochemistry, and contractility. This relationship suggests a similarity between kidney glomerular sclerosis and atherosclerosis. Vitamin E appears beneficial in the prevention and treatment of coronary heart disease and it also inhibits the proliferation of VSMCs in vitro. Thus, we investigated the effect of vitamin E on glomerular sclerosis and MC-proliferative glomerulonephritis (GN) in two rat models of glomerular disease.

METHODS

A remnant kidney rat model accelerated with hyperlipidemia was used to examine progressive glomerular sclerosis leading to chronic renal failure. A rat model of MC-proliferative GN was induced by the intravenous administration of absorbed rabbit anti-rat thymocyte serum (ATS).

RESULTS

In the remnant kidney rat model, dietary supplementation with vitamin E (500 IU dl-alpha-tocopheryl acetate/kg) and cholesterol (2%) significantly inhibited glomerular sclerosis and macrophage infiltration in glomeruli relative to controls receiving basal and cholesterol-supplemented diets. In the ATS-induced GN model, glomerular cell proliferation (principally MCs) was lower in rats fed diets supplemented with vitamin E (1000 IU dl-alpha-tocopheryl acetate/kg) compared with controls fed the basal diet only. Although the degree of glomerular macrophage infiltration was similar in both groups, fewer proliferative cell nuclear antigen (PCNA)-positive cells were observed in the vitamin E group, suggesting that MC proliferation was suppressed via the inhibition of intracellular transduction.

CONCLUSIONS

Supplemental dietary vitamin E suppresses MC proliferation and glomerular sclerosis in models of glomerular disease in rats. This action of vitamin E in experimental nephritis suggests the value of clinical trials testing the potential benefit of vitamin E in chronic GN patients.

Dietary conjugated linoleic acid influences the immune response of young and old C57BL/6NCrlBR mice

Aging is associated with a decline in the immune response in mammals. Conjugated linoleic acid (CLA) has been suggested to have immunoenhancing properties. We examined the influence of dietary CLA on the immune response of young and old mice. Forty young (4 mo) and 40 old (22 mo) mice consumed ad libitum diets containing 0 or 1 g CLA /100 g for 8 wk. Splenocytes from half of the mice were isolated to evaluate proliferation to concanavalin A (Con A) (0.5, 1.5, 5.0 mg/L) and phytohemagglutinin A (PHA) (5, 20, 40 mg/L) and lipopolysaccharide (LPS) (5, 15, 30 mg/L), natural killer cell (NK) activity and prostaglandin (PG)E2 and interleukin (IL)-2 production. The remaining mice were used to evaluate in vivo delayed-type hypersensitivity (DTH) skin response. There was a significant decline due to age in response to all three mitogens tested (P < 0. 05). CLA supplementation significantly increased all CLA isomers measured in hepatic neutral lipids and phospholipids (P < 0.05). Young mice fed 1% CLA had greater splenocyte proliferation in response to Con A (0.5 and 5.0 mg/L) and PHA (40 mg/L) (P < 0.05) than young mice fed control diet. Old mice fed 1 g CLA/100 g had significantly higher proliferative response to optimal concentrations of Con A (1.5 mg/L) (P < 0.001) than the mice fed the control diet. Old mice fed the control diet had significantly lower splenocyte IL-2 production than the young mice (P < 0.005). CLA-supplemented young mice had significantly higher splenocyte IL-2 production than those fed the control diet (P < 0.05). CLA had no effect on NK cell activity, PGE2 production or DTH in young or old mice. Further studies are needed to determine the mechanism of CLA-induced enhancement of IL-2 production and T cell proliferation.

The effect of long-term dietary supplementation with antioxidants

The impact of diet and specific food groups on aging and age-associated degenerative diseases has been widely recognized in recent years. The modern concept of the free radical theory of aging takes as its basis a shift in the antioxidant/prooxidant balance that leads to increased oxidative stress, dysregulation of cellular function, and aging. In the context of this theory, antioxidants can influence the primary "intrinsic" aging process as well as several secondary age-associated pathological processes. For the latter, several epidemiological and clinical studies have revealed potential roles for dietary antioxidants in the age-associated decline of immune function and the reduction of risk of morbidity and mortality from cancer and heart disease. We reported that long-term supplementation with vitamin E enhances immune function in aged animals and elderly subjects. We have also found that the beneficial effect of vitamin E in the reduction of risk of atherosclerosis is, in part, associated with molecular modulation of the interaction of immune and endothelial cells. Even though the effects of dietary antioxidants on aging have been mostly observed in relation to age-associated diseases, the effects cannot be totally separated from those related to the intrinsic aging process. For modulation of the aging process by antioxidants, earlier reports have indicated that antioxidant feeding increased the median life span of mice to some extent. To further delineate the effect of dietary antioxidants on aging and longevity, middle-aged (18 mo) C57BL/6NIA male mice were fed ad libitum semisynthetic AIN-76 diets supplemented with different antioxidants (vitamin E, glutathione, melatonin, and strawberry extract). We found that dietary antioxidants had no effect on the pathological outcome or on mean and maximum life span of the mice, which was observed despite the reduced level of lipid peroxidation products, 4-hydroxynonenol, in the liver of animals supplemented with vitamin E and strawberry extract (1.34 +/- 0.4 and 1.6 +/- 0.5 nmol/g, respectively) compared to animals fed the control diet (2.35 +/- 1.4 nmol/g). However, vitamin E-supplemented mice had significantly lower lung viral levels following influenza infection, a viral challenge associated with oxidative stress. These and other observations indicate that, at present, the effects of dietary antioxidants are mainly demonstrated in connection with age-associated diseases in which oxidative stress appears to be intimately involved. Further studies are needed to determine the effect of antioxidant supplementation on longevity in the context of moderate caloric restriction.

Assessment of the safety of supplementation with different amounts of vitamin E in healthy older adults

We showed previously that supplementation for 30 d with 800 IU (727 mg) vitamin E/d did not adversely affect healthy elderly persons. We have now assessed the effects of 4 mo of supplementation with 60, 200, or 800 IU (55, 182, or 727 mg) all-rac-alpha-tocopherol/d on general health, nutrient status, liver enzyme function, thyroid hormone concentrations, creatinine concentrations, serum autoantibodies, killing of Candida albicans by neutrophils, and bleeding time in 88 healthy subjects aged >65 y participating in a double-blind, placebo-controlled trial. No side effects were reported by the subjects. Vitamin E supplementation had no effect on body weight, plasma total proteins, albumin, glucose, plasma lipids or the lipoprotein profile, total bilirubin, alkaline phosphatase, serum aspartate aminotransferase, serum alanine aminotransferase, lactate dehydrogenase, serum urea nitrogen, total red blood cells, white blood cells or white blood cell differential counts, platelet number, bleeding time, hemoglobin, hematocrit, thyroid hormones, or urinary or serum creatinine concentrations. Values from all supplemented groups were within normal ranges for older adults and were not significantly different from values in the placebo group. Vitamin E supplementation had no significant effects on plasma concentrations of other antioxidant vitamins and minerals, glutathione peroxidase, superoxide dismutase, or total homocysteine. There was no significant effect of vitamin E on serum nonspecific immunoglobulin concentrations or anti-DNA and anti-thyroglobulin antibodies. The cytotoxic ability of neutrophils against Candida albicans was not compromised. Thus, 4 mo of supplementation with 60-800 IU vitamin E/d had no adverse effects. These results are relevant for determining risk-to-benefit ratios for vitamin E supplementation.

Disease incidence and longevity are unaltered by dietary antioxidant supplementation initiated during middle age in C57BL/6 mice

The ability of augmented antioxidant consumption to alter disease incidence, lesion burden and/or longevity was studied in adult male C57BL/6 mice. Mice were fed modified AIN76 diet or modified AIN76 supplemented with vitamin E, glutathione (GSH), vitamin E and GSH, melatonin or strawberry extract starting at 18 months of age. All the mice in this study were heavier than reference populations of male C57BL/6 mice fed NIH-07 or NIH-31, which were maintained without a mid-life change in diet. Fatty liver, focal kidney atrophy and proteinacious casts in the renal tubules were observed more frequently in this study population than in the reference populations. Lesion burden and incidence of specific lesions observed amongst the various groups in this study did not differ. There were no differences observed for longevity of any of the study groups. The longevity observed in this study was similar to that previously reported for male C57BL/6 mice. Thus, diet supplementation with antioxidants initiated during middle age did not appear to affect age-associated lesions patterns, lesion burden or longevity for ad libitum fed male C57BL/6 mice.

Effect of vitamin E supplementation on prostaglandin concentrations in aspirin-induced acute gastric injury in aged rats

Nonsteroidal antiinflammatory drugs (NSAIDs), such as aspirin, frequently cause gastric mucosal injury in the elderly. Impairment of prostaglandin synthesis is a crucial step by which aspirin attenuates mucosal defense capacity. Vitamin E has been shown to decrease prostanoid concentrations, which implies an ulceropermissive effect of vitamin E. To assess the effect of vitamin E on aspirin-induced gastric injury and mucosal prostanoid concentrations, 20 male rats aged 20 mo were divided into two groups and fed diets containing either 30 (physiologic requirement) or 500 mg all-rac-alpha-tocopheryl acetate/kg. After 6 wk, all rats received two intragastric doses of aspirin (1.4 mumol/kg body wt). A third group of six animals fed the high-vitamin E diet received a vehicle solution without aspirin. Mucosal samples for vitamin E and prostaglandin E2, 6-keto-prostaglandin F1 alpha, and thromboxane A2 measurements were collected. The prevalence and degree of mucosal lesions were not significantly different among all groups. Rats fed the high-vitamin E diet had significantly higher mucosal vitamin E concentrations than rats fed the low-vitamin E diet. Mucosal concentrations of all three prostanoids were 95% lower in aspirin-treated rats than in controls (P = 0.0001 in all instances). The high-vitamin E diet group had significantly lower mucosal 6-keto-prostaglandin F1 alpha concentrations (P = 0.02) than the low-vitamin E diet group, indicating decreased prostacyclin formation, whereas concentrations of prostaglandin E2 and thromboxane A2 were similar in the aspirin-treated groups. Aspirin markedly reduced mucosal prostanoid concentrations in rats, without apparent effects on gastric injury, whereas vitamin E supplementation significantly reduced mucosal 6-keto-prostaglandin F(1 alpha) concentrations. Nevertheless, vitamin E supplementation did not result in more gastric injury in aspirin-treated rats than in controls.

Short- and long-term beta-carotene supplementation do not influence T cell-mediated immunity in healthy elderly persons

Supplementation of healthy elderly persons with beta-carotene has been considered a way to enhance immune responses. In study 1 the short-term effect of beta-carotene (90 mg/d for 3 wk) on immunity was assessed in a randomized, double-blind, placebo-controlled longitudinal comparison of healthy elderly women. In study 2 the long-term effect of beta-carotene (50 mg every other day for 10-12 y) on immunity was assessed in a randomized, double-blind, placebo-controlled longitudinal comparison of men enrolled in the Physicians' Health Study. Subjects from both studies taking active supplements had significantly greater plasma beta-carotene concentrations than did subjects taking placebo. The pre- to postintervention change in delayed-type hypersensitivity skin test responses between beta-carotene and placebo groups in the short-term study was not significantly different, nor was the response between treatment groups in the long-term study. There were no significant effects due to beta-carotene supplementation on in vitro lymphocyte proliferation, production of interleukin 2, or production of prostaglandin E2 as a result of short- or long-term beta-carotene supplementation. In addition, there were no differences in the profiles of lymphocyte subsets [total T cells (CD3+), T helper cells (CD4+), T cytotoxic-suppressor cells (CD8+), and B cells (CD19+)] due to short- or long-term beta-carotene supplementation, nor were there differences in percentages of CD16+ natural killer cells or activated lymphocytes (cells expressing interleukin 2 transferrin receptor) due to long-term beta-carotene supplementation. Consistent results from these two trials show that beta-carotene supplementation did not have an enhancing or suppressive effect on T cell-mediated immunity of healthy elderly.

A closer look at vitamin E. Can this antioxidant prevent chronic diseases?

Vitamin E, the most effective natural free radical scavenger identified to date, is taking America by storm-and apparently for good reason. Reports of benefits ranging from Improved Immunity to prevention of cancer and cardiovascular disease are appearing regularly. In this article, the authors review the scientific literature to help you evaluate whether patients might benefit from supplemental vitamin E.

Vitamin E supplementation decreases lung virus titers in mice infected with influenza

Effects of vitamin E (E) supplementation on influenza infection were examined in young and old C57BL/6NIA mice fed 30 or 500 ppm of E for 6 weeks and subsequently infected with influenza A/Port Chalmers/1/73 (H3N2). Old mice fed 30 ppm of E had significantly higher lung virus titers on days 2 and 7 after infection than young mice fed 30 ppm of E. Titers on all 3 days were significantly lower in old mice fed 500 ppm of E than in those fed 30 ppm. Significant effects of E on lung virus titers in young mice were observed on only day 5, but E caused more reduction of virus titers in old than in young mice (25-fold vs. 15-fold). An age-associated decline in NK cell activity was restored by 500 ppm of E in old but not young mice. Pulmonary cytotoxic T lymphocyte activity on day 7 was not affected by age or E. These experiments demonstrate that high doses of E significantly enhance influenza viral clearance in aged mice but only modestly affect young mice.

Vitamin E supplementation and in vivo immune response in healthy elderly subjects. A randomized controlled trial

OBJECTIVE

To determine whether long-term supplementation with vitamin E enhances in vivo, clinically relevant measures of cell-mediated immunity in healthy elderly subjects.

DESIGN

Randomized, double-blind, placebo-controlled intervention study.

SETTING AND PARTICIPANTS

A total of 88 free-living, healthy subjects at least 65 years of age.

INTERVENTION

Subjects were randomly assigned to a placebo group or to groups consuming 60, 200, or 800 mg/d of vitamin E for 235 days.

MAIN OUTCOME MEASURES

Delayed-type hypersensitivity skin response (DTH); antibody response to hepatitis B, tetanus and diphtheria, and pneumococcal vaccines; and autoantibodies to DNA and thyroglobulin were assessed before and after supplementation.

RESULTS

Supplementation with vitamin E for 4 months improved certain clinically relevant indexes of cell-mediated immunity in healthy elderly. Subjects consuming 200 mg/d of vitamin E had a 65% increase in DTH and a 6-fold increase in antibody titer to hepatitis B compared with placebo (17% and 3-fold, respectively), 60-mg/d (41% and 3-fold, respectively), and 800-mg/d (49% and 2.5-fold, respectively) groups. The 200-mg/d group also had a significant increase in antibody titer to tetanus vaccine. Subjects in the upper tertile of serum alpha-tocopherol (vitamin E) concentration (>48.4 micromol/L [2.08 mg/dL]) after supplementation had higher antibody response to hepatitis B and DTH. Vitamin E supplementation had no effect on antibody titer to diphtheria and did not affect immunoglobulin levels or levels of T and B cells. No significant effect of vitamin E supplementation on autoantibody levels was observed.

CONCLUSIONS

Our results indicate that a level of vitamin E greater than currently recommended enhances certain clinically relevant in vivo indexes of T-cell-mediated function in healthy elderly persons. No adverse effects were observed with vitamin E supplementation.

Vitamin E inhibits low-density lipoprotein-induced adhesion of monocytes to human aortic endothelial cells in vitro

Monocyte adhesion to human aortic endothelial cells (ECs) is one of the early events in the development of atherogenesis. ECs were used to investigate the role of vitamin E in human monocyte adhesion to ECs in vitro. ECs incubated with 40 to 193 mg/dL of low-density lipoprotein cholesterol (LDL) for 22 hours exhibited increasing dose-dependent adherence for untreated, isolated human monocytes (P < .05). ECs exposed to the highest dose of LDL (193 mg/dL) but pretreated with 19 mumol/L alpha-tocopherol for 24 hours showed a trend to lower adherence for monocytes compared with non-treated ECs (4.4 +/- 1.2% versus 7.6 +/- 1.9%; P = .09). This effect of vitamin E became more significant (P < .05) when ECs were exposed to a lower level of LDL (40 mg/dL) or were pretreated with a higher level of alpha-tocopherol (42 mumol/L) and then exposed to 80 mg/dL LDL. Presupplementation of ECs with 15, 19, and 37 mumol/L alpha-tocopherol significantly (P < .05) reduced monocyte adhesion by 6 +/- 1%, 37 +/- 6%, and 69 +/- 17%, respectively. Levels of soluble intercellular adhesion molecule-1 (sICAM-1), one of the adhesion molecules for monocytes, increased after incubation of ECs with LDL 80 mg/dL (4.7 +/- 0.7 versus 6.4 +/- 1.2 ng/mL, respectively; P < .05). Treatment of ECs with alpha-tocopherol (42 mumol/L) significantly reduced induction of sICAM-1 by LDL to 2.2 +/- 2.3 ng/mL. After exposure to LDL, prostaglandin I2 production by ECs was diminished, whereas presupplementation of ECs with alpha-tocopherol partially reversed the LDL effect. Production of interleukin-1 beta was not detectable when ECs were treated with alpha-tocopherol, LDL, or alpha-tocopherol followed by LDL. Our findings indicate that vitamin E has an inhibitory effect on LDL-induced production of adhesion molecules and adhesion of monocytes to ECs via its antioxidant function and/or its direct regulatory effect on sICAM-1 expression.

Exercise, free radical generation, and aging

Advancing age is associated with profound alterations in body composition and exercise capacity. Skeletal muscle mass declines on average of 6% per decade after age thirty and this change impacts both basal energy requirements and maximal aerobic exercise capacity. While skeletal muscle has one of the highest requirements of all tissues for oxygen, exercise increases total oxygen consumption by approximately 10-fold, causing an increased rate of production of reactive oxygen species (ROS). Biological aging is thought to be influenced by ROS generation and older individuals may be more susceptible to exercise-induced oxidative damage. However, aging is also associated with increases in antioxidant enzymes and controversy still exists as to whether exercise training further upregulates the expression of these free radical scavenging enzymes. Older individuals who participate in regular exercise may have higher requirements for antioxidant vitamins to compensate for the deficit of endogenous antioxidants.

Natural killer cell activity in elderly men is enhanced by beta-carotene supplementation

Natural killer (NK) cell activity has been postulated to be an immunologic link between beta-carotene and cancer prevention. In a cross-sectional, placebo-controlled, double-blind study we examined the effect of 10-12 y of beta-carotene supplementation (50 mg on alternate days) on NK cell activity in 59 (38 middle-aged men, 51-64 y; 21 elderly men, 65-86 y) Boston area participants in the Physicians' Health Study. No significant difference was seen in NK cell activity due to beta-carotene supplementation in the middle-aged group. The elderly men had significantly lower NK cell activity than the middle-aged men; however, there was no age-associated difference in NK cell activity in men supplemented with beta-carotene. beta-carotene-supplemented elderly men had significantly greater NK cell activity than elderly men receiving placebo. The reason for this is unknown; however, it was not due to an increase in the percentage of NK cells, nor to an increase in interleukin 2 (IL-2) receptor expression, nor to IL-2 production. beta-carotene may be acting directly on one or more of the lytic stages of NK cell cytotoxicity, or on NK cell activity-enhancing cytokines other than IL-2, such as IL-12. Our results show that long-term beta-carotene supplementation enhances NK cell activity in elderly men, which may be beneficial for viral and tumoral surveillance.

Fatty acid-related functions

The first recommendations for specific nutrient quantities that must be obtained to support health were made by the US Department of Agriculture before 1939. Hazel Stiebeling was the leader of this effort and the scientific background was published in the Yearbook of Agriculture. The recommendations clearly stated that food must be available to provide the nutrients to support health. The science of nutrition in the United States is engaged in the most thorough review and reexamination of the recommended dietary allowances in at least a generation of nutrition scientists. There is a new awareness of nutrition complexity and the likelihood of identification of new essential nutrients. This meeting was devoted to the search for functional endpoints to reach quantitative estimates of dietary substances needed to support a function. Included in that concept is determining a range of individual needs and identifying factors that alter these needs. We give the rationale for endpoints of fatty acid metabolism related to platelets and the risk of thrombosis, give the rationale for the recommendation for a new nutrient, and show the necessity for including nutrient interaction in the determination of needs for two nutrients.

Carotenoid and tocopherol concentrations in plasma, peripheral blood mononuclear cells, and red blood cells after long-term beta-carotene supplementation in men

To determine the effects of long-term beta-carotene supplementation on concentrations of carotenoids and tocopherols in plasma and in blood cells, fasting blood was collected from 73 randomly selected physicians from the Boston area who are participating in the Physicians Health Study (PHS). The PHS is a randomized, placebo-controlled, double-blind study. In 1982, 22,071 male physicians were assigned to one of four treatments (325 mg aspirin alone, 50 mg beta-carotene alone, both, or neither) every other day. Plasma, peripheral blood mononuclear cells (PBMCs), and red blood cells (RBCs) from physicians who have participated in the study for approximately 12 y were analyzed for carotenoids and tocopherols. Compared with the placebo group, the supplemented group had higher beta-carotene concentrations in plasma (1.73+/-0.16 compared with 0.54+/-0.06 micromol/L0, RBCs (91.5+/-9.7 compared with 31.2+/-4.2 pmol/g hemoglobin), and PBMCs (61.6+/-10.3 compared with 15.5+/-2.5 pmol/10(7) cells). There were no differences in other carotenoids or tocopherols in plasma, RBCs, and PBMCs between these two groups. The beta-carotene concentrations. Plasma cryptoxanthin correlated with both RBC and PBMC cryptoxanthin concentrations but plasma lycopene correlated only with PBMC lycopene concentrations. These data suggest that plasma may not be the best indicator of carotenoid status. Furthermore, long-term beta-carotene supplementation in men results in higher beta-carotene concentrations in plasma, RBCs and PBMCs without lowering concentrations of other carotenoids or tocopherols.

Immunologic effects of marine- and plant-derived n-3 polyunsaturated fatty acids in nonhuman primates

The effect of marine- and plant-derived n-3 polyunsaturated fatty acids (PUFAs) on T cell-mediated immune response was studied in cynomolgus monkeys. Animals were first fed a 14-wk baseline diet; 10 animals were then fed diets containing 1.3% or 3.3% of energy as eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) which the other 10 were fed diets containing 3.5% or 5.3% of energy as alpha-linolenic acid (ALA) for two consecutive 14-wk periods. Both diets significantly decreased the percentage of T cells (except 1.3% EPA + DHA), T helper cells (except 1.3% EPA + DHA and 3.5% ALA), and T suppressor cells. Proliferative response of lymphocytes to T cell mitogens significantly increased after the diet containing 3.3% EPA + DHA. Interleukin 2 production significantly increased after the diets containing 1.3% and 3.3% EPA + DHA. No significant changes in mitogenic response or interleukin 2 production were found after ALA diets. Feeding 1.3% or 3.3% EPA + DHA or 5.3% ALA significantly suppressed prostaglandin E2 production in response to T cell mitogens. Plasma tocopherol concentrations were decreased significantly only in monkeys fed ALA diets. We conclude that after adjustment for the tocopherol concentration, marine-derived n-3 PUFAs but not plant-derived n-3 PUFAs increased T cell-mediated mitogenic response and interleukin 2 production. This is most likely due to diet-induced quantitative differences in cellular fatty acid composition and, thus, in prostaglandin E2 production and tocopherol status.