Aging-related nicotinamide adenine dinucleotide oxidase response to dietary supplementation: the French paradox revisited

Aging-related cell-surface NADH oxidase (arNOX)-specific activities increase with age between age 30 and ages 50-65. The protein is shed and circulates. Activity correlates with a number of aging-related disorders including low-density lipoprotein (LDL) oxidation as a precondition to atherosclerosis as well as oxidation of collagen and elastin as a major contributor to skin aging. arNOX inhibitors formulated for sustained release are capable of maintaining circulating arNOX at low levels with regular use as food supplements formulated with natural compounds. Among the best sources are certain culinary seasonings, all of which are ingredients used extensively in the French kitchen. Their regular use may contribute to an understanding of the nutritional basis for the French Paradox.

LDL resistance to oxidation: Effects of lipid phenotype, autologous HDL and alanine

BACKGROUND

Although LDL resistance to copper-induced oxidation is a time-honoured method, how it is modulated by the physiologic variability of lipid phenotype and what influences the protective action of homologous HDL and exogenous alanine is still unclear.

METHODS

In 159 subjects without severe dyslipidemias, LDL resistance to copper-induced oxidation (lag phase) was measured under standardised conditions, with alanine and with autologous HDL.

RESULTS

Lag phase was normally distributed and averaged 68+/-10 min (range: 40-105 min). Both VLDL-triglycerides (37+/-5, 52+/-7, 59+/-7, 53+/-5 mg/dl, p<0.05) and LDL-triglycerides (27+/-2, 27+/-1, 30+/-2, 35+/-3 mg/dl, p<0.01) increased across quartiles of lag phase. The relative LDL enrichment in triglycerides (triglycerides percent or triglycerides/cholesterol ratio) was strongly related to lag phase (r=0.29 and r=0.31, p<0.0005 for both) independently of age, gender, BMI, and presence of diabetes or hypertension. The protective effect of HDL was variable (+42+/-18 min) and largely dependent on the capacity of HDL to resist oxidation (r=0.69, p<0.0001). Alanine induced a rather constant lag phase prolongation (+32+/-7 min) that was weakly related only to baseline lag phase (r=0.17, p<0.05).

CONCLUSIONS

Relative triglyceride abundance protects LDL from ex-vivo oxidation, HDL particles protect LDL mainly through substrate dilution and alanine probably through a direct anti-oxidant effect.

Supplementation with omega3 polyunsaturated fatty acids and all-rac alpha-tocopherol alone and in combination failed to exert an anti-inflammatory effect in human volunteers

There is growing evidence supporting the importance of inflammation in all stages of atherosclerosis. While both omega-3 polyunsaturated fatty acids (n3PUFA) and the lipid-soluble antioxidant alpha-tocopherol (AT) have been shown to independently have significant anti-inflammatory effects, there is paucity of data examining the effect of n3PUFA alone and in combination with AT on markers of inflammation and monocyte function. Therefore, we tested the effect of n3PUFA alone, all-rac (synthetic) AT alone, and the combination on markers of inflammation and monocyte function. Healthy nonsmoking volunteers were randomly assigned to 1 of 4 groups (n = 20 per group): 1.5 g/d n3PUFA, 800 IU/d AT, 1.5 g n3PUFA + 800 IU/d AT, or placebo in a parallel double-blinded study. Compared to baseline, 12 weeks of supplementation resulted in no changes in plasma lipids regardless of treatment. Plasma AT was significantly increased only in those groups that received AT (P <.0001). Similarly, groups receiving n3PUFA showed a significant increase in plasma docosahexaenoic acid (P <.0001). No significant within- or between-group differences were found for plasma levels of high-sensitivity C-reactive protein (hsCRP). Furthermore, there were no differences in monocyte proinflammatory cytokine release (interleukin [IL]-1beta, tumor necrosis factor [TNF]-alpha and IL-6) after activation with monocyte chemotactic protein-1 (MCP-1). In conclusion, supplementation with n3PUFA and all-rac AT at these doses is not anti-inflammatory.

Circadian temporal organization of lipidic fractions in elderly people. Entrainment to the dietary schedule

BACKGROUND AND AIMS

Changes in some rhythmometric parameters have been reported in the elderly as a consequence of both structural and neurochemical changes occurring in the central nervous system. Since alterations of lipid and lipoprotein metabolism are directly involved in several age-related disorders, the aim of this study was to investigate the circadian temporal organization of some important lipidic fractions (total cholesterol, triacylglycerol, apolipoprotein A1 and B) in physiological aging.

METHODS

Thirty old hospitalized subjects were synchronized for daily activities, sleeping/waking habits, and time/quality of meals. Twenty-four healthy young individuals served as controls. After an overnight fast, samples were taken beginning at 08:00 every 4 hours until 20:00, and every 2 hours from 20:00 to 04:00. Rhythmometric data were analyzed by single and population mean Cosinor analysis, and by ANOVA; the comparison of the rhythm's parameters between elderly and young subjects was carried out by the Mesor test and the amplitude-acrophase using Hotelling's test.

RESULTS

Elderly subjects exhibited statistically significant circadian rhythms for total cholesterol (p<0.00002), triacylglycerol (p<0.000001), apo A-1 (p<0.0013), and apo B (p<O.0104). Young subjects also exhibited statistically significant daily fluctuations for total cholesterol (p<0. 0003), triacylglycerol (p<0. 03), apo A-1 (p<0.002) and apo B (p<0.003). The mean level of apo B rhythm was higher in old subjects than in controls.

CONCLUSIONS

These data suggest that the circadian temporal organization of lipidic fractions is maintained in physiological aging and underline the importance of the feeding schedule as a powerful synchronizer of the daily lipidic profile.

eNOS activity is reduced in senescent human endothelial cells: Preservation by hTERT immortalization

Advanced age is associated with endothelial dysfunction and increased risk for atherosclerosis. However, the mechanisms for these observed effects are not clear. To clarify the association between aging and loss of endothelial function, young human aortic endothelial cells (HAECs), senescent HAECs transfected with control vector, and immortalized HAECs containing human telomerase reverse transcriptase (hTERT) were compared for expression of endothelial nitric oxide synthase (eNOS) and production of NO. To investigate a specific function modulated by endothelial NO, adhesion of monocytes under basal conditions as well as after exposure to TNF-alpha was assessed. A decrease in eNOS mRNA, protein, and activity was observed in endothelial cells at senescence as compared with young HAEC; this effect was blunted in hTERT cells. In all cells, shear stress induced a greater increase in the expression of eNOS protein with the final result being higher levels in hTERT compared with senescent cells. Basal monocyte binding was significantly elevated on aged endothelial cells compared with parental and hTERT cells. Exposure of TNF-alpha resulted in a 2-fold increase in monocyte adhesion in senescent cells, whereas this effect was reduced in cells transfected with hTERT. Prior exposure to fluid flow significantly reduced subsequent monocyte adhesion in all groups. These studies demonstrate that replicative aging results in decreased endothelial expression of eNOS accompanied by enhanced monocyte binding. Stable expression of hTERT results in endothelial cells with a younger phenotype with greater amount of eNOS and NO activity. Thus, telomerase transfection may have important functional consequences on endothelial cells.

In vitro oxidation of low-density lipoprotein in two species of nonhuman primates subjected to caloric restriction

Caloric restriction (CR), which increases longevity and retards age-associated diseases in laboratory rodents, is being evaluated in nonhuman primate trials. CR reduces oxidative stress in rodents and appears to improve risk factors for cardiovascular disease in nonhuman primates. We tested the hypothesis that low-density lipoprotein (LDL) oxidizability is reduced in two monkey species (rhesus and cynomolgus) subjected to chronic CR. In both species, no significant differences occurred between CR and control animals on total, LDL, or high-density lipoprotein (HDL) cholesterol. In rhesus monkeys, triglycerides were higher in controls than CR (139 +/- 23 vs 66 +/- 8 mg/dl,p < .01, respectively). LDL from CR rhesus monkeys was reduced in triglyceride content and molecular weight compared to controls, whereas LDL composition in cynomolgus monkeys was similar in CR and control animals. In keeping with minor deviations in lipids, antioxidants, and LDL composition, no consistent differences in in vitro LDL oxidizability were apparent between CR and controls in either species.

Age-related Increases in Plasma Phosphatidylcholine Hydroperoxide Concentrations in Control Subjects and Patients with Hyperlipidemia

Background: The basal lipid peroxide concentration in the plasma of patients with hyperlipidemia may be related to atherosclerosis. Quantitative determination of lipid peroxides in the plasma is an important step in the overall evaluation of the biochemical processes leading to oxidative injury. Unfortunately, the currently available methods for lipid peroxidation lack specificity and sensitivity.

Methods: Hyperlipidemic patients (44 males and 50 females), ages 12–82 years (mean ± SE, 53 ± 2.3 years for males, 58 ± 2.0 years for females, and 56 ± 14 years for total cases), and normolipidemic volunteers (controls, 32 males and 15 females), ages 13–90 years (49 ± 4 years for males, 65 ± 4 years for females, and 55 ± 24 years for total cases), were recruited in the present study. Plasma phosphatidylcholine hydroperoxide (PCOOH) was determined by chemiluminescence-HPLC (CL-HPLC).

Results: Plasma PCOOH concentrations increased with age in both controls and hyperlipidemic patients. However, the mean plasma PCOOH concentration in patients with hyperlipidemia (331 ± 19 nmol/L; n = 94) was significantly (P &lt;0.001) higher than in the controls (160 ± 65 nmol/L; n = 47). Plasma PCOOH concentrations were similar in three hyperlipidemic phenotypes: hypercholesterolemia (IIa), hypertriglyceridemia (IV), and combined hyperlipidemia (IIb). The mean plasma PCOOH in patients with treatment-induced normalized plasma lipids was 202 ± 17 nmol/L. There was no significant correlation between plasma PCOOH concentration and total cholesterol, triglycerides, or phospholipids in hyperlipidemic patients. For all subjects, there was a significantly positive correlation between plasma PCOOH and each lipid (total cholesterol, P = 0.0002; triglycerides, P = 0.0137; and phospholipids, P &lt;0.0001). Analysis of fatty acids composition of plasma phosphatidylcholine showed significantly low concentrations of n-6 fatty acids moieties (linoleic acid and arachidonic acid) in patients compared with controls.

Conclusions: Our results suggest that an increase in plasma PCOOH in patients with hyperlipidemia may be related to the development and progression of atherosclerosis, particularly in the elderly. Measurement of plasma PCOOH is useful for in vivo evaluation of oxidative stress.

Physiological levels of melatonin contribute to the antioxidant capacity of human serum

This work evaluates whether physiological concentrations of the pineal secretory product melatonin contribute to the total antioxidant status (TAS) of human serum. Day and nighttime serum samples were collected from healthy volunteers ranging from 2 to 89 years of age and used to measure melatonin and TAS. Results showed that both melatonin and TAS in human serum exhibited 24 hr variations with nocturnal peak values at 01:00 hr. Moreover, exposure of volunteers to light at night resulted in clear decreases of both TAS and melatonin. Furthermore, when melatonin was removed from sera collected at night, the TAS value of the sample was reduced to basal daytime values. In aging studies, it was found that nocturnal serum values of TAS and melatonin exhibited maximal values during the first four decades; thereafter, these values decreased as age advanced. In 60-year-old individuals, day/night differences in serum melatonin and TAS levels were clearly diminished, by more than 80%, with these differences being completely abolished in older individuals. Our results suggest that melatonin contributes to the total antioxidative capability of human serum. This antioxidant contribution of melatonin is reduced as age advances correlating with the age-related reduction of melatonin.

Lipoprotein modification and atherosclerosis in aging

The development of extensive atherosclerosis of major arteries of the heart, brain, and lower extremities is a particularly frequent problem in elderly individuals and is responsible for the majority of the cardiovascular morbidity and mortality in this population. Although the frequency and severity of this problem is well recognized, there has been relatively little investigation of the effects of aging on the development of atherosclerosis. Work by a number of investigators over the last 10-15 years has demonstrated that modifications of lipoproteins, resulting from oxidative stress, glycoxidation, formation of AGE, or other processes may play an important role in atherosclerosis. As described in this review, the aging process may enhance lipoprotein modification and atherosclerosis in several ways. Conditions such as hypertension, diabetes, and menopause all increase in frequency with advancing age and may contribute both directly and indirectly to lipoprotein modification and vascular injury.Additionally, in some studies of older animals and humans, there seems to be evidence for greater in vivo oxidative stress. Whether this is a specific consequence of aging and associated medical conditions, or related to differences in dietary fatty acid or antioxidant content or other lifestyle differences is currently unknown. One important consequence of this may be enhanced susceptibility of lipoproteins to oxidation. Additional study of lipoprotein modifications associated with aging is clearly needed, and may provide new insight and solutions to the common problem of atherosclerosis in the elderly.

Relationship between insulin resistance and partially oxidized LDL particles in healthy, nondiabetic volunteers

This study was performed in 36 healthy volunteers to define the relationship between plasma concentrations of partially oxidized low density lipoprotein (poxLDL), plasma glucose and insulin responses to oral glucose, and steady-state plasma glucose (SSPG) concentrations after a 180-minute infusion of somatostatin, insulin, and glucose. The concentration of poxLDL was estimated by determining the amount of conjugated dienes formed during in vitro LDL oxidation in the presence or absence of alanine. Under these conditions, the greater the in vitro antioxidant effect of alanine, the lower the amount of poxLDL that was present in plasma. The results demonstrated that plasma poxLDL concentration was significantly correlated with plasma glucose (r=.53, P<.001) and insulin (r=.43, P<.01) responses, SSPG concentrations (r=.53, P<.001), and plasma triglyceride (r=.42, P<.01) and HDL cholesterol (r=-.50, P<.002) concentrations. Furthermore, these relationships persisted when the data were corrected for differences in age, sex, body mass index, and the ratio of waist to hip girth. Of note, there was no correlation between poxLDL and LDL cholesterol concentration. When SSPG was entered along with age, sex, body mass index, and waist-to-hip ratio in a multiple regression model, SSPG alone was a significant prediction of poxLDL (r-=.37, P<.02). The addition of plasma glucose and insulin responses and triglyceride and HDL cholesterol concentrations increased the r2 to only .47. These results show that the amount of poxLDL in plasma is significantly correlated with insulin resistance (ie, SSPG) and its metabolic consequences.

Receptor- and age-selective effects of dopamine oxidation on receptor-G protein interactions in the striatum

The striatum contains a high concentration of oxidizable dopamine (DA), and the aged organism shows a decreased ability to respond to oxidative stress (OS), making this area extremely vulnerable to free radical insult. To determine the receptor specificity of this putative increase in OS sensitivity, striatal slices from 6- and 24-month-old animals were incubated (30 min, 37 degrees C) in a modified Krebs medium containing 0 to 500 microM DA with or without a preincubation (15 min) in a nitrone trapping agent, 1 or 5 mM alpha-phenyl-n-tert-butyl nitrone (PBN), and changes in low Km GTPase activity (an index of receptor-G protein coupling/uncoupling) assessed in muscarinic, 5-HT1A D1, and D2 receptors stimulated with carbachol, 8 OH-DPAT-HBr, SKF 38393, or quinelorane, respectively. DA exposure induced selective decreases in the stimulated activity in all of these receptor systems, and an overall increase in conjugated dienes (56%) of the young. In the case of carbachol and 8 OH-DPAT-HBr, the DA-induced deficits in GTPase stimulation were seen primarily in the young (61 and 32%, respectively), while DA-induced deficits in quinelorane (D2) stimulation were seen in both age groups. In the case of SKF 38393-stimulation (D1) the DA-induced deficits were higher in the striatal tissue from the old. The DA-induced decreases in carbachol stimulated GTPase activity in the tissue from the young could be prevented by pretreatment with PBN or the DA uptake inhibitor, nomifensin. No effect of nomifensin was seen in the old, because their DA uptake mechanisms were already compromised. These results suggest that although age-related declines in DA uptake may provide some protection against the OS effects in muscarinic or 5-HT1A receptors, other factors may increase the vulnerability of DA neurons to OS, even with reductions in DA uptake.

Vitamin E supplementation in elderly lowers the oxidation rate of linoleic acid in LDL

Oxidation of LDL-linoleic acid (LDL-LA), a major substrate for lipid peroxidation, may be counteracted by the antioxidant vitamin E. In a 3-month randomized double-blind placebo-controlled trial in 83 apparently healthy Dutch elderly, aged 67-85 years, the direct protective effect of 100 IU vitamin E on the rate of oxidized LDL-LA was studied. The oxidation of LDL-LA was measured by its disappearance after a 5-h in vitro Cu-oxidation of LDL isolated from 1 ml plasma. In the vitamin E group, the decrease in oxidized LDL LA of 10.4, (p < 0.05) was significantly different (p < 0.05) from the smaller 4.6% p< 0.01) decrease in the control group. Moreover, within the vitamin E group the decrease was even more marked over tertiles of alpha-tocopherol to LDL-LA ratio with a significant difference in decrease (p < 0.05) from the lowest compared to the highest tertile of, respectively, 18.4% [-24; -2%] (median and range) and 2.0% [-16: 34%]. In conclusion, supplementation with 100 IU vitamin E in elderly is beneficial in lowering the rate of oxidation of LDL LA. The protective effect of vitamin E might best be monitored by using the ratio of alpha-tocopherol to LDL-LA as this reflects the degree of alpha-tocopherol available to protect the amount of LDL-LA present.

Properties of low density lipoproteins relevant to oxidative modifications change paradoxically during aging

Atherosclerosis is a common problem among the elderly. Because lipid peroxidation is considered a contributor to the development of atherosclerosis, we compared oxidative properties of lipoproteins in an otherwise healthy (SENIEUR-classified) aged population (65-74 years) with young controls (18-30 years). Relative amounts of oxidatively altered low density lipoprotein (LDL), estimated by means of an antibody against LDL modified by 4-hydroxynonenal, a product of lipid peroxidation, were increased marginally in serum from the elderly (9.8 vs. 7.4%, P = 0.07). In contrast, isolated LDL from the elderly revealed a decreased susceptibility to in vitro oxidation: the lag time was increased (2.34 vs. 2.10 h, P < 0.01), and the maximal rate of LDL oxidation decreased (0.88 vs. 1.01 O.D./h, P = 0.001). However, there were no age-related changes in lipid composition of native LDL and consumption of fatty acids during in vitro oxidation. The serum concentrations of ascorbic acid and most lipophilic anti-oxidants (the latter expressed per g serum lipids) were significantly decreased in the elderly except tocopherols which tended to be higher. In conclusion, our data reveal paradox age-related alterations of LDL as to its behaviour in oxidation in vivo vs. in vitro.

Plasma oxidizability in Mexican-Americans and non-Hispanic whites

Several lines of evidence support an atherogenic role for oxidized low-density lipoprotein (LDL). Previous studies have suggested that although Mexican-Americans have an increased rate of diabetes, obesity, elevated triglyceride levels, and low high-density lipoprotein (HDL) cholesterol levels, their rates of coronary heart disease (CHD) are similar or possibly lower than in non-Hispanic whites. Mexican-Americans have smaller, denser LDL than non-Hispanic whites. On the basis of this latter observation, we postulated that lipid peroxide (LPO) levels would be increased in Mexican-Americans. We examined the oxidizability of plasma in 50 Mexican-Americans and 50 non-Hispanic whites from the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease, at baseline and after coincubation with a metal-independent system (2'2'-azobis-2-amidinopropane hydrochloride [AAPH]) and a metal-dependent system (Fe2+/H2O2) of oxidation. LPO levels were measured by a modified fluorimetric assay. Vitamin E and plasma fatty acid composition were also determined. We found significantly higher LPO levels at baseline and after AAPH coincubation in Mexican-Americans than in non-Hispanic whites (baseline, 2.75 +/- .09 v 2.07 +/- .09 micromol/L, P < .001; post-AAPH, 5.49 +/- .14 v 5.07 +/-. .04 micromol/L, P = .037). However, no significant ethnic differences were seen after coincubation with Fe2+/H2O2. Diabetes and cigarette-smoking were also associated with higher LPO levels. Mexican-Americans also had lower levels of vitamin E (the predominant lipid-soluble antioxidant in plasma) than non-Hispanic whites, although these differences only partially explained the differences in susceptibility to oxidation. Plasma fatty acids were similar in Mexican-Americans and non-Hispanic whites, suggesting only small differences in diet composition. We conclude that LPO levels are higher in Mexican-Americans than in non-Hispanic whites, and that these results are only partially related to differences in vitamin E levels.