Effect of short-term hormone therapy on oxidative stress and endothelial function in African American and Caucasian postmenopausal women

Chronic intermittent hypoxia-induced hypertension: the impact of sex hormones

Obstructive sleep apnea, a common form of sleep-disordered breathing, is characterized by intermittent cessations of breathing that reduce blood oxygen levels and contribute to the development of hypertension. Hypertension is a major complication of obstructive sleep apnea that elevates the risk of end-organ damage. Premenopausal women have a lower prevalence of obstructive sleep apnea and cardiovascular disease than men and postmenopausal women, suggesting that sex hormones play a role in the pathophysiology of sleep apnea-related hypertension. The lack of protection in men and postmenopausal women implicates estrogen and progesterone as protective agents but testosterone as a permissive agent in sleep apnea-induced hypertension. A better understanding of how sex hormones contribute to the pathophysiology of sleep apnea-induced hypertension is important for future research and possible hormone-based interventions. The effect of sex on the pathophysiology of sleep apnea and associated intermittent hypoxia-induced hypertension is of important consideration in the screening, diagnosis, and treatment of the disease and its cardiovascular complications. This review summarizes our current understanding of the impact of sex hormones on blood pressure regulation in sleep apnea with a focus on sex differences.

Acute beetroot juice reduces blood pressure in young Black and White males but not females

A complex interplay of social, lifestyle, and physiological factors contribute to Black Americans having the highest blood pressure (BP) in America. One potential contributor to Black adult's higher BP may be reduced nitric oxide (NO) bioavailability. Therefore, we sought to determine whether augmenting NO bioavailability with acute beetroot juice (BRJ) supplementation would reduce resting BP and cardiovascular reactivity in Black and White adults, but to a greater extent in Black adults. A total of 18 Black and 20 White (∼equal split by biological sex) young adults completed this randomized, placebo-controlled (nitrate (NO3-)-depleted BRJ), crossover design study. We measured heart rate, brachial and central BP, and arterial stiffness (via pulse wave velocity) at rest, during handgrip exercise, and during post-exercise circulatory occlusion. Compared with White adults, Black adults exhibited higher pre-supplementation resting brachial and central BP (Ps ≤0.035; e.g., brachial systolic BP: 116(11) vs. 121(7) mmHg, P = 0.023). Compared with placebo, BRJ (∼12.8 mmol NO3-) reduced resting brachial systolic BP similarly in Black (Δ-4±10 mmHg) and White (Δ-4±7 mmHg) adults (P = 0.029). However, BRJ supplementation reduced BP in males (Ps ≤ 0.020) but not females (Ps ≥ 0.299). Irrespective of race or sex, increases in plasma NO3- were associated with reduced brachial systolic BP (ρ = -0.237, P = 0.042). No other treatment effects were observed for BP or arterial stiffness at rest or during physical stress (i.e., reactivity); Ps ≥ 0.075. Despite young Black adults having higher resting BP, acute BRJ supplementation reduced systolic BP in young Black and White adults by a similar magnitude, an effect that was driven by males.

Strategies to decrease oxidative stress biomarker levels in human medical conditions: A meta-analysis on 8-iso-prostaglandin F2α

The widespread detection of elevated oxidative stress levels in many medical conditions has led to numerous efforts to design interventions to reduce its effects. Efforts have been wide-ranging, from dietary changes to administration of antioxidants, supplements, e.g., omega-3-fatty acids, and many medications. However, there is still no systemic assessment of the efficacy of treatments for oxidative stress reduction across a variety of medical conditions. The goal of this meta-analysis is, by combining multiple studies, to quantitate the change in the levels of the popular oxidative stress biomarker 8-iso-prostaglandin F2α (8-iso-PGF2α) after a variety of treatment strategies in human populations. Nearly 350 unique publications with 180 distinct strategies were included in the analysis. For each strategy, the difference between pre- or placebo and post-treatment levels calculated using Hedges' g value of effect. In general, administration of antibiotics, antihyperlipidemic agents, or changes in lifestyle (g = - 0.63, - 0.54, and 0.56) had the largest effect. Administration of supplements, antioxidants, or changes in diet (g = - 0.09, - 0.28, - 0.12) had small quantitative effects. To fully interpret the effectiveness of these treatments, comparisons to the increase in g value for each medical condition is required. For example, antioxidants in populations with coronary artery disease (CAD) reduce the 8-iso-PGF2α levels by g = - 0.34 ± 0.1, which is quantitatively considered a small effect. However, CAD populations, in comparison to healthy populations, have an increase in 8-iso-PGF2α levels by g = 0.38 ± 0.04; therefore, the overall reduction of 8-iso-PGF2α levels is ≈ 90% by this treatment in this specific medical condition. In conclusion, 8-iso-PGF2α levels can be reduced not only by antioxidants but by many other strategies. Not all strategies are equally effective at reducing 8-iso-PGF2α levels. In addition, the effectiveness of any strategy can be assessed only in relation to the medical condition investigated.

Effects of melatonin and dexpanthenol on antioxidant parameters when combined with estrogen treatment in ovariectomized rats

The purpose of the study was to assess whether it is possible to reduce the oxidative damage using antioxidant agents combined with hormone replacement therapy after menopause. In this prospective experimental study, 50 mature female Wistar albino rats weighing 270-310 g were used. Rats were divided into the following six groups: (1) Ovx group (n = 7): the animals underwent bilateral ovariectomy. No drug was administered following bilateral ovariectomy. (2) Ovx + E 2 group (n = 7): bilateral ovariectomy + 17β-estradiol (100 μg/kg/day); (3) Ovx + E 2 + MT5 group (n = 7): bilateral ovariectomy + 17β-estradiol (100 μg/kg/day) + melatonin (5 mg/kg/day); (4) Ovx + E 2 + MT20 group (n = 7): bilateral ovariectomy + 17β-estradiol (100 μg/kg/day) + melatonin (20 mg/kg/day); (5) Ovx + E 2 + Dxp250 group (n = 7): bilateral ovariectomy + 17β-estradiol (100 μg/kg/day) + dexpanthenol (250 mg/kg/day); (6) Ovx + E 2 + Dxp500 group (n = 7): bilateral ovariectomy + 17β-estradiol (100 μg/kg/day) + dexpanthenol (500 mg/kg/day), and the activity of these antioxidative enzymes and oxidative stress products were measured. Enzymatic activity levels of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase(GSH-Px), and glutathione reductase and levels of free radicals (malondialdehyde (MDA) and nitric oxide) were both analyzed. We observed an increase in the level of GSH activity, but no significant differences in levels of CAT, SOD, and GSH-Px enzymatic activity and in levels of free radical MDA following 17β-estradiol or additional antioxidant treatment (melatonin or dexpanthenol). Despite the present study indicating that the addition of melatonin and dexpanthenol into the hormone replacement therapy regimen may contribute to the antioxidant effect of estrogen, the existence of limited data in this field indicates that further studies are warranted.

17β-estradiol levels and oxidative balance in a population of pre-, peri-, and post-menopausal women

BACKGROUND

The high incidence of various diseases observed in post-menopausal women has been widely associated to the decline of 17β-estradiol (E2) occurring in correspondence of menopausal transition. One of the mechanisms suggested to explain this link takes into account the ability of E2 to counteract oxidative stress (OS) which is believed to play an important role in several pathogenic processes.

AIM

To investigate whether stages of women's life characterized by different levels of E2 influence OS.

SUBJECTS AND METHODS

We conducted a cross sectional study of OS markers in 159 women subdivided in 65 pre-menopausal, 36 peri-menopausal, and 58 post-menopausal classified according to the Staging of Reproductive Aging Workshop (STRAW) criteria. E2, follicle-stimulating hormone, and markers of OS including hydroperoxides, thiols, uric acid, total and residual antioxidant power, were assessed.

RESULTS

After adjustment for covariates, only total antioxidant power was significantly different according to menopausal status (p <0.01), with lower value in pre- with respect peri- and post-menopausal women. No significant correlations between E2 levels and OS markers were detected.

CONCLUSIONS

Endogen E2, and, consequently, its decline during menopausal transition, is not a determinant factor for OS.

Endogenous nitric oxide formation correlates negatively with circulating matrix metalloproteinase (MMP)-2 and MMP-9 levels in black subjects

Deficient formation of endogenous nitric oxide (NO) contributes to cardiovascular diseases, and this may be associated with increased circulating levels of matrix metalloproteinase-9 (MMP-9), as previously shown in white subjects. Because interethnic differences exist with respect to risk factors, prevalence, and severity of cardiovascular diseases, we designed this study to examine whether the circulating levels of nitrites (a marker of endogenous NO formation) are associated with the plasma levels of MMP-9 and MMP-2 in healthy black subjects. We studied 198 healthy subjects self-reported as blacks not taking any medications. Venous blood samples were collected and plasma and whole blood nitrite levels were measured using an ozone-based chemiluminescence assay. Plasma MMP-2 and MMP-9 levels were determined by gelatin zymography. We found a positive correlation between plasma MMP-9 and MMP-2 levels (P < 0.0001, rs = 0.556). Interestingly, we found a negative relationship between the plasma MMP-9 levels and the plasma or whole blood nitrites levels (P = 0.04, rs = -0.149; and P < 0.0001, rs = -0.349, respectively). In parallel, we found similar negative relationships between plasma MMP-2 levels and plasma or whole blood nitrites levels (P = 0.02, rs = -0.172; and P < 0.0001, rs = -0.454, respectively). This is the first study to show that endogenous nitric oxide formation correlates negatively with the circulating levels of both MMP-2 and MMP-9 in black subjects. Our findings suggest a mechanistic link between deficient NO formation and increased MMPs levels, which may promote cardiovascular diseases.

Impact of serum estradiol on postprandial lipemia, oxidative stress, and inflammation across a single menstrual cycle

BACKGROUND

An abrupt rise in circulating lipids, oxidative stress, and inflammatory biomarkers is a common finding after ingestion of a high-fat meal. Estradiol, typically provided via hormone replacement therapy to postmenopausal women, has been reported to possess lipidemic, antioxidant, and antiinflammatory properties, all of which may minimize postprandial oxidative stress.

OBJECTIVE

The purpose of this study was to compare the postprandial triglyceride (TG), oxidative stress, and inflammatory responses after a lipid meal in menstruating women during the early follicular (days 1-3) and preovulatory (day 14) phases of the menstrual cycle.

METHODS

Healthy normolipidemic women (fasting blood TG, <200 mg/dL) with regular menstrual cycles reported to the Cardiorespiratory/Metabolic Laboratory at the University of Memphis, Memphis, Tennessee (October-December 2008) and consumed an identical lipid meal (heavy whipping cream and water) on 2 separate days during the menstrual cycle. Blood samples were collected premeal and 1, 2, 4, and 6 hours postmeal, then assayed for TG, malondialdehyde (MDA), hydrogen peroxide, Trolox equivalent antioxidant capacity (TEAL), nitrate/nitrite, and C-reactive protein (CRP). The AUC was calculated for each variable, and a 2 (menstrual cycle phase) x 5 (time) ANOVA with Tukey post hoc testing was also conducted. Estradiol concentration was measured in premeal samples for verification of cycle phase.

RESULTS

Ten women (mean [SD] age, 29 [11] years; 8 white, 2 black; body mass index, 22 [3] kg/m(2)) participated in the study. Despite a higher serum estradiol concentration on day 14 (113 [56] pg/mL) compared with the early follicular phase (61 [34] pg/mL), the TG, oxidative stress, and inflammatory AUC responses to feeding were not significantly different. TG (P = 0.03), MDA (P = 0.02), and hydrogen peroxide (P < 0.001) were significantly increased in response to feeding (time effect), whereas nitrate/nitrite was decreased (P = 0.01). TEAC and CRP were not significantly affected.

CONCLUSIONS

These data indicate that estradiol, at the concentrations noted in the present study, had no significant effect on postprandial TG or biomarkers of oxidative stress or inflammation in a sample of young, healthy women. It is possible that a greater divergence in circulating estradiol may be needed for significant differences to be detected, as may be the case with chronic hormone replacement therapy in postmenopausal women.

Antioxidants: benefits and risks for long-term health

The oxidative modification hypothesis postulates that oxidative stress is one of the major factors in aging and the development of age-related disorders, including cardiovascular diseases. In this scenario, the oxidative modification of lipids, proteins and nucleic acids in vascular walls contributes to the etiology of cardiovascular disease, implying that consumption or therapeutic use of antioxidants could prevent the onset of such pathological disorders. Because of this, a number of studies have been conducted to address the question of whether cardiovascular diseases can be modulated by antioxidant treatment or consumption. Although some of the earliest data, collected in animal studies and epidemiologic studies have shown a measure of success, numerous clinical trials indicate that this approach is of minimal or no benefit. These conclusions represent a challenge to design more sensitive antioxidant trials in order to confirm or alter these conclusions. The focus of this review is on the benefits and disadvantages associated with the use of antioxidants, such as vitamins C and E, polyphenols, or antioxidant therapies, including hormone replacement therapy and iron reduction therapy, on overall vascular health.

Ischemia/reperfusion unveils impaired capacity of older adults to restrain oxidative insult

Age independently predicts poor outcome in a variety of medical settings, including sepsis, trauma, severe burns, and surgery. Because these conditions are associated with oxidative stress, we hypothesized that the capacity to constrain oxidative insult diminishes with age, leading to more extensive oxidative damage during trauma. To test this hypothesis, we used suprasystolic inflation of an arm blood pressure cuff to safely induce localized forearm ischemia/reperfusion (I/R) and quantified plasma F(2)-isoprostane (IsoP) levels in serial blood samples. Before I/R, IsoP levels were similar in young (20-33 years) and older adults (62-81 years). After I/R challenge, the magnitude and duration of increased IsoP levels was significantly greater in older adults. Because aging is associated with declining levels of sex hormones that contribute to the regulation of antioxidant enzyme expression, we then examined the response to I/R in older women receiving hormone replacement therapy and found that these women did not manifest the amplified IsoP response found in untreated older women. These findings demonstrate that aging impairs the ability to restrain oxidative damage after an acute insult, which may contribute to the increased vulnerability of older adults to traumatic conditions and establishes a useful method to identify effective interventions to ameliorate this deficiency.

The nitroxide tempol has similar antioxidant effects as physiological levels of 17beta-oestradiol in reversing ovariectomy-induced oxidative stress in mice liver and kidney

OBJECTIVE

Oestrogen defciency increases oxidative stress postmenopause, while tempol is an intracellular radical scavenger that interferes with the formation or effects of many radicals. We aimed to investigate the effects of oestrogen and tempol on oxidative stress parameters in the kidney and liver of ovariectomized mice.

MATERIAL AND METHODS

Forty 8-week-old female Bald/c mice were divided into five groups: sham-operated, ovariectomized mice without treatment, ovariectomized mice treated with tempol, ovariectomized mice treated with 17beta-oestradiol and ovariectomized mice treated with 17beta-oestradiol and tempol. Oxidative stress in liver and kidney tissues was investigated by measuring 2-thiobarbituric acid reactive substances (TBA-RS), reduced glutathione, myeloperoxidase, superoxide dismutase and catalase levels.

RESULTS

TBA-RS levels were increased and reduced glutathione, myeloperoxidase, superoxide dismutase levels were decreased in the tissues of ovariectomized mice. This effect of ovariectomy on oxidative stress parameters was opposed significantly by the administration of tempol and 17beta-oestradiol either alone or in combination. Ovariectomy reduced the kidney catalase levels, but the effect was not statistically significant (p>0.05). On the other hand, catalase levels were elevated significantly in all treatment groups compared to those of the ovariectomized group (p<0.05).

CONCLUSION

These study findings demonstrate that tempol significantly opposes the oxidative stress generated by ovariectomy. This effect, which is evident in remote tissues such as liver and kidney, is comparable to that of physiological levels of oestradiol.

Impact of Long-term Hormone Replacement Therapy onIn vivoandIn vitroMarkers of Lipid Oxidation

Postmenopausal hormone replacement therapy (HRT) with estrogen has been suggested to inhibit oxidation of low-density lipoprotein (LDL) in vitro, but progestins may oppose this effect. We studied whether estrogen HRT and combined HRT with estrogen and progestin differ in their ability to resist in vivo and in vitro oxidation of lipids. Study group included 15 women on oestradiol valerate (mean age 56 years, treatment duration 10.5 years) and 15 women on combined HRT with oestradiol valerate and levonorgestrel (mean age 58 years, treatment duration 11.3 years). In addition to lipid and apolipoprotein concentrations, the lagtime of LDL to oxidation, the rate of the propagation phase and the maximum concentration of conjugated dienes were recorded as indices of LDL susceptibility to copper-induced oxidation in vitro. As an in vivo marker of oxidative stress we measured 24-h excretion of urinary 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha). All measurements were done after long-term HRT (baseline), after 4 weeks pause and again 3 weeks after reintroduction of HRT. High-density lipoprotein (HDL) cholesterol and apolipoprotein AI concentrations were significantly higher and LDL to HDL ratio significantly lower after long-term oestradiol valerate therapy than after combined therapy. Simultaneously, the triglyceride and lipoprotein (a) levels were higher in the estrogen group. Susceptibility of LDL to oxidation and the level of 8-iso-PGF2alpha were similar in both groups at all measurement points, and treatment group was not a statistically significant determinant of these markers at baseline. According to these results, estrogen and combined HRT do not differ in their abilities to oppose LDL oxidation in vitro or systemic oxidative stress in vivo, but have differential effects on blood lipids.

Effects of oral contraception with ethinylestradiol and drospirenone on oxidative stress in women 18-35 years old

BACKGROUND

Oral contraceptives (OCs) with estrogens and progestins may affect oxidative stress (OS) status.

STUDY DESIGN

A group of 32 women using oral contraceptives (OCU) containing 0.03 mg ethinylestradiol and 3 mg drospirenone have been compared to a matched control group of 30 noncontraception users (NCU). Blood levels of antioxidants, trace elements and markers of lipid peroxidation were assessed by biochemical methods. A microarray analysis of whole blood mRNA levels of 200 genes involved in OS-dependant pathway was also performed.

RESULTS

Levels of zinc, vitamin E and antibodies to oxidized low-density lipoproteins (LDLs) were not significantly different between the two groups. On the other hand, significant increases in the mean levels of lipid peroxides (+176%, p<.001), oxidized LDLs (+145%, p<.002), copper (+103%, p<.001), Cu/Zn ratio (+100%, p<.001) and a significant decrease in the mean level of beta-carotene (-41%, p<.01) were observed in the OCU compared to NCU. There was a highly significant positive correlation between the lipid peroxide levels and the copper-to-zinc ratio. From the 200 genes tested by microarray, one coding for HSP70 was significantly up-regulated (log(2) fold change=+ 0.45, p<.02) and one coding for inducible nitric oxide synthase significantly down-regulated (log(2) fold change=-0.24, p<.05) in the OCU compared to the NCU.

CONCLUSIONS

The recently introduced combination of ethinylestradiol and drospirenone induced the heightening of lipid peroxidation correlated with high levels of copper, a situation that could be associated with increased cardiovascular risk.

Biomarkers of Psychological Stress in Health Disparities Research

Psychological stress can contribute to health disparities in populations that are confronted with the recurring stress of everyday life. A number of biomarkers have been shown to be affected by psychological stress. These biomarkers include allostatic load, which is a summary measure of the cumulative biological burden of the repeated attempts to adapt to daily stress. Allostatic load includes effects on the hypothalamic-pituitary axis, the sympathetic nervous system and the cardiovascular system. These in turn affect the immune system via bidirectional signaling pathways. Evidence is also building that psychological stress, perhaps via heightened inflammatory states, can increase oxidative stress levels and DNA damage. The inter-relationships of ethnicity, genotype, gene expression and ability to adequately mitigate stress response are just starting to be appreciated. The need to conduct these studies in disadvantaged populations is clear and requires methods to address potential logistical barriers. Biomarkers can help characterize and quantify the biological impact of psychological stress on the etiology of health disparities.

Racial differences in nitric oxide-dependent vasorelaxation

Along with the growing heterogeneity of the American population, ethnic/racial disparity is becoming a clear health issue in the United States. The awareness of ethnic/racial disparities has been growing because of considerable data gathered from recent clinical and epidemiological studies. These studies have highlighted the importance of addressing these differences in the diagnosis and treatment of various diseases potentially according to race. It is becoming particularly clear that there is a 2- to 3-fold racial difference in certain cardiovascular diseases (eg, preeclampsia) associated with dysfunctional nitric oxide-mediated vasodilation. In this review, the authors summarize the current literature on racial disparities in nitric oxide-mediated vasodilation in relation to cardiovascular health with an emphasis on vascular nitric oxide bioavailability as a balance between production via endothelial nitric oxide synthase and degradation through reactive oxygen species. The major hypotheses postulated on the biological basis of these differences are also highlighted.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Influence of hormone replacement therapy on blood antioxidant enzymes in menopausal women

BACKGROUND

Natural loss of estrogen occurring in menopausal process may contribute to various health problems many of them possibly related to oxidative stress. Hormone replacement therapy (HRT) is the most common treatment to attenuate menopausal disturbances. This study was aimed at evaluating the influence of HRT on the activity of antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; and glutathione peroxidase, GPx) and lipid peroxidation (thiobarbituric acid reactive substances, TBARS) in menopausal women.

METHODS

Blood antioxidant enzyme activities were determined in premenopausal (n=18) and in postmenopausal healthy women without (n=21) or with (n=19) HRT (mean ages: 47, 59, and 57 years, respectively).

RESULTS

TBARS, CAT, and GPx activity were not significantly different among the groups of study. However, SOD activity was significantly lower in postmenopausal women without HRT (0.68+/-0.04 U/mg Hb) when compared both to premenopausal women (0.91+/-0.04 U/mg Hb) and to postmenopausal women with HRT (0.89+/-0.07 U/mg Hb). SOD activity was positively correlated to the duration of HRT in the postmenopausal groups (r=0.33, p<0.05).

CONCLUSIONS

HRT antagonizes the decrease of SOD activity that occurs after menopause, suggesting that HRT may play a beneficial role in the protection against oxidative stress.

Therapeutic dosages of raloxifene do not modify myeloperoxidase and F2α-isoprostane levels in postmenopausal women

We investigated the effect of a therapeutic dose of raloxifene on the plasma levels of myeloperoxidase and F2alpha-isoprostanes, two markers of oxidative stress recently described as reliable indicators of coronary heart disease. Contrary to changes described in the literature for estrogens (E), raloxifene did not modify the levels of either myeloproxidase or F2alpha-isoprostanes after 3 or 6 months of treatment.

Effect of a Soymilk Supplement Containing Isoflavones on Urinary F2 Isoprostane Levels in Premenopausal Women

Epidemiological studies have associated soy diets with reduced risk of breast and some other cancers, and oxidative cellular damage may contribute to the development of these and other diseases. We tested the effect of a soymilk supplement rich in isoflavones on a measure of cellular lipid peroxidation in a controlled feeding study. Eight premenopausal women consumed a constant diet that included soymilk containing 113-207 mg/day total isoflavones and 4 mo later a constant soy diet low (<5 mg/day) in isoflavones, both for a complete menstrual cycle. The average daily urinary excretions of daidzein and genistein were 24.6 +/- 10.1 and 9.2 +/- 6.1 mg/day, respectively, during the high-isoflavone soy diet and were below the detection limit during the low-isoflavone diet. F2 isoprostane 8-iso-PGF-2alpha excretion varied widely within and between subjects, and the group mean was not significantly different during the high- and low-isoflavone soy diet (7.67 +/- 1.13 and 8.65 +/- 1.18 nmol/12 h, mean +/- SD, respectively). However, individual changes in 8-iso-PGF-2alpha between the two soymilk drinks were significantly associated with age (r = -0.87; P = 0.006) and several measures of isoflavone exposure, namely, daidzein dose (r = 0.81; P = 0.015), combined daidzein and genistein dose (r = 0.77; P = 0.03), and total urinary excretion of isoflavones (daidzein, genistein, and equol) (r = 0.71; P = 0.05). The findings suggest that soy isoflavones may reduce lipid peroxidation in an age-dependent manner, with greater effects in older women, and with lower doses of isoflavones.

Factors regulating isoprostane formation in vivo

Discovery of the F2-isoprostanes, a group of prostaglandin F2-like compounds biosynthesized from arachidonic acid nonenzymatically, has uncovered a new and novel facet of free radical biology. Some of these compounds are bioactive and thus may mediate adverse effects associated with oxidant stress. F2-Isoprostanes have also been shown to be reliable biomarkers of lipid peroxidation. Factors influencing their formation and metabolism have been studied to some extent, although much remains to be determined. The purpose of this review is to summarize our current knowledge of conditions that modulate endogenous generation of these compounds. Isoprostanes have a wide daily variation in secretion in humans. Although normal levels can be defined, these compounds are found in increased concentrations in various pathophysiological states, including ischemia-reperfusion injury, atherosclerosis, and diabetes, and in experimental conditions of oxidative stress and inflammation. Alterations in isoprostane biosynthesis, secretion, and excretion in normal physiology and in pathophysiological states are due to the various types of endogenous and exogenous regulatory mechanisms that control the availability of precursors required for isoprostane synthesis, such as dietary and tissue arachidonic acid content, oxygen concentration, and the generation of various free radical species. Selected aspects of issues related to isoprostane formation and metabolism in vivo will be examined herein.