Evaluation of a web-based weight loss intervention in overweight cancer survivors aged 50 years and younger.

PURPOSE: Half of adult cancer survivors under age 50 years are obese. Excess body weight is associated with cancer recurrence, and effective weight loss interventions for younger cancer survivors are needed. Commercially available, online weight loss programmes are readily accessible, but few have been studied in this population. This study employed a single-arm, pre-post intervention (baseline-6 month/baseline-12 month comparisons) to preliminarily explore feasibility, efficacy and safety of an online, commercially available weight loss programme in breast (n = 30) and testicular (n = 16) cancer survivors under age 50 years. METHODS: The intervention included three daily components: exercise, nutritional/behavioural modification strategies and health lessons. Intention-to-treat and completers analyses were conducted. Feasibility was measured by participation (number of participants enrolled/number screened), retention (number of participants attending 6/12 month study visit/number of enrolled) and self-reported adherence rates (average of mean percent adherence to each of the three intervention components). Efficacy was assessed by changes in initial weight (percent weight loss). Safety was assessed by adverse events. RESULTS: The mean participation rate was 42%. The retention rate was 59% at 6 and 49% at 12 months. The adherence rate for all participants (completers/dropouts/lost-to-follow-up) was 50.1% at 6 and 44% at 12 months. Completers reported adherence rates of 68% at 12 months. Study participants lost 5.3% body weight at 12 months; completers lost 9%. Only three unexpected adverse events (unrelated to the intervention) were reported. CONCLUSION: Clinically significant weight loss was observed, although retention rates were low. Findings generally support preliminary feasibility, efficacy and safety of this online weight loss programme, and future randomized control trials should be explored.

Prasugrel vs. clopidogrel in acute coronary syndrome patients treated with prasugrel.

WHAT IS KNOWN AND OBJECTIVE: Current guidelines recommend a combination of clopidogrel and aspirin for management of patients who have experienced an acute coronary syndrome (ACS). Additional antiplatelet agents have been recently approved. Few comparative effectiveness studies are available for these new agents. Accordingly, we evaluated effect on time to hospital admission and resource utilization (number of hospitalizations, ER visits and outpatient visits) of prasugrel vs. clopidogrel in prasugrel-treated patients as assessed in a matched cohort. METHODS: Based on the Truven Health Analytics MarketScan database from 01 January 2009 through 31 July 2012, a retrospective prasugrel-clopidogrel matched cohort was created. Inferences for average treatment effect over 1 and 12 months on time to hospitalization and resource utilization were performed by (i) frequentist Kaplan-Meier estimation with a Cox proportional hazard model and Lin's cost history method for censored resource utilization outcomes and (ii) Bayesian discrete-time hazard and negative binomial models. RESULTS AND DISCUSSION: The 10,963 matched pairs were well balanced on baseline characteristics. Frequentist analyses of time to hospital admission over 365 days and mean all-cause resource utilization over 30 and 365 days showed no statistical differences between prasugrel and clopidogrel (P-values > 0·05). Based on Bayesian analysis of time to admission over 12 months, there was positive evidence of equivalence (0·987 probability of equivalence at a 10% equivalence margin and a Bayes factor of 0·611). Although the frequentist analyses for number of all-cause hospitalizations showed a lack of a significant difference at Months 1 and 12, the Bayesian data analysis showed positive evidence of superiority of clopidogrel at Month 1 (Bayes factor: 5·369); however, at Month 12, there was little evidence of superiority of one treatment over the other (Bayes factor: 0·422). WHAT IS NEW AND CONCLUSION: Using frequentist and Bayesian data analyses, in prasugrel-treated patients, clopidogrel was equivalent to prasugrel for time to hospital admission over 12 months and there was positive evidence that it was superior to prasugrel for number of hospitalizations over the first month of treatment.

Incidence of MSDs and neck and back pain among logging machine operators in the southern U.S.

There are limited data about the incidence and prevalence of musculoskeletal disorders (MSDs) among loggers in the southern U.S. despite the risk factors associated with these occupations. Risk factors are both personal (age, body mass index, etc.) and job-related (awkward postures, repetitive hand and foot movements, vibration, etc.). A survey was conducted to estimate the incidence of self-reported pain and diagnosed MSDs and to study the relationship with known risk factors. Respondents were loggers attending training and continuing education classes. Respondents were asked to identify personal attributes, machine use, awkward postures, repetitive movements, and recent incidence of pain and medical diagnoses. All were male with an average age of 44 (range of 19-67) and an average body mass index of 31.3. Most were machine operators (97%) who have worked in the logging industry for an average of 22.9 years. Most machines identified were manufactured within the past ten years (average machine age 6.7 years). For machine operators, 10.5% (16) reported an MSD diagnosis, 74.3% (113) reported at least mild back pain, and 71.7% (109) reported at least mild neck pain over the past year. Further analysis attempted to identify an association between personal attributes, machine use, posture, and pain. Risk factors related to machine use may be biased since most survey respondents had considerable choice or control in working conditions, as they were firm owners and/or supervisors.

An approach to the assessment of risk from chronic radiation to populations of European lobster, Homarus gammarus (L.).

The basic principles underlying a four-discrete age group, logistic, growth model for the European lobster Homarus gammarus are presented and discussed at proof-of-concept level. The model considers reproduction, removal by predation, natural death, fishing, radiation and migration. Non-stochastic effects of chronic low linear energy transfer (LET) radiation are modelled with emphasis on (99)Tc, using three endpoints: repairable radiation damage, impairment of reproductive ability and, at higher dose rates, mortality. An allometric approach for the calculation of LD(50/30) as a function of the mass of each life stage is used in model calibration. The model predicts that at a dose rate of 1 Gy day(-1), lobster population reproduction and survival become severely compromised, leading eventually to population extinction. At 0.01 Gy day(-1), the survival rate of an isolated population is reduced by 10%, mainly through loss of fecundity, comparable to natural migration losses. Fishing is the main ecological stress and only dose rates in the range 0.03-0.1 Gy day(-1) can achieve discernible effects above it. On the balance of radiation and other ecological stresses, a benchmark value of 0.01 Gy day(-1) is proposed for the protection of lobster populations. This value appears consistent with available information on radiation effects in wildlife.

Formal total synthesis of (+/-)-gamma-lycorane and (+/-)-1-deoxylycorine using the [4+2]-cycloaddition/rearrangement cascade of furanyl carbamates.

The total syntheses of gamma-lycorane and (+/-)-1-deoxylycorine were accomplished using an intramolecular Diels-Alder cycloaddition of a furanyl carbamate as the key step. The initially formed [4+2]-cycloadduct undergoes nitrogen-assisted ring opening followed by deprotonation/reprotonation of the resulting zwitterion to give a rearranged hexahydroindolinone. The stereochemical outcome of the IMDAF cycloaddition has the side arm of the tethered alkenyl group oriented syn with respect to the oxygen bridge. The key intermediate used in both syntheses corresponds to hexahydroindolinone 20. Removal of the t-Boc group in 20 followed by reaction with 6-iodobenzo[1,3]dioxole-5-carbonyl chloride afforded enamide 22. Treatment of this compound with Pd(OAc)(2) employing the Jeffrey modification of the Heck reaction provided the galanthan tetracycle 24 in good yield. Compound 24 was subsequently converted into (+/-)-gamma-lycorane using a four-step procedure to establish the cis-B,C-ring junction. A radical-based cyclization of the related enamide 33 was used for the synthesis of 1-deoxylycorine. Heating a benzene solution of 33 with AIBN and n-Bu(3)SnH at reflux gave the tetracyclic compound 38 possessing the requisite trans fusion between rings B and C in good yield. After hydrolysis and oxidation of 38 to 40, an oxidative decarboxylation reaction was used to provide the C(2)(-)C(3)(-)C(12) allylic alcohol unit characteristic of the lycorine alkaloids. The resulting enone was eventually transformed into (+/-)-1-deoxylycorine via known synthetic intermediates.

Reconsidering mortality compression and deceleration: an alterative model of mortality rates.

In this research we develop a model of mortality rates that parameterizes mortality deceleration and compression, permits hypothesis tests for change in these parameters over time, and allows for formal gender comparisons. Our model fits mortality data well across all adult ages 20-105 for 1968-1992 U.S. white data, and the results offer some confirmation of findings of mortality research using conventional methods. We find that the age at which mortality deceleration begins is increasing over time, that decompression of mortality is occurring, and that these trends vary substantially across genders, although male and female mortality patterns appear to be converging to some extent.

Success and future of demography: the role of data and methods.

Demography typifies paradigmatic success; that is, cumulative scientific work that has provided useful perspectives on a set of important questions. This success can be traced partly to the core subject matter of demography, which is relatively conducive to quantitative, observational science. The development of demography was further aided by extrinsic factors, such as the import of its data for government administration, for business purposes, and the import of demographic questions for social problems and public policy. These observations make suspect any simple projection of demography's success into the future or the transport of its experience to other disciplines.

Plasma thiols inhibit hemin-dependent oxidation of human low-density lipoprotein.

Oxidative modification of human low-density lipoprotein (LDL) renders it atherogenic. Previous studies demonstrated that plasma thiols promote oxidation of LDL by free ferric iron (Fe3+). The current study investigated effects of plasma thiols on oxidation of LDL by hemin, a physiological Fe3+-protoporphyrin IX complex thought to be capable of initiating LDL oxidation in vivo. In contrast to free Fe3+ which is incapable of oxidizing LDL in the absence of an exogenous reductant, hemin readily promoted LDL oxidation. During incubation of LDL (0.2 mg of protein/ml) with hemin (10 microM) at 37 degrees C for 6 h, thiobarbituric acid-reactive substances (TBARS), a marker of lipid oxidation, increased from 0.3 (+/-0.1) nmol/mg of LDL protein to a maximal concentration of 45.8 (+/-5.2) nmol/mg of LDL protein. Under the same experimental conditions, lipid-conjugated dienes, another marker of lipid oxidation, increased from non-detectable to near-maximal levels of 78-187 nmol/mg of LDL protein, and lipoprotein polyunsaturated fatty acyl-containing cholesteryl ester content decreased to 15-36% of that present in native (i.e. unoxidized) LDL. Continued incubation of LDL with hemin for up to 24 h resulted in no further significant alterations in lipoprotein levels of TBARS, lipid-conjugated dienes, and cholesteryl esters. In addition to these chemical modifications indicative of lipoprotein oxidation, agarose gel electrophoretic analysis indicated that exposure of LDL to hemin resulted in conversion of the lipoprotein to an atherogenic form as evidenced by its increased anodic electrophoretic mobility. Addition of physiological concentrations of plasma thiols (either cysteine, homocysteine or reduced glutathione; 1-100 microM, each) inhibited hemin-mediated oxidation of LDL. Thus, whereas the maximal TBARS concentration was achieved following 6 h of incubation of LDL with hemin alone, addition of thiol extended the time required to attain maximal TBARS concentration to > or = 12 h. Similar antioxidant effects of thiols on formation of lipid-conjugated dienes, loss of cholesteryl esters, and lipoprotein anodic electrophoretic mobility were also observed. However, all thiols were not equally effective at inhibiting hemin-dependent LDL oxidation. Thus, whereas reduced glutathione was most effective at inhibiting hemin-dependent LDL oxidation, an intermediate effect was observed for homocysteine, and cysteine was least effective. The inhibition of hemin-mediated LDL oxidation by plasma thiols reported here confirms a previous observation that, under certain conditions, thiols can function as antioxidants, but contrasts with the previously documented pro-oxidant effect of the same thiols on oxidation of LDL by free Fe3+. These contrasting effects of plasma thiols on hemin- and free Fe3+-mediated LDL oxidation indicate that, in vivo, the ability of thiols to function as either anti- or pro-oxidants during LDL oxidation may, at least in part, be determined by the type of oxidant stress to which the lipoprotein is exposed.

Caregiving networks of elderly persons: variation by marital status.

Using data from the 1982 National Long-Term Care Survey, this study examines the relationship between marital status and two dimensions of caregiving networks, size and composition. Results indicate that widowed and never married people have helping networks that are larger than those of married people. Diversity across marital statuses in sources of assistance is revealed in analyses of two measures of caregiving network composition: (a) having more kin than nonkin helpers and (b) presence of specific helpers (adult children, siblings, friends, and formal helpers). Moreover, gender interacts with marital status to influence the composition of caregiving networks.

Reliability of measurements obtained with a modified functional reach test in subjects with spinal cord injury.

BACKGROUND AND PURPOSE: The primary purpose of this study was to determine whether the Functional Reach Test (FRT) could be modified to provide reliable measurements of sitting balance. A secondary purpose was to determine whether the test could be used to measure differences among levels of spinal cord injury. SUBJECTS: Thirty male subjects with spinal cord injuries were divided into into three groups based on injury type. Group 1 consisted of subjects with C5-6 tetraplegia, group 2 consisted of subjects with T1-4 paraplegia, and group 3 consisted of subjects with T10-12 paraplegia. METHODS: Subjects sat on similar mat tables (tables varied based on what was available at a given clinic) against the same backboard, set at 80 degrees. During two sessions, forward reach was measured with a yardstick, with a 10-minute break between sessions. RESULTS: Intraclass correlation coefficients (3,2) were high and varied from .85 to .94. Post hoc testing revealed that differences occurred between groups 1 and 3 and groups 2 and 3, but not between groups 1 and 2. CONCLUSION AND DISCUSSION: Test-retest reliability was high with modification of the FRT with a single rater. The measurements reflected differences among levels of lesion. Further study is needed to determine normal values for all levels of lesion, relationships to functional outcomes, and effects of equipment on sitting balance. The modified FRT appears to provide reliable measurements of sitting balance in nonstanding persons with spinal cord injuries.

Vascular superoxide dismutase deficiency impairs endothelial vasodilator function through direct inactivation of nitric oxide and increased lipid peroxidation.

Nitric oxide (NO) and superoxide are both constitutive products of the endothelium. Because NO is readily inactivated by superoxide, the bioactivity of endothelium-derived NO (EDNO) is dependent on local activity of superoxide dismutase (SOD). We examined the effects of chronic inhibition of copper-zinc SOD (CuZnSOD) using a rat model of dietary copper restriction. Male weanling Sprague-Dawley rats were fed a Cu-deficient diet and received either no Cu replacement (Cu-deficient) or Cu in the drinking water (Cu-sufficient). Compared with Cu-sufficient animals, Cu-deficiency was associated with a 68% reduction in CuZnSOD activity and a 58% increase in vascular superoxide as estimated by lucigenin chemiluminescence (both P < .05). Compared with Cu-sufficient animals, arterial relaxation in the thoracic aorta from Cu-deficient animals was 10-fold less sensitive to acetylcholine, a receptor-dependent EDNO agonist, but only 1.5-fold less sensitive to A23187, a receptor-independent EDNO agonist, and only 1.25-fold less sensitive to authentic NO (all P < .05). In contrast, acute inhibition of CuZnSOD with 10 mM diethyldithiocarbamate produced a more uniform reduction in sensitivity to acetylcholine (8-fold), A23187 (10-fold), and NO (4-fold; all P < .001). Cu-deficient animals demonstrated a 2.5-fold increase in plasma-esterified F2-isoprostanes, a stable marker of lipid peroxidation, that correlated inversely with arterial relaxation to acetylcholine (R = -.83; P < .0009) but not A23187 or authentic NO. From these findings, we conclude that chronic inhibition of CuZnSOD inhibits EDNO-mediated arterial relaxation through two mechanisms, one being direct inactivation of NO and the other being lipid peroxidation that preferentially interrupts receptor-mediated stimulation of EDNO.

Physiological thiol compounds exert pro- and anti-oxidant effects, respectively, on iron- and copper-dependent oxidation of human low-density lipoprotein.

The effects of thiol compounds on oxidation of human low-density lipoprotein (LDL, 0.2 mg of protein/ml) by Cu2+ or Fe3+ (10 microM, each) were investigated in an in vitro system. L-Cysteine (CYS, 25 microM-1 mM) inhibited Cu2+-dependent, but facilitated Fe3+-dependent, oxidation of LDL in a dose-dependent manner. D,L-Homocysteine (HCY, 1 mM) and glutathione (GSH, 1 mM) similarly inhibited Cu2+-dependent, while facilitating Fe3+-dependent, oxidation of LDL. However, the effectiveness of these thiols (CYS, HCY, and GSH; 1 mM each) at mediating either Cu(2+)- or Fe3+-dependent LDL oxidation was not equivalent. Thus, Cu2+-dependent oxidation of LDL was most effectively inhibited by GSH, an intermediate effect was observed with HCY, and CYS was least effective. In contrast, a reversal of this pattern was observed for facilitation of Fe3+-dependent oxidation of LDL, with CYS being most effective and GSH being least effective. Interestingly, although the disulfides cystine and homocystine (0.5 mM, each) were without effect on either Cu(2+)- or Fe3+-dependent LDL oxidation, both glutathione disulfide (GSSG, 0.5 mM) and methionine (1 mM), an S-methylated derivative of HCY, inhibited Cu2+-dependent oxidation of LDL. However, neither GSSG nor methionine had any effect on Fe3+-dependent oxidation of LDL. Thus, while a free (reduced) thiol group is important for stimulation of Fe3+-dependent oxidation of LDL by CYS, HCY, and GSH, inhibition of Cu2+-dependent oxidation of LDL by these compounds seems to be thiol-independent. Our results show that thiol compounds differentially mediate Cu(2+)- and Fe3+-dependent LDL oxidation, an important early event in atherogenesis. Mediation of metal ion-dependent LDL oxidation by thiol compounds may have important implications for the etiology of atherosclerosis and may help explain the recent epidemiologic observation that plasma HCY concentration is an independent risk factor for cardiovascular disease.

Mechanisms of metal ion-dependent oxidation of human low density lipoprotein.

Although either copper or iron is essential for oxidation of human low density lipoprotein (LDL) by vascular cells, the mechanism is unknown. In our experiments copper- and iron-mediated LDL oxidation was found to proceed by different mechanisms. Oxidation of LDL by iron requires superoxide and proceeds by a hydroxyl radical-independent mechanism involving reduction of iron from the ferric to the ferrous form. In contrast, copper-mediated LDL oxidation involves direct reduction of copper from the cupric to the cuprous form by LDL.

Ascorbic acid and atherosclerotic cardiovascular disease.

In this chapter, we have briefly reviewed the current scientific knowledge of the role of vitamin C in the prevention of atherosclerosis and its associated clinical manifestations. There is good evidence from animal studies that vitamin C can slow the progression of experimental atherosclerosis. Most of these studies, however, were done either in guinea pigs, using ascorbic acid depletion, or in cholesterol-fed rabbits, using ascorbic acid supplementation. Both animal models have limitations, as guinea pigs are not a well-established (nor well-studied) model of atherosclerosis, and rabbits develop atherosclerosis at high serum beta-VLDL cholesterol levels, and in addition can synthesize ascorbic acid. In contrast, humans develop atherosclerosis spontaneously and readily at moderately elevated serum LDL cholesterol levels and have lost the ability to synthesize ascorbic acid. Thus, the animal studies discussed, although quite promising and suggestive of an anti-atherogenic effect of ascorbic acid, need to be expanded to primates before more definitive conclusions can be drawn. Similar to the animal data, the current evidence from epidemiological studies on the role of vitamin C in the prevention of CVD is inconclusive, with some studies showing a very strong correlation between increased vitamin C intake and incidence of CVD events and other studies showing no correlation at all. Studies on CVD risk factors indicate that vitamin C may moderately decrease total serum cholesterol levels, increase HDL levels, and exert a hypotensive effect. These findings are particularly intriguing and should be pursued vigorously in basic research studies to elucidate biological mechanisms. In addition, it appears that large placebo-controlled, double-blind, randomized trials of vitamin C supplementation (without simultaneous supplementation with vitamin E) in populations with a wide range of vitamin C body levels are needed in order to confirm or refute a role for vitamin C in the prevention of CVD. Unfortunately, no such trials are currently being conducted. The possible mechanisms by which ascorbic acid may affect the development of atherosclerosis and the onset of acute coronary events include effects on arterial wall integrity related to biosynthesis of collagen and GAGs, altered cholesterol metabolism mediated by vitamin C-dependent conversion of cholesterol to bile acids, and effects on triglyceride levels via modulation of lipoprotein lipase activity. A particularly intriguing possible mechanism for the anti-atherogenic effect of vitamin C is prevention of atherogenic, oxidative modification of LDL. Numerous in vitro studies have demonstrated that ascorbic acid strongly inhibits LDL oxidation by a variety of mechanisms. The potential effects of ascorbic acid on platelet function and EDRF metabolism are particularly intriguing, as they might have widespread consequences for the prevention of atherosclerotic lesion development as well as acute clinical events. Thus, both metabolic and antioxidant functions may contribute to the possible reduction of CVD risk by vitamin C.

Increase in circulating products of lipid peroxidation (F2-isoprostanes) in smokers. Smoking as a cause of oxidative damage.

BACKGROUND: It has been hypothesized that the pathogenesis of diseases induced by cigarette smoking involves oxidative damage by free radicals. However, definitive evidence that smoking causes the oxidative modification of target molecules in vivo is lacking. We conducted a study to determine whether the production of F2-isoprostanes, which are novel products of lipid peroxidation, is enhanced in persons who smoke. METHODS: We measured the levels of free F2-isoprostanes in plasma, the levels of F2-isoprostanes esterified to plasma lipids, and the urinary excretion of metabolites of F2-isoprostanes in 10 smokers and 10 nonsmokers matched for age and sex. The short-term effects of smoking (three cigarettes smoked over 30 minutes) and the effects of two weeks of abstinence from smoking on levels of F2-isoprostanes in the circulation were also determined in the smokers. RESULTS: Plasma levels of free and esterified F2-isoprostanes were significantly higher in the smokers (242 +/- 147 and 574 +/- 217 pmol per liter, respectively) than in the nonsmokers (103 +/- 19 and 345 +/- 65 pmol per liter; P = 0.02 for free F2-isoprostanes and P = 0.03 for esterified F2-isoprostanes). Smoking had no short-term effects on the circulating levels of F2-isoprostanes. However, the levels of free and esterified F2-isoprostanes fell significantly after two weeks of abstinence from smoking (250 +/- 156 and 624 +/- 214 pmol per liter, respectively, before the cessation of smoking, as compared with 156 +/- 67 and 469 +/- 108 pmol per liter after two weeks' cessation; P = 0.03 for free F2-isoprostanes and P = 0.02 for esterified F2-isoprostanes). CONCLUSIONS: The increased levels of F2-isoprostanes in the circulation of persons who smoke support the hypothesis that smoking can cause the oxidative modification of important biologic molecules in vivo.

Reduction of copper, but not iron, by human low density lipoprotein (LDL). Implications for metal ion-dependent oxidative modification of LDL.

Cell-mediated oxidative modification of human low density lipoprotein (LDL), most likely an important early step in atherosclerosis, requires redox active metal ions such as copper or iron. We have previously shown that iron-dependent, in contrast to copper-dependent, oxidative modification of LDL requires superoxide, a physiological reductant. In the present study, we sought to explain these discrepant results. LDL was incubated at 37 degrees C with Cu2+ (10 microM) and bathocuproine (BC, 360 microM), an indicator molecule which specifically complexes Cu+, but not Cu2+. In a time- and concentration-dependent manner, LDL reduced Cu2+ to Cu+. An LDL concentration as low as 10 micrograms of protein/ml (about 20 nM) reduced about 7 microM Cu2+ within 1 h of incubation. Complexation of the Cu+ formed under these conditions with BC significantly inhibited oxidative modification of LDL, as assessed by agarose gel electrophoresis. Preincubation of LDL with N-ethylmaleimide had no effect on the rate and extent of Cu2+ reduction nor LDL oxidation, indicating that free sulfhydryl groups associated with apolipoprotein B are not involved. Addition of either superoxide dismutase or catalase or increasing the alpha-tocopherol content of LDL from 11.8 +/- 3.0 to 24.4 +/- 2.8 nmol/mg of protein also had no significant effect on the kinetics of Cu2+ reduction by LDL. In contrast, incubation of LDL with Fe(3+)-citrate (10 microM) and the indicator bathophenanthroline (BP, 360 microM) resulted in no significant Fe2+ formation, even at LDL concentrations as high as 200 micrograms of protein/ml. However, incubation of LDL with Fe(3+)-citrate and an enzymatic source of superoxide led to rapid formation of Fe2+ and consequent oxidative modification of LDL. Addition of BP inhibited iron-mediated LDL oxidation under these conditions. Our results indicate that reduced metal ions are important mediators of LDL oxidation, and that LDL specifically reduces Cu2+, but not Fe3+. These data, therefore, help explain why copper, in addition to being chemically more reactive, is more potent than iron at mediating LDL oxidation.

The effect of iron overload on rat plasma and liver oxidant status in vivo.

There is ample evidence implicating reactive oxygen species in a number of human degenerative diseases such as atherosclerosis and haemochromatosis. Although lipid peroxidation underlies many of the toxic effects of oxidative stress, there is a lack of a sensitive and reliable method for its assessment in vivo. To understand the implications of oxidative stress in vivo, we have used dietary iron overload (IO) in the rat. Oxidant status in these animals was determined by assessing depletion of endogenous antioxidants and formation of various lipid peroxidation products, including acylated F2-isoprostanes, a novel class of free-radical-derived prostaglandin-F2-like compounds. IO led to a significant decrease in the concentration of the antioxidants alpha-tocopherol and ascorbic acid in plasma, and alpha-tocopherol, beta-carotene and ubiquinol-10 in liver. Whereas there was no significant lipid peroxidation in plasma, hepatic F2-isoprostane levels were moderately but significantly increased in IO. In addition, IO caused a significant increase in plasma total and high-density lipoprotein cholesterol levels, an effect that was correlated with depletion of plasma ascorbic acid but not alpha-tocopherol. The data demonstrate that IO causes lipid metabolism disturbances and oxidative stress which is associated with substantial depletion of endogenous antioxidants and moderate lipid peroxidative damage.

Formation of non-cyclooxygenase-derived prostanoids (F2-isoprostanes) in plasma and low density lipoprotein exposed to oxidative stress in vitro.

F2-isoprostanes are prostaglandin F2-like compounds that are known to be formed in vivo by free radical oxidation of arachidonyl-containing lipids, and their plasma levels have been suggested as indicators of in vivo oxidative stress. As oxidation of LDL, a likely causal factor in atherosclerosis, involves lipid peroxidation, we investigated whether F2-isoprostanes are formed in plasma and LDL exposed to oxidative stress, and how F2-isoprostane formation is related to endogenous antioxidant status. In plasma exposed to aqueous peroxyl radicals, lipid hydroperoxides and esterified F2-isoprostanes were formed simultaneously after endogenous ascorbate and ubiquinol-10 had been exhausted, despite the continued presence of urate, alpha-tocopherol, beta-carotene, and lycopene. In isolated LDL exposed to aqueous peroxyl radicals or Cu2+, consumption of endogenous ubiquinol-10 and alpha-tocopherol was followed by rapid formation and subsequent breakdown of lipid hydroperoxides and esterified F2-isoprostanes, and a continuous increase in LDL's electronegativity, indicative of atherogenic modification. In Cu(2+)-exposed LDL, the decrease in esterified F2-isoprostane levels was paralleled by the appearance of free F2-isoprostanes, suggesting that hydrolysis by an LDL-associated activity had occurred. Our data suggest that F2-isoprostanes are useful markers of LDL oxidation in vivo. As F2-isoprostanes are potent vasoconstrictors and can modulate platelet aggregation, their formation in LDL demonstrated here may also have important implications for the etiology of cardiovascular disease.