Isoprostanes and isofurans as non-traditional risk factors for cardiovascular disease among Canadian Inuit

Associations of dietary, lifestyle, other participant characteristics, and oxidative balance scores with plasma F2-isoprostanes concentrations in a pooled cross-sectional study

PURPOSE

Plasma F₂-isoprostanes (FiP) concentration, a reliably measured, valid, systemic oxidative stress biomarker, has been associated with multiple health-related outcomes; however, associations of most individual dietary and lifestyle exposures with FiP are unclear, and there is no reported oxidative balance score (OBS) comprising multiple dietary and/or lifestyle components weighted by their associations with FiP.

METHODS

To investigate cross-sectional associations of dietary and lifestyle characteristics with plasma FiP concentrations, we used multivariable general linear models to compare adjusted mean FiP concentrations across categories of dietary nutrient and whole-food intakes and lifestyle characteristics in two pooled cross-sectional studies (n = 386). We also developed equal-weight and weighted OBS (nutrient- and foods-based dietary OBS, lifestyle OBS, and total OBS), and compared adjusted mean FiP concentrations across OBS tertiles.

RESULTS

Among men and women combined, adjusted mean FiP concentrations were statistically significantly, proportionately 28.1% higher among those who were obese relative to those who were normal weight; among those in the highest relative to the lowest total nutrient intake tertiles, FiP concentrations were statistically significantly lower by 9.8% for carotenes, 13.6% for lutein/zeaxanthin, 10.9% for vitamin C, 12.2% for vitamin E, 11.5% for glucosinolates, and 5% for calcium. Of the various OBS, the weighted OBS that combined total nutrient intakes and lifestyle exposures was most strongly associated with FiP concentrations: among those in the highest relative to the lowest total OBS, mean FiP concentrations were statistically significantly 29.7% lower (P < 0.001).

CONCLUSION

Multiple dietary and lifestyle characteristics, individually, and especially collectively, may contribute to systemic oxidative stress.

Cardiovascular disease risk factors and oxidative stress among premenopausal women

Oxidative stress is one hypothesized mechanism linking anthropometric, behavioral, and medical risk factors with cardiovascular disease (CVD). We evaluated cross-sectional associations between CVD risk factors and biomarkers of oxidative stress, and investigated these biomarkers as predictors of incident diabetes and hypertension among premenopausal women. F₂-isoprostane (F₂-IsoP) and metabolite (15-F_2t-IsoP-M), reliable biomarkers of oxidative stress, were measured in urine samples collected at enrollment from 897 premenopausal women (ages 35-54) enrolled in the Sister Study cohort without a CVD history. Blood pressure, waist circumference, and body mass index (BMI) were measured at enrollment by trained study personnel. Diabetes and cigarette smoking were self-reported via enrollment questionnaires. Over a maximum follow-up of 11.5 years, participants self-reported incident diabetes and hypertension diagnoses on mailed questionnaires. In cross-sectional analyses, both F₂-IsoP and 15-F_2t-IsoP-M were positively associated with BMI, waist circumference, diastolic blood pressure, and current smoking. F₂-IsoP was elevated among those with diabetes, and 15-F_2t-IsoP-M increased with higher systolic blood pressure. Prospective analyses suggested an increased hypertension risk among those with elevated 15-F_2t-IsoP-M (highest vs. lowest quartile: hazard ratio=2.34; 95% CI: 1.20-4.56). Our results suggest that urinary F₂-IsoP and 15-F_2t-IsoP-M are positively associated with adiposity measures, blood pressure, and cigarette smoking. Further investigation is warranted to evaluate 15-F_2t-IsoP-M as a predictor of hypertension.

The State of Affairs for Cardiovascular Health Research in Indigenous Women in Canada: A Scoping Review

Cardiovascular disease (CVD) is the leading cause of death among Indigenous peoples in Canada. As rates of CVD rise, the impacts among the growing population of Indigenous women will emerge as an important health issue. The objective of this scoping review was to advance the state of knowledge about cardiovascular health research in Indigenous women in Canada. Five databases and grey literature (non-peer reviewed works) were searched to identify all studies that reported on the prevalence, pathophysiology, diagnosis, treatment, or interventions for CVD among adult Indigenous women in Canada, including First Nations, Métis, and Inuit. Searching identified 3194 potential articles; 61 of which were included. The most commonly researched topics were the prevalence of CVD, hypertension, and dyslipidemia. Rates of CVD and associated mortality among Indigenous women appear to have surpassed those of their nonindigenous counterparts. Very little research has examined the pathophysiology, diagnosis, and treatment of CVD. Gaps in the research identified the need for sex-based analyses, comparison with nonindigenous women, comprehensive longitudinal data, assessment of diagnosis criteria, development and evaluation of cardiovascular health interventions, and a better understanding of the role of culture and traditions in the prevention and treatment of CVD among Indigenous women. Although comprehensive CVD data are lacking, rates of CVD among Indigenous women in Canada are rising and are nearing or surpassing those of nonindigenous women. This review serves as a call to action to seek further research on the pathophysiology, diagnosis, and treatment of CVD among Indigenous women from across Canada.

The association between three major physiological stress systems and oxidative DNA and lipid damage

BACKGROUND

Increased activity of the three major physiological stress systems (immune-inflammatory system, hypothalamic-pituitary-adrenal-axis [HPA-axis], and autonomic nervous system [ANS]) is part of the pathophysiology of various somatic and psychiatric diseases. Oxidative damage is a key mechanism in both ageing and disease. Elucidating the relationship between these stress systems and oxidative damage would contribute to the understanding of the role of physiological stress in disease. This study therefore investigates associations between various measures of physiological stress and oxidative DNA (8-hydroxy-2'-deoxyguanosine, 8-OHdG) and lipid (F2-isoprostanes) damage.

METHODS

Plasma 8-OHdG and F2-isoprostanes were measured using LC-MS/MS in 2858 subjects (aged 18-65). Plasma inflammation markers, salivary cortisol and ANS markers (three for each stress system) were determined. Linear regression analyses were adjusted for sociodemographics, sampling factors and medication.

RESULTS

8-OHdG was positively associated with all inflammation markers (β=0.047-0.050, p<0.01), evening cortisol (β=0.073, p<0.001), and unexpectedly with low respiratory sinus arrhythmia (RSA) reflecting low ANS stress (β=0.073, p<0.001). F2-isoprostanes were associated with higher C-reactive protein (β=0.072, p<0.001), high ANS stress reflected in heart rate (β=0.064, p<0.001) and RSA (β=-0.076, p=0.001), but not with cortisol. Analyses investigating the cumulative impact of the stress systems demonstrated that the number of systems with ≥1 marker in the high risk quartile showed a positive linear trend with both 8-OHdG (p=0.030) and F2-isoprostanes (p=0.009).

CONCLUSION

This large-scale study showed that markers of inflammation, the HPA-axis and ANS are associated with oxidative DNA damage. Oxidative lipid damage is associated with inflammation and the ANS. Increased physiological stress across systems is associated with increasing oxidative damage in a dose-response fashion.

Effect of Coenzyme Q10 on Biomarkers of Oxidative Stress and Cardiac Function in Hemodialysis Patients: The CoQ10 Biomarker Trial

BACKGROUND

Oxidative stress is highly prevalent in patients with end-stage renal disease and is linked to excess cardiovascular risk. Identifying therapies that reduce oxidative stress has the potential to improve cardiovascular outcomes in patients undergoing maintenance dialysis.

STUDY DESIGN

Placebo-controlled, 3-arm, double-blind, randomized, clinical trial.

SETTING & PARTICIPANTS

65 patients undergoing thrice-weekly maintenance hemodialysis.

INTERVENTION

Patients were randomly assigned in a 1:1:1 ratio to receive once-daily coenzyme Q10 (CoQ10; 600 or 1,200mg) or matching placebo for 4 months.

OUTCOMES

The primary outcome was plasma oxidative stress, defined as plasma concentration of F2-isoprotanes. Secondary outcomes included levels of plasma isofurans, levels of cardiac biomarkers, predialysis blood pressure, and safety/tolerability.

MEASUREMENTS

F2-isoprostanes and isofurans were measured as plasma markers of oxidative stress, and N-terminal pro-brain natriuretic peptide and troponin T were measured as cardiac biomarkers at baseline and 1, 2, and 4 months.

RESULTS

Of 80 randomly assigned patients, 15 were excluded due to not completing at least 1 postbaseline study visit and 65 were included in the primary intention-to-treat analysis. No treatment-related major adverse events occurred. Daily treatment with 1,200mg, but not 600mg, of CoQ10 significantly reduced plasma F2-isoprostanes concentrations at 4 months compared to placebo (adjusted mean changes of -10.7 [95% CI, -7.1 to -14.3] pg/mL [P<0.001] and -8.3 [95% CI, -5.5 to -11.0] pg/mL [P=0.1], respectively). There were no significant effects of CoQ10 treatment on levels of plasma isofurans, cardiac biomarkers, or predialysis blood pressures.

LIMITATIONS

Study not powered to detect small treatment effects; difference in baseline characteristics among randomized groups.

CONCLUSIONS

In patients undergoing maintenance hemodialysis, daily supplementation with 1,200mg of CoQ10 is safe and results in a reduction in plasma concentrations of F2-isoprostanes, a marker of oxidative stress. Future studies are needed to determine whether CoQ10 supplementation improves clinical outcomes for patients undergoing maintenance hemodialysis.

The novelty of phytofurans, isofurans, dihomo-isofurans and neurofurans: Discovery, synthesis and potential application

Polyunsaturated fatty acids (PUFA) are oxidized in vivo under oxidative stress through free radical pathway and release cyclic oxygenated metabolites, which are commonly classified as isoprostanes and isofurans. The discovery of isoprostanes goes back twenty-five years compared to fifteen years for isofurans, and great many are discovered. The biosynthesis, the nomenclature, the chemical synthesis of furanoids from α-linolenic acid (ALA, C18:3 n-3), arachidonic acid (AA, C20:4 n-6), adrenic acid (AdA, 22:4 n-6) and docosahexaenoic acid (DHA, 22:6 n-3) as well as their identification and implication in biological systems are highlighted in this review.

Sociodemographic and Lifestyle Determinants of Plasma Oxidative Stress Markers 8-OHdG and F2-Isoprostanes and Associations with Metabolic Syndrome

Background. Oxidative stress is increasingly important in health research. Therefore, it is necessary to understand which factors determine basal oxidative stress. This study examines the associations of various determinants with markers of oxidative DNA and lipid damage: 8-hydroxy-2'-deoxyguanosine (8-OHdG) and F2-isoprostanes. Methods. Data are from the Netherlands Study of Depression and Anxiety; 1117 subjects (18-65 years) without a current psychiatric diagnosis. Multivariable regression analyses were conducted with plasma levels of 8-OHdG and F2-isoprostanes (measured by LC/MS-MS) including sociodemographic, lifestyle, and sampling variables. Associations with metabolic syndrome (MetS) and chronic disease were examined. Results. 8-OHdG and F2-isoprostanes were weakly correlated (r = 0.06, p = 0.045). Both were positively associated with age and cotinine (cigarette exposure); 8-OHdG was lower in females and after longer sample storage. F2-isoprostanes were higher in females, alcohol users, and in samples collected in spring and lower in supplement users and those with more education. Both markers were lower in fasting subjects. F2-isoprostanes, not 8-OHdG, were positively associated with MetS. Conclusion. The weak correlation between 8-OHdG and F2-isoprostanes suggests they reflect specific aspects of oxidative stress. Both markers are associated with a range of sociodemographic, lifestyle, and sampling determinants which should be considered in future research. F2-isoprostanes are associated with MetS.

Association of plasma F2-isoprostanes and isofurans concentrations with erythropoiesis-stimulating agent resistance in maintenance hemodialysis patients

Background

In patients undergoing maintenance hemodialysis (HD), hyporesponsiveness to erythropoiesis stimulating agents (ESAs) is associated with adverse clinical outcomes. Systemic inflammation is highly prevalent in HD patients and is associated with ESA hyporesponsiveness. Oxidative stress is also highly prevalent in HD patients, but no previous study has determined its association with ESA response. This study assessed the association of plasma markers of oxidative stress and inflammation with ESA resistance in patients undergoing maintenance HD.

Methods

We analyzed data from 165 patients enrolled in the Provision of Antioxidant Therapy in Hemodialysis study, a randomized controlled trial evaluating antioxidant therapy in prevalent HD patients. Linear and mixed-effects regression were used to assess the association of baseline and time-averaged high sensitivity F2-isoprostanes, isofurans, C-reactive protein (hsCRP), and interleukin-6 (IL-6) with ESA resistance index (ERI), defined as the weekly weight-adjusted ESA dose divided by blood hemoglobin level. Unadjusted models as well as models adjusted for potential confounders were examined. Predicted changes in ERI per month over study follow-up among baseline biomarker quartiles were also assessed.

Results

Patients with time-averaged isofurans in the highest quartile had higher adjusted mean ERI compared with patients in the lowest quartile (β = 14.9 ng/ml; 95 % CI 7.70, 22.2; reference group <0.26 ng/ml). The highest quartiles of hsCRP and IL-6 were also associated with higher adjusted mean ERI (β = 10.8 mg/l; 95 % CI 3.52, 18.1 for hsCRP; β = 10.2 pg/ml; 95 % CI 2.98, 17.5 for IL-6). No significant association of F2-isoprostanes concentrations with ERI was observed. Analyses restricted to baseline exposures and ERI showed similar results. Baseline hsCRP, IL-6, and isofurans concentrations in the highest quartiles were associated with greater predicted change in ERI over study follow-up compared to the lowest quartiles (P = 0.008, P = 0.004, and P = 0.04, respectively). There was no association between baseline F2-isoprostanes quartile and change in ERI.

Conclusions

In conclusion, higher concentrations of isofurans, hsCRP and IL-6, but not F2-isoprostanes, were associated with greater resistance to ESAs in prevalent HD patients. Further research is needed to test whether interventions that successfully decrease oxidative stress and inflammation in patients undergoing maintenance HD improve ESA responsiveness.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0074-9) contains supplementary material, which is available to authorized users.

Levels of F2 isoprostane in Behcet's disease: Correlation with cardiometabolic risk factors

OBJECTIVE

Behcet's disease (BD) is a chronic inflammatory disease and recent findings suggest a role of oxidative stress in the pathogenesis of BD. Free radical-induced oxidative stress is also involved in the pathogenesis of cardiovascular and other rheumatic diseases. Oxidative stress may be detected in vivo by measuring F2 isoprostanes. Here, we measured plasma levels of F2 isoprostane in patients with BD and evaluated the correlation of F2 isoprostane with cardiometabolic risk factors.

METHODS

Forty-three patients with BD in remission and 37 age- and sex-matched controls were recruited for the study. Blood samples were obtained to determine F2 isoprostane, C-reactive protein levels, erythrocyte sedimentation rate, and other biochemical parameters. Homeostasis model assessment insulin resistance and body mass index were calculated. Systolic blood pressure, diastolic blood pressure, and waist circumference were measured.

RESULTS

Plasma F2 isoprostane, fasting plasma glucose, triglyceride, and C-reactive protein levels were significantly higher in patients with BD compared with healthy controls, whereas high-density lipoprotein cholesterol levels were significantly lower in patients with BD. F2 isoprostane levels did not correlate with cardiometabolic risk factors, C-reactive protein levels, or erythrocyte sedimentation rate.

CONCLUSION

High levels of F2 isoprostane in patients with BD indicate oxidative stress. Antioxidant therapeutic approaches could potentially affect the course of this disease.

The isoprostanes--25 years later

Isoprostanes (IsoPs) are prostaglandin-like molecules generated independent of the cyclooxygenase (COX) by the free radical-induced peroxidation of arachidonic acid. The first isoprostane species discovered were isomeric to prostaglandin F2α and were thus termed F2-IsoPs. Since the initial discovery of the F2-IsoPs, IsoPs with differing ring structures have been identified as well as IsoPs from different polyunsaturated fatty acids, including eicosapentaenoic acid and docosahexanenoic acid. The discovery of these molecules in vivo in humans has been a major contribution to the field of lipid oxidation and free radical research over the course of the past 25 years. These molecules have been determined to be both biomarkers and mediators of oxidative stress in numerous disease settings. This review focuses on recent developments in the field with an emphasis on clinical research. Special focus is given to the use of IsoPs as biomarkers in obesity, ischemia-reperfusion injury, the central nervous system, cancer, and genetic disorders. Additionally, attention is paid to diet and lifestyle factors that can affect endogenous levels of IsoPs. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance."

New insights regarding tissue Se and Hg interactions on oxidative stress from plasma IsoP and IsoF measures in the Canadian Inuit population

Despite animal and in vitro studies demonstrating pro-oxidative effects of Hg, previous human work showed no relationship between tissue Hg and plasma levels of F2-isoprostanes (IsoPs), a whole-body oxidative stress marker. We hypothesized that another IsoP species, isofurans (IsoFs), was a more sensitive indicator of Hg-mediated oxidative stress, which can be modified by tissue Se status. A cross-sectional study was carried out involving individuals from a random subset (n = 233) of Inuit adults from a population-based survey (n = 2,595) of 36 Canadian Arctic Inuit communities to assess the relationships of plasma IsoPs to Se and Hg status indicators. F2-IsoPs were inversely correlated with blood Se (r = -0.186, P = 0.005) and toenail Se (r = -0.146, P = 0.044), but not correlated with Hg. IsoFs were inversely correlated with blood Se (r = -0.164, P = 0.014) and positively correlated with Hg (r = 0.228, P < 0.001) and Hg:Se (r = 0.340, P < 0.001). The strength of the correlations remained unchanged after multivariate adjustments. Multivariate analysis showed that F2-IsoPs were not positively associated with Hg but with Hg:Se (β = 0.148, P = 0.021). We conclude that Se and Hg status and their interactions are important factors modulating F2-IsoP and IsoF levels such that the Inuit may be protected from Hg-induced oxidative stress because of their high Se status.