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

Abstract

Objectives: The aim of the present study was to investigate the potential importance of oxidative stress, measured by isoprostanes-related compounds, as non-traditional risk factor for cardiovascular disease. We planned to examine the relationship between concentrations of plasma F₂-isoprostanes (F₂-IsoPs), isofurans (IsoFs), measures of obesity and various cardiometabolic risk factors. Materials and methods: Cross-sectional study using a sub-sample from the population of a survey conducted in the summer and fall 2007 and 2008 by Canadian Coastguard Ship Amundsen in 36 Canadian Arctic Inuit communities. Subjects included a subset (n =?233) of a total study population (n =?2595) with a mean age 42.56 ± 15.39 years and body mass index 27.78 ± 5.65 kg/m². Plasma levels of F₂-IsoPs and IsoFs was determined by gas chromatography/negative ion chemical ionization/mass spectrometry (GC/NICI/MS) method; and their relationships to waist circumference (WC), blood pressure C reactive proteins (CRP), blood lipids and fasting glucose were assessed by multivariate analyses. Results: Plasma F₂-IsoPs correlated positively with CRP (r =.132, P =.048) and systolic blood pressure (SBP) (r =.157, P =.024) after adjustment for age, sex and body mass index. IsoFs correlated with WC (r =.190, P =.005) and SBP (r =.137, P =.048). F2-IsoPs were not found elevated in smokers (P =.034), whereas IsoFs were decreased in smokers (P =.001). WC, SBP and sex were found to be major correlates of oxidative stress in Canadian Inuit. Conclusions: Plasma measures of F₂-IsoPs and IsoFs increase with increased obesity and associated cardiometabolic risk factors, including CRP and blood pressure. Simultaneous measurement of IsoFs provides an advantageous mechanistic insight into oxidative stress not captured by F₂-IsoPs alone.     

Isofurans,but not F2-isoprostanes,are increased in the substantia nigra of patients with Parkinson's disease and with dementia with Lewy body disease

F2-isoprostanes (F2-IsoPs) are well-established sensitive and specific markers of oxidative stress in vivo. Isofurans (IsoFs) are also products of lipid peroxidation, but in contrast to F2-IsoPs, their formation is favored when oxygen tension is increased in vitro or in vivo. Mitochondrial dysfunction in Parkinson's disease (PD) may not only lead to oxidative damage to brain tissue but also potentially result in increased intracellular oxygen tension, thereby influencing relative concentrations of F2-IsoPs and IsoFs. In this study, we attempted to compare the levels of F2-IsoPs and IsoFs esterified in phospholipids in the substantia nigra (SN) from patients with PD to those of age-matched controls as well as patients with other neurodegenerative diseases, including dementia with Lewy body disease (DLB), multiple system atrophy (MSA), and Alzheimer's disease (AD). The results demonstrated that IsoFs but not F2-IsoPs in the SN of patients with PD and DLB were significantly higher than those of controls. Levels of IsoFs and F2-IsoPs in the SN of patients with MSA and AD were indistinguishable from those of age-matched controls. This preferential increase in IsoFs in the SN of patients with PD or DLB not only indicates a unique mode of oxidant injury in these two diseases but also suggests different underlying mechanisms of dopaminergic neurodegeneration in PD and DLB from those of MSA.     

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.     

Quantification of F2-isoprostanes as a biomarker of oxidative stress

Oxidant stress has been implicated in a wide variety of disease processes. One method to quantify oxidative injury is to measure lipid peroxidation. Quantification of a group of prostaglandin F(2alpha)-like compounds derived from the nonezymatic oxidation of arachidonic acid, termed the F2-isoprostanes (F2-IsoPs), provides an accurate assessment of oxidative stress both in vitro and in vivo. In fact, in a recent independent study sponsored by the National Institutes of Health (NIH), F2-IsoPs were shown to be the most reliable index of in vivo oxidant stress when compared against other well known biomarkers. This protocol details our laboratory's method to quantify F2-IsoPs in biological fluids and tissues using gas chromatography-mass spectrometry (GC-MS). This procedure can be completed for 12-15 samples in 6-8 h.     

The extent to which adiposity markers explain the association between sedentary behavior and cardiometabolic risk factors

An emerging body of evidence suggests that sedentary behavior (SB) is an independent risk factor for cardiometabolic disease. Recent data suggest that multi-domain SB has detrimental associations with BMI, waist circumference (WC), and nonadiposity-related (total cholesterol, high density lipoprotein cholesterol (HDL-C), systolic (SBP) and diastolic (DBP) blood pressure) cardiometabolic risk markers. The aim of this cross-sectional study was to examine the extent to which the associations between SB and nonadiposity-related cardiometabolic risk markers are explained by adiposity markers. Subjects were 5,067 Health Survey for England (HSE) 2008 respondents (2,552 men) aged 16-65 years. The measurements protocol involved self-reports of television time, other recreational sitting, occupational sitting/standing, physical activity and objective measures of weight, height, WC, total cholesterol, HDL cholesterol, SBP, and DBP. BMI or WC adjustments of the multivariable models looking at the associations between SB and nonadiposity markers attenuated all associations towards the null. Using established logistic regression-based algorithms we calculated that a large percentage of the associations between SB time and nonadiposity risk factors is explained by BMI or WC (range: 27.3-95.9%). Future longitudinal studies should further examine the mediatory role of adiposity in explaining the associations between SB and cardiometabolic risk.     

Oxidative stress, erythrocyte ageing and plasma non-protein-bound iron in diabetic patients

Increased oxidative stress and decreased life span of erythrocytes (RBCs) are repeatedly reported in diabetes. In the aim to elucidate the mechanism of the latter, i.e. the events leading to erythrocyte ageing, this study determined in RBCs from diabetic patients iron release in a free desferrioxamine-chelatable form (DCI), methemoglobin (MetHb) formation, binding of autologous IgG to membrane proteins and in plasma non-protein-bound iron (NPBI), F(2)-Isoprostanes (F(2)-IsoPs) and advanced oxidation protein products (AOPP). DCI and MetHb were higher in diabetic RBCs than in controls and autologous IgG binding occurred in a much higher percentage of diabetic patients than controls. A significant correlation between DCI and IgG binding was found in diabetic RBCs. Plasma NPBI, esterified F(2)-IsoPs and AOPP were higher in diabetic patients and a significant correlation was found between plasma NPBI and intra-erythrocyte DCI. The increased DCI and autologous IgG binding appear to be important factors in the accelerated removal of RBCs from the blood stream in diabetes and the increase in plasma NPBI could play an important role in the increased oxidative stress.     

A comparison of the metabolic response to abdominal obesity in two Canadian Inuit and First Nations population

Inuit and Cree populations are known for high obesity rates despite markedly different rates of type 2 diabetes (T2DM). To document this apparent discrepancy we evaluated the impact of body size parameters and fasting insulin (FI) on several T2DM risk factors among Inuit and Cree populations (Québec, Canada). A total of 1,104 adults (≥18 years) Inuit and Cree individuals participated in a cross-sectional investigation. Interestingly, across both genders, across all levels of waist circumference (WC), Inuit showed lower levels of FI (age-adjusted, P < 0.0001) and fasting glucose (P < 0.0001) than Cree individuals. In both groups, a comparison of multi-sample structural equation models confirmed the predominant influence of WC on other traditional risk factors, compared to BMI. A preponderant direct impact of WC was observed on blood pressure (BP) parameters (P < 0.0001), high-density lipoprotein cholesterol (HDL-C) (P < 0.0001), and FI (P < 0.0001). Fasting glucose level appear to be influenced by WC via FI in both ethnic groups (P < 0.0001), while triacylglycerol (TAG) level was predominantly impacted by WC via FI, but only in Cree individuals (P < 0.0001). The main ethnic difference found was the strength of the impact of WC on FI, which was considerably higher among the Cree (λ = 2.4, P < 0.0001) than the Inuit (λ = 1.8, P < 0.0001). These results confirm the predominant role of abdominal adiposity in the complex and tenuous links of different traditional T2DM determinants. However, the ethnic difference in the impact of abdominal obesity on insulin levels across all WCs needs to be explored further.     

Ethnic Differences in Cardiometabolic Risk Profile at Age 5-6 Years: The ABCD Study

Background

To examine ethnic differences in cardiometabolic risk profile in early age, and explore whether such differences can be explained by differences in body mass index (BMI) or waist circumference (WC).

Method

Anthropometric measurements, blood pressure and (in a subsample) fasting blood were collected during a health check of 2,509 children aged 5–6 years. Four ethnic groups were distinguished: Dutch (n = 2,008; blood n = 1,300), African descent (n = 199; blood n = 105), Turkish (n = 108; blood n = 57) and Moroccan (n = 194; blood n = 94). Ethnic differences in diastolic and systolic blood pressure (DBP/SBP), fasting glucose, low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglyceride levels were determined and the explanatory role of BMI and WC was examined with regression analysis.

Results

After adjustment for confounders, African descent children showed higher DBP (β2.22 mmHg; 95%CI:1.09–3.36) and HDL levels (β:0.09 mmol/l; 95%CI:0.03–0.16) compared to Dutch children (reference group). Turkish children showed higher SBP (β:1.89 mmHg; 95%CI:0.25–3.54), DBP (β:2.62 mmHg; 95%CI:1.11–4.13), glucose (β:0.12 mmol/L; 95%CI:0.00–0.25) and triglyceride levels (β:0.13 mmol/L; 95%CI:0.02–0.25). Higher BMI values were found in all non–Dutch groups (differences ranged from 0.53–1.03 kg/m²) and higher WC in Turkish (β:1.68 cm; 95%CI:0.99–2.38) and Moroccan (β:1.65 cm; 95%CI:1.11–2.19) children. BMI and WC partly explained the higher SBP/DBP and triglyceride levels in Turkish children.

Conclusion

Ethnic differences in cardiometabolic profile exist early in life and are partly explained by differences in BMI and WC. African children showed favourable HDL levels and Turkish children the most unfavourable overall profile, whereas their Moroccan peers have less increased cardiometabolic risk in spite of their high BMI and WC.     

Correlation between two markers of inflammation, serum C-reactive protein and interleukin 6, and indices of oxidative stress in patients with high risk of cardiovascular disease.

As evidence of the involvement of inflammation and oxidative damage in pathogenesis of age-related chronic diseases is growing, epidemiologists need to develop measures of both conditions to study their relationships in human populations. One way of searching for appropriate biomarkers is to examine correlations between different inflammatory markers and oxidative indices. We examined cross-sectional correlations between two inflammatory markers, serum C-reactive protein (CRP) and interleukin (IL)-6, and three oxidative indices, plasma levels of alpha-tocopherol and beta-carotene, and urinary levels of 2,3-dinor-5,6-dihydro-15-F2t-isoprostane (F2-IsoP), in 60 individuals at high risk of cardiovascular disease. Correlations between the biomarkers were examined graphically and using the Pearson correlation coefficient. No correlation was found between plasma levels of alpha-tocopherol and either of the inflammatory markers. Plasma beta-carotene inversely correlated with IL-6 (r = -0.46, p=0.0002) and CRP (r = -0.41, p = 0.001). Although urinary F2-IsoP did not correlate with IL-6, this biomarker positively correlated with CRP (r = 0.31, p = 0.002). As only urinary F2-IsoP levels have been validated against known oxidative assaults, their positive association with CRP levels is interpreted as evidence of an interconnection between low-level inflammation and oxidative status. Urinary levels of F2-IsoP and serum levels of CRP represent appropriate biomarkers for future studies of inflammation and oxidative status in humans.     

F2-isoprostanes are not just markers of oxidative stress

F(2)-isoprostanes are not just markers of oxidative stress. The discovery of F(2)-isoprostanes (F(2)-IsoPs) as specific and reliable markers of oxidative stress in vivo is briefly summarized here. F(2)-IsoPs are also agonists of important biological effects, such as the vasoconstriction of renal glomerular arterioles, the retinal vessel, and the brain microcirculature. In addition to the F(2)-IsoPs, E(2)- and D(2)-IsoPs can be formed by rearrangement of H(2)-IsoP endoperoxides and can give rise to cyclopentenone IsoPs, which are very reactive alpha,beta-unsaturated aldehydes. The same type of reactivity is also shown by acyclic gamma-ketoaldehydes formed as products of the IsoP pathway. Because previous studies suggested a relation between oxidative stress and collagen hyperproduction, it was investigated whether collagen synthesis is induced by F(2)-IsoPs, the most proximal products of lipid peroxidation. In contrast to aldehydes, F(2)-IsoPs act through receptors able to elicit definite signal transduction pathways. In a rat model of carbon tetrachloride-induced hepatic fibrosis, plasma F(2)-IsoPs were markedly elevated for the entire experimental period; hepatic collagen content was also increased. When hepatic stellate cells from normal liver were cultured up to activation (expression of smooth muscle alpha-actin) and then treated with F(2)-IsoPs in the concentration range found in the in vivo studies (10(-9) to 10(-8) M), a striking increase in DNA synthesis, cell proliferation, and collagen synthesis was observed. Total collagen content was similarly increased. All these stimulatory effects were reversed by the specific antagonist of the thromboxane A(2) receptor, SQ 29 548, whereas the receptor agonist, I-BOP, also had a stimulatory effect. Therefore F(2)-IsoPs generated by lipid peroxidation in hepatocytes may mediate hepatic stellate cell proliferation and collagen hyperproduction seen in hepatic fibrosis.     

Measurement of F(2)-isoprostanes as an index of oxidative stress in vivo

In 1990 we discovered the formation of prostaglandin F(2)-like compounds, F(2)-isoprostanes (F(2)-IsoPs), in vivo by nonenzymatic free radical-induced peroxidation of arachidonic acid. F(2)-IsoPs are initially formed esterified to phospholipids and then released in free form. There are several favorable attributes that make measurement of F(2)-IsoPs attractive as a reliable indicator of oxidative stress in vivo: (i) F(2)-IsoPs are specific products of lipid peroxidation; (ii) they are stable compounds; (iii) levels are present in detectable quantities in all normal biological fluids and tissues, allowing the definition of a normal range; (iv) their formation increases dramatically in vivo in a number of animal models of oxidant injury; (v) their formation is modulated by antioxidant status; and (vi) their levels are not effected by lipid content of the diet. Measurement of F(2)-IsoPs in plasma can be utilized to assess total endogenous production of F(2)-IsoPs whereas measurement of levels esterified in phospholipids can be used to determine the extent of lipid peroxidation in target sites of interest. Recently, we developed an assay for a urinary metabolite of F(2)-IsoPs, which should provide a valuable noninvasive integrated approach to assess total endogenous production of F(2)-IsoPs in large clinical studies.     

The relationship of age, body mass index and waist circumference with blood pressure in Bengalee Hindu male jute mill workers of Belur, West Bengal, India

A cross-sectional study of 150 adult Bengalee Hindu male jute mill workers of Belur, a suburb of Kolkata, West Bengal, India, was undertaken to study the relationship of age, body mass index (BMI) and waist circumference (WC) with systolic (SBP), diastolic (DBP) and mean arterial (MAP) blood pressure. The mean age and the BMI of the subjects were 40.7 years (S.D. = 15.2) and 23.2 kg/m2 (S.D. = 3.2), respectively. The mean SBP, DBP and MAP were 124.7 mmHg (S.D. = 7.8), 81.5 mmHg (S.D. = 5.7) and 95.9 mmHg (S.D. = 6.1), respectively. Age had similar significant (p < 0.001) correlations with BMI and WC. Age and WC were significantly correlated (p < 0.001) with all the three blood pressure variables. In general, the correlations of BMI with SBP (r = 0.24, p < 0.01), DBP (r = 0.15, n.s.) and MAP (r = 0.19, p < 0.05) were weaker. Age controlled multiple regression analyses demonstrated that BMI did not have a significant effect of any blood pressure variable. However, WC had a significant impact (p < 0.0001) on SBP (t = 7.068), DBP (t = 5.190) and MAP (t = 6.387), even after adjusting for the effect of age. Moreover, even after age adjustment, percent variations in SBP (20.7%), DBP (12.5%) and MAP (17.2%) explained by WC were high. This significant impact (p < 0.0001) of WC on SBP (t = 9.426), DBP (t = 8.349) and MAP (t = 9.642) remained even after controlling for the combined effects of age and BMI.     

Antioxidant supplementation prevents exercise-induced lipid peroxidation, but not inflammation, in ultramarathon runners

To determine if 6 weeks of supplementation with vitamins E and C could alleviate exercise-induced lipid peroxidation and inflammation, we studied 22 runners during a 50 km ultramarathon. Subjects were randomly assigned to one of two groups: (1) placebos (PL) or (2) antioxidants (AO: 1000 mg vitamin C and 300 mg RRR-alpha-tocopheryl acetate). Blood samples were obtained prior to supplementation (baseline), after 3 weeks of supplementation, 1 h pre-, mid-, and postrace, 2 h postrace and for 6 days postrace. Plasma levels of alpha-tocopherol (alpha-TOH), ascorbic acid (AA), uric acid (UA), F2-isoprostanes (F2-IsoPs), tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and C-reactive protein (CRP) were measured. With supplementation, plasma alpha-TOH and AA increased in the AO but not the PL group. Although F2-IsoP levels were similar between groups at baseline, 28 +/- 2 (PL) and 27 +/- 3 pg/ml (AO), F2-IsoPs increased during the run only in the PL group (41 +/- 3 pg/ml). In PL women, F2-IsoPs were elevated postrace (p <.01), but returned to prerace concentrations by 2 h postrace. In PL men, F2-IsoP concentrations were higher postrace, 2 h postrace, and 1, 2, 3, 4, and 6 days postrace (PL vs. AO group, each p <.03). Markers of inflammation were increased dramatically in response to the run regardless of treatment group. Thus, AO supplementation prevented endurance exercise-induced lipid peroxidation but had no effect on inflammatory markers.     

Measurement of F2-isoprostanes, hydroxyeicosatetraenoic products, and oxysterols from a single plasma sample

Oxidized lipids such as F2-isoprostanes (F2-IsoPs), hydroxyeicosatetraenoic acid products (HETEs), and cholesterol oxidation products (COPs) are widely believed to be involved in multiple diseases. Usually, each product is measured individually in separate blood samples. In this study we describe a method allowing us to measure F2-IsoPs, HETEs, COPs, and arachidonate using a single sample. Plasma (1 ml) samples from healthy volunteers were diluted with heavy isotopic standards, hydrolyzed in alkali with organic solvent, and then subjected to anionic-exchange solid-phase extraction (SPE). After the SPE column was washed, hexane and hexane/ethyl acetate portions were collected and combined for COPs measurement. Thereafter the column was loaded with hexane/ethanol/acetic acid and fractions were collected for total F2-IsoPs, total HETEs, and arachidonate measurement. All compounds in the eluates were measured by gas chromatography-mass spectrometry. The efficiency of SPE and reproducibility for all compounds measured were high. Levels of total F2-IsoPs (0.45+/-0.26 ng/ml (n=157)), total HETEs (34.06+/-16.35 ng/ml (n=21)), total arachidonate (68.36+/-24.45 microg/ml (n=33)), and COPs (7-ketocholesterol, 12.25+/-6.56 ng/ml; 7beta-hydroxycholesterol, 6.32+/-3.46 ng/ml; 7alpha-hydroxycholesterol, 15.06+/-7.06 ng/ml; 24-hydroxycholesterol, 41.39+/-18.22 ng/ml; and 27-hydroxycholesterol, 29.08+/-16.79 ng/ml (n=26)) were recorded in healthy subjects (age range 20 to 66 years; average male to female ratio 1:1).     

Increased levels of F2-isoprostanes following aneurysmal subarachnoid hemorrhage in humans

Subarachnoid hemorrhage (SAH) resulting from aneurysmal rupture is the major cause of nontraumatic SAH. We hypothesized that oxidative stress could be increased following aneurysmal SAH due to hemoglobin release and ischemia-reperfusion injury and that may further contribute to poor outcome. We collected plasma and cerebrospinal fluid (CSF) samples from 11 non-SAH controls and 15 aneurysmal SAH patients for up to 10 days after surgery and investigated status of oxidative stress in patients. Results showed that mean or peak levels of F(2)-isoprostanes (F(2)-IsoPs), a specific marker of lipid peroxidation, and total nitrate/nitrite, metabolites of nitric oxide and peroxynitrite, in CSF and plasma were significantly higher in SAH patients than in controls. First-day levels were also higher in CSF, but not in plasma, in SAH patients. Moreover, mean and peak levels of CSF F(2)-IsoPs were positively correlated with poor outcome or severity of clinical conditions in patients. Furthermore, levels of retinol, delta-tocopherol, beta+gamma-tocopherol, lutein, beta-carotene, and coenzyme Q(10) in plasma were significantly lower in SAH patients than in controls. Our results indicate that oxidative damage may play important roles in the severity and complications of aneurysmal SAH and suggest that means to suppress lipid peroxidation may be beneficial in improving the outcome of aneurysmal SAH.     

Comparison of measures of adiposity in identifying cardiovascular disease risk among Ethiopian adults

We sought to determine which measures of adiposity can predict cardiovascular disease (CVD) risk and to evaluate the extent to which overall and abdominal adiposity are associated with cardiometabolic risk factors among working adults in Ethiopia. This was a cross-sectional study of 1,853 individuals (1,125 men, 728 women) in Addis Ababa, Ethiopia. The World Health Organization STEPwise approach was used to collect sociodemographic data, anthropometric measurements, and blood samples among study subjects. Fasting blood glucose (FBG) and lipid concentrations were measured using standard approaches. Spearman's rank correlation, receiver operating characteristic (ROC) curves, and logistic regression were employed to determine the association and predictive ability (with respect to CVD risk factors) of four measures of adiposity: BMI, waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR). Overall, FBG is best associated with WHtR in men and WC in women. Systolic blood pressure (SBP) is most strongly associated with BMI in men, but with WC in women. Compared to those with low BMI and low WC, the risk of having CVD is the highest for those with high BMI and high WC and those with high WC and low BMI. Review of ROC curves indicated that WC is the best predictor of CVD risk among study subjects. Findings from our study underscore the feasibility and face validity of using simple measures of central and overall adiposity in identifying CVD risk in resource-poor settings.     

Urinary F₂-isoprostanes, obesity, and weight gain in the IRAS cohort

Obesity has been associated with increased F(2)-isoprostane (F(2)-IsoP) levels cross-sectionally. However, the prospective association may be inverse, based on our earlier finding that elevated urinary F(2)-IsoP levels predict lower risk of diabetes. This earlier finding led us to hypothesize that urinary F(2)-IsoPs reflect the intensity of oxidative metabolism and as such predict lower risk of both diabetes and weight gain. We examined cross-sectional relationships with obesity and prospective relationships with weight gain using the data from 299 participants of the Insulin Resistance Atherosclerosis Study (IRAS), all of whom were free of diabetes at baseline. Four urinary F(2)-IsoPs were assayed in stored baseline urine samples using liquid chromatography with tandem mass spectrometry: iPF(2α)-III, 2,3-dinor-iPF(2α)-III, iPF(2α)-VI, and 8,12-iso-iPF(2α)-VI (F(2)-IsoP 1-4, respectively). Baseline F(2)-IsoPs were positively associated with baseline measures of obesity; the strongest associations were found with two F(2)-IsoPs: odds ratios (95% confidence intervals) for overall and abdominal obesity were 1.74 (1.26-2.40) and 1.63 (1.18-2.24) for F(2)-IsoP2 and 1.47 (1.12-1.94) and 1.64 (1.22-2.20) for F(2)-IsoP4. F(2)-IsoP2 showed the strongest and significant inverse association with weight gain during the 5-year follow-up period: increase in F(2)-IsoP2 equal to 1 s.d. was associated with 0.90 kg lower weight gain (P = 0.02) and the odds ratios for relative (≥5%) and absolute (≥5 kg) weight gain were 0.67 (0.47-0.96) and 0.57 (0.37-0.87), respectively. The other three F(2)-IsoPs were consistently inversely associated with weight gain, although not significantly, suggesting that different F(2)-IsoPs vary in their ability to detect the association with weight gain.     

Isoprostanes and the liver

The liver has been central to our understanding of the physiology and biology of the F2-isoprostanes. The discovery of F2-IsoPs and the initial demonstration that they could be used to localize oxidative stress was first demonstrated in a rat model of oxidative liver injury (carbon tetrachloride), and the first demonstration that plasma concentrations are increased in a human disease was in patients with liver failure and the hepatorenal syndrome [J. Clin. Invest. 90 (6) (1992b) 2502; J. Lipid Mediat. 6 (1/3) (1993) 417]. This article will cover the measurement of F2-IsoPs as markers of lipid peroxidation in vivo in liver disease, and review their biological activity as mediators of disease.     

Inflammatory response to a high-fat, low-carbohydrate weight loss diet: effect of antioxidants

The objective of this study was to test the hypothesis that the inflammatory response to a high-fat, low-carbohydrate weight loss diet (HF) we previously observed was due to oxidative stress. Nineteen overweight subjects (BMI>27 kg/m(2)) were randomly assigned to either an antioxidant supplement (AS) (1 g vitamin C/800 IU vitamin E) or a placebo (P) group and provided with a HF for 7 days. Fasted pre- and post serum samples were measured for markers of inflammation (C-reactive protein (CRP), interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1)), oxygen radical absorbance capacity (ORAC), and glucose, whereas urine was measured for oxidative stress (8-epi-prostaglandin-F(2alpha) (8-epi)). HF resulted in significant reductions in weight (-3.2%), glucose (-18.7%), and MCP-1 (-15%) (all P<0.01), with no difference between groups. There was a trend for a differential effect between groups for CRP as it decreased 32% in the AS group but increased 50% for P (P=0.076). Inverse correlations were noted between initial values and changes in several inflammatory and oxidative stress markers, including CRP (r= -0.501), 8-epi (r= -0.863), and ORAC (r= -0.546) (all P<0.05). It was concluded that weight loss on a short-term HF caused reduction of some but not all markers of inflammation. A role for oxidative stress in causing inflammation was not confirmed; however, longer term diet-controlled studies are necessary to further explore the trend for a differential response in CRP with antioxidant supplementation.     

Measurement of chronic oxidative and inflammatory stress by quantification of isoketal/levuglandin gamma-ketoaldehyde protein adducts using liquid chromatography tandem mass spectrometry

Measurement of F(2)-isoprostanes (F(2)-IsoPs) has been independently verified as one of the most reliable approaches to assess oxidative stress in vivo. However, the rapid clearance of F(2)-IsoPs makes the timing of sample collection critical for short-lived oxidative insults. Isoketals (IsoKs) are gamma-ketoaldehydes formed via the IsoP pathway of lipid peroxidation that rapidly react with lysyl residues of proteins to form stable protein adducts. Oxidative stress can also activate cyclooxygenases to produce prostaglandin H(2), which can form two specific isomers of IsoK-levuglandin (LG) D(2) and E(2). Because adducted proteins are not rapidly cleared, IsoK/LG protein adduct levels can serve as a dosimeter of oxidative and inflammatory damage over prolonged periods of time as well as brief episodes of injury. Quantification of IsoK/LG protein adducts begins with liquid-phase extraction to separate proteins from lipid membranes, allowing measurement of both IsoK/LG protein adducts and F(2)-IsoP from the same sample if desired. IsoK/LG-lysyl-lactam adducts are measured by liquid chromatography tandem mass spectrometry after proteolytic digestion of extracted proteins, solid-phase extraction and preparative HPLC.