Measures of Oxidized Low-Density Lipoprotein and Oxidative Stress Are Not Related and Not Elevated in Otherwise Healthy Men With the Metabolic Syndrome

Oxidized LDL Modify the Human Adipocyte Phenotype to an Insulin Resistant, Proinflamatory and Proapoptotic Profile

Little information exists in humans on the regulation that oxidized low-density lipoprotein (oxLDL) exerts on adipocyte metabolism, which is associated with obesity and type 2 diabetes. The aim was to analyze the oxLDL effects on adipocytokine secretion and scavenger receptors (SRs) and cell death markers in human visceral adipocytes. Human differentiated adipocytes from visceral adipose tissue from non-obese and morbidly obese subjects were incubated with increasing oxLDL concentrations. mRNA expression of SRs, markers of apoptosis and autophagy, secretion of adipocytokines, and glucose uptake were analyzed. In non-obese and in morbidly obese subjects, oxLDL produced a decrease in insulin-induced glucose uptake, a significant dose-dependent increase in tumor necrosis factor-α (TNF-α), IL-6, and adiponectin secretion, and a decrease in leptin secretion. OxLDL produced a significant increase of Lox-1 and a decrease in Cxcl16 and Cl-p1 expression. The expression of Bnip3 (marker of apoptosis, necrosis and autophagy) was significantly increased and Bcl2 (antiapoptotic marker) was decreased. OxLDL could sensitize adipocytes to a lower insulin-induced glucose uptake, a more proinflammatory phenotype, and could modify the gene expression involved in apoptosis, autophagy, necrosis, and mitophagy. OxLDL can upregulate Lox-1, and this could lead to a possible amplification of proinflammatory and proapoptotic effects of oxLDL.

The Effect of Visceral Abdominal Fat Volume on Oxidative Stress and Proinflammatory Cytokines in Subjects with Normal Weight, Overweight and Obesity

PURPOSE

The increase of visceral abdominal fat (VAF) and oxidative stress (OS) are independent predictors for cardiovascular risk. This study aimed to determine the association of VAF with proinflammatory cytokines, oxidants, antioxidants, and oxidative damage to DNA in subjects with normal weight, overweight, and obesity.

PATIENTS AND METHODS

A cross-sectional study that included 21 men and 71 women who attended for a medical check-up was conducted. Dual-energy X-ray absorptiometry (DXA) was used to measure the VAF volume. ELISA and colorimetric techniques were used for chemical analysis.

RESULTS

Low activity of superoxide dismutase (SOD) was found in overweight and obese subjects compared to the normal weight group (p=0.005). In contrast, the activity of glutathione peroxidase (GPx) was higher in the overweight and obesity groups compared to the normal weight subjects (p=0.017). The total antioxidant capacity (TAC) was also increased in the overweight group compared to the normal weight group (p=0.04). According to the volume of VAF, the levels of tumor necrosis factor alfa and interleukin 6 showed no differences between subjects with normal and high VAF. Subjects with high VAF show higher levels of 8-isoprostans compared to normal VAF group (p=0.039). Less concentration of 8-oxoguanine-DNA-N-glycosylase-1 (hOGG1) was found in the high VAF group (p=0.032) compared to the normal VAF subjects. VAF was positively correlated with lipoperoxides (LPO) (r=0.27, p<0.05) and 8-isoprostanes (r=0.25, p<0.05). We also found correlations between oxidative stress markers and anthropometric ratios for intra-abdominal fat. The waist-hip ratio was positively correlated with LPO (r=0.30, p<0.05) and TAC (r=0.24, p<0.05).

CONCLUSION

These findings suggest that the predominantly oxidative damage associated with VAF in overweight or obesity is lipoperoxidation and oxidative DNA damage. Alterations in endogenous antioxidant defenses may not be linked to the amount of VAF.

The relationship between glucose variability and insulin sensitivity and oxidative stress in subjects with prediabetes

AIM

The present study assessed the relationship between glucose variability (GV) and insulin levels, insulin resistance and oxidative stress at early stages of glucose intolerance.

MATERIAL AND METHODS

A total of 50 subjects - 12 males and 38 females, mean age 55.6 ± 9.7 years, mean BMI 28.4 ± 6.4 kg/m², divided into 2 groups according to glucose tolerance: 32 with prediabetes and 18 with normal glucose tolerance were included. Glucose tolerance was assessed by OGTT according to WHO 2006 criteria. Plasma glucose and serum insulin were measured at fasting, 120-minute and 180-minute during the test; and oxLDL and 3-Nitrotyrosine - at fasting and 120-minute. HOMA-IR and OGIS indexes were calculated. HbA1c and lipid levels was assessed. Continuous glucose monitoring was performed with a blind sensor (FreeStyle Libre Pro) for a mean period of 13.6 ± 2.3 days.

RESULTS

Our results demonstrate significantly increased insulin resistance in subjects with prediabetes, whereas there is no difference in oxidative stress markers between the two groups. OxLDL and 3-NT correlate positively with insulin levels and HOMA-IR and negatively with OGIS in both groups. There is a positive association between oxidative stress markers and 120-minute glucose in the prediabetes group. Insulin levels and HOMA-IR are positively related to plasma glucose and reciprocally to CV and M-Value in prediabetes, since the latter association is with borderline significance after adjustment for hypertension and smoking.

CONCLUSIONS

Our results demonstrate a significant correlation between oxidative stress and insulin resistance at early stages of glucose intolerance. Both chronic hyperglycemia and GV seem to be related to insulin levels and insulin resistance, and just postload glycaemia to oxidative stress in prediabetes.

Oxidative Stress is Closely Associated with Increased Arterial Stiffness, Especially in Aged Male Smokers without Previous Cardiovascular Events: A Cross-Sectional Study

Aim: Cigarette smoking is one of the major risk factors for cardiovascular diseases and induces deleterious vascular damage. Oxidative stress is involved in vascular inflammation, the process of atherosclerosis. The purpose of the present study was to investigate whether the effects of oxidative stress on the arterial wall differ between smokers and non-smokers.

Methods: Male smokers and non-smokers without physical deconditioning who visited Enshu hospital for an annual physical check-up were enrolled in the study. To assess oxidative stress, serum levels of derivative reactive oxygen metabolites (d-ROM) were measured. The radial augmentation index (RAI) was measured using an automated device and was used as an index for arterial stiffness.

Results: Univariate and multivariate linear regression analysis showed that RAI was independently associated with d-ROM levels only in smokers. Moreover, RAI was significantly higher in smokers than in non-smokers. Logistic regression analysis with the endpoint of a higher RAI than the mean revealed that older age (> 65 years), hypertension, and smoking were independently associated with higher RAI. Similarly, logistic regression analysis with the endpoint of higher d-ROM levels than the mean showed that older age and smoking were independently associated with higher d-ROM levels.

Conclusions: Increased RAI is significantly associated with smoking and, in smokers, with increased d-ROM levels. These results suggest that the effects of oxidative stress on arterial properties differ between smokers and non-smokers and that oxidative stress is closely associated with arterial stiffness, especially in smokers.

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.

A Randomized Clinical Trial Evaluating the Efficacy of an Anthocyanin-Maqui Berry Extract (Delphinol®) on Oxidative Stress Biomarkers

OBJECTIVE

Berries are a rich source of anthocyanins, and clinical data suggest that a polyphenol-rich diet may exert health-promoting effects by reducing oxidative stress. The aim of this study was to elucidate the effects of dietary supplementation with Delphinol (trademark owned by MNL Chile) standardized maqui berry (Aristotelia chilensis) extract on products of lipid peroxidation in healthy, overweight, and smoker subjects.

METHODS

In a double-blind, placebo-controlled design, 42 participants (age 45-65 years) consumed in random order either a standardized extract of maqui berry (162 mg anthocyanins) or a matched placebo, given 3 times daily for 4 weeks. The samples were collected at baseline, after the end of the supplementation, and 40 days after the end of the study. Primary outcome was the measure of oxidized low-density lipoprotein (Ox-LDL) and F2-isoprostanes in plasma and urine, respectively. Secondary outcomes included anthropometric measures, blood pressure, and lipid profile.

RESULTS

Delphinol supplementation was associated with reduced levels of Ox-LDL in the anthocyanin group compared to baseline (p < 0.05). There was also a decrease in urinary F2-isoprostanes (8-iso-prostaglandin F2α) at 4 weeks versus baseline in the Delphinol-supplemented group (p < 0.05). However, no differences in primary outcomes were evident at 40 days of follow-up. In the fourth week of the intervention, no significant differences were noted for anthropometric characteristics, ambulatory blood pressure, and lipid profile.

CONCLUSIONS

Our observations suggest that dietary interventions with maqui berry extract may improve oxidative status (Ox-LDL and F2-isoprostanes) in healthy adults, overweight adults, and adult smokers.

8-Isoprostane and Coenzyme Q10 Levels in Patients with Metabolic Syndrome

BACKGROUND

Metabolic syndrome has become an important health problem, which involves obesity, hyperlipidemia, insulin resistance, and high blood pressure values. The components of metabolic syndrome are all suggested as independent cardiovascular disease risk factors along with high mortality and morbidity rates accompanied by many organ and system complications.

OBJECTIVE

We aimed to determine 8-isoprostane (8-IsoP) and coenzyme Q10 (CoQ10) levels in patients with metabolic syndrome and healthy individuals and demonstrate whether there was any relation between these parameters and metabolic syndrome criteria.

MATERIALS AND METHODS

A total of 30 patients (10 male, 20 female) with metabolic syndrome and 20 age-matched healthy individuals (9 male, 11 female) were involved in the study. Body mass index, waist and hip circumferences, systolic and diastolic blood pressures and serum glucose, triglyceride, total cholesterol, high-density lipoprotein cholesterol, insulin, HbA1c, 8-IsoP and CoQ10 levels, and homeostasis model assessment of insulin resistance indexes of all participants were determined.

RESULTS

8-IsoP levels were significantly increased in metabolic syndrome compared to healthy individuals (P = 0.003), however, there was no significant difference between groups for CoQ10 levels. 8-IsoP levels were positively correlated with waist circumference (r = 0.303, P = 0.032), diastolic blood pressure (r = 0.337, P = 0.017), systolic blood pressure (r = 0.329, P = 0.020) values and total cholesterol levels (r = 0.354, P = 0.012).

CONCLUSION

We can suggest that the levels of 8-IsoP, which is an indicator of the oxidative stress, increase in metabolic syndrome and this can be associated with high blood pressure and visceral adiposity, which are the components of metabolic syndrome.

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.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

Urinary 8-iso-prostaglandin F2α as a marker of metabolic risks in the general Japanese population: The ROAD study

OBJECTIVE

To determine whether 8-iso-prostaglandin F2α (8-iso-PGF2α) is a reliable biomarker of the accumulation of metabolic risks [e.g., overweight, hypertension, impaired glucose tolerance (IGT), and dyslipidemia].

METHODS

This was a cross-sectional study of the baseline characteristics of a Japanese general population cohort study: Research on Osteoarthritis/Osteoporosis Against Disability (ROAD). Of 1,690 participants, 1,527 fulfilled all questionnaires and examinations. Free and conjugated urinary 8-iso-PGF2α levels and metabolic syndrome (MetS) components including blood pressure, HbA1c, total cholesterol, high-density lipoprotein cholesterol (HDL-C), and non-HDL-C were analyzed. The data were analyzed by ANCOVA, multiple regression analysis, and multinomial logistic analysis.

RESULTS

8-iso-PGF2α was significantly associated with HbA1c and significantly inversely associated with total cholesterol and non-HDL-C. Notably, IGT with an HbA1c cut-off of 5.5% was significantly associated with 8-iso-PGF2α level in participants aged ≤50 years. Multinomial logistic regression analysis revealed 8-iso-PGF2α level was significantly associated with a greater number of MetS risks present; this association was stronger in younger participants. In participants aged ≥71 years, 8-iso-PGF2α was significantly associated with a greater number of MetS risks with higher IGT cut-offs.

CONCLUSIONS

Urinary 8-iso-PGF2α can be a reliable marker of IGT and the accumulation of MetS risks, especially in younger people.

Urine 8-isoprostane in relation to adiposity and insulin resistance in individuals at high cardiometabolic risk

BACKGROUND

Oxidative stress has been implicated in the pathogenesis of many conditions, including insulin resistance and obesity. However, in vivo data concerning these relationships are scarce and conflicting. Therefore, the aim of this study was to investigate the association of oxidative stress with abdominal adiposity and insulin resistance in individuals at high cardiometabolic risk.

METHODS

A total of 116 overweight/obese individuals participating in the HealthGrain and Etherpaths European Projects, having waist circumference (WC) and any other component of the metabolic syndrome, were included in this cross-sectional evaluation. 8-Isoprostane concentrations in 24-hr urine were measured as marker of oxidative stress in vivo. Baseline anthropometric and metabolic parameters were analyzed according to quartiles of 8-isoprostanes. Linear regression (LR) analysis was used to assess clinical correlates of oxidative stress.

RESULTS

Urinary 8-isoprostane levels were 52% higher in men than in women (P<0.001). Across the isoprostanes quartiles, there was a significant increase in WC and body weight [P for trend<0.001; analysis of variance (ANOVA) P<0.001] and fasting triglycerides (P for trend<0.05; ANOVA P<0.05), and a significant decrease in high-density lipoprotein cholesterol (P for trend<0.001; ANOVA P=0.001). No significant association between urinary isoprostane concentrations and insulin resistance [homeostasis model assessment of insulin resistance (HOMA-IR)] was found. WC circumference and body weight remained significant after adjustment for age and gender (P=0.023 and P=0.014, respectively) and independently associated with isoprostanes at LR (P<0.005 for both).

CONCLUSIONS

Central obesity was independently associated with oxidative stress even in a population homogeneous for adiposity and cardiometabolic risk, whereas no relationship was observed between oxidative stress and insulin resistance.

Dysregulation of monocyte biology in metabolic syndrome

Metabolic syndrome (MetS), which constitutes a cardio-metabolic risk cluster, is becoming a global epidemic. It is a pro-inflammatory and pro-oxidant state that confers an increased risk of cardiovascular disease and diabetes. MetS is not only characterized by increased circulating biomarkers of inflammation and oxidative stress but also by dysregulation of a pivotal phagocyte, the circulating monocyte. Pertubations manifesting in monocytes of patients with MetS include increased Toll-like receptors, CD40-CD40L dyad, increased ER stress, increased CCR5 and Fc-γ receptors (CD32 and CD64). Additionally, the monocytes demonstrate increase in NADPH oxidase activity and decreased Nrf2, resulting in oxidative damage to biomolecules. Thus the dysregulated monocyte in MetS appears to be a critical cell in the predisposition of MetS patients to diabetes and CVD. Therapeutic strategies targeting monocytes can attenuate this risk and the most compelling data derives from studies with statin therapy.

Differences in the redox status of human visceral and subcutaneous adipose tissues--relationships to obesity and metabolic risk

OBJECTIVE

Metabolic homeostasis depends on adipocyte metabolic responses/processes, most of which are redox-regulated. Besides, visceral and subcutaneous adipose tissues (VAT and SAT, respectively) differ metabolically and in their contribution to metabolic complications, but their redox characteristics in humans are still unknown. To understand the molecular mechanisms of metabolic syndrome development, we analysed the redox characteristics of VAT and SAT in groups with various body weights and metabolic risks.

MATERIAL AND METHODS

Fifty premenopausal women were classified according to body mass index into normal-weight and obese groups, and these groups were further sub-classified into metabolically healthy and metabolically obese ("at risk") based on the homeostasis model assessment of insulin resistance (HOMA-IR) index and the triglyceride, total-, LDL- and HDL-cholesterol levels. Antioxidant components, NADPH oxidase protein and 4-hydroxynonenal (4-HNE) levels were analysed in VAT and SAT.

RESULTS

Compared with the SAT, the VAT showed a higher basal level of glutathione (GSH) and GSH-dependent enzyme activities. Compared with the metabolically healthy normal-weight controls, the obese groups of women showed lower GSH levels in both depots. However, in these groups, additional prooxidative changes (increased NADPH oxidase and 4-HNE and decreased levels of SOD and/or CAT) were observed only in VAT.

CONCLUSIONS

Because of the critical role of thiol-redox homeostasis in lipogenesis, interdepot-differences in the GSH-dependent antioxidant part may be connected to the higher metabolic activity found in VAT. Analogously, the lower GSH levels that occur during obesity and the corresponding additional redox imbalance may be signs of VAT metabolic dysfunction that underlie the subsequent metabolic impairment.

Hemostatic and Fibrinolytic Changes Are Related to Inflammatory Conditions in Patients with Psoriatic Arthritis — Effect of Different Treatments

Objective.

To prospectively evaluate the effect of tumor necrosis factor (TNF)-α inhibitors on hemostatic and fibrinolytic variables in subjects with psoriatic arthritis (PsA).

Methods.

Among subjects with PsA who were taking traditional disease-modifying antirheumatic drugs (DMARD), 98 patients with active disease who switched to treatment with TNF-α inhibitors were enrolled in this study (Group 1). In parallel, 98 matched subjects with minimal disease activity (MDA) and treated with DMARD were enrolled (Group 2). In all patients, hemostatic and fibrinolytic variables were evaluated at enrollment and after a 6-month followup. Results were stratified according to treatment and to MDA achievement.

Results.

Seventy-six Group 1 and 80 Group 2 subjects completed the 6-month followup. During the followup, significant changes in hemostatic and fibrinolytic variables were found in Group 1, but not in Group 2 subjects. At the end of the followup, patients treated with TNF-α inhibitors showed significantly lower levels of hemostatic and fibrinolytic variables as compared to those treated with traditional DMARD. Among Group 1 subjects, changes in hemostatic and fibrinolytic variable levels were significantly higher in those who achieved MDA versus in those who did not. Multivariate analyses showed that a treatment with TNF-α blockers affected fibrinolytic variables [plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (t-PA)] and some acute-phase proteins (D-dimer, coagulation factor VIII, and von Willebrand factor). In contrast, the MDA achievement during treatment with TNF-α blockers maximally affected fibrinolytic variables (PAI-1 and t-PA).

Conclusion.

TNF-α inhibitors brought about a significant improvement of hemostatic and fibrinolytic balance in subjects with PsA. Maximal changes were found in patients achieving MDA.

Relationship between oxidized LDL, IgM, and IgG autoantibodies to ox-LDL levels with recurrent cardiovascular events in Swedish patients with previous myocardial infarction

We determined whether plasma levels of circulating oxidized low-density lipoprotein (LDL; E06), immunoglobulin (Ig) G, and IgM autoantibodies binding to malonyldialdehyde-modified LDL (MDA-LDL) may predict cardiovascular events (CVEs). Patients (n=123) with a previous myocardial infarction (MI) were included. The primary end point was defined as any of the following: cardiovascular death from any cause, nonfatal reinfarction or stroke, percutaneous coronary intervention, coronary artery bypass grafting, and hospitalization due to angina pectoris. There were 43 CVEs during the follow-up period of 8.4±3.5 years. There was no significant difference in the levels of E06 and MDA-LDL IgG between the CVE and the event-free group. However, MDA-LDL IgM levels were significantly lower in patients in the CVE group (9524±6326 relative light unit [RLU]) compared with the event-free (10,975±5398 RLU) group (P=.04). In conclusion, levels of MDA-LDL IgM were associated with an increased risk of CVE in patients with a previous MI.

Elevated concentration of oxidized LDL together with poor cardiorespiratory and abdominal muscle fitness predicts metabolic syndrome in young men

BACKGROUND

Metabolic syndrome (MetS) is associated with increased oxidized LDL (ox-LDL), systemic inflammation, and poor cardiorespiratory fitness. We examined affiliations of these factors and the effect of muscular fitness on MetS in young healthy men.

METHODS

Physical fitness, ox-LDL, tumor necrosis factor α (TNFα), interleukin-6 (IL-6) and serum lipids were measured in a nationally representative sample of Finnish young men with and without MetS. Participants (mean age 25.1years) performed tests of maximal oxygen uptake (VO₂max) and muscle fitness, and were divided into MetS (n=54, IDF 2007 criteria) and non-MetS (n=790). Age, smoking and leisure-time physical activity were used as covariates (ANCOVA).

RESULTS

The MetS group had lower results in VO₂max and all of the muscular fitness tests (excluding grip strength) (P<0.0001, in all). Ox-LDL, ox-LDL/HDL-cholesterol, ox-LDL/LDL-cholesterol, TNFα and IL-6 were all higher in the MetS group than in the non-MetS group (P<0.01, in all). In stepwise multivariate logistic regression analysis (adjusted to MetS criteria), higher ox-LDL (OR 1.118, 95% CI 1.078-1.160), lower VO₂max (OR 0.938, 95% CI 0.901-0.977) and lower sit-ups (OR 0.898, 95% CI 0.844-0.956) predicted MetS (p<0.05, in all).

CONCLUSIONS

Young men with MetS possess significantly poorer cardiorespiratory and muscle fitness, together with elevated systemic levels of ox-LDL, TNFα and IL-6 compared to non-MetS young men. Of these variables, ox-LDL, VO₂max and sit-ups predicted MetS. Based on these findings, poor physical fitness and elevated concentration of ox-LDL are significant predisposing factors in the development of MetS.

Oxidative stress is associated with C-reactive protein in nondiabetic postmenopausal women, independent of obesity and insulin resistance

OBJECTIVE

Oxidative stress is associated with obesity, metabolic syndrome and inflammation, suggesting it could be an early event in the pathology of chronic diseases. We tested the hypothesis that elevated levels of oxidative stress markers are associated with increased C-reactive protein (CRP) and that this is independent of obesity and insulin resistance.

RESEARCH DESIGN AND METHODS

This study was cross-sectional designed and nondiabetic postmenopausal women (n = 1821) with CRP levels ≤10 mg/l was enrolled. The CRP levels were categorized into quartiles from the lowest to the highest concentrations (Q1-Q4). The degree of insulin resistance was determined using the homoeostasis model assessment of insulin resistance (HOMA-IR). We measured oxidative stress using urinary 8-epi-prostaglandin F2α (8-epi-PGF2α) and plasma oxidized low-density lipoprotein (ox-LDL).

RESULTS

After adjustments for age and lifestyle habits, including smoking and drinking, we found higher body mass index (BMI) and HOMA-IR scores in Q2 and Q3 vs Q1. The Q4 BMI and HOMA-IR scores were higher than all other quartiles. The plasma ox-LDL was higher in Q4 than in Q1. Urinary 8-epi-PGF2α was higher in Q3 and Q4 than in Q1 or Q2. Urinary 8-epi-PGF2α positively correlated with CRP (r = 0·235, P < 0·001), whereas no correlation was found between ox-LDL and CRP. Multiple linear regression analyses of BMI and HOMA-IR showed that the association between urinary 8-epi-PGF2α and CRP levels remained significant (P < 0·001).

CONCLUSIONS

Oxidative stress measured by increased concentration of urine 8-epi-PGF2α is strongly associated with CRP levels. This finding was independent of obesity and insulin resistance in nondiabetic postmenopausal women.

LDL Oxidation and Its Association With Carotid Artery Intima-Media Thickness and Other Cardiovascular Risk Factors in a Sample of Spanish General Population

We studied the association between oxidized low-density lipoproteins (OxLDLs) and early atherosclerosis, assessed by carotid artery intima-media thickness (cIMT), as well as with other known atherosclerosis risk factors in a sample of the general middle- and old-age population of Burgos (Spain). Circulating OxLDL showed a significant and independent association with the average cIMT of both carotid arteries but not with the absence or presence of ≥1 carotid atheroma plaques. Plasma OxLDL concentrations were associated with age, smoking, low-density lipoprotein-cholesterol, and triglycerides, independently of other variables. Our findings in an asymptomatic sample representative of the Spanish middle- and old-age population underscore the role of OxLDL in early atherosclerosis represented by the cIMT especially in older asymptomatic individuals, but this cannot be extended to more advanced atherosclerosis, represented by carotid plaques.

Increased oxidative stress in normal-weight postmenopausal women with metabolic syndrome compared with metabolically healthy overweight/obese individuals

OBJECTIVE

The purpose of this study was to assess whether the metabolically healthy overweight/obese phenotype is associated with decreased oxidative stress compared with normal-weight individuals with metabolic syndrome (MetS).

MATERIALS/METHODS

Plasma oxidized LDL (ox-LDL) and urinary 8-epi-prostaglandin F2α (8-epi-PGF2α) were analyzed in a cross-sectional study of 1846 healthy postmenopausal women. Participants were classified by presence (n=569) or absence (n=1277) of MetS and by BMI (18.5-24.9kg/m(2)=normal weight, n=1254; ≥25kg/m(2)=overweight/obese, n=592). MetS was diagnosed with the modified National Cholesterol Education Program Adult Treatment Panel III criteria.

RESULTS

Compared to normal weight women with MetS (n=296), metabolically healthy overweight/obese women (n=319) showed lower blood pressure, triglyceride, and glucose and higher HDL cholesterol, adiponectin, and LDL particle size. Ox-LDL was higher in overweight/obese women without MetS than in normal weight women without MetS (n=958) but was lower than in women with MetS. Urinary 8-epi-PGF2α level was about 11% lower in women without MetS than in women with MetS. Normal weight women with MetS had greater odds of having ox-LDL (multivariate odds ratio [OR] 2.42, 95% CI: 1.65-3.55) and 8-epi-PGF2α (OR 1.49; CI: 1.03-2.14) levels in the top quartile compared to normal weight women without MetS after adjusting for age, drinking, smoking, total- and LDL-cholesterol, and high sensitivity C-reactive protein. Additionally, there was no significant correlation between ox-LDL and 8-epi-PGF2α.

CONCLUSIONS

The metabolically healthy overweight/obese phenotype was associated with a better overall metabolic profile and less oxidative stress than that observed in normal weight individuals with MetS. Furthermore, there was a lack of association between ox-LDL and 8-epi-PGF2α.

Protein oxidation in a group of subjects with metabolic syndrome

AIMS

To examine the protein oxidation, marker of the oxidative stress, in metabolic syndrome (MS).

METHODS

We enrolled 106 subjects (45 women and 61 men) with MS of which 43 (14 women and 27 men) were with diabetes mellitus and 63 (31 women and 32 men) were without diabetes mellitus, and 54 subjects (19 women and 35 men) as control group. The protein oxidation, expressed as carbonyl groups, was measured by an enzyme-like immunosorbent assay (ELISA) kit (BioCell PC test kit, Enzo Life Sciences AG, Switzerland).

RESULTS

In the whole group of MS subjects, in comparison with control group, a significant increase in carbonyl groups was present. The same datum was also evident between control group and diabetic subjects with MS and between control group and nondiabetic subjects with MS. No difference was observed between the two subgroups (diabetic and nondiabetic subjects with MS) about NOx. Few information were obtained examining the linear regression among carbonyl groups, age, BMI, waist circumference, blood pressure values and metabolic pattern of MS subjects.

CONCLUSIONS

In MS subject we observed an increase of protein oxidation not influenced by diabetes mellitus. Several strategies may be employed to reduce this parameter.

[Relationships among Oxidative Stress Markers, Life Style Factors and Biochemical Findings.]

BACKGROUND

In many studies, oxidative stress markers have been employed to serve as a measure of a disease process or to reflect oxidative status. These oxidative stress markers must have some degree of predictive validity, but full substantiation of this relation is still lacking. This paper presents data on levels of three biomarkers, oxidized low-density lipoproteins (LDL), carbonyl, and 8-hydroxy-2'-deoxyguanosine (8-OHdG), and a number of life style factors associated with oxidative stress in healthy adults.

METHODS

For 237 healthy adults aged 40-60 years, a number of life style factors, biochemical characteristics and oxidative status were evaluated. Markers of oxidative stress were measured by an ELISA method.

RESULTS

Waist-hip ratio and use of vitamin supplement were associated with serum oxidized LDL (P<0.05). Body mass index and stress had a relationship (P<0.05) with protein carbonyl. Creactive protein was related to serum oxidized LDL (P<0.01). There was no correlation among three oxidative stress markers, oxidized LDL, carbonyl, and 8-OHdG.

CONCLUSIONS

The oxidative stress markers used in this study could not be regarded as a general estimate of the healthy individual oxidative status. Further studies focusing on the development of biomarkers to reflect changes in the oxidative status under normal, non-pathological conditions in humans will be required.

Nebivolol and metoprolol: long-term effects on inflammation and oxidative stress in essential hypertension

Arterial hypertension is characterised by increased oxidative stress and inflammation, which are associated with further cardiovascular risk. The aim of our study was to investigate the long-term effects of nebivolol and metoprolol succinate on oxidative stress, and on inflammatory and pro-inflammatory markers in patients with hypertension. Eighty patients with never-treated mild-to-moderate essential hypertension, aged 30-65 years, were randomised to a 5 mg daily dose of nebivolol or a 50-100 mg daily dose of metoprolol succinate. Brachial blood pressure, plasma oxidized LDL (oxLDL), interleukin-6 (IL-6), high-sensitivity C-reactive protein (hsCRP), fibrinogen, intercellular adhesion molecule-1 (ICAM-1), asymmetric dimethylarginine (ADMA), and urine 8-isoprostane levels were measured before and after 1 year of treatment. Nebivolol and metoprolol reduced equally significantly brachial blood pressure. The oxLDL was significantly reduced in both groups (p < 0.01 and for both drugs), but only nebivolol reduced 8-isoprostanes (p = 0.01). In the metoprolol group, change in oxLDL levels correlated with change in systolic blood pressure (r = 0.45; p < 0.01) and pulse pressure (r = 0.47; p < 0.01). Both metoprolol and nebivolol reduced ICAM-1 (p < 0.01). There was no change in IL-6, hsCRP, fibrinogen, or ADMA levels in either group. These data suggest that in long-term antihypertensive treatment both the cardioselective beta blocker metoprolol succinate and the vasodilating beta blocker nebivolol have inflammation-related effects but only nebivolol has a favourable blood pressure-independent effect on oxidative stress.

The relation between carotid plaque echogenicity and oxidative stress marker 8-iso-prostaglandin F2α

Echolucent plaques are associated with high risk of ischemic cerebrovascular events. Oxidative stress has been implicated in the process of atherosclerotic plaque development from initiation to progression. We assessed the relation between carotid plaque echogenicity and urinary 8-iso-prostaglandin F2α, as an index of oxidative stress. This cross-sectional study was conducted prospectively on 290 consecutive outpatients. Each patient was evaluated for carotid plaque echogenicity using the gray-scale median at the maximal thickness plaque and urinary 8-iso-prostaglandin F2α using enzyme linked immunosorbent assay. By Pearson correlation analysis, we found significant negative linear relation between gray-scale median values and the urinary 8-iso-prostaglandin F2α levels (r = -0.133, p = 0.023). This correlation remained significant after adjustment for atherosclerotic risk factors, thickness of the maximal plaque and medication use (β = -0.137, p = 0.031). We herein show that higher levels of urinary 8-iso-prostaglandin F2α is associated with lower plaque echogenicity.

Oxidative stress and metabolic syndrome in a Japanese female population

AIM

One of the methods to evaluate oxidative stress in clinical medical settings is the reactive oxygen metabolites (d-ROMs) test. While metabolic syndrome (MetS) is considered an oxidative condition, the oxidative status in MetS has not been fully examined using this test. The aim of the present study was to investigate the possible association between oxidative stress as evaluated by the d-ROMs test and the MetS component number, in a Japanese female population.

METHODS

The serum oxidant capacity (measured by the d-ROMs test) was cross-sectionally determined in cardiovascular disease-free and non-smoking women who were not taking medications (n = 180; mean age, 60 ± 10 (standard deviation) years). Their MetS state was determined by the National Cholesterol Education Program Adult Treatment Panel recommendations with minor modifications for a Japanese population.

RESULTS

Patients with MetS (n = 60, 362 ± 53 CARR U) showed a significantly higher oxidant capacity by d-ROMs than those without MetS (n = 120, 324 ± 55 CARR U, P < 0.01). Moreover, the significant increase in the oxidant capacity by d-ROMs was closely associated with an increase in the MetS component number (trend P < 0.01).

CONCLUSIONS

These results showed a significantly positive association between the oxidant capacity (by d-ROMs) and the MetS component number in this population. Further studies are required to establish the clinical applications of this test to MetS practice and clarify the biological mechanisms of the observed relationships.

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.

LDL from obese patients with the metabolic syndrome show increased lipid peroxidation and activate platelets

AIMS/HYPOTHESIS

This study assessed oxidative stress in LDL from obese patients with the metabolic syndrome and compared it with that in LDL from type 2 diabetic patients or control volunteers. It also determined the effect on platelets of LDL from the three groups.

METHODS

The profiles of lipids, fatty acids and fatty acid oxidation products were determined in LDL isolated from plasma of patients with the metabolic syndrome, patients with type 2 diabetes and volunteers (n = 10 per group). The effects of LDL from the participant groups on the platelet arachidonic acid signalling cascade and aggregation were investigated.

RESULTS

Compared with LDL from control volunteers, LDL from obese metabolic syndrome and type 2 diabetic patients had lower cholesteryl ester, higher triacylglycerol and lower ethanolamine plasmalogen levels. Proportions of linoleic acid were decreased in phosphatidylcholine and cholesteryl esters in LDL from both patient groups. Among the markers of lipid peroxidation, oxidation products of linoleic acid (hydroxy-octadecadienoic acids) and malondialdehyde were increased by 59% and twofold, respectively in LDL from metabolic syndrome and type 2 diabetic patients. LDL from metabolic syndrome and type 2 diabetic patients were equally potent in activating the platelet arachidonic acid signalling cascade through increased phosphorylation of p38 mitogen-activated protein kinase and cytosolic phospholipase A(2), and through increased thromboxane B(2) formation. LDL from patients with the metabolic syndrome and type 2 diabetes potentiated platelet aggregation by threefold and 3.5-fold respectively, whereas control LDL had no activating effects on platelets.

CONCLUSIONS/INTERPRETATION

The metabolic syndrome in obese patients, without or with diabetes, is associated with increased oxidative stress in LDL, which triggers platelet activation.

The association between reactive oxygen metabolites and metabolic syndrome in asymptomatic Japanese men

Background

The association between the oxidative status and metabolic syndrome (MetS) should be studied in various populations with various oxidative stress-related markers. The aim of this cross-sectional study was to investigate the association between oxidative status, as assessed by the reactive oxygen metabolites (d-ROMs) test, and MetS in asymptomatic Japanese men, in relation to age.

Methods

The serum d-ROMs levels were measured in cardiovascular disease-free, non-smoking, non-medicated males (n = 140), who were divided into groups as follows: Group 1, < 60 years (n = 75, mean age 46 ± 9 [SD] years), and Group 2, ≥ 60 years (n = 65, mean 68 ± 6 years). The MetS was determined by the NCEP-ATP recommendations with minor modifications for a Japanese population.

Results

There was no significant difference in the d-ROMs levels between the subjects with and without MetS in Group 2 (≥ 60 years), but the subjects with MetS (n = 38, 324 ± 59 U. Curr.) exhibited significantly higher d-ROMs levels than those without MetS (n = 37, 290 ± 49 U. Curr., P < 0.01) in Group 1 (< 60 years). These differences did not change even after adjustments for basic confounders.

Conclusions

These results suggest that oxidative status, as assessed by the d-ROMs, can be enhanced among asymptomatic younger, but not older, Japanese males with MetS. Further studies are required to establish the observed associations.

Keywords

Oxidative stress; Reactive oxygen species; D-ROMs; Obesity; Metabolic syndrome

Interstitial F(2)-isoprostane 8-iso-PGF(2α) as a biomarker of oxidative stress after severe human traumatic brain injury

Oxidative stress is a major contributor to the secondary injury process after experimental traumatic brain injury (TBI). The importance of oxidative stress in the pathobiology of human TBI is largely unknown. The F(2)-isoprostane 8-iso-prostaglandin F(2α) (8-iso-PGF(2α)), synthesized in vivo through non-enzymatic free radical catalyzed peroxidation of arachidonic acid, is a widely used biomarker of oxidative stress in multiple disease states, including TBI and cerebral ischemia/reperfusion. Our hypothesis is that harvesting of biomarkers directly in the injured brain by cerebral microdialysis (MD) is advantageous because of its high spatial and temporal resolution compared to blood or cerebrospinal fluid sampling. The aim of this study was to test the feasibility of measuring 8-iso-PGF(2α) in MD, ventricular cerebrospinal fluid (vCSF), and plasma samples collected from patients with severe TBI, and to compare the MD signals with MD-glycerol, implicated as a biomarker of oxidative stress, as well as MD-glutamate, a biomarker of excitotoxicity. Six patients (4 men, 2 women) were included in the study, three of whom had a focal/mixed TBI, and three a diffuse axonal injury (DAI). Following the bedside analysis of routine MD biomarkers (glucose, lactate:pyruvate ratio, glycerol, and glutamate), two 12-h MD samples per day were used to analyze 8-iso-PGF(2α) from 24 h up to 8 days post-injury. The interstitial levels of 8-iso-PGF(2α) were markedly higher than the levels obtained from plasma and vCSF (p<0.05), supporting our hypothesis. The MD-8-iso-PGF(2α) levels correlated strongly (p<0.05) with MD-glycerol and MD-glutamate, which are widely used biomarkers of membrane phospholipid degradation/oxidative stress and excitotoxicity, respectively. This study demonstrates the feasibility of analyzing 8-iso-PGF(2α) in MD samples from the human brain. Our results support a close relationship between oxidative stress and excitotoxicity following human TBI. MD-8-iso-PGF(2α) in combination with MD-glycerol may be useful biomarkers of oxidative stress in the neurointensive care setting.

Alteration of PON1 activity in adult and childhood obesity and its relation to adipokine levels

Obesity as a pathogenic disorder is a predisposing factor for cardiovascular diseases and shows an increasing incidence in the industrialized countries. Adipokines such as leptin, adiponectin and resistin have a great impact on the development of atherosclerosis in obesity. Elevated levels of leptin have been found to be atherogenic whereas decreased levels of adiponectin have been proved to be anti-atherogenic in recent studies. The exact role of resistin in the process of atherosclerosis has so far remained uncertain and controversial. In our recent work, we studied the alteration in human paraoxonase-1 (PON1) activity and adipokine levels; furthermore, we also aimed at identifying the potential correlation between these parameters in this metabolic disorder. We investigated the above-mentioned parameters both in adults and in children, with regard to the emerging role of childhood obesity and to get a clearer view of these factors during a whole lifetime. Investigating the adult population with a broad range of body mass index (BMI) we found significantly increased leptin and significantly decreased adiponectin and resistin levels and PON1 activity in the obese group compared to the lean controls. Adiponectin and resistin levels showed significantly positive correlation, while leptin and BMI showed significantly negative correlation with PON1 activity. Our findings were similar in childhood obesity: leptin showed significantly negative correlation, while adiponectin showed significantly positive correlation with PON1 activity. We found gender differences in the univariate correlations of leptin and adiponectin levels with PON1 activity in the adult population. In multiple regression analysis, adiponectin proved to be an independent factor of PON1 activity both in childhood and adult obesity, furthermore thiobarbituric acid-reactive substances (TBARS) also proved to be an independent predictor of the enzyme in adults, reflecting the important role of oxidative stress in obesity. Investigating PON 192 Q/R polymorphism by phenotypic distribution (A/B isoenzyme) in obese children, we found a significant correlation of PON1 arylesterase activity with leptin and adiponectin levels, and of body fat percentage with PON1 192 B isoenzyme. According to our studies, these metabolic changes in obesity predispose to the early development of atherosclerosis throughout our whole lifetime. Decreased activity of PON1 and alterations in adipokine levels in childhood obesity could contribute to an early commencement of this process, detected only later in adulthood by increased cardiovascular morbidity and mortality. Changed levels of leptin, adiponectin, resistin and PON1 activity at all ages, just like 192 Q/R polymorphism determined by phenotypic distribution, may be useful markers beside the general risk factors.

Relationship of oxidized low density lipoprotein with lipid profile and oxidative stress markers in healthy young adults: a translational study

Background

Despite oxidized low density lipoprotein (ox-LDL) plays important roles in the pro-inflammatory and atherosclerotic processes, the relationships with metabolic and oxidative stress biomarkers have been only scarcely investigated in young adult people. Thus, the aim of this study was to assess plasma ox-LDL concentrations and the potential association with oxidative stress markers as well as with anthropometric and metabolic features in healthy young adults.

Methods

This study enrolled 160 healthy subjects (92 women/68 men; 23 ± 4 y; 22.0 ± 2.9 kg/m²). Anthropometry, body composition, blood pressure, lifestyle features, biochemical data, and oxidative stress markers were assessed with validated tools. Selenium, copper, and zinc nail concentrations were measured by atomic absorption spectrophotometry.

Results

Total cholesterol (TC), LDL-c and uric acid concentrations, TC-to-HDL-c ratio, and glutathione peroxidase (GPx) activity were positive predictors of ox-LDL concentrations, while nail selenium level (NSL) was a negative predictor, independently of gender, age, smoking status, physical activity. Those individuals included in the highest tertile of GPx activity (≥611 nmol/[mL/min]) and of NSL (≥430 ng/g of nail) had higher and lower ox-LDL concentrations, respectively, independently of the same covariates plus truncal fat or body mass index, and total cholesterol or LDL-c concentrations.

Conclusions

Ox-LDL concentrations were significantly associated with lipid biomarkers, GPx activity, uric acid concentration, and NSL, independently of different assayed covariates, in young healthy adults. These findings jointly suggest the early and complex relationship between lipid profile and redox status balance.

Carotid intima-media thickness in psoriatic arthritis: differences between tumor necrosis factor-α blockers and traditional disease-modifying antirheumatic drugs

OBJECTIVE

Subjects with psoriatic arthritis (PsA) have an abnormally high prevalence of vascular risk factors (VRFs) and are predisposed to vascular mortality. Tumor necrosis factor (TNF)-α, a major determinant of inflammation, is involved in atherosclerosis. Ultrasonographic carotid intima-media thickness (C-IMT) evaluation allows for subclinical atherosclerosis detection.

METHODS AND RESULTS

Two hundred twenty-four PsA patients (120 on TNF-α blockers and 104 on traditional disease-modifying antirheumatic drugs [DMARDs]) underwent a C-IMT ultrasound assessment. As many as 305 matched subjects without any inflammatory/rheumatologic disease served as controls. The C-IMT of PsA subjects without VRFs was higher (P<0.0001) than that of controls, the C-IMT of PsA subjects with ≥1 VRF(s) was lower (P<0.0001) than that of controls, and the C-IMT was lower (P<0.0001) in those on TNF-α blockers than in those on DMARDs. Carotid plaques were detected in 15.8% of those on TNF-α blockers and in 40.4% of those on DMARDs (P<0.0001). Treatment duration inversely (β=-0.317, P<0.0001) predicted C-IMT in PsA subjects on TNF-α blockers but not in those on DMARDs (P=0.313).

CONCLUSIONS

Among PsA individuals, the C-IMT is higher in subjects on DMARDs than in those on TNF-α blockers. The reduction of inflammation may hamper the cascade that causes the raised vascular risk in PsA patients.

Circulating oxidized low-density lipoproteins and arterial elasticity: comparison between men with metabolic syndrome and physically active counterparts

Background

Accumulation of oxidized low-density lipoproteins in the intimae of arteries and endothelial dysfunction are key events in the development of atherosclerosis. Patients with metabolic syndrome are at high risk for cardiovascular diseases but the linkage between metabolic syndrome and atherosclerosis is incompletely understood. We studied whether the levels of oxidized LDL and arterial elasticity differ between metabolic syndrome patients and physically active controls.

Methods

40 men with metabolic syndrome and 40 physically active controls participated in this cross-sectional study. None of the study subjects had been diagnosed with cardiovascular disease. Levels of oxidized LDL were assessed by a two-site ELISA immunoassay. Arterial elasticity was assessed non-invasively by the HDI/PulseWave™ CR-2000 arterial tonometer.

Results

Levels of oxidized LDL were 89.6 ± 33.1 U/L for metabolic syndrome subjects and 68.5 ± 23.6 U/L for controls (p = 0.007). The difference remained significant after adjustment for LDL cholesterol. Large artery elasticity index (C1) was 16.2 ± 4.1 mL/mmHgx10 for metabolic syndrome subjects and 19.4 ± 3.7 mL/mmHgx10 for controls (p = 0.001), small artery indices (C2) were 7.0 ± 3.2 mL/mmHgx100 and 6.5 ± 2.9 mL/mmHgx100 (NS), respectively.

Conclusions

Subjects with metabolic syndrome had elevated levels of oxidized LDL and reduced large arterial elasticity compared to controls. This finding may partly explain the increased risk for cardiovascular diseases among metabolic syndrome patients.

Trial registration

ClinicalTrials.gov NCT01114763

Markers of oxidative damage are not elevated in otherwise healthy individuals with the metabolic syndrome

OBJECTIVE

The role of oxidative damage in the pathogenesis of metabolic syndrome is poorly understood.

RESEARCH DESIGN AND METHODS

A detailed cross-sectional study was performed to assess the relationship between lipid oxidation products, gamma-glutamyltransferase, high-sensitivity C-reactive protein (hs-CRP), and phospholipase activities with respect to the metabolic status in a cohort of otherwise healthy individuals.

RESULTS

A total of 179 individuals (87 men and 92 women) aged 43 +/- 14 years (mean +/- SD) participated in this study. There were no differences in the levels of plasma F(2)-isoprostanes, hydroxyeicosatetraenoic acids, cholesterol oxidation products, and phospholipase activities in individuals with features of metabolic syndrome. In multivariate analyses, serum hs-CRP was a consistent independent predictor of metabolic syndrome.

CONCLUSIONS

Minimal changes were observed in multiple markers of oxidative damage in a well-characterized cohort of individuals with features of metabolic syndrome.

Comparison of lipid and fatty acid composition of the liver, subcutaneous and intra-abdominal adipose tissue, and serum

Ceramides may mediate saturated fat-induced insulin resistance, but there are no data comparing ceramide concentrations between human tissues. We therefore performed lipidomic analysis of human subcutaneous (SCfat) and intra-abdominal (IAfat) adipose tissue, the liver, and serum in eight subjects. The liver contained (nmol/mg tissue) significantly more ceramides (1.5-3-fold), sphingomyelins (7-8-fold), phosphatidylethanolamines (10-11-fold), lysophosphatidylcholines (7-12-fold), less ether-linked phosphatidylcholines (2-2.5-fold) but similar amounts of diacylglycerols as compared to SCfat and IAfat. The amounts of ceramides and their synthetic precursors, such as palmitic (16:0) free fatty acids and sphingomyelins, differed considerably between the tissues. The liver contained proportionally more palmitic, stearic (18:0), and long polyunsaturated fatty acids than adipose tissues. Stearoyl-CoA desaturase 1 (SCD1) activity reflected by serum, estimated from the 16:1/16:0-ratio, was closely related to that in the liver (r = 0.86, P = 0.024) but not adipose tissues. This was also true for estimated elongase (18:1/16:1, r = 0.89, P = 0.01), and Delta5 (20:4/20:3, r = 0.89, P = 0.012) and Delta6 (18:3[n-6]/18:2, r = 1.0, P < 0.001) desaturase activities. We conclude that the human liver contains higher concentrations of ceramides and saturated free fatty acids than either SCfat or IAfat.

Biomarkers of oxidative stress in heart failure

Oxidative stress is the relative excess of reactive oxygen species (ROS) versus endogenous defense mechanisms. Abundant evidence has demonstrated the role of ROS, along with reactive nitrogen species (RNS), in the pathophysiology of cardiovascular disease, including heart failure. Many biomarkers of oxidative stress have been studied as surrogates of oxidative damage. Recently, markers of impaired nitric oxide signaling have also been identified. Many biomarkers have been associated with prognosis and mortality, and some may even be modified by therapy. However, the clinical utility is limited by less than optimal standardization techniques and the lack of sufficient large-sized, multimarker prospective trials.

Metabolic syndrome and periodontitis: is oxidative stress a common link?

A review of pathological mechanisms that can explain the relationship between periodontitis and cardiovascular disease (CVD) is necessary to improve the management of both conditions. Metabolic syndrome is a combination of obesity, hypertension, impaired glucose tolerance or diabetes, hyperinsulinemia, and dyslipidemia. All these have been examined in recent years in terms of their relationship to periodontitis. Reviewed data indicate an association between some of them (body mass index, high-density lipoprotein-cholesterol [HDL-C], triglycerides, high blood pressure, among others) and periodontitis. Oxidative stress may act as a potential common link to explain relationships between each component of metabolic syndrome and periodontitis. Both conditions show increased serum levels of products derived from oxidative damage, with a pro-inflammatory state likely influencing each other bidirectionally. Adipocytokines might modulate the oxidant/anti-oxidant balance in this relationship.

Serum saturated fatty acids containing triacylglycerols are better markers of insulin resistance than total serum triacylglycerol concentrations

AIMS/HYPOTHESIS

The weak relationship between insulin resistance and total serum triacylglycerols (TGs) could be in part due to heterogeneity of TG molecules and their distribution within different lipoproteins. We determined concentrations of individual TGs and the fatty acid composition of serum and major lipoprotein particles and analysed how changes in different TGs and fatty acid composition are related to features of insulin resistance and abdominal obesity.

METHODS

We performed lipidomic analyses of all major lipoprotein fractions using two analytical platforms in 16 individuals, who exhibited a broad range of insulin sensitivity.

RESULTS

We identified 45 different TGs in serum. Serum TGs containing saturated and monounsaturated fatty acids were positively, while TGs containing essential linoleic acid (18:2 n-6) were negatively correlated with HOMA-IR. Specific serum TGs that correlated positively with HOMA-IR were also significantly positively related to HOMA-IR when measured in very-low-density lipoproteins (VLDLs), intermediate-density lipoproteins (IDLs) and LDL, but not in HDL subfraction 2 (HDL(2)) or 3 (HDL(3)). Analyses of proportions of esterified fatty acids within lipoproteins revealed that palmitic acid (16:0) was positively related to HOMA-IR when measured in VLDL, IDL and LDL, but not in HDL(2) or HDL(3). Monounsaturated palmitoleic (16:1 n-7) and oleic (18:1 n-9) acids were positively related to HOMA-IR when measured in HDL(2) and HDL(3), but not in VLDL, IDL or LDL. Linoleic acid was negatively related to HOMA-IR in all lipoproteins.

CONCLUSIONS/INTERPRETATION

Serum concentrations of specific TGs, such as TG(16:0/16:0/18:1) or TG(16:0/18:1/18:0), may be more precise markers of insulin resistance than total serum TG concentrations.

Oxidized LDL impair adipocyte response to insulin by activating serine/threonine kinases

Oxidized LDL (oxLDL) increase in patients affected by type-2 diabetes, obesity, and metabolic syndrome. Likewise, insulin resistance, an impaired responsiveness of target tissues to insulin, is associated with those pathological conditions. To investigate a possible causal relationship between oxLDL and the onset of insulin resistance, we evaluated the response to insulin of 3T3-L1 adipocytes treated with oxLDL. We observed that oxLDL inhibited glucose uptake (-40%) through reduced glucose transporter 4 (GLUT4) recruitment to the plasma membrane (-70%), without affecting GLUT4 gene expression. These findings were associated to the impairment of insulin signaling. Specifically, in oxLDL-treated cells insulin receptor (IR) substrate-1 (IRS-1) was highly degraded likely because of the enhanced Ser(307)phosphorylation. This process was largely mediated by the activation of the inhibitor of kappaB-kinase beta (IKKbeta) and the c-Jun NH(2)-terminal kinase (JNK). Moreover, the activation of IKKbeta positively regulated the nuclear content of nuclear factor kappaB (NF-kappaB), by inactivating the inhibitor of NF-kappaB (IkappaBalpha). The activated NF-kappaB further impaired per se GLUT4 functionality. Specific inhibitors of IKKbeta, JNK, and NF-kappaB restored insulin sensitivity in adipocytes treated with oxLDL. These data provide the first evidence that oxLDL, by activating serine/threonine kinases, impaired adipocyte response to insulin affecting pathways involved in the recruitment of GLUT4 to plasma membranes (PM). This suggests that oxLDL might participate in the development of insulin resistance.

Circulating oxidized low-density lipoprotein: a biomarker of atherosclerosis and cardiovascular risk?

Low-density lipoproteins (LDLs) are susceptible to structural modifications by oxidation, particularly the small dense LDL particles. The formation of lipid peroxidation derivates, such as thiobarbituric reactive substances, conjugated dienes, lipid hydroperoxides, and aldehydes, is associated with changes in apolipoprotein conformation and affects the functional properties of LDLs. Oxidized LDL (oxLDL) formation in the subendothelial space of the arterial wall is a key initiating step in atherosclerosis because it contributes to foam cell generation, endothelial dysfunction, and inflammatory processes. In the last decade, immunoassays were developed using monoclonal antibodies against oxidation-dependent epitopes of LDL which made it possible to directly measure oxLDL in the circulation. Increased circulating oxLDL concentrations have been related to cardiovascular disease in some studies, although not always independently after adjustment of classical lipid markers. The Asklepios Study, investigating 2524 healthy middle-aged subjects, showed that circulating oxLDL is affected by many biological and lifestyle factors, as well as (generalized) subclinical atherosclerosis.

Clin Chem Lab Med 2009;47:128–37.