N-3 PUFAs reduce oxidative stress in ESRD patients on maintenance HD by inhibiting 5-lipoxygenase activity

LC-MS/MS-based arachidonic acid metabolomics in acute spinal cord injury reveals the upregulation of 5-LOX and COX-2 products

Arachidonic acid (AA) plays a critical role in inflammatory regulation and secondary injury after spinal cord injury (SCI). However, the overall AA metabolism profile in the acute phase of SCI remains elusive. Here we quantified AA metabolomics by High Performance Liquid Chromatography-Tandem Mass Spectrometry-Based Method (LC-MS/MS) using spinal cord tissue collected at 4 h, 24 h and 48 h after contusive SCI in rats. Remarkably, Prostaglandin E2 (PGE2) and Leukotriene B4 (LTB4) were significantly increased throughout the acute SCI. Cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX), the key enzymes involved in the production of PGE2 and LTB4, were elevated in the lesioned spinal cord tissue, validated by both western blot and immunofluorecnce. The spatial-temporal changes of COX-2 and 5-LOX mainly occurs in neurons both in epicenter and rostral and caudal spinal cord segments after SCI. Our study sheds light on the dynamic microenvironment changes in acute SCI by characterizing the profile of AA metabolism. The COX-2 and 5-LOX may be promising therapeutic target for SCI.

Diminished arachidonate 5-lipoxygenase perturbs phase separation and transcriptional response of Runx2 to reverse pathological ventricular remodeling

BACKGROUND

Arachidonate 5-lipoxygenase (Alox5) belongs to a class of nonheme iron-containing dioxygenases involved in the catalysis of leukotriene biosynthesis. However, the effects of Alox5 itself on pathological cardiac remodeling and heart failure remain elusive.

METHODS

The role of Alox5 in pathological cardiac remodeling was investigated by Alox5 genetic depletion, AAV9-mediated overexpression in cardiomyocytes, and a bone marrow (BM) transplantation approach. Neonatal rat cardiomyocytes were used to explore the effects of Alox5 in vitro. Molecular and signaling pathways were revealed by CUT &Tag, IP-MS, RNA sequencing and bioinformatic analyses.

FINDINGS

Untargeted metabolomics showed that serum 5-HETE (a primary product of Alox5) levels were little changed in patients with cardiac hypertrophy, while Alox5 expression was significantly upregulated in murine hypertensive cardiac samples and human cardiac samples of hypertrophy, which prompted us to test whether high Alox5 levels under hypertensive stimuli were directly associated with pathologic myocardium in an enzymatic activity-independent manner. Herein, we revealed that Alox5 deficiency significantly ameliorated transverse aortic constriction (TAC)-induced hypertrophy. Cardiomyocyte-specific Alox5 depletion attenuated hypertensive ventricular remodeling. Conversely, cardiac-specifical Alox5 overexpression showed a pro-hypertrophic cardiac phenotype. Ablation of Alox5 in bone marrow-derived cells did not affect pathological cardiac remodeling and heart failure. Mechanically, Runx2 was identified as a target of Alox5. In this regard, Alox5 PEST domain could directly bind to Runx2 PTS domain, promoting nuclear localization of Runx2 in an enzymatic activity-independent manner, simultaneously contributed to liquid-liquid phase separation (LLPS) of Runx2 at specific domain in the nucleus and increased transcription of EGFR in cardiomyocytes. Runx2 depletion alleviated hypertrophy in Ang II-pretreated Alox5-overexpressing cardiomyocytes.

INTERPRETATION

Overall, our study demonstrated that targeting Alox5 exerted a protective effect against cardiac remodeling and heart failure under hypertensive stimuli by disturbing LLPS of Runx2 and substantial reduction of EGFR transcription activation in cardiomyocytes. Our findings suggest that negative modulation of Alox5-Runx2 may provide a therapeutic approach against pathological cardiac remodeling and heart failure.

FUNDING

National Natural Science Foundation of China.

Blood Levels of Endocannabinoids, Oxylipins, and Metabolites Are Altered in Hemodialysis Patients

Hemodialysis patients (HDPs) have higher blood pressure, higher levels of inflammation, a higher risk of cardiovascular disease, and unusually low plasma n-3 polyunsaturated fatty acid (PUFA) levels compared to healthy subjects. The objective of our investigation was to examine the levels of endocannabinoids (eCBs) and oxylipins (OxLs) in female HDPs compared to healthy matched female controls, with the underlying hypothesis that differences in specific PUFA levels in hemodialysis patients would result in changes in eCBs and OxLs. Plasma phospholipid fatty acids were analyzed by gas chromatography. Plasma was extracted and analyzed using ultra-performance liquid chromatography followed by electrospray ionization and tandem MS for eCBs and OxLs. The global untargeted metabolite profiling of plasma was performed by GCTOF MS. Compared to the controls, HDPs showed lower levels of plasma EPA and the associated OxL metabolites 5- and 12-HEPE, 14,15-DiHETE, as well as DHA derived 19(20)-EpDPE. Meanwhile, no changes in arachidonylethanolamide or 2-arachidonylglycerol in the open circulation were detected. Higher levels of multiple N-acylethanolamides, monoacylglycerols, biomarkers of progressive kidney disease, the nitric oxide metabolism-linked citrulline, and the uremic toxins kynurenine and creatine were observed in HDP. These metabolic differences in cCBs and OxLs help explain the severe inflammatory and cardiovascular disease manifested by HDPs, and they should be explored in future studies.

Lipidomics reveals association of circulating lipids with body mass index and outcomes in IgA nephropathy patients

IgA nephropathy (IgAN) is a leading cause of chronic kidney disease (CKD), which are commonly accompanied by dyslipidemia. Obesity is also associated with dyslipidemia and risk of CKD, but the relation of the dyslipidemia patterns with obesity and disease progression in IgAN patients remains unknown. Traditional Chinese medicine (TCM) and the combined treatment with corticosteroids and TCM have been shown to be of benefit for IgAN patients, but predictive markers for guiding these treatments are lacking. Here, we quantified 545 lipid species in the plasma from 196 participants, including 140 IgAN patients and 56 healthy volunteers, and revealed an altered plasma lipidome in IgAN patients as compared to healthy participants. Association analysis showed that a sub-group of glycerides, particularly triacylglycerols (TGs) containing docosahexaenoic acid, were positively associated with high body mass index (BMI) in under- or normal weight IgAN patients, while several free fatty acids and sphingomyelins were positively associated with high BMI in overweight or obese IgAN patients. Further, our study suggested that elevated levels of eight lipids, mainly TG species containing linolenic acid, were independent risk factors for IgAN progression and also reported the prospective association of circulating lipids with treatment outcomes in IgAN. Taken together, our findings may not only help to achieve precision medicine but also provide a knowledge base for dietary intervention in the treatment of IgAN.

Dietary walnut as food factor to rescue from NSAID-induced gastrointestinal mucosal damages

Nuclear factor erythroid-derived 2-like 2 (Nrf-2) is transcription factor implicated in the antioxidant response element-mediated induction of endogenous antioxidant enzyme such as heme oxygenase-1 (HO-1), glutamate-cysteine ligase, and NAD(P)H quinone dehydrogenase 1, among which HO-1 is an enzyme catalyzing the degradation of heme.producing biliverdin, ferrous iron, and carbon monoxide. In the stomach, as much as regulating gastric acid secretions, well-coordinated establishment of defense system stands for maintaining gastric integrity. In previous study, author et al. for the first time discovered HO-1 induction was critical in affording faithful gastric defense against various irritants including Helicobacter pylori infection, stress, alcohol, non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, and toxic bile acids. In this review article, we can add the novel evidence that dietary walnut intake can be reliable way to rescue from NSAIDs-induced gastrointestinal damages via the induction of HO-1 transcribed with Nrf-2 through specific inactivation of Keap-1. From molecular exploration to translational animal model of indomethacin-induced gastrointestinal damages, significant induction of HO-1 contributed to rescuing from damages. In addition to HO-1 induction action relevant to walnut, we added the description the general actions of walnut extracts or dietary intake of walnut regarding cytoprotection and why we have focused on to NSAID damages.

Polyphyllin VI, a saponin from Trillium tschonoskii Maxim. induces apoptotic and autophagic cell death via the ROS triggered mTOR signaling pathway in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancers. Our previous studies have proven that Trillium tschonoskii Maxim. (TTM), a traditional Chinese medicine, possesses potent anti-tumor effect. However, the detailed components and molecular mechanism of TTM in anti-NSCLC are still unknown. In the present experiment, polyphyllin VI (PPVI) was successfully isolated from TTM with guidance of the anti-proliferative effect in A549 cells, and the cell death of PPVI treated A549 and H1299 cells was closely linked with the increased intracellular ROS levels. In addition, PPVI induced apoptosis by promoting the protein expression of Bax/Bcl2, caspase-3 and caspase-9, and activated autophagy by improving LC3 II conversion and GFP-LC3 puncta formation in A549 and H1299 cells. The mechanism study found that the activity of mTOR which regulates cell growth, proliferation and autophagy was significantly suppressed by PPVI. Accordingly, the PI3K/AKT and MEK/ERK pathways positively regulating mTOR were inhibited, and AMPK negatively regulating mTOR was activated. In addition, the downstream of mTOR, ULK1 at Ser 757 which downregulates autophagy was inhibited by PPVI. The apoptotic cell death induced by PPVI was confirmed, and it was significantly suppressed by the overexpression of AKT, ERK and mTOR, and the induced autophagic cell death which was depended on the Atg7 was decreased by the inhibitors, such as LY294002 (LY), Bafilomycin A1 (Baf), Compound C (CC) and SBI-0206965 (SBI). Furthermore, the mTOR signaling pathway was regulated by the increased ROS as the initial signal in A549 and H1299 cells. Finally, the anti-tumor growth activity of PPVI in vivo was validated in A549 bearing athymic nude mice. Taken together, our data have firstly demonstrated that PPVI is the main component in TTM that exerts the anti-proliferative effect by inducing apoptotic and autophagic cell death in NSCLC via the ROS-triggered mTOR signaling pathway, and PPVI may be a promising candidate for the treatment of NSCLC in future.

Relationship of Omega-3 fatty acids DHA and EPA with the inflammatory biomarker hs-CRP in children with sickle cell anemia

BACKGROUND

Inflammation and vaso-occlusion play key roles in Sickle Cell Disease (SCD) pathophysiology. Lipoxygenase products of the omega-3 fatty acids (O3FAs), docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, are potent anti-inflammatory mediators modulating pain. O3FAs decrease episodes of vaso-occlusion in SCD.

METHODS

We assessed erythrocyte fatty acid composition in two major cell membrane phospholipids, phosphatidylcholine and phosphatidylethanolamine, in children with SCD HbSS-disease (n = 38) and age/race-matched HbAA-controls (n = 18). Ratio of pro-inflammatory arachidonic acid (AA) to anti-inflammatory DHA and EPA (FA-Ratio), and its relationship to hs-CRP were evaluated.

RESULTS

FA-Ratios were increased in both phosphatidylcholine and phosphatidylethanolamine in HbSS compared to controls. Correlations were noted in HbSS subjects between hs-CRP and FA-Ratios (p = 0.011). FA-Ratios increased with age (p = 0.0007) due to an increase in pro-inflammatory AA with a concomitant decrease in anti-inflammatory DHA.

CONCLUSIONS

Findings demonstrate relative deficiencies in HbSS of the anti-inflammatory precursor fatty acids DHA and EPA, which correlates positively with hs-CRP.

Effect of omega-3 fatty acid plus vitamin E Co-Supplementation on oxidative stress parameters: A systematic review and meta-analysis

BACKGROUND & AIMS

The impact of combined omega-3 FAs and vitamin E supplementation on oxidative stress (OS) has been evaluated in several studies. However the results are inconsistent. Therefore, we performed a systematic review and meta-analysis to assess the role of omega-3 FAplus vitamin E on anti-oxidant and OS parameters.

METHODS

We searched five databases (PubMed, Embase, Web of Sciences, Scopus and the Cochrane Central Register of Controlled Trials) from inception until March 15th 2018 for RCT covering OS parameters combined with omega-3 FAs and vitamin E. The effect of omega-3 FAs plus vitamin E combination on OS factors was determined as the standardized mean difference (SMD) calculated according to DerSimonian and Laird for the random effects model.

RESULTS

Nine articles were included in our analyses, significant improvements were observed in trials supplementing with omega-3 FAs plus vitamin E vs placebo for total antioxidant capacity (TAC) (SMD=0.63, 95%CI: 0.31 to 0.95, P<0.001) and nitric oxide (NO) (SMD=0.55, 95%CI: 0.23 to 0.87, P<0.001). Significant reduction was observed for malondialdehyde (MDA) (SMD: -0.48, 95%CI: -0.68 to -0.28, P<0.001). However, the results of meta-analysis did not show a significant difference in levels of glutathione (GSH) (SMD=0.34, 95%CI: -0.07 to 0.75, P=0.10), superoxide dismutase (SOD) activity (SMD: 0.07, 95% CI: -0.58 to 0.73, P=0.82) and Catalase (CAT) activity (SMD: 0.74, 95% CI: -0.30 to 1.79, P=0.16).

CONCLUSION

Co-supplementation with omega-3 FAs and vitamin E increases the levels of NO and TAC, while MDA levels decrease compared to placebo. However, the results showed no significant alterations on GSH concentrations, CAT, and SOD activities.

Omega-3 fatty acids in coronary heart disease: Recent updates and future perspectives

Incidence of coronary heart disease (CHD) increases worldwide with varying etiological factors. In addition to the control of risk factors, dietary modification has been recommended to reduce the prevalence. Omega-3 (ω-3) fatty acids (FAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), of fish oil are beneficial for the prevention of CHD. The effect can be ascribed to anti-inflammatory, vasodilating, antiarrhythmic, antihypertensive activities and lowering of triacyl glycerol level. The American Heart Association advises two fish meals per week in subjects without CHD or supplementation of 1 g of EPA plus DHA per day in subjects with CHD. Despite the beneficial effects of EPA/DHA reported in some of the clinical trials, results of many others were inconsistent that can be ascribed to short duration of studies, low doses of ω-3 FAs, variations in the EPA:DHA ratio, selection of patients with different risk factors or interaction of ω-3 FAs with drugs used in the therapy. Therefore, well designed clinical trials in various populations are warranted. This article discusses the current situation and future prospective of ω-3 FAs in CHD.

Omega-3 Polyunsaturated Fatty Acid Derived Lipid Mediators and their Application in Drug Discovery

Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) play crucial and often opposing regulatory roles in health and in pathological conditions. n-3 and n-6 PUFA undergo biotransformation to parallel series of lipid mediators that are potent modulators of many cellular processes. A wide range of biological actions have been attributed to lipid mediators derived from n-6 PUFA, and these mediators have served as lead compounds in the development of numerous clinically approved drugs, including latanoprost (Xalatan: Pfizer), which is listed on the WHO Model List of Essential Medicines. n-3 PUFA-derived mediators have received less attention, in part because early studies suggested that n-3 PUFA act simply as competitive substrates for biotransformation enzymes and decrease the formation of n-6 PUFA-derived lipid mediators. However, more recent studies suggest that n-3 PUFA-derived mediators are biologically important in their own right. It is now emerging that many n-3 PUFA-derived lipid mediators have potent and diverse activities that are distinct from their n-6 counterparts. These findings provide new opportunities for drug discovery. Herein, we review the biosynthesis of n-3 PUFA-derived lipid mediators and highlight their biological actions that may be exploited for drug development. Lastly, we provide examples of medicinal chemistry research that has utilized n-3 PUFA-derived lipid mediators as novel lead compounds in drug design.

Eicosapentaenoic Acid and Prevalence of Cardiovascular Disease in Hemodialysis Patients

Eicosapentaenoic acid (EPA)/arachidonic acid (AA) ratio showed inverse associations with cardiovascular disease (CVD) in general population. However, this has not been examined enough in dialysis patients. We cross-sectionally investigated the relationship between EPA/AA ratio and prevalence of CVD in 321 chronic hemodialysis patients (64 ± 11 years old; 110 women; dialysis vintage 10 ± 8 years) in an urban area of Tokyo. CVD was defined as a composite of ischemic heart disease, ischemic stroke and hemorrhagic stroke. The frequency of dietary fish intake was also examined. Logistic regression was used to quantify the association of EPA/AA ratio with CVD. EPA/AA ratio was 0.31 ± 0.19 and 154 patients (48%) consumed fish once or less weekly. One hundred and thirty patients (41%) had CVD, including 65 with ischemic heart disease, 70 with ischemic stroke, and 20 with hemorrhagic stroke. Age (odds ratio [OR], 1.04; P = 0.01), hypertension (OR, 2.25; P = 0.002), and dialysis vintage (OR, 1.04; P = 0.02) were associated with CVD; however, EPA/AA was not after adjustment for other risk factors. A similar relationship was observed between fish intake and CVD prevalence. We did not find any significant association between EPA/AA ratio and prevalence of CVD, although traditional risk factors such as age, hypertension and dialysis vintage were associated with CVD. These results might have been influenced by the fact that only a small proportion of our patients showed a high EPA/AA ratio.

Effect of Omega-3 Fatty Acid Supplementation on Plasma Fibroblast Growth Factor 23 Levels in Post-Myocardial Infarction Patients with Chronic Kidney Disease: The Alpha Omega Trial

Fibroblast growth factor 23 (FGF23) is an independent risk factor for cardiovascular mortality in chronic kidney disease. Omega-3 (n-3) fatty acid consumption has been inversely associated with FGF23 levels and with cardiovascular risk. We examined the effect of marine n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and plant-derived alpha-linolenic acid (ALA) on plasma FGF23 levels in post-myocardial infarction patients with chronic kidney disease. In the randomized double-blind Alpha Omega Trial, 4837 patients with a history of myocardial infarction aged 60-80 years (81% men) were randomized to one of four trial margarines supplemented with a targeted additional intake of 400 mg/day EPA and DHA, 2 g/day ALA, EPA-DHA plus ALA, or placebo for 41 months. In a subcohort of 336 patients with an eGFR < 60 mL/min/1.73 m² (creatinine-cystatin C-based CKD-EPI formula), plasma C-terminal FGF23 was measured by ELISA at baseline and end of follow-up. We used analysis of covariance to examine treatment effects on FGF23 levels adjusted for baseline FGF23. Patients consumed 19.8 g margarine/day on average, providing an additional amount of 236 mg/day EPA with 158 mg/day DHA, 1.99 g/day ALA or both, in the active intervention groups. Over 79% of patients were treated with antihypertensive and antithrombotic medication and statins. At baseline, plasma FGF23 was 150 (128 to 172) RU/mL (mean (95% CI)). After 41 months, overall FGF23 levels had increased significantly (p < 0.0001) to 212 (183 to 241) RU/mL. Relative to the placebo, the treatment effect of EPA-DHA was indifferent, with a mean change in FGF23 (95% CI) of -17 (-97, 62) RU/mL (p = 0.7). Results were similar for ALA (36 (-42, 115) RU/mL) and combined EPA-DHA and ALA (34 (-44, 113) RU/mL). Multivariable adjustment, pooled analyses, and subgroup analyses yielded similar non-significant results. Long-term supplementation with modest quantities of EPA-DHA or ALA does not reduce plasma FGF23 levels when added to cardiovascular medication in post-myocardial patients with chronic kidney disease.

High Dose Omega-3 Fatty Acid Administration and Skeletal Muscle Protein Turnover in Maintenance Hemodialysis Patients

BACKGROUND AND OBJECTIVES

Protein energy wasting and systemic inflammation are prevalent in maintenance hemodialysis (MHD) patients. Omega-3 (ω-3) fatty acids have anti-inflammatory properties and have been shown to improve protein homeostasis. We hypothesized that administration of high-dose (2.9 g/d) ω-3 would be associated with decreased muscle protein breakdown in MHD patients with systemic inflammation.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

This is a substudy from a randomized, placebo-controlled study (NCT00655525). Patients were recruited between September 2008 and June 2011. Primary inclusion criteria included signs of chronic inflammation (average C-reactive protein of ≥5 mg/L over three consecutive measurements), lack of active infectious or inflammatory disease, no hospitalization within 1 month prior to the study, and not receiving steroids (>5 mg/d) and/or immunosuppressive agents. The primary outcomes were forearm muscle and whole body protein breakdown and synthesis before and after the intervention. The patients received ω-3 (n=11) versus placebo (n=9) for 12 weeks. Analysis of covariance was used to compare outcome variables at 12 weeks. Models were adjusted for a propensity score that was derived from age, sex, race, baseline high sensitivity C-reactive protein, diabetes mellitus, and fat mass because the groups were not balanced for several characteristics.

RESULTS

Compared with placebo, ω-3 supplementation was significantly associated with decreased muscle protein breakdown at 12 weeks (-31, [interquartile range, -98--13] versus 26 [interquartile range, 13-87] µg/100 ml per min; P=0.01), which remained significant after multivariate adjustment (-46, [95% confidence interval, -102 to -1] µg/100 ml per min). ω-3 Supplementation resulted in decreased forearm muscle protein synthesis while the rate in the placebo group increased; however, there is no longer a statistically significant difference in skeletal muscle protein synthesis or in net protein balance after multivariate adjustment. There was no statistically significant effect of ω-3 supplementation on whole body protein synthesis or breakdown.

CONCLUSIONS

High-dose ω-3 supplementation over 12 weeks in MHD patients with systemic inflammation was associated with attenuation of forearm muscle protein breakdown but did not influence skeletal muscle protein synthesis, skeletal muscle net protein balance or any component of the whole-body protein balance. These results should be interpreted cautiously given the imbalance in the two groups and the short duration of the intervention.

Mitochondria: a new therapeutic target in chronic kidney disease

Cellular metabolic changes during chronic kidney disease (CKD) may induce higher production of oxygen radicals that play a significant role in the progression of renal damage and in the onset of important comorbidities. This condition seems to be in part related to dysfunctional mitochondria that cause an increased electron "leakage" from the respiratory chain during oxidative phosphorylation with a consequent generation of reactive oxygen species (ROS). ROS are highly active molecules that may oxidize proteins, lipids and nucleic acids with a consequent damage of cells and tissues. To mitigate this mitochondria-related functional impairment, a variety of agents (including endogenous and food derived antioxidants, natural plants extracts, mitochondria-targeted molecules) combined with conventional therapies could be employed. However, although the anti-oxidant properties of these substances are well known, their use in clinical practice has been only partially investigated. Additionally, for their correct utilization is extremely important to understand their effects, to identify the correct target of intervention and to minimize adverse effects. Therefore, in this manuscript, we reviewed the characteristics of the available mitochondria-targeted anti-oxidant compounds that could be employed routinely in our nephrology, internal medicine and renal transplant centers. Nevertheless, large clinical trials are needed to provide more definitive information about their use and to assess their overall efficacy or toxicity.

Anti-tumor activities of lipids and lipid analogues and their development as potential anticancer drugs

Lipids have the potential for development as anticancer agents. Endogenous membrane lipids, such as ceramides and certain saturated fatty acids, have been found to modulate the viability of tumor cells. In addition, many tumors over-express cyclooxygenase, lipoxygenase or cytochrome P450 enzymes that mediate the biotransformation of ω-6 polyunsaturated fatty acids (PUFAs) to potent eicosanoid regulators of tumor cell proliferation and cell death. In contrast, several analogous products from the biotransformation of ω-3 PUFAs impair particular tumorigenic pathways. For example, the ω-3 17,18-epoxide of eicosapentaenoic acid activates anti-proliferative and proapoptotic signaling cascades in tumor cells and the lipoxygenase-derived resolvins are effective inhibitors of inflammatory pathways that may drive tumor expansion. However, the development of potential anti-cancer drugs based on these molecules is complex, with in vivo stability a major issue. Nevertheless, recent successes with the antitumor alkyl phospholipids, which are synthetic analogues of naturally-occurring membrane phospholipid esters, have provided the impetus for development of further molecules. The alkyl phospholipids have been tested against a range of cancers and show considerable activity against skin cancers and certain leukemias. Very recently, it has been shown that combination strategies, in which alkyl phospholipids are used in conjunction with established anticancer agents, are promising new therapeutic approaches. In future, the evaluation of new lipid-based molecules in single-agent and combination treatments may also be assessed. This could provide a range of important treatment options in the management of advanced and metastatic cancer.

Docosahexaenoic acid supplementation promotes erythrocyte antioxidant defense and reduces protein nitrosative damage in male athletes

The aim of this study was to determine the influence of long-term docosahexaenoic acid (DHA) dietary supplementation on the erythrocyte fatty acid profile and oxidative balance in soccer players after training and acute exercise. Fifteen volunteer male athletes (age 20.0 ± 0.5 years) were randomly assigned to a placebo group that consumed an almond-based beverage (n = 6), or to an experimental group that consumed the same beverage enriched with DHA (n = 9) for 8 weeks. Blood samples were taken in resting conditions at the beginning and after 8 weeks of nutritional intervention and training in resting and in post-exercise conditions. Oxidative damage markers (malonyldialdehyde, carbonyl and nitrotyrosine indexes) and the activity and protein level of antioxidant enzymes (catalase, superoxide dismutase, glutathione reductase and peroxidase) were assessed. The results showed that training increased antioxidant enzyme activities in erythrocytes. The experimental beverage increased DHA from 34.0 ± 3.6 to 43.0 ± 3.6 nmol/10(9) erythrocytes. DHA supplementation increased the catalytic activity of superoxide dismutase from 1.48 ± 0.40 to 10.5 ± 0.35 pkat/10(9) erythrocytes, and brought about a reduction in peroxidative damage induced by training or exercise. In conclusion, dietary supplementation with DHA changed the erythrocyte membrane composition, provided antioxidant defense and reduced protein peroxidative damage in the red blood cells of professional athletes after an 8-week training season and acute exercise.

Fish and omega-3 fatty acid intake in relation to circulating fibroblast growth factor 23 levels in renal transplant recipients

BACKGROUND AND AIMS

A high circulating fibroblast growth factor 23 (FGF23) level is an independent risk factor for cardiovascular mortality in renal transplant recipients and the general population. N-3 fatty acids eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) may contribute to cardiovascular risk reduction. We investigated whether fish and EPA-DHA intake are related to FGF23 levels in renal transplant recipients.

METHODS AND RESULTS

We performed a cross-sectional analysis in 619 stable renal transplant recipients (mean age 53 years, 57% male, estimated glomerular filtration rate [eGFR] 53 ± 20 mL/min/1.73 m(2)). Dietary intake was assessed by a 177-item food frequency questionnaire. Serum intact FGF23 was measured by ELISA. We examined differences in FGF23 levels across categories of fish and EPA-DHA intake using analysis of variance models adjusted for age, sex, dietary and lifestyle factors and key determinants of FGF23. Patients consumed on average 15 g of fish and 139 mg EPA-DHA/day. Median FGF23 was 62 pg/mL (IQR 43-98 pg/mL). Higher dietary EPA-DHA and fish intake were associated with lower serum FGF23 levels. Subgroup analyses revealed that particularly in patients with reduced renal function (eGFR <60 mL/min/1.73 m(2)), adjusted FGF23 levels (114, 79, 75 pg/mL, P = 0.0001) were inversely associated with tertiles of EPA-DHA intake. Similarly, we observed an inverse association between fish consumption and serum FGF23 levels in adjusted analyses.

CONCLUSION

A higher intake of fish and dietary n-3 fatty acids (EPA-DHA) is related to lower circulating FGF23 levels in renal transplant recipients. Further research is needed to assess the causality of this association and the clinical implications.

5-Lypoxygenase products are involved in renal tubulointerstitial injury induced by albumin overload in proximal tubules in mice

The role of albumin overload in proximal tubules (PT) in the development of tubulointerstitial injury and, consequently, in the progression of renal disease has become more relevant in recent years. Despite the importance of leukotrienes (LTs) in renal disease, little is known about their role in tubulointerstitial injury. The aim of the present work was to investigate the possible role of LTs on tubulointerstitial injury induced by albumin overload. An animal model of tubulointerstitial injury challenged by bovine serum albumin was developed in SV129 mice (wild-type) and 5-lipoxygenase-deficient mice (5-LO^–/–). The changes in glomerular morphology and nestin expression observed in wild-type mice subjected to kidney insult were also observed in 5-LO^–/– mice. The levels of urinary protein observed in the 5-LO^–/– mice subjected or not to kidney insult were lower than those observed in respective wild-type mice. Furthermore, the increase in lactate dehydrogenase activity, a marker of tubule damage, observed in wild-type mice subjected to kidney insult did not occur in 5-LO^–/– mice. LTB₄ and LTD₄, 5-LO products, decreased the uptake of albumin in LLC-PK1 cells, a well-characterized porcine PT cell line. This effect correlated with activation of protein kinase C and inhibition of protein kinase B. The level of proinflammatory cytokines, tumor necrosis factor-α and interleukin (IL)-6, increased in mice subjected to kidney insult but this effect was not modified in 5-LO^–/– mice. However, 5-LO^–/– mice subjected to kidney insult presented lower macrophage infiltration and higher levels of IL-10 than wild-type mice. Our results reveal that LTs have an important role in tubulointerstitial disease induced by albumin overload.

Omega-3 fatty acids inhibit the up-regulation of endothelial chemokines in maintenance hemodialysis patients

BACKGROUND

Chronic systemic inflammation is common in patients with chronic kidney disease on dialysis (CKD5D) and has been considered a key mediator of the increased cardiovascular risk in this patient population. In this study, we tested the hypothesis that supplementation of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) will attenuate the systemic inflammatory process in CKD5D patients.

METHODS

The design was a randomized, double-blinded, placebo controlled pilot trial (NCT00655525). Thirty-eight patients were randomly assigned in a 1 : 1 fashion to receive 2.9 g of eicosapentaenoic acid (C20:5, n-3) plus docosahexaenoic acid (C22:6, n-3) versus placebo for 12 weeks. The primary outcome was change in pro-inflammatory chemokines measured by lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMCs). Secondary outcomes were changes in systemic inflammatory markers. Analysis of covariance was used to compare percent change from baseline to 12 weeks.

RESULTS

Thirty-one patients completed 12 weeks and three patients completed 6 weeks of the study. Median age was 52 (interquartile range 45, 60) years, 74% were African-American and 79% were male. Supplementation of ω-3 PUFAs effectively decreased the LPS-induced PBMC expression of RANTES (Regulated upon Activation, Normal T cell Expressed and Secreted) and MCP-1 (Monocyte Chemotactic Protein-1; unadjusted P = 0.04 and 0.06; adjusted for demographics P = 0.02 and 0.05, respectively). There was no significant effect of the intervention on serum inflammatory markers (C-reactive protein, interleukin-6 and procalcitonin).

CONCLUSIONS

The results of this pilot study suggest that supplementation of ω-3 PUFAs is beneficial in decreasing the levels of endothelial chemokines, RANTES and MCP-1. Studies of larger sample size and longer duration are required to further evaluate effects of ω-3 PUFAs on systemic markers of inflammation, other metabolic parameters and clinical outcomes, particularly cardiovascular outcomes in CKD5D patients.

Interactions between α-tocopherol, polyunsaturated fatty acids, and lipoxygenases during embryogenesis

α-Tocopherol is a lipid-soluble antioxidant that is specifically required for reproduction and embryogenesis. However, since its discovery, α-tocopherol's specific biologic functions, other than as an antioxidant, and the mechanism(s) mediating its requirement for embryogenesis remain unknown. As an antioxidant, α-tocopherol protects polyunsaturated fatty acids (PUFAs) from lipid peroxidation. α-Tocopherol is probably required during embryonic development to protect PUFAs that are crucial to development, specifically arachidonic (ARA) and docosahexaenoic (DHA) acids. Additionally, ARA and DHA are metabolized to bioactive lipid mediators via lipoxygenase enzymes, and α-tocopherol may directly protect, or it may mediate the production and/or actions of, these lipid mediators. In this review, we discuss how α-tocopherol (1) prevents the nonspecific, radical-mediated peroxidation of PUFAs, (2) functions within a greater antioxidant network to modulate the production and/or function of lipid mediators derived from 12- and 12/15-lipoxygenases, and (3) modulates 5-lipoxygenase activity. The application and implication of such interactions are discussed in the context of α-tocopherol requirements during embryogenesis.

Serum oxylipin profiles in IgA nephropathy patients reflect kidney functional alterations

Immunoglobulin A nephropathy (IgAN) is a leading cause of chronic kidney disease, frequently associated with hypertension and renal inflammation. ω-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in fish oil (FO) improve kidney function in animal models, but have inconsistent metabolic effects in humans. Oxylipin profiles in serum from IgAN patients supplemented with either FO or corn oil (CO) placebo were analyzed by liquid chromatography coupled to tandem mass spectrometry. EPA cyclooxygenase and lipoxygenase metabolites, and EPA and DHA epoxides and diols were increased in response to FO supplementation, as were total epoxides and epoxide/diol ratios. Several of these metabolites were drivers of separation as assessed by multivariate analysis of FO patients pre- vs. post-supplementation, including 17,18-dihydroxyeicosatrienoic acid, prostaglandin D₃, prostagalandin E₃, Resolvin E1, 12-hydroxyeicosapentaenoic acid, and 10(11)-epoxydocosapentaenoic acid. In patients whose proteinuria improved, plasma total oxylipins as well as several hydroxyoctadecadienoic acids, hydroxyeicosatetraenoic acids, and leukotriene B₄ metabolites were among the metabolites that were significantly lower than in patients whose proteinuria either did not improve or worsened. These data support the involvement of oxylipins in the inflammatory component of IgAN as well as the potential use of oxylipin profiles as biomarkers and for assessing responsiveness to ω-3 fatty acid supplementation in IgAN patients.

The effect of low-dose marine n-3 fatty acids on the biosynthesis of pro-inflammatory 5-lipoxygenase pathway metabolites in overweight subjects: a randomized controlled trial

INTRODUCTION

Marine n-3 polyunsaturated fatty acids (PUFA) have a variety of anti-inflammatory properties. This study evaluated the effect of n-3 PUFA in a low, but recommended cardioprotective dosage on the formation of 5-lipoxygenase pathway metabolites in overweight subjects.

MATERIALS AND METHODS

Fifty subjects were randomized to 1.1g of n-3 PUFA or olive oil for 6 weeks.

RESULTS

Leukotriene B(4) formation decreased by 14% in the n-3 PUFA group which proved to be significant within the group (p=0.005) but not between groups (p=0.25). The formation of 5-hydroxyeicosatetraenoic acid (5-HETE) did not differ significantly between the groups. In the n-3 PUFA group, both 5-hydroxyeicosapentaenoic (5-HEPE) acid and leukotriene B(5) increased significantly compared to the control group (p<0.001).

CONCLUSION

In conclusion, we did not observe any significant net anti-inflammatory effect on the 5-lipoxygenase pathway from a daily supplement of 1.1g marine n-3 PUFA for 6 weeks.

Presence of glucose in dialyzing fluid and synthesis of selected lipoxygenase-derived eicosanoids during hemodialysis

PURPOSE

Active metabolites of arachidonic acid (AA), eicosanoids, are exerting a significant influence on renal homeostasis. In our recent paper, we demonstrated that high levels of lipoxygenase (LOX)-derived AA metabolites, hydroxyeicosatetraenoic acids (HETEs), unfavorably influence post-transplant function of kidney allografts. Hence, in this study, we wanted (1) to analyze 5-, 12- and 15-HETE levels in non-diabetic chronic kidney disease (CKD) patients, already undergoing regular hemodialysis treatment, and determine factors that may influence these eicosanoids' generation, as well as, (2) to verify whether application of glucose-containing, instead of glucose-free, dialyzing fluids may be beneficial for the limitation of 5-, 12- and 15-HETE synthesis during a single hemodialysis session.

METHODS

Twenty-four healthy individuals and 50 CKD patients undergoing regular hemodialysis treatment were included in the study. CKD patients were divided into two subgroups depending on presence/absence of glucose in dialyzing fluid. LOX-derived HETEs were measured using liquid chromatography.

RESULTS

Results demonstrated higher levels of examined eicosanoids in CKD patients (P<0.05 for all). Older age and higher C-reactive protein levels were associated with HETEs concentrations. Presence of glucose in dialyzing fluid significantly diminished the increase in 5- and 12-HETE synthesis (411.24% vs. 107.29%, P<0.006; 301.70% vs. 98.21%, P<0.0008, respectively), however, it did not influence 15-HETE generation (156.98% vs. 135.24%, P=0.26).

CONCLUSIONS

Non-diabetic CKD patients have higher levels of LOX-derived HETEs, which are associated mainly with age and intensified inflammatory process. The presence of glucose in the dialysate is associated with a reduced synthesis of selected LOX-derived HETEs in these patients; hence, we speculate that the application of such a simple hemodialysis fluid modification may have a favorable influence on post-transplant outcomes.

The effect of n-3 polyunsaturated fatty acids on leukotriene B₄ and leukotriene B₅ production from stimulated neutrophil granulocytes in patients with chronic kidney disease

The proinflammatory leukotriene B₄ (LTB₄) may be of importance in the progression of chronic kidney disease (CKD). We investigated whether n-3 polyunsaturated fatty acids (PUFA) decrease LTB₄ and increase the formation of the less inflammatory leukotriene B₅ (LTB₅) in patients with CKD. Fifty-six patients with CKD stage 2-5 were randomised to 2.4 g n-3 PUFA or olive oil for 8 weeks. Compared to controls, n-3 PUFA significantly decreased release of LTB₄ (p<0.001) and 5-hydroxyeicosatetraenoic acid (5-HETE) (p<0.01) and significantly increased release of LTB₅ (p<0.001) and 5-hydroxyeicosapentaenoic acid (5-HEPE) (p<0.001) from stimulated neutrophil granulocytes. Kidney function evaluated by creatinine clearance and proteinuria did not improve. In conclusion, n-3 PUFA supplementation for 8 weeks in patients with CKD stage 2-5 significantly decreased LTB₄ and 5-HETE and significantly increased LTB₅ and 5-HEPE. No effect was seen on kidney function.

Protective effect of docosahexaenoic acid against cyclosporine A-induced nephrotoxicity in rats: a possible mechanism of action

The aim of this experimental study was to investigate whether, and how then, docosahexaenoic acid (DHA) could alleviate the cyclosporine A (CsA)-induced nephrotoxicity. Three main groups of Sprague-Dawley rats were treated orally with CsA (25 mg/kg), DHA (100 mg/kg), and CsA along with DHA. A corresponding control group was also used. DHA administration significantly reduced CsA-induced nephrotoxicity and associated hyperlipidemia and proteinuria as assessed by estimating serum triacylglycerol, serum total cholesterol, serum total protein, serum urea, and creatinine clearance. Furthermore, urinary excretions of protein and N-acetyl-β-D-glucosaminidase were significantly inhibited following DHA administration. DHA supplementation slightly attenuated the oxidative damage in kidney tissues as evaluated by the levels of thiobarbituric acid-reacting substances and protein carbonyl content in the kidney homogenate, although there were no significant differences between CsA-intoxicated and DHA-treated animals. Moreover, DHA treatment significantly restored total nitric oxide (NO) levels in both renal tissues and urine. This study demonstrates the ability of DHA to ameliorate CsA-induced renal dysfunction, which might be beneficial to enhance the therapeutic index of CsA. The data suggest that the protective potential of DHA in the prevention of CsA nephrotoxicity in rats was mainly associated with the increase of total NO bioavailability in renal tissues. Nevertheless, the exact independent mechanism in which DHA exerts its beneficial effect is yet to be fully elucidated.

Chronic treatment with statins increases the availability of selenium in the antioxidant defence systems of hemodialysis patients

PROJECT

Oxidative stress (OS) is enhanced in hemodialysis (HD) patients. Lipid peroxidation and oxidative damage to glycids, proteins and nucleic acids are the main consequences of OS and are associated with increased cardiovascular risk. Vitamin E and glutathione peroxidase (GSH-Px) represent the main antioxidant systems in human cells. Selenium (Se), bound to the active sites of GSH-Pxs, plays a critical role in this antioxidant defence system. Statins are widely used and extensively investigated in the prevention of cardiovascular disease, notably in high-risk subjects. Several studies show antioxidant effects of statins not related to their lipid-lowering action. Our study aimed to compare serum Se concentration in ESRD patients on maintenance HD and in homogeneous healthy subjects and to investigate whether chronic treatment with statins may interfere with serum Se concentration in HD patients.

PROCEDURE

A total of 103 HD patients and 69 healthy subjects were enrolled; HD patients were divided into patients who were not treated with statins (group A) and patients who assumed statins since 6 months at least (group B). Serum Se was determined by atomic absorption spectrometry.

RESULTS

Serum Se was significantly lower in HD patients of group A compared with healthy subjects (81.65+/-19.66 Vs. 96.47+/-15.62 mcg/L, p<0.0040). However, in HD patients who assumed statins serum, Se was significantly higher than in HD patients who did not (111.83+/-18.82 vs. 81.65+/-19.66 mcg/L, p<0.0001).

CONCLUSIONS

Our results suggest that in HD patients chronic treatment with statins is related to higher-serum Se concentration.

Antiatherogenic effects of vitamin E: the search for the Holy Grail

Vitamin E, a naturally occurring antioxidant, has been found to reduce atherosclerotic lesion formation in animal models as well as cardiovascular morbidity in several observational studies. However, a number of case-control and prospective cohort studies failed to confirm its value in the primary and secondary prevention of morbidity and mortality from coronary artery disease. Several small or larger randomized interventional trials completed to date failed to resolve the conflict. Notably, even in large, well-conducted prospective epidemiologic studies, the potential effects of residual confounding may be on the same order of magnitude as the reported benefit. The response to vitamin E supplementation in specific patient subpopulations with chronic inflammation and/or higher degrees of oxidative stress has not been studied as yet. Therefore, further large randomized interventional trials are warranted to clarify accurately the role of vitamin E in the primary and secondary prevention of atherosclerotic coronary disease in these patient groups.

Inhibition of arachidonic acid metabolism and its implication on cell proliferation and tumour-angiogenesis

Arachidonic acid (AA) and its metabolites have recently generated a heightened interest due to growing evidence of their significant role in cancer biology. Thus, inhibitors of the AA cascade, first and foremost COX inhibitors, which have originally been of interest in the treatment of inflammatory conditions and certain types of cardiovascular disease, are now attracting attention as an arsenal against cancer. An increasing number of investigations support their role in cancer chemoprevention, although the precise molecular mechanisms that link levels of AA, and its metabolites, with cancer progression have still to be elucidated. This article provides an overview of the AA cascade and focuses on the roles of its inhibitors and their implication in cancer treatment. In particular, emphasis is placed on the inhibition of cell proliferation and neo-angiogenesis through inhibition of the enzymes COX-2, 5-LOX and CYP450. Downstream effects of inhibition of AA metabolites are analysed and the molecular mechanisms of action of a selected number of inhibitors of catalytic pathways reviewed. Lastly, the benefits of dietary omega-3 fatty acids and their mechanisms of action leading to reduced cancer risk and impeded cancer cell growth are mentioned. Finally, a proposal is put forward, suggesting a novel and integrated approach in viewing the molecular mechanisms and complex interactions responsible for the involvement of AA metabolites in carcinogenesis and the protective effects of omega-3 fatty acids in inflammation and tumour prevention.

5-Lipoxygenase in the Prefrontal Cortex of Suicide Victims

5-lipoxygenase (5-LOX), an enzyme involved in leukotriene synthesis, is expressed in the brain and has been associated with Alzheimer's disease and depression. Recently, it has been suspected that leukotriene receptor antagonists might be associated with suicide. In this work, we investigated the 5-LOX protein in the brain samples from depressed suicide victims and matching controls. We used Western immunoblotting with an antibody against Ser(523)-phosphorylated 5-LOX (p5-LOX) to evaluate protein kinase A-mediated 5-LOX phosphorylation, and in addition, an antibody against the total 5-LOX protein. In the total homogenate of the prefrontal cortex samples, 5-LOX content did not differ in the control and suicide groups but p5-LOX was significantly elevated in the suicide samples. The 5-LOX protein content was reduced in the membrane fraction and increased in the cytosol fraction of suicide victims. We propose that further studies of brain 5-LOX are needed to elucidate the functional implications of the protein alterations observed in our present study, and to further explore a putative role of 5-LOX in depression and suicide.

Effects of N-3 PUFAs supplementation on insulin resistance and inflammatory biomarkers in hemodialysis patients

AIMS/HYPOTHESIS

It was suggested that polyunsaturated n-3 fatty acids (n-3 PUFAs) could improve insulin sensitivity and have an anti-inflammatory effects in overall population. This study investigates a possible effect of n-3 PUFAs supplementation on the insulin sensitivity and some inflammatory markers; hence, patients with chronic renal failure (CRF) on maintenance hemodialysis (MHD) are presented with insulin resistance.

METHODS

This study explored the ratio between red blood cells (RBC) phospholipid long chain fatty acids (LC FAs) and components of metabolic syndrome (MeS) in 35 patients (mean age 54.50 +/- 11.99 years) with CRF on MHD. Furthermore, the effects of omega-3 FA eight-week's supplementation (EPA+DHA, 2.4 g/d) on the MeS features and inflammatory markers TNF-alpha, IL 6, and hsCRP were examined.

RESULTS

Supplementation increased EPA and DHA levels in RBCs (p = 0.009 for EPA and p = 0.002 for DHA). Total n-6 PUFAs: n-3 PUFAs ratio tended to be lower after supplementation (p = 0.31), but not significantly. Data revealed a significant decrease of saturated FAs (SFA) (p = 0.01) as well as total SFA: n-3 PUFAs ratio during the treatment (p = 0.04). The values of serum insulin and calculated IR index-IR HOMA were reduced after supplementation (p = 0.001 for both). There was a significant decrease in the levels of all inflammatory markers (p = 0.01 for TNF alpha, p = 0.001 for IL 6, p = 0.001 for hsCRP, and p = 0.01 for ferritin). In multivariate regression analysis, only the changes in n-6 PUFAs: n-3 PUFAs ratio independently contributed to 40% of the variance in IR HOMA. The impact of changes in PUFAs level in RBCs membrane phospholipid fatty acids on inflammation markers was also registered. The changes in n-6: n-3 PUFAs ratio independently contributed to 18% of the variance in TNF alpha.

CONCLUSION

It was concluded that the EPA and DHA moderate dose administration in the patients with CRF on MHD had a beneficial effect on insulin resistance decrease. The anti-inflammatory effects of the supplemented PUFAs were also presented.