The effects of EPA, DHA, and aspirin ingestion on plasma lysophospholipids and autotaxin

Phospholipid-derived lysophospholipids in (patho)physiology

Phospholipids (PL) are major components of cellular membranes and changes in PL metabolism have been associated with the pathogenesis of numerous diseases. Lysophosphatidylcholine (LPC) in particular, is a comparably abundant component of oxidatively damaged tissues. LPC originates from the cleavage of phosphatidylcholine (PC) by phospholipase A2 or the reaction of lipids with reactive oxygen species (ROS) such as HOCl. Another explanation of increased LPC concentration is the decreased re-acylation of LPC into PC. While there are also several other lysophospholipids, LPC is the most abundant lysophospholipid in mammals and will therefore be the focus of this review. LPC is involved in many physiological processes. It induces the migration of lymphocytes, fostering the production of pro-inflammatory compounds by inducing oxidative stress. LPC also "signals" via G protein-coupled and Toll-like receptors and has been implicated in the development of different diseases. However, LPCs are not purely "bad": this is reflected by the fact that the concentration and fatty acyl composition of LPC varies under different conditions, in plasma of healthy and diseased individuals, in tissues and different tumors. Targeting LPC and lipid metabolism and restoring homeostasis might be a potential therapeutic method for inflammation-related diseases.

A dual role of lysophosphatidic acid type 2 receptor (LPAR2) in nonsteroidal anti-inflammatory drug-induced mouse enteropathy

Lysophosphatidic acid (LPA) is a bioactive phospholipid mediator that has been found to ameliorate nonsteroidal anti-inflammatory drug (NSAID)-induced gastric injury by acting on lysophosphatidic acid type 2 receptor (LPAR2). In this study, we investigated whether LPAR2 signaling was implicated in the development of NSAID-induced small intestinal injury (enteropathy), another major complication of NSAID use. Wild-type (WT) and Lpar2 deficient (Lpar2-/-) mice were treated with a single, large dose (20 or 30 mg/kg, i.g.) of indomethacin (IND). The mice were euthanized at 6 or 24 h after IND treatment. We showed that IND-induced mucosal enteropathy and neutrophil recruitment occurred much earlier (at 6 h after IND treatment) in Lpar2-/- mice compared to WT mice, but the tissue levels of inflammatory mediators (IL-1β, TNF-α, inducible COX-2, CAMP) remained at much lower levels. Administration of a selective LPAR2 agonist DBIBB (1, 10 mg/kg, i.g., twice at 24 h and 30 min before IND treatment) dose-dependently reduced mucosal injury and neutrophil activation in enteropathy, but it also enhanced IND-induced elevation of several proinflammatory chemokines and cytokines. By assessing caspase-3 activation, we found significantly increased intestinal apoptosis in IND-treated Lpar2-/- mice, but it was attenuated after DBIBB administration, especially in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Finally, we showed that IND treatment reduced the plasma activity and expression of autotaxin (ATX), the main LPA-producing enzyme, and also reduced the intestinal expression of Lpar2 mRNA, which preceded the development of mucosal damage. We conclude that LPAR2 has a dual role in NSAID enteropathy, as it contributes to the maintenance of mucosal integrity after NSAID exposure, but also orchestrates the inflammatory responses associated with ulceration. Our study suggests that IND-induced inhibition of the ATX-LPAR2 axis is an early event in the pathogenesis of enteropathy.

Non-targeted LC-MS/MS metabolomic profiling of human plasma uncovers a novel Mediterranean diet biomarker panel

INTRODUCTION

Consumption of a Mediterranean diet (MD) has established health benefits, and the identification of novel biomarkers could enable objective monitoring of dietary pattern adherence.

OBJECTIVES

The present investigation performed untargeted metabolomics on blood plasma from a controlled study of MD adherence, to identify novel blood-based metabolite biomarkers associated with the MD pattern, and to build a logistic regression model that could be used to characterise MD adherence.

METHODS

A hundred and thirty-five plasma samples from n = 58 patients collected at different time points were available. Using a 14-point scale MD Score (MDS) subjects were divided into 'high' or 'low' MDS adherence groups and liquid chromatography-mass spectrometry (LC-MS/MS) was applied for analysis.

RESULTS

The strongest association with MDS was pectenotoxin 2 seco acid (r = 0.53; ROC = 0.78), a non-toxic marine xenobiotic metabolite. Several lipids were useful biomarkers including eicosapentaenoic acid, the structurally related lysophospholipid (20:5(5Z,8Z,11Z,14Z,17Z)/0:0), a phosphatidylcholine (P-18:1(9Z)/16:0) and also xi-8-hydroxyhexadecanedioic acid. Two metabolites negatively correlated with MDS, these were the monoacylglycerides (0:0/16:1(9Z)/0:0) and (0:0/20:3(5Z,8Z,11Z)/0:0). By stepwise elimination we selected a panel of 3 highly discriminatory metabolites and developed a linear regression model which identified 'high MDS' individuals with high sensitivity and specificity [AUC (95% CI) 0.83 (0.76-0.97)].

CONCLUSION

Our study highlights the utility of metabolomics as an approach for developing novel panels of dietary biomarkers. Quantitative profiling of these metabolites is required to validate their utility for evaluating dietary adherence.

Effects of Nutrition Education Program for the Japan Diet on Serum Phospholipid Fatty Acid Compositions in Patients with Dyslipidemia: Re-analysis of Data from a Previous Randomized Controlled Trial

AIM

We investigated changes in serum phospholipid fatty acid compositions with intake of the Japan Diet (JD) (higher consumption of fish, soybeans, vegetables, seaweed/mushrooms/konjak, and unrefined cereals with reduced consumption of animal fat, meat and poultry with fat, sweets and alcoholic drinks) recommended by the Japan Atherosclerosis Society.

METHODS

A randomized parallel controlled clinical trial on JD intake was conducted on Japanese patients with dyslipidemia. Nutrition education, based on the JD or partial JD (PJD) at baseline and at 3 months, was provided and the participants were followed up for 6 months. Fatty acids comprising serum phospholipids were measured in the JD (n=44) and PJD (n=44) groups.

RESULTS

Fatty acid intakes of C20:4, C20:5 and C22:6 increased in the JD group as compared with the PJD group. The percentages of serum phospholipid, C22:1 and C20:5 increased, while those of C18:1, C20:3(n-6) and C20:4(n-6) decreased in the JD as compared with the PJD group at 3 months. Changes in the phospholipid concentrations of C20:5, C22:5 and C22:6 reflected those intake volumes. Serum phospholipid C20:5 and C22:6 showed inverse correlations with C18:1, C18:2, and C20:3(n-6) at baseline and the changes at 3 and 6 months. In contrast, no correlation was observed between C20:4(n-6) and those n-3 fatty acids. The ratios of fatty acid concentrations, C16:1/C16:0 and C18:1/C18:0, decreased, but the ratio of C20:4(n-6)/C20:3(n-6) increased in the JD group.

CONCLUSION

Nutrition education on the JD changed serum phospholipid fatty acid profiles in favor to prevent against cardiovascular risk factors in patients with dyslipidemia.

Comparative analysis of the synergetic effects of Diwuyanggan prescription on high fat diet-induced non-alcoholic fatty liver disease using untargeted metabolomics

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver disorders worldwide and had no approved pharmacological treatments. Diwuyanggan prescription (DWYG) is a traditional Chinese medicine preparation composed of 5 kinds of herbs, which has been used for treating chronic liver diseases in clinic. Whereas, the synergistic mechanism of this prescription for anti-NAFLD remains unclear. In this study, we aimed to demonstrate the synergetic effect of DWYG by using the disassembled prescriptions and untargeted metabolomics research strategies. The therapeutic effects of the whole prescription of DWYG and the individual herb were divided into six groups according to the strategy of disassembled prescriptions, including DWYG, Artemisia capillaris Thunb. (AC), Curcuma longa L. (CL), Schisandra chinensis Baill. (SC), Rehmannia glutinosa Libosch. (RG) and Glycyrrhiza uralensis Fisch. (GU) groups. The high fat diets-induced NAFLD mice model was constructed to evaluate the efficacy effects of DWYG. An untargeted metabolomics based on the UPLC-QTOF-MS/MS approach was carried out to make clear the synergetic effect on the regulation of metabolites dissecting the united mechanisms. Experimental results on animals revealed that the anti-NAFLD effect of DWYG prescription was better than the individual herb group in reducing liver lipid deposition and restoring the abnormality of lipidemia. In addition, further metabolomics analysis indicated that 23 differential metabolites associated with the progression of NAFLD were identified and 19 of them could be improved by DWYG. Compared with five single herbs, DWYG showed the most extensive regulatory effects on metabolites and their related pathways, which were related to lipid and amino acid metabolisms. Besides, each individual herb in DWYG was found to show different degrees of regulatory effects on NAFLD and metabolic pathways. SC and CL possessed the highest relationship in the regulation of NAFLD. Altogether, these results provided an insight into the synergetic mechanisms of DWYG from the metabolic perspective, and also supported a scientific basis for the rationality of clinical use of this prescription.

Oral Administration of Egg- and Soy-Derived Lysophosphatidylcholine Mitigated Acetylcholine Depletion in the Brain of Scopolamine-Treated Rats

Enzyme-modified lecithin that contains lysophosphatidylcholine (LPC) is generally recognized as safe. However, its potential as a functional ingredient has been less investigated than other choline (Ch)-containing compounds, such as glycerophosphocholine (GPC). Reports on the possibility of LPC functioning as a cholinergic precursor in vivo and on its kinetics are limited to docosahexaenoic acid-bound LPC. Herein, three experiments were performed to investigate these processes in scopolamine (SCO)-treated rats. First, an egg-derived LPC reagent was orally administered to rats, and brain acetylcholine (ACh), Ch, plasma Ch, and LPC were measured. Second, soy- and rapeseed-derived enzyme-modified lecithins and GPC were administered for comparison. Third, soy-derived enzyme-modified lecithins with different fat contents were administered for comparison. The LPC reagent mitigated SCO-induced ACh depletion at 500 mg/kg body weight and increased plasma Ch, but not LPC, concentrations. Additionally, soy-derived LPC-containing food additive counteracted brain ACh depletion similarly to GPC. Interestingly, plasma Ch and linoleoyl-LPC levels were higher when soy-derived LPC with a higher fat content was administered, whereas the plasma levels of palmitoyl-LPC decreased and those of total LPC remained constant. In conclusion, egg- and soy-derived LPC species function as cholinergic precursors in vivo, and future studies should explore this potential.

Longitudinal associations between blood lysophosphatidylcholines and skeletal muscle mitochondrial function

Lysophosphatidylcholines (LPCs) are phospholipids critical in the synthesis of cardiolipin, an essential component of mitochondrial membranes. Lower plasma LPCs have been cross-sectionally associated with lower skeletal muscle mitochondrial function, but whether lower LPCs and their decline over time are longitudinally associated with an accelerated decline of mitochondria function is unknown. We analyzed data from 184 participants in the Baltimore Longitudinal Study of Aging (mean age: 74.5 years, 57% women, 25% black) who had repeated measures of plasma LPCs (16:0, 16:1, 17:0, 18:0, 18:1, 18:2, 20:3, 20:4, 24:0, and 28:1) by liquid chromatography-tandem mass spectrometry and repeated measures of skeletal muscle oxidative capacity (k_PCr) assessed by ³¹P magnetic resonance spectroscopy over an average of 2.4 years. Rates of change in k_PCr and each LPC were first estimated using simple linear regression. In multivariable linear regression models adjusted for baseline demographics and PCr % depletion, lower baseline LPC 16:1 and faster rates of decline in LPC 16:1 and 18:1 were significantly associated with a faster rate of decline in k_PCr (B =  - 0.169, 95% CI: - 0.328, - 0.010, p = 0.038; B = 0.209, 95% CI: 0.065, 0.352, p = 0.005; B = 0.156, 95% CI: 0.011, 0.301, p = 0.035, respectively). Rates of change in other LPCs were not significantly associated with change in k_PCr (all p > 0.05). Lower baseline concentrations and faster decline in selected plasma lysophosphatidylcholines over time are associated with faster decline in skeletal muscle mitochondrial function. Strategies to prevent the decline of plasma LPCs at an early stage may slow down mitochondrial function decline and impairment during aging.

Aspirin and omega-3 polyunsaturated fatty acid use and their interaction in cardiovascular diseases and colorectal adenomas

Aspirin (acetylsalicylic acid, ASA) is inexpensive and is established in preventing cardiovascular disease (CVD) and colorectal adenomas. Omega-3 (n3) polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have also shown benefit in preventing CVD. The combination could be an effective preventative measure in patients with such diseases. ASA and n3 PUFA reduced the risk of CVD in ASA-resistant or diabetic patients. EPA- and DHA-deficient patients also benefited the most from n3 PUFA supplementation. Synergistic effects between ASA and EPA and DHA are 'V-shaped' such that optimal ASA efficacy is dependent on EPA and DHA concentrations in blood. In colorectal adenomas, ASA (300 mg/d) and EPA reduced adenoma burden in a location- and subtype-specific manner. Low doses of ASA (75-100 mg/d) were used in CVD prevention; however, ultra-low doses (30 mg/d) can also reduce thrombosis. EPA-to-DHA ratio is also important with regard to efficacy. DHA is more effective in reducing blood pressure and modulating systemic inflammation; however, high-dose EPA can lower CVD events in high-risk individuals. Although current literature has yet to examine ASA and DHA in preventing CVD, such combination warrants further investigation. To increase adherence to ASA and n3 PUFA supplementation, combination dosage form may be required to improve outcomes.

Associations between plasma lysophospholipids concentrations, chronic kidney disease and the type of renal replacement therapy

BACKGROUND

Lysophosphatidic acid (LPA) and lysophosphatidylcholine (LPC) are bioactive lysophospholipids involved in the pathogenesis of renal diseases, especially the renal fibrosis. Plasma LPC concentrations in chronic kidney disease (CKD) patients are lower or similar to those observed in control groups, but less is known about the LPA concentrations. The main aim of the study was the analysis of associations of chronic kidney disease and renal replacement therapy with the plasma LPA concentrations. We have also analyzed the relationship between the plasma concentrations of LPA and LPC.

MATERIAL AND METHODS

Study group consisted of 110 patients with CKD in stages G3-G5 according to the KDIGO guidelines and was divided into four subgroups: treated conservatively (CT, 30 patients), on hemodialysis (HD, 30 patients), on peritoneal dialysis (PD, 30 patients) and renal transplant recipients (RT, 20 patients). In HD the blood was collected immediately before (HD D1) and after the dialysis (HD D2). In RT the blood was collected immediately before (RT D1) and 3-14 days after the transplantation (RT D2). The control group (Con) consisted of 50 healthy volunteers. Plasma concentrations of LPA and LPC were measured using enzyme-linked immunosorbent assays.

RESULTS

In CT, PD and RT D2 plasma concentrations of LPA were significantly higher, compared to Con. In HD, LPA levels did not differ compared to Con and they were significantly lower compared to PD (HD D1 and HD D2), RT D2 (HD D1 and HD D2) and CT (HD D1). However, in most of patients concentrations of LPA were within the range of reference values established in healthy volunteers. Concentrations of LPC were significantly lower in almost all patients subgroups, compared to Con, except in PD. There were no significant correlations between plasma concentrations of LPA and LPC in any of patients subgroups.

CONCLUSIONS

Presence of CKD is associated with increased plasma LPA levels and the hemodialysis therapy reduces this influence. However, only in a small percentage of patients with CKD, LPA concentrations are out of the reference range, which makes LPA not useful as a diagnostic marker for CKD. Further studies are needed to confirm and explain observed relationships.

Lipidomic Profiling of Plasma and Erythrocytes From Septic Patients Reveals Potential Biomarker Candidates

Background

Sepsis remains the primary cause of death from infection, despite advances in modern medicine. The identification of reliable diagnostic biomarkers for the early detection of this disease is critical and may reduce the mortality rate as it could allow early treatment. The purpose of this study was to describe the changes in the plasma and red cells blood lipidome profiling of patients diagnosed with sepsis and septic shock with the aim to identify potentially useful metabolic markers.

Methods

Lipids from plasma and erythrocytes from septic patients (n = 20) and healthy controls (n = 20) were evaluated by electrospray ionization quadrupole time-of-flight mass spectrometry, and the fatty acid composition of the phospholipids fraction of erythrocytes was determined by gas chromatography. The data were treated with multivariate data analysis, including principal component analysis and (orthogonal) partial least squares discriminant analysis.

Results

Potential biomarkers including lysophosphatidylcholines (lyso-PCs) and sphingomyelin (SMs) with specific fatty acid chains were identified. Both Lyso-PCs and SMs were downregulated, whereas the saturated and unsaturated phosphatidylcholines (PCs) were upregulated in the plasma and erythrocytes of septic patients. An increase in oleic acid (C18:1 n-9) accompanied by a decrease in the unsaturation index as well as in the levels on n-3 polyunsaturated fatty acids was observed in erythrocytes phospholipids patients as compared with healthy controls.

Conclusions

These results suggest that lipidome profiling has great potential in discovering potential clinical biomarkers for sepsis and helping to understand its underlying mechanisms.

Brain docosahexaenoic acid uptake and metabolism

Docosahexaenoic acid (DHA) is the most abundant n-3 polyunsaturated fatty acid in the brain where it serves to regulate several important processes and, in addition, serves as a precursor to bioactive mediators. Given that the capacity of the brain to synthesize DHA locally is appreciably low, the uptake of DHA from circulating lipid pools is essential to maintaining homeostatic levels. Although, several plasma pools have been proposed to supply the brain with DHA, recent evidence suggests non-esterified-DHA and lysophosphatidylcholine-DHA are the primary sources. The uptake of DHA into the brain appears to be regulated by a number of complementary pathways associated with the activation and metabolism of DHA, and may provide mechanisms for enrichment of DHA within the brain. Following entry into the brain, DHA is esterified into and recycled amongst membrane phospholipids contributing the distribution of DHA in brain phospholipids. During neurotransmission and following brain injury, DHA is released from membrane phospholipids and converted to bioactive mediators which regulate signaling pathways important to synaptogenesis, cell survival, and neuroinflammation, and may be relevant to treating neurological diseases. In the present review, we provide a comprehensive overview of brain DHA metabolism, encompassing many of the pathways and key enzymatic regulators governing brain DHA uptake and metabolism. In addition, we focus on the release of non-esterified DHA and subsequent production of bioactive mediators and the evidence of their proposed activity within the brain. We also provide a brief review of the evidence from post-mortem brain analyses investigating DHA levels in the context of neurological disease and mood disorder, highlighting the current disparities within the field.

Abnormal lipoprotein oxylipins in metabolic syndrome and partial correction by omega-3 fatty acids

Metabolic syndrome (MetSyn) is characterized by chronic inflammation which mediates the associated high risk for cardiovascular and other diseases. Oxylipins are a superclass of lipid mediators with potent bioactivities in inflammation, vascular biology, and more. While their role as locally produced agents is appreciated, most oxylipins in plasma are found in lipoproteins suggesting defective regulation of inflammation could be mediated by the elevated VLDL and low HDL levels characteristic of MetSyn. Our objective was to compare the oxylipin composition of VLDL, LDL, and HDL in 14 optimally healthy individuals and 31 MetSyn patients, and then to determine the effects of treating MetSyn subjects with 4g/day of prescription omega-3 fatty acids (P-OM3) on lipoprotein oxylipin profiles. We compared oxylipin compositions of healthy (14) and MetSyn (31) subjects followed by randomization and assignment to 4g/d P-OM3 for 16 weeks using LC/MS/MS. Compared to healthy subjects, MetSyn is characterized by abnormalities of (1) pro-inflammatory, arachidonate-derived oxylipins from the lipoxygenase pathway in HDL; and (2) oxylipins mostly not derived from arachidonate in VLDL. P-OM3 treatment corrected many components of these abnormalities, reducing the burden of inflammatory mediators within peripherally circulating lipoproteins that could interfere with, or enhance, local effectors of inflammatory stress. We conclude that MetSyn is associated with a disruption of lipoprotein oxylipin patterns consistent with greater inflammatory stress, and the partial correction of these dysoxylipinemias by treatment with omega-3 fatty acids could explain some of their beneficial effects.

Fatty acyl composition of lysophosphatidylcholine is important in atherosclerosis

Atherosclerosis is a major cause of death for mankind. Although the pathophysiology of atherosclerosis is a complex and multifactorial process, growing body of evidence has identified phospholipids-mediated signaling as an important factor in the induction and progression of atherosclerosis. Lysophosphatidylcholine (LPC) is a major phospholipid in oxidized low-density lipoprotein, and is generally considered to be atherogenic. However, some studies have shown anti-atherogenic properties of LPC. The controversial findings surrounding the pro- or anti-atherogenic properties of LPC appear to be due to the chain length and the degree of saturation of the fatty acyl moiety of LPC. Studies have suggested that the presence of omega (n)-polyunsaturated fatty acids (PUFA) at the sn-1 position of LPC modulates the inflammatory response thereby making LPC anti-atherogenic. We have recently shown that feeding a diet high in n-3 PUFA resulted in the enrichment of LPC in both plasma and liver of C57BL/6 mice with n-3 PUFA. Others have also shown that supplementation with fish oil leads to preferential incorporation of n-3 PUFA into LPC. We also found that plasma obtained from mice fed a diet high in n-3 PUFA showed higher cholesterol efflux capacity compared to animals fed a low n-3 PUFA diet, despite no changes in high-density lipoprotein concentrations. We are therefore hypothesizing that n-3 PUFA enriched LPC has anti-atherogenic properties by promoting cholesterol efflux from macrophages and by reducing inflammation. Our anticipated long term objective is to establish that the fatty acyl moiety of LPC can be used as a potential biomarker for the risk of developing atherosclerosis. Validating this hypothesis would have a substantial impact on the public health with respect to early diagnosis of cardiovascular risks, and designing dietary based therapeutic strategies for the prevention and management of atherosclerosis and other heart related diseases.

Comparison of serum concentrations of symmetric dimethylarginine and creatinine as kidney function biomarkers in healthy geriatric cats fed reduced protein foods enriched with fish oil, L-carnitine, and medium-chain triglycerides

The purpose of this study was to determine whether feeding cats reduced protein and phosphorus foods with added fish oil, L-carnitine, and medium-chain triglycerides (MCT) altered serum biomarkers of renal function. Thirty-two healthy cats, mean age 14.0 (8.3-19.6) years, were fed control food or one of two experimental foods for 6 months. All foods had similar concentrations of moisture, protein, and fat (approximately 8.0%, 26.5%, and 20.0%, respectively). Both experimental foods contained added fish oil (1.5%) and L-carnitine (500 mg/kg). Experimental-food 2 also contained increased MCT (10.5% from coconut oil), 1.5% added corn oil, and reduced animal fat. Glomerular filtration rate (GFR), serum biochemistries, renal function biomarkers including serum creatinine (sCr) and symmetrical dimethylarginine (SDMA), and plasma metabolomic profiles were measured at baseline, and at 1.5, 3, and 6 months. Body composition was determined by dual-energy X-ray absorptiometry. Although both experimental foods altered plasma fatty acids, carnitine and related metabolites, and lysophospholipid concentrations, there were no changes in renal function biomarkers. There was, however, a benefit in using SDMA versus sCr to assess renal function in older cats with less total lean mass. Compared with cats <12 years, those >15 years had lower total lean mass (P < 0.01), lower GFR (P = 0.04), and lower sCr concentrations (P < 0.01). However, SDMA concentrations (P < 0.01) were higher in older cats. This study shows that in cats, serum SDMA concentration is more highly correlated with GFR than sCr concentration, and, unlike sCr, which declines with age because of muscle wasting, SDMA increases as GFR declines with age.

A protective lipidomic biosignature associated with a balanced omega-6/omega-3 ratio in fat-1 transgenic mice

A balanced omega-6/omega-3 polyunsaturated fatty acid (PUFA) ratio has been linked to health benefits and the prevention of many chronic diseases. Current dietary intervention studies with different sources of omega-3 fatty acids (omega-3) lack appropriate control diets and carry many other confounding factors derived from genetic and environmental variability. In our study, we used the fat-1 transgenic mouse model as a proxy for long-term omega-3 supplementation to determine, in a well-controlled manner, the molecular phenotype associated with a balanced omega-6/omega-3 ratio. The fat-1 mouse can convert omega-6 to omega-3 PUFAs, which protect against a wide variety of diseases including chronic inflammatory diseases and cancer. Both wild-type (WT) and fat-1 mice were subjected to an identical diet containing 10% corn oil, which has a high omega-6 content similar to that of the Western diet, for a six-month duration. We used a multi-platform lipidomic approach to compare the plasma lipidome between fat-1 and WT mice. In fat-1 mice, an unbiased profiling showed a significant increase in the levels of unesterified eicosapentaenoic acid (EPA), EPA-containing cholesteryl ester, and omega-3 lysophosphospholipids. The increase in omega-3 lipids is accompanied by a significant reduction in omega-6 unesterified docosapentaenoic acid (omega-6 DPA) and DPA-containing cholesteryl ester as well as omega-6 phospholipids and triacylglycerides. Targeted lipidomics profiling highlighted a remarkable increase in EPA-derived diols and epoxides formed via the cytochrome P450 (CYP450) pathway in the plasma of fat-1 mice compared with WT mice. Integration of the results of untargeted and targeted analyses has identified a lipidomic biosignature that may underlie the healthful phenotype associated with a balanced omega-6/omega-3 ratio, and can potentially be used as a circulating biomarker for monitoring the health status and the efficacy of omega-3 intervention in humans.

The autotaxin-LPA axis emerges as a novel regulator of lymphocyte homing and inflammation

Lysophosphatidic acid (LPA) is a pleiotropic lipid molecule with potent effects on cell growth and motility. Major progress has been made in recent years in deciphering the mechanisms of LPA generation and how it acts on target cells. Most research has been conducted in other disciplines, but emerging data indicate that LPA has an important role to play in immunity. A key discovery was that autotaxin (ATX), an enzyme previously implicated in cancer cell motility, generates extracellular LPA from the precursor lysophosphatidylcholine. Steady-state ATX is expressed by only a few tissues, including high endothelial venules in lymph nodes, but inflammatory signals can upregulate ATX expression in different tissues. In this article, we review current thinking about the ATX/LPA axis in lymphocyte homing, as well as in models of allergic airway inflammation and asthma. New insights into the role of LPA in regulating immune responses should be forthcoming in the near future.

The effects of aspirin and fish oil consumption on lysophosphatidylcholines and lysophosphatidic acids and their correlates with platelet aggregation in adults with diabetes mellitus

Many diabetics are insensitive to aspirin's platelet anti-aggregation effects. The influence of co-administration of aspirin and fish oil (FO) on plasma lysophospholipids in subjects with diabetes is poorly characterized. Thirty adults with type 2 diabetes mellitus were treated with aspirin (81mg/day) for seven days, then with FO (4g/day) for 28 days, then in combination for another seven days. Lysophospholipids and platelet measures were determined after acute (4h) and chronic (7 days) ingestion of aspirin, FO, or both in combination. FO ingestion reduced all lysophosphatidic acid (LPA) concentrations, while EPA (20:5n-3) and DHA (22:6n-3) lysophosphatidylcholine (LPC) concentrations significantly increased after FO alone and in combination with aspirin. In vitro arachidonic acid-induced platelet aggregation was most strongly correlated with palmitoleic (16:1) and oleic (18:1) LPA and LPC concentrations at all time points. The ingestion of these agents may reduce cardiovascular disease risk in diabetic adults, with a disrupted lipid milieu, via lysolipid mediated mechanisms.

Dietary omega-3 polyunsaturated fatty acids alter the fatty acid composition of hepatic and plasma bioactive lipids in C57BL/6 mice: a lipidomic approach

Background

Omega (n)-3 polyunsaturated fatty acids (PUFA) are converted to bioactive lipid components that are important mediators in metabolic and physiological pathways; however, which bioactive compounds are metabolically active, and their mechanisms of action are still not clear. We investigated using lipidomic techniques, the effects of diets high in n-3 PUFA on the fatty acid composition of various bioactive lipids in plasma and liver.

Methodology and Principal Findings

Female C57BL/6 mice were fed semi-purified diets (20% w/w fat) containing varying amounts of n-3 PUFA before mating, during gestation and lactation, and until weaning. Male offspring were continued on their mothers’ diets for 16 weeks. Hepatic and plasma lipids were extracted in the presence of non-naturally occurring internal standards, and tandem electrospray ionization mass spectrometry methods were used to measure the fatty acyl compositions. There was no significant difference in total concentrations of phospholipids in both groups. However, there was a significantly higher concentration of eicosapentaenoic acid containing phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and cholesteryl esters (CE) (p < 0.01) in the high n-3 PUFA group compared to the low n-3 PUFA group in both liver and plasma. Plasma and liver from the high n-3 PUFA group also had a higher concentration of free n-3 PUFA (p < 0.05). There were no significant differences in plasma concentrations of different fatty acyl species of phosphatidylethanolamine, triglycerides, sphingomyelin and ceramides.

Conclusions/Significance

Our findings reveal for the first time that a diet high in n-3 PUFA caused enrichment of n-3 PUFA in PC, LPC, CE and free fatty acids in the plasma and liver of C57BL/6 mice. PC, LPC, and unesterified free n-3 PUFA are important bioactive lipids, thus altering their fatty acyl composition will have important metabolic and physiological roles.

Feeding healthy beagles medium-chain triglycerides, fish oil, and carnitine offsets age-related changes in serum fatty acids and carnitine metabolites

The purpose of this study was to determine if feeding dogs medium-chain triglycerides (MCT), fish oil, and L-carnitine enriched foods offsets age-associated changes in serum fatty acids (FA) and carnitine metabolites. Forty-one healthy Beagles, mean age 9.9 years (range 3.1 to 14.8), were fed control or one of two treatment foods for 6 months. All foods were complete and balanced and met the nutrient requirements for adult dogs, and had similar concentrations of moisture, protein, and fat (approx. 7.4%, 14.0%, and 18.1%, respectively). The treatment diets both contained added L-carnitine (300 mg/kg) and 0.6% (treatment food 1) or 1.5% (treatment food 2) added fish oil. Treatment food 2 also had increased MCT from coconut oil, added corn oil, and reduced animal fat. Composition of serum FA was determined by gas chromatography of FA methyl esters. Metabolomic profiles of serum samples were determined from extracted supernatants that were split and run on GC/MS and LC/MS/MS platforms, for identification and relative quantification of small metabolites. Body composition was determined by dual energy x-ray absorptiometry. Among dog groups, there was no change in total-lean-body weight, or in serum total protein and serum albumin concentrations, based on time or dietary treatment. Serum concentrations of carnitine metabolites were decreased in geriatric (>7 years) vs. mature adult (≤ 7 years) dogs, and supplementation with L-carnitine attenuated the effects of aging. The ratio of PUFA to SFA was significantly greater in mature dogs at baseline (P ≤ 0.05). Serum concentrations of eicosapentaenoic and docosahexaenoic FA increased in a dose-dependent manner. Dogs consuming treatment food 2 also had increased serum concentrations of lauric and myristic FA, and decreased concentrations of SFA, MUFA, and arachidonate (all P ≤ 0.05) and their PUFA to SFA ratio increased. In summary, dietary MCT, fish oil, and L-carnitine counterbalanced the effects of aging on circulating concentrations of these compounds.

The combination of EPA+DHA and low-dose aspirin ingestion reduces platelet function acutely whereas each alone may not in healthy humans

INTRODUCTION

Aspirin's effectiveness in reducing cardiovascular disease events is inadequate in some individuals, a phenomenon termed aspirin "resistance". The hypothesis that combining low dose aspirin with eicosapentaenoic acid and docosahexaenoic acid (EPA+DHA) reduces platelet function in the acute setting has not been investigated.

PATIENTS AND METHODS

We conducted a clinical trial of EPA+DHA and aspirin ingestion in healthy adults. Fasting blood samples were drawn at baseline and 4 h after supplementation with EPA/DHA (3.4 g/d), aspirin (81 mg), and both. Platelet function was measured using the Platelet Function Analyzer-100 (PFA-100). Plasma lysophosphatidylcholine (LPC), lysophosphatidic acid (LPA), autotaxin, angiogenesis activators, and cytokines were measured.

RESULTS

Platelet function decreased with the combination of aspirin+EPA/DHA (p=0.03) but not with either alone (p>0.05). EPA-LPC increased (p=0.002).

DISCUSSION AND CONCLUSIONS

Our results demonstrate that a potentially beneficial effect on platelet function occurred within 4h after ingestion of low-dose aspirin and EPA+DHA in healthy adults.

Fish oil supplementation alters the plasma lipidomic profile and increases long-chain PUFAs of phospholipids and triglycerides in healthy subjects

BACKGROUND

While beneficial health effects of fish and fish oil consumption are well documented, the incorporation of n-3 polyunsaturated fatty acids in plasma lipid classes is not completely understood. The aim of this study was to investigate the effect of fish oil supplementation on the plasma lipidomic profile in healthy subjects.

METHODOLOGY/PRINCIPAL FINDINGS

In a double-blinded randomized controlled parallel-group study, healthy subjects received capsules containing either 8 g/d of fish oil (FO) (1.6 g/d EPA+DHA) (n = 16) or 8 g/d of high oleic sunflower oil (HOSO) (n = 17) for seven weeks. During the first three weeks of intervention, the subjects completed a fully controlled diet period. BMI and total serum triglycerides, total-, LDL- and HDL-cholesterol were unchanged during the intervention period. Lipidomic analyses were performed using Ultra Performance Liquid Chromatography (UPLC) coupled to electrospray ionization quadrupole time-of-flight mass spectrometry (QTOFMS), where 568 lipids were detected and 260 identified. Both t-tests and Multi-Block Partial Least Square Regression (MBPLSR) analysis were performed for analysing differences between the intervention groups. The intervention groups were well separated by the lipidomic data after three weeks of intervention. Several lipid classes such as phosphatidylcholine, phosphatidylethanolamine, lysophosphatidylcholine, sphingomyelin, phosphatidylserine, phosphatidylglycerol, and triglycerides contributed strongly to this separation. Twenty-three lipids were significantly decreased (FDR<0.05) in the FO group after three weeks compared with the HOSO group, whereas fifty-one were increased including selected phospholipids and triglycerides of long-chain polyunsaturated fatty acids. After seven weeks of intervention the two intervention groups showed similar grouping.

CONCLUSIONS/SIGNIFICANCE

In healthy subjects, fish oil supplementation alters lipid metabolism and increases the proportion of phospholipids and triglycerides containing long-chain polyunsaturated fatty acids. Whether the beneficial effects of fish oil supplementation may be explained by a remodeling of the plasma lipids into phospholipids and triglycerides of long-chain polyunsaturated fatty acids needs to be further investigated.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01034423.

Lpa2 is a negative regulator of both dendritic cell activation and murine models of allergic lung inflammation

Negative regulation of innate immune responses is essential to prevent excess inflammation and tissue injury and promote homeostasis. Lysophosphatidic acid (LPA) is a pleiotropic lipid that regulates cell growth, migration, and activation and is constitutively produced at low levels in tissues and in serum. Extracellular LPA binds to specific G protein-coupled receptors, whose function in regulating innate or adaptive immune responses remains poorly understood. Of the classical LPA receptors belonging to the Edg family, lpa2 (edg4) is expressed by dendritic cells (DC) and other innate immune cells. In this article, we show that DC from lpa2(-/-) mice are hyperactive compared with their wild-type counterparts and are less susceptible to inhibition by different LPA species. In transient-transfection assays, we found that lpa2 overexpression inhibits NF-κB-driven gene transcription. Using an adoptive-transfer approach, we found that allergen-pulsed lpa2(-/-) DC induced substantially more lung inflammation than did wild-type DC after inhaled allergen challenge. Finally, lpa2(-/-) mice develop greater allergen-driven lung inflammation than do their wild-type counterparts in models of allergic asthma involving both systemic and mucosal sensitization. Taken together, these findings identify LPA acting via lpa2 as a novel negative regulatory pathway that inhibits DC activation and allergic airway inflammation.

Whole grain products, fish and bilberries alter glucose and lipid metabolism in a randomized, controlled trial: the Sysdimet study

Background

Due to the growing prevalence of type 2 diabetes, new dietary solutions are needed to help improve glucose and lipid metabolism in persons at high risk of developing the disease. Herein we investigated the effects of low-insulin-response grain products, fatty fish, and berries on glucose metabolism and plasma lipidomic profiles in persons with impaired glucose metabolism.

Methodology/Principal Findings

Altogether 106 men and women with impaired glucose metabolism and with at least two other features of the metabolic syndrome were included in a 12-week parallel dietary intervention. The participants were randomized into three diet intervention groups: (1) whole grain and low postprandial insulin response grain products, fatty fish three times a week, and bilberries three portions per day (HealthyDiet group), (2) Whole grain enriched diet (WGED) group, which includes principally the same grain products as group (1), but with no change in fish or berry consumption, and (3) refined wheat breads (Control). Oral glucose tolerance, plasma fatty acids and lipidomic profiles were measured before and after the intervention. Self-reported compliance with the diets was good and the body weight remained constant. Within the HealthyDiet group two hour glucose concentration and area-under-the-curve for glucose decreased and plasma proportion of (n-3) long-chain PUFAs increased (False Discovery Rate p-values <0.05). Increases in eicosapentaenoic acid and docosahexaenoic acid associated curvilinearly with the improved insulin secretion and glucose disposal. Among the 364 characterized lipids, 25 changed significantly in the HealthyDiet group, including multiple triglycerides incorporating the long chain (n-3) PUFA.

Conclusions/Significance

The results suggest that the diet rich in whole grain and low insulin response grain products, bilberries, and fatty fish improve glucose metabolism and alter the lipidomic profile. Therefore, such a diet may have a beneficial effect in the efforts to prevent type 2 diabetes in high risk persons.

Trial Registration

ClinicalTrials.gov NCT00573781

Dietary fish oil alters the lysophospholipid metabolomic profile and decreases urinary 11-dehydro thromboxane B₂ concentration in healthy Beagles

Increased concentrations of dietary fish oil and antioxidants have been shown previously to change circulating concentrations of individual fatty acids (FAs) and vitamin E. The purpose of this study was to further investigate the effects of vitamins E and C, in combination with dietary fish oil, on selected blood and urinary biomarkers. Fifty adult Beagle dogs (mean age 5.3 years, range 1.4-14.2 years) were randomized into five dietary treatment groups for 90 days. All foods were complete and balanced and met the nutrient profiles of AAFCO for adult dogs. For 60 days before study initiation, dogs consumed a pretrial food that contained 74 IU/kg vitaminE and 0mg/kg vitaminC. The five experimental foods were confirmed by analytical methods to contain ≥ 640 IU/kg vitaminE and 130 mg/kg vitaminC (as fed). Experimental foods ranged from low levels of EPA and DHA (pretrial food and lowest experimental food had 0.01% EPA and no detectable DHA) to the highest experimental food with 0.25% EPA and 0.17% DHA. Serum was analyzed for FAs, vitamin E, and cholesterol concentrations; urine was analyzed for 11-dehydro thromboxane B(2) (TXB(2)). Serum was also used for metabolomic analysis. FA intake ranged from 0.02 g/day EPA and 0.02 g/day DHA to 0.58 g/day EPA and 0.39 g/day DHA. Increasing dietary concentrations of EPA and DHA resulted in increased serum concentrations of EPA and DHA in a dose-dependent fashion. Greater dietary vitamin E intake resulted in increased serum vitamin E concentrations (P<0.01). Higher serum cholesterol was also associated with higher serum vitamin E concentrations (P<0.01). In turn, changes in serum cholesterol concentration were associated with diet-induced changes in serum FA concentrations (all P<0.01). At the beginning of the dietary treatment period the most significant predictor of urine 11-dehydro TXB(2) concentration was age, followed by lean-body mass. After dietary treatment with different amounts of fish oil, age (increases 11-dehydro TXB(2)) was followed by EPA concentration as a significant negative predictor of urine 11-dehydro TXB(2) concentration (increasing serum concentrations of EPA decrease 11-dehydro TXB(2)), and then lean-body mass (decreases 11-dehydro TXB(2)). Serum docosahexaenoyl-glycerophosphocholine concentration was increased by feeding fish oil in a dose-response manner. In summary, serum vitamin E concentration is enhanced primarily by feeding vitamin E and secondarily by serum cholesterol concentration. When feeding diets enriched with fish oil, the major negative predictor of urinary 11-dehydro TXB(2) concentration is serum EPA concentration. Plasma lysophospholipids can be dynamically regulated by dietary fish oil supplementation.