Prevention of 1-palmitoyl lysophosphatidylcholine-induced inflammation by polyunsaturated acyl lysophosphatidylcholine

Sex-specific perturbation of complex lipids in response to medium-chain fatty acids in very long-chain acyl-CoA dehydrogenase deficiency

Very-long-chain acyl-CoA dehydrogenase deficiency (VLCAD) is the most common defect of long-chain fatty acid β-oxidation. The recommended treatment includes the application of medium-chain triacylglycerols (MCTs). However, long-term treatment of VLCAD^-/- mice resulted in the development of a sex-specific metabolic syndrome due to the selective activation of the ERK/mTORc1 signalling in females and ERK/peroxisome proliferator-activated receptor gamma pathway in males. In order to investigate a subsequent sex-specific effect of MCT on the lipid composition of the cellular membranes, we performed lipidomic analysis, SILAC-based quantitative proteomics and gene expression in fibroblasts from WT and VLCAD^-/- mice of both sexes. Treatment with octanoate (C8) affected the composition of complex lipids resulting in a sex-specific signature of the molecular profile. The content of ceramides and sphingomyelins in particular differed significantly under control conditions and increased markedly in cells from mutant female mice but remained unchanged in cells from mutant males. Moreover, we observed a specific upregulation of biosynthesis of plasmalogens only in male mice, whereas in females C8 led to the accumulation of higher concentration of phosphatidylcholines and lysophosphatidylcholines. Our data on membrane lipids in VLCAD after supplementation with C8 provide evidence of a sex-specific lipid perturbation. We hypothesize a likely C8-induced pro-inflammatory response contributing to the development of a severe metabolic syndrome in female VLCAD^-/- mice on long-term MCT supplementation.

Structure-function relationships of HDL in diabetes and coronary heart disease

High-density lipoproteins (HDL) contain hundreds of lipid species and proteins and exert many potentially vasoprotective and antidiabetogenic activities on cells. To resolve structure-function-disease relationships of HDL, we characterized HDL of 51 healthy subjects and 98 patients with diabetes (T2DM), coronary heart disease (CHD), or both for protein and lipid composition, as well as functionality in 5 cell types. The integration of 40 clinical characteristics, 34 nuclear magnetic resonance (NMR) features, 182 proteins, 227 lipid species, and 12 functional read-outs by high-dimensional statistical modeling revealed, first, that CHD and T2DM are associated with different changes of HDL in size distribution, protein and lipid composition, and function. Second, different cellular functions of HDL are weakly correlated with each other and determined by different structural components. Cholesterol efflux capacity (CEC) was no proxy of other functions. Third, 3 potentially novel determinants of HDL function were identified and validated by the use of artificially reconstituted HDL, namely the sphingadienine-based sphingomyelin SM 42:3 and glycosylphosphatidylinositol-phospholipase D1 for the ability of HDL to inhibit starvation-induced apoptosis of human aortic endothelial cells and apolipoprotein F for the ability of HDL to promote maximal respiration of brown adipocytes.

Lipidomic Profile Revealed the Association of Plasma Lysophosphatidylcholines with Adolescent Obesity

Objective

The human lipidomic profile reflects lipid metabolism, including the early phase of pathophysiological changes associated with diseases. An investigation of the association between the plasma lipidomic profile and adolescent obesity might provide new insights into the biological mechanisms of obesity. Therefore, we aimed to investigate the association of the plasma lipidome with obesity in Chinese adolescents using lipidomics.

Methods

Using a combination of liquid chromatography and electrospray ionization tandem mass spectrometry, we quantified 328 lipid species from 24 lipid classes and subclasses in 100 male adolescents aged 14–16 years who were categorized into four groups: (1) normal weight with traditional normal clinical plasma lipid levels (NN); (2) normal weight with traditional abnormal clinical plasma lipid levels (NA); (3) obese with traditional normal clinical plasma lipid levels (ON); and (4) obese with traditional abnormal clinical plasma lipid levels (OA). The concentrations of all the lipid species were compared between obese and normal-weight adolescents at different traditional clinical plasma lipid levels using the Kruskal–Wallis test followed by the Mann–Whitney U test. A partial least squares discriminant analysis (PLS-DA) was applied to select lipids with a significant ability to discriminate adolescent obesity.

Results

The lipidomic profile distinguished obese adolescents from normal-weight subjects. Regardless of whether traditional clinical plasma lipid levels were normal or abnormal, we observed a significant reduction in the levels of five lysophosphatidylcholines (LPC) species (LPC18:2, LPC18:1, LPC20:2, LPC20:1, and LPC20:0) in the obese group compared with the normal-weight group (difference = −31.29% to −13.19%; P=9.91 × 10⁻⁵ to 2.28 × 10⁻²). The ability of these five LPC species to discriminate adolescent obesity was confirmed in the PLS-DA model.

Conclusions

The findings provided evidence for the association of some LPC species with adolescent obesity. The discriminatory effects of five LPC species were identified between normal-weight and obese adolescents, independent of traditional clinical plasma lipid levels. These results will provide a basis for validation in subsequent studies.

Enrichment of brain docosahexaenoic acid (DHA) is highly dependent upon the molecular carrier of dietary DHA: lysophosphatidylcholine is more efficient than either phosphatidylcholine or triacylglycerol

Docosahexaenoic acid (DHA) is highly concentrated in the brain, and its deficiency is associated with several neurological disorders including Alzheimer's disease. However, the currently used supplements do not appreciably enrich brain DHA, although they enrich most other tissues. We tested the hypothesis that the ability of the dietary carrier to augment brain DHA depends upon the generation of DHA-lysophosphatidylcholine (LPC), the preferred carrier of DHA across the blood brain barrier. We compared the efficacy of DHA-triacylglycerol (TAG), di-DHA phosphatidylcholine (PC) and DHA-LPC to enrich brain DHA following their gavage to normal rats for 30 days, all at a dose of 10 mg DHA/day. The results show that DHA from TAG, which is released as free DHA or monoacylglycerol during digestion and is absorbed as TAG in chylomicrons, was incorporated preferentially into adipose tissue and heart but not into brain. In contrast, LPC-DHA increased brain DHA by up to 100% but had no effect on adipose tissue. Di-DHA PC, which generates both free DHA and LPC-DHA during the digestion, enriched DHA in brain, as well as in heart and liver. Brain-derived neurotrophic factor was increased by di-DHA PC and DHA-LPC, but not by TAG-DHA, showing that enrichment of brain DHA correlated with its functional effect. We conclude that dietary DHA from TAG or from natural PC (sn-2 position) is not suitable for brain enrichment, whereas DHA from LPC (at either sn-1 or sn-2 position) or from sn-1 position of PC efficiently enriches the brain and is functionally effective.

Dysregulated Choline, Methionine, and Aromatic Amino Acid Metabolism in Patients with Wilson Disease: Exploratory Metabolomic Profiling and Implications for Hepatic and Neurologic Phenotypes

Wilson disease (WD) is a genetic copper overload condition characterized by hepatic and neuropsychiatric symptoms with a not well-understood pathogenesis. Dysregulated methionine cycle is reported in animal models of WD, though not verified in humans. Choline is essential for lipid and methionine metabolism. Defects in neurotransmitters as acetylcholine, and biogenic amines are reported in WD; however, less is known about their circulating precursors. We aimed to study choline, methionine, aromatic amino acids, and phospholipids in serum of WD subjects. Hydrophilic interaction chromatography-quadrupole time-of-flight mass spectrometry was employed to profile serum of WD subjects categorized as hepatic, neurologic, and pre-clinical. Hepatic transcript levels of genes related to choline and methionine metabolism were verified in the Jackson Laboratory toxic milk mouse model of WD (tx-j). Compared to healthy subjects, choline, methionine, ornithine, proline, phenylalanine, tyrosine, and histidine were significantly elevated in WD, with marked alterations in phosphatidylcholines and reductions in sphingosine-1-phosphate, sphingomyelins, and acylcarnitines. In tx-j mice, choline, methionine, and phosphatidylcholine were similarly dysregulated. Elevated choline is a hallmark dysregulation in WD interconnected with alterations in methionine and phospholipid metabolism, which are relevant to hepatic steatosis. The elevated phenylalanine, tyrosine, and histidine carry implications for neurologic manifestations and are worth further investigation.

[High-performance liquid chromatography-mass spectrometry-based serum metabolic profiling in patients with HBV-related hepatocellular carcinoma]

OBJECTIVE

To explore the diagnostic value of the serum metabolites identified by high-performance liquid chromatography-mass spectrometry (HPLC/MS) for hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC).

METHODS

A total of 126 patients admitted to Tianjin Third Central Hospital were enrolled, including 27 patients with HBV-related hepatitis with negative viral DNA (DNA-N), 24 with HBV-related hepatitis with positive viral DNA, 24 with HBV-related liver cirrhosis, 27 with HBV-related HCC undergoing surgeries or radiofrequency ablation, and 24 with HBV-related HCC receiving interventional therapy, with 25 healthy volunteers as the normal control group. Serum samples were collected from all the subjects for HPLC/MS analysis, and the data were pretreated to establish an orthogonal partial least- squares discriminant analysis (OPLS-DA) model. The differential serum metabolites were preliminarily screened by comparisons between the HBV groups and the control group, and the characteristic metabolites were identified according to the results of non-parametric test. The potential clinical values of these characteristic metabolites were evaluated using receiver operator characteristic curve (ROC) analysis.

RESULTS

A total of 25 characteristic metabolites were identified in the HBV- infected patients, including 9 lysophosphatidylcholines, 2 fatty acids, 17α-estradiol, sphinganine, 5-methylcytidine, vitamin K2, lysophosphatidic acid, glycocholic acid and 8 metabolites with few reports. The patients with HBV- related HCC showed 22 differential serum metabolites compared with the control group, 4 differential metabolites compared with patients with HBV-related liver cirrhosis; 10 differential metabolites were identified in patients with HBV-related HCC receiving interventional therapy compared with those receiving surgical resection or radiofrequency ablation. From the normal control group to HBV-related HCC treated by interventional therapy, many metabolites underwent variations following a similar pattern.

CONCLUSIONS

We identified 25 characteristic metabolites in patients with HBV-related HCC, and these metabolites may have potential clinical values in the diagnosis of HBV-related HCC. The continuous change of some of these metabolites may indicate the possibility of tumorigenesis, and some may also have indications for the choice of surgical approach.

The Role of Lipids in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disease characterized by a progressive loss of dopaminergic neurons from the nigrostriatal pathway, formation of Lewy bodies, and microgliosis. During the past decades multiple cellular pathways have been associated with PD pathology (i.e., oxidative stress, endosomal-lysosomal dysfunction, endoplasmic reticulum stress, and immune response), yet disease-modifying treatments are not available. We have recently used genetic data from familial and sporadic cases in an unbiased approach to build a molecular landscape for PD, revealing lipids as central players in this disease. Here we extensively review the current knowledge concerning the involvement of various subclasses of fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, and lipoproteins in PD pathogenesis. Our review corroborates a central role for most lipid classes, but the available information is fragmented, not always reproducible, and sometimes differs by sex, age or PD etiology of the patients. This hinders drawing firm conclusions about causal or associative effects of dietary lipids or defects in specific steps of lipid metabolism in PD. Future technological advances in lipidomics and additional systematic studies on lipid species from PD patient material may improve this situation and lead to a better appreciation of the significance of lipids for this devastating disease.

Lipidomic Response to Coffee Consumption

Coffee is widely consumed and contains many bioactive compounds, any of which may impact pathways related to disease development. Our objective was to identify individual lipid changes in response to coffee drinking. We profiled the lipidome of fasting serum samples collected from a previously reported single blinded, three-stage clinical trial. Forty-seven habitual coffee consumers refrained from drinking coffee for 1 month, consumed 4 cups of coffee/day in the second month and 8 cups/day in the third month. Samples collected after each coffee stage were subject to quantitative lipidomic profiling using ion-mobility spectrometry–mass spectrometry. A total of 853 lipid species mapping to 14 lipid classes were included for univariate analysis. Three lysophosphatidylcholine (LPC) species including LPC (20:4), LPC (22:1) and LPC (22:2), significantly decreased after coffee intake (p < 0.05 and q < 0.05). An additional 72 species mapping to the LPC, free fatty acid, phosphatidylcholine, cholesteryl ester and triacylglycerol classes of lipids were nominally associated with coffee intake (p < 0.05 and q > 0.05); 58 of these decreased after coffee intake. In conclusion, coffee intake leads to lower levels of specific LPC species with potential impacts on glycerophospholipid metabolism more generally.

Lysophosphatidylcholine induces expression of genes involved in cholesterol biosynthesis in THP-1 derived macrophages

Lysophosphatidylcholine (LPC), a major component of oxidized low-density lipoprotein, is associated with atherosclerosis, obesity, stroke, and cancer. However, the direction and mechanism of this relationship remains unclear. In this study, we conducted RNA profiling in THP-1 derived macrophages treated with LPC and uncovered a relationship between LPC and the cholesterol biosynthesis pathway. Principal component analysis (PCA) of RNA profiling showed that untreated THP-1 cells and those treated with 10, 20, or 40 µM LPC were distinctly distributed. Functional annotation revealed that LPC affected the expression of genes involved in cytokine-cytokine receptor interaction, TNF signaling, and MAPK signaling. Interestingly, LPC also altered the expression of 11 genes involved in cholesterol synthesis such as those in terpenoid backbone biosynthesis and steroid biosynthesis pathways. This increased gene expression occurred in a dose-dependent manner in response to LPC treatment. Especially, LPC with saturated acyl groups enhanced the expression of these genes compared to LPC with unsaturated acyl groups, and similar results were shown in response to saturated and unsaturated free fatty acids. Our findings demonstrate that LPCs with saturated acyl groups induce the expression of genes involved in cholesterol biosynthesis and may have implications for cholesterol related diseases.

Analysis of lipoprotein-specific lipids in patients with acute coronary syndrome by asymmetrical flow field-flow fractionation and nanoflow liquid chromatography-tandem mass spectrometry

A comprehensive lipid analysis was performed at the plasma lipoprotein level in patients with acute coronary syndrome (ACS) and stable coronary artery disease (CAD). Because the lipids in lipoproteins are related to the pathology of the cardiovascular system, lipoprotein-specific lipid analysis can be useful for understanding the mechanism of lipid-associated cardiovascular diseases. Lipoproteins were size-sorted into high density lipoproteins (HDL) and low density lipoproteins (LDL) using asymmetrical flow field-flow fractionation, then lipids of each lipoprotein were analysed using nanoflow ultrahigh performance liquid chromatography-electrospray ionization-tandem mass spectrometry. A total of 365 lipids were structurally identified and quantified by selected reaction monitoring method. Two high abundance lysophosphatidylcholines (16:0 and 18:0) were significantly increased only in the HDL of the ACS group (vs. the stable CAD group). Phosphatidylethanolamines (38:5 and 40:5) significantly increased in ACS by >2-fold in both lipoproteins. (18:0, 22:6)-diacylglycerol increased in ACS by 3.5-fold only in LDL; however, most high abundance triacylglycerols decreased 2-fold in both lipoproteins. The present study revealed the usefulness of lipoprotein-specific analysis of lipids in distinguishing ACS from stable CAD, and the selected lipids analysed in this study may be useful in the development of lipid markers for the early detection of ACS.

Metabolomic and lipidomic analysis of the effect of pioglitazone on hepatic steatosis in a rat model of obese Type 2 diabetes

BACKGROUND AND PURPOSE

Thiazolidinediones, acting as PPAR-γ ligands, reduce hepatic steatosis in humans and animals. However, the underlying mechanism of this action remains unclear. The purpose of this study was to investigate changes in hepatic metabolites and lipids in response to treatment with the thiazolidinedione pioglitazone in an animal model of obese Type 2 diabetes.

EXPERIMENTAL APPROACH

Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats were orally administered either vehicle (control) or pioglitazone (30 mg·kg^-1 ) and fed a high-fat diet (60% kcal fat) for 12 weeks. Hepatic metabolites were analysed via metabolomic and lipidomic analyses. Gene expression and PLA₂ activity were analysed in livers from pioglitazone-treated and control rats.

KEY RESULTS

OLETF rats that received pioglitazone showed decreased fat accumulation and improvement of lipid profiles in the liver compared to control rats. Pioglitazone treatment significantly altered levels of hepatic metabolites, including free fatty acids, lysophosphatidylcholines and phosphatidylcholines, in the liver. In addition, pioglitazone significantly reduced the expression of genes involved in hepatic de novo lipogenesis and fatty acid uptake and transport, whereas genes related to fatty acid oxidation were up-regulated. Gene expression and enzyme activity of PLA₂ , which hydrolyzes phosphatidylcholines to release lysophosphatidylcholines and free fatty acids, were significantly decreased in the livers of pioglitazone-treated rats compared to control rats.

CONCLUSIONS AND IMPLICATIONS

Our results present evidence for the ameliorative effect of pioglitazone on hepatic steatosis, largely due to the regulation of lipid metabolism, including fatty acids, lysophosphatidylcholines, phosphatidylcholines and related gene-expression patterns.

Adipocyte-derived Lysophosphatidylcholine Activates Adipocyte and Adipose Tissue Macrophage Nod-Like Receptor Protein 3 Inflammasomes Mediating Homocysteine-Induced Insulin Resistance

The adipose Nod-like receptor protein 3 (NLRP3) inflammasome senses danger-associated molecular patterns (DAMPs) and initiates insulin resistance, but the mechanisms of adipose inflammasome activation remains elusive. In this study, Homocysteine (Hcy) is revealed to be a DAMP that activates adipocyte NLRP3 inflammasomes, participating in insulin resistance. Hcy-induced activation of NLRP3 inflammasomes were observed in both adipocytes and adipose tissue macrophages (ATMs) and mediated insulin resistance. Lysophosphatidylcholine (lyso-PC) acted as a second signal activator, mediating Hcy-induced adipocyte NLRP3 inflammasome activation. Hcy elevated adipocyte lyso-PC generation in a hypoxia-inducible factor 1 (HIF1)-phospholipase A2 group 16 (PLA2G16) axis-dependent manner. Lyso-PC derived from the Hcy-induced adipocyte also activated ATM NLRP3 inflammasomes in a paracrine manner. This study demonstrated that Hcy activates adipose NLRP3 inflammasomes in an adipocyte lyso-PC-dependent manner and highlights the importance of the adipocyte NLRP3 inflammasome in insulin resistance.

Metabolomic study on the antihypertensive effect of S-1-propenylcysteine in spontaneously hypertensive rats using liquid chromatography coupled with quadrupole-Orbitrap mass spectrometry

Aged garlic extract (AGE) has been shown to improve hypertension in both clinical trials and experimental animal models. However, the active ingredient of AGE remains unknown. In the present study, we investigated the antihypertensive effects of AGE and its major constituents including S-1-propenylcysteine (S1PC) and S-allylcysteine (SAC) using spontaneously hypertensive rats (SHR) and found that S1PC is an active substance to lower blood pressure in SHR. In addition, the metabolomics approach was used to investigate the potential mechanism of the antihypertensive action of S1PC in SHR. Treatment with AGE (2g/kg body weight) or S1PC (6.5mg/kg body weight; equivalent to AGE 2g/kg body weight) significantly decreased the systolic blood pressure (SBP) of SHR after the repeated administration for 10 weeks, whereas treatment with SAC (7.9mg/kg body weight; equivalent to AGE 2g/kg body weight) did not decrease the SBP. After the treatment for 10 weeks, the plasma samples obtained from Wistar Kyoto (WKY) rats and SHR were analyzed by means of ultra high performance liquid chromatography coupled with high-resolution quadrupole-Orbitrap mass spectrometry. Multivariate statistical analysis of LC-MS data showed a clear difference in the metabolite profiles between WKY rats and SHR. The results indicated that 30 endogenous metabolites significantly contributed to the difference and 7 of 30 metabolites were changed by the S1PC treatment. Furthermore, regression analysis showed correlation between SBP and the plasma levels of betaine, tryptophan and 3 LysoPCs. This metabolomics approach suggested that S1PC could exert its antihypertensive effect by affecting glycine, serine and threonine metabolism, tryptophan metabolism and glycerophospholipid metabolism.

Chlorinated Phospholipids and Fatty Acids: (Patho)physiological Relevance, Potential Toxicity, and Analysis of Lipid Chlorohydrins

Chlorinated phospholipids are formed by the reaction of hypochlorous acid (HOCl), generated by the enzyme myeloperoxidase under inflammatory conditions, and the unsaturated fatty acyl residues or the head group. In the first case the generated chlorohydrins are both proinflammatory and cytotoxic, thus having a significant impact on the structures of biomembranes. The latter case leads to chloramines, the properties of which are by far less well understood. Since HOCl is also widely used as a disinfecting and antibacterial agent in medicinal, industrial, and domestic applications, it may represent an additional source of danger in the case of abuse or mishandling. This review discusses the reaction behavior of in vivo generated HOCl and biomolecules like DNA, proteins, and carbohydrates but will focus on phospholipids. Not only the beneficial and pathological (toxic) effects of chlorinated lipids but also the importance of these chlorinated species is discussed. Some selected cleavage products of (chlorinated) phospholipids and plasmalogens such as lysophospholipids, (chlorinated) free fatty acids and α-chloro fatty aldehydes, which are all well known to massively contribute to inflammatory diseases associated with oxidative stress, will be also discussed. Finally, common analytical methods to study these compounds will be reviewed with focus on mass spectrometric techniques.

Exploring the Inflammatory Metabolomic Profile to Predict Response to TNF-α Inhibitors in Rheumatoid Arthritis

In clinical practice, approximately one-third of patients with rheumatoid arthritis (RA) respond insufficiently to TNF-α inhibitors (TNFis). The aim of the study was to explore the use of a metabolomics to identify predictors for the outcome of TNFi therapy, and study the metabolomic fingerprint in active RA irrespective of patients’ response. In the metabolomic profiling, lipids, oxylipins, and amines were measured in serum samples of RA patients from the observational BiOCURA cohort, before start of biological treatment. Multivariable logistic regression models were established to identify predictors for good- and non-response in patients receiving TNFi (n = 124). The added value of metabolites over prediction using clinical parameters only was determined by comparing the area under receiver operating characteristic curve (AUC-ROC), sensitivity, specificity, positive- and negative predictive value and by the net reclassification index (NRI). The models were further validated by 10-fold cross validation and tested on the complete TNFi treatment cohort including moderate responders. Additionally, metabolites were identified that cross-sectionally associated with the RA disease activity score based on a 28-joint count (DAS28), erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP). Out of 139 metabolites, the best-performing predictors were sn1-LPC(18:3-ω3/ω6), sn1-LPC(15:0), ethanolamine, and lysine. The model that combined the selected metabolites with clinical parameters showed a significant larger AUC-ROC than that of the model containing only clinical parameters (p = 0.01). The combined model was able to discriminate good- and non-responders with good accuracy and to reclassify non-responders with an improvement of 30% (total NRI = 0.23) and showed a prediction error of 0.27. For the complete TNFi cohort, the NRI was 0.22. In addition, 88 metabolites were associated with DAS28, ESR or CRP (p<0.05). Our study established an accurate prediction model for response to TNFi therapy, containing metabolites and clinical parameters. Associations between metabolites and disease activity may help elucidate additional pathologic mechanisms behind RA.

Impairment of lysophospholipid metabolism in obesity: altered plasma profile and desensitization to the modulatory properties of n-3 polyunsaturated fatty acids in a randomized controlled trial

BACKGROUND

Plasma lysophospholipids have emerged as signaling molecules with important effects on inflammation, insulin resistance, and fatty liver disease, each of which is linked closely to obesity. Dietary n-3 (ω-3) polyunsaturated fatty acids (PUFAs) may be able to improve these conditions.

OBJECTIVE

The objective of this study was to assess the response of plasma lysophospholipids to obesity, n-3 PUFA consumption, and a high-fat meal challenge to better understand the role of lysophospholipid metabolism in the progression of obesity-related disorders.

DESIGN

We determined the concentrations of 8 lysophosphatidylcholines, 11 lysophosphatidylethanolamines, and 7 lysophosphatidylinositols in the plasma of 34 normal-weight and 38 obese subjects randomly assigned to consume corn oil (control) or n-3 PUFA-rich fish oil (3 g/d; n = 15-19/group) for 90 d. Blood samples were collected on the last day of the study under fasting conditions and 6 h after a high-fat meal (1135 kcal, 86 g fat) challenge. The profile of secreted lysophospholipids was studied in HepG2 cells under palmitate-induced steatosis.

RESULTS

Obese and normal-weight subjects had different profiles of plasma lysophospholipids. A multivariate combination of the 26 lysophospholipids could discriminate between normal-weight and obese subjects with an accuracy of 98%. The high-fat meal challenge altered the concentration of plasma lysophosphatidylcholines in an oil treatment-dependent manner in normal-weight but not obese subjects, suggesting that obesity impairs the sensitivity of lysophospholipid metabolism to n-3 PUFAs. Noncytotoxic steatosis in HepG2 cells affected the secretion pattern of lysophospholipids, partially resembling the changes observed in the plasma of obese subjects.

CONCLUSIONS

Obesity has a substantial impact on lysophospholipid metabolism, altering the plasma lysophospholipid profile and abolishing its sensitivity to dietary n-3 PUFAs. These effects could contribute to the onset or progression of alterations associated with obesity, such as inflammation, insulin resistance, and fatty liver disease. This trial was registered at www.controlled-trials.com as ISRCTN96712688.

Metabolomics of the Antipyretic Effects of Bubali Cornu (Water Buffalo Horn) in Rats

Bubali Cornu (water buffalo horn, WBH) has been used for thousands of years in traditional Chinese medicine (TCM) as an effective treatment for heat. In the present study, we have carried out a metabolomics profiling study on plasma and urine samples to explore potential biomarkers and determine how WBH exerts its antipyretic effects in yeast-induced pyrexia at a metabolomic level. Ultra-high performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS), together with multivariate statistical analysis, was used to detect and identify potential biomarkers associated with pyrexia and with WBH treatment. In total, sixteen endogenous metabolites were identified in plasma samples and twenty-one metabolites were detected in urine samples. The biomarkers identified in this study, using metabolic pathway analysis (MetPA), are involved in glycerophospholipid, arachidonic acid, amino acid, sphingolipid, and purine metabolism, all of which are disturbed in rats with pyrexia. As a result, WBH affect arachidonic acid metabolism and oxidative stress in yeast-induced pyrexia rats chiefly. The present study determines the important substances underlying the antipyretic efficacy of WBH at a metabolic level. It might pave the way for further investigations into the mechanisms of action of other animal horn-derived traditional Chinese medicines (TCMs).

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.

Mass spectrometry-based metabolite profiling in the mouse liver following exposure to ultraviolet B radiation

Although many studies have been performed on the effects of ultraviolet (UV) radiation on the skin, only a limited number of reports have investigated these effects on non-skin tissue. This study aimed to describe the metabolite changes in the liver of hairless mice following chronic exposure to UVB radiation. We did not observe significant macroscopic changes or alterations in hepatic cholesterol and triglyceride levels in the liver of UVB-irradiated mice, compared with those for normal mice. In this study, we detected hepatic metabolite changes by UVB exposure and identified several amino acids, fatty acids, nucleosides, carbohydrates, phospholipids, lysophospholipids, and taurine-conjugated cholic acids as candidate biomarkers in response to UVB radiation in the mouse liver by using various mass spectrometry (MS)-based metabolite profiling including ultra-performance liquid chromatography-quadrupole time-of-flight (TOF)-MS, gas chromatography-TOF-MS and nanomate LTQ-MS. Glutamine exhibited the most dramatic change with a 5-fold increase in quantity. The results from altering several types of metabolites suggest that chronic UVB irradiation may impact significantly on major hepatic metabolism processes, despite the fact that the liver is not directly exposed to UVB radiation. MS-based metabolomic approach for determining regulatory hepatic metabolites following UV irradiation will provide a better understanding of the relationship between internal organs and UV light.

Lysophospholipid profile in serum and liver by high-fat diet and tumor induction in obesity-resistant BALB/c mice

OBJECTIVE

Our previous study revealed that chronic consumption of a high-fat diet (HFD) stimulates colon cancer progression in obesity-resistant BALB/c mice. The aim of the present study was to investigate the significant alteration of metabolites caused by tumor progression and an HFD in the serum and liver in the same mouse model.

METHODS

Male BALB/c mice were fed either a control diet or a HFD for 20.5 wk. The syngeneic CT26 colon carcinoma cells were injected into the right rear flank of mice after 16 wk of feeding. Metabolites in serum and liver samples were analyzed by ultra-performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry-based metabolomics.

RESULTS

HFD feeding and tumor injection induced changes in the choline-containing phospholipids, namely, phosphatidylcholines and lysophosphatidylcholines (lysoPCs), and lysophosphatidylethanolamines in the serum and liver. The majority of these metabolite changes were due to HFD feeding (11 in sera and 5 in livers) rather than tumors (3 in sera and 1 in livers).

CONCLUSION

The HFD- and tumor-related metabolite alterations of phospholipids, especially lysoPCs, in the liver and serum of obesity-resistant mice, suggesting that the lysoPCs are potential biomarkers for the chronic consumption of HFD in nonobese individuals.

Metabolic fingerprint of Gestational Diabetes Mellitus

Gestational Diabetes (GDM) is causing severe short- and long-term complications for mother, fetus or neonate. As yet, the metabolic alterations that are specific for the development of GDM have not been fully determined, which also precludes the early diagnosis and prognosis of this pathology. In this pilot study, we determine the metabolic fingerprint, using a multiplatform LC-QTOF/MS, GC-Q/MS and CE-TOF/MS system, of plasma and urine samples of 20 women with GDM and 20 with normal glucose tolerance in the second trimester of pregnancy. Plasma fingerprints allowed for the discrimination of GDM pregnant women from controls. In particular, lysoglycerophospholipids showed a close association with the glycemic state of the women. In addition, we identified some metabolites with a strong discriminative power, such as LPE(20:1), (20:2), (22:4); LPC(18:2), (20:4), (20:5); LPI(18:2), (20:4); LPS(20:0) and LPA(18:2), as well as taurine-bile acids and long-chain polyunsaturated fatty acid derivatives. Finally, we provide evidence for the implication of these compounds in metabolic routes, indicative of low-grade inflammation and altered redox-balance, that may be related with the specific pathophysiological context of the genesis of GDM. This highlights their potential use as prognostic markers for the identification of women at risk to develop severe glucose intolerance during pregnancy.

BIOLOGICAL SIGNIFICANCE

Gestational Diabetes Mellitus (GDM) is increasing worldwide and, although diabetes usually remits after pregnancy, women with GDM have a high risk of developing postpartum type 2-diabetes, particularly when accompanied by obesity. Therefore, understanding the pathophysiology of GDM, as well as the identification of potentially modifiable risk factors and early diagnostic markers for GDM are relevant issues. In the present study, we devised a multiplatform metabolic fingerprinting approach to obtain a comprehensive picture of the early metabolic alternations that occur in GDM, and may reflect on the specific pathophysiological context of the disease. Future studies at later stages of gestation will allow us to validate the discriminant power of the identified metabolites.

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.

Biomolecular signatures of diabetic wound healing by structural mass spectrometry

Wound fluid is a complex biological sample containing byproducts associated with the wound repair process. Contemporary techniques, such as immunoblotting and enzyme immunoassays, require extensive sample manipulation and do not permit the simultaneous analysis of multiple classes of biomolecular species. Structural mass spectrometry, implemented as ion mobility-mass spectrometry (IM-MS), comprises two sequential, gas-phase dispersion techniques well suited for the study of complex biological samples because of its ability to separate and simultaneously analyze multiple classes of biomolecules. As a model of diabetic wound healing, poly(vinyl alcohol) sponges were inserted subcutaneously into nondiabetic (control) and streptozotocin-induced diabetic rats to elicit a granulation tissue response and to collect acute wound fluid. Sponges were harvested at days 2 or 5 to capture different stages of the early wound-healing process. Utilizing IM-MS, statistical analysis, and targeted ultraperformance liquid chromatography analysis, biomolecular signatures of diabetic wound healing have been identified. The protein S100-A8 was highly enriched in the wound fluids collected from day 2 diabetic rats. Lysophosphatidylcholine (20:4) and cholic acid also contributed significantly to the differences between diabetic and control groups. This report provides a generalized workflow for wound fluid analysis demonstrated with a diabetic rat model.

Novel bioactive glycerol-based lysophospholipids: new data -- new insight into their function

Based on the results of research conducted over last two decades, lysophospholipids (LPLs) were observed to be not only structural components of cellular membranes but also biologically active molecules influencing a broad variety of processes such as carcinogenesis, neurogenesis, immunity, vascular development or regulation of metabolic diseases. With a growing interest in the involvement of extracellular lysophospholipids in both normal physiology and pathology, it has become evident that those small molecules may have therapeutic potential. While lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) have been studied in detail, other LPLs such as lysophosphatidylglycerol (LPG), lysophosphatidylserine (LPS), lysophosphatidylinositol (LPI), lysophosphatidylethanolamine (LPE) or even lysophosphatidylcholine (LPC) have not been elucidated to such a high degree. Although information concerning the latter LPLs is sparse as compared to LPA and S1P, within the last couple of years much progress has been made. Recently published data suggest that these compounds may regulate fundamental cellular activities by modulating multiple molecular targets, e.g. by binding to specific receptors and/or altering the structure and fluidity of lipid rafts. Therefore, the present review is devoted to novel bioactive glycerol-based lysophospholipids and recent findings concerning their functions and possible signaling pathways regulating physiological and pathological processes.

Serum metabolic profiling study of hepatocellular carcinoma infected with hepatitis B or hepatitis C virus by using liquid chromatography-mass spectrometry

The objective of the present study was to explore the common and specific metabolic alterations of hepatocellular carcinoma (HCC) infected with hepatitis B virus (HBV) or hepatitis C virus (HCV). Serum profiling data revealed that the two HCC groups shared a mainly similar metabolic profile, providing a basis for investigating their common tumor pathogenesis mechanism and early diagnosis biomarkers. Arachidonic acid as a pro-inflammatory precursor increased significantly in the HCC group compared to the cirrhosis and healthy control. And the lysophosphatidylcholines (lysoPCs) with polyunsaturated fatty acid acyl chain with potent anti-inflammatory activity significantly decreased in the HCC and cirrhosis groups compared to those in the healthy control group, which may partly contribute to maintaining chronic inflammation and benefit the initiation and progression of the malignant hepatic tumor. The decreased ratios of polyunsaturated lysoPCs to saturated lysoPCs in HCC groups compared to chronic liver diseases infected with HBV or HCV and healthy control further demonstrated that a malignant liver tumor exerts profound influences independent of virus infection. Especially, serum endocannabinoids anandamide (AEA) and palmitylethanolamide (PEA) were found significantly elevated in HCC groups compared to healthy control, and in HCC with HCV compared to corresponding chronic liver diseases. AEA, PEA, or their combination showed better sensitivity, specificity, and the area under the curve for distinguishing HCC from chronic liver diseases, showing they are potential biomarkers to distinguish the HCC from cirrhosis infected with HCV.