Elevated 18:0 lysophosphatidylcholine contributes to the development of pain in tissue injury

Plasma metabolites associated with endometriosis in adolescents and young adults

STUDY QUESTION

What are the plasma metabolomics profiles associated with endometriosis in adolescents and young adults?

SUMMARY ANSWER

Our findings show dysregulation of plasma metabolomic profiles in adolescents and young adults with endometriosis, revealing systemic elevation of fatty acyls and ceramides in endometriosis cases compared to controls.

WHAT IS KNOWN ALREADY

Endometriosis is a gynecologic disease often presenting with severe pelvic pain impacting around 200 million reproductive-aged women worldwide. However, little is known about the pathophysiology and molecular features of endometriosis diagnosed during adolescence and young adulthood.

STUDY DESIGN, SIZE, DURATION

We conducted a cross-sectional analysis including 190 laparoscopically confirmed endometriosis cases and 120 controls who participated in The Women's Health Study: From Adolescence to Adulthood, which enrolled participants from 2012 to 2018. Control participants were females without a diagnosis of endometriosis enrolled from the same clinics as the cases or recruited from the general population. Among the cases, 81 had blood samples collected before and after surgery.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Plasma metabolites were measured in blood collected at enrollment using liquid chromatography-tandem mass spectrometry, and a total of 430 known metabolites were evaluated in our analysis. We used linear regression adjusting for age at blood draw, BMI, hormone use, and fasting status at blood draw. Metabolite set enrichment analysis (MSEA) was used to identify metabolite classes. Number of effective tests (NEF) and false discovery rate (FDR) were used for multiple testing correction.

MAIN RESULTS AND THE ROLE OF CHANCE

The median age was 17 years for endometriosis cases and 22 years for controls. The majority of endometriosis cases had rASRM stage I or II (>95%). We identified 63 plasma metabolites associated with endometriosis (NEF < 0.05). Endometriosis cases had higher levels of plasma metabolites associated with proinflammatory response [e.g. eicosatrienoic acid (β = 0.61, 95% CI = 0.37, 0.86)], increased oxidative stress response [e.g. xanthine (β = 0.64, 95% CI = 0.39, 0.88)], and downregulation of metabolites related to apoptosis [glycocholic acid (β = -0.80, 95% CI = -1.04, -0.56)]. MSEA revealed increased fatty acyls (FDR = 2.3e-4) and ceramides (FDR = 6.0e-3) and decreased steroids and steroid derivatives (FDR = 1.3e-4) in endometriosis cases compared to controls. When we examined the changes in plasma metabolite profiles before and after surgery among endometriosis cases, 55 endometriosis-associated metabolites significantly changed from before to after surgery. MSEA revealed steroids and steroid derivatives (FDR = 8.1e-4) significantly increased after surgery, while fatty acyls (FDR = 1.2e-4) significantly decreased after surgery. Ceramides did not change from pre- to post-surgery and were elevated in post-surgical blood compared to controls (FDR = 3.9e-3).

LIMITATIONS, REASONS FOR CAUTION

Our study population mainly consists of self-reported non-Hispanic, white individuals and endometriosis cases with superficial peritoneal lesions only, so the generalizability may be limited. Furthermore, despite our large study population of adolescents and young adults with endometriosis, sample size was limited to conduct detailed stratified analyses of plasma metabolomic profiles, especially by post-surgical pelvic pain outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

Our study includes the utilization of state-of-the-art metabolomics technology with high reproducibility to comprehensively investigate the metabolites that were associated with endometriosis diagnosed in adolescents and young adults. Our results suggest a positive impact of endometriosis-related surgery for some, but not all, on systemic metabolic dysregulation in young patients with endometriosis. These results warrant further investigation on whether and how persistent systemic changes despite treatment may lead to long-term chronic disease risk among those diagnosed with endometriosis.

STUDY FUNDING/COMPETING INTEREST(S)

Financial support for establishment of and data collection within the A2A cohort was provided by the J. Willard and Alice S. Marriott Foundation, and support for assay costs was in part provided by the Peery family. This project was funded by Eunice Kennedy Shriver National Institute of Child Health and Human Development R21HD107266. S.A.M., A.L.S., and K.L.T. were supported by Eunice Kennedy Shriver National Institute of Child Health and Human Development R01HD094842. S.A.M. received grant funding from AbbVie, National Institutes of Health, Department of Defense, and Marriott Family Foundation; received honoraria from WERF, Huilun Shanghai, and University of Kansas Medical Center; travel support from SRI, ESHRE, FWGBD, University of Michigan, MIT, ASRM, LIDEA Registry, Taiwan Endometriosis Society, SEUD, Japan Endometriosis Society, NASEM, Endometriosis Foundation of America, Gedeon Richter Symposium at ESHRE; Board member receiving financial remuneration from AbbVie, Roche, LIDEA Registry, Editor of Frontiers in Reproductive Health, Roundtable participation for Abbott; Board member without financial remuneration from NextGen Jane and Statistical Advisory Board member of Human Reproduction; leadership role in Society for Women's Health Research, World Endometriosis Society, World Endometriosis Research Foundation, ASRM, ESHRE. N.S. and K.L.T. receive grant funding from Aspira Women's Health unrelated to this project. The remaining authors have no disclosures relevant to this manuscript.

TRIAL REGISTRATION NUMBER

N/A.

Metabolomics study of serum from patients with type 2 diabetes: Peripheral neuropathy could be associated with sphingosine and phospholipid molecules

Abnormal lipid metabolism is one of the risk factors for type 2 diabetes mellitus peripheral neuropathy (DPN). This study aimed to determine the differences in lipid metabolism in patients with type 2 diabetes and DPN and the possible pathogenesis caused by this difference. The participants comprised type 2 diabetes mellitus patients with DPN (N = 60) and healthy controls (N = 20). Blood samples were drawn from the participants in the morning in the fasting state, and then changes in serum lipids were explored using targeted metabolomics on the liquid chromatography-electrospray ionization-tandem mass spectrometry platform. Among the 1768 differentially abundant lipid metabolites, the results of orthogonal partial least squares-discriminant analysis combined with random forest analysis showed that the levels of sphingosine (SPH) (d18:0), carnitine 22:1, lysophosphatidylethanolamine (LPE) (18:0/0:0), LPC (16:0/0:0), lysophosphatidylcholine (LPC) (18:1/0:0), LPC (0:0/18:0) and LPE (0:0/18:1) were significantly different between the two groups. Spearman correlation analysis showed that SPH (d18:0), carnitine 22:1, LPE (18:0/0:0), and LPC (0:0/18:0) levels correlated highly with the patients' electromyography results. Kyoto Encyclopedia of Genes and Genomes pathway annotation and enrichment analysis of 538 differentially abundant lipid metabolites revealed that type 2 diabetes mellitus DPN was related to glycerophospholipid metabolism and glycerol metabolism. Our results further identified the dangerous lipid metabolites associated with DPN and abnormal lipid metabolism. The influence of lipid metabolites such as SPH and phospholipid molecules on DPN development in patients with type 2 diabetes mellitus were suggested and the possible pathogenic pathways were clarified, providing new insights into the clinical risk of DPN in patients with type 2 diabetes mellitus.

Functional determinants of lysophospholipid- and voltage-dependent regulation of TRPC5 channel

Lysophosphatidylcholine (LPC) is a bioactive lipid present at high concentrations in inflamed and injured tissues where it contributes to the initiation and maintenance of pain. One of its important molecular effectors is the transient receptor potential canonical 5 (TRPC5), but the explicit mechanism of the activation is unknown. Using electrophysiology, mutagenesis and molecular dynamics simulations, we show that LPC-induced activation of TRPC5 is modulated by xanthine ligands and depolarizing voltage, and involves conserved residues within the lateral fenestration of the pore domain. Replacement of W577 with alanine (W577A) rendered the channel insensitive to strong depolarizing voltage, but LPC still activated this mutant at highly depolarizing potentials. Substitution of G606 located directly opposite position 577 with tryptophan rescued the sensitivity of W577A to depolarization. Molecular simulations showed that depolarization widens the lower gate of the channel and this conformational change is prevented by the W577A mutation or removal of resident lipids. We propose a gating scheme in which depolarizing voltage and lipid-pore helix interactions act together to promote TRPC5 channel opening.

The same species, different nutrients: Lipidomics analysis of muscle in mud crabs (Scylla paramamosain) fed with lard oil and fish oil

Aiming to assess the effects of lard oil (LO) and fish oil (FO) on the nutritional value of mud crabs (Scylla paramamosain), non-targeted lipidomics analysis was performed on the muscle of crabs after eight weeks of feeding trail. Compared to FO, dietary LO reduced the content of phosphatidylethanolamine (PE) and phosphatidylserine (PS) with 18:0 bound at sn-1/3 site, the content of ether phospholipids containing 20:5n-3 (EPA) and 22:6n-3 (DHA) combined at sn-2 site, and increased the content of ether PE containing 18:0 and 18:1n-9. Furthermore, the deposition of 16:0, 16:1n-7, 18:2n-6, 18:3n-3, 20:4n-6, EPA and DHA at each site of PE, PS, phosphatidylcholine and/or triacylglycerols were reduced by dietary LO, while the DHA content at the sn-2 position of PE was increased. In conclusion, the nutritional value of mud crabs was reduced by dietary LO with the manifestation of variation in FA composition and positional distribution on phospholipids.

DODAB vesicles containing lysophosphatidylcholines: The relevance of acyl chain saturation on the membrane structure and thermal properties

The saturated LPC18:0 and unsaturated LPC18:1 lysophosphatidylcholines have important roles in inflammation and immunity and are interesting targets for immunotherapy. The synthetic cationic lipid DODAB has been successfully employed in delivery systems, and would be a suitable carrier for those lysophosphatidylcholines. Here, assemblies of DODAB and LPC18:0 or LPC18:1 were characterized by Differential Scanning Calorimetry (DSC) and Electron Paramagnetic Resonance (EPR) spectroscopy. LPC18:0 increased the DODAB gel-fluid transition enthalpy and rigidified both phases. In contrast, LPC18:1 caused a decrease in the DODAB gel-fluid transition temperature and cooperativity, associated with two populations with distinct rigidities in the gel phase. In the fluid phase, LPC18:1 increased the surface order but, differently from LPC18:0, did not affect viscosity at the membrane core. The impact of the different acyl chains of LPC18:0 and 18:1 on structure and thermotropic behavior should be considered when developing applications using mixed DODAB membranes.