Lysophospholipids

Pancreatic cancer has the worst prognosis among all cancers. Cancer screening of body fluids may improve the survival time prognosis of patients, who are often diagnosed too late at an incurable stage. Several studies report the dysregulation of lipid metabolism in tumor cells, suggesting that changes in the blood lipidome may accompany tumor growth. Here we show that the comprehensive mass spectrometric determination of a wide range of serum lipids reveals statistically significant differences between pancreatic cancer patients and healthy controls, as visualized by multivariate data analysis. Three phases of biomarker discovery research (discovery, qualification, and verification) are applied for 830 samples in total, which shows the dysregulation of some very long chain sphingomyelins, ceramides, and (lyso)phosphatidylcholines. The sensitivity and specificity to diagnose pancreatic cancer are over 90%, which outperforms CA 19-9, especially at an early stage, and is comparable to established diagnostic imaging methods. Furthermore, selected lipid species indicate a potential as prognostic biomarkers.

The diversity of glycerophospholipid species in cellular membranes is immense and affects various biological functions. Glycerol-3-phosphate acyltransferases (GPATs) and lysophospholipid acyltransferases (LPLATs), in concert with phospholipase A1/2s enzymes, contribute to this diversity via selective esterification of fatty acyl chains at the sn-1 or sn-2 positions of membrane phospholipids. These enzymes are conserved across all kingdoms, and in mammals four GPATs of the 1-acylglycerol-3-phosphate O-acyltransferase (AGPAT) family and at least 14 LPLATs, either of the AGPAT or the membrane-bound O-acyltransferase (MBOAT) families, have been identified. Here we provide an overview of the biochemical and biological activities of these mammalian enzymes, including their predicted structures, involvements in human diseases, and essential physiological roles as revealed by gene-deficient mice. Recently, the nomenclature used to refer to these enzymes has generated some confusion due to the use of multiple names to refer to the same enzyme and instances of the same name being used to refer to completely different enzymes. Thus, this review proposes a more uniform LPLAT enzyme nomenclature, as well as providing an update of recent advances made in the study of LPLATs, continuing from our JBC mini review in 2009.

The physiological functions of lysophosphatidylethanolamine (lysoPE) have not been fully elucidated. In this study, the effects of lysoPE on lipogenesis and lipolysis were investigated in a cultured human liver-derived cell line. The intracellular lipid profile was investigated in detail using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to better understand the underlying mechanism. The expression of genes related to lipid metabolism and catabolism was analyzed using real-time PCR. LysoPE supplementation induced cellular lipid droplet formation and altered triacylglycerol (TAG) profiles. Furthermore, lysoPE downregulated expression of the TAG hydrolyzation regulation factor ATGL, and reduced the expression of fatty acid biosynthesis-related genes SREBP1 and SCD1. LC-MS/MS-based lipidomic profiling revealed that the addition of lysoPE 18:2 increased the PE species containing linoleic acyl, as well as the CE 18:2 species, likely due to the incorporation of linoleic acyl from lysoPE 18:2. Collectively, these findings suggest that lysoPE 18:2 is involved in lipid droplet formation by suppressing lipolysis and fatty acid biosynthesis. Thus, lysoPE might play a pathological role in the induction of fatty liver disease.

BackgroundDysregulation of lysophosphatidylcholines (LPCs) and phosphatidylcholines (PCs) is linked to endothelial dysfunction and impaired tissue repair. Nevertheless, the organ-specific modulation of lysolecithin remodeling in T2DM remains unexplored. Here, we investigate the LPC/PC remodeling dynamics in a T2DM model and propose a novel therapeutic approach using an orally bioavailable peptide (SP6) derived from Spirulina platensis.MethodsLPC/PC levels were analyzed by UHPLC-HRMS. Membrane fluidity, VEGF/API5, LPCAT1, VE-cadherin, and GLUT1 were evaluated by merocyanine assay, qPCR, immunoblotting, and immunofluorescence. In vivo, T2DM was induced by a high-fat diet and streptozotocin, and SP6 was orally administered. Tissue lipidomics, GLUTs expression, and insulin secretion were assessed, with the latter also spatially characterized in pancreatic tissue by MALDI-MS imaging.ResultsHigh glucose induced LPC/PC imbalance, enhanced membrane fluidity, impaired VEGF/API5 expression, and hindered wound healing and VE-cadherin localization via LPCAT1 downregulation and subsequent impact on GLUT1 translocation. In vivo analysis of diabetic mice revealed a multi-organ influence of SP6 preserving LPCAT1 mRNA levels in pancreas, liver, skeletal muscle, and adipose tissue and a specific pattern of lysolecithin remodeling, with selective modulation of LPC 16:0, 18:0, and 20:4 in plasma. Finally, its effects in T2DM are mediated by preserving insulin secretion and glycemic control through increased ATP production.ConclusionThese findings reveal tissue-specific lysolecithin reprogramming in T2DM development and identify LPCAT1-mediated lysolecithin remodeling as a mechanism involved in T2DM-related endothelial and metabolic dysfunction. SP6 modulates lipid metabolism, vascular integrity, and glucose regulation at the transcript level, suggesting its potential as a new preventive treatment for T2DM and its complications.