Quantitative lipidomics reveals age-dependent perturbations of whole-body lipid metabolism in ACBP deficient mice

Regulation of Milk Fat Synthesis: Key Genes and Microbial Functions

Milk is rich in a variety of essential nutrients, including fats, proteins, and trace elements that are important for human health. In particular, milk fat has an alleviating effect on diseases such as heart disease and diabetes. Fatty acids, the basic units of milk fat, play an important role in many biological reactions in the body, including the involvement of glycerophospholipids and sphingolipids in the formation of cell membranes. However, milk fat synthesis is a complex biological process involving multiple organs and tissues, and how to improve milk fat of dairy cows has been a hot research issue in the industry. There exists a close relationship between milk fat synthesis, genes, and microbial functions, as a result of the organic integration between the different tissues of the cow's organism and the external environment. This review paper aims (1) to highlight the synthesis and regulation of milk fat by the first and second genomes (gastrointestinal microbial genome) and (2) to discuss the effects of ruminal microorganisms and host metabolites on milk fat synthesis. Through exploring the interactions between the first and second genomes, and discovering the relationship between microbial and host metabolite in the milk fat synthesis pathway, it may become a new direction for future research on the mechanism of milk fat synthesis in dairy cows.

Two typical acyl-CoA-binding proteins (ACBPs) are required for the asexual development and virulence of Phytophthora sojae

Being found in all eukaryotes investigated, acyl-CoA-binding proteins (ACBPs) participate in lipid metabolism via specifically binding acyl-CoA esters with high affinity. The structures and functions of ACBP family proteins have been extensively described in yeasts, fungi, plants and mammals, but not oomycetes. In the present study, seven ACBP genes named PsACBP1-7 were identified from the genome of Phytophthora sojae, an oomycete pathogen of soybean. CRISPR-Cas9 knockout mutants targeting PsACBP1 and PsACBP2 were created for phenotypic assays. PsACBP1 knockout led to defects in sporangia production and virulence. PsACBP2 knockout mutants exhibited impaired vegetative growth, zoospore production, cyst germination and virulence. Moreover, Nile red staining of PsACBP2 knockout and over-expression lines showed that PsACBP2 is involved in the formation of lipid bodies in P. sojae. Our results demonstrate that two ACBP genes are differently required for growth and development, and both are essential for virulence in P. sojae.

Fat Deposition in the Muscle of Female and Male Yak and the Correlation of Yak Meat Quality with Fat

This study aimed to explore the differences in fat deposition between female (FYs) and male yaks (MYs). Compared with MYs, the tenderness, L*, marbling, absolute content of fat, and most fatty acids (FAs) of longissimus dorsi (LD) in FYs were higher or better (p < 0.05), whereas the relative content of polyunsaturated fatty acids (PUFAs) and n-3 PUFAs were lower (p < 0.01). The absolute content of fat, C18:0, cis-C18:2, cis-C18:1, and C24:0 were positively correlated with L*_{45 min}, b*_{24 h}, tenderness, and marbling score of LD in FYs and MYs (p < 0.05), respectively. LPL, FATP2, ELOVL6, HADH, HACD, and PLINS genes play a crucial role in improving the marbling score and tenderness of yak meat. The results of gene expression and protein synthesis showed the effect of gender to FA biosynthesis, FA transport, lipolysis, and FA oxidation in the adipose tissue of yak was realized by the expressions of ME1, SCD, ACSL5, LPL, FABP1, PLIN4, and PLIN2 in peroxisome proliferators-activated receptor (PPAR) signaling. This study established a theoretical basis for the improvement of the meat quality of yak and molecular breeding.

Lipid molecular timeline profiling reveals diurnal crosstalk between the liver and circulation

Diurnal regulation of whole-body lipid metabolism plays a vital role in metabolic health. Although changes in lipid levels across the diurnal cycle have been investigated, the system-wide molecular responses to both short-acting fasting-feeding transitions and longer-timescale circadian rhythms have not been explored in parallel. Here, we perform time-series multi-omics analyses of liver and plasma revealing that the majority of molecular oscillations are entrained by adaptations to fasting, food intake, and the postprandial state. By developing algorithms for lipid structure enrichment analysis and lipid molecular crosstalk between tissues, we find that the hepatic phosphatidylethanolamine (PE) methylation pathway is diurnally regulated, giving rise to two pools of oscillating phosphatidylcholine (PC) molecules in the circulation, which are coupled to secretion of either very low-density lipoprotein (VLDL) or high-density lipoprotein (HDL) particles. Our work demonstrates that lipid molecular timeline profiling across tissues is key to disentangling complex metabolic processes and provides a critical resource for the study of whole-body lipid metabolism.

Advances in Understanding the Acyl-CoA-Binding Protein in Plants, Mammals, Yeast, and Filamentous Fungi

Acyl-CoA-binding protein (ACBP) is an important protein with a size of about 10 kDa. It has a high binding affinity for C12-C22 acyl-CoA esters and participates in lipid metabolism. ACBP and its family of proteins have been found in all eukaryotes and some prokaryotes. Studies have described the function and structure of ACBP family proteins in mammals (such as humans and mice), plants (such as Oryza sativa, Arabidopsis thaliana, and Hevea brasiliensis) and yeast. However, little information on the structure and function of the proteins in filamentous fungi has been reported. This article concentrates on recent advances in the research of the ACBP family proteins in plants and mammals, especially in yeast, filamentous fungi (such as Monascus ruber and Aspergillus oryzae), and fungal pathogens (Aspergillus flavus, Cryptococcus neoformans). Furthermore, we discuss some problems in the field, summarize the binding characteristics of the ACBP family proteins in filamentous fungi and yeast, and consider the future of ACBP development.

Total Fatty Acid Analysis of Human Blood Samples in One Minute by High-Resolution Mass Spectrometry

Total fatty acid analysis is a routine method in many areas, including lipotyping of individuals in personalized medicine, analysis of foodstuffs, and optimization of oil production in biotechnology. This analysis is commonly done by converting fatty acyl (FA) chains of intact lipids into FA methyl esters (FAMEs) and monitoring these by gas-chromatography (GC)-based methods, typically requiring at least 15 min of analysis per sample. Here, we describe a novel method that supports fast, precise and accurate absolute quantification of total FA levels in human plasma and serum samples. The method uses acid-catalyzed transesterification with ¹⁸O-enriched H₂O (i.e., H₂¹⁸O) to convert FA chains into ¹⁸O-labeled free fatty acids. The resulting “mass-tagged” FA analytes can be specifically monitored with improved signal-to-background by 1 min of high resolution Fourier transform mass spectrometry (FTMS) on an Orbitrap-based mass spectrometer. By benchmarking to National Institute of Standards and Technology (NIST) certified standard reference materials we show that the performance of our method is comparable, and at times superior, to that of gold-standard GC-based methods. In addition, we demonstrate that the method supports the accurate quantification of FA differences in samples obtained in dietary intervention studies and also affords specific monitoring of ingested stable isotope-labeled fatty acids (¹³C₁₆-palmitate) in normoinsulinemic and hyperinsulinemic human subjects. Overall, our novel high-throughput method is generic and suitable for many application areas, spanning basic research to personalized medicine, and is particularly useful for laboratories equipped with high resolution mass spectrometers, but lacking access to GC-based instrumentation.

Lipidomics unveils the complexity of the lipidome in metabolic diseases

Dysregulation of lipid metabolism is responsible for pathologies of human diseases including metabolic diseases. Recent advances in lipidomics analysis allow for the targeted and untargeted identification of lipid species and for their quantification in normal and diseased conditions. Herein, this review provides a brief introduction to lipidomics, highlights its application to characterize the lipidome at the cellular and physiological levels under different biological conditions, and discusses the potential for the use of lipidomics in the discovery of biomarkers.

Easy, Fast, and Reproducible Quantification of Cholesterol and Other Lipids in Human Plasma by Combined High Resolution MSX and FTMS Analysis

Reliable, cost-effective, and gold-standard absolute quantification of non-esterified cholesterol in human plasma is of paramount importance in clinical lipidomics and for the monitoring of metabolic health. Here, we compared the performance of three mass spectrometric approaches available for direct detection and quantification of cholesterol in extracts of human plasma. These approaches are high resolution full scan Fourier transform mass spectrometry (FTMS) analysis, parallel reaction monitoring (PRM), and novel multiplexed MS/MS (MSX) technology, where fragments from selected precursor ions are detected simultaneously. Evaluating the performance of these approaches in terms of dynamic quantification range, linearity, and analytical precision showed that the MSX-based approach is superior to that of the FTMS and PRM-based approaches. To further show the efficacy of this approach, we devised a simple routine for extensive plasma lipidome characterization using only 8 μL of plasma, using a new commercially available ready-to-spike-in mixture with 14 synthetic lipid standards, and executing a single 6 min sample injection with combined MSX analysis for cholesterol quantification and FTMS analysis for quantification of sterol esters, glycerolipids, glycerophospholipids, and sphingolipids. Using this simple routine afforded reproducible and absolute quantification of 200 lipid species encompassing 13 lipid classes in human plasma samples. Notably, the analysis time of this procedure can be shortened for high throughput-oriented clinical lipidomics studies or extended with more advanced MS^ALL technology (Almeida R. et al., J. Am. Soc. Mass Spectrom. 26, 133-148 [1]) to support in-depth structural elucidation of lipid molecules. Graphical Abstract ᅟ.

Proposal for a common nomenclature for fragment ions in mass spectra of lipids

Advances in mass spectrometry-based lipidomics have in recent years prompted efforts to standardize the annotation of the vast number of lipid molecules that can be detected in biological systems. These efforts have focused on cataloguing, naming and drawing chemical structures of intact lipid molecules, but have provided no guidelines for annotation of lipid fragment ions detected using tandem and multi-stage mass spectrometry, albeit these fragment ions are mandatory for structural elucidation and high confidence lipid identification, especially in high throughput lipidomics workflows. Here we propose a nomenclature for the annotation of lipid fragment ions, describe its implementation and present a freely available web application, termed ALEX123 lipid calculator, that can be used to query a comprehensive database featuring curated lipid fragmentation information for more than 430,000 potential lipid molecules from 47 lipid classes covering five lipid categories. We note that the nomenclature is generic, extendable to stable isotope-labeled lipid molecules and applicable to automated annotation of fragment ions detected by most contemporary lipidomics platforms, including LC-MS/MS-based routines.

Reporting of lipidomics data should be standardized

This article highlights, to our opinion, some of the most pertinent issues related to producing high quality lipidomics data. These issues include pitfalls related to sample collection and storage, lipid extraction, the use of shotgun and LC-MS-based lipidomics approaches, and the identification, annotation and quantification of lipid species. We hope that highlighting these issues will help stimulate efforts to implement reporting standards for dissemination of lipidomics data. This article is part of a Special Issue entitled: BBALIP_Lipidomics Opinion Articles edited by Sepp Kohlwein.