Evaluation of nonpolar lipid extract antigen-based enzyme-linked immunosorbent assay for the serodiagnosis of tuberculosis.

This study assessed the diagnostic potential of nonpolar lipid extracts in enzyme-linked immunosorbent assays (ELISAs) for tuberculosis (TB) serodiagnosis. Nonpolar lipid extracts were harvested from Mycobacterium tuberculosis (Mtb) knockout in mce1 operon (∆mce1) and its parental wild type (WT) strains. IgM and IgG anti-nonpolar lipid serum levels were measured in TB patients (n=45), healthy individuals with positive (n=22) and negative (n=44) interferon-gamma release assay (IGRA) results, and symptomatic respiratory (SR) patients with negative TB tests (n=9). IgG anti-WT lipid distinguished TB patients from IGRA-positive individuals with 60% sensitivity and 77.3% specificity. Conversely, IgG anti-∆mce lipid levels didn't vary significantly across groups. Interestingly, most SR patients exhibited significantly higher IgM and IgG anti-WT lipid titers than the IGRA-positive and -nega groups. While the overall diagnostic potential of Mtb nonpolar lipids was limited, the impaired immunogenecity of Δmce1 lipid extract suggests that some missing lipid classes in this extract can potentially induce antibody production in TB patients.

Contribution of Lipids to the Flavor of Mussel (Mytilus edulis) Maillard Reaction Products.

Lipid oxidation and the Maillard reaction are two of the most important reactions affecting the flavor of foods that have been heat-processed. To investigate the contribution of lipids to the mussel's flavor, the mussel's Maillard reaction products (MRPs) were prepared with polar lipids (mainly phospholipids) and nonpolar lipids (mainly glycerides), respectively. The effects of polar and nonpolar lipids on the flavor of the MRPs were investigated by sensory evaluation, electronic tongue, electronic nose, ultra-performance liquid chromatography-mass-spectrometry (UPLC-MS) and gas chromatography-mass-spectrometry (GC-MS). From the sensory evaluation results, the polar lipid MRPs had the highest scores. The tastes of polar lipid MRPs and nonpolar lipid MRPs were mainly umami, saltiness and sourness, and there were significant differences in their sour tastes. The flavor compounds in the MRPs were mainly inorganic sulfides, organic sulfides and nitrogen oxides. The odor of polar lipid MRPs was stronger than that of nonpolar lipid MRPs, and the seafood flavor was more obvious. A total of 37 volatile compounds were detected by GC-MS, mainly aldehydes, alcohols and ketones. The addition of polar lipids helped the MRPs to produce more volatile compounds. A total of 177 non-volatile compounds (including amino acids and their derivatives and oligopeptides, etc.) were detected in the samples using UPLC-MS. The non-volatile compounds contained in the no-lipid MRPs, polar lipid MRPs and nonpolar lipid MRPs were significantly different. This study provides a theoretical basis and technical support for the production of mussel MRPs.

Direct Infusion Mass Spectrometry for Complex Lipid Analysis.

Direct infusion or "shotgun" mass spectrometry provides a fast strategy to measure different classes of lipids, combining rapid analysis and short idle time. In contrast to liquid chromatography-mass spectrometry (LC-MS), the lipids are infused into the mass spectrometer without prior separation by liquid chromatography. Ions are separated in the quadrupole of a tandem mass spectrometer, and after collision-induced dissociation fragments are quantified relative to internal standards in the third quadrupole or in the time-of-flight mass analyzer of a triple quadrupole or quadrupole time of flight (Q-TOF) mass spectrometer. Abundant lipids, that is, galactolipids and phospholipids in leaves, are measured in crude lipid extracts, while less abundant lipids can be measured after enrichment by solid-phase extraction. Here we describe protocols for the quantification of the major plant glycerolipids (galactolipids, phospholipids, diacylglycerol, and triacylglycerol) using nanospray direct infusion mass spectrometry. This provides a strategy for comprehensive, highly sensitive, high-throughput lipidomic analyses.

Effect of zinc deprivation on the lipid metabolism of budding yeast.

Zinc is an essential micronutrient for all living cells. It serves as a structural and catalytic cofactor for numerous proteins, hence maintaining a proper level of cellular zinc is essential for normal functioning of the cell. Zinc homeostasis is sustained through various ways under severe zinc-deficient conditions. Zinc-dependent proteins play an important role in biological systems and limitation of zinc causes a drastic change in their expression. In budding yeast, a zinc-responsive transcription factor Zap1p controls the expression of genes required for uptake and mobilization of zinc under zinc-limiting conditions. It also regulates the polar lipid levels under zinc-limiting conditions to maintain membrane integrity. Deletion of ZAP1 causes an increase in triacylglyerol levels which is due to the increased biosynthesis of acetate that serves as a precursor for triacylglycerol biosynthesis. In this review, we expanded our recent work role of Zap1p in nonpolar lipid metabolism of budding yeast.

Analysis of yeast lipid droplet proteome and lipidome.

Lipid droplets (LD) are in the spotlight of lipid research because of the link of lipid storage to health and disease and the just incipient understanding of their involvement in cellular processes apart from nonpolar lipid metabolism. Yeast is an excellent model organism to study the lipidome and proteome of LD under different environmental conditions and to address new aspects of LD biology and chemistry. In this chapter, we describe a versatile protocol for the isolation of LD at high purity and address specific demands for handling different yeast species. Moreover, we discuss the analysis of the LD proteome and lipidome based on standard methods such as thin layer chromatography (TLC), gas liquid chromatography (GLC), mass spectrometry (MS) as well as GLC/MS. Finally, we point out similarities and disparities of LD proteome and lipidome from the three different yeasts Saccharomyces cerevisiae, Yarrowia lipolytica, and Pichia pastoris.

Ambient temperature and nutritional stress influence fatty acid composition of structural and fuel lipids in Japanese quail (Coturnix japonica) tissues.

In birds, fatty acids (FA) serve as the primary metabolic fuel during exercise and fasting, and their composition affects metabolic rate and thus energy requirements. To ascertain the relationship between FAs and metabolic rate, a distinction should be made between structural and fuel lipids. Indeed, increased unsaturation of structural lipid FAs brings about increased cell metabolism, and changes in the FA composition of fuel lipids affects metabolic rate through selective mobilization and increasing availability of specific FAs. We examined the effects of acclimation to a low ambient temperature (Ta: 12.7±3.0°C) and nutritional status (fed or unfed) on the FA composition of four tissues in Japanese quail, Coturnix japonica. Differentiating between neutral (triglycerides) and polar (phospholipids) lipids, we tested the hypothesis that both acclimation to low Ta and nutritional status modify FA composition of triglycerides and phospholipids. We found that both factors affect FA composition of triglycerides, but not the composition of phospholipids. We also found changes in liver triacylglyceride FA composition in the low-Ta acclimated quail, namely, the two FAs that differed, oleic acid (18:1) and arachidonic acid (20:4), were associated with thermoregulation. In addition, the FAs that changed with nutritional status were all reported to be involved in regulation of glucose metabolism, and thus we suggest that they also play a role in the response to fasting.