Lipid-gene regulatory network reveals coregulations of triacylglycerol with phosphatidylinositol/lysophosphatidylinositol and with hexosyl-ceramide

KRAS Affects the Lipid Composition by Regulating Mitochondrial Functions and MAPK Activation in Bovine Mammary Epithelial Cells

Kirsten rat sarcoma viral oncogene homolog (KRAS), or guanosine triphosphatase KRAS, is a proto-oncogene that encodes the small guanosine triphosphatase transductor protein. Previous studies have found that KRAS can promote cytokine secretion, cell chemotaxis, and survival. However, its effects on milk fat synthesis in bovine mammary epithelial cells are unclear. In this study, the effects of KRAS inhibition on cell metabolism, autophagy, oxidative stress, endoplasmic reticulum stress, mitochondrial function, and lipid composition as well as the potential mechanisms were detected in an immortalized dairy cow mammary epithelial cell line (MAC-T). The results showed that inhibition of KRAS changed the lipid composition (especially the triglyceride level), mitochondrial functions, autophagy, and endoplasmic reticulum stress in cells. Moreover, KRAS inhibition regulated the levels of the mammalian target of rapamycin and mitogen-activated protein kinase (extracellular regulated protein kinases, c-Jun N-terminal kinases, p38) activation. These results indicated that regulation of KRAS would affect the synthesis and composition of milk fat. These results are also helpful for exploring the synthesis and secretion of milk fat at the molecular level and provide a theoretical basis for improving the percentage of fat in milk and the yield of milk from cows.

Mass spectrometry imaging of mice brain lipid profile changes over time under high fat diet

Overweight and obesity have been shown to significantly affect brain structures and size. Obesity has been associated with cerebral atrophy, alteration of brain functions, including cognitive impairement, and psychiatric diseases such as depression. Given the importance of lipids in the structure of the brain, here, by using 47 mice fed a high fat diet (HFD) with 60% calories from fat (40% saturated fatty acids) and 20% calories from carbohydrates and age-matched control animals on a normal chow diet, we examined the effects of HFD and diet-induced obesity on the brain lipidome. Using a targeted liquid chromatography mass spectrometry analysis and a non-targeted mass spectrometry MALDI imaging approach, we show that the relative concentration of most lipids, in particular brain phospholipids, is modified by diet-induced obesity (+ 40%of body weight). Use of a non-targeted MALDI-MS imaging approach further allowed define cerebral regions of interest (ROI) involved in eating behavior and changes in their lipid profile. Principal component analysis (PCA) of the obese/chow lipidome revealed persistence of some of the changes in the brain lipidome of obese animals even after their switch to chow feeding and associated weight loss. Altogether, these data reveal that HFD feeding rapidly modifies the murine brain lipidome. Some of these HFD-induced changes persist even after weight loss, implying that some brain sequelae caused by diet-induced obesity are irreversible.

Non-targeted lipidomics and transcriptomics analysis reveal the molecular underpinnings of mandibular gland development in Apis mellifera ligustica

The mandibular gland is an important exocrine gland of worker bees, which mainly secretes fatty acids and pheromones. Lipids have important roles in energy storage, membrane structure stabilization, and signaling. However, molecular underpinnings of mandibular gland development and lipid remodeling at the different physiological stages of worker bees is still lacking. In this study, we used scanning and transmission electron microscopy to reveal the morphological changes in secretory cells, and liquid chromatography-mass spectrometry and RNA-seq to investigate the lipidome and gene transcripts during development. The morphology of secretory cells was flat in newly emerged workers, becoming vacuolated and turgid when they were activated in nurse bees and foragers. Transport vesicles became denser from newly emerged bees to 21-day worker bees. Concentrations of 10-HDA reached a maximum within 15d workers and changes in genes expression were consistent with 10-HDA content. Non-targeted lipidomics analysis of newly emerged, 6d, and 15d worker bees revealed that PC and TAG were the main lipids in mandibular gland, and lipids dramatically altered across developmental stages. TAG 54:4 was increased most strongly at 6d and 15d worker bees, meanwhile, the abundances of TAG 54:1 and TAG 54:2 were decreased sharply. Further, transcriptomics analysis showed that differentially expressed genes were significantly enriched in key nutrient metabolic pathways, particularly lipid metabolism, in 6d and 15d bees. This multi-omic perspective provides a unique resource and deeper insight into bee mandibular gland development and baseline data for further study of the mandibular gland in worker bees.

High-coverage targeted lipidomics revealed dramatic lipid compositional changes in asthenozoospermic spermatozoa and inverse correlation of ganglioside GM3 with sperm motility

BACKGROUND

It has been previously demonstrated that cholesterol content and cholesterol/phospholipid ratio were significantly higher in asthenozoospermia and oligoasthenoteratozoospermia. The majority of published studies have investigated the fatty acid composition of phospholipids rather than lipids themselves. This study evaluated the lipid composition of asthenozoospermic and normozoospermic spermatozoa, and identified the exact lipid species that correlated with sperm motility.

METHODS

A total of 12 infertile asthenozoospermia patients and 12 normozoospermia subjects with normal sperm motility values were tested for semen volume, sperm concentration, count, motility, vitality and morphology. High-coverage targeted lipidomics with 25 individual lipid classes was performed to analyze the sperm lipid components and establish the exact lipid species that correlated with sperm motility.

RESULTS

A total of 25 individual lipid classes and 479 lipid molecular species were identified and quantified. Asthenozoospermic spermatozoa showed an increase in the level of four lipid classes, including Cho, PE, LPI and GM3. A total of 48 lipid molecular species were significantly altered between normozoospermic and asthenozoospermic spermatozoa. Furthermore, the levels of total GM3 and six GM3 molecular species, which were altered in normozoospermic spermatozoa versus asthenozoospermic spermatozoa, were inversely correlated with sperm progressive and total motility.

CONCLUSIONS

Several unique lipid classes and lipid molecular species were significantly altered between asthenozoospermic and normozoospermic spermatozoa, revealing new possibilities for further mechanistic pursuits and highlighting the development needs of culture medium formulations to improve sperm motility.

Sex-dependent effects of ambient PM2.5 pollution on insulin sensitivity and hepatic lipid metabolism in mice

Background & aims

Emerging evidence supports ambient fine particulate matter (PM_2.5) exposure is associated with insulin resistance (IR) and hepatic lipid accumulation. In this study, we aimed to evaluate the sex-dependent vulnerability in response to PM_2.5 exposure and investigate the underlying mechanism by which PM_2.5 modulates hepatic lipid metabolism.

Methods

Both male and female C57BL/6 mice were randomly assigned to ambient PM_2.5 or filtered air for 24 weeks via a whole body exposure system. High-coverage quantitative lipidomics approaches and liquid chromatography-mass spectrometry techniques were performed to measure hepatic metabolites and hormones in plasma. Metabolic studies, histological analyses, as well as gene expression levels and molecular signal transduction analysis were applied to examine the effects and mechanisms by which PM_2.5 exposure-induced metabolic disorder.

Results

Female mice were more susceptible than their male counterparts to ambient PM_2.5 exposure-induced IR and hepatic lipid accumulation. The hepatic lipid profile was changed in response to ambient PM_2.5 exposure. Levels of hepatic triacylglycerols (TAGs), free fatty acids (FFAs) and cholesterol were only increased in female mice from PM group compared to control group. Plasmalogens were dysregulated in the liver from PM_2.5-exposed mice as well. In addition, exposure to PM_2.5 led to enhanced hepatic ApoB and microsomal triglyceride transport protein expression in female mice. Finally, PM_2.5 exposure inhibited hypothalamus-pituitary-adrenal (HPA) axis and decreased glucocorticoids levels, which may contribute to the vulnerability in PM_2.5-induced metabolic dysfunction.

Conclusions

Ambient PM_2.5 exposure inhibited HPA axis and demonstrated sex-associated differences in its effects on IR and disorder of hepatic lipid metabolism. These findings provide new mechanistic evidence of hormone regulation in air pollution-mediated metabolic abnormalities of lipids and more personalized care should be considered in terms of sex-specific risk factors.

Mycobacterium tuberculosis strains of the modern Beijing sublineage excessively accumulate triacylglycerols in vitro

Mycobacterium tuberculosis (Mtb) strains of modern Beijing sublineage appear to be more transmissible and cause more severe disease than strains of other sublineages, but the responsible pathogenic mechanisms remain unclear. We previously identified genetic changes that are specific for the modern Beijing sublineage, and here we characterize the lipidome and transcriptome differences between modern and ancient Beijing sublineages. We report that modern Beijing strains accumulated 2.89 (95%CI: 2.05-3.73) times more triacylglycerol (TAG) than ancient Beijing strains in vitro. We also observed that modern Beijing strains had a 2.64-fold (95%CI: 1.29-4.00) upregulation of tgs2 (annotated as TAG synthetase 2), whose role in TAG accumulation was further confirmed in Mycobacterium marinum (Mm). Because TAG serves as a crucial carbon source and reservoir of free fatty acids, the results suggest that the excessive accumulation of TAG might fuel the growth of modern Beijing strains after infection and lead to rapid development of disease.

Surfactant Lipidomics of Alveolar Lavage Fluid in Mice Based on Ultra-High-Performance Liquid Chromatography Coupled to Hybrid Quadrupole-Exactive Orbitrap Mass Spectrometry

Surfactant lipid metabolism is closely related to pulmonary diseases. Lipid metabolism disorder can cause lung diseases, vice versa. With this rationale, a useful method was established in this study to determine the lipidome in bronchoalveolar lavage fluid (BALF) of mice. The lipid components in BALF were extracted by liquid-liquid extraction (methanol and methyl tert-butyl ether, and water). Ultra-high-performance liquid chromatography coupled to hybrid Quadrupole-Exactive Orbitrap mass spectrometry was used to analyze the extracted samples, which showed a broad scanning range of 215-1800 m/z. With MS-DIAL software and built-in LipidBlast database, we identified 38 lipids in positive, and 31 lipids in negative, ion mode, including lysophosphatidylcholine (lysoPC), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), etc. Then, the changes of lipids in BALF of mice with acute lung injury (ALI) induced by lipopolysaccharide (LPS) was investigated, which may contribute to further exploration of the pathogenesis of ALI.