Journal of Lipid Research最新文献

Plasma membrane (PM) domains and order phases have been shown to play a key role in the assembly, release, and entry of several lipid-enveloped viruses. In the present study, we provide a mechanistic understanding of the Ebola virus (EBOV) matrix protein VP40 interaction with PM lipids and their effect on VP40 oligomerization, a crucial step for viral assembly and budding. VP40 matrix formation is sufficient to induce changes in the PM fluidity. We demonstrate that the distance between the lipid headgroups, the fatty acid tail saturation, and the PM order are important factors for the stability of VP40 binding and oligomerization at the PM. The use of FDA-approved drugs to fluidize the PM destabilizes the viral matrix assembly leading to a reduction in budding efficiency. Overall, these findings support an EBOV assembly mechanism that reaches beyond lipid headgroup specificity by using ordered PM lipid regions independent of cholesterol.

Liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS)-based methods have become the gold standard methodology for the comprehensive profiling of the human plasma lipidome. However, both the complexity of lipid chemistry and LC-HRMS-associated data pose challenges to the characterization of this biological matrix. In accordance with the current consensus of quality requirements for LC-HRMS lipidomics data, we aimed to characterize the NIST® Standard Reference Material for Human Plasma (SRM 1950) using an LC-ESI(+/-)-MS method compatible with high-throughput lipidome profiling. We generated a highly curated lipid database with increased coverage, quality, and consistency, including additional quality assurance procedures involving adduct formation, within-method m/z evaluation, retention behavior of species within lipid chain isomers, and expert-driven resolution of isomeric and isobaric interferences. As a proof-of-concept, we showed the utility of our in-house LC-MS lipidomic database -consisting of 592 lipid entries- for the fast, comprehensive, and reliable lipidomic profiling of the human plasma from healthy human volunteers. We are confident that the implementation of this robust resource and methodology will have a significant impact by reducing data redundancy and the current delays and bottlenecks in untargeted plasma lipidomic studies.

Membrane-associated ring-CH-type finger 6 (MARCH6), also designated as TEB4 or RNF176, is an E3 ligase that is embedded in membranes of the endoplasmic reticulum where it ubiquitinates many substrate proteins to consign them to proteasome-mediated degradation. In recent years, MARCH6 has been identified as a key regulator of several metabolic pathways, including cholesterol and lipid droplet homeostasis, protein quality control, ferroptosis, and tumorigenesis. Despite its importance, there are currently no specific antibodies to detect and monitor MARCH6 levels in cultured cells and animals. Here, we address this deficiency by generating a monoclonal antibody that specifically detects MARCH6 in cultured cells of insect, mouse, hamster, and human origin, as well as in mouse tissues, with minimal cross-reactivity against other proteins. We then used this antibody to assess two properties of MARCH6. First, analysis of mouse tissues with this antibody revealed that the liver contained the highest levels of March6. Second, analysis of five different cell lines with this antibody showed that endogenous levels of MARCH6 are unchanged as the cellular content of cholesterol is varied. This reagent promises to be a useful tool in interrogating additional signaling roles of MARCH6.

Hepatocellular carcinoma (HCC) poses significant treatment challenges due to high postoperative recurrence rates and the limited effectiveness of targeted medications. Researchers have identified the unique metabolic profiles of cancer stem cells (CSCs) as the primary drivers of cancer recurrence, metastasis, and drug resistance. Therefore, to address the therapeutic conundrum, this study focused on rewinding metabolic reprogramming of CSCs as a novel therapeutic strategy. HCC CSCs exhibited elevated fatty acid (FA) metabolism compared with parental cells. To specifically target FA metabolism in CSCs, we utilized cerulenin, a fatty acid synthase (FASN) inhibitor. Surprisingly, cerulenin can diminish CSC-like characteristics, including stemness gene expression, spherogenicity, tumorigenicity, and metastatic potential. In addition, sorafenib, a multikinase inhibitor used as targeted therapy for advanced HCC, was employed in combination with cerulenin, demonstrating a great synergistic effect, particularly in CSCs. Importantly, our RNA sequencing analysis disclosed that the amyloid protein precursor (APP) is a crucial downstream effector of FASN in regulating CSC properties. We found that APP plays a crucial role in CSCs' characteristics that can be inhibited by cerulenin. By focusing on FA metabolism, this study identified the FASN/APP axis as a viable target to develop a more potent therapy strategy for advanced HCC.

Metabolic dysfunction-associated steatotic liver disease has emerged as a leading global cause of chronic liver disease. Our recent translational investigations have shown that the STE20-type kinases comprising the GCKIII subfamily-MST3, STK25, and MST4-associate with hepatic lipid droplets and regulate ectopic fat storage in the liver; however, the mode of action of these proteins remains to be resolved. By comparing different combinations of the silencing of MST3, STK25, and/or MST4 in immortalized human hepatocytes, we found that their single knockdown results in a similar reduction in hepatocellular lipid content and metabolic stress, without any additive or synergistic effects observed when all three kinases are simultaneously depleted. A genome-wide yeast two-hybrid screen of the human hepatocyte library identified several interaction partners contributing to the GCKIII-mediated regulation of liver lipid homeostasis, that is, PDCD10 that protects MST3, STK25, and MST4 from degradation, MAP4K4 that regulates their activity via phosphorylation, and HSD17B11 that controls their action via a conformational change. Finally, using in vitro kinase assays on microfluidic microarrays, we pinpointed various downstream targets that are phosphorylated by the GCKIII kinases, with known functions in lipogenesis, lipolysis, and lipid secretion, as well as glucose uptake, glycolysis, hexosamine synthesis, and ubiquitination. Together, this study demonstrates that the members of the GCKIII kinase subfamily regulate hepatocyte lipid metabolism via common pathways. The results shed new light on the role of MST3, STK25, and MST4, as well as their interactions with PDCD10, MAP4K4, and HSD17B11, in the control of liver lipid homeostasis and metabolic dysfunction-associated steatotic liver disease susceptibility.

Gaucher disease (GD) is a lysosomal storage disorder (LSD) resulting from inherited glucocerebrosidase (GBA1) deficiency. GD diagnosis relies on GBA1 activity assays, typically employing 4-methylumbelliferyl-β-D-glucopyranoside (4MU-β-Glc) as fluorogenic substrate. However, these assays suffer from background 4MU release by the non-lysosomal GBA2 and cytosolic GBA3 enzymes. Here we developed GBA1-selective fluorogenic substrates by synthesizing a series of 6-O-acyl-4MU-β-Glc substrates with diverse fatty acid tails. Because of the chemical and enzymatic instability of the ester bonds, analogs of 6-O-palmitoyl-4MU-β-Glc (3) with different chemical linkages were synthesized. 6-O-alkyl-4MU-β-Glc 9, featuring an ether linkage, emerged as the most optimal GBA1 substrate, exhibiting both a low K_m and compared to substrate 3 a high V_max. Importantly, substrate 9 is not hydrolyzed by GBA2 and GBA3 and therefore acts as a superior substrate for GD diagnosis. Plants contain glycosyl phytosterols (campesterol, β-sitosterol, and sigmasterol) that may also be acylated at C-6. LC-MS/MS analysis revealed that 6-O-acylated and regular glycosylcholesterol (HexChol) tend to be increased in spleens of patients with GD. Moreover, significant increases in 6-O-acyl-glycosyl-phytosterols were detected in GD spleens. Our findings suggest uptake of (6-O-acyl)-glycosyl-phytosterols from plant food and subsequent lysosomal processing by GBA1, and comprise the first example of accumulation of an exogenous class of glycolipids in GD. Excessive exposure of rodents to glycosylated phytosterols has been reported to induce manifestations of Parkinson's disease (PD). Further investigation is warranted to determine whether (6-O-acyl)-glycosyl-phytosterols could contribute to the enigmatic link between inherited defects in GBA1 and the risk for PD.

Osteoporosis is linked to increased bone marrow adipocyte (BMAd) proliferation, which displaces bone-forming cells and alters the local environment. The impact of BMAd lipid droplets on bone health and osteoblast function remains unclear. This study investigates the interplay between BMAd-derived lipid droplets and osteoblast functionality, focusing on ferroptosis pathways. Osteoblast cultures were treated with conditioned media from adipocytes to simulate in vivo conditions. High-throughput mRNA sequencing and Western blot analysis were used to profile changes in gene expression and protein levels related to ferroptosis, oxidative phosphorylation, and osteogenic markers. Cellular assays assessed the direct impact of lipid droplets on osteoblast activity. Results showed that osteoblasts exposed to adipocyte-conditioned media had increased intracellular lipid droplet accumulation, upregulation of ferroptosis-related genes and proteins, and downregulation of oxidative phosphorylation and osteoblast differentiation markers. Treatment with ferroptosis inhibitors reversed the detrimental effects on osteoblasts, indicating the functional relevance of this pathway in osteoporosis. BMAd-derived lipid droplets contribute to osteoblast dysfunction through ferroptosis induction. Inhibiting ferroptosis could preserve osteoblast function and combat osteoporosis-related bone issues, suggesting that modulating lipid metabolism and redox balance in bone cells may be promising for future treatments.

Fever is a host-pathogen defense mechanism in which the immune system drives a physiologic increase in core body temperature. For over 50 years, it has been known that the temperature of brown adipose tissue (BAT) is increased during the febrile response. However, recent studies suggested that the primary thermogenic protein Uncoupling protein 1 in brown adipocytes does not contribute to fever induction in mice, casting doubt about the functional contribution of BAT to fever. In a new set of studies, Li et al. (2024) provide compelling evidence that fatty acid oxidation is markedly increased in BAT in a Salmonella infection model of fever and strongly suggest that metabolic adaptation in BAT may play a critical role in the febrile response. This article re-opens the debate about how thermogenic and metabolic programs in BAT contribute to fever and raises new questions about whether BAT contributes to host defense against pathogens.

Recent studies have challenged the traditional belief that mature fat cells are irreversibly differentiated and revealed they can dedifferentiate into fibroblast-like cells known as dedifferentiated fat (DFAT) cells. Resembling pluripotent stem cells, DFAT cells hold great potential as a cell source for stem cell therapy. However, there is limited understanding of the specific changes that occur following adipocyte dedifferentiation and the detailed regulation of this process. This review explores the epigenetic, genetic, and phenotypic alterations associated with DFAT cell dedifferentiation, identifies potential targets for clinical regulation and discusses the current applications and challenges in the field of DFAT cell research.

Inflammation is part of natural immune defense mechanism against any form of infection or injury. However, prolonged inflammation could perturb cell homeostasis and contribute to the development of metabolic and inflammatory diseases, including maternal obesity, diabetes, cardiovascular diseases, and metabolic dysfunction-associated steatotic liver diseases (MASLD). Polyunsaturated fatty acids have been shown to mitigate inflammatory response by generating specialized proresolving lipid mediators, which take part in resolution of inflammation. Similarly here, we show that palmitoleate, an omega-7 monounsaturated fatty acid exerts anti-inflammatory properties in response to lipopolysaccharide (LPS)-mediated inflammation. Exposure of bone marrow-derived macrophages (BMDMs) to LPS or TNFα induces robust increase in the expression of proinflammatory cytokines and supplementation of palmitoleate inhibited LPS-mediated upregulation of proinflammatory cytokines. We also observed that palmitoleate was able to block LPS + ATP-induced inflammasome activation mediated cleavage of procaspase 1 and prointerleukin-1β. Further, treatment of palmitoleate protects against LPS-induced inflammation in human THP-1-derived macrophages and trophoblasts. Coexposure of LPS and palmitate (saturated free fatty acid) induces inflammasome and cell death in BMDMs, however, treatment of palmitoleate blocked LPS and palmitate-induced cell death in BMDMs. Further, LPS and palmitate together results in the activation of mitogen-activated protein kinases and pretreatment of palmitoleate inhibited the activation of mitogen-activated protein kinases and nuclear translocation of nuclear factor kappa B in BMDMs. In conclusion, palmitoleate shows anti-inflammatory properties against LPS-induced inflammation and LPS + palmitate/ATP-induced inflammasome activity and cell death.