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Lecithin:retinol acyltransferase (LRAT) is the main enzyme producing retinyl esters (REs) in quiescent hepatic stellate cells (HSCs). When cultured on stiff plastic culture plates, quiescent HSCs activate and lose their RE stores in a process similar to that in the liver following tissue damage, leading to fibrosis. Here we validated HSC cultures in soft gels to study RE metabolism in stable quiescent HSCs and investigated RE synthesis and breakdown in activating HSCs. HSCs cultured in a soft gel maintained characteristics of quiescent HSCs, including the size, amount and composition of their characteristic large lipid droplets. Quiescent gel-cultured HSCs maintained high expression levels of Lrat and a RE storing phenotype with low levels of RE breakdown. Newly formed REs are highly enriched in retinyl palmitate (RP), similar to freshly isolated quiescent HSCs, which is associated with high LRAT activity. Comparison of these quiescent gel-cultured HSCs with activated plastic-cultured HSCs showed that although during early activation the total RE levels and RP-enrichment are reduced, levels of RE formation are maintained and mediated by LRAT. Loss of REs was caused by enhanced RE breakdown in activating HSCs. Upon prolonged culturing, activated HSCs have lost their LRAT activity and produce small amounts of REs by DGAT1. This study reveals unexpected dynamics in RE metabolism during early HSC activation, which might be important in liver disease as early stages are reversible. Soft gel cultures provide a promising model to study RE metabolism in quiescent HSCs, allowing detailed molecular investigations on the mechanisms for storage and release., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The molecular signature of cell-derived extracellular vesicles (EVs) from synovial fluid (SF) offers insights into the cells and molecular processes associated with joint disorders and can be exploited to define biomarkers. The EV-signature is determined by cargo molecules and the lesser-studied lipid bilayer. We here investigated the lipidome of SF-EVs in inflamed joints derived from Rheumatoid Arthritis (RA) and Spondyloarthritis (SpA) patients, two autoimmune-driven joint diseases, and compared these signatures to the lipid profile of equine SF-EVs obtained during induced acute synovitis. Since neutrophils are primary SF-infiltrating cells during these inflammatory joint diseases, we also analyzed how inflammatory stimuli alter the lipidomic profile of human and equine neutrophil-derived EVs (nEVs) in vitro and how these signatures relate to the lipidome signatures of SF-EVs from inflamed joints. We identified neutrophil stimulation intensity-dependent changes in the lipidomic profile of nEVs with elevated presence of dihexosylceramide (lactosylceramide), phosphatidylserine, and phosphatidylethanolamine ether-linked lipid classes in human nEVs upon full neutrophil activation. In horses, levels of monohexosylceramide (glucosylceramide) increased instead of dihexosylceramide, indicating species-specific differences. The lipid profiles of RA and SpA SF-EVs were relatively similar and showed a relative resemblance with stimulated human nEVs. Similarly, the lipidome of equine synovitis-derived SF-EVs closer resembled the one of stimulated equine nEVs. Hence, lipidome profiling can provide insights into the contribution of nEVs to the heterogeneous pool of SF-EVs, deepening our understanding of inflammatory joint diseases and revealing molecular changes in joint homeostasis, which can lead to the development of more precise disease diagnosis and treatment strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Obesity represents a significant health challenge, intricately linked to conditions such as type II diabetes, metabolic syndrome, and hepatic steatosis. Several existing obesity treatments exhibit limited efficacy, undesirable side effects or a limited capability to maintain therapeutics effects in the long-term. Recently, modulation Coenzyme Q (CoQ) metabolism has emerged as a promising target for treatment of metabolic syndrome. This potential intervention could involve the modulation of endogenous CoQ biosynthesis by the use of analogs of the precursor of its biosynthesis, such as β-resorcylic acid (β-RA). Here, we show that oral supplementation with β-RA, incorporated into the diet of diet-induced obese (DIO) mice, leads to substantial weight loss. The anti-obesity effects of β-RA are partially elucidated through the normalization of mitochondrial CoQ metabolism in white adipose tissue (WAT). Additionally, we identify an HFN4α/LXR-dependent transcriptomic activation of the hepatic lipid metabolism that contributes to the anti-obesity effects of β-RA. Consequently, β-RA mitigates WAT hypertrophy, prevents hepatic steatosis, counteracts metabolic abnormalities in WAT and liver, and enhances glucose homeostasis by reducing the insulin/glucagon ratio and plasma levels of gastric inhibitory peptide (GIP). Moreover, pharmacokinetic evaluation of β-RA supports its translational potential. Thus, β-RA emerges as an efficient, safe, and translatable therapeutic option for the treatment and/or prevention of obesity, metabolic dysfunction-associated steatotic liver disease (MASLD)., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Luis C. Lopez reports article publishing charges was provided by University of Granada. Luis C. Lopez has patent #WO2022123103 issued to No. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Inflammation is the hallmark of most joint disorders. However, the precise regulation of induction, perpetuation, and resolution of joint inflammation is not entirely understood. Since extracellular vesicles (EVs) are critical for intercellular communication, we aim to unveil their role in these processes. Here, we investigated the EVs' dynamics and phospholipidome profile from synovial fluid (SF) of healthy equine joints and from horses with lipopolysaccharide (LPS)-induced synovitis. LPS injection triggered a sharp increase of SF-EVs at 5-8 h post-injection, which started to decline at 24 h post-injection. Importantly, we identified significant changes in the lipid profile of SF-EVs after synovitis induction. Compared to healthy joint-derived SF-EVs (0 h), SF-EVs collected at 5, 24, and 48 h post-LPS injection were strongly increased in hexosylceramides. At the same time, phosphatidylserine, phosphatidylcholine, and sphingomyelin were decreased in SF-EVs at 5 h and 24 h post-LPS injection. Based on the lipid changes during acute inflammation, we composed specific lipid profiles associated with healthy and inflammatory state-derived SF-EVs. The sharp increase in SF-EVs during acute synovitis and the correlation of specific lipids with either healthy or inflamed states-derived SF-EVs are findings of potential interest for unveiling the role of SF-EVs in joint inflammation, as well as for the identification of EV-biomarkers of joint inflammation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

In response to changes in their environment bacteria need to change both their protein and phospholipid repertoire to match environmental requirements, but the dynamics of bacterial phospholipid composition under different growth conditions is still largely unknown. In the present study, we investigated the phospholipidome of the bacterial pathogen Campylobacter jejuni. Transcription profiling on logarithmic and stationary phase grown cells of the microaerophilic human pathogen C. jejuni using RNA-seq revealed differential expression of putative phospholipid biosynthesis genes. By applying high-performance liquid chromatography tandem-mass spectrometry, we identified 203 phospholipid species representing the first determination of the phospholipidome of this pathogen. We identified nine different phospholipid classes carrying between one and three acyl chains. Phospholipidome analysis on bacteria of different ages (0-5 days) showed rapid changes in the ratio of phospholipids containing ethanolamine, or glycerol as phospholipid head group and in the number of cyclopropane bond containing fatty acids. Oxygen concentration influenced the percentage of lysophospholipids, and cyclo-propane bonds containing acyl chains. We show that large amounts of the phospholipids are lysophospholipids (30-45%), which mutant studies reveal are needed for normal C. jejuni motility at low oxygen conditions. C. jejuni possesses an unusual phospholipidome that is highly dynamic in response to environmental changes., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Lysophosphatidic acid (LPA) accumulates in the central atheroma of human atherosclerotic plaques and is the primary platelet-activating lipid constituent of plaques. Here, we investigated the enzymatic regulation of LPA homeostasis in atherosclerotic lesions at various stages of disease progression. Atherosclerotic lesions were induced in carotid arteries of low-density lipoprotein receptor-deficient mice by semiconstrictive collar placement. At 2-week intervals after collar placement, lipids and RNA were extracted from the vessel segments carrying the plaque. Enzymatic-and liquid chromatography-mass spectrometry-based lipid profiling revealed progressive accumulation of LPA species in atherosclerotic tissue preceded by an increase in lysophosphatidylcholine, a precursor in LPA synthesis. Plaque expression of LPA-generating enzymes cytoplasmic phospholipase A(2)IVA (cPLA(2)IVA) and calcium-independent PLA(2)VIA (iPLA(2)VIA) was gradually increased, whereas that of the LPA-hydrolyzing enzyme LPA acyltransferase alpha was quenched. Increased expression of cPLA(2)IVA and iPLA(2)VIA in advanced lesions was confirmed by immunohistochemistry. Moreover, LPA receptors 1 and 2 were 50% decreased and sevenfold upregulated, respectively. Therefore, key proteins in LPA homeostasis are increasingly dysregulated in the plaque during atherogenesis, favoring intracellular LPA production. This might at least partly explain the observed progressive accumulation of this thrombogenic proinflammatory lipid in human and mouse plaques. Thus, intervention in the enzymatic LPA production may be an attractive measure to lower intraplaque LPA content, thereby reducing plaque progression and thrombogenicity.