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Seasonality can influence many physiological traits requiring optimal energetic capacity for life-history stage transitions. In Atlantic salmon, high-energy status is essential for the initiation of maturation. Atlantic salmon lipid reserves are predominantly found in the viscera and myosepta in the muscle while the liver is essential for maintaining lipid metabolism. A genomic study found a region including a transcription co-factor-coding gene,vgll3, linked to Atlantic salmon maturation timing, which acts as an inhibitor of adipogenesis in mice, and mediates maturation via condition factor in Atlantic salmon. Here we investigate the influence of season andvgll3genotypes associating with early (EE) and late (LL) maturation on lipid profiles in the muscle and liver in juvenile Atlantic salmon. We reared Atlantic salmon for two years until the occurrence of sexually mature males and sampled muscle and liver at two time points: spring and autumn of the second year. We found no seasonal or genotype effect in lipid profiles in muscle of immature males and females. However, in the liver we did detect a triacylglycerol (TG) enrichment and a genotype specific direction of change in membrane lipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), from spring to autumn. Specifically, from spring to autumn membrane lipid concentrations increased in vgll3*EE individuals and decreased in vgll3*LL individuals. This could be explained with two possible scenarios 1) a seasonally more stable capacity of endoplasmic reticulum (ER) functions invgll3*EE individuals compared tovgll3*LL individuals or 2)vgll3*LL individuals storing larger lipid droplets from spring to autumn in the liver compared tovgll3*EE individuals at the expense of ER capacity. This genotype specific seasonal direction of change in membrane lipid concentrations provides more indirect evidence that a mechanism linkingvgll3with lipid metabolism and storage exists.HighlightsSeasonal lipid species profile separation in muscle and liver in juvenile Atlantic salmonGenotype specific direction of change of membrane lipids from spring to autumnIndirect evidence that a mechanism linkingvgll3with lipid metabolism and storage exists

Background: There is little knowledge on the effects of alpha-linolenic acid (ALA) and n-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) on the LDL lipidome and aggregation of LDL particles. Objective: We examined if consumption of Camelina sativa oil (CSO) as a source of ALA, fatty fish (FF) as a source of n-3 LCPUFA and lean fish (LF) as a source of fish protein affect the lipidome of LDL as compared to a control diet. Methods: Participants with impaired glucose tolerance (39 women and 40 men) were randomized to 4 study groups (CSO providing 10 g/d ALA, FF and LF [both 4 fish meals/wk] and control limiting their fish and ALA intake) in a 12-week, parallel trial. Diets were instructed and dietary fats were provided to the participants. The lipidome of LDL particles isolated from samples collected at baseline and after intervention was analyzed with electrospray ionization-tandem mass spectrometry. Results: In the CSO group, the relative concentrations of saturated and monounsaturated cholesteryl ester species in LDL decreased and the species with ALA increased. In the FF group, LDL phosphatidylcholine (PC) species containing n-3 LCPUFA increased. There was a significant positive correlation between the change in total sphingomyelin and change in LDL aggregation, while total PC and triunsaturated PC species were inversely associated with LDL aggregation when all the study participants were included in the analysis. Conclusion: Dietary intake of CSO and FF modifies the LDL lipidome to contain more polyunsaturated and less saturated lipid species. The LDL surface lipids are associated with LDL aggregation. (c) 2021 National Lipid Association. Published by Elsevier Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

Drug-induced liver injury is an emerging form of acute and chronic liver disease that may manifest as fatty liver. Amiodarone (AMD), a widely used antiarrhythmic drug, can cause hepatic injury and steatosis by a variety of mechanisms, not all completely understood. We hypothesized that repetitive AMD administration may induce hepatic lipotoxicity not only via effects on the liver but also via effects on adipose tissue. Indeed, repetitive AMD administration induced endoplasmic reticulum (ER) stress in both liver and adipose tissue. In adipose tissue, AMD reduced lipogenesis and increased lipolysis. Moreover, AMD treatment induced ER stress and ER stress-dependent lipolysis in 3T3L1 adipocytes in vitro. In the liver, AMD caused increased expression of genes encoding proteins involved in fatty acid (FA) uptake and transfer (Cd36, Fabp1, and Fabp4), and resulted in increased hepatic accumulation of free FAs, but not of triacylglycerols. In line with this, there was increased expression of hepatic de novo FA synthesis genes. However, AMD significantly reduced the expression of the desaturase Scd1 and elongase Elovl6, detected at mRNA and protein levels. Accordingly, the FA profile of hepatic total lipids revealed increased accumulation of palmitate, an SCD1 and ELOVL6 substrate, and reduced levels of palmitoleate and cis-vaccenate, products of the enzymes. In addition, AMDtreated mice displayed increased hepatic apoptosis. The studies show that repetitive AMD induces ER stress and aggravates lipolysis in adipose tissue while inducing a lipotoxic hepatic lipid environment, suggesting that AMD-induced liver damage is due to compound insult to liver and adipose tissue. NEW & NOTEWORTHY AMD chronic administration induces hepatic lipid accumulation by several mechanisms, including induction of hepatic ER stress, impairment of b-oxidation, and inhibition of triacylglycerol secretion. Our study shows that repetitive AMD treatment induces not only hepatic ER stress but also adipose tissue ER stress and lipolysis and hepatic accumulation of free fatty acids and enrichment of palmitate in the total lipids. Understanding the toxicity mechanisms of AMD would help devise ways to limit liver damage.

Cardiolipin (CL) is an essential phospholipid for mitochondrial structure and function. Here we present a small mitochondrial protein, NERCLIN, as a negative regulator of CL homeostasis and mitochondrial ultrastructure. Primate-specific NERCLIN is expressed ubiquitously fromGRPEL2locus on a tightly regulated low level, but induced by heat stress. NERCLIN overexpression severely disrupts mitochondrial cristae structure and induces mitochondrial fragmentation. Proximity labeling suggested interactions of NERCLIN with CL synthesis and prohibitin complexes on the matrix side of the inner mitochondrial membrane. Lipid analysis indicated that NERCLIN regulates mitochondrial CL content. The regulation may occur directly through interaction with PTPMT1, a proximal partner on the CL synthesis pathway, as its product phosphatidylglycerol was also reduced by NERCLIN. We propose that NERCLIN contributes to stress-induced adaptation of mitochondrial dynamics and turnover by regulating the mitochondrial CL content. Our findings add NERCLIN to the group of recently identified small mitochondrial proteins with important regulatory functions.

Background and Purpose: Drug induced liver injury is an emerging form of acute and chronic liver disease that may manifest as fatty liver. Amiodarone (AMD), a widely used anti-arrhythmic drug, can cause hepatic injury and steatosis by a variety of mechanisms, which are not completely understood. Experimental Approach: Chronic damage was induced by daily gavage of 180mg/kg body weight AMD for four consecutive days to C57Bl/6OlaHsd male mice. Key Results: Chronic AMD administration induced endoplasmic reticulum (ER) stress in both liver and adipose tissue. In adipose tissue, AMD reduced lipogenesis and increased lipolysis. Moreover, AMD treatment induced ER stress and ER stress-dependent lipolysis in 3T3L1 adipocytes in vitro. In the liver, AMD caused increased expression of genes encoding proteins involved in fatty acid (FA) uptake and transfer (Cd36, Fabp1 and Fabp4) and resulted in increased hepatic accumulation of free FAs, but not of triacylglycerols. In line with this, there was increased expression of hepatic de novo FA synthesis genes (Srebp1 and FA synthase encoded by Fasn). However, AMD significantly reduced the expression of the desaturase Scd1 and elongase Elovl6, detected at mRNA and protein levels. Accordingly, the FA profile of hepatic total lipids revealed increased accumulation of palmitate, a SCD1 and ELOVL6 substrate, and reduced levels of palmitoleate and cis-vaccenate, products of the enzymes. In addition, AMD-treated mice displayed increased hepatic apoptosis, known to be induced by lipotoxic palmitate. Conclusions and Implications: Chronic AMD induced ER stress and aggravated lipolysis in adipose tissue, while inducing a lipotoxic hepatic lipid environment.

Human mesenchymal stromal/stem cells (hMSCs) show great promise in cell therapy due to their immunomodulatory properties. The overall immunomodulatory response of hMSCs resembles the resolution of inflammation, in which lipid mediators and regulatory macrophages (Mregs) play key roles. We investigated the effect of hMSC cell-cell contact and secretome on macrophages polarized and activated toward Mreg phenotype. Moreover, we studied the effect of supplemented polyunsaturated fatty acids (PUFAs): docosahexaenoic acid (DHA) and arachidonic acid, the precursors of lipid mediators, on hMSC immunomodulation. Our results show that unlike hMSC cell-cell contact, the hMSC secretome markedly increased the CD206 expression in both Mreg-polarized and Mreg-activated macrophages. Moreover, the secretome enhanced the expression of programmed death-ligand 1 on Mreg-polarized macrophages and Mer receptor tyrosine kinase on Mreg-activated macrophages. Remarkably, these changes were translated into improved Candida albicans phagocytosis activity of macrophages. Taken together, these results demonstrate that the hMSC secretome promotes the immunoregulatory and proresolving phenotype of Mregs. Intriguingly, DHA supplementation to hMSCs resulted in a more potentiated immunomodulation with increased CD163 expression and decreased gene expression of matrix metalloproteinase 2 in Mreg-polarized macrophages. These findings highlight the potential of PUFA supplementations as an easy and safe method to improve the hMSC therapeutic potential.

The current clinical care of glioblastomas leaves behind invasive, radio- and chemo-resistant cells. We recently identified mammary-derived growth inhibitor (MDGI/FABP3) as a biomarker for invasive gliomas. Here, we demonstrate a novel function for MDGI in the maintenance of lysosomal membrane integrity, thus rendering invasive glioma cells unexpectedly vulnerable to lysosomal membrane destabilization. MDGI silencing impaired trafficking of polyunsaturated fatty acids into cells resulting in significant alterations in the lipid composition of lysosomal membranes, and subsequent death of the patient-derived glioma cells via lysosomal membrane permeabilization (LMP). In a preclinical model, treatment of glioma-bearing mice with an antihistaminergic LMP-inducing drug efficiently eradicated invasive glioma cells and secondary tumours within the brain. This unexpected fragility of the aggressive infiltrating cells to LMP provides new opportunities for clinical interventions, such as re-positioning of an established antihistamine drug, to eradicate the inoperable, invasive, and chemo-resistant glioma cells from sustaining disease progression and recurrence.

Human mesenchymal stromal/stem cells (hMSCs) are used in experimental cell therapy to treat various immunological disorders, and the extracellular vesicles (hMSC-EVs) they produce have emerged as an option for cell-free therapeutics. The immunomodulatory function of hMSCs resembles the resolution of inflammation, in which proresolving lipid mediators (LMs) play key roles. Multiple mechanisms underlying the hMSC immunosuppressive effect has been elucidated; however, the impact of LMs and EVs in the resolution is poorly understood. In this study, we supplemented hMSCs with polyunsaturated fatty acids (PUFAs); arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, which serve as precursors for multiple LMs. We then determined the consequent compositional modifications in the fatty acid, phospholipid, and LM profiles. Mass spectrometric analyses revealed that the supplemented PUFAs were incorporated into the main membrane phospholipid classes with different dynamics, with phosphatidylcholine serving as the first acceptor. Most importantly, the PUFA modifications were transferred into hMSC-EVs, which are known to mediate hMSC immunomodulation. Furthermore, the membrane-incorporated PUFAs influenced the LM profile by increasing the production of downstream prostaglandin E-2 and proresolving LMs, including Resolvin E2 and Resolvin D6. The production of LMs was further enhanced by a highly proinflammatory stimulus, which resulted in an increase in a number of mediators, most notably prostaglandins, while other stimulatory conditions had less a pronounced impact after a 48-h incubation. The current findings suggest that PUFA manipulations of hMSCs exert significant immunomodulatory effects via EVs and proresolving LMs, the composition of which can be modified to potentiate the therapeutic impact of hMSCs.

Malignant brain tumors represent a surgical and therapeutic challenge. Despite major breakthrough in the precision neurosurgery and the personalized medicine, it remains impossible to circumvent the tumor relapse. This is due to the highly infiltrative nature of the glioma cells, with single tumor-initiating cells invading far distances in the brain. However, we recently identified a major flaw in the invasive tumor cell biology: a high sensitivity to the lysosomal membrane permeabilization (LMP). We first identified the fatty acid binding-protein 3 (FABP3) specifically expressed by invasive gliomas cells. Expression of FABP3 is indispensable to the transportation of poly-unsaturated fatty acids (PUFAs), which cannot be otherwise synthetized by the cells, from the extracellular space to biological membranes. Silencing of FABP3 stopped the supply of PUFAs that are essential to the lysosomal membrane maintenance. Induction of the LMP activated a cascade of events including the release of the lysosomal cathepsins in the cytosol, leading to the tumor cell death. Interestingly, the specific killing of invasive glioma cells through the LMP can be achieved by using lysosomotropic drugs, such as anti-histamines. These cationic amphiphilic molecules accumulate in the lysosome and induce the phospholipidosis of the lysosomal membrane. We therefore tested the ability of the blood-brain-barrier permeable clemastine, an anti-histamine, to reduce the tumorigenicity several patient-derived gliomas implanted in nude mice. Although clemastine treatment did not modify the primary tumor mass growth, it completely eradicated the invasive population. These promising results obtained by therapeutic activation of the LMP could also be beneficial for other aggressive cancers models, such as brain metastases of breast cancer or metastatic pancreatic cancer. Citation Format: Vadim Le Joncour, Pauliina Filppu, Minna Holopainen, Maija Hyvönen, S. Pauliina Turunen, Harri Sihto, Isabel Burghardt, Juha Jääskeläinen, Michael Weller, Kaisa Lehti, Reijo Käkela, Pirjo Laakkonen. Novel therapeutic option targeting the tumor cell lysosomes [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-055.

Platelets are collected for transfusion to patients with different hematological disorders, and for logistical reasons, platelets are stored as concentrates. Despite the carefully controlled conditions, platelets become activated during storage, and platelet concentrates (PLCs) may cause adverse inflammatory reactions in the recipients. We studied by mass spectrometry the lipidomic changes during storage of the clinical PLCs, the platelets isolated from PLCs, and the extracellular vesicles (EVs) thereof. The release of EVs from platelets increased with the prolonged storage time. The molar percentages of arachidonic acid -containing species were increased during storage especially in the phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine classes of glycerophopholipids. The increase of these species in the membrane glycerophopholipid composition paralleled the production of both proinflammatory and proresolving lipid mediators (LMs) as the amount of the arachidonic acid-derived LMs such as thromboxane B2 and prostaglandin E2 also increased in time. Moreover, several monohydroxy pathway markers and functionally relevant proinflammatory and proresolving LMs were detected in the PLC and the EVs, and some of these clearly accumulated during storage. By Western blot, the key enzymes of these pathways were shown to be present in the platelets and in many cases also in the EVs. Since the EVs were enriched in the fatty acid precursors of LMs, harbored LM-producing enzymes, contained the related monohydroxy pathway markers, and also secreted the final LM products, the PLC-derived EVs appear to have the potential to regulate inflammation and healing, and may thereby aid the platelets in exerting their essential physiological functions.

High arachidonic acid (20:4n-6) and low n-3 PUFA levels impair the capacity of cultured human bone marrow mesenchymal stromal cells (hBMSCs) to modulate immune functions. The capacity of the hBMSCs to modify PUFA structures was found to be limited. Therefore, different PUFA supplements given to the cells resulted in very different glycerophospholipid (GPL) species profiles and substrate availability for phospholipases, which have preferences for polar head group and acyl chains when liberating PUFA precursors for production of lipid mediators. When supplemented with 20:4n-6, the cells increased prostaglandin E2 secretion. However, they elongated 20:4n-6 to the less active precursor, 22:4n-6, and also incorporated it into triacylglycerols, which may have limited the proinflammatory signaling. The n-3 PUFA precursor, 18:3n-3, had little potency to reduce the GPL 20:4n-6 content, while the eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acid supplements efficiently displaced the 20:4n-6 acyls, and created diverse GPL species substrate pools allowing attenuation of inflammatory signaling.(Jlr) The results emphasize the importance of choosing appropriate PUFA supplements for in vitro hBMSC expansion and suggests that for optimal function they require an exogenous fatty acid source providing 20:5n-3 and 22:6n-3 sufficiently, but 20:4n-6 moderately, which calls for specifically designed optimal PUFA supplements for the cultures.

Human mesenchymal stromal cells (hMSCs) are fibroblast-like cells that have an exceptional ability to modulate immune cells. Due to their immuno-modulatory properties, hMSCs have been employed in various clinical trials in the treatment of autoimmune or inflammatory diseases. Even though hMSC therapy has yielded multiple promising results, not all trials have been successful. Due to the discrepancies in the therapeutic response, hMSC therapy requires further development and standardisation. While optimisation of the culture conditions provides one method to improve the therapeutic efficacy of hMSCs, fine-tuning the culture conditions requires deep understanding of the hMSC immunomodulatory mechanisms. It has been established that hMSCs mediate their therapeutic effect via cell-cell contact and especially by secreting several paracrine factors that include lipid mediators and extracellular vesicles (EVs). Intriguingly, hMSC-derived EVs (hMSC-EVs) are able to mediate the therapeutic response of MSCs, which has led to a growing interest in and research on cell-free hMSC-EV therapy. In addition to EVs, lipid metabolism and especially the lipid mediator prostaglandin E2 (PGE2) are vital to the hMSC immunomodulation. Interestingly, the membrane lipid composition correlates with the immunosuppressive capacity of hMSCs, suggesting that membrane lipids play a role in mediating the immunomodulatory response of hMSCs. Lipid mediators are derived from polyunsaturated fatty acids (PUFAs) that can be stored in membrane phospholipids. Over the past few decades, the significance of PUFA-derived lipid mediators in orchestrating the dampening phase of inflammation, i.e., resolution, has been unravelled. These novel specialized proresolving mediators (SPMs) have several essential roles in modulating immune cells, including macrophages. The role of these SPMs in hMSC immunomodulation has received only marginal interest, and whether hMSCs produce multiple SPMs has not been determined. Keeping in mind that hMSC-EVs mediate the therapeutic response of MSCs, we investigated the lipid metabolism of hMSCs and their EVs after supplementing the cells with lipid mediator precursor PUFAs: arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid (DHA). Due to the supplementation, the membrane phospholipid and fatty acid composition were notably modified and the downstream lipid mediator production was enhanced. Excitingly, we were able to demonstrate for the first time that hMSCs produce several SPMs, which may mediate the immunomodulatory response of hMSCs. Remarkably, we showed that the PUFA modifications in the phospholipid composition were transferred into the EVs, highlighting the importance of EVs as transporters of the immunomodulatory factors derived from hMSCs. Because of their importance in the resolution of inflammation, we investigated the effects of hMSCs and hMSC-EVs on macrophages with a focus on regulatory macrophages (Mregs). We elucidated that both hMSCs and hMSC-EVs enhanced the anti-inflammatory and proresolving properties of these less-studied macrophages, highlighting the importance of PGE2 in the function of hMSC-EVs. Moreover, the hMSC secretome increased the CD206 expression and Candida albicans phagocytosis activity of macrophages, demonstrating a functional change in the macrophage properties. Fascinatingly, the DHA-supplemented hMSCs even further skewed the macrophage phenotype in an anti-inflammatory direction. However, the change was limited, and the elucidation of the functional effects of PUFA supplementations on hMSCs require additional investigations. In conclusion, this thesis provides further evidence that the lipid metabolism has an essential role in hMSC functionality and that the SPM production may represent an additional mechanism in hMSC immunomodulation. For the first time, we have explored the impact of hMSCs and hMSC-EVs on Mregs and our results highlight the importance of EVs as the mediators of hMSC immunomodulation. Furthermore, we investigated the possibility of improving the hMSC immunomodulation with PUFA supplementations that would represent an easy and safe way to enhance the therapeutic potential of hMSCs or hMSC-EVs. A more detailed understanding of the complex immunomodulatory mechanisms of hMSCs is in key position when investigating new possibilities in the development of hMSC therapy. Aikuisesta ihmisestä peräisin olevia mesenkymaalisia stroomasoluja (hMSC) on käytetty erilaisissa soluterapiasovellutuksissa jo kymmenien vuosien ajan lupaavin tuloksin. Potilaat kuitenkin reagoivat soluterapiaan hyvin eri tavoin eikä solujen toimintamekanismeja tunneta edelleen täysin. Näiden seikkojen vuoksi on tärkeää kehittää hMSC-terapiaa pidemmälle. Aiempien tutkimusten perusteella on osoitettu, että solunulkoiset vesikkelit (EV) välittävät hMSC:jen terapeuttista vastetta. Lisäksi solukalvon lipidikoostumus on linkitetty solujen vasteen tehoon. Solukalvon fosfolipidit ja niiden rakennusosaset eli monityydyttymättömät rasvahapot (PUFA) ovat esiasteita tulehduksessa toimiville lipidimediaattoreille. Tulehdusta vaimentavat lipidimediaattorit ovat hyvin tärkeitä tulehdusreaktion aktiivisessa alasajossa. Onkin ajateltu, että hMSC:t osallistuisivat tulehduksen alasajoon, mutta näiden solujen ja tulehdusta vaimentavien lipidimediaattoreiden välistä yhteyttä ei ole kunnolla muodostettu. Väitöskirjassa tutkittiin hMSC:jen ja hMSC-EV:en toimintamekanismeja erityisesti lipidomiikan näkökulmasta. Havaitsimme, että hMSC:t ja hMSC-EV:t paransivat säätelevien makrofagien tulehdusta alentavaa ilmiasua. Lisäksi makrofagien solusyöntiaktiivisuus, joka on tärkeää tulehduksen alasajossa, lisääntyi hMSC:jen vaikutuksesta. Tutkimme myös, miten PUFA:t vaikuttavat hMSC:jen ja hMSC-EV:en lipidikoostumukseen. Havaitsimme, että nämä lipidimediaattoreiden esiasteet tulivat osaksi solukalvoja ja muokkasivat solujen rasvahappokoostumusta. Lisäksi lisätyt PUFA:t lisäsivät tulehdusta vaimentavien lipidimediattorien tuotantoa. Havaitsimme myös, että nämä PUFA:illa muokatut hMSC:t saivat aikaan kaikkein suurimman vasteen aikaan makrofageissa tarkoittaen, että näiden hMSC:jen immuunisoluja säätelevä vaste oli kaikkein voimakkain. Väitöskirjassa tuotimme uutta tietoa hMSC:jen ja hMSC-EV:ien vaikutuksesta sääteleviin makrofageihin. Lisäksi havaintomme PUFA:jen vaikutuksista hMSC:jen lipidiaineenvaihdunnalle ja immuunisoluja säätelevälle vasteelle tukevat muiden tutkimusten tuloksia siitä, että nämä rasvahapot edistävät solujen terapeuttista tehoa. Lipidimediaattoreiden esiasteina toimivien rasvahappojen lisäykset olisivat helppoja ja turvallisia keinoja parantaa hMSC:jen ja hMSC-EV:en terapeuttista tehoa ja siten parantaa potilasturvallisuutta.