Inhibition of Lipid Accumulation and Oxidation in Hepatocytes by Bioactive Bean Extracts.

During our search for natural resources that can inhibit lipid droplet accumulation (LDA) and potentially prevent metabolic dysfunction-associated fatty liver disease (MAFLD) and its progressive stages, such as metabolic dysfunction-associated steatohepatitis (MASH), eight bean extracts (BE1-BE8) were tested for their ability to inhibit lipid accumulation and oxidation in hepatocytes. Substantial inhibitory effects on LDA with bean extracts (BEs) BE2, BE4, BE5, and BE8 were demonstrated. An advanced lipidomic approach was used to quantify the accumulation and inhibition of intracellular triacylglycerol (TAG) and its oxidized species, TAG hydroperoxide (TGOOH), in hepatocytes under fatty acid-loading conditions. The results show that the antioxidants BE2 and BE8 are potential candidates for regulating TAG and TGOOH accumulation in fatty acid-induced lipid droplets (LDs). This study suggests that bean-based foods inhibit LDs formation by decreasing intracellular lipids and lipid hydroperoxides in the hepatocytes. The metabolic profiling of BEs revealed that BE2 and BE8 contained polyphenolic compounds. These may be potential resources for the development of functional foods and drug discovery targeting MAFLD/MASH.

A facile method for monitoring sphingomyelin synthase activity in HeLa cells using liquid chromatography/mass spectrometry.

Sphingomyelin synthase (SMS) is a sphingolipid-metabolizing enzyme involved in the de novo synthesis of sphingomyelin (SM) from ceramide (Cer). Recent studies have indicated that SMS is a key therapeutic target for metabolic diseases such as fatty liver, type 2 diabetes, atherosclerosis, and colorectal cancer. However, very few SMS inhibitors have been identified because of the limited sensitivity and selectivity of the current fluorescence-based screening assay. In this study, we developed a simple cell-based assay coupled with liquid chromatography/tandem mass spectrometry (LC-MS/MS) to screen for SMS inhibitors. HeLa cells stably expressing SMS1 or SMS2 were used for the screening. A non-fluorescent unnatural C6-Cer was used as a substrate for SMS to produce C6-SM. C6-Cer and C6-SM levels in the cells were monitored and quantified using LC-MS/MS. The activity of ginkgolic acid C15:1 (GA), a known SMS inhibitor, was measured. GA had half-maximal inhibitory concentrations of 5.5 µM and 3.6 µM for SMS1 and SMS2, respectively. To validate these findings, hSMS1 and hSMS2 proteins were optimized for molecular docking studies. In silico analyses were conducted to assess the interaction of GA with SMS1 and SMS2, and its binding affinity. This study offers an analytical approach for screening novel SMS inhibitors and provides in silico support for the experimental findings.

Increased phosphatidylcholine and its hydroperoxides in serum low-density lipoproteins from patients with non-alcoholic steatohepatitis.

BACKGROUND: Non-alcoholic fatty liver disease is classified into simple steatosis (SS) and non-alcoholic steatohepatitis (NASH) according to histological findings from liver biopsies. Phosphatidylcholine (PC), the main component of phospholipids in serum lipoproteins, is easily oxidized to phosphatidylcholine hydroperoxide (PC-OOH). Although a lipid composition in the low-density lipoproteins (LDL) from patients with NASH could be abnormal, it remains unclear. Here, to better understand the characteristics of lipids in the LDL from NASH and SS, we compared the composition of PC and PC-OOH species in LDL particles (LDL-PC, LDL-PCOOH) from these patients, then clarified the association between these lipids and NASH severity. METHODS: The serum samples from patients with NASH (female, n = 9) and SS (female, n = 4; male, n = 2) were used for isolation of LDL. Total lipids were extracted from isolated LDL, and the species of PC and PC-OOH were measured using liquid chromatography-mass spectrometry/mass spectrometry. RESULTS: The sum of LDL-PC and the sum of LDL-PCOOH were significantly higher in NASH than in SS. Several LDL-PC (PC 32:0, 32:1, 32:2, 34:3, 36:2, sum of PC with saturated fatty acyl chains and sum of LDL-PC with polyunsaturated fatty acyl chains) and several LDL-PCOOH (34:2, 36:2, 36:3 and total) were increased significantly with increasing fibrosis score. In particular, a series of LDL-PCOOH were more reflective of the severity of fibrosis score. CONCLUSIONS: LDL-PC and LDL-PCOOH species were strongly correlated with the fibrosis score in NASH, which suggests that abnormal LDL is involved in the development of liver fibrosis.

Sex-Specific Effect of Ethanol on Colon Content Lipidome in a Mice Model Using Nontargeted LC/MS.

Consumption of alcohol has widespread effects on the human body. The organs that are most significantly impacted are the liver and digestive system. When alcohol is consumed, it is absorbed in the intestines and processed by the liver. However, excessive alcohol use may affect gut epithelial integrity, microbiome composition, and lipid metabolism. Despite past studies investigating the effect of ethanol on hepatic lipid metabolism, the focus on colonic lipid metabolism has not been well explored. In this study, we investigated the sex-specific effect of ethanol on the colonic content lipidome in a mouse model using nontargeted liquid chromatography-mass spectrometry. Comprehensive lipidome analysis of colonic flush samples was performed using ethanol-fed (EF) and pair-fed (PF) mice of each sex. Partial least-squares discriminant analysis revealed that ethanol altered colonic lipid composition largely in male mice compared with female mice. A significant increase in free fatty acids, ceramides, and hexosylceramides and decreased phosphatidylglycerols (PG) was observed in the EF group compared to the PF group in male mice. Phosphatidylethanolamine (PE) levels were increased significantly in the EF group of both sexes compared to the PF group. The volcanic plot shows that PG (O-15:1/15:0) and PE (O-18:2/15:0) are common markers that are increased in both sexes of the EF group. In addition, decreased fatty acid esters of hydroxy fatty acids (FAHFA) were observed specifically in the EF group of female mice. Overall, a significant variation in the mice colonic content lipidome between the EF and PF groups was observed. Target pathways, such as sphingolipid metabolism in males, FAHFA in females, and PE metabolism in both sexes, were suggested. This study provides new insight into the sex-dependent lipid change associated with alcohol-induced gut-microbiota dysfunction and its potential health impacts.

Regio-specific lipid fingerprinting of edible sea cucumbers using LC/MS.

Sea cucumbers are a rich source of bioactive compounds and are gaining popularity as nutrient-rich seafood. They are consumed as a whole organism in Pacific regions. However, limited data are available on the comparison of their lipid composition and nutritional value. In this study, untargeted liquid chromatography/mass spectrometry was applied to comprehensively profile lipids in the skin, meat, and intestinal contents of three color-distinct edible sea cucumbers. Multivariate principal component analysis revealed that the lipid composition of the intestinal contents of red, black, and blue sea cucumbers differs from that of skin, and meats. Polyunsaturated fatty acids (PUFAs) are abundant in the intestinal contents, followed by meats of sea cucumber. Lipid nutritional quality assessments based on fatty acid composition revealed a high P:S ratio, low index of atherogenicity, and high health promotion indices for the intestinal contents of red sea cucumber, suggesting its potential health benefits. In addition, hierarchical cluster analysis revealed that the intestinal contents of sea cucumbers were relatively high in PUFA-enriched phospholipids and lysophospholipids. Ceramides are abundant in black skin, blue meat, and red intestinal content samples. Overall, this study provides the first insights into a comprehensive regio-specific profile of the lipid content of sea cucumbers and their potential use as a source of lipid nutrients in food and nutraceuticals.

Dissecting new lipids and their composition in herbal tea using untargeted LC/MS.

Herbal teas and beverages have gained global attention because they are rich in natural bioactive compounds, which are known to have diverse biological effects, including antioxidant and anticarcinogenic properties. However, the lipidomic profiles of herbal teas remain unclear. In this study, we applied an untargeted lipidomics approach using high-performance liquid chromatography coupled with linear ion trap-Orbitrap mass spectrometry to comprehensively profile, compare, and identify unknown lipids in four herbal teas: dokudami, kumazasa, sugina, and yomogi. A total of 341 molecular species from five major classes of lipids were identified. Multivariate principal component analysis revealed distinct lipid compositions for each of the herbs. The fatty acid α-linolenic acid (FA 18:3) was found to be abundant in kumazasa, whereas arachidonic acid (FA 20:4) was the most abundant in sugina. Interestingly, novel lipids were discovered for the first time in plants; specifically, short-chain fatty acid esters of hydroxy fatty acids (SFAHFAs) with 4-hydroxy phenyl nonanoic acid as the structural core. This study provides insight into the lipidomic diversity and potential bioactive lipid components of herbal teas, offering a foundation for further research into their health-promoting properties and biological significance.

Kaempferol Improves Cardiolipin and ATP in Hepatic Cells: A Cellular Model Perspective in the Context of Metabolic Dysfunction-Associated Steatotic Liver Disease.

Targeting mitochondrial function is a promising approach to prevent metabolic dysfunction-associated steatotic liver disease (MASLD). Cardiolipin (CL) is a unique lipid comprising four fatty acyl chains localized in the mitochondrial inner membrane. CL is a crucial phospholipid in mitochondrial function, and MASLD exhibits CL-related anomalies. Kaempferol (KMP), a natural flavonoid, has hepatoprotective and mitochondrial function-improving effects; however, its influence on CL metabolism in fatty liver conditions is unknown. In this study, we investigated the effects of KMP on mitochondrial function, focusing on CL metabolism in a fatty liver cell model (linoleic-acid-loaded C3A cell). KMP promoted mitochondrial respiratory functions such as ATP production, basal respiration, and proton leak. KMP also increased the gene expression levels of CPT1A and PPARGC1A, which are involved in mitochondrial ß-oxidation. Comprehensive quantification of CL species and related molecules via liquid chromatography/mass spectrometry showed that KMP increased not only total CL content but also CL72:8, which strongly favors ATP production. Furthermore, KMP improved the monolysocardiolipin (MLCL)/CL ratio, an indicator of mitochondrial function. Our results suggest that KMP promotes energy production in a fatty liver cell model, associated with improvement in mitochondrial CL profile, and can serve as a potential nutrition factor in preventing MASLD.

Synthesis and quantification of short-chain fatty acid esters of hydroxy fatty acids in rat intestinal contents and fecal samples by LC-MS/MS.

Short-chain fatty acid esters of hydroxy fatty acids (SFAHFAs) are a new class of endogenous lipids belonging to the fatty acid esters of the hydroxy fatty acid family. We previously uncovered their chemical structure and discussed their potential biological significance. We anticipate an increased need for SFAHFA measurements as markers of metabolic and inflammatory health. In this study, we synthesized sixty isomeric SFAHFAs by combining 12 hydroxy fatty acids (C16-C24) and five short-chain fatty acids (C2-C6) including a labelled internal standard. SFAHFA enrichment was achieved by solid-phase extraction and established a sensitive method for their quantitation by targeted LC-MS/MS. The method was applied to profile SFAHFAs in intestinal contents and fecal samples collected from rats fed a high-fat diet (HFD). The results demonstrated a significant decrease in SFAHFAs in the intestinal contents of the HFD group compared with the control group. The fecal time course (0-8 weeks) profile of SFAHFAs showed significant downregulation of acetic and propanoic acid esters in just 2 weeks after HFD administration. This study offers the first synthesis and quantitation method for SFAHFAs, demonstrating their potential use in elucidating SFAHFA sources, their role in various diseases, and potential biochemical signalling pathways.

Glucosylceramide flippases contribute to cellular glucosylceramide homeostasis.

Lipid transport is an essential cellular process with importance to human health, disease development, and therapeutic strategies. Type IV P-type ATPases (P4-ATPases) have been identified as membrane lipid flippases by utilizing nitrobenzoxadiazole (NBD)-labeled lipids as substrates. Among the 14 human type IV P-type ATPases, ATP10D was shown to flip NBD-glucosylceramide (GlcCer) across the plasma membrane. Here, we found that conversion of incorporated GlcCer (d18:1/12:0) to other sphingolipids is accelerated in cells exogenously expressing ATP10D but not its ATPase-deficient mutant. These findings suggest that 1) ATP10D flips unmodified GlcCer as well as NBD-GlcCer at the plasma membrane and 2) ATP10D can translocate extracellular GlcCer, which is subsequently converted to other metabolites. Notably, exogenous expression of ATP10D led to the reduction in cellular hexosylceramide levels. Moreover, the expression of GlcCer flippases, including ATP10D, also reduced cellular hexosylceramide levels in fibroblasts derived from patients with Gaucher disease, which is a lysosomal storage disorder with excess GlcCer accumulation. Our study highlights the contribution of ATP10D to the regulation of cellular GlcCer levels and maintaining lipid homeostasis.

Lysosomal membrane integrity in fibroblasts derived from patients with Gaucher disease.

Gaucher disease (GD) is a recessively inherited lysosomal storage disorder characterized by a deficiency of lysosomal glucocerebrosidase (GBA1). This deficiency results in the accumulation of its substrate, glucosylceramide (GlcCer), within lysosomes. Here, we investigated lysosomal abnormalities in fibroblasts derived from patients with GD. It is noteworthy that the cellular distribution of lysosomes and lysosomal proteolytic activity remained largely unaffected in GD fibroblasts. However, we found that lysosomal membranes of GD fibroblasts were susceptible to damage when exposed to a lysosomotropic agent. Moreover, the susceptibility of lysosomal membranes to a lysosomotropic agent could be partly restored by exogenous expression of wild-type GBA1. Here, we report that the lysosomal membrane integrity is altered in GD fibroblasts, but lysosomal distribution and proteolytic activity is not significantly altered.Key words: glucosylceramide, lysosome, Gaucher disease, lysosomotropic agent.

Regiospecific analysis of lipidome in the brain from mammals of land and aquatic habitats-by liquid chromatography-mass spectrometry.

The brain is a complex organ demonstrated by the occurrence of specific types of functional lipids. Despite some studies focusing on providing the animal brain lipid signature, there are limited studies focusing on the comprehensive and regiospecific characterization of multiple animal brain lipidome. Herein we characterized about 294 lipid molecular species from six different lipid classes in different portions of the brain after fixation from mammals of different habitats, fully-aquatic (n = 6), semi-aquatic (n = 6), and terrestrial (n = 4), using liquid chromatography-mass spectrometry. The untargeted brain lipid profiling revealed a significant difference in total lipid levels between fully-aquatic, semi-aquatic, and terrestrial mammals. The polyunsaturated fatty acids and cholesterol esters are abundant in brain tissue of semi-aquatic followed by fully-aquatic mammals whereas phosphatidylethanolamines are profoundly high in terrestrial species. The regiospecific analysis revealed a predominance of sphingolipids in all the groups but no significant differences were observed between the different portions of the brain such as the cerebellum, cortex, pons, spinal cord, and thalamus. Interestingly the multivariate analysis showed almost the same lipid compositions in the spinal cord and thalamus of terrestrial mammals. Overall, this is the first report to compare the comprehensive brain-lipidome among different mammalian groups inhabiting three distinct habitats. These results indicate that the brain lipid composition is specific to the animal habitat.

Identification of a ß-Carboline Alkaloid from Chemoselectively Derived Vanilla Bean Extract and Its Prevention of Lipid Droplet Accumulation in Human Hepatocytes (HepG2).

Targeting bioactive compounds to prevent lipid droplet accumulation in the liver, we explored an antioxidative extract from vanilla bean (Vainilla planifolia) after chemo-selective derivatization through heating and acid modification. The chemical analysis of vanilla bean extract through chemoselective derivatization resulted in the identification of sixteen compounds (34-50) using LC-MS/MS analysis. A ß-carboline alkaloid with a piperidine C-ring and a vanillin moiety at C-1 (34) was identified by molecular networking and diagnostic fragmentation filtering approaches. ß-carboline alkaloid 34 exhibited significant inhibitory activity of lipid droplet accumulation (LDAI) in oleic acid-loaded hepatocellular carcinoma HepG2 cells. The LDAI activity was associated with both activation of lipolysis and suppression of lipogenesis in the cells. The study indicates that crude plant extracts, following chemoselective derivatization, may contain bioactive compounds that could be beneficial in preventing hepatosteatosis and could serve as a source of lead compounds for drug development. This approach may be useful to investigate other mixtures of natural products and food resources.

Plasmalogen Profiling in Porcine Brain Tissues by LC-MS/MS.

Plasmalogen, a functional glycerophospholipid, is known for its beneficial nutritional effects, such as anti-oxidation and anti-inflammation. As the porcine brain is a plasmalogen-rich resource, this study aimed to explore its potential for plasmalogen-based health food product development, with special attention on whether and how the industrial production processes influence the plasmalogen content and composition. In the present work, plasmalogens from different porcine brain products were investigated using liquid chromatography-tandem mass spectrometry. The results indicated that all the porcine brain products showed abundant total plasmalogens, of which more than 95% were ethanolamine plasmalogen species. Acetone precipitation, ethanol extraction, and drying did not significantly affect the plasmalogen content, whereas repeated freeze-thaw cycles in the production process led to noticeable loss. The chemometric investigation suggested that raw products and glycerophospholipid products exhibited different profiles; furthermore, the concentration step seemed to impact the plasmalogen composition. The nutritional assessment revealed that porcine brain products showed favorable values of multiple indexes, including PUFA/SFA ratio, n-6/n-3 ratio, thrombogenicity index, and unsaturation index, suggesting a health-beneficial value. The current study not only shows the feasibility of producing porcine brain-derived plasmalogens, but also provides possible strategies for developing and quality-controlling dietary plasmalogen supplements and healthcare products.

The elucidation of plasma lipidome profiles during severe influenza in a mouse model.

Although influenza virus infection has been shown to affect lipid metabolism, details remain unknown. Therefore, we elucidated the kinetic lipid profiles of mice infected with different doses of influenza virus A/Puerto Rico/8/34 (H1N1) (PR8) by measuring multiple lipid molecular species using untargeted lipidomic analysis. C57BL/6 male mice were intranasally infected with PR8 virus at 50 or 500 plaque-forming units to cause sublethal or lethal influenza, respectively. Plasma and tissue samples were collected at 1, 3, and 6 days post-infection (dpi), and comprehensive lipidomic analysis was performed using high-performance liquid chromatography-linear trap quadrupole-Orbitrap mass spectrometry, as well as gene expression analyses. The most prominent feature of the lipid profile in lethally infected mice was the elevated plasma concentrations of phosphatidylethanolamines (PEs) containing polyunsaturated fatty acid (PUFA) at 3 dpi. Furthermore, the facilitation of PUFA-containing phospholipid production in the lungs, but not in the liver, was suggested by gene expression and lipidomic analysis of tissue samples. Given the increased plasma or serum levels of PUFA-containing PEs in patients with other viral infections, especially in severe cases, the elevation of these phospholipids in circulation could be a biomarker of infection and the severity of infectious diseases.

Lipid Composition Analysis and Characterization of Acyl Sterol Glycosides in Adzuki and Soybean Cultivars by Non-Targeted LC-MS.

Beans, a globally significant economic and nutritional food crop, are rich in polyphenolic chemicals with potential health advantages, providing high protein, fiber, minerals, and vitamins. However, studies on the global profiling of lipids in beans are limited. We applied a non-targeted lipidomic approach based on high-performance liquid chromatography coupled with linear ion trap-Orbitrap mass spectrometry (HPLC/LTQ-Orbitrap-MS) to comprehensively profile and compare the lipids in six distinct bean cultivars, namely, adzuki red beans-adzuki cultivar (ARB-AC), adzuki red beans-Benidainagon cultivar (ARB-BC), adzuki red beans-Erimoshouzu cultivar (ARB-EC), soybean-Fukuyutaka cultivar 2021 (SB-FC21), soybean-Fukuyutaka cultivar 2022 (SB-FC22), and soybean-Oosuzu cultivar (SB-OC). MS/MS analysis defined 144 molecular species from four main lipid groups. Multivariate principal component analysis indicated unique lipid compositions in the cultivars except for ARB-BC and ARB-EC. Evaluation of the concentrations of polyunsaturated fatty acid to saturated fatty acid ratio among all the cultivars showed that SB-FC21 and SB-FC22 had the highest value, suggesting they are the most beneficial for health. Furthermore, lipids such as acyl sterol glycosides were detected and characterized for the first time in these bean cultivars. Hierarchical cluster correlations revealed the predominance of ceramides in ARB-EC, lysophospholipids in SB-FC21, and glycerophospholipids in SB-OC. This study comprehensively investigated lipids and their compositions in beans, indicating their potential utility in the nutritional evaluation of beans as functional foods.

A Pacific Oyster-Derived Antioxidant, DHMBA, Protects Renal Tubular HK-2 Cells against Oxidative Stress via Reduction of Mitochondrial ROS Production and Fragmentation.

The kidney contains numerous mitochondria in proximal tubular cells that provide energy for tubular secretion and reabsorption. Mitochondrial injury and consequent excessive reactive oxygen species (ROS) production can cause tubular damage and play a major role in the pathogenesis of kidney diseases, including diabetic nephropathy. Accordingly, bioactive compounds that protect the renal tubular mitochondria from ROS are desirable. Here, we aimed to report 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA), isolated from the Pacific oyster (Crassostrea gigas) as a potentially useful compound. In human renal tubular HK-2 cells, DHMBA significantly mitigated the cytotoxicity induced by the ROS inducer L-buthionine-(S, R)-sulfoximine (BSO). DHMBA reduced the mitochondrial ROS production and subsequently regulated mitochondrial homeostasis, including mitochondrial biogenesis, fusion/fission balance, and mitophagy; DHMBA also enhanced mitochondrial respiration in BSO-treated cells. These findings highlight the potential of DHMBA to protect renal tubular mitochondrial function against oxidative stress.

Sleep deprivation in obesogenic setting alters lipidome and microbiome toward suboptimal inflammation in acute heart failure.

Sleep is a fundamental medicine for cardiac homeostasis, and sleep-deprived individuals are prone to higher incidences of heart attack. The lipid-dense diet (obesogenic diet-OBD) is a cumulative risk factor for chronic inflammation in cardiovascular disease; thus, understanding how sleep fragmentation (SF) in an obesity setting impacts immune and cardiac health is an unmet medical need. We hypothesized whether the co-existence of SF with OBD dysregulates gut homeostasis and leukocyte-derived reparative/resolution mediators, thereby impairing cardiac repair. Two-month-old male C57BL/6J mice were randomized first into two groups, then four groups; Control, control + SF, OBD, and OBD + SF mice subjected to myocardial infarction (MI). OBD mice had higher levels of plasma linolenic acid with a decrease in eicosapentaenoic and docosahexaenoic acid. The OBD mice had lower Lactobacillus johnsonii indicating a loss of probiotic microbiota. SF in OBD mice increased Firmicutes/Bacteroidetes ratio indicative of a detrimental change in SF-directed microbiome. OBD + SF group increased in the neutrophil: lymphocyte ratio suggestive of suboptimal inflammation. As a result of SF, resolution mediators (RvD2, RvD3, RvD5, LXA4 , PD1, and MaR1) decreased and inflammatory mediators (PGD2 , PGE2 , PGF2a , 6k-PGF1a ) were increased in OBD mice post-MI. At the site of infarction, the proinflammatory cytokines Ccl2, IL1ß, and IL-6 were amplified in OBD + SF indicating a robust proinflammatory milieu post-MI. Also, brain circadian genes (Bmal1, Clock) were downregulated in SF-subjected control mice, but remained elevated in OBD mice post-MI. SF superimposed on obesity dysregulated physiological inflammation and disrupted resolving response thereby impaired cardiac repair and signs of pathological inflammation.

Mass spectrometric approaches in discovering lipid biomarkers for COVID-19 by lipidomics: Future challenges and perspectives.

Coronavirus disease 2019 (COVID-19) has emerged as a global health threat and has rapidly spread worldwide. Significant changes in the lipid profile before and after COVID-19 confirmed the significance of lipid metabolism in regulating the response to viral infection. Therefore, understanding the role of lipid metabolism may facilitate the development of new therapeutics for COVID-19. Owing to their high sensitivity and accuracy, mass spectrometry (MS)-based methods are widely used for rapidly identifying and quantifying of thousands of lipid species present in a small amount of sample. To enhance the capabilities of MS for the qualitative and quantitative analysis of lipids, different platforms have been combined to cover a wide range of lipidomes with high sensitivity, specificity, and accuracy. Currently, MS-based technologies are being established as efficient methods for discovering potential diagnostic biomarkers for COVID-19 and related diseases. As the lipidome of the host cell is drastically affected by the viral replication process, investigating lipid profile alterations in patients with COVID-19 and targeting lipid metabolism pathways are considered to be crucial steps in host-directed drug targeting to develop better therapeutic strategies. This review summarizes various MS-based strategies that have been developed for lipidomic analyzes and biomarker discoveries to combat COVID-19 by integrating various other potential approaches using different human samples. Furthermore, this review discusses the challenges in using MS technologies and future perspectives in terms of drug discovery and diagnosis of COVID-19.

Oxidized Low-Density Lipoproteins Trigger Hepatocellular Oxidative Stress with the Formation of Cholesteryl Ester Hydroperoxide-Enriched Lipid Droplets.

Oxidized low-density lipoproteins (oxLDLs) induce oxidative stress in the liver tissue, leading to hepatic steatosis, inflammation, and fibrosis. Precise information on the role of oxLDL in this process is needed to establish strategies for the prevention and management of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). Here, we report the effects of native LDL (nLDL) and oxLDL on lipid metabolism, lipid droplet formation, and gene expression in a human liver-derived C3A cell line. The results showed that nLDL induced lipid droplets enriched with cholesteryl ester (CE) and promoted triglyceride hydrolysis and inhibited oxidative degeneration of CE in association with the altered expression of LIPE, FASN, SCD1, ATGL, and CAT genes. In contrast, oxLDL showed a striking increase in lipid droplets enriched with CE hydroperoxides (CE-OOH) in association with the altered expression of SREBP1, FASN, and DGAT1. Phosphatidylcholine (PC)-OOH/PC was increased in oxLDL-supplemented cells as compared with other groups, suggesting that oxidative stress increased hepatocellular damage. Thus, intracellular lipid droplets enriched with CE-OOH appear to play a crucial role in NAFLD and NASH, triggered by oxLDL. We propose oxLDL as a novel therapeutic target and candidate biomarker for NAFLD and NASH.