Β-oxidation Activity Research Articles

7097 The role of mitochondrial fraction locating cytoplasmic and peridroplet area in white adipocyte

Abstract Disclosure: I. Mori: None. T. Ishizuka: None. H. Morita: None. K. Kajita: None. White adipocytes (WAs) are involved in the formation of obesity and insulin resistance, but little is known about the role of WAs mitochondria. A recent study revealed that the mitochondria of brown adipocytes (BAs) consist of cytoplasmic mitochondria CM), which is responsible for β-oxidation, and peridroplet mitochondria (PDM), which supplies triglyceride to lipid droplets. However, it is unclear whether such a functional division exist in WA mitochondria. In this study, we examined whether the pellets obtained from cytoplasmic and oil layers of WAs of C57/BL/J mice by centrifugation were mitochondria. Since mitochondrial DNA, mitochondrial protein, Mitotracker Red staining, and mitochondrial images in electron microscope were detected in both fractions, they were considered to be cytoplasmic mitochondria (CMw) and peridroplet mitochondria (PDMw) in WAs, respectively. The amount of CMw and PDMw were greater in epididymal fat than in inguinal fat. CMw had higher β-oxidation activity than PDMw. PDMw was associated with perilipin 1/3 and diacylglycerol acyltransferase 2. The amount of PDMw was elevated in epididymal fat of mice fed a high-fat diet (HFD) for 2 and 4 weeks compared to normal chew-fed mice. These results suggested that CMw was involved in β-oxidation, and PDMw in droplet expansion. Although numerous researches have been shown that amount of mitochondria is suppressed in obese WAs, our results revealed that PDMw might be involved in the early stage of obesity formation. Presentation: 6/1/2024

Endogenous activation of peroxisome proliferator-activated receptor-α in proximal tubule cells in counteracting phosphate toxicity.

Increased dietary phosphate consumption intensifies renal phosphate burden. Several mechanisms for phosphate-induced renal tubulointerstitial fibrosis have been reported. Considering the dual nature of phosphate as both a potential renal toxin and an essential nutrient for the body, kidneys may possess inherent protective mechanisms against phosphate overload, rather than succumbing solely to injury. However, there is limited understanding of such mechanisms. To identify these mechanisms, we conducted single-cell RNA sequencing (scRNA-seq) analysis of the kidneys of control and dietary phosphate-loaded (Phos) mice at a time point when the Phos group had not yet developed tubulointerstitial fibrosis. scRNA-seq analysis identified the highest number of differentially expressed genes in the clusters belonging to proximal tubular epithelial cells (PTECs). Based on these differentially expressed genes, in silico analyses suggested that the Phos group activated peroxisome proliferator-activated receptor-α (PPAR-α) and fatty acid β-oxidation (FAO) in the PTECs. This activation was further substantiated through various experiments, including the use of an FAO activity visualization probe. Compared with wild-type mice, Ppara knockout mice exhibited exacerbated tubulointerstitial fibrosis in response to phosphate overload. Experiments conducted with cultured PTECs demonstrated that activation of the PPAR-α/FAO pathway leads to improved cellular viability under high-phosphate conditions. The Phos group mice showed a decreased serum concentration of free fatty acids, which are endogenous PPAR-α agonists. Instead, experiments using cultured PTECs revealed that phosphate directly activates the PPAR-α/FAO pathway. These findings indicate that noncanonical metabolic reprogramming via endogenous activation of the PPAR-α/FAO pathway in PTECs is essential to counteract phosphate toxicity.NEW & NOTEWORTHY This study revealed the activation of peroxisome proliferator-activated receptor-α and fatty acid β-oxidation in proximal tubular epithelial cells as an endogenous mechanism to protect the kidney from phosphate toxicity. These findings highlight noncanonical metabolic reprogramming as a potential target for suppressing phosphate toxicity in the kidneys.

Tamoxifen upregulates the peroxisomal β-oxidation enzyme Enoyl CoA hydratase and 3-hydroxyacyl CoA hydratase ameliorating hepatic lipid accumulation in mice

Tamoxifen is an estrogen receptor modulator that has been reported to alleviate hepatic lipid accumulation in mice, but the mechanism is still unclear. Peroxisome fatty acid β-oxidation is the main metabolic pathway for the overload of long-chain fatty acids. As long-chain fatty acids are a cause of hepatic lipid accumulation, the activation of peroxisome fatty acid β-oxidation might be a novel therapeutic strategy for metabolic associated fatty liver disease. In this study, we investigated the mechanism of tamoxifen against hepatic lipid accumulation based on the activation of peroxisome fatty acid β-oxidation. Tamoxifen reduced liver long-chain fatty acids and relieved hepatic lipid accumulation in high fat diet mice without sex difference. In vitro, tamoxifen protected primary hepatocytes against palmitic acid-induced lipotoxicity. Mechanistically, the RNA-sequence of hepatocytes isolated from the liver revealed that peroxisome fatty acid β-oxidation was activated by tamoxifen. Protein and mRNA expression of enoyl CoA hydratase and 3-hydroxyacyl CoA hydratase were significantly increased in vivo and in vitro. Small interfering RNA enoyl CoA hydratase and 3-hydroxyacyl CoA hydratase in primary hepatocytes abolished the therapeutic effects of tamoxifen in lipid accumulation. In conclusion, our results indicated that tamoxifen could relieve hepatic lipid accumulation in high fat diet mice based on the activation of enoyl CoA hydratase and 3-hydroxyacyl CoA hydratase-mediated peroxisome fatty acids β-oxidation.

Oxidized-LDL Induces Metabolic Dysfunction in Retinal Pigment Epithelial Cells.

Recently, mitochondrial dysfunction has gained attention as a causative factor in the pathogenesis and progression of age-related macular degeneration (AMD). Mitochondrial damage plays a key role in metabolism and disrupts the balance of intracellular metabolic pathways, such as oxidative phosphorylation (OXPHOS) and glycolysis. In this study, we focused on oxidized low-density lipoprotein (ox-LDL), a major constituent of drusen that accumulates in the retina of patients with AMD, and investigated whether it could be a causative factor for metabolic alterations in retinal pigment epithelial (RPE) cells. We found that prolonged exposure to ox-LDL induced changes in fatty acid β-oxidation (FAO), OXPHOS, and glycolytic activity and increased the mitochondrial reactive oxygen species production in RPE cells. Notably, the effects on metabolic alterations varied with the concentration and duration of ox-LDL treatment. In addition, we addressed the limitations of using ARPE-19 cells for retinal disease research by highlighting their lower barrier function and FAO activity compared to those of induced pluripotent stem cell-derived RPE cells. Our findings can aid in the elucidation of mechanisms underlying the metabolic alterations in AMD.

Microaerobic insights into production of polyhydroxyalkanoates containing 3-hydroxyhexanoate via native reverse β-oxidation from glucose in Ralstonia eutropha H16

BackgroundRalstonia eutropha H16, a facultative chemolitoautotroph, is an important workhorse for bioindustrial production of useful compounds such as polyhydroxyalkanoates (PHAs). Despite the extensive studies to date, some of its physiological properties remain not fully understood.ResultsThis study demonstrated that the knallgas bacterium exhibited altered PHA production behaviors under slow-shaking condition, as compared to its usual aerobic condition. One of them was a notable increase in PHA accumulation, ranging from 3.0 to 4.5-fold in the mutants lacking of at least two NADPH-acetoacetyl-CoA reductases (PhaB1, PhaB3 and/or phaB2) when compared to their respective aerobic counterpart, suggesting the probable existence of (R)-3HB-CoA-providing route(s) independent on PhaBs. Interestingly, PHA production was still considerably high even with an excess nitrogen source under this regime. The present study further uncovered the conditional activation of native reverse β-oxidation (rBOX) allowing formation of (R)-3HHx-CoA, a crucial precursor for poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)], solely from glucose. This native rBOX led to the natural incorporation of 3.9 mol% 3HHx in a triple phaB-deleted mutant (∆phaB1∆phaB1∆phaB2-C2). Gene deletion experiments elucidated that the native rBOX was mediated by previously characterized (S)-3HB-CoA dehydrogenases (PaaH1/Had), β-ketothiolase (BktB), (R)-2-enoyl-CoA hydratase (PhaJ4a), and unknown crotonase(s) and reductase(s) for crotonyl-CoA to butyryl-CoA conversion prior to elongation. The introduction of heterologous enzymes, crotonyl-CoA carboxylase/reductase (Ccr) and ethylmalonyl-CoA decarboxylase (Emd) along with (R)-2-enoyl-CoA hydratase (PhaJ) aided the native rBOX, resulting in remarkably high 3HHx composition (up to 37.9 mol%) in the polyester chains under the low-aerated condition.ConclusionThese findings shed new light on the robust characteristics of Ralstonia eutropha H16 and have the potential for the development of new strategies for practical P(3HB-co-3HHx) copolyesters production from sugars under low-aerated conditions.Graphical

Mechanisms of hepatic steatosis in chickens: integrated analysis of the host genome, molecular phenomics and gut microbiome.

Hepatic steatosis is the initial manifestation of abnormal liver functions and often leads to liver diseases such as nonalcoholic fatty liver disease in humans and fatty liver syndrome in animals. In this study, we conducted a comprehensive analysis of a large chicken population consisting of 705 adult hens by combining host genome resequencing; liver transcriptome, proteome, and metabolome analysis; and microbial 16S ribosomal RNA gene sequencing of each gut segment. The results showed the heritability (h2 = 0.25) and duodenal microbiability (m2 = 0.26) of hepatic steatosis were relatively high, indicating a large effect of host genetics and duodenal microbiota on chicken hepatic steatosis. Individuals with hepatic steatosis had low microbiota diversity and a decreased genetic potential to process triglyceride output from hepatocytes, fatty acid β-oxidation activity, and resistance to fatty acid peroxidation. Furthermore, we revealed a molecular network linking host genomic variants (GGA6: 5.59-5.69 Mb), hepatic gene/protein expression (PEMT, phosphatidyl-ethanolamine N-methyltransferase), metabolite abundances (folate, S-adenosylmethionine, homocysteine, phosphatidyl-ethanolamine, and phosphatidylcholine), and duodenal microbes (genus Lactobacillus) to hepatic steatosis, which could provide new insights into the regulatory mechanism of fatty liver development.

Moderate replacement of fish oil with palmitic acid-stimulated mitochondrial fusion promotes β-oxidation by Mfn2 interacting with Cpt1α via its GTPase-domain

The mitochondrial matrix serves as the principal locale for the process of fatty acids (FAs) β-oxidation. Preserving the integrity and homeostasis of mitochondria, which is accomplished through ongoing fusion and fission events, is of paramount importance for the effective execution of FAs β-oxidation. There has been no investigation to date into whether and how mitochondrial fusion directly enhances FAs β-oxidation. The underlying mechanism of a balanced FAs ratio favoring hepatic lipid homeostasis remains largely unclear. To address such gaps, the present study was conducted to investigate the mechanism through which a balanced dietary FAs ratio enhances hepatic FAs β-oxidation. The investigation specifically focused on the involvement of Mfn2-mediated mitochondrial fusion in the regulation of Cpt1α in this process. In the present study, the yellow catfish (Pelteobagrus fulvidraco), recognized as a model organism for lipid metabolism, were subjected to eight weeks of in vivo feeding with six distinct diets featuring varying FAs ratios. Additionally, in vitro experiments were conducted to inhibit Mfn2-mediated mitochondrial fusion in isolated hepatocytes, achieved through the transfection of hepatocytes with si-mfn2. Further, deletion mutants for both Mfn2 and Cpt1α were constructed to elucidate the critical regions responsible for the interactions between these two proteins within the system. The key findings were: (1) Substituting palmitic acid (PA) for fish oil (FO) proved to be enhanced in reducing hepatic lipid accumulation. This beneficial effect was primarily attributed to the activation of mitochondrial FAs β-oxidation; (2) The balanced replacement of PA stimulated Mfn2-mediated mitochondrial fusion by diminishing Mfn2 ubiquitination, thereby enhancing its protein retention within the mitochondria; (3) Mfn2-mediated mitochondrial fusion promoted FAs β-oxidation through direct interaction between Mfn2 and Cpt1α via its GTPase-domains, which is essential for the maintenance of Cpt1 activity. Notably, the present research results unveil a previously undisclosed mechanism wherein Mfn2-mediated mitochondrial fusion promotes FAs β-oxidation by directly augmenting the capacity for FA transport into mitochondria (MT), in addition to expanding the mitochondrial matrix. This underscores the pivotal role of mitochondrial fusion in preserving hepatic lipid homeostasis. The present results further confirm that these mechanisms are evolutionarily conserved, extending their relevance from fish to mammals.

Ingestion of triglycerides containing medium- and long-chain fatty acids can increase metabolism of ingested long-chain triglycerides in overweight persons.

Medium-chain fatty acids (MCFAs) have attracted considerable attention for preventing or improving obesity, which is a recognized risk factor for lifestyle-related diseases. Medium- and long-chain triglycerides (MLCTs) are expected to improve the metabolism of ingested long-chain triglycerides (LCTs). However, previous studies have reported mixed results. In this study, the effect of ingestion of MLCTs was evaluated on the metabolism of LCTs and compared to the ingestion of rapeseed oil (control oil). A randomized, double-blind, placebo-controlled crossover study was performed among sedentary participants with BMIs ranging from 25 below 30 kg/m2. Thirty participants were asked to ingest either 14 g of MLCTs or a control oil for 4 weeks. The metabolism of ingested LCTs was evaluated by measuring isotopically labeled carbon dioxide released by the degradation of carbon-13 (13C)-labeled LCTs. Ingestion of MLCTs markedly enhanced the metabolism of ingested LCTs by comparison to the control oil. The findings of this study suggest that ingestion of MLCTs may enhance the metabolism of dietary LCTs through activation of β-oxidation in liver mitochondria, which may increase the metabolic kinetics of ingested long-chain fatty acid (LCFAs). https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000053101, identifier: UMIN000046604.

Activation of Fatty Acid β-Oxidation in Proximal Tubular Epithelial Cells Is an Intrinsic Mechanism for Suppressing Phosphorus-Induced Kidney Injury

Activation of Fatty Acid β-Oxidation in Proximal Tubular Epithelial Cells Is an Intrinsic Mechanism for Suppressing Phosphorus-Induced Kidney Injury

Docosahexaenoic acid (DHA) alleviates hepatic lipid accumulation by regulating mitochondrial quality control through ERK signaling pathway in grass carp (Ctenopharyngodon idellus)

Docosahexaenoic acid (DHA) alleviates hepatic lipid accumulation in fish, but the underlying mechanism remains unclear. Studies in mammals showed that promoting fatty acid (FA) β-oxidation, which mainly occurs in mitochondrion, improves lipid accumulation. This study aims to investigate the effect of DHA on fatty acid (FA) β-oxidation, focusing on the role of hepatic mitochondrial quality control (MQC) and mitochondrial function, in grass carp (Ctenopharyngodon idellus) in vivo and in vitro. Grass carps (41.87 ± 0.08 g) were fed with diets supplemented with 0% (control) and 1% DHA for 8 weeks. Dietary 1% DHA markedly decreased the hepatosomatic index, hepatic triglyceride (TG) content, and serum TG (P < 0.05). Dietary 1% DHA significantly increased pparα and cpt1 mRNAs, which implies the activated FA β-oxidation. In addition, dietary 1% DHA improved mitochondrial function by increasing the ATP content and antioxidant ability. The mRNAs encoding DRP1, OPA1, MFN1 and MFN2 were significantly increased by DHA (P < 0.05), suggesting that mitochondrial division and fusion were activated simultaneously. Transmission electron microscopy displayed that dietary 1% DHA triggers the increase of mitochondria. Along with this, mitochondrial DNA copy numbers and the mRNA expression of pgc1α, tfam and nrf1 were significantly increased in 1% DHA group (P < 0.05), suggesting that DHA activated mitochondrial biogenesis. BNIP3/NIX-dependent mitophagy was also induced by DHA. Consistent with these in vivo results, DHA restored the loss of ATP content, mitochondrial membrane potential, and antioxidant ability in palmitic acid (PA)-treated hepatocytes in vitro, implying that DHA improved the MQC network damaged by PA. DHA further activated FA β-oxidation and inhibited lipid accumulation in the hepatocytes. Importantly, U0126, an inhibitor of ERK, abrogated the effects of DHA on the MQC network and lipid metabolism. Taken together, the present study demonstrated that the alleviation of hepatic lipid accumulation by DHA is mediated by the activation of FA β-oxidation and improvement of MQC via the ERK pathway. This study may shed light on the molecular mechanism underlying DHA's function in relieving hepatic lipid deposition in vertebrates.

CLPX regulates mitochondrial fatty acid β-oxidation in liver cells

Mitochondrial fatty acid oxidation (β-oxidation) is an essential metabolic process for energy production in eukaryotic cells, but the regulatory mechanisms of this pathway are largely unknown. In the present study, we found that several enzymes involved in β-oxidation are associated with CLPX, the AAA+ unfoldase that is a component of the mitochondrial matrix protease ClpXP. The suppression of CLPX expression increased β-oxidation activity in the HepG2 cell line and in primary human hepatocytes without glucagon treatment. However, the protein levels of enzymes involved in β-oxidation did not significantly increase in CLPX-deleted HepG2 cells (CLPX-KO cells). Coimmunoprecipitation experiments revealed that the protein level in the immunoprecipitates of each antibody changed after the treatment of WT cells with glucagon, and a part of these changes was also observed in the comparison of WT and CLPX-KO cells without glucagon treatment. Although the exogenous expression of WT or ATP-hydrolysis mutant CLPX suppressed β-oxidation activity in CLPX-KO cells, glucagon treatment induced β-oxidation activity only in CLPX-KO cells expressing WT CLPX. These results suggest that the dissociation of CLPX from its target proteins is essential for the induction of β-oxidation in HepG2 cells. Moreover, specific phosphorylation of AMP-activated protein kinase and a decrease in the expression of acetyl-CoA carboxylase 2 were observed in CLPX-KO cells, suggesting that CLPX might participate in the regulation of the cytosolic signaling pathway for β-oxidation. The mechanism for AMP-activated protein kinase phosphorylation remains elusive; however, our results uncovered the hitherto unknown role of CLPX in mitochondrial β-oxidation in human liver cells.

Characteristics of Mycobacterium tuberculosis PtpA interaction and activity on the alpha subunit of human mitochondrial trifunctional protein, a key enzyme of lipid metabolism.

During Mycobacterium tuberculosis (Mtb) infection, the virulence factor PtpA belonging to the protein tyrosine phosphatase family is delivered into the cytosol of the macrophage. PtpA interacts with numerous eukaryotic proteins modulating phagosome maturation, innate immune response, apoptosis, and potentially host-lipid metabolism, as previously reported by our group. In vitro, the human trifunctional protein enzyme (hTFP) is a bona fide PtpA substrate, a key enzyme of mitochondrial β-oxidation of long-chain fatty acids, containing two alpha and two beta subunits arranged in a tetramer structure. Interestingly, it has been described that the alpha subunit of hTFP (ECHA, hTFPα) is no longer detected in mitochondria during macrophage infection with the virulent Mtb H37Rv. To better understand if PtpA could be the bacterial factor responsible for this effect, in the present work, we studied in-depth the PtpA activity and interaction with hTFPα. With this aim, we performed docking and in vitro dephosphorylation assays defining the P-Tyr-271 as the potential target of mycobacterial PtpA, a residue located in the helix-10 of hTFPα, previously described as relevant for its mitochondrial membrane localization and activity. Phylogenetic analysis showed that Tyr-271 is absent in TFPα of bacteria and is present in more complex eukaryotic organisms. These results suggest that this residue is a specific PtpA target, and its phosphorylation state is a way of regulating its subcellular localization. We also showed that phosphorylation of Tyr-271 can be catalyzed by Jak kinase. In addition, we found by molecular dynamics that PtpA and hTFPα form a stable protein complex through the PtpA active site, and we determined the dissociation equilibrium constant. Finally, a detailed study of PtpA interaction with ubiquitin, a reported PtpA activator, showed that additional factors are required to explain a ubiquitin-mediated activation of PtpA. Altogether, our results provide further evidence supporting that PtpA could be the bacterial factor that dephosphorylates hTFPα during infection, potentially affecting its mitochondrial localization or β-oxidation activity.

WED-518 - Opposite correlations between hepatic β-oxidation activity and triglyceride levels in male and female rats after a high-fat diet supplemented with liquid fructose

WED-518 - Opposite correlations between hepatic β-oxidation activity and triglyceride levels in male and female rats after a high-fat diet supplemented with liquid fructose

Abstract P6-11-11: Breast cancer stem cell marker, CD24 regulates metabolic reprogramming in triple negative breast cancer

Abstract Breast cancer stem cell (BCSC) is a subset of cancer cells that can dictate the tumor initiation, metastatic progression, and therapeutic resistance in BC. The eradication of this unusual population is emerging as a new paradigm in cancer treatment. Molecularly, CD24 negativity in conjunction with high expression of CD44 is considered a hallmark for the BCSCs. While extensive studies have been performed to delineate the role of CD44 in BCSCs, the regulation of CD24 and its functional role have not been fully understood. In this study, we investigated the regulatory mechanisms responsible for low CD24 expression in BCSCs and their functional relevance in BCSCs. Analysis of DNA from tumor tissues and blood from BC patients as well as BCSCs sorted from BC cell lines suggest that CD24 is epigenetically regulated via DNMT-1/HDAC1-dependent increased methylation of CpG islands in the CD24 proximal promoter region. To understand the role of CD24 in triple-negative BC (TNBC), an aggressive subgroup of BC, we knocked down (CD24-KD) and overexpressed (CD24-OE) CD24 in metastatic TNBC cells. While CD24-KD resulted in increased proliferation and stemness, CD24-OE diminished the proliferative and stem-like potential. To further identify the signaling cascade underpinning these effects, we performed phospho-proteome analysis using Reverse Phase Protein Array (RPPA). Remarkably, we observed an enhanced activation of AMPK and NF-kB signaling cascades, and reduced PDGFRβ signaling upon depletion of CD24. As signaling cascades are intricately linked to cellular metabolism, we performed a metabolomic analysis of CD24-KD and CD24-OE cells. Our comprehensive analysis revealed heightened activation of mitochondrial fatty acid β-oxidation (FAO) in CD24-KD and increased glutamine metabolism in CD24-OE cells. In coherence with these findings, we observed significant regulation of genes related to fatty acid metabolism in the TNBC patient cohort expressing low levels of CD24. Consistently, the CD24-KD cells demonstrated increased sensitivity towards FAO inhibitors while CD24-OE cells were more sensitive to glutamine metabolism inhibitors. In vivo studies to further understand the translational significance of this metabolic axis is underway. Taken together, our study demonstrates, for the first time, that CD24 presents a novel metabolic vulnerability that can target BCSCs to gain a therapeutic advantage in the treatment of drug-resistant TNBC patients. Citation Format: Divya Murthy, Debasmita Dutta, Sukjin Yang, Junhyoung Park, Benny Kaipparettu. Breast cancer stem cell marker, CD24 regulates metabolic reprogramming in triple negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-11-11.

Establishment of hyperoxic cell culture system for predicting drug-induced liver injury: reducing accumulated lipids in hepatocytes derived from chimeric mice with humanized liver.

Drug-induced liver injury (DILI) is a major adverse reaction. Species-specific differences between humans and laboratory animals make it difficult to establish evaluation models that can accurately predict DILI in the preclinical phase. Chimeric mice with humanized liver are potential predictive models for understanding DILI. Chimeric mice generated by transplanting human hepatocytes into urokinase-type plasminogen activator/severe combined immunodeficient mice are known to develop fatty liver and show lipid accumulation in isolated hepatocytes. It is speculated that the lipids accumulated in hepatocytes may interfere with DILI assessment. It is known that normal 20% oxygen culture conditions do not meet oxygen demand because oxygen consumption rate is higher than the oxygen supply rate. Therefore, we predicted that hyperoxic cultures could induce hepatocyte function and reduce accumulated lipids. A culture of chimeric mouse hepatocytes in 40% oxygen showed reduced intracellular lipid and triglyceride levels compared to those cultured in 20% oxygen on days 7 and 10. In addition, fatty acid β-oxidation (FAO) activity increased from day 7 under 40% oxygen conditions. On the other hand, FAO activity increased on day 10 under 20% conditions. Microarray and Ingenuity Pathway Analysis showed that lipid metabolism-related pathways were downregulated under 40% oxygen conditions for 7 days, suggesting the involvement of several mechanisms in decreasing lipid levels and increasing FAO. Furthermore, some pathways related to cellular function and maintenance were upregulated under 40% oxygen conditions for 7 days. In conclusion, chimeric mouse hepatocytes cultured under hyperoxic conditions may be useful for predicting DILI.

Litchi flower essential oil balanced lipid metabolism through the regulation of DAF-2/IIS, MDT-15/SBP-1, and MDT-15/NHR-49 pathway.

Many litchi flowers are discarded in China every year. The litchi flower is rich in volatile compounds and exhibits strong anti-obesity activity. Litchi flower essential oil (LFEO) was extracted by the continuous phase transformation device (CPTD) independently developed by our research group to recycle the precious material resources in litchi flowers. However, its fat-reducing effect and mechanism remain unclear. Employing Caenorhabditis elegans as a model, we found that LFEO significantly reduced fat storage and triglyceride (TG) content in normal, glucose-feeding, and high-fat conditions. LFEO significantly reduced body width in worms and significantly decreased both the size and number of lipid droplets in ZXW618. LFEO treatment did not affect energy intake but increased energy consumption by enhancing the average speed of worms. Further, LFEO might balance the fat metabolism in worms by regulating the DAF-2/IIS, sbp-1/mdt-15, and nhr-49/mdt-15 pathways. Moreover, LFEO might inhibit the expression of the acs-2 gene through nhr-49 and reduce β-oxidation activity. Our study presents new insights into the role of LFEO in alleviating fat accumulation and provides references for the large-scale production of LFEO to promote the development of the litchi circular economy.

Protective Effect of Nopal Cactus (Opuntia ficus-indica) Seed Oil against Short-Term Lipopolysaccharides-Induced Inflammation and Peroxisomal Functions Dysregulation in Mouse Brain and Liver.

Exposure to endotoxins (lipopolysaccharides, LPS) may lead to a potent inflammatory cytokine response and a severe impairment of metabolism, causing tissue injury. The protective effect provided by cactus seed oil (CSO), from Opuntia ficus-indica, was evaluated against LPS-induced inflammation, dysregulation of peroxisomal antioxidant, and β-oxidation activities in the brain and the liver. In both tissues, a short-term LPS exposure increased the proinflammatory interleukine-1β (Il-1β), inducible Nitroxide synthase (iNos), and Interleukine-6 (Il-6). In the brain, CSO action reduced only LPS-induced iNos expression, while in the liver, CSO attenuated mainly the hepatic Il-1β and Il-6. Regarding the peroxisomal antioxidative functions, CSO treatment (as Olive oil (OO) or Colza oil (CO) treatment) induced the hepatic peroxisomal Cat gene. Paradoxically, we showed that CSO, as well as OO or CO, treatment can timely induce catalase activity or prevent its induction by LPS, respectively, in both brain and liver tissues. On the other hand, CSO (as CO) pretreatment prevented the LPS-associated Acox1 gene and activity decreases in the liver. Collectively, CSO showed efficient neuroprotective and hepato-protective effects against LPS, by maintaining the brain peroxisomal antioxidant enzyme activities of catalase and glutathione peroxidase, and by restoring hepatic peroxisomal antioxidant and β-oxidative capacities.

Integrated multiple-omics reveals the regulatory mechanism underlying the effects of artificial feed and grass feeding on growth and muscle quality of grass carp (Ctenopharyngodon idellus)

The muscle quality of farmed fish has attracted widespread public attention. To understand a comprehensive molecular mechanism underlying the effects of artificial formula feed- (AF) and grass-feeding (GF) on muscle quality and growth of grass carp (Ctenopharyngodon idellus), muscular transcriptomics and proteomics of GF and AF C. idellus were characterized. A total of 834 DEGs (484 up-, 350 down-regulated genes) and 487 DEPs (271 up- and 216 down-regulations) were identified between groups. Then, the functional enrichment analysis of DEGs & DEPs (DEs) and the integration of multiple-Omics (SDFs), further reflected that the stronger myofiber differentiation and protein synthesis capacities are likely the main strategy of more muscle mass gain in AF C. idellus, while the muscle growth in GF C. idellus is consequent to the stronger muscle cell proliferation and hypertrophy. Secondly, there was a significant difference in muscle fiber types between GF and AF groups, this has a noticeable effect on muscle tenderness and quality. In combination with previously metabolic results, we established DEG-DEP-SDM interaction network, which validated that the slow-MyHC-I fiber, dense in AF C. idellus muscles, accumulated more glycogen and exhibited more powerful glycolytic activity. Meanwhile, the suppressed activity of eIF2α in AF C. idellus muscles promoted protein synthesis, the “Ubiquitin mediated proteolysis” was simultaneously restrained. However, the activities of TCA cycle and fatty acid oxidation were significantly enhanced in GF muscles (rich in fast-MyHC-IIb). Accordingly, the up-regulated ACSL1, ACADS, ppara, etc. were quantified in GF C. idellus samples with stronger fatty acids β-oxidation activity, then led to the reduction of cellular triglycerides and lipid droplet formation. Additionally, our results also provide key information for further understanding of the molecular mechanisms (e.g. MAPK and PI3K signaling pathways, Necroptosis and so on) of C. idellus under dietary treatments. In summary, the grass-feeding could effectively alleviate the negative effects of AF on fish, namely, reducing fat deposition, improving nutrients, flavor and texture of muscle, relieving insulin resistance and stress tolerance, finally lead to better nourishing and healthy C. idellus.

Synthesized HMGB1 peptide prevents the progression of inflammation, steatosis, fibrosis, and tumor occurrence in a non-alcoholic steatohepatitis mouse model.

Non-alcoholic steatohepatitis (NASH) with fibrosis eventually leads to cirrhosis and hepatocellular carcinoma. Thus, the development of therapies other than dietary restriction and exercise, particularly those that suppress steatosis and fibrosis of the liver and have a long-term beneficial effect, is necessary. We aimed to evaluate the therapeutic effects of the HMGB1 peptide synthesized from box A using the melanocortin-4 receptor-deficient (Mc4r-KO) NASH model mouse. We performed short- and long-term administration of this peptide and evaluated the effects on steatosis, fibrosis, and carcinogenesis using Mc4r-KO mice. We also analyzed the direct effect of this peptide on macrophages and hepatic stellate cells in vitro and performed lipidomics and metabolomics techniques to evaluate the effect. Although this peptide did not show direct effects on macrophages and hepatic stellate cells in vitro, in the short-term administration model, we could confirm the reduction of liver damage, steatosis, and fibrosis progression. The results of lipidomics and metabolomics suggested that the peptide might ameliorate NASH by promoting lipolysis via the activation of fatty acid β-oxidation and improving insulin resistance. In the long-term administration model, this peptide prevented progression to cirrhosis but retained the steatosis state, that is, the peptide prevents the progression to "burnt-out NASH." This peptide inhibited carcinogenesis by about one-third. This HMGB1 peptide can reduce liver damage, improve fibrosis and steatosis, and inhibit carcinogenesis, suggesting that the peptide would be a new treatment candidate for NASH and can contribute to the long-term prognosis for patients with NASH.

Vitamin K2 Enhances Fat Degradation to Improve the Survival of C. elegans.

The beneficial effects of vitamin K (VK) on various chronic age-related syndromes have generally been considered dependent on its antioxidant effects. However, due to the distinct bioavailability and biological activities of VKs, exactly which of these activities and by what mechanisms they might act still need to be elucidated. In this study, we found that VK2 can extend the lifespan of C. elegans and improve the resistance to pathogen infection, heat stress and H2O2-induced inner oxidative stress. Importantly, the roles of VK2 on aging and stress resistance were shown to be dependent on enhanced fat metabolism and not due to its antioxidant effects. Moreover, the genes related to fat metabolism that were up-regulated following VK2 treatment play key roles in improving survival. Obesity is a leading risk factor for developing T2DM, and taking VKs has been previously considered to improve the insulin sensitivity associated with obesity and T2DM risk. However, our results showed that VK2 can significantly influence the expression of genes related to fat metabolism, including those that regulate fatty acid elongation, desaturation, and synthesis of fatty acid-CoA. VK2 enhanced the fatty acid β-oxidation activity in peroxisome to degrade and digest fatty acid-CoA. Our study implies that VK2 can enhance fat degradation and digestion to improve survival, supporting the effectiveness of VK2-based medical treatments. VK2 is mainly produced by gut bacteria, suggesting that VK2 might facilitate communication between the gut microbiota and the host intestinal cells to influence fat metabolism.