DGAT1-Dependent Lipid Droplet Biogenesis Protects Mitochondrial Function during Starvation-Induced Autophagy

JZL-184 Alleviate Neurological Impairment through Regulation of Mitochondrial Transfer and Lipid Droplet Accumulation after Cardiac Arrest

Astrocytes are abundant glial cells in the central nervous system (CNS) that play important roles in brain injury following cardiac arrest (CA). Following brain ischemia, astrocytes trigger endogenous neuroprotective mechanisms, such as fatty acid transport. Lipid droplets (LDs) are cellular structures involved in neutral lipid storage and play essential roles in many biological processes. However, whether lipid droplet metabolism is related to the neurological prognosis after CA remains unclear. JZL-184 is a selective irreversible inhibitor of monoacylglycerol lipase (MAGL), and previous investigations revealed that JZL-184 confers neuroprotection in the brain following stroke. However, further investigations are warranted to explore the effect and mechanism of JZL-184 after CA. Here, we reveal that JZL-184 is neuroprotective after cardiac arrest, as it alleviates astroglial activation by upregulating the expression of transforming growth factor beta 1 (TGF-β1), promotes the transfer of mitochondria from astrocytes to neurons in the astrocyte‒neuron coculture system, and reduces lipid droplet accumulation in neurons. Mechanistically, this protective effect depends on the downstream genes DUSP4 and Rab27b. This study provides additional insights into strategies for inhibiting neurological impairment and suggests a potential therapeutic target after cardiac arrest.

Rapamycin induced autophagy enhances lipid breakdown and ameliorates lipotoxicity in Atlantic salmon cells

Autophagy is a highly conserved cellular recycling process essential for homeostasis in all eukaryotic cells. Lipid accumulation and its regulation by autophagy are key areas of research for understanding metabolic disorders in human and model mammals. However, the role of autophagy in lipid regulation remains poorly characterized in non-model fish species of importance to food production, which could be important for managing health and welfare in aquaculture. Addressing this knowledge gap, we investigate the role of autophagy in lipid regulation using a macrophage-like cell line (SHK-1) from Atlantic salmon (Salmo salar L.), the world's most commercially valuable farmed finfish. Multiple lines of experimental evidence reveal that the autophagic pathway responsible for lipid droplet breakdown is conserved in Atlantic salmon cells. We employed global lipidomics and proteomics analyses on SHK-1 cells subjected to lipid overload, followed by treatment with rapamycin to induce autophagy. This revealed that activating autophagy via rapamycin enhances storage of unsaturated triacylglycerols and suppresses key lipogenic proteins, including fatty acid elongase 6, fatty acid binding protein 2 and acid sphingomyelinase. Moreover, fatty acid elongase 6 and fatty acid binding protein 2 were identified as possible cargo for autophagosomes, suggesting a critical role for autophagy in lipid metabolism in fish. Together, this study establishes a novel model of lipotoxicity and advances understanding of lipid autophagy in fish cells, with significant implications for addressing fish health issues in aquaculture.

TBC1D15 protects alcohol-induced liver injury in female mice through PLIN5-mediated mitochondrial and lipid droplet contacting

OBJECTIVE

Alcohol-induced hepatic steatosis and mitochondrial dysfunction are progressive conditions contributing to the development of alcoholic liver disease (ALD), often leading to cirrhosis and hepatocellular carcinoma. TBC1D15, a Rab7 GTPase-activating protein (GAP), has been implicated in mitochondrial homeostasis, however, its role in ALD remains elusive. This study aimed to investigate the functional role of TBC1D15 in ALD and elucidate the underlying mechanisms.

METHODS

Female TBC1D15flox/flox mice and hepatocyte-specific overexpression of TBC1D15 mice were fed a Lieber-DeCarli ethanol diet, which progressively increasing ethanol dosages over 8 weeks. Liver tissues were assessed using histology, transmission electron microscopy, immunofluorescence, immunoblotting, and real-time PCR techniques.

RESULTS

TBC1D15 levels were markedly decreased in human ALD samples and primary hepatocytes exposed to ethanol. Hepatocyte-specific TBC1D15 overexpression attenuated alcohol-induced body weight loss, improved survival, and alleviated liver injury, lipid droplet (LD) accumulation, and hepatocyte apoptosis. TBC1D15 overexpression also protected against alcohol-induced mitochondrial dysfunction and enhanced mitochondrial fatty acid β-oxidation (FAO) by promoting interactions between mitochondria and LDs in the face of alcohol exposure. Mechanistically, TBC1D15 was translocated to mitochondrial membranes in hepatocytes in response to alcohol exposure, where it recruited PLIN5 through its 10-180 aa domain. This interaction promoted mitochondria-LD contacts and facilitated PKA-induced nuclear translocation of PLIN5. Furthermore, TBC1D15 upregulated protein levels of PPARα, PGC1α and CPT1α in hepatocytes following alcohol challenge, an effect that was nullified by PKA inhibition.

CONCLUSION

TBC1D15 plays a promising protective role in ALD injury by enhancing mitochondrial function and FAO, potentially through its interaction with PLIN5 and modulation of mitochondria-LD contacts via PKA-mediated nuclear translocation of PLIN5. These findings identify TBC1D15 as a potential therapeutic target for ALD.

Lipid droplet - organelle crosstalk and its implication in cancer

Lipid droplets (LDs) store lipids in cells, provide phospholipids for membrane synthesis, and maintain the intracellular balance of energy and lipid metabolism. Undoubtedly, the crosstalk between LDs and other organelles is the foundation for performing functions. Many studies indicate that LDs promote tumor progression. LD accumulation has been observed in a variety of cancers, and high LD content is associated with malignant phenotype and poor prognosis of cancers. In this paper, we summarized the intimate crosstalk between LDs and intracellular organelles, including endoplasmic reticulum (ER), mitochondria, lysosomes and peroxisomes, and addressed the effects of LD-organelle crosstalk on cancer initiation and progression. We also integrated the changes of LD-organelle interactions in cancers to provide an insightful knowledge for cancer therapeutics.

Dietary fuel or fire: Fatty acids rewire gut ILC3s

Long-term consumption of diets high in fats has detrimental impacts on the immune system, but the window necessary for initiating these effects is unclear. In this issue of Immunity, Xiong et al.1 demonstrate that even short-term exposure to saturated fats impairs ILC3 function and renders the intestine vulnerable to inflammation and injury.

The perspective of modern transplant science - transplant arteriosclerosis: inspiration derived from mitochondria associated endoplasmic reticulum membrane dysfunction in arterial diseases

The mitochondria-associated endoplasmic reticulum membrane (MAM) is a crucial structure connecting mitochondria and the endoplasmic reticulum (ER), regulating intracellular calcium homeostasis, lipid metabolism, and various signaling pathways essential for arterial health. Recent studies highlight MAM's significant role in modulating vascular endothelial cells (EC) and vascular smooth muscle cells (VSMC), establishing it as a key regulator of arterial health and a contributor to vascular disease pathogenesis. Organ transplantation is the preferred treatment for end-stage organ failure, but transplant arteriosclerosis (TA) can lead to chronic transplant dysfunction, significantly impacting patient survival. TA, like other vascular diseases, features endothelial dysfunction and abnormal proliferation and migration of VSMC. Previous research on TA has focused on immune factors; the pathological and physiological changes in grafts following immune system attacks have garnered insufficient attention. For example, the potential roles of MAM in TA have not been thoroughly investigated. Investigating the relationship between MAM and TA, as well as the mechanisms behind TA progression, is essential. This review aims to outline the fundamental structure and the primary functions of MAM, summarize its key molecular regulators of vascular health, and explore future prospects for MAM in the context of TA research, providing insights for both basic research and clinical management of TA.

The Ways to Die: Cell Death in Liver Pathophysiology

Liver diseases are closely associated with various cell death mechanisms, including apoptosis, necroptosis, autophagy, pyroptosis, and ferroptosis. Each process contributes uniquely to the pathophysiology of liver injury and repair. Importantly, these mechanisms are not limited to hepatocytes; they also significantly involve nonparenchymal cells. This review examines the molecular pathways and regulatory mechanisms underlying these forms of cell death in hepatocytes, emphasizing their roles in several liver diseases, such as ischemia-reperfusion injury, metabolic dysfunction-associated steatotic liver disease, drug-induced liver injury, and alcohol-associated liver disease. Recent insights into ferroptosis and pyroptosis may reveal novel therapeutic targets for managing liver diseases. This review aims to provide a comprehensive overview of these cell death mechanisms in the context of liver diseases, detailing their molecular signaling pathways and implications for potential treatment strategies.

A hydrophobic photouncaging reaction to profile the lipid droplet interactome in tissues

Most bioorthogonal photouncaging reactions preferentially occur in polar environments to accommodate biological applications in the aqueous cellular milieu. However, they are not precisely designed to chemically adapt to the diverse microenvironments of the cell. Herein, we report a hydrophobic photouncaging reaction with tailored photolytic kinetics toward solvent polarity. Structural modulations of the aminobenzoquinone-based photocage reveal the impact of cyclic ring size, steric substituent, and electronic substituent on the individual uncaging kinetics (kH2O and kdioxane) and polarity preference (kdioxane/kH2O). Rational incorporation of optimized moieties leads to up to 20.2-fold nonpolar kinetic selectivity (kdioxane/kH2O). Further photochemical spectroscopic characterizations and theoretical calculations together uncover the mechanism underlying the polarity-dependent uncaging kinetics. The uncaged ortho-quinone methide product bears covalent reactivity toward diverse nucleophiles of a protein revealed by tandem mass spectrometry. Finally, we demonstrate the application of such lipophilic photouncaging chemistry toward selective labeling and profiling of proteins in proximity to lipid droplets inside human fatty liver tissues. Together, this work studies the solvent polarity effects of a photouncaging reaction and chemically adapts it toward suborganelle-targeted protein proximity labeling and profiling.

Mitochondria-organelle crosstalk in establishing compartmentalized metabolic homeostasis

Mitochondria serve as central hubs in cellular metabolism by sensing, integrating, and responding to metabolic demands. This integrative function is achieved through inter-organellar communication, involving the exchange of metabolites, lipids, and signaling molecules. The functional diversity of metabolite exchange and pathway interactions is enabled by compartmentalization within organelle membranes. Membrane contact sites (MCSs) are critical for facilitating mitochondria-organelle communication, creating specialized microdomains that enhance the efficiency of metabolite and lipid exchange. MCS dynamics, regulated by tethering proteins, adapt to changing cellular conditions. Dysregulation of mitochondrial-organelle interactions at MCSs is increasingly recognized as a contributing factor in the pathogenesis of multiple diseases. Emerging technologies, such as advanced microscopy, biosensors, chemical-biology tools, and functional genomics, are revolutionizing our understanding of inter-organellar communication. These approaches provide novel insights into the role of these interactions in both normal cellular physiology and disease states. This review will highlight the roles of metabolite transporters, lipid-transfer proteins, and mitochondria-organelle interfaces in the coordination of metabolism and transport.

Lipid metabolism analysis reveals that DGAT1 regulates Th17 survival by controlling lipid peroxidation in uveitis

Lipid metabolism is closely linked with antitumor immunity and autoimmune disorders. However, the precise role of lipid metabolism in uveitis pathogenesis is not clear. In our study, we analyzed the single-cell RNA-Seq (scRNA-Seq) data from cervical draining lymph nodes (CDLNs) of mice with experimental autoimmune uveitis (EAU), revealing an increased abundance of fatty acids in Th17 cells. Subsequent scRNA-Seq analysis identified the upregulation of DGAT1 expression in EAU and its marked reduction under various immunosuppressive agents. Suppression of DGAT1 prevented the conversion of fatty acids into neutral lipid droplets, resulting in the accumulation of lipid peroxidation and subsequent reduction in the proportion of Th17 cells. Inhibiting lipid peroxidation by Ferrostatin-1 effectively restored Th17 cell numbers that were decreased by DGAT1 inhibitor. Moreover, we validated the upregulation of DGAT1 in CD4+ T cells from patients with Vogt-Koyanagi-Harada (VKH) disease, a human uveitis. Inhibiting DGAT1 induced lipid peroxidation in human CD4+ T cells and reduced the proportion of Th17 cells. Collectively, our study focused on elucidating the regulatory mechanisms underlying Th17 cell survival and proposed that targeting DGAT1 may hold promise as a therapeutic approach for uveitis.

FATP1-mediated fatty acid uptake in renal tubular cells as a countermeasure for hypothermia

Hypothermia is a condition in which body temperature falls below 35 °C, resulting from exposure to low environmental temperatures or underlying medical conditions. Postmortem examinations have revealed increased levels of fatty acids in blood and lipid droplet formation in renal tubules during hypothermia. However, the causes and implications of these findings are unclear. This study aimed to analyze the biological significance of these phenomena through lipidomics and transcriptomics analyses of specimens from emergency hypothermia patients and mouse hypothermia models. Both human hypothermia patients and murine models exhibited elevated plasma concentrations of fatty acids and their derivatives compared with controls. Hypothermic mouse kidneys displayed lipid droplet formation, with gene expression analysis revealing enhanced fatty acid uptake and β-oxidation in renal tubular cells. In primary cultured mouse renal proximal tubular cells, low temperatures increased the expression levels of Fatty acid transport protein 1 (FATP1), a fatty acid transporter, and boosted oxygen consumption via β-oxidation. Mice treated with FATP1 inhibitors showed a more rapid decrease in body temperature upon exposure to low temperatures compared with untreated mice. In conclusion, increased fatty acid uptake mediated by FATP1 in renal tubular cells plays a protective role during hypothermia. KEY MESSAGES: Low temperatures increase FATP1 expression and fatty acid uptake in renal proximal tubular cells, resulting in enhanced β-oxidation. Renal proximal tubular cells play an important role in the resistance to hypothermia via lipid uptake. Maintaining renal lipid metabolism is essential for cold stress adaptation.

Metabolic reprogramming: a new option for the treatment of spinal cord injury

Spinal cord injuries impose a notably economic burden on society, mainly because of the severe after-effects they cause. Despite the ongoing development of various therapies for spinal cord injuries, their effectiveness remains unsatisfactory. However, a deeper understanding of metabolism has opened up a new therapeutic opportunity in the form of metabolic reprogramming. In this review, we explore the metabolic changes that occur during spinal cord injuries, their consequences, and the therapeutic tools available for metabolic reprogramming. Normal spinal cord metabolism is characterized by independent cellular metabolism and intercellular metabolic coupling. However, spinal cord injury results in metabolic disorders that include disturbances in glucose metabolism, lipid metabolism, and mitochondrial dysfunction. These metabolic disturbances lead to corresponding pathological changes, including the failure of axonal regeneration, the accumulation of scarring, and the activation of microglia. To rescue spinal cord injury at the metabolic level, potential metabolic reprogramming approaches have emerged, including replenishing metabolic substrates, reconstituting metabolic couplings, and targeting mitochondrial therapies to alter cell fate. The available evidence suggests that metabolic reprogramming holds great promise as a next-generation approach for the treatment of spinal cord injury. To further advance the metabolic treatment of the spinal cord injury, future efforts should focus on a deeper understanding of neurometabolism, the development of more advanced metabolomics technologies, and the design of highly effective metabolic interventions.

Growth, fusion and degradation of lipid droplets: advances in lipid droplet regulatory protein

Context: An adequate supply of energy is essential for the proper functioning of all life activities in living organisms. As organelles that store neutral lipids, lipid droplets (LDs) are involved in the synthesis and metabolism of lipids in cells and are also an important source of energy supply.

Methods and mechanisms: A comprehensive summary of the literature was first carried out to screen for relevant proteins affecting the morphological size of LDs. The size of milk fat globules (MFGs) is directly influenced by the morphological size of LDs, which also controls the energy storage capacity of LDs. In this review, we detail the progress of research into the role of some protein in regulating the morphological size of LDs.

Conclusion: It has been discovered that the number of protein are involved in the control of LD growth and degradation, such as Rab18-mediated local synthesis of triacylglycerol (TAG), cell death-inducing DFF45-like effector family proteins (CIDEs)-mediated atypical fusion between LDs, Stomatin protein-mediated LD fusion and autophagy-related proteins (ATGs)-mediated autophagic degradation of LDs. However, more studies are needed in the future to enrich the network of mechanisms that regulate the morphological size of LDs.

Lipid Droplet in Lipodystrophy and Neurodegeneration

Lipid droplets are ubiquitous yet distinct intracellular organelles that are gaining attention for their uses outside of energy storage. Their formation, role in the physiological function, and the onset of the pathology have been gaining attention recently. Their structure, synthesis, and turnover play dynamic roles in both lipodystrophy and neurodegeneration. Factors like development, aging, inflammation, and cellular stress regulate the synthesis of lipid droplets. The biogenesis of lipid droplets has a critical role in reducing cellular stress. Lipid droplets, in response to stress, sequester hazardous lipids into their neutral lipid core, preserving energy and redox balance while guarding against lipotoxicity. Thus, the maintenance of lipid droplet homeostasis in adipose tissue, CNS, and other body tissues is essential for maintaining organismal health. Insulin resistance, hypertriglyceridemia, and lipid droplet accumulation are the severe metabolic abnormalities that accompany lipodystrophy-related fat deficit. Accumulation of lipid droplets is detected in almost all neurodegenerative diseases like Alzheimer's, Parkinson's, Huntington's, and Hereditary spastic paraplegia. Hence, the regulation of lipid droplets can be used as an alternative approach to the treatment of several diseases. The current review summarizes the structure, composition, biogenesis, and turnover of lipid droplets, with an emphasis on the factors responsible for the accumulation and importance of lipid droplets in lipodystrophy and neurodegenerative disease.

Tools to Dissect Lipid Droplet Regulation, Players, and Mechanisms

Spurred by the authors' own recent discovery of reactive metabolite-regulated nexuses involving lipid droplets (LDs), this perspective discusses the latest knowledge and multifaceted approaches toward deconstructing the function of these dynamic organelles, LD-associated localized signaling networks, and protein players. Despite accumulating knowledge surrounding protein families and pathways of conserved importance for LD homeostasis surveillance and maintenance across taxa, much remains to be understood at the molecular level. In particular, metabolic stress-triggered contextual changes in LD-proteins' localized functions, crosstalk with other organelles, and feedback signaling loops and how these are specifically rewired in disease states remain to be illuminated with spatiotemporal precision. We hope this perspective promotes an increased interest in these essential organelles and innovations of new tools and strategies to better understand context-specific LD regulation critical for organismal health.

Acid-Controlled Fabrication of Multicolor Carbon Dots with Switchable Organelle-Targeting Capability for Visualizing Organelle Interactions

Synchronous regulation of the photoluminescence and physicochemical characteristics of multicolor carbon dots (CDs) can fully realize their application potential in multicomponent imaging. Herein, by utilizing an acid-regulated synthetic strategy, green-emissive and orange-emissive CDs that target lipid droplets (LDs) and mitochondria (Mito) have been developed for fluorescence visualization of LD-Mito interactions. The finding of different molecular fluorophores reveals that the precursor undergoes different reaction pathways in neutral and acidic conditions, which alters the size of sp2-conjugated domain and surface properties for the successful regulation of photoluminescence properties and organelle-targeting ability. Moreover, the one-step fabrication of these two CDs was also realized by lowering the dosage of acid. Therefore, the multicolor imaging of LDs and Mito has been achieved with one-step staining, disclosing that their interaction frequency decreases during the lipotoxicity process. This work successfully demonstrates the high coupling potential between multicolor CDs and organelle-interaction visualization, which would provide guidance on the correlation between photoluminescence features and other properties of multicolor CDs for extending application space.

Lipid metabolism: the potential therapeutic targets in glioblastoma

Glioblastoma is a highly malignant tumor of the central nervous system with a high mortality rate. The mechanisms driving glioblastoma onset and progression are complex, posing substantial challenges for developing precise therapeutic interventions to improve patient survival. Over a century ago, the discovery of the Warburg effect underscored the importance of abnormal glycolysis in tumors, marking a pivotal moment in cancer research. Subsequent studies have identified mitochondrial energy conversion as a fundamental driver of tumor growth. Recently, lipid metabolism has emerged as a critical factor in cancer cell survival, providing an alternative energy source. Research has shown that lipid metabolism is reprogrammed in glioblastoma, playing a vital role in shaping the biological behavior of tumor cells. In this review, we aim to elucidate the impact of lipid metabolism on glioblastoma tumorigenesis and explore potential therapeutic targets. Additionally, we provide insights into the regulatory mechanisms that govern lipid metabolism, emphasizing the critical roles of key genes and regulators involved in this essential metabolic process.

CRSP8-driven fatty acid metabolism reprogramming enhances hepatocellular carcinoma progression by inhibiting RAN-mediated PPARα nucleus-cytoplasm shuttling

BACKGROUND

In-depth exploration into the dysregulation of lipid metabolism in hepatocellular carcinoma (HCC) has contributed to the development of advanced antitumor strategies. CRSP8 is a critical component of mediator multiprotein complex involved in transcriptional recruiting. However, the regulatory mechanisms of CRSP8 on fatty acid metabolism reprogramming and HCC progression remain unclear.

METHODS

In-silico/house dataset analysis, lipid droplets (LDs) formation, HCC mouse models and targeted lipidomic analysis were performed to determine the function of CRSP8 on regulating lipid metabolism in HCC. The subcellular colocalization and live cell imaging of LDs, transmission electron microscopy, co-immunoprecipitation and luciferase reporter assay were employed to investigate their potential mechanism.

RESULTS

CRSP8 was identified as a highly expressed oncogene essential for the proliferation and aggressiveness of HCC in vitro and in vivo. The tumor promotion of CRSP8 was accompanied by LDs accumulation and increased de novo fatty acids (FAs) synthesis. Moreover, CRSP8 diminished the colocalization between LC3 and LDs to impair lipophagy in a nuclear-localized PPARα-dependent manner, which decreased the mobilization of FAs from LDs degradation and hindered mitochondrial fatty acid oxidation. Mechanistically, the small ras family GTPase RAN was transcriptionally activated by CRSP8, leading to the reinforcement of RAN/CRM1-mediated nuclear export. CRSP8-induced enhanced formation of RAN/CRM1/PPARα nucleus-cytoplasm shuttling heterotrimer orchestrated cytoplasmic translocation of PPARα, attenuated nPPARα-mediated lipophagy and fatty acid catabolism, subsequently exacerbated HCC progression. In CRSP8-enriched HCC, lipid synthesis inhibitor Orlistat effectively reshaped the immunosuppressive tumor microenvironment (TME) and improved the efficacy of anti-PD-L1 therapy in vivo.

CONCLUSION

Our study establishes that CRSP8-driven fatty acid metabolism reprogramming facilitates HCC progression via the RAN/CRM1/PPARα nucleus-cytoplasm shuttling heterotrimer and impaired lipophagy-derived catabolism. Targeting the energy supply sourced from lipids could represent a promising therapeutic strategy for treating CRSP8-sufficient HCC.

Kinsenoside Suppresses DGAT1-Mediated Lipid Droplet Formation to Trigger Ferroptosis in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) presents limited therapeutic options and is characterized by a poor prognosis. Although Kinsenoside (KIN) possesses a wide range of pharmacological activities, its effect and mechanism in TNBC remain unclear. The objective of this research was to explore the therapeutic effectiveness and the molecular mechanisms of KIN on TNBC. Xenograft experiment was carried out to assess the impact of KIN on TNBC in vivo. The effect of KIN on TNBC in vitro was evaluated through the analysis of cell cytotoxicity and colony formation assays. Oil Red O staining and BODIPY 493/503 fluorescence staining were employed to detect the effect of KIN on lipid droplet (LD) formation. Transcriptomics and inhibitor-rescue experiments were conducted to investigate the role of KIN on TNBC. Mechanistic experiments, including quantitative real-time polymerase chain reaction (RT-qPCR), Western blotting, diacylglycerol acyltransferase 1 (DGAT1) overexpression assay, and flow cytometric assay, were employed to uncover the regulatory mechanisms of KIN on TNBC. KIN inhibited tumor growth without causing obvious toxicity to the liver and kidneys. In vitro experiments demonstrated that KIN significantly inhibited the viability and proliferation of TNBC cells, accompanied by decreased LD formation and lipid content. Polyunsaturated fatty acids (PUFAs) levels were significantly increased by KIN. Furthermore, transcriptomics and inhibitor-rescue experiments revealed that KIN induced ferroptosis in TNBC cells. KIN could significantly regulate ferroptosis-related proteins. Lipid peroxidation, iron accumulation, and GSH depletion also confirmed this. The LD inducer mitigated the KIN-induced ferroptosis in TNBC. The overexpression of DGAT1 attenuated the effects of KIN on cell viability and proliferation. Furthermore, the overexpression of DGAT1 inhibited the effect of KIN to trigger ferroptosis in TNBC cells. Our findings confirmed that KIN could trigger ferroptosis by suppressing DGAT1-mediated LD formation, thereby demonstrating a promising therapeutic effect of KIN in TNBC.

Proximity proteomics reveals a mechanism of fatty acid transfer at lipid droplet-mitochondria- endoplasmic reticulum contact sites

Membrane contact sites between organelles are critical for the transfer of biomolecules. Lipid droplets store fatty acids and form contacts with mitochondria, which regulate fatty acid oxidation and adenosine triphosphate production. Protein compartmentalization at lipid droplet-mitochondria contact sites and their effects on biological processes are poorly described. Using proximity-dependent biotinylation methods, we identify 71 proteins at lipid droplet-mitochondria contact sites, including a multimeric complex containing extended synaptotagmin (ESYT) 1, ESYT2, and VAMP Associated Protein B and C (VAPB). High resolution imaging confirms localization of this complex at the interface of lipid droplet-mitochondria-endoplasmic reticulum where it likely transfers fatty acids to enable β-oxidation. Deletion of ESYT1, ESYT2 or VAPB limits lipid droplet-derived fatty acid oxidation, resulting in depletion of tricarboxylic acid cycle metabolites, remodeling of the cellular lipidome, and induction of lipotoxic stress. These findings were recapitulated in Esyt1 and Esyt2 deficient mice. Our study uncovers a fundamental mechanism that is required for lipid droplet-derived fatty acid oxidation and cellular lipid homeostasis, with implications for metabolic diseases and survival.

CAMKIIδ Reinforces Lipid Metabolism and Promotes the Development of B Cell Lymphoma

The most prevalent types of lymphomas are B cell lymphomas (BCL). Newer therapies for BCL have improved the prognosis for many patients. However, approximately 30% with aggressive BCL either remain refractory or ultimately relapse. These patients urgently need other options. This study shows how calcium/calmodulin-dependent protein kinase II delta (CAMKIIδ) is pivotal for BCL development. In BCL cells, ablation of CAMKIIδ inhibits both lipolysis from lipid droplets and oxidative phosphorylation (OXPHOS). With lipolysis blocked, BCL progression is markedly suppressed in two distinct BCL mouse models: MYC-driven EµMyc mice and Myc/Bcl2 double-expressed mice. When CAMKIIδ is present, it destabilizes transcription factor Forkhead Box O3A (FOXO3A) by phosphorylating it at Ser7 and Ser12. This then permits transcription of downstream gene IRF4 - a master transcription factor of lipid metabolism. The CAMKIIδ/FOXO3A axis bolsters lipid metabolism, mitochondrial respiration, and tumor fitness in BCL under metabolic stress. This study also evaluates Tetrandrine (TET), a small molecule compound, as a potent CAMKIIδ inhibitor. TET attenuates metabolic fitness and elicits therapeutic responses both in vitro and in vivo. Collectively, this study highlights how CAMKIIδ is critical in BCL progression. The results also pave the way for innovative therapeutic strategies for treating aggressive BCL.

Lipid droplets in the nervous system: involvement in cell metabolic homeostasis

Lipid droplets serve as primary storage organelles for neutral lipids in neurons, glial cells, and other cells in the nervous system. Lipid droplet formation begins with the synthesis of neutral lipids in the endoplasmic reticulum. Previously, lipid droplets were recognized for their role in maintaining lipid metabolism and energy homeostasis; however, recent research has shown that lipid droplets are highly adaptive organelles with diverse functions in the nervous system. In addition to their role in regulating cell metabolism, lipid droplets play a protective role in various cellular stress responses. Furthermore, lipid droplets exhibit specific functions in neurons and glial cells. Dysregulation of lipid droplet formation leads to cellular dysfunction, metabolic abnormalities, and nervous system diseases. This review aims to provide an overview of the role of lipid droplets in the nervous system, covering topics such as biogenesis, cellular specificity, and functions. Additionally, it will explore the association between lipid droplets and neurodegenerative disorders. Understanding the involvement of lipid droplets in cell metabolic homeostasis related to the nervous system is crucial to determine the underlying causes and in exploring potential therapeutic approaches for these diseases.

Integrative metabolism in MASLD and MASH: Pathophysiology and emerging mechanisms

The liver acts as a central metabolic hub, integrating signals from the gastrointestinal tract and adipose tissue to regulate carbohydrate, lipid, and amino acid metabolism. Gut-derived metabolites, such as acetate and ethanol and non-esterified fatty acids from white adipose tissue, influence hepatic processes, which rely on mitochondrial function to maintain systemic energy balance. Metabolic dysregulation caused by obesity, insulin resistance, and type 2 diabetes disrupts these pathways, leading to metabolic dysfunction-associated steatotic liver disease (MASLD) and steatohepatitis (MASH). In this review, we explore the metabolic fluxes within the gut-adipose tissue-liver axis, focusing on the pivotal role of de novo lipogenesis, dietary substrates like glucose and fructose, and changes in mitochondrial function during MASLD progression. We also highlight the contributions of white adipose tissue insulin resistance and impaired mitochondrial dynamics to hepatic lipid accumulation. Further understanding how the interplay between substrate flux from the gastro-intestinal tract integrates with adipose tissue and intersects with structural and functional alterations to liver mitochondria will be important to identify novel therapeutic targets and advance the treatment of MASLD and MASH.

Caki-1 Spheroids as a Renal Model for Studying Free Fatty Acid-Induced Lipotoxicity

Lipotoxicity, resulting from the buildup of excess lipids in non-adipose tissues, is increasingly recognized as a major contributor to the progression of kidney disease, highlighting the need for alternative models to assess its effects on renal cells. The main aim of this study was to investigate the usefulness of Caki-1, a human proximal tubule (PT) and renal cell carcinoma (RCC) representative cell line, as a 3D model system for studying free fatty acid-induced PT lipotoxicity. Caki-1 spheroids were generated and maintained on ultra-low attachment plates and characterized regarding time-dependent morphology changes. In optimal 3D culture conditions, Caki-1 cells formed well-defined large compact spheroids with uniform morphology, good circularity, and increased diameter from days 4-12. Chronic exposure to saturated palmitate resulted in dose- and time-dependent spheroid disintegration and cell death, including dispersed and flattened spheroid morphology, with increased dead cells in the peripheral layers and decreased spheroid core. Moreover, palmitate-treated spheroids showed a significant increase in cleaved poly(ADP-ribose) polymerase (PARP) and active caspase-3. Palmitate-induced PARP cleavage, as well as endoplasmic reticulum (ER) stress and autophagy dysfunction, were blunted by triacsin C, an inhibitor of long-chain acyl-CoA synthetases. In addition, co-incubation with unsaturated oleate prevented palmitate-induced spheroid disintegration and apoptotic cell death in Caki-1 3D culture. While fatty acid overload upregulated lipid droplet protein perilipin 2 in Caki-1 cells, knockdown of perilipin 2 by siRNAs resulted in an exacerbation of palmitate-induced cell death. Together, these results indicate that the 3D Caki-1 spheroid model is a simple and reproducible in vitro system for studying renal lipotoxicity and lipid metabolism that gives useful readouts at the molecular, cellular, and multicellular levels.

Endosomal trafficking participates in lipid droplet catabolism to maintain lipid homeostasis

The interplay between lipid droplets (LDs) and endosomes remains unknown. Here, we screen and synthesize AP1-coumarin, an LD-specific probe, by conjugating a fluorescent dye coumarin to a triazine compound AP1. AP1-coumarin labels all stages of LDs in live cells and markedly induces the accumulation of enlarged RAB5-RAB7 double-positive intermediate endosomes. The AP1-coumarin-labeled LDs contact these intermediate endosomes, with some LDs even being engulfed in them. When LD biogenesis is inhibited, the ability of AP1-coumarin to label LDs is markedly reduced, and the accumulation of enlarged intermediate endosomes is abolished. Moreover, blocking the biogenesis of LDs decreases the number of late endosomes while increasing the number of early endosomes and inhibits the endosomal trafficking of low-density lipoprotein (LDL) and transferrin. Correspondingly, interference with RAB5 or RAB7, either through knockdown or using dominant-negative mutants, inhibits LD catabolism, whereas the expression of a RAB7 constitutively active mutant accelerates LD catabolism. Additionally, CCZ1 knockdown not only induces the accumulation of intermediate endosomes but also inhibits LD catabolism. These results collectively suggest that LDs and endosomes interact and influence each other's functions, and endosomal trafficking participates in the catabolic process of LDs to maintain lipid homeostasis.

Functional compartmentalization of hepatic mitochondrial subpopulations during MASH progression

The role of peridroplet mitochondria (PDM) in diseased liver, such as during the progression of metabolic dysfunction-associated steatohepatitis (MASH), remains unknown. We isolated hepatic cytoplasmic mitochondria (CM) and PDM from a mouse model of diet-induced MASLD/MASH to characterize their functions from simple steatosis to advanced MASH, using chow-fed mice as controls. Our findings show an inverse relationship between hepatic CM and PDM levels from healthy to steatosis to advanced MASH. Proteomics analysis revealed these two mitochondrial populations are compositionally and functionally distinct. We found that hepatic PDM are more bioenergetically active than CM, with higher pyruvate oxidation capacity in both healthy and diseased liver. Higher respiration capacity of PDM was associated with elevated OXPHOS protein complexes and increased TCA cycle flux. In contrast, CM showed higher fatty acid oxidation capacity with MASH progression. Transmission electron microscopy revealed larger and elongated mitochondria during healthy and early steatosis, which appeared small and fragmented during MASH progression. These changes coincided with higher MFN2 protein levels in hepatic PDM and higher DRP1 protein levels in hepatic CM. These findings highlight the distinct roles of hepatic CM and PDM in MASLD progression towards MASH.

Targeting membrane contact sites to mediate lipid dynamics: innovative cancer therapies

Membrane contact sites (MCS) are specialized regions where organelles are closely interconnected through membrane structures, facilitating the transfer and exchange of ions, lipids, and other molecules. This proximity enables a synergistic regulation of cellular homeostasis and functions. The formation and maintenance of these contact sites are governed by specific proteins that bring organelle membranes into close apposition, thereby enabling functional crosstalk between cellular compartments. In eukaryotic cells, lipids are primarily synthesized and metabolized within distinct organelles and must be transported through MCS to ensure proper cellular function. Consequently, MCS act as pivotal platforms for lipid synthesis and trafficking, particularly in cancer cells and immune cells within the tumor microenvironment, where dynamic alterations are critical for maintaining lipid homeostasis. This article provides a comprehensive analysis of how these cells exploit membrane contact sites to modulate lipid synthesis, metabolism, and transport, with a specific focus on how MCS-mediated lipid dynamics influence tumor progression. We also examine the differences in MCS and associated molecules across various cancer types, exploring novel therapeutic strategies targeting MCS-related lipid metabolism for the development of anticancer drugs, while also addressing the challenges involved.

Near-Native Imaging of Metal Ion-Initiated Cell State Transition

Metal ions are indispensable to life, as they can serve as essential enzyme cofactors to drive fundamental biochemical reactions, yet paradoxically, excess is highly toxic. Higher-order cells have evolved functionally distinct organelles that separate and coordinate sophisticated biochemical processes to maintain cellular homeostasis upon metal ion stimuli. Here, we uncover the remodeling of subcellular architecture and organellar interactome in yeast initiated by several metal ion stimulations, relying on near-native three-dimensional imaging, cryo-soft X-ray tomography. The three-dimensional architecture of intact yeast directly shows that iron or manganese triggers a hormesis-like effect that promotes cell proliferation. This process leads to the reorganization of organelles in the preparation for division, characterized by the polar distribution of mitochondria, an increased number of lipid droplets (LDs), volume shrinkage, and the formation of a hollow structure. Additionally, vesicle-like structures that detach from the vacuole are observed. Oppositely, cadmium or mercury causes stress-associated phenotypes, including mitochondrial fragmentation, LD swelling, and autophagosome formation. Notably, the organellar interactome, encompassing the interactions between mitochondria and LDs and those between the nuclear envelope and LDs, is quantified and exhibits alteration with multifaceted features in response to different metal ions. More importantly, the dynamics of organellar architecture render them more sensitive biomarkers than traditional approaches for assessing the cell state. Strikingly, yeast has a powerful depuration capacity to isolate and transform the overaccumulated cadmium in the vacuole, mitochondria, and cytoplasm as a high-value product, quantum dots. This work presents the possibility of discovering fundamental links between organellar morphological characteristics and the cell state.

Fatty Acid Trafficking Between Lipid Droplets and Mitochondria: An Emerging Perspective

The current understanding of lipid droplets (LDs) in cell biology has evolved from being viewed merely as storage compartments. LDs are now recognized as metabolic hubs that act as cytosolic buffers against the detrimental effects of free fatty acids (FAs). Upon activation, FAs traverse various cellular pathways, including oxidation in mitochondria, integration into complex lipids, or storage in triacylglycerols (TGs). Maintaining a balance among these processes is crucial in cellular FA trafficking, and under metabolically challenging circumstances the routes of FA metabolism adapt to meet the current cellular needs. This typically involves an increased demand for anabolic intermediates or energy and the prevention of redox stress. Surprisingly, LDs accumulate under certain conditions such as amino acid starvation. This review explores the biochemical aspects of FA utilization in both physiological contexts and within cancer cells, focusing on the metabolism of TGs, cholesteryl esters (CEs), and mitochondrial FA oxidation. Emphasis is placed on the potential toxicity associated with non-esterified FAs in cytosolic and mitochondrial compartments. Additionally, we discuss mechanisms that lead to increased LD biogenesis due to an inhibited mitochondrial import of FAs.

VEGFD/VEGFR3 signaling contributes to the dysfunction of the astrocyte IL-3/microglia IL-3Rα cross-talk and drives neuroinflammation in mouse ischemic stroke

Astrocyte-derived IL-3 activates the corresponding receptor IL-3Rα in microglia. This cross-talk between astrocytes and microglia ameliorates the pathology of Alzheimer's disease in mice. In this study we investigated the role of IL-3/IL-3Rα cross-talk and its regulatory mechanisms in ischemic stroke. Ischemic stroke was induced in mice by intraluminal occlusion of the right middle cerebral artery (MCA) for 60 min followed by reperfusion (I/R). Human astrocytes or microglia subjected to oxygen-glucose deprivation and reoxygenation (OGD/Re) were used as in vitro models of brain ischemia. We showed that both I/R and OGD/Re significantly induced decreases in astrocytic IL-3 and microglial IL-3Rα protein levels, accompanied by pro-inflammatory activation of A1-type astrocytes and M1-type microglia. Importantly, astrocyte-derived VEGFD acting on VEGFR3 of astrocytes and microglia contributed to the cross-talk dysfunction and pro-inflammatory activation of the two glial cells, thereby mediating neuronal cell damage. By using metabolomics and multiple biochemical approaches, we demonstrated that IL-3 supplementation to microglia reversed OGD/Re-induced lipid metabolic reprogramming evidenced by upregulated expression of CPT1A, a rate-limiting enzyme for the mitochondrial β-oxidation, and increased levels of glycerophospholipids, the major components of cellular membranes, causing reduced accumulation of lipid droplets, thus reduced pro-inflammatory activation and necrosis, as well as increased phagocytosis of microglia. Notably, exogenous IL-3 and the VEGFR antagonist axitinib reestablished the cross-talk of IL-3/IL-3Rα, improving microglial lipid metabolic levels via upregulation of CPT1A, restoring microglial phagocytotic function and attenuating microglial pro-inflammatory activation, ultimately contributing to brain recovery from I/R insult. Our results demonstrate that VEGFD/VEGFR3 signaling contributes to the dysfunction of the astrocyte IL-3/microglia IL-3Rα cross-talk and drives pro-inflammatory activation, causing lipid metabolic reprogramming of microglia. These insights suggest VEGFR3 antagonism or restoring IL-3 levels as a potential therapeutic strategy for ischemic stroke.

The many faces of DGAT1

Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) is a multifaced enzyme with a wide spectrum of substrates, from lipids through waxes to retinoids, which makes it an interesting therapeutic target. DGAT1 inhibitors are currently at various stages of preclinical and clinical trials, mostly related to metabolic diseases. Interestingly, in recent years, a growing amount of research has shown the influence of DGAT1 on immune cell metabolism and functions, highlighting its important role during infections and tumorigenesis. In this review, we aim to elucidate the potential immunomodulatory effect of DGAT1 in physiological and pathological conditions.

MTCH2 controls energy demand and expenditure to fuel anabolism during adipogenesis

Mitochondrial carrier homolog 2 (MTCH2) is a regulator of apoptosis, mitochondrial dynamics, and metabolism. Loss of MTCH2 results in mitochondrial fragmentation, an increase in whole-body energy utilization, and protection against diet-induced obesity. In this study, we used temporal metabolomics on HeLa cells to show that MTCH2 deletion results in a high ATP demand, an oxidized cellular environment, and elevated utilization of lipids, amino acids, and carbohydrates, accompanied by a decrease in several metabolites. Lipidomics analysis revealed a strategic adaptive reduction in membrane lipids and an increase in storage lipids in MTCH2 knockout cells. Importantly, MTCH2 knockout cells showed an increase in mitochondrial oxidative function, which may explain the higher energy demand. Interestingly, this imbalance in energy metabolism and reductive potential triggered by MTCH2-deletion prevents NIH3T3L1 preadipocytes from differentiating into mature adipocytes, an energy consuming reductive biosynthetic process. In summary, the loss of MTCH2 leads to increased mitochondrial oxidative activity and energy demand, creating a catabolic and oxidative environment that fails to fuel the anabolic processes required for lipid accumulation and adipocyte differentiation.

The cholesterol metabolite 25-hydroxycholesterol suppresses porcine deltacoronavirus via lipophagy inhibition and mTORC1 modulation

25-Hydroxycholesterol (25HC) is a hydroxylated cholesterol with multiple antiviral activities, however, little is known about the mechanisms by which 25HC correlates antiviral ability with lipid droplet (LD) dynamic balance to ensure cholesterol homeostasis. In the present study, 25HC was applied to porcine deltacoronavirus (PDCoV)-infected LLC-PK1 (Lilly Laboratories Culture-Porcine Kidney 1) cells and piglets to explore its antiviral capacity and underlying mechanism. The results revealed that 25HC decreased free cholesterol (FC) levels but increased triglyceride (TG) levels in PDCoV-infected cells and piglets. The accumulation of LDs induced by oleic acid (OA) impedes PDCoV replication. In addition, 25HC administration increases LD accumulation and declines protein expression associated with lipophagy and lysosomes to facilitate LD accumulation. Moreover, 25HC inhibited TFEB (transcription factor-EB) expression, blocked its translocation into the nucleus and reversed Mechanistic Target of Rapamycin Complex 1 (mTORC1) activity, which in turn hindered lipophagy and PDCoV replication. Additionally, 25HC treatment ameliorated the clinical symptoms and intestinal injury of PDCoV-infected piglets. These findings reveal the beneficial effect of lipophagy on PDCoV infection and uncover the antiviral mechanism of 25HC, by which lipophagy and mTOR activity are tightly controlled by 25HC.

Autophagic flux-lipid droplet biogenesis cascade sustains mitochondrial fitness in colorectal cancer cells adapted to acidosis

Cancer development is associated with adaptation to various stressful conditions, such as extracellular acidosis. The adverse tumor microenvironment also selects for increased malignancy. Mitochondria are integral in stress sensing to allow for tumor cells to adapt to stressful conditions. Here, we show that colorectal cancer cells adapted to acidic microenvironment (CRC-AA) are more reliant on oxidative phosphorylation than their parental cells, and the acetyl-CoA in CRC-AA cells are generated from fatty acids and glutamine, but not from glucose. Consistently, CRC-AA cells exhibit increased mitochondrial mass and fitness that depends on an upregulated autophagic flux-lipid droplet axis. Lipid droplets (LDs) function as a buffering system to store the fatty acids derived from autophagy and to protect mitochondria from lipotoxicity in CRC-AA cells. Blockade of LD biogenesis causes mitochondrial dysfunction that can be rescued by inhibiting carnitine palmitoyltransferase 1 α (CPT1α). High level of mitochondrial superoxide is essential for the AMPK activation, resistance to apoptosis, high autophagic flux and mitochondrial function in CRC-AA cells. Thus, our results demonstrate that the cascade of autophagic flux and LD formation plays an essential role in sustaining mitochondrial fitness to promote cancer cell survival under chronic acidosis. Our findings provide insight into the pro-survival metabolic plasticity in cancer cells under microenvironmental or therapeutic stress and imply that this pro-survival cascade may potentially be targeted in cancer therapy.

Pellino 3 E3 ligase promotes starvation-induced autophagy to prevent hepatic steatosis

Nutrient deprivation is a major trigger of autophagy, a conserved quality control and recycling process essential for cellular and tissue homeostasis. In a high-content image-based screen of the human ubiquitome, we here identify the E3 ligase Pellino 3 (PELI3) as a crucial regulator of starvation-induced autophagy. Mechanistically, PELI3 localizes to autophagic membranes, where it interacts with the ATG8 proteins through an LC3-interacting region (LIR). This facilitates PELI3-mediated ubiquitination of ULK1, driving ULK1's subsequent proteasomal degradation. PELI3 depletion leads to an aberrant accumulation and mislocalization of ULK1 and disrupts the early steps of autophagosome formation. Genetic deletion of Peli3 in mice impairs fasting-induced autophagy in the liver and enhances starvation-induced hepatic steatosis by reducing autophagy-mediated clearance of lipid droplets. Notably, PELI3 expression is decreased in the livers of patients with metabolic dysfunction-associated steatotic liver disease (MASLD), suggesting its role in hepatic steatosis development in humans. The findings suggest that PELI3-mediated control of autophagy plays a protective role in liver health.

Lipid droplets in central nervous system and functional profiles of brain cells containing lipid droplets in various diseases

Lipid droplets (LDs), serving as the convergence point of energy metabolism and multiple signaling pathways, have garnered increasing attention in recent years. Different cell types within the central nervous system (CNS) can regulate energy metabolism to generate or degrade LDs in response to diverse pathological stimuli. This article provides a comprehensive review on the composition of LDs in CNS, their generation and degradation processes, their interaction mechanisms with mitochondria, the distribution among different cell types, and the roles played by these cells-particularly microglia and astrocytes-in various prevalent neurological disorders. Additionally, we also emphasize the paradoxical role of LDs in post-cerebral ischemia inflammation and explore potential underlying mechanisms, aiming to identify novel therapeutic targets for this disease.

Omics Approaches to Study Perilipins and Their Significant Biological Role in Cardiometabolic Disorders

Lipid droplets (LDs), highly dynamic cellular organelles specialized in lipid storage and maintenance of lipid homeostasis, contain several proteins on their surface, among which the perilipin (Plin) family stands out as the most abundant group of LD-binding proteins. They play a pivotal role in influencing the behavior and functionality of LDs, regulating lipase activity, and preserving a balance between lipid synthesis and degradation, which is crucial in the development of obesity and abnormal accumulation of fat in non-adipose tissues, causing negative adverse biological effects, such as insulin resistance, mitochondrial dysfunction, and inflammation. The expression levels of Plins are often associated with various diseases, such as hepatic steatosis and atherosclerotic plaque formation. Thus, it becomes of interest to investigate the Plin roles by using appropriate "omics" approaches that may provide additional insight into the mechanisms through which these proteins contribute to cellular and tissue homeostasis. This review is intended to give an overview of the most significant omics studies focused on the characterization of Plin proteins and the identification of their potential targets involved in the development and progression of cardiovascular and cardiometabolic complications, as well as their interactors that could be useful for more efficient therapeutic and preventive approaches for patients.

Mitochondria-giant lipid droplet proximity and autophagy suppression in nitrogen-depleted oleaginous yeast Lipomyces starkeyi cells

Balancing energy production and storage is a fundamental process critical for cellular homeostasis in most eukaryotes that relies on the intimate interplay between mitochondria and lipid droplets (LDs). In the oleaginous yeast Lipomyces starkeyi under nitrogen starvation, LD forms a single giant spherical structure that is easily visible under a light microscope. Currently, how mitochondria behave in L. starkeyi cells undergoing giant LD formation remains unknown. Here we show that mitochondria transition from fragments to elongated tubules and sheet-like structures that are in close proximity to a giant LD in nitrogen-depleted L. starkeyi cells. Under the same conditions, mitochondrial degradation and autophagy are strongly suppressed, suggesting that these catabolic events are not required for giant LD formation. Conversely, carbon-depleted cells suppress mitochondrial elongation and LD expansion, whereas they promote mitochondrial degradation and autophagy. We propose a potential link of mitochondrial proximity and autophagic suppression to giant LD formation.

FSP1-mediated lipid droplet quality control prevents neutral lipid peroxidation and ferroptosis

Lipid droplets (LDs) are organelles that store and supply lipids based on cellular needs. While mechanisms preventing oxidative damage to membrane phospholipids are established, the vulnerability of LD neutral lipids to peroxidation and protective mechanisms are unknown. Here, we identify LD-localized Ferroptosis Suppressor Protein 1 (FSP1) as a critical regulator that prevents neutral lipid peroxidation by recycling coenzyme Q10 (CoQ10) to its lipophilic antioxidant form. Lipidomics reveal that FSP1 loss leads to the accumulation of oxidized triacylglycerols and cholesteryl esters, and biochemical reconstitution of FSP1 with CoQ10 and NADH suppresses triacylglycerol peroxidation in vitro. Notably, polyunsaturated fatty acid (PUFA)-rich triacylglycerols enhance cancer cell sensitivity to FSP1 loss and inducing PUFA-rich LDs triggers triacylglycerol peroxidation and LD-initiated ferroptosis when FSP1 activity is impaired. These findings uncover the first LD lipid quality control pathway, wherein LD-localized FSP1 maintains neutral lipid integrity to prevent the buildup of oxidized lipids and induction of ferroptosis.

DFCP1 is a regulator of starvation-driven ATGL-mediated lipid droplet lipolysis

Lipid droplets (LDs) are transient lipid storage organelles that can be readily tapped to resupply cells with energy or lipid building blocks, and therefore play a central role in cellular metabolism. Double FYVE Domain Containing Protein 1 (DFCP1/ZFYVE1) has emerged as a key regulator of LD metabolism, where the nucleotide-dependent accumulation of DFCP1 on LDs influences their size, number, and dynamics. Here we show that DFCP1 regulates lipid metabolism by directly modulating the activity of Adipose Triglyceride Lipase (ATGL/PNPLA2), the rate-limiting lipase driving the catabolism of LDs. We show through pharmacological inhibition of key enzymes associated with LD metabolism that DFCP1 specifically regulates lipolysis and, to a lesser extent, lipophagy. Consistent with this observation, DFCP1 interacts with and recruits ATGL to LDs in starved cells, irrespective of other known regulatory factors of ATGL. We further establish that this interaction prevents dynamic disassociation of ATGL from LDs and thereby impedes the rate of LD lipolysis. Collectively, our findings indicate that DFCP1 is a nutrient-sensitive regulator of LD catabolism.

Exploring fatty acid metabolism in Alzheimer's disease: the key role of CPT1A

Alzheimer's disease (AD) is a severe neurodegenerative disease, and the most common type of dementia, with symptoms of progressive cognitive dysfunction and behavioral impairment. Studying the pathogenesis of AD and exploring new targets for the prevention and treatment of AD is a very worthwhile challenge. Accumulating evidence has highlighted the effects of fatty acid metabolism on AD. In this study, fatty acid metabolism was used as an entry point to understand the pathogenesis of AD and identify new targets. After identifying differentially expressed genes, multiple machine learning algorithms, carnitine palmitoyltransferase 1 A (CPT1A) was identified as the key gene for fatty acid metabolism in AD. Further single nucleus RNA sequencing analysis were performed, and the GSEA results showed that the fatty acid β-oxidation pathway was enriched only in astrocytes, and the fatty acid β-oxidation pathway was down-regulated in the AD astrocytes compared to the CN astrocytes, while CPT1A was specifically downregulated in astrocytes of AD, which was confirmed in vitro experiment subsequently, and decreased expression level of CPT1A would lead to abnormal lipid metabolism, which shapes astrocyte reactivity and injury, neuroinflammatory, and thus affects AD pathogenesis. Our findings report the involvement of CPT1A in AD. We confirm that the primary role of astrocytes for fatty acid β-oxidation, and CPT1A is localized in astrocytes. Downregulated CPT1A could be a novel potential target for the prevention and treatment of AD. Our study provides strong evidence for the involvement of fatty acid metabolism in the pathogenesis of AD.

Circadian Influences on Brain Lipid Metabolism and Neurodegenerative Diseases

Circadian rhythms are intrinsic, 24 h cycles that regulate key physiological, mental, and behavioral processes, including sleep-wake cycles, hormone secretion, and metabolism. These rhythms are controlled by the brain's suprachiasmatic nucleus, which synchronizes with environmental signals, such as light and temperature, and consequently maintains alignment with the day-night cycle. Molecular feedback loops, driven by core circadian "clock genes", such as Clock, Bmal1, Per, and Cry, are essential for rhythmic gene expression; disruptions in these feedback loops are associated with various health issues. Dysregulated lipid metabolism in the brain has been implicated in the pathogenesis of neurological disorders by contributing to oxidative stress, neuroinflammation, and synaptic dysfunction, as observed in conditions such as Alzheimer's and Parkinson's diseases. Disruptions in circadian gene expression have been shown to perturb lipid regulatory mechanisms in the brain, thereby triggering neuroinflammatory responses and oxidative damage. This review synthesizes current insights into the interconnections between circadian rhythms and lipid metabolism, with a focus on their roles in neurological health and disease. It further examines how the desynchronization of circadian genes affects lipid metabolism and explores the potential mechanisms through which disrupted circadian signaling might contribute to the pathophysiology of neurodegenerative disorders.

Zhishi Xiebai Guizhi Decoction modulates hypoxia and lipid toxicity to alleviate pulmonary vascular remodeling of pulmonary hypertension in rats

BACKGROUND

Pulmonary hypertension (PH) is a severe cardio-pulmonary vascular disease, involves complex molecular mechanism especially during the pathological process of pulmonary vascular remodeling, brings a significant challenge to clinical treatment and thus resulting in high mortality rates. Classic Traditional Chinese medicine formula, Zhishi Xiebai Guizhi Decoction (ZXGD), holds therapeutic potential for PH. In present study, we sought to explore therapeutic potential of ZXGD against PH in rats.

METHODS

We employed a combination methods of chemical profiling, echocardiographic, morphologic measurements, molecular biology, rats models and cultured pulmonary artery smooth muscle cells (PASMCs) to achieve this.

RESULTS

Eighteen compounds were precisely identified in ZXGD using UHPLC-QTOF-MS/MS. Our data demonstrated ZXGD could alleviate PH by reducing pulmonary artery pressure and alleviating pulmonary vascular remodeling in rats. Specifically, ZXGD was found to intervene in abnormal expansion of PASMCs, thereby attenuating pulmonary vascular remodeling. ZXGD was also observed to modulate expressions of HIF-1α, ROS, and Nrf2 to alleviate hypoxia and oxidative stress. Additionally, ZXGD significantly regulated disorders in pro-inflammatory cytokines, thus mitigating inflammation. Furthermore, ZXGD decreased levels of decadienyl-L-carnitine and LDL-C, while elevating HDL-C and lipid droplet counts, thereby reducing cholesterol and lipid toxicity and preserving mitochondrial function. Importantly, inhibition of HIF-1α reversed expression of key pathological triggers for pulmonary vascular remodeling. Neohesperidin and naringin in ZXGD extract were identified as the primary contributors to its pharmacological effects against PH.

CONCLUSION

Altogether, our study empirically explored therapeutic potential and pharmacological mechanisms of ZXGD in treating PH, offering a groundwork for the development of novel anti-PH drugs.

Age-related TFEB downregulation in proximal tubules causes systemic metabolic disorders and occasional apolipoprotein A4-related amyloidosis

With the aging of society, the incidence of chronic kidney disease (CKD), a common cause of death, has been increasing. Transcription factor EB (TFEB), the master transcriptional regulator of the autophagy/lysosomal pathway, is regarded as a promising candidate for preventing various age-related diseases. However, whether TFEB in the proximal tubules plays a significant role in elderly patients with CKD remains unknown. First, we found that nuclear TFEB localization in proximal tubular epithelial cells (PTECs) declined with age in both mice and humans. Next, we generated PTEC-specific Tfeb-deficient mice and bred them for up to 24 months. We found that TFEB deficiency in the proximal tubules caused metabolic disorders and occasionally led to apolipoprotein A4 (APOA4) amyloidosis. Supporting this result, we identified markedly decreased nuclear TFEB localization in the proximal tubules of elderly patients with APOA4 amyloidosis. The metabolic disturbances were accompanied by mitochondrial dysfunction due to transcriptional changes involved in fatty acid oxidation and oxidative phosphorylation pathways, as well as decreased mitochondrial clearance. This decreased clearance was reflected by the accumulation of mitochondria-lysosome-related organelles, which depended on lysosomal function. These results shed light on the presumptive mechanisms of APOA4 amyloidosis pathogenesis and provide a therapeutic strategy for CKD-related metabolic disorders and APOA4 amyloidosis.

Pathology and Treatments of Alzheimer's Disease Based on Considering Changes in Brain Energy Metabolism Due to Type 2 Diabetes

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with cognitive dysfunction, memory decline, and behavioral disturbance, and it is pathologically characterized by the accumulation of amyloid plaques and neurofibrillary tangles in the brain. Although various hypotheses have been proposed to explain the pathogenesis of AD, including the amyloid beta hypothesis, oxidative stress hypothesis, and abnormal phosphorylation of tau proteins, the exact pathogenic mechanisms underlying AD remain largely undefined. Furthermore, effective curative treatments are very limited. Epidemiologic studies provide convincing evidence for a significant association between type 2 diabetes and AD. Here, we showed energy metabolism using glucose, lactate, ketone bodies, and lipids as energy substrates in a normal brain, and changes in such energy metabolism due to type 2 diabetes. We also showed the influences of such altered energy metabolism due to type 2 diabetes on the pathology of AD. Furthermore, we comprehensively searched for risk factors related with type 2 diabetes for AD and showed possible therapeutic interventions based on considering risk factors and altered brain energy metabolism due to type 2 diabetes for the development of AD.

Mitochondrial dysfunction of Astrocyte induces cell activation under high salt condition

Excess dietary sodium can accumulate in brain and adversely affect human health. We have confirmed in previous studies that high salt can induce activation of astrocyte manifested by the secretion of various inflammatory factors. In order to further explore the effect of high salt on the internal cell metabolism of astrocytes, RNA sequencing was performed on astrocytes under high salt environment, which indicated the oxidative phosphorylation and glycolysis pathways of astrocytes were downregulated. Next, we found that high salt concentrations elicited astrocyte mitochondrial morphology change, as evidenced by swelling from a short rod to a round shape through a High Intelligent and Sensitive Structured Illumination Microscope (HIS-SIM). Furthermore, we found that high salt concentrations reduced astrocyte mitochondrial oxygen consumption and membrane potential. Treatment with 18-kDa translocator protein (TSPO) ligands FGIN-1-27 improved mitochondrial networks and reversed astrocyte activation under high-salt circumstances. Our study shows that high salt can directly disrupt astrocytic mitochondrial homeostasis and function. Targeting translocator protein signaling may have therapeutic potential against high-salt neurotoxicity.

RAB18 regulates extrahepatic siRNA-mediated gene silencing efficacy

Small interfering RNAs (siRNAs) hold considerable therapeutic potential to selectively silence previously "undruggable" disease-associated targets, offering new opportunities to fight human diseases. This therapeutic strategy, however, is limited by the inability of naked siRNAs to passively diffuse across cellular membranes due to their large molecular size and negative charge. Delivery of siRNAs to liver through conjugation of siRNA to N-acetylgalactosamine (GalNAc) has been a success, providing robust and durable gene knockdown, specifically in hepatocytes. However, the poor delivery and silencing efficacy of siRNAs in other cell types has hindered their applications outside the liver. We previously reported that a genome-wide pooled knockout screen identified RAB18 as a major modulator of GalNAc-siRNA conjugates. Herein, we demonstrate RAB18 knockout/knockdown efficaciously enhances siRNA-mediated gene silencing in hepatic and extrahepatic cell lines and in vivo. Our results reveal a mechanism by which retrograde Golgi-endoplasmic reticulum (ER) transport and the intracellular lipid droplets (LDs) positively regulate siRNA-mediated gene silencing.

Atg5-Mediated Lipophagy Induces Ferroptosis in Corneal Epithelial Cells in Dry Eye Disease

Purpose

Ferroptosis occurred in corneal epithelial cells has been implicated in the inflammation in dry eye disease (DED). Given the proposed link between ferroptosis and autophagy, this study aims to investigate the role of autophagy in driving ferroptosis in corneal epithelial cell and enrich the pathogenesis underlying DED.

Methods

DED models were established in C57BL/6 mice via scopolamine injection and in human corneal epithelial cell line (HCEC) using hyperosmotic medium. Lipidomic and transcriptomic analysis were conducted to assess lipid metabolism and regulatory pathways. Atg5 expression was manipulated in vivo using cholesterol-modified small interfering RNA. Lipid droplets (LDs) and lysosomes were labeled with BODIPY 493/503 and Lysotracker Red DND-99, respectively. Western blot, immunofluorescence (IF) staining, co-immunoprecipitation (CO-IP), transmission electron microscopy and microplate reader were used to explore protein expressions and interactions, cellular structures, and free fatty acid (FFA) content.

Results

Our results revealed that autophagy was activated in DED, as evidenced by lipidomic and transcriptomic analyses. Enhanced lipophagy was observed in HCECs exposed to hyperosmolarity, manifested by lysosome-LD co-localization and autophagic vacuoles containing LDs. Upregulation of Atg5 promoted lipophagy, leading to elevated cellular FFA levels, lipid peroxidation, and expression of ferroptosis markers. Interaction between Atg5 and perilipin3 was confirmed through CO-IP and IF. In the DED mouse model, Atg5 inhibition effectively ameliorated corneal damage, suppressed ferroptosis and ocular surface inflammation.

Conclusions

Our findings highlight the pivotal role of Atg5-mediated lipophagy in driving ferroptosis in corneal epithelial cells in DED, proposing Atg5 as a promising therapeutic target for mitigating ferroptosis-induced cell damage and inflammation in DED.

Preclinical evaluation of fenretinide against primary and metastatic intestinal type‑gastric cancer

In recent years there has been a decline in the incidence of gastric cancer, however the high mortality rate has remained constant. The present study evaluated the potential effects of the retinoid fenretinide on the viability and migration of two cell lines, AGS and NCI-N87, that represented primary and metastatic intestinal gastric cancer subtypes, respectively. It was determined that a similar2 dose of fenretinide reduced the viability of both the primary and metastatic cell lines. In addition, it was demonstrated that combined treatment with fenretinide and cisplatin may affect the viability of both primary and metastatic gastric cancer cells. Furthermore, a wound healing assay demonstrated an inhibitory effect for fenretinide on cell migration. As part of the characterization of the mechanism of action, the effect of fenretinide on reactive oxygen species production and lipid droplet content was evaluated, with the latter as an indirect means of assessing autophagy. These results support the hypothesis of combining using fenretinide with conventional therapies to improve survival rates in advanced or metastatic gastric cancer.

Lipid droplets as cell fate determinants in skeletal muscle

Lipid droplets (LDs) are dynamic organelles that communicate with other cellular components to orchestrate energetic homeostasis and signal transduction. In skeletal muscle, the presence and importance of LDs have been widely studied in myofibers of both rodents and humans under physiological conditions and in metabolic disorders. However, the role of LDs in myogenic stem cells has only recently begun to be unveiled. In this review we briefly summarize the process of LD biogenesis and degradation in the most prevalent model. We then review recent knowledge on LDs in skeletal muscle and muscle stem cells. We further introduce advanced methodologies for LD imaging and mass spectrometry that have propelled our understanding of the dynamics and heterogeneity of LDs.