Lipid Droplet-Derived Monounsaturated Fatty Acids Traffic via PLIN5 to Allosterically Activate SIRT1

Regulation of lipid metabolism: a new strategy for platelet storage

Transfusions of platelets are often used as prophylaxis in patients with hematologic malignancies and as treatment for active bleeding. However, platelets are in short supply due to the fact that they could only be kept for 5-7 days in vitro and they lose some of their functionality as a result of platelet storage lesions. To address this issue, refrigeration, cryopreservation and platelet additive solutions have been researched to determine their abilities to extend platelet storage duration. However, refrigerated platelets are quickly cleared after transfusion, while platelets in platelet additive solutions still present issues such as platelets quality and the risk of allergic reactions. Recent studies showed that changes in lipid metabolites during platelet storage and inadequate of fatty acid metabolism may also limit platelet shelf life and function. In this review, we address the principles of lipid metabolism during platelet storage and discuss the strategies for effective platelet storage systems. The findings of this review highlight the role of lipid metabolism during platelet storage, providing insights into future research focused on extending the preservation period and function of platelet.

Plasma-based untargeted metabolomics reveals potential biomarkers for screening and distinguishing of ovarian tumors

Ovarian cancer (OC), a leading cause of gynecological cancer mortality, is frequently detected at advanced stages due to asymptomatic early progression. This study investigates plasma-based untargeted metabolomics for identifying biomarkers to screen and differentiate ovarian tumors (OT). Plasma samples from OC, benign ovarian tumors (BOT), and healthy controls (HC) were analyzed. Samples were randomized into train and test sets, with differential metabolites screened via two-tailed Student's t-test and partial least squares discriminant analysis. ROC models evaluated discriminatory capacity. Key metabolites demonstrated high predictive value: TMAO and hippuric acid distinguished OT from HC (AUC > 0.95), while linoleic acid, alpha-linolenic acid, and arachidonic acid (AUC > 0.9) further supported OT screening. Kynurenine differentiated OC from BOT (AUC = 0.808). Reduced levels of specific lysophosphatidylcholines (LPC (17:0/0:0), LPC (15:0/0:0)) also distinguished OT from HC (AUC = 0.771-0.89). These findings suggest plasma metabolomics holds promise for noninvasive biomarker discovery in OT screening and distinguishing between malignant and benign cases, though further validation of metabolite quantification is warranted prior to clinical application.

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.

Transcriptional Response to Fasting Studied in the Liver of Mice That Express Phosphorylation Resistant Perilipin 5

Perilipin 5 (PLIN5) is a lipid droplet (LD) protein highly expressed in cells that actively oxidize fatty acids. Previous in vitro studies have revealed that PLIN5 phosphorylation (p-PLIN5) at serine 155 by protein kinase A is critical for transcriptional regulation of PPARa target genes by which PLIN5 adapt cells for fatty acid oxidation. We aim to determine the extent of p-PLIN5 in vivo and the consequence of impaired PLIN5 phosphorylation in the liver by using a whole-body knock-in of phosphorylation-resistant PLIN5 (SA/SA) in mice. Plin5 phosphorylation at S155 was increased in the liver LD fraction of fasted mice compared with that of fed mice by mass spectrometry (P < .05). Quantitative polymerase chain reaction of key lipid metabolism genes did not differ between wild-type and SA/SA liver upon fasting in both young and old males. Young SA/SA female mice showed a small but significant reduction in the expression of Ppara and Cpt1a genes in the liver after overnight fasting. Male SA/SA mice had higher fasting blood glucose (P < .05) without a difference in body weight, serum insulin, or serum lipids. IRS2 was reduced in the liver of fasted male SA/SA mice (P < .05). PLIN5 S155 phosphorylation has a limited impact on the upregulation of hepatic lipid metabolism genes important for fasting response in vivo in females and is largely dispensable in males. Impaired phosphorylation also had little effect on serum lipids or liver triglycerides. However, old SA/SA mice showed decreased IRS2 expression in the liver, which may contribute to glucose intolerance in SA/SA male mice.

Plin5: A potential therapeutic target for type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a kind of metabolic disease characterized by aberrant insulin secretion as a result of -cell loss or injury, or by impaired insulin sensitivity of peripheral tissues, which finally results in insulin resistance and a disturbance of glucose and lipid metabolism. Among them, lipid metabolism disorders lead to lipotoxicity through oxidative stress and inflammatory response, destroying the structure and function of tissues and cells. Abnormal lipid metabolism can lead to abnormal insulin signaling and disrupt glucose metabolism through a variety of pathways. Therefore, emphasizing lipid metabolism may be a crucial step in the prevention and treatment of T2DM. Plin5 is a lipid droplet surface protein, which can bi-directionally regulate lipid metabolism and plays an important role in lipolysis and fat synthesis. Plin5 can simultaneously decrease the buildup of free fatty acids in the cytoplasm, improve mitochondrial uptake of free fatty acids, speed up fatty acid oxidation through lipid drops-mitochondria interaction, and lessen lipotoxicity. In oxidative tissues like the heart, liver, and skeletal muscle, Plin5 is extensively expressed. And Plin5 is widely involved in β-cell apoptosis, insulin resistance, oxidative stress, inflammatory response and other pathological processes, which has important implications for exploring the pathogenesis of T2DM. In addition, recent studies have found that Plin5 is also closely related to T2DM and cancer, which provides a new perspective for exploring the relationship between T2DM and cancer.

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.

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.

Lipid metabolism in ferroptosis: Unraveling key mechanisms and therapeutic potential in cancer

Ferroptosis, a form of iron-dependent cell death driven by lipid peroxidation, has emerged as a critical area of research for cancer therapy. This review delves into the intricate relationship between lipid metabolism and ferroptosis, emphasizing the impact of lipidome remodeling on cancer cell susceptibility. We explore key mechanisms, such as the role of polyunsaturated fatty acids and phosphatidylethanolamines in ferroptosis induction, alongside the protective effects of monounsaturated fatty acids and their regulatory enzymes. We also discuss the influence of dietary fatty acids, lipid droplets, and the epithelial-to-mesenchymal transition on ferroptosis and cancer resistance. By integrating current findings on enzymatic regulation, lipid peroxidation pathways, and metabolic adaptations, this review highlights potential therapeutic strategies targeting lipid metabolism to enhance ferroptosis-based cancer treatments. Our goal is to provide a comprehensive overview that underscores the significance of lipid metabolic pathways in ferroptosis and their implications for developing novel cancer therapies.

The connection between fatty acids and inflammation in celiac disease; a deep exploring

The interplay between fatty acids (FAs) and celiac disease (CD) is a burgeoning field of research with significant implications for understanding the pathophysiology and potential therapeutic avenues for this autoimmune disorder. CD, triggered by gluten consumption in susceptible individuals, presents with a range of intestinal and extra-intestinal symptoms impacting various bodily functions. The disruption of intestinal tight junctions (TJs) by gluten proteins leads to increased gut permeability and subsequent inflammatory responses mediated by T-cells. FAs, crucial components of cell membranes, play diverse roles in inflammation and immune regulation. In fact, FAs have been shown to modulate inflammatory processes through various mechanisms. Studies have highlighted alterations in FA profiles in individuals with CD, indicating potential implications for disease pathogenesis and micronutrient deficiencies. Moreover, the exploration of FAs as biomarkers for CD diagnosis offers promising avenues for future research and therapeutic interventions. Understanding the intricate relationship between FAs and CD could lead to novel approaches in managing this complex autoimmune disorder. Therefore, this review article aims to provide an overview of the connection between FAs and inflammation in CD.

Spatially resolved rewiring of mitochondria-lipid droplet interactions in hepatic lipid homeostasis

Hepatic lipid accumulation, or Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD), is a significant risk factor for liver cancer. Despite the rising incidence of MASLD, the underlying mechanisms of steatosis and lipotoxicity remain poorly understood. Interestingly, lipid accumulation also occurs during fasting, driven by the mobilization of adipose tissue-derived fatty acids into the liver. However, how hepatocytes adapt to increased lipid flux during nutrient deprivation and what occurs differently in MASLD is not known. To investigate the differences in lipid handling in response to nutrient deficiency and excess, we developed a novel single-cell tissue imaging (scPhenomics) technique coupled with spatial proteomics. Our investigation revealed extensive remodeling of lipid droplet (LD) and mitochondrial topology in response to dietary conditions. Notably, fasted mice exhibited extensive mitochondria-LD interactions, which were rarely observed in Western Diet (WD)-fed mice. Spatial proteomics showed an increase in PLIN5 expression, a known mediator of LD-mitochondria interaction, in response to fasting. To examine the functional role of mitochondria-LD interaction on lipid handling, we overexpressed PLIN5 variants. We found that the phosphorylation state of PLIN5 impacts its capacity to form mitochondria-LD contact sites. PLIN5 S155A promoted extensive organelle interactions, triglyceride (TG) synthesis, and LD expansion in mice fed a control diet. Conversely, PLIN5 S155E expressing cells had fewer LDs and contact sites and contained less TG. Wild-type (WT) PLIN5 overexpression in WD-fed mice reduced steatosis and improved redox state despite continued WD consumption. These findings highlight the importance of organelle interactions in lipid metabolism, revealing a critical mechanism by which hepatocytes maintain homeostasis during metabolic stress. Our study underscores the potential utility of targeting mitochondria-LD interactions for therapeutic intervention.

Lipid metabolism: Novel approaches for managing idiopathic epilepsy

Epilepsy is a common neurological condition characterized by abnormal neuronal activity, often leading to cellular damage and death. There is evidence to suggest that lipid imbalances resulting in cellular death play a key role in the development of epilepsy, including changes in triglycerides, cholesterol, sphingolipids, phospholipids, lipid droplets, and bile acids (BAs). Disrupted lipid metabolism acts as a crucial pathological mechanism in epilepsy, potentially linked to processes such as cellular ferroptosis, lipophagy, and immune modulation of gut microbiota (thus influencing the gut-brain axis). Understanding these mechanisms could open up new avenues for epilepsy treatment. This study investigates the association between disturbances in lipid metabolism and the onset of epilepsy.

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.

RNA-seq analysis of small intestine transcriptional changes induced by starvation stress in piglets

Piglets may experience a variety of stress injuries, but the molecular regulatory mechanisms underlying these injuries are not well understood. In this study, we analysed the ileum of Large White (LW) and Mashen (MS) piglets at different times of starvation using chemical staining and transcriptome analysis. The intestinal barrier of piglets was damaged after starvation stress, but the intestinal antistress ability of MS piglets was stronger than LW piglets. A total of 8021 differentially expressed genes (DEGs) were identified in two breeds. Interestingly, the immune capacity (CHUK, TLR3) of MS piglets increased significantly after short-term starvation stress, while energy metabolism (NAGS, PLA2G12B, AGCG8) was predominant in LW piglets. After long-term starvation stress, the level of energy metabolism (PLIN5, PLA2G12B) was significantly increased in MS piglets. The expression of immune (HLA-DQB1, IGHG4, COL3A1, CD28, LAT) and disease (HSPA1B, MINPPI, ADH1C, GAL3ST1) related genes were significantly increased in two breeds of piglets. These results suggest that short-term stress mainly enhances immunity and energy metabolism in piglets, while long-term starvation produces greater stress on piglets, making it difficult for them to compensate for the damage to their bodies through self-regulation. This information can help improve the stress resistance of piglets through molecular breeding.

Mechanisms coupling lipid droplets to MASLD pathophysiology

Hepatic steatosis, the buildup of neutral lipids in lipid droplets (LDs), is commonly referred to as metabolic dysfunction-associated steatotic liver disease when alcohol or viral infections are not involved. Metabolic dysfunction-associated steatotic liver disease encompasses simple steatosis and the more severe metabolic dysfunction-associated steatohepatitis, characterized by inflammation, hepatocyte injury, and fibrosis. Previously viewed as inert markers of disease, LDs are now understood to play active roles in disease etiology and have significant nonpathological and pathological functions in cell signaling and function. These dynamic properties of LDs are tightly regulated by hundreds of proteins that coat the LD surface, controlling lipid metabolism, trafficking, and signaling. The following review highlights various facets of LD biology with the primary goal of discussing key mechanisms through which LDs promote the development of advanced liver diseases, including metabolic dysfunction-associated steatohepatitis.

Mechanisms of lipid droplet degradation

Lipid droplets (LDs) are subcellular organelles that play an integral role in lipid metabolism by regulating the storage and release of fatty acids, which are essential for energy production and various cellular processes. Lipolysis and lipophagy are the two major LD degradation pathways that mediate the utilization of lipids stored in these organelles. Recent studies have further uncovered alternative pathways, including direct lysosomal LD degradation and LD exocytosis. Here, we highlight recent findings that dissect the molecular basis of these diverse LD degradation pathways. Then, we discuss speculations on the crosstalk among these pathways and the potential unconventional roles of LD degradation.

A systematic review and meta-analysis of randomized controlled trials: effects of mediterranean diet and low-fat diet on liver enzymes and liver fat content of NAFLD

Background: Non-alcoholic fatty liver disease (NAFLD) has emerged as a leading cause of several chronic diseases, imposing a significant global economic burden. The Mediterranean diet (MD) and low-fat diet (LFD) are the two primary recommended dietary patterns that exhibit distinct positive effects on treating NAFLD. Objective: To investigate which of the two diets, MD and LFD, is more effective in the treatment of NAFLD. Methods: Randomized controlled trials (RCTs) up to April 2024 were searched for in PubMed, Web of Science, Medline, Scopus and Embase. Interventions included MD or LFD, with primary outcome measures being intrahepatic lipid, liver stiffness, triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, alanine aminotransferase, gamma-glutamyl transferase, and homeostasis model assessment of insulin resistance. Secondary outcomes included weight, waist circumference, and body mass index. Use of random effects meta-analysis to assess outcomes of interest. Results: meta-analysis revealed no significant differences between MD and LFD in improving liver enzymes, liver fat, and related indices in NAFLD patients. Our findings provide compelling evidence for patients and healthcare professionals, allowing patients to choose a dietary pattern that aligns with their preferences and disease conditions. In summary, both MD and LFD can equivalently ameliorate NAFLD in the short term. Conclusions: Our results show that MD and LFD have similar therapeutic effects on liver enzymes and liver fat content in patients with NAFLD in the short term. Furthermore, our meta-analysis results have also opened up a new avenue of thought as to whether similar effects are achieved by alternating MD and LFD on alternate days.

S-acylation of ATGL is required for lipid droplet homoeostasis in hepatocytes

Lipid droplets (LDs) are organelles specialized in the storage of neutral lipids, cholesterol esters and triglycerides, thereby protecting cells from the toxicity of excess lipids while allowing for the mobilization of lipids in times of nutrient deprivation. Defects in LD function are associated with many diseases. S-acylation mediated by zDHHC acyltransferases modifies thousands of proteins, yet the physiological impact of this post-translational modification on individual proteins is poorly understood. Here, we show that zDHHC11 regulates LD catabolism by modifying adipose triacylglyceride lipase (ATGL), the rate-limiting enzyme of lipolysis, both in hepatocyte cultures and in mice. zDHHC11 S-acylates ATGL at cysteine 15. Preventing the S-acylation of ATGL renders it catalytically inactive despite proper localization. Overexpression of zDHHC11 reduces LD size, whereas its elimination enlarges LDs. Mutating ATGL cysteine 15 phenocopies zDHHC11 loss, causing LD accumulation, defective lipolysis and lipophagy. Our results reveal S-acylation as a mode of regulation of ATGL function and LD homoeostasis. Modulating this pathway may offer therapeutic potential for treating diseases linked to defective lipolysis, such as fatty liver disease.

Ros-responsive nano-platform for lipid-specific fluorescence imaging of atherosclerosis

Fluorescent probes that specifically targeting Lipid droplets (LDs) have shown potential in biological imaging. Albeit, their in vivo applications are limited due to the hydrophobicity, low signal-to-noise ratio (SNR) and LDs-specificity. Thus, we designed a novel probe namely MeOND, and a reactive oxygen species (ROS)-responsive nano-platform to improve in vivo LDs-specific imaging. MeOND exhibits a remarkable twisted intramolecular charge transfer (TICT) effect with a strongly enhanced near-infrared emission in low-polarity lipid environment. Also, MeOND demonstrates satisfactory biocompatibility and superior intracellular LDs imaging capabilities. MeOND encapsulated nano-platform (MeOND@PMM) presented favorable water solubility and biocompatibility. MeOND@PMM remains stable in physiological conditions but quickly degrades in the environment of elevated ROS level. The released MeOND could then light up the intracellular LDs in atherosclerotic plaques. The design of the probe and nano-platform is expected to provide a better tool for the scientific research of LDs and LDs-related diseases.

Individual and interaction effects of monounsaturated fatty acids on their associations with hypertension in Chinese residents

Currently, associations between dietary intakes of individual monounsaturated fatty acids (MUFAs) and hypertension were not well disclosed, and the interaction effects of MUFAs on their associations with hypertension were unknown. Obesity was correlated with both MUFAs and hypertension, while if anthropometric obesity indices performed mediating roles in associations between MUFAs and hypertension remained underdetermined. In our study, 8509 Chinese adults investigated from 2004 to 2011 were included. Dietary information collection and physical examinations were performed at baseline and each timepoint of follow-up. As we found, inverse associations of MUFA17, MUFA18 and MUFA20 with hypertension were statistically significant after adjustments, hazard ratios (HRs) were 0.87, 0.90 and 0.91, respectively. MUFA15 was positively associated with hypertension, with an HR of 1.07 (95% confidence interval: 1.01, 1.12). By performing principal component analysis (PCA) to estimate the joint effects of MUFAs on hypertension, the PCA score of MUFAs was only inversely associated with blood pressure. No joint effect was observed in g-computation analyses. Both linear and nonlinear interactions of MUFAs on their associations with hypertension were estimated using restricted cubic spline analysis. The association between MUFA15 and hypertension was interacted by MUFA17, and the association between MUFA20 and hypertension was interacted by MUFA18. The mediation effects of body mass index and waist circumference were found on associations of hypertension with MUFA15, MUFA17 and MUFA20. Our findings suggested that associations with hypertension were different among individual MUFAs, and mutual interactions existed, implying that the utility of individual MUFAs might be recommended for estimating relationships between MUFAs and diseases. Moreover, fat accumulation might potentially underlie associations between MUFAs and hypertension.

Roles of lipid droplets and related proteins in metabolic diseases

Lipid droplets (LDs), which are active organelles, derive from the monolayer membrane of the endoplasmic reticulum and encapsulate neutral lipids internally. LD-associated proteins like RAB, those in the PLIN family, and those in the CIDE family participate in LD formation and development, and they are active players in various diseases, organelles, and metabolic processes (i.e., obesity, non-alcoholic fatty liver disease, and autophagy). Our synthesis on existing research includes insights from the formation of LDs to their mechanisms of action, to provide an overview needed for advancing research into metabolic diseases and lipid metabolism.

Resveratrol Alleviates Liver Fibrosis Induced by Long-Term Inorganic Mercury Exposure through Activating the Sirt1/PGC-1α Signaling Pathway

Liver disease has become an important risk factor for global health. Resveratrol (Res) is a natural polyphenol which is widely found in foods and has a variety of biological activities. This study investigated the role of the microbiota-gut-liver axis in the Res relieving the liver fibrosis induced by inorganic mercury exposure. Twenty-eight mice were divided into four groups (n = 7) and treated with mercuric chloride and/or Res for 24 weeks, respectively. The results showed that Res mitigated the ileum injury induced by inorganic mercury and restrained LPS and alcohol entering the body circulation. Network pharmacological and molecular analyses showed that Res alleviated oxidative stress, metabolism disorders, inflammation, and hepatic stellate cell activation in the liver. In conclusion, Res alleviates liver fibrosis induced by inorganic mercury via activating the Sirt1/PGC-1α signaling pathway and regulating the microbial-gut-liver axis, particularly, increasing the relative enrichment of Bifidobacterium in the intestinal tract.

Lycium barbarum polysaccharide ameliorates the accumulation of lipid droplets in adipose tissue via an ATF6/SIRT1-dependent mechanism

Lipid droplets (LDs) are dynamic organelles that store neutral lipids and are closely linked to obesity. Previous studies have suggested that Lycium barbarum polysaccharide (LBP) supplements can ameliorate obesity, but the underlying mechanisms remain unclear. In this study, we hypothesize that LBP alleviates LD accumulation in adipose tissue (AT) by inhibiting fat-specific protein 27 (Fsp27) through an activating transcription factor-6 (ATF6)/small-molecule sirtuin 1 (SIRT1)-dependent mechanism. LD accumulation in AT is induced in high-fat diet (HFD)-fed mice, and differentiation of 3T3-L1 preadipocytes (PAs) is induced. The ability of LBP to alleviate LD accumulation and the possible underlying mechanism are then investigated both in vivo and in vitro. The influences of LBP on the expressions of LD-associated genes ( ATF6 and Fsp27) are also detected. The results show that HFD and PA differentiation markedly increase LD accumulation in ATs and adipocytes, respectively, and these effects are markedly suppressed by LBP supplementation. Furthermore, LBP significantly activates SIRT1 and decreases ATF6 and Fsp27 expressions. Interestingly, the inhibitory effects of LBP are either abolished or exacerbated when ATF6 is overexpressed or silenced, respectively. Furthermore, SIRT1 level is transcriptionally regulated by LBP through opposite actions mediated by ATF6. Collectively, our findings suggest that LBP supplementation alleviates obesity by ameliorating LD accumulation, which might be partially mediated by an ATF6/SIRT1-dependent mechanism.

Lipid Droplet-Mitochondria Contacts in Health and Disease

The orchestration of cellular metabolism and redox balance is a complex, multifaceted process crucial for maintaining cellular homeostasis. Lipid droplets (LDs), once considered inert storage depots for neutral lipids, are now recognized as dynamic organelles critical in lipid metabolism and energy regulation. Mitochondria, the powerhouses of the cell, play a central role in energy production, metabolic pathways, and redox signaling. The physical and functional contacts between LDs and mitochondria facilitate a direct transfer of lipids, primarily fatty acids, which are crucial for mitochondrial β-oxidation, thus influencing energy homeostasis and cellular health. This review highlights recent advances in understanding the mechanisms governing LD-mitochondria interactions and their regulation, drawing attention to proteins and pathways that mediate these contacts. We discuss the physiological relevance of these interactions, emphasizing their role in maintaining energy and redox balance within cells, and how these processes are critical in response to metabolic demands and stress conditions. Furthermore, we explore the pathological implications of dysregulated LD-mitochondria interactions, particularly in the context of metabolic diseases such as obesity, diabetes, and non-alcoholic fatty liver disease, and their potential links to cardiovascular and neurodegenerative diseases. Conclusively, this review provides a comprehensive overview of the current understanding of LD-mitochondria interactions, underscoring their significance in cellular metabolism and suggesting future research directions that could unveil novel therapeutic targets for metabolic and degenerative diseases.

Hepatic lipid droplet-associated proteome changes distinguish dietary-induced fatty liver from glucose tolerance in male mice

Fatty liver is characterized by the expansion of lipid droplets (LDs) and is associated with the development of many metabolic diseases. We assessed the morphology of hepatic LDs and performed quantitative proteomics in lean, glucose-tolerant mice compared with high-fat diet (HFD) fed mice that displayed hepatic steatosis and glucose intolerance as well as high-starch diet (HStD) fed mice who exhibited similar levels of hepatic steatosis but remained glucose tolerant. Both HFD- and HStD-fed mice had more and larger LDs than Chow-fed animals. We observed striking differences in liver LD proteomes of HFD- and HStD-fed mice compared with Chow-fed mice, with fewer differences between HFD and HStD. Taking advantage of our diet strategy, we identified a fatty liver LD proteome consisting of proteins common in HFD- and HStD-fed mice, as well as a proteome associated with glucose tolerance that included proteins shared in Chow and HStD but not HFD-fed mice. Notably, glucose intolerance was associated with changes in the ratio of adipose triglyceride lipase to perilipin 5 in the LD proteome, suggesting dysregulation of neutral lipid homeostasis in glucose-intolerant fatty liver. We conclude that our novel dietary approach uncouples ectopic lipid burden from insulin resistance-associated changes in the hepatic lipid droplet proteome.NEW & NOTEWORTHY This study identified a fatty liver lipid droplet proteome and one associated with glucose tolerance. Notably, glucose intolerance was linked with changes in the ratio of adipose triglyceride lipase to perilipin 5 that is indicative of dysregulation of neutral lipid homeostasis.

Lipid droplets provide metabolic flexibility for cancer progression

A hallmark of cancer cells is their remarkable ability to efficiently adapt to favorable and hostile environments. Due to a unique metabolic flexibility, tumor cells can grow even in the absence of extracellular nutrients or in stressful scenarios. To achieve this, cancer cells need large amounts of lipids to build membranes, synthesize lipid-derived molecules, and generate metabolic energy in the absence of other nutrients. Tumor cells potentiate strategies to obtain lipids from other cells, metabolic pathways to synthesize new lipids, and mechanisms for efficient storage, mobilization, and utilization of these lipids. Lipid droplets (LDs) are the organelles that collect and supply lipids in eukaryotes and it is increasingly recognized that the accumulation of LDs is a new hallmark of cancer cells. Furthermore, an active role of LD proteins in processes underlying tumorigenesis has been proposed. Here, by focusing on three major classes of LD-resident proteins (perilipins, lipases, and acyl-CoA synthetases), we provide an overview of the contribution of LDs to cancer progression and discuss the role of LD proteins during the proliferation, invasion, metastasis, apoptosis, and stemness of cancer cells.

Molecular mechanisms of perilipin protein function in lipid droplet metabolism

Perilipins are abundant lipid droplet (LD) proteins present in all metazoans and also in Amoebozoa and fungi. Humans express five perilipins, which share a similar domain organization: an amino-terminal PAT domain and an 11-mer repeat region, which can fold into amphipathic helices that interact with LDs, followed by a structured carboxy-terminal domain. Variations of this organization that arose during vertebrate evolution allow for functional specialization between perilipins in relation to the metabolic needs of different tissues. We discuss how different features of perilipins influence their interaction with LDs and their cellular targeting. PLIN1 and PLIN5 play a direct role in lipolysis by regulating the recruitment of lipases to LDs and LD interaction with mitochondria. Other perilipins, particularly PLIN2, appear to protect LDs from lipolysis, but the molecular mechanism is not clear. PLIN4 stands out with its long repetitive region, whereas PLIN3 is most widely expressed and is used as a nascent LD marker. Finally, we discuss the genetic variability in perilipins in connection with metabolic disease, prominent for PLIN1 and PLIN4, underlying the importance of understanding the molecular function of perilipins.

Perilipin 5 regulates hepatic stellate cell activation and high-fat diet-induced non-alcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases globally. Hepatic stellate cells (HSCs) are the major effector cells of liver fibrosis. HSCs contain abundant lipid droplets (LDs) in their cytoplasm during quiescence. Perilipin 5 (PLIN 5) is a LD surface-associated protein that plays a crucial role in lipid homeostasis. However, little is known about the role of PLIN 5 in HSC activation.

METHODS

PLIN 5 was overexpressed in HSCs of Sprague-Dawley rats by lentivirus transfection. At the same time, PLIN 5 gene knockout mice were constructed and fed with a high-fat diet (HFD) for 20 weeks to study the role of PLIN 5 in NAFLD. The corresponding reagent kits were used to measure TG, GSH, Caspase 3 activity, ATP level, and mitochondrial DNA copy number. Metabolomic analysis of mice liver tissue metabolism was performed based on UPLC-MS/MS. AMPK, mitochondrial function, cell proliferation, and apoptosis-related genes and proteins were detected by western blotting and qPCR.

RESULTS

Overexpression of PLIN 5 in activated HSCs led to a decrease in ATP levels in mitochondria, inhibition of cell proliferation, and a significant increase in cell apoptosis through AMPK activation. In addition, compared with the HFD-fed C57BL/6J mice, PLIN 5 knockout mice fed with HFD showed reduced liver fat deposition, decreased LD abundance and size, and reduced liver fibrosis.

CONCLUSION

These findings highlight the unique regulatory role of PLIN 5 in HSCs and the role of PLIN 5 in the fibrosis process of NAFLD.

Lipid droplets and cellular lipid flux

Lipid droplets are dynamic organelles that store neutral lipids, serve the metabolic needs of cells, and sequester lipids to prevent lipotoxicity and membrane damage. Here we review the current understanding of the mechanisms of lipid droplet biogenesis and turnover, the transfer of lipids and metabolites at membrane contact sites, and the role of lipid droplets in regulating fatty acid flux in lipotoxicity and cell death.

Direct degradation and stabilization of proteins: New horizons in treatment of nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is featured with excessive hepatic lipid accumulation and its global prevalence is soaring. Nonalcoholic steatohepatitis (NASH), the severe systemic inflammatory subtype of NAFLD, is tightly associated with metabolic comorbidities, and the hepatocytes manifest severe inflammation and ballooning. Currently the therapeutic options for treating NASH are limited. Potent small molecules specifically intervene with the signaling pathways that promote pathogenesis of NASH. Nevertheless they have obvious adverse effects and show long-term ineffectiveness in clinical trials. It poses the fundamental question to efficiently and safely inhibit the pathogenic processes. Targeted protein degradation (TPD) belongs to the direct degradation strategies and is a burgeoning strategy. It utilizes the small molecules to bind to the target proteins and recruit the endogenous proteasome, lysosome and autophagosome-mediated degradation machineries. They effectively and specifically degrade the target proteins. It has exhibited promising therapeutic effects in treatment of cancer, neurodegenerative diseases and other diseases in a catalytic manner at low doses. We critically discuss the principles of multiple direct degradation strategies, especially PROTAC and ATTEC. We extensively analyze their emerging application in degradation of excessive pathogenic proteins and lipid droplets, which promote the progression of NASH. Moreover, we discuss the opposite strategy that utilizes the small molecules to recruit deubiquinases to stabilize the NASH/MASH-suppressing proteins. Their advantages, limitations, as well as the solutions to address the limitations have been analyzed. In summary, the innovative direct degradation strategies provide new insights into design of next-generation therapeutics to combat NASH with optimal safety paradigm and efficiency.

Lipid droplets, autophagy, and ageing: A cell-specific tale

Lipid droplets are the essential organelle for storing lipids in a cell. Within the variety of the human body, different cells store, utilize and release lipids in different ways, depending on their intrinsic function. However, these differences are not well characterized and, especially in the context of ageing, represent a key factor for cardiometabolic diseases. Whole body lipid homeostasis is a central interest in the field of cardiometabolic diseases. In this review we characterize lipid droplets and their utilization via autophagy and describe their diverse fate in three cells types central in cardiometabolic dysfunctions: adipocytes, hepatocytes, and macrophages.

Anti-Aging Drugs and the Related Signal Pathways

Aging is a multifactorial biological process involving chronic diseases that manifest from the molecular level to the systemic level. From its inception to 31 May 2022, this study searched the PubMed, Web of Science, EBSCO, and Cochrane library databases to identify relevant research from 15,983 articles. Multiple approaches have been employed to combat aging, such as dietary restriction (DR), exercise, exchanging circulating factors, gene therapy, and anti-aging drugs. Among them, anti-aging drugs are advantageous in their ease of adherence and wide prevalence. Despite a shared functional output of aging alleviation, the current anti-aging drugs target different signal pathways that frequently cross-talk with each other. At present, six important signal pathways were identified as being critical in the aging process, including pathways for the mechanistic target of rapamycin (mTOR), AMP-activated protein kinase (AMPK), nutrient signal pathway, silent information regulator factor 2-related enzyme 1 (SIRT1), regulation of telomere length and glycogen synthase kinase-3 (GSK-3), and energy metabolism. These signal pathways could be targeted by many anti-aging drugs, with the corresponding representatives of rapamycin, metformin, acarbose, nicotinamide adenine dinucleotide (NAD+), lithium, and nonsteroidal anti-inflammatory drugs (NSAIDs), respectively. This review summarized these important aging-related signal pathways and their representative targeting drugs in attempts to obtain insights into and promote the development of mechanism-based anti-aging strategies.

Fatty acid elongation regulates mitochondrial β-oxidation and cell viability in prostate cancer by controlling malonyl-CoA levels

Recently, the fatty acid elongation enzyme ELOVL5 was identified as a critical pro-metastatic factor in prostate cancer, required for cell growth and mitochondrial homeostasis. The fatty acid elongation reaction catalyzed by ELOVL5 utilizes malonyl-CoA as the carbon donor. Here, we demonstrate that ELOVL5 knockdown causes malonyl-CoA accumulation. Malonyl-CoA is a cellular substrate that can inhibit fatty acid β-oxidation in the mitochondria through allosteric inhibition of carnitine palmitoyltransferase 1A (CPT1A), the enzyme that controls the rate-limiting step of the long chain fatty acid β-oxidation cycle. We hypothesized that changes in malonyl-CoA abundance following ELOVL5 knockdown could influence mitochondrial β-oxidation rates in prostate cancer cells, and regulate cell viability. Accordingly, we find that ELOVL5 knockdown is associated with decreased mitochondrial β-oxidation in prostate cancer cells. Combining ELOVL5 knockdown with FASN inhibition to increase malonyl-CoA abundance endogenously enhances the effect of ELOVL5 knockdown on prostate cancer cell viability, while preventing malonyl-CoA production rescues the cells from the effect of ELOVL5 knockdown. Our findings indicate an additional role for fatty acid elongation, in the control of malonyl-CoA homeostasis, alongside its established role in the production of long-chain fatty acid species, to explain the importance of fatty acid elongation for cell viability.

A turn-on fluorescent probe for lipid-targeting imaging in human arterial aneurysm and fibrocalcific stenotic aortic valve

Fluorescence imaging techniques have shown remarkable performance in studying the biological functions of lipid droplets (LDs). However, the biological applications of the commercially available LDs probes suffer from insufficient specificity and low signal/noise ratio (SNR). Herein, we presented a novel near-infrared (NIR) lipid activatable fluorescence probe, namely Me2NND, with extremely low emission in water but significantly enhanced emission in the lipid environment. Me2NND presented good biocompatibility and impressive LDs-specific imaging ability in cells and tissues. Moreover, Me2NND has also shown good photostability and it could efficiently locate the distribution of LDs in human pathological samples of aortic aneurysms and fibrocalcific stenotic aortic valves. This study provided a novel turn-on probe Me2NND and would improve the bio-applications of LDs-specific probes.

Sirtuins and autophagy in lipid metabolism

Sirtuins are a family of NAD+ -dependent deacetylases that regulate some important biological processes, including lipid metabolism and autophagy, through their deacetylase function. Autophagy is a new discovery in the field of lipid metabolism, which may provide a new idea for the regulation of lipid metabolism. There are many tandem parts in the regulation process of lipid metabolism and autophagy of sirtuins protein family. This paper summarized these tandem parts and proposed the possibility of sirtuins regulating lipid autophagy, as well as the interaction and synergy between sirtuins protein family. Currently, some natural drugs have been reported to affect metabolism by regulating sirtuins, some of which regulate autophagy by targeting sirtuins.

Unsaturated fatty acid alters the immune response in non-small cell lung adenocarcinoma through regulation of HMGB1 trafficking

Cancer cell evasion of the immune response is critical to cancer development and metastases. The ability of clinicians to kickstart the immune system to target these rogue cells is an ever-growing area of research and medicine. In this study, we delved into the relationship between lipid metabolism, High Mobility Group Box 1 protein (HMGB1), and immune regulation within non-small cell lung adenocarcinoma (NSCLC), shedding light on novel therapeutic avenues and potential personalized approaches for patients. We found that the expression of stearoyl CoA desaturase 1 (SCD1) was decreased in NSCLC tumors compared to normal tissues. This emphasized the critical role of lipid metabolism in tumor progression. Interestingly, monounsaturated fatty acid (MUFA) availability impacted the expression of programmed death receptor ligand -1 (PD-L1), a pivotal immune checkpoint target in lung cancer cells and immune cells, suggesting a novel approach to modulating the immune response. This study uncovered a complex interplay between HMGB1, SCD1, and PD-L1, influencing the immunological sensitivity of tumors. Our work underscores the importance of understanding the intricate relationships between lipid metabolism and immune modulation to develop more effective NSCLC treatments and personalized therapies. As we continue to explore these connections, we hope to contribute to the ever-evolving field of cancer research, improving patient outcomes and advancing precision medicine in NSCLC.

lncRNA Hnscr Regulates Lipid Metabolism by Mediating Adipocyte Lipolysis

Obesity is a process of fat accumulation due to the imbalance between energy intake and consumption. Long noncoding RNA (lncRNA) Hnscr is crucial for metabolic regulation, but its roles in lipid metabolism during obesity are still unknown. In this article, we found that the expression of Hnscr gradually decreased in adipose tissues of diet-induced obese mice. Furthermore, the deletion of Hnscr promoted an increase in body weight and adipose tissue weight by upregulating the expression of lipogenesis genes and downregulating lipolysis genes in inguinal white adipose tissue (iWAT) and brown adipose tissue. In vitro knockdown of Hnscr in adipocytes resulted in reduced lipolysis of adipocytes. Overexpression of Hnscr by adenovirus or drug mimics showed the opposite. Mechanistically, Hnscr regulated adipose lipid metabolism by mediating the cyclic adenosine monophosphate/protein kinase A signaling pathway. This study identifies the initial characterization of Hnscr as a critical modifier that regulates lipid metabolism, suggesting that lncRNA Hnscr is a potential target for treating obesity.

TP53/p53 Facilitates Stress-Induced Exosome and Protein Secretion by Adipocytes

Besides the secretion of fatty acids, lipolytic stimulation of adipocytes results in the secretion of triglyceride-rich extracellular vesicles and some free proteins (e.g., fatty acid binding protein 4) that, in sum, affect adipose homeostasis as well as the development of metabolic disease. At the mechanistic level, lipolytic signals activate p53 in an adipose triglyceride lipase-dependent manner, and pharmacologic inhibition of p53 attenuates adipocyte-derived extracellular vesicle (AdEV) protein and FABP4 secretion. Mass spectrometry analyses of the lipolytic secretome identified proteins involved in glucose and fatty acid metabolism, translation, chaperone activities, and redox control. Consistent with a role for p53 in adipocyte protein secretion, activation of p53 by the MDM2 antagonist nutlin potentiated AdEV particles and non-AdEV protein secretion from cultured 3T3-L1 or OP9 adipocytes while the levels of FABP4 and AdEV proteins were significantly reduced in serum from p53-/- mice compared with wild-type controls. The genotoxin doxorubicin increased AdEV protein and FABP4 secretion in a p53-dependent manner and DNA repair-depleted ERCC1-/Δ-haploinsufficient mice expressed elevated p53 in adipose depots, along with significantly increased serum FABP4. In sum, these data suggest that lipolytic signals, and cellular stressors such as DNA damage, facilitate AdEV protein and FABP4 secretion by adipocytes in a p53-dependent manner.

ARTICLE HIGHLIGHTS

Dietary fatty acids activate or deactivate brown and beige fat

Brown adipose tissue (BAT) and beige fat have been documented to rapidly consume fatty acids (FAs) rather than deposit of lipid, and they have high capacity to dissipate energy via nonshivering thermogenesis, making BAT and beige fat potential organs to fight obesity and related chronic diseases. As the main substrate for thermogenesis and the basic constituent unit of triacylglycerol, FAs could modify BAT and remodel white adipose tissue (WAT) to beige fat. However, there are few comprehensive review covering the link between dietary FAs and thermogenic adipocyte..In this review, we described the metabolism of thermogenic adipose upon activation and comprehensively summarized publications on the dietary FAs that activate or deactivate BAT and beige fat. Specifically, eicosapentaenoic acid/docosahexaenoic acid (EPA/DHA), α-linolenic acid (α-ALA), conjugated linoleic acid (CLA), oleic acid (OA), long-chain saturated fatty acid (LC-SFA) and medium-chain fatty acid (MCFA). in addition, the influences on BAT function, WAT remodeling, and lipid metabolism, as well as delineated the possible mechanisms are also reviewed. Characterizing thermogenic or obesogenic dietary FAs may offer novel insight into dietary oil and nutritional treatment.

Perilipin 5 deficiency aggravates cardiac hypertrophy by stimulating lactate production in leptin-deficient mice

BACKGROUND

Perilipin 5 (Plin5) is well known to maintain the stability of intracellular lipid droplets (LDs) and regulate fatty acid metabolism in oxidative tissues. It is highly expressed in the heart, but its roles have yet to be fully elucidated.

METHODS

Plin5-deficient mice and Plin5/leptin-double-knockout mice were produced, and their histological structures and myocardial functions were observed. Critical proteins related to fatty acid and glucose metabolism were measured in heart tissues, neonatal mouse cardiomyocytes and Plin5-overexpressing H9C2 cells. 2-NBDG was employed to detect glucose uptake. The mitochondria and lipid contents were observed by MitoTracker and BODIPY 493/503 staining in neonatal mouse cardiomyocytes.

RESULTS

Plin5 deficiency impaired glucose utilization and caused insulin resistance in mouse cardiomyocytes, particularly in the presence of fatty acids (FAs). Additionally, Plin5 deficiency increased the NADH content and elevated the expression of lactate dehydrogenase (LDHA) in cardiomyocytes, which resulted in increased lactate production. Moreover, when fatty acid oxidation was blocked by etomoxir or LDHA was inhibited by GSK2837808A in Plin5-deficient cardiomyocytes, glucose utilization was improved. Leptin-deficient mice exhibited myocardial hypertrophy, insulin resistance and altered substrate utilization, and Plin5 deficiency exacerbated myocardial hypertrophy in leptin-deficient mice.

CONCLUSION

Our results demonstrated that Plin5 plays a critical role in coordinating fatty acid and glucose oxidation in cardiomyocytes, providing a potential target for the treatment of metabolic disorders in the heart.

Defensive-lipid droplets: Cellular organelles designed for antimicrobial immunity

Microbes have developed many strategies to subvert host organisms, which, in turn, evolved several innate immune responses. As major lipid storage organelles of eukaryotes, lipid droplets (LDs) are an attractive source of nutrients for invaders. Intracellular viruses, bacteria, and protozoan parasites induce and physically interact with LDs, and the current view is that they "hijack" LDs to draw on substrates for host colonization. This dogma has been challenged by the recent demonstration that LDs are endowed with a protein-mediated antibiotic activity, which is upregulated in response to danger signals and sepsis. Dependence on host nutrients could be a generic "Achilles' heel" of intracellular pathogens and LDs a suitable chokepoint harnessed by innate immunity to organize a front-line defense. Here, we will provide a brief overview of the state of the conflict and discuss potential mechanisms driving the formation of the 'defensive-LDs' functioning as hubs of innate immunity.

Tapping lipid droplets: A rich fat diet of intracellular bacterial pathogens

Lipid droplets (LDs) are dynamic and versatile organelles present in most eukaryotic cells. LDs consist of a hydrophobic core of neutral lipids, a phospholipid monolayer coat, and a variety of associated proteins. LDs are formed at the endoplasmic reticulum and have diverse roles in lipid storage, energy metabolism, membrane trafficking, and cellular signaling. In addition to their physiological cellular functions, LDs have been implicated in the pathogenesis of several diseases, including metabolic disorders, cancer, and infections. A number of intracellular bacterial pathogens modulate and/or interact with LDs during host cell infection. Members of the genera Mycobacterium, Legionella, Coxiella, Chlamydia, and Salmonella exploit LDs as a source of intracellular nutrients and membrane components to establish their distinct intracellular replicative niches. In this review, we focus on the biogenesis, interactions, and functions of LDs, as well as on their role in lipid metabolism of intracellular bacterial pathogens.

PLIN5 interacts with FATP4 at membrane contact sites to promote lipid droplet-to-mitochondria fatty acid transport

Cells adjust their metabolism by remodeling membrane contact sites that channel metabolites to different fates. Lipid droplet (LD)-mitochondria contacts change in response to fasting, cold exposure, and exercise. However, their function and mechanism of formation have remained controversial. We focused on perilipin 5 (PLIN5), an LD protein that tethers mitochondria, to probe the function and regulation of LD-mitochondria contacts. We demonstrate that efficient LD-to-mitochondria fatty acid (FA) trafficking and ß-oxidation during starvation of myoblasts are promoted by phosphorylation of PLIN5 and require an intact PLIN5 mitochondrial tethering domain. Using human and murine cells, we further identified the acyl-CoA synthetase, FATP4 (ACSVL4), as a mitochondrial interactor of PLIN5. The C-terminal domains of PLIN5 and FATP4 constitute a minimal protein interaction capable of inducing organelle contacts. Our work suggests that starvation leads to phosphorylation of PLIN5, lipolysis, and subsequent channeling of FAs from LDs to FATP4 on mitochondria for conversion to fatty-acyl-CoAs and subsequent oxidation.

Regulation of Monocyte Activation by PPARα Through Interaction With the cGAS-STING Pathway

Monocyte activation plays an important role in diabetic complications such as diabetic retinopathy (DR). However, the regulation of monocyte activation in diabetes remains elusive. Fenofibrate, an agonist of peroxisome proliferator-activated receptor-α (PPARα), has shown robust therapeutic effects on DR in patients with type 2 diabetes. Here we found that PPARα levels were significantly downregulated in monocytes from patients with diabetes and animal models, correlating with monocyte activation. Fenofibrate attenuated monocyte activation in diabetes, while PPARα knockout alone induced monocyte activation. Furthermore, monocyte-specific PPARα overexpression ameliorated, while monocyte-specific PPARα knockout aggravated monocyte activation in diabetes. PPARα knockout impaired mitochondrial function while also increasing glycolysis in monocytes. PPARα knockout increased cytosolic mitochondrial DNA release and activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway in monocytes under diabetic conditions. STING knockout or STING inhibitor attenuated monocyte activation induced by diabetes or by PPARα knockout. These observations suggest that PPARα negatively regulates monocyte activation through metabolic reprogramming and interaction with the cGAS-STING pathway.

Perilipin5 protects against non-alcoholic steatohepatitis by increasing 11-Dodecenoic acid and inhibiting the occurrence of ferroptosis

BACKGROUND

Non-alcoholic steatohepatitis (NASH) is a major contributor to liver cirrhosis and hepatocellular carcinoma. There remains no effective pharmacological therapy. The hepatic lipid metabolism and fatty acid β-oxidation are regulated by Perilipin5 (Plin5). However, it is yet unknown how Plin5 affects NASH and the molecular process.

METHODS

High-fat, high-cholesterol and high-fructose (HFHC) diets were used to mimic the progression of NASH in wild type (WT) mice and Plin5 knockout (Plin5 KO) mice. The degree of ferroptosis was measured by detecting the expression of key genes of ferroptosis and the level of lipid peroxide. The degree of NASH was judged by observing the morphology of the liver, detecting the expression of inflammation and fibrosis related genes of liver damage. Plin5 was overexpressed in the liver of mice by tail vein injection of adenovirus, and the process of NASH was simulated by methionine choline deficiency (MCD) diet. The occurrence of ferroptosis and NASH was detected by the same detection method. Targeted lipidomics sequencing was used to detect the difference in free fatty acid expression in the WT Plin5 KO group. Finally, it was verified in cell experiments to further study the effect of free fatty acids on ferroptosis of hepatocytes.

RESULTS

In various NASH models, hepatic Plin5 was dramatically reduced. Plin5 knockout (KO) worsened NASH-associated characteristics in mice given a high-fat/high-cholesterol (HFHC) diet, such as lipid accumulation, inflammation and hepatic fibrosis. It has been shown that ferroptosis is involved in NASH progression. We revealed that Plin5 KO in mice aggravated the degree of ferroptosis in NASH models. Conversely, overexpression of Plin5 significantly alleviated ferroptosis and further ameliorated progression of MCD-induced NASH. Analysis of livers obtained from HFHC diet-fed mice by targeted lipidomics revealed that 11-Dodecenoic acid was significantly decreased in Plin5 KO mice. Addition of 11-Dodecenoia acid to Plin5 knockdown hepatocytes effectively prevented ferroptosis.

CONCLUSION

Our study demonstrates that Plin5 protects against NASH progression by increasing 11-Dodecenoic acid level and further inhibiting ferroptosis, suggesting that Plin5 has therapeutic potential as a target for the management of NASH.

Energy restriction or improvements in diet quality: identifying the best pathway for a longer and healthier life

Obesity is a major risk factor for chronic non-communicable diseases (NCDs) and it has increased to epidemic proportions. Unhealthy diet represents a modifiable risk factor for both obesity and NCDs, however, there is no universal dietary intervention to improve obesity-related NCDs and particularly to reduce the risk for major adverse cardiovascular events. Energy restriction (ER) and diet quality changes, with and without ER, have been widely investigated in preclinical and clinical studies, however, the potential underlying mechanisms driving the benefits of those dietary interventions remain largely unclear. ER affects multiple metabolic, physiological, genetic, and cellular adaptation pathways associated with prolonged lifespan, particularly in preclinical models, while these benefits remain to be established in humans. Moreover, the sustainability of ER and its implementation across the different diseases remains challenging. On the other hand, diet quality with improvements, with or without ER, has been associated with more favorable long-term metabolic and cardiovascular outcomes. This narrative review will describe the role of ER and/or diet quality improvements on the risk for NCDs. It will also discuss the potential mechanisms of action underlying the potential beneficial effects of those dietary approaches.

The Janus-Faced Role of Lipid Droplets in Aging: Insights from the Cellular Perspective

It is widely accepted that nine hallmarks-including mitochondrial dysfunction, epigenetic alterations, and loss of proteostasis-exist that describe the cellular aging process. Adding to this, a well-described cell organelle in the metabolic context, namely, lipid droplets, also accumulates with increasing age, which can be regarded as a further aging-associated process. Independently of their essential role as fat stores, lipid droplets are also able to control cell integrity by mitigating lipotoxic and proteotoxic insults. As we will show in this review, numerous longevity interventions (such as mTOR inhibition) also lead to strong accumulation of lipid droplets in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, and mammalian cells, just to name a few examples. In mammals, due to the variety of different cell types and tissues, the role of lipid droplets during the aging process is much more complex. Using selected diseases associated with aging, such as Alzheimer's disease, Parkinson's disease, type II diabetes, and cardiovascular disease, we show that lipid droplets are "Janus"-faced. In an early phase of the disease, lipid droplets mitigate the toxicity of lipid peroxidation and protein aggregates, but in a later phase of the disease, a strong accumulation of lipid droplets can cause problems for cells and tissues.

Organelle interactions compartmentalize hepatic fatty acid trafficking and metabolism

Organelle interactions play a significant role in compartmentalizing metabolism and signaling. Lipid droplets (LDs) interact with numerous organelles, including mitochondria, which is largely assumed to facilitate lipid transfer and catabolism. However, quantitative proteomics of hepatic peridroplet mitochondria (PDM) and cytosolic mitochondria (CM) reveals that CM are enriched in proteins comprising various oxidative metabolism pathways, whereas PDM are enriched in proteins involved in lipid anabolism. Isotope tracing and super-resolution imaging confirms that fatty acids (FAs) are selectively trafficked to and oxidized in CM during fasting. In contrast, PDM facilitate FA esterification and LD expansion in nutrient-replete medium. Additionally, mitochondrion-associated membranes (MAM) around PDM and CM differ in their proteomes and ability to support distinct lipid metabolic pathways. We conclude that CM and CM-MAM support lipid catabolic pathways, whereas PDM and PDM-MAM allow hepatocytes to efficiently store excess lipids in LDs to prevent lipotoxicity.

Endocrine modulation of brain-skeleton axis driven by neural stem cell-derived perilipin 5 in the lipid metabolism homeostasis for bone regeneration

Factors released from the nervous system always play crucial roles in modulating bone metabolism and regeneration. How the brain-driven endocrine axes maintain bone homeostasis, especially under metabolic disorders, remains obscure. Here, we found that neural stem cells (NSCs) residing in the subventricular zone participated in lipid metabolism homeostasis of regenerative bone through exosomal perilipin 5 (PLIN5). Fluorescence-labeled exosomes tracing and histological detection identified that NSC-derived exosomes (NSC-Exo) could travel from the lateral ventricle into bone injury sites. Homocysteine (Hcy) led to osteogenic and angiogenic impairment, whereas the NSC-Exo were confirmed to restore it. Mecobalamin, a clinically used neurotrophic drug, further enhanced the protective effects of NSC-Exo through increased PLIN5 expression. Mechanistically, NSC-derived PLIN5 reversed excessive Hcy-induced lipid metabolic imbalance and aberrant lipid droplet accumulation through lipophagy-dependent intracellular lipolysis. Intracerebroventricular administration of mecobalamin and/or AAV-shPlin5 confirmed the effects of PLIN5-driven endocrine modulations on new bone formation and vascular reconstruction in hyperhomocysteinemic and high-fat diet models. This study uncovered a novel brain-skeleton axis that NSCs in the mammalian brain modulated bone regeneration through PLIN5-driven lipid metabolism modulation, providing evidence for lipid- or bone-targeted medicine development.

Lipid droplets and peroxisomes are co-regulated to drive lifespan extension in response to mono-unsaturated fatty acids

Dietary mono-unsaturated fatty acids (MUFAs) are linked to longevity in several species. But the mechanisms by which MUFAs extend lifespan remain unclear. Here we show that an organelle network involving lipid droplets and peroxisomes is critical for MUFA-induced longevity in Caenorhabditis elegans. MUFAs upregulate the number of lipid droplets in fat storage tissues. Increased lipid droplet number is necessary for MUFA-induced longevity and predicts remaining lifespan. Lipidomics datasets reveal that MUFAs also modify the ratio of membrane lipids and ether lipids-a signature associated with decreased lipid oxidation. In agreement with this, MUFAs decrease lipid oxidation in middle-aged individuals. Intriguingly, MUFAs upregulate not only lipid droplet number but also peroxisome number. A targeted screen identifies genes involved in the co-regulation of lipid droplets and peroxisomes, and reveals that induction of both organelles is optimal for longevity. Our study uncovers an organelle network involved in lipid homeostasis and lifespan regulation, opening new avenues for interventions to delay aging.