Journal of Lipid Research最新文献

Sphingolipids (SPLs) are bioactive lipids playing vital functions in cellular stress responses. The tumor suppressor p53 has been implicated in regulating few specific SPL enzymes; however, a comprehensive understanding of p53's overall impact on SPL metabolism is lacking. Here, we employed an integrative biochemical approach combining a novel flux tracing method (using d17dihydrosphingosine) with in situ enzymatic activity assays in the context of treatment with Doxorubicin (Dox), a DNA-damaging agent causing well-established dose-dependent activation of p53. Furthermore, our previous studies established dose-specific modulation of SPLs by sublethal (low dose) versus lethal (high dose) Dox. Here, we exploited this model to focus on the role of p53, and found: i) Both low and high Dox enhanced the rate of synthesis of select dihydroceramide species, d17:0/16:0, d17:0/18:0, and d17:0/20:0, implicating activation of specific ceramide synthases (CerS 1/4 and 5/6), with p53 dependence only at low Dox; ii) Novel p53-dependent suppression of dihydroceramide desaturase (DES) activity at both Dox doses; iii) Both doses of Dox impaired the synthesis of d17hexosylceramide and d17sphingomyelin, with an unanticipated role for p53 only at low Dox. iv) With respect to inhibition of d17sphingomyelin synthesis, an investigation into ceramide transport to the Golgi identified the ceramide transport protein 1 (CERT1) as a novel target of Dox (reduction of protein and activity) and p53 (reduction of activity, particularly at low Dox). These observations underscore p53's prominent role as a master regulator of SPL metabolism, inducing major remodeling of cellular SPL metabolism with extensive and integrated effects on sphingolipid synthesis.

Introduction: The HDL-specific phospholipid efflux (HDL-SPE) assay is a novel cell-free measure of HDL function that is inversely associated with coronary artery disease (CAD). However, the effect of exercise training on HDL-SPE is unknown. The purpose of this study was to examine the effect of exercise training on HDL-SPE in a large, diverse cohort free of overt disease.

Methods: Clinical and functional measures of HDL were taken before and after 20 weeks of endurance exercise training in 508 participants from the HERITAGE Family Study. Associations of HDL-SPE with HDL-related traits were examined using Pearson correlations at baseline and following exercise training (significance: p<7.4x10^-4). The effect of exercise training on HDL-SPE was examined using paired t-tests (significance: p<0.05).

Results: Mean (SD) HDL-SPE was 1.40 (0.19) and higher in females compared to males and in White participants compared to Black participants. Baseline HDL-SPE was strongly associated with HDL-C (r=0.45) and apoA-I (r=0.43, both p<6.9x10^-24), but not with measures of cholesterol efflux. Mean HDL-SPE increased (0.023, p=0.002) following exercise training, but these increases only occurred in those with the lowest baseline HDL-SPE levels. Change in HDL-SPE was associated with changes in HDL-C (r=0.27), medium HDL concentration (r=0.24), and apoA-I and HDL size (r=0.17, all p<1.3x10^-4).

Conclusion: HDL-SPE increased following regular exercise and changes in HDL-SPE were related to changes in HDL size and subclass concentrations. Our findings demonstrate that individuals at higher risk for CAD may experience the largest benefits from exercise training as related to this novel biomarker of HDL function.

Adipocytes play a central role in energy balance and metabolic health by storing excess nutrients as triglycerides in white adipose tissue (WAT). During physiological stress, sympathetic activation triggers lipolysis, releasing fatty acids and glycerol to meet systemic energy demands. Lipolytic activation in white adipocytes also increases their rate of oxygen consumption. Phosphorylation of signal transducer and activator of transcription 3 (STAT3) at Ser⁷²⁷ is a key regulatory event in lipolysis-driven respiration. Here, we identify c-Jun N-terminal kinase 1 (JNK1) as the kinase responsible for this essential phosphorylation event and a key regulator of oxidative metabolism in lipolytic adipocytes. We show that fatty acids produced by lipolysis activate JNK, which phosphorylates lipid droplet-associated STAT3, leading to inhibition of glycerol-3-phosphate acyltransferase 3 (GPAT3) and suppression of fatty acid re-esterification. This shift in lipid handling promotes mitochondrial uncoupling and increases energy expenditure. Pharmacological inhibition of JNK1 markedly reduced lipolysis-driven respiration without altering the rate of lipolysis. The critical role of JNK1 in promoting respiration in lipolytic adipocytes was verified using genetic knockdown studies. Notably, canonical upstream MAP kinase kinases were not required for JNK1 activation, suggesting a noncanonical pathway that senses acute increases in intracellular fatty acid levels. Together, these findings identify JNK1 as a metabolic sensor linking intracellular fatty acid levels to STAT3-mediated oxidative metabolism in adipocytes, with potential implications for energy balance and metabolic disease.

Lipid metabolism has long been implicated in diabetes, but there has been a paucity of population-based studies of the plasma lipidome and incident diabetes in cohorts of early-middle age. We used data from the U.S.-based Coronary Artery Risk Development in Young Adults (CARDIA) Study to identify lipidomics associated with 15-year incident diabetes (n=1,094; n=162 incident diabetes; [mean (SD) age: 45 (3.6); 58% women; 59% White race]). Plasma lipidomics was conducted using liquid-chromatography and infusion-mass spectrometry. Diabetes was defined at 5-, 10- and 15-year follow-ups as: fasting glucose ≥ 126 mg/dL,2-hour glucose tolerance test ≥ 200 mg/dL, HbA1c ≥ 6.5%, or reported diabetic medication use. We tested associations between individual lipids and incident diabetes with interval-censored, multivariable-adjusted Cox proportional hazards regression, accounting for multiple comparisons. We used differentially expression analysis to identify pathways up- and down-regulated in participants who developed diabetes over the 15-year period. Lastly, we used penalized regression (LASSO) to generate a lipid risk score (LRS) for incident diabetes (0.7 training, 0.3 testing). In hazards regression, 156 lipids including glycerolipids, glycerophospholipids, and sphingolipids, were associated with incident diabetes. Of these, 56 were also selected by LASSO regression as distinguishing participants who developed diabetes from those who did not. The LRS's ability to improve prediction of 15-yr incident diabetes past sociodemographic, behavioral, and clinical covariates was limited to the training set. Pathways leading to diacylglycerols and ceramides were upregulated, while pathways leading to hexosylceramides, lysophosphatidylethanolamines, triacylglycerols, and lysophosphatidylcholines were downregulated in incident diabetes cases. Our results in this cohort of early-middle-aged adults, supports further investigation into the roles of glycerophospholipid and sphingolipid metabolism in diabetes development, particularly for ceramides and hexosylceramides.

Oxidized lipids, once viewed as byproducts of oxidative stress, are now recognized as critical mediators linking metabolism, redox imbalance, and immunity. Generated through enzymatic and non-enzymatic oxidation of polyunsaturated fatty acids, oxidized phospholipids, lipid aldehydes, and oxidized lipoproteins act as context-dependent signals regulating immune activation, resolution, and metabolic adaptation. In metabolic inflammation, these lipids engage scavenger and Toll-like receptors to influence macrophage polarization, dendritic-cell function, and T-cell differentiation. Their context and concentration determine whether oxidized lipids amplify inflammation or promote immune tolerance. Accumulation of these species connects oxidative stress to immune dysfunction, contributing to diseases such as atherosclerosis, obesity, diabetes, cancer, and autoimmunity. This review synthesizes mechanistic and disease-specific insights into how oxidized lipids shape innate and adaptive immune responses in metabolic and autoimmune inflammation. As advances in lipidomics and immunology converge, a deeper understanding of oxidized-lipid regulation and function will enable the development of targeted strategies to restore immune and metabolic balance in chronic inflammatory disease.

Phosphatidylserine (PS), the most abundant negatively charged phospholipid in mammalian cells, is made in the endoplasmic reticulum (ER) but concentrated in the plasma membrane (PM). Similarly, cellular cholesterol is synthesised in the ER, yet enriched in the PM. Recently, PS has been shown to govern the transport of low-density lipoprotein (LDL)-derived cholesterol from the PM to the ER. Here, we investigated how cholesterol regulates delivery of PS from the ER to PM by the lipid-transfer proteins, ORP5 and ORP8. Adding exogenous cholesterol markedly increased the level of PI(4,5)P₂ on the PM, which recruited ORP5/8 to promote the delivery of PS to the PM from the ER. Similar results were also obtained when the level of PM cholesterol was increased upon sphingomyelinase treatment. The increased delivery of PS to the PM helps recruit GRAMD1b, a cholesterol carrier transporting cholesterol from the PM to the ER. Importantly, we show ORP5 interacts with GRAMD1b, and this interaction further facilitates the recruitment of GRAMD1b to the PM. Our results thus unveil a new mechanism by which excess PM cholesterol promotes its own trafficking to the ER via PI(4,5)P₂ and ORP5/8. Our results also provide fundamental new insights into how two major lipid species, PS and cholesterol, can impact each other's cellular homeostasis.

Primary Coenzyme Q10 (CoQ₁₀) deficiency is a rare mitochondrial disorder caused by mutations in genes involved in CoQ biosynthesis (e.g., COQ4) that result in impaired mitochondrial respiration, oxidative stress, and dysfunction across multiple organ systems due to decreased mitochondrial levels of CoQ₁₀. Although oral CoQ₁₀ supplementation has been examined for standard of care, poor absorption and inadequate tissue and intracellular distribution have resulted in a lack of clinically significant efficacy. BPM31510 is a lipid nanoparticle formulation of oxidized CoQ₁₀ designed to improve bioavailability and targeted uptake into the mitochondria. In the current study, we assessed the efficacy of BPM31510 to increase CoQ levels in Coq4^F147C mice, a novel genetic knock-in model of primary CoQ deficiency. CoQ₉, the main form of CoQ in mice, and CoQ₁₀ were significantly decreased in brain, kidney, heart, and muscle of Coq4^F147C mice compared to Coq4^+/+ mice. BPM31510 treatment significantly increased oxidized CoQ₁₀ levels across all tissues, mediated by the nanoliposome biodistribution of oxidized CoQ₁₀ in BPM31510. MALDI-MSI demonstrated regional and spatial restoration of CoQ₁₀ within the brain, including the cerebellum, myocardium, and renal cortex of Coq4^F147C mice. These results demonstrate that BPM31510 successfully concentrates pharmacologically active CoQ₁₀ in target tissues that are not reachable with oral therapy, in a genetic model of primary CoQ deficiency. We enabled the visualization of sub-organ CoQ₁₀ localization to specifically demonstrate CoQ₁₀ restoration. This study establishes proof-of-concept for spatial quinomics, a new methodology that combines spatial metabolomics with quinomics to evaluate next-generation CoQ₁₀-based therapeutics for mitochondrial disorders.

Background & aims: Very low-density lipoproteins (VLDLs) are crucial for maintaining liver and whole-body lipid homeostasis. Limited knowledge exists regarding the lipidation process of VLDL. Endoplasmic reticulum (ER) luminal lipid droplets (LLDs) have been suggested to provide lipids for VLDL lipidation and maturation. Seipin, an integral membrane protein of the ER, plays key roles in the formation of cytoplasmic LDs (CLDs) and adipocyte differentiation. Surprisingly, seipin is hardly detectable in hepatocytes. Given the critical contribution of seipin in forming CLDs, we hypothesize that the absence of seipin in hepatocytes might ensure the proper formation of LLDs and the lipidation and assembly of VLDLs.

Methods: To explore the functional interactions between CLDs, LLDs and VLDLs, we generated liver-specific human seipin overexpression (AAV-hSeipin) mice using adeno-associated virus (AAV). We examined hepatic lipid accumulation, plasma lipid levels, VLDL lipidation, and liver pathology using biochemical, histological, and electron microscopy techniques.

Results: Liver-specific overexpression of seipin resulted in increased accumulation of CLDs in hepatocytes, accompanied by reduced plasma triacylglycerol and cholesterol levels. VLDL lipidation was severely impaired in AAV-hSeipin mice. When subjected to a high-fat, high-cholesterol diet, AAV-hSeipin mice developed more severe hepatic inflammation and fibrosis.

Conclusions: These findings suggest that enhanced formation of CLDs driven by seipin may channel lipids storage towards the cytoplasm of hepatocytes, thereby impeding the biogenesis of LLDs and causing defective VLDL lipidation in the ER lumen. Our results thus provide important new insights into the connection between the biogenesis of CLDs and LLDs, as well as VLDL assembly.

Long-term consumption of high-fat diet (HFD) leads to energy surplus, resulting in excessive adipose tissue (AT) accumulation and dysfunction. Kiss1 is known to play a role in the metabolic regulation of AT. To explore the involvement of Kiss1 in mediating the effects of energy surplus induced by HFD, we conducted an 8-week intervention combining aerobic exercise and HFD in mice with AT-specific knockout (KO) and overexpression of Kiss1, along with HFD treatment in Kiss1-KO 3T3-L1 cells. Our results revealed that in perigonadal visceral AT (PgVAT) of female mice, the expression of Kiss1 and FASN is positively correlated. Additionally, Kiss1 participate the fatty acid (FA) synthesis pathway in PgVAT of female mice. When we overexpressed Kiss1 in AT of female mice, we found that Aerobic exercise reduced FASN levels by downregulating Kiss1 expression in PgVAT, thereby may suppressing the FA synthesis capacity. This study provides novel insights for developing targeted therapeutic strategies against obesity and associated metabolic disorders.

In recent studies, acute physiological stress has been shown to enhance liver gluconeogenesis by activating β3-adrenergic receptor (ADRB3)-dependent IL-6 production in brown adipocytes, effectively fueling "fight or flight" responses. However, the specific molecular mechanism of this IL-6 production in an ADRB3-dependent manner is not fully understood. ADRB3 regulates multiple metabolic programs in adipose tissue, including thermogenesis, lipolysis and glucose uptake, by activating cAMP-PKA-CREB signaling. Our previous studies revealed that the transcription factor KLF7 transcriptionally induces IL-6 expression in white adipocytes. Using KLF7-adipocyte knockout mice, we showed that KLF7 is also required for ADRB3-induced IL-6 production during stress. cAMP-PKA-CREB signaling mediates this transduction via stress and ADRB3 agonist administration in a mouse model in vivo, as well as in brown adipocytes cultured in vitro. CREB positively regulates KLF7 transcription by binding to the promoter of KLF7. These findings indicate that stress-induced IL-6 production is dependent on KLF7 in adipocytes. KLF7, as a target gene of CREB, responds to ADRB3 activation to increase endocrine IL-6 in a cAMP-PKA-CREB signaling-dependent manner. Our study provides a new theoretical basis for elucidating and enriching the novel mechanism of stress-induced IL-6 production in adipocytes.