Stearate-derived very long-chain fatty acids are indispensable to tumor growth

Exploring the role of ELOVLs family in lung adenocarcinoma based on bioinformatic analysis and experimental validation

BACKGROUND

The role of lipid metabolic reprogramming in the development of various types of cancer has already been established. However, the exact biological function and significance of the elongation of very-long-chain fatty acids (ELOVLs) gene family, which can affect fatty acid metabolism, is still not well understood in lung adenocarcinoma (LUAD). The aim of our study is to explore whether there are genes related to the pathogenesis of LUAD in the ELOVLs family, and even to guide clinical medication and potential prognostic indicators.

METHODS

Gene expression profiling interactive analysis (GEPIA), human protein atlas (HPA), cBioPortal, Kaplan-Meier (KM) plotter, single-sample Gene Set Enrichment Analysis (ssGSEA) algorithm and SubMap algorithms were utilized to analyze the role of ELOVLs in the LUAD. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, cell counting kit-8 (CCK8), colony formation, wound healing, transwell migration assays and fatty acid metabolism detection were employed to confirm the significant role of ELOVL6 in vitro experiment.

RESULTS

Our results revealed that mRNA expression levels of ELOVL2, ELOVL4 and ELOVL6 and protein expression levels of ELOVL5 and ELOVL6 were elevated in LUAD tissues compared to normal subjects. The low-expressing ELOVL6 group showed superior overall survival (OS) and disease-specific survival (DSS) versus the high-expressing group. Meanwhile, patients with low-ELOVL6 expression were more sensitive to the 4 representative chemotherapeutic agents. In vitro, we revealed that interfering with ELOVL6 could influence the viability, proliferation, migration capacity and fatty acid metabolism of LUAD cells (A549 and H1299).

CONCLUSIONS

Our study indicated that ELOVL6 could be used as an indicator to evaluate the prognosis and therapeutic effect, and even potential therapeutic target for patients with LUAD.

Theoretical framework and emerging challenges of lipid metabolism in cancer

Elevated lipid metabolism is one of hallmarks of malignant tumors. Lipids not only serve as essential structural components of biological membranes but also provide energy and substrates for the proliferation of cancer cells and tumor growth. Cancer cells meet their lipid needs by coordinating the processes of lipid absorption, synthesis, transport, storage, and catabolism. As research in this area continues to deepen, numerous new discoveries have emerged, making it crucial for scientists to stay informed about the developments of cancer lipid metabolism. In this review, we first discuss relevant concepts and theories or assumptions that help us understand the lipid metabolism and -based cancer therapies. We then systematically summarize the latest advancements in lipid metabolism including new mechanisms, novel targets, and up-to-date pre-clinical and clinical investigations of anti-cancer treatment with lipid metabolism targeted drugs. Finally, we emphasize emerging research directions and therapeutic strategies, and discuss future prospective and emerging challenges. This review aims to provide the latest insights and guidance for research in the field of cancer lipid metabolism.

Modeling compound lipid homeostasis using stable isotope tracing

Lipids represent the most diverse pool of metabolites found in cells, facilitating compartmentation, signaling, and other functions. Dysregulation of lipid metabolism is linked to disease states such as cancer and neurodegeneration. However, limited tools are available for quantifying metabolic fluxes across the lipidome. To directly measure reaction fluxes encompassing compound lipid homeostasis, we applied stable isotope tracing, liquid chromatography-high-resolution mass spectrometry, and network-based isotopologue modeling to non-small cell lung cancer (NSCLC) models. Compound lipid metabolic flux analysis (CL-MFA) enables the concurrent quantitation of fatty acid synthesis, elongation, headgroup assembly, and salvage reactions within virtually any biological system. Here, we resolve liver kinase B1 (LKB1)-mediated regulation of sphingolipid recycling in NSCLC cells and precision-cut lung slice cultures. We also demonstrate that widely used tissue culture conditions drive cells to upregulate fatty acid synthase flux to supraphysiological levels. Finally, we identify previously uncharacterized isozyme specificity of ceramide synthase inhibitors. These results highlight the ability of CL-MFA to quantify lipid cycling in biological systems to discover biological function and elucidate molecular mechanisms in membrane lipid metabolism.

A fatty acid elongase complex regulates cell membrane integrity and septin-dependent host infection by the rice blast fungus

Very-long-chain fatty acids (VLCFAs) regulate biophysical properties of cell membranes to determine growth and development of eukaryotes, such as the pathogenesis of the rice blast fungus Magnaporthe oryzae. The fatty acid elongase Elo1 regulates pathogenesis of M. oryzae by modulating VLCFA biosynthesis. However, it remains unknown whether and how Elo1 associates with other factors to regulate VLCFA biosynthesis in fungal pathogens. Here, we identified Ifa38, Phs1 and Tsc13 as interacting proteins of Elo1 by proximity labelling in M. oryzae. Elo1 associated with Ifa38, Phs1 and Tsc13 on the endoplasmic reticulum (ER) membrane to control VLCFA biosynthesis. Targeted gene deletion mutants Δifa38, Δphs1 and Δtsc13 were all similarly impaired as Δelo1 in vegetative growth, conidial morphology, stress responses in ER, cell wall and membrane. These deletion mutants also displayed severe damage in cell membrane integrity and failed to organize the septin ring that is essential for penetration peg formation and pathogenicity. Our study demonstrates that M. oryzae employs a fatty acid elongase complex to regulate VLCFAs for maintaining or remodelling cell membrane structure, which is important for septin-mediated host penetration.

Prediction of prognosis and immunotherapy efficacy based on metabolic landscape in lung adenocarcinoma by bulk, single-cell RNA sequencing and Mendelian randomization analyses

Immunotherapy has been a remarkable clinical advancement in cancer treatment, but only a few patients benefit from it. Metabolic reprogramming is tightly associated with immunotherapy efficacy and clinical outcomes. However, comprehensively analyzing their relationship is still lacking in lung adenocarcinoma (LUAD). Herein, we evaluated 84 metabolic pathways in TCGA-LUAD by ssGSEA. A matrix of metabolic pathway pairs was generated and a metabolic pathway-pair score (MPPS) model was established by univariable, LASSO, multivariable Cox regression analyses. The differences of metabolic reprogramming, tumor microenvironment (TME), tumor mutation burden and drug sensitivity in different MPPS groups were further explored. WGCNA and 117 machine learning algorithms were performed to identify MPPS-related genes. Single-cell RNA sequencing and in vitro experiments were used to explore the role of C1QTNF6 on TME. The results showed MPPS model accurately predicted prognosis and immunotherapy efficacy of LUAD patients regardless of sequencing platforms. High-MPPS group had worse prognosis, immunotherapy efficacy and lower immune cells infiltration, immune-related genes expression and cancer-immunity cycle scores than low-MPPS group. Seven MPPS-related genes were identified, of which C1QTNF6 was mainly expressed in fibroblasts. High C1QTNF6 expression in fibroblasts was associated with more infiltration of M2 macrophage, Treg cells and less infiltration of NK cells, memory CD8+ T cells. In vitro experiments validated silencing C1QTNF6 in fibroblasts could inhibit M2 macrophage polarization and migration. The study depicted the metabolic landscape of LUAD and constructed a MPPS model to accurately predict prognosis and immunotherapy efficacy. C1QTNF6 was a promising target to regulate M2 macrophage polarization and migration.

Hypoxia expedites the progression of papillary thyroid carcinoma by promoting the CPT1A-mediated fatty acid oxidative pathway

Hypoxia has been reported to promote the proliferation and migration of thyroid cancer, while the special mechanism was still unclear. HIF-1α/carnitine palmitoyl-transferase 1A (CPT1A) was found to be associated with papillary thyroid carcinoma (PTC) but the biological role of CPT1A in PTC was not explored. The effects of hypoxia and carnitine palmitoyl-transferase 1A (CPT1A) expression on PTC cells were determined by cell counting kit-8 assay, detection of oxidative stress, inflammation response and mitochondrial membrane motential (MMP). Oil Red O staining and the detection of free fatty acids were performed to assess the status of lipid metabolism. Flow cytometric analysis was performed to assess cell apoptosis. Quantitative polymerase chain reaction (qPCR) and western blot analysis were applied to investigate the expressions of CPT1A and HIF-1α and the molecules involved cell function. The expressions of CPT1A and HIF-1α were significantly increased in PTC cells with or without hypoxia treatment. CPT1A overexpression or silencing promoted or inhibited cell viability, and hypoxia further repressed cell viability. In addition, CPT1A overexpression alleviates hypoxia-induced increased oxidative stress, inflammation response and elevated MMP. CPT1A overexpression enhanced palmitic acid-induced decreased cell growth, enhanced the metabolic capacity of free fatty acid and suppressed cell apoptosis. Animal experiments showed that CPT1A overexpression promoted PTC tumor growth, reduced lipid deposition, oxidative stress and inflammation, as well as enhancing cell function indicators. However, CPT1A silencing showed the opposite effects both in vitro and in vivo. Hypoxia induces the high expression of HIF-1α/CPT1A, thereby reprogramming the lipid metabolism of PTC cells for adapting the hypoxia environment, meanwhile inhibiting the cell damage and apoptosis caused by oxidative stress.

A study on cholesterol-cholesteryl ester metabolic homeostasis and drug intervention in hyperlipidemic hamsters using UHPLC-MS/MS

Hyperlipidemia is a global metabolic disorder characterized by dysregulation of lipid metabolism. This dysregulation is closely associated with the altered homeostasis of cholesterol-cholesteryl ester (CE) metabolism in systemic circulation, and some organs. Additionally, the relationship between oxidized cholesteryl ester (oxCE) and the disease has also gained attention. Currently, there is a lack of comprehensive research on the alterations in cholesterol-CE metabolism in the context of hyperlipidemia, as well as the characteristics of lipid-lowering agents in regulating this metabolic state. Therefore, 40 oxCEs were identified in the hamster liver sample, and novel ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) methods were established for simultaneous analysis of cholesterol, 57 CEs, and 40 oxCEs in the serum, liver, adipose tissue, and intestine of hyperlipidemic hamsters. This study investigated the metabolic alterations between cholesterol-CE/oxCE in hyperlipidemic hamsters and those treated with lipid-lowering agents, including the Niemann-Pick-C1 like-1 protein (NPC1L1) inhibitor ezetimibe and the acyl coenzyme A: cholesterol acyltransferase (ACAT) inhibitor avasimibe. The study findings demonstrate metabolic disorders in cholesterol-CE/oxCE homeostasis in hyperlipidemic hamsters. Lipid-lowering agent therapy can improve the metabolic dysregulation caused by hyperlipidemia, with distinct characteristics: ezetimibe is more effective in reducing cholesterol, while avasimibe is more effective in reducing CEs/oxCEs. Eight potential biomarkers indicating the dysregulation of cholesterol-CE metabolism caused by hyperlipidemia and its improvement by lipid-lowering agents have been identified in the serum. This study offers new insights into the hyperlipidemia pathophysiology and the mechanisms of lipid-lowering agents from a novel perspective on cholesterol-CE/oxCE metabolic homeostasis.

Evaluation of the causal effects of blood metabolites on irritable bowel syndrome: Mendelian randomization

BACKGROUND

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder characterized by abdominal pain, discomfort, and changes in bowel habits. The mechanism underlying IBS remains unclear, and little evidence exists for clarifying the causal relationship between blood metabolites and IBS.

METHODS

We conducted a Mendelian randomization (MR) study using two samples. Exposure data for 7824 Europeans were extracted from a genome-wide association study (GWAS) on metabolite levels. The IBS GWAS data from the GWAS database were used for the initial analysis. The primary analysis of causal relationships was conducted using inverse-variance weighting (IVW) with MR-Egger and weighted medians as supplementary analyses. Sensitivity analyses were performed using a combination of the Cochran's Q test, MR-Egger intercept test, Mendelian randomization pleiotropy residual sum and outlier, and leave-one-out analysis. For significant associations, replication and meta-analyses were performed using additional independent IBS case GWAS data released by the FinnGen Consortium R9. To identify the metabolites, score regression, confounding analysis, and reverse MR were performed to further assess the causal relationships between the metabolites.

RESULTS

After rigorous screening, we identified four known metabolites to be associated with IBS (stearate, odds ratio [OR]: 0.74, 95% confidence interval [CI]: 0.59-0.92; arginine, OR: 1.36, 95% CI: 1.07-1.74; 1-palmitoylglycerol, OR:1.49, 95% CI: 1.07-2.07; 1-palmitoylglycerophosphoinositol, OR: 0.84, 95% CI: 0.71-0.99).

CONCLUSIONS

MR analysis revealed a causal relationship between the four metabolites and IBS, providing preliminary evidence for the pathogenesis of IBS. Our results provide novel insights into the potential biomarkers of IBS.

Differences in Absorption and Metabolism between Structured 1,3-Oleate-2-palmitate Glycerol and 1-Oleate-2-palmitate-3-linoleate Glycerol on C57BL/6J Mice

This study investigated differences in absorption and metabolism between 1,3-oleate-2-palmitate glycerol (OPO) and 1-oleate-2-palmitate-3-linoleate glycerol (OPL) using C57BL/6J mice. OPL was associated with higher postprandial plasma total triacylglycerol (TG), low-density lipoprotein cholesterol (LDL-C) concentrations, and the ratio of LDL-C to high-density lipoprotein cholesterol (HDL-C) compared to those of OPO (p > 0.05). OPO significantly increased postprandial oleic acid (OA) concentrations compared to OPL over the entire monitoring period (p < 0.05), while OPL significantly elevated linoleic acid (LA) levels compared to OPO (p < 0.05). After 1 month of feeding, the mice in both OPO and OPL groups showed lower final weight, weight gain, and liver TG, LDL-C, and LDL/HDL concentrations compared to the control (soybean oil) group. Lipidomics results showed that OPO increased the biosynthesis of very long-chain fatty acids and decreased the abundance of AcCa (16:1), AcCa (18:2), AcCa (18:1), AcCa (16:0), CarE (16:0), and CarE (16:1) relative to OPL. These lipid metabolites were positively correlated with liver TG, LDL-C, and LDL/HDL levels and negatively related to peroxisome proliferator-activated receptors α (PPARα) and acyl-CoA oxidase (ACOX1) expression. This study showed differences in physiologic functions between OPO and OPL and provided support for the future application of OPL in infant formula.

Integrating Single-Cell RNA-Seq and Bulk RNA-Seq Data to Explore the Key Role of Fatty Acid Metabolism in Breast Cancer

Cancer immune escape is associated with the metabolic reprogramming of the various infiltrating cells in the tumor microenvironment (TME), and combining metabolic targets with immunotherapy shows great promise for improving clinical outcomes. Among all metabolic processes, lipid metabolism, especially fatty acid metabolism (FAM), plays a major role in cancer cell survival, migration, and proliferation. However, the mechanisms and functions of FAM in the tumor immune microenvironment remain poorly understood. We screened 309 fatty acid metabolism-related genes (FMGs) for differential expression, identifying 121 differentially expressed genes. Univariate Cox regression models in The Cancer Genome Atlas (TCGA) database were then utilized to identify the 15 FMGs associated with overall survival. We systematically evaluated the correlation between FMGs' modification patterns and the TME, prognosis, and immunotherapy. The FMGsScore was constructed to quantify the FMG modification patterns using principal component analysis. Three clusters based on FMGs were demonstrated in breast cancer, with three patterns of distinct immune cell infiltration and biological behavior. An FMGsScore signature was constructed to reveal that patients with a low FMGsScore had higher immune checkpoint expression, higher immune checkpoint inhibitor (ICI) scores, increased immune microenvironment infiltration, better survival advantage, and were more sensitive to immunotherapy than those with a high FMGsScore. Finally, the expression and function of the signature key gene NDUFAB1 were examined by in vitro experiments. This study significantly demonstrates the substantial impact of FMGs on the immune microenvironment of breast cancer, and that FMGsScores can be used to guide the prediction of immunotherapy efficacy in breast cancer patients. In vitro experiments, knockdown of the NDUFAB1 gene resulted in reduced proliferation and migration of MCF-7 and MDA-MB-231 cell lines.

Alteration of Colonic Bacterial and Fungal Composition and Their Inter- and Intra-Kingdom Interaction in Patients with Adenomas with Low-Grade Dysplasia

Colorectal cancer (CRC) develops from pre-cancerous cellular lesions in the gut epithelium and mainly originates from specific types of colonic adenomas with dysplasia. However, gut microbiota signatures among sampling sites in patients with colorectal adenomas with low-grade dysplasia (ALGD) and normal control (NC) remain uncharacterized. To characterize gut microbial and fungal profiles in ALGD and normal colorectal mucosa tissues. We used 16S and ITS1-2 rRNA gene sequencing and bioinformatics analysis on the microbiota of ALGD and normal colorectal mucosa from 40 subjects. Bacterial sequences in the ALGD group showed an increase in Rhodobacterales, Thermales, Thermaceae, Rhodobacteraceae, and several genera, including Thermus, Paracoccus, Sphingobium, and Pseudomonas, compared to the NC group. Fungal sequences in the ALGD group showed an increase in Helotiales, Leotiomycetes, and Basidiomycota, while several orders, families, and genera, including Verrucariales, Russulales, and Trichosporonales, were decreased. The study found various interactions between intestinal bacteria and fungi. The bacterial functional analysis showed increased glycogen and vanillin degradation pathways in the ALGD group. Meanwhile, the fungal functional analysis showed a decrease in pathways related to the biosynthesis of gondoate and stearate, as well as degradation of glucose, starch, glycogen, sucrose, L-tryptophan, and pantothenate, and an increase in the octane oxidation pathway in the ALGD group. The mucosal microbiota in ALGD exhibits altered fungal and microbial composition compared to the NC mucosa, potentially contributing to the development of intestinal cancer by regulating specific metabolic pathways. Therefore, these changes in microbiota and metabolic pathways may be potential markers for diagnosing and treating colorectal adenoma and carcinoma.