Chronic kidney disease (CKD) is a major global health burden, with renal fibrosis as the key pathological driver of disease progression. Fucoidan (FPS) is a sulfated polysaccharide from brown algae that has demonstrated renoprotective and anti-fibrotic properties. However, its metabolic and microbiota-related mechanisms remain unclear. Here, we evaluated the efficacy of FPS in a unilateral ureteral obstruction (UUO) mouse model, in which mice received oral FPS (100 or 200 mg kg-1 day-1) for 14 days. Kidney metabolomics and 16S rRNA sequencing of the gut microbiota were performed. As a result, UUO induced pronounced disturbances in tryptophan metabolism and marked gut microbial dysbiosis. FPS treatment attenuated renal fibrosis, normalized key tryptophan pathway intermediates and related metabolic enzymes in the kidneys, and partially restored the gut microbial composition. These results implicate the modulation of tryptophan metabolism and the gut microbiota in the anti-fibrotic effects of FPS, supporting its potential as a natural therapeutic candidate for renal fibrosis and CKD.

Cisplatin (DDP) is a widely used chemotherapeutic agent, but its clinical application is limited by dose-dependent nephrotoxicity. Although metabolic dysregulation is a hallmark of DDP-induced acute kidney injury (AKI), the specific changes in fatty acid oxidation (FAO)-associated metabolic programs and the enzymes linking metabolic disturbances to cell death remain incompletely defined. In this study, targeted metabolomic profiling of the kidney revealed a marked blockade of FAO, evidenced by the accumulation of fatty acids and a decrease in downstream acylcarnitines. Among FAO-related enzymes, acyl-CoA synthetase short-chain family member 2 (ACSS2) emerged as the most significantly downregulated enzyme, which was further confirmed in an ischemia/reperfusion AKI model. ACSS2 overexpression in HK-2 cells aggravated DDP-induced inflammation and apoptosis, whereas ACSS2 knockdown significantly reduced cytotoxicity and pro-inflammatory cytokine production. Furthermore, pharmacological inhibition of ACSS2 in vivo alleviated DDP-induced AKI characterized by reduced oxidative stress and improved renal function. Together, these findings indicate that targeting ACSS2 may represent a promising therapeutic strategy to mitigate DDP-induced renal injury.

Lactylation is a widespread protein modification with important regulatory roles in health and disease. Emerging evidence also links metabolite lactylation to disease onset, progression, and treatment response. It is estimated that an uncharacterized pool of lactoyl-metabolites exists in vivo, according to its formation mechanism. To mine this pool, we combined knowledge-driven prediction with stable isotopic labeling-based high-resolution mass spectrometry (SIL-HRMS). A predictive library of 151 lactoyl-metabolites was generated by expanding 20 basic amino acids (AAs) to their upstream and downstream metabolites. To improve detection, we developed a pair of new hydroxyl-reactive labeling reagents, 3,5-(dimethylamino)-2,4,6-triazine benzene-1-chlorine (Tmt-aycl-Cl) and its deuterium form d12-Tmt-aycl-Cl. Using HRMS, 95 lactoyl-metabolites were putatively identified across 14 tissue types, 64 structures of which are reported for the first time. Representative lactoyl-metabolites were chemically synthesized and characterized to verify some of the annotations. We then developed a pseudotargeted metabolomics workflow for semiquantitative profiling in a diabetic kidney disease (DKD) mouse model. DKD mice showed elevated lactate in serum and the kidney and widespread dysregulations of lactoyl-metabolites. Many lactoyl-metabolites correlated strongly with the urinary albumin-to-creatinine ratio, suggesting biomarker potential for DKD. This integrated strategy expands the catalog of lactoyl-metabolites and provides a platform for investigating their biological significance.

ETHNOPHARMACOLOGICAL RELEVANCE:Dachaihu Decoction (DCHD) is a traditional Chinese medicine formula from the Shanghan Lun. It has been used for over 1800 years to treat "Shaoyang and Yangming concurrent syndromes", which are closely related to modern liver disorders, including metabolic dysfunction-associated steatohepatitis (MASH). While DCHD has demonstrated hepatoprotective effects in preclinical studies, the specific bioactive components and mechanism of action against MASH remain elusive. AIM OF THE STUDY:To systematically identify the key active components of DCHD mediating its anti-MASH effects and to elucidate their molecular mechanisms. MATERIALS AND METHODS:The components in DCHD were characterized using high resolution-mass spectrometry (HRMS). The potential bioactive components were screened using network pharmacology. The therapeutic efficacy of candidate compounds was evaluated both in free fatty acid (FFA)-induced hepatocyte injury and activated hepatic stellate cells (HSCs) and in a high-fat diet/CCl4-induced MASH mouse model. The molecular mechanism was investigated via transcriptomic profiling, drug-target interaction validation, and gene knockdown assays. RESULTS:A total of 128 components were identified from DCHD using HRMS. Lonicerin (LON), a flavonoid glycoside predominantly derived from Citrus trifoliata L., was identified as the key active component. LON significantly ameliorated steatosis, inflammation and fibrosis both in vitro and in vivo. Mechanistically, LON bound to lymphocyte antigen 6 family member D (LY6D), which was significantly upregulated during MASH progression, and dose-dependently suppressed its expression. Importantly, LY6D knockdown abolished the protective effect of LON in AML12 hepatocytes and activated HSCs, confirming LY6D as a functional target. CONCLUSIONS:This study identified LON as a key bioactive component mediating the anti-MASH effects of DCHD and revealed that it alleviated MASH progression by targeting LY6D.

Cisplatin (DDP) is a widely used chemotherapeutic agent, but its clinical application is limited by dose-dependent nephrotoxicity. Although metabolic dysregulation is a hallmark of DDP-induced acute kidney injury (AKI), the specific changes in fatty acid oxidation (FAO)-associated metabolic programs and the enzymes linking metabolic disturbances to cell death remain incompletely defined. In this study, targeted metabolomic profiling of the kidney revealed a marked blockade of FAO, evidenced by the accumulation of fatty acids and a decrease in downstream acylcarnitines. Among FAO-related enzymes, acyl-CoA synthetase short-chain family member 2 (ACSS2) emerged as the most significantly downregulated enzyme, which was further confirmed in an ischemia/reperfusion AKI model. ACSS2 overexpression in HK-2 cells aggravated DDP-induced inflammation and apoptosis, whereas ACSS2 knockdown significantly reduced cytotoxicity and pro-inflammatory cytokine production. Furthermore, pharmacological inhibition of ACSS2 in vivo alleviated DDP-induced AKI characterized by reduced oxidative stress and improved renal function. Together, these findings indicate that targeting ACSS2 may represent a promising therapeutic strategy to mitigate DDP-induced renal injury.

Multidrug resistance (MDR) is a significant challenge in cancer treatment, with limited effective strategies available. Neuropilin-1 (NRP1) is emerging as a potential therapeutic target for overcoming drug resistance, but its role in MDR and the identification of potential inhibitors require further exploration. In this study, we investigated the role of NRP1 in MDR and identifies potential inhibitors targeting NRP1. Elevated NRP1 expression was observed in oxaliplatin (OXP)-resistant HCT116 (HCT116/L) and cisplatin (DDP)-resistant A549 cells (A549/DDP). Virtual screening and biological assays identified pitavastatin (Ptv) as a potent NRP1 inhibitor that restored chemosensitivity in resistant cells both in vitro and in vivo. Mechanistic studies revealed that Ptv directly binds to NRP1, promotes degradation of Zinc finger X-chromosomal protein (ZFX), and disrupts the NRP1-ZFX axis to reverse MDR. This study provides promising prospects for targeting the NRP1-ZFX axis as a therapeutic strategy for MDR and highlights the potential clinical application of Ptv in diseases involving NRP1.

Cisplatin (DDP) is widely utilized in the clinical treatment of malignant tumors, but its effectiveness is significantly compromised by the adverse effects of acute kidney injury (AKI). Renal tubular cells are primarily responsible for DDP-induced AKI (DDP-AKI); however, the responses of heterogeneous renal tubular cells to DDP exposure have not been thoroughly explored. In this study, we employed a targeted metabolomics approach to investigate the metabolic responses of renal tubular cells in DDP-AKI rats. Tubular cells were isolated from the renal cortex and outer medulla, and a chemical derivatization-based liquid chromatography-tandem mass spectrometry (LC-MS/MS) metabolomics method was applied. Our findings revealed distinct metabolic profiles in tubular cells from the renal cortex and outer medulla, with outer medullary cells exhibiting greater sensitivity to DDP exposure. Further analyses identified the tryptophan pathway as a critical factor contributing to these regional differences. Additional functional investigations showed that intermediate metabolites of the tryptophan pathway alleviated DDP cytotoxicity in both cortical and outer medullary tubular cells primarily through modulation of the Bcl2/Bax and Caspase-3 pathway. This study enhances our understanding of the metabolic characteristics of tubular cells across heterogeneous renal regions in DDP-AKI and facilitates further exploration of the underlying mechanisms of DDP-induced nephrotoxicity.

Astragali Radix (AR), a traditional Chinese medicine (TCM), has demonstrated therapeutic efficacy against various diseases, including cardiovascular conditions, over centuries of use. While doxorubicin serves as an effective chemotherapeutic agent against multiple cancers, its clinical application remains constrained by significant cardiotoxicity. Research has indicated that AR exhibits protective properties against doxorubicin-induced cardiomyopathy (DIC); however, the specific bioactive components and underlying mechanisms responsible for this therapeutic effect remain incompletely understood. This investigation seeks to identify the protective bioactive components in AR against DIC and elucidate their mechanisms of action. Through network medicine analysis, astragaloside IV (AsIV) and formononetin (FMT) were identified as potential cardioprotective agents from 129 AR components. In vitro experiments using H9c2 rat cardiomyocytes revealed that the AsIV-FMT combination (AFC) effectively reduced doxorubicin-induced cell death in a dose-dependent manner, with optimal efficacy at a 1∶2 ratio. In vivo, AFC enhanced survival rates and improved cardiac function in both acute and chronic DIC mouse models. Additionally, AFC demonstrated cardiac protection while maintaining doxorubicin's anti-cancer efficacy in a breast cancer mouse model. Lipidomic and metabolomics analyses revealed that AFC normalized doxorubicin-induced lipid profile alterations, particularly by reducing fatty acid accumulation. Gene knockdown studies and inhibitor experiments in H9c2 cells demonstrated that AsIV and FMT upregulated peroxisome proliferator activated receptor γ coactivator 1α (PGC-1α) and PPARα, respectively, two key proteins involved in fatty acid metabolism. This research establishes AFC as a promising therapeutic approach for DIC, highlighting the significance of multi-target therapies derived from natural herbals in contemporary medicine.

Ulcerative colitis (UC) is an idiopathic, chronic inflammatory disorder with an increasing incidence worldwide. Due to the complex and unclear therapeutic targets, unmet UC therapeutic drugs still exist. Recently, acylcarnitine metabolism disorder has been linked to intestinal inflammation, but its role in UC remains elusive. According to our preliminary non-targeted metabolomics data, acylcarnitines (ACs) was screened as the disturbed metabolites in the different intestinal inflammation-related diseases. Here we quantified 26 ACs within liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the dextran sulfate sodium (DSS)-induced UC rat model, and found that long-chain acylcarnitines (LCACs) were increased to varying degrees. As the key metabolites of fatty acid β-oxidation (FAO), the upstream metabolites long-chain fatty acids (LCFAs) and the related metabolic enzymes were further characterized, the results showed that the rate-limiting enzyme carnitine palmitoyltransferase 1A (CPT1A)-mediated LCFAs-LCACs metabolic axis was activated sharply. Next in vitro experiments exhibited that CPT1A was significantly upregulated in both inflammatory macrophages and colonic epithelial cells, and inhibition or knockdown of CPT1A could reduce the inflammation level remarkably. Thus, we screened the pharmacologic inhibitors of CPT1A from US Food and Drug Administration (FDA) approved drugs, within molecular docking, Western blot and cell membrane chromatography (CMC) technology, gliquidone was found to inhibit CPT1A in a dose-dependent manner and exert anti-inflammatory effects in vitro. Animal experiments also showed that gliquidone alleviated DSS-induced UC significantly. In summary, our study presents that within metabolomics analysis, inhibiting CPT1A is focused to be a potential therapeutic strategy against UC, and gliquidone represents an alternative treatment.

Environmental pollutants can induce multiorgan damage, with the digestive tract particularly susceptible. Diabetic enteropathy is a significant complication of type 2 diabetes mellitus (T2D). However, the relationship between environmental pollutant exposure and T2D-associated intestinal injury has not been previously explored. In this study, T2D mice were subjected to polystyrene microplastics (PS-MPs, 100 μg/day, 3 weeks) and bisphenol A (BPA, 100 μg/kg/day, 2 weeks). Metabolomics and 16S rRNA sequencing were used to detect changes in colonic metabolites and gut microbial composition. Caco-2 cells were utilized to investigate the functions of the altered metabolites. Compared to the T2D group, mice exposed to PS-MPs and BPA exhibited shorter colon length and reduced levels of gut barrier proteins ZO-1 and Occludin. Metabolomics analysis revealed that PS-MPs primarily affected colonic long-chain fatty acids (LCFAs) and adenosine metabolism, while BPA disrupted α-ketoisovaleric acid (KIVA) and pyruvic acid (PyrA) homeostasis. Moreover, PS-MPs exposure altered the abundance of Duncaniella and Olsenella, while BPA primarily affected Phocaeicola, Olsenella, and Variovorax. In vitro experiments showed that palmitoleic acid (C16:1), γ-linolenic acid (C18:3), adenosine (Ado), and KIVA promoted the expression of ZO-1 in Caco-2 cells. Our findings provide valuable insights into the impact of environmental pollutants on intestinal injury in T2D, underscoring the importance of environmental contaminant management, particularly in susceptible populations.

BACKGROUND:Tracking changes in plasma concentrations of monosaccharides and sugar alcohols related to glycometabolism, which plays a role as the main source of energy, is of great significance for the treatment of metabolic diseases. However, analysis of monosaccharides and sugar alcohols has always been a difficult task due to the high polarity of the polyhydroxy structure and the presence of a large number of isomers. So far, no suitable method has been developed for simultaneous determination of monosaccharides and sugar alcohols in beagle plasma. RESULTS:This work performed an innovative gas chromatography-mass spectrometry method for the simultaneous chromatographic separation and absolute quantification of 11 monosaccharides and sugar alcohols associated with glycometabolism. After derivatization, monosaccharides converted to be oxime acetylated derivatives and sugar alcohols transformed into acetylated derivatives. All analytes achieved good separation after chromatographic conditions were optimized, especially the selection of mid-polarity capillary column(6 % cyanopropyl phenyl and 94 % dimethyl polysiloxane). The improvement of derivatization efficiency through single factor and response surface optimization ensured a high sensitivity, with LOQ of each analyte in the range of 0.2-50 ng/mL. The established method was fully validated in terms of linearity and range, sensitivity, accuracy and precision, recovery, matrix effect, stability, dilution integrity and proved to be reliable, which was applied to the comparative study on hypoglycemic effect of two antidiabetic agents with different pharmacological mechanisms, dorzagliatin and metformin, as well as possible metabolic pathways affected by them. SIGNIFICANCE:This method solves the problems of multiple peaks after derivatization and frequent co-elution of analytes in previous analytical methods, significantly enhances derivatization efficiency of ketoses, which provides a promising approach for simultaneous analysis of aldose, ketose, and sugar alcohol. It offers new insights into a more comprehensive research on glycometabolism rather than merely focusing on glucose.

BACKGROUND:Ulcerative colitis (UC) has demonstrated an escalating global incidence and prevalence, thereby posing substantial challenges to public health. Despite recent advancements in therapeutic interventions, the clinical management of UC remains suboptimal, underscoring the urgent need for novel treatment strategies. Saikosaponin A (SSa), a bioactive compound derived from the traditional Chinese herb Radix Bupleuri (RB), exhibits potent anti-inflammatory and immunomodulatory effects. However, its effects on UC and the underlying molecular mechanisms remain to be thoroughly explored. PURPOSE:This study aims to elucidate the underlying mechanisms of SSa in ameliorating UC and establish a pharmacological foundation for developing novel treatment modalities to address unmet clinical needs in UC treatment. METHODS:The protective effects of SSa against DSS-induced acute colitis were evaluated in a 3 % DSS-treated mouse model. Histological (H&E staining) and molecular analyses (RT-qPCR, ELISA, Western blotting, and flow cytometry) were performed to assess colonic tissue damage and inflammatory responses. Macrophage depletion via tail vein injection of clodronate liposomes confirmed the pivotal role of macrophages in UC pathogenesis and SSa's anti-inflammatory effects. The inhibitory effects of SSa on NLRP3 inflammasome activation were analyzed in vivo and in LPS/ATP-stimulated bone marrow-derived macrophages (BMDMs) using RT-qPCR, ELISA, and Western blotting. Bioinformatics analysis, targeted LC-MS/MS, and molecular docking were employed to identify potential molecular targets and mechanisms of SSa. Drug affinity responsive target stability (DARTS), cellular thermal shift assay (CETSA), and CH25H siRNA knockdown assays were used to validate CH25H as the direct target of SSa. RESULTS:SSa effectively attenuated DSS-induced colitis in mice by alleviating colonic inflammation, preserving intestinal barrier integrity, reducing LPS translocation, and mitigating systemic organ injury in the liver and spleen. The inflammatory response of macrophages and the production of IL-1β were identified as key pathogenic components in colitis, and the clearance of macrophages significantly ameliorated colitis progression while SSa administration post-macrophage clearance did not further alter the disease phenotype. Mechanistically, SSa inhibited the NLRP3 inflammasome activation-mediated IL-1β secretion in macrophages. The sterol metabolism played a crucial role in the activation of the NLRP3 inflammasome. SSa also restored the disturbed sterol homeostasis in the colon under inflammatory conditions, especially promoted the synthesis of 25-hydroxycholesterol (25-OHC). Further investigation revealed that SSa primarily exerts its therapeutic effects by directly targeting cholesterol 25-hydroxylase (CH25H), which promotes the production of 25-OHC and inhibits macrophage NLRP3 inflammasome activation. CONCLUSION:This pioneering study demonstrated the therapeutic effect of SSa on DSS-induced colitis by targeting CH25H to enhance 25-OHC biosynthesis, which subsequently inhibited NLRP3 inflammasome activation in IL-1β-producing macrophages. These findings reveal a novel mechanism of SSa in UC treatment through cholesterol metabolism-regulated cascade immune modulation, providing strong pharmacological support for its development as a potential UC therapy.

Background and aims: Insulin resistance is a key driver of metabolic disorders, yet its molecular mechanisms remain elusive. This study identifies 27-hydroxycholesterol (27HC), a cholesterol-derived metabolite, and investigates its role in insulin resistance. Methods: Targeted metabolomics quantified absolute and relative levels of 27HC (27HC/cholesterol ratio) in patients, mice, and hepatocytes. Insulin resistant mouse models were established to characterize spatiotemporal dynamics of 27HC and related enzymes. Functional analyses assessed 27HC's effect on insulin signaling across multiple hepatocyte types. Transcriptomic analysis identified key effector pathways. Plasma membrane cholesterol accessibility was evaluated using biosensors and validated by cholesterol rescue. Membrane protein extraction, immunofluorescence, and flow cytometry were employed to assess the impact of 27HC on insulin receptor (IR) distribution and binding capacity. Results: Elevated 27HC levels were observed in patients with metabolic dysfunction-associated steatotic liver disease (MASLD), obese and type 2 diabetic mice (T2DM), and PA-treated HepG2 and primary hepatocytes, correlating with impaired insulin sensitivity. CYP27A1 was identified as the key enzyme regulating liver 27HC levels. In vitro studies demonstrated that 27HC disrupts insulin signaling in HepG2, AML12, and primary hepatocytes, whereas CYP27A1 knockdown restored IR responsiveness. 27HC suppresses SREBP2-dependent cholesterol biosynthesis, depleting accessible cholesterol in the plasma membrane, triggering IR mislocalization and signal attenuation. Liver-specific CYP27A1 silencing in mice fed a high-fat diet improved systemic insulin sensitivity and restored metabolic homeostasis. Conclusion: Our findings establish 27HC as a key effector linking cholesterol metabolism to insulin resistance and propose CYP27A1 inhibition as a potential therapeutic strategy for insulin resistance.

Lung adenocarcinoma (LUAD), the predominant subtype of non-small cell lung cancer (NSCLC), poses significant therapeutic challenges due to its aggressive nature and limited treatment options. Cisplatin is a commonly used chemotherapeutic agent for advanced LUAD, often encounters PDR, leading to rapid disease progression and tumor recurrence. In this study, we demonstrate that LDHA expression is elevated in cisplatin-resistant LUAD cell lines and correlates with poor patient prognosis. Notably, inhibiting the expression of LDHA significantly enhances cisplatin sensitivity. Mechanistically, LDHA functions through non-metabolic enzymatic activity to promote the ubiquitination and degradation of AMBRA1 by facilitating its interaction with RNF2, thereby activating Cyclin D1 and BCL2, which drives cisplatin resistance. Importantly, we identified two LDHA inhibitors, triflupromazine (TRI) and tranylcypromine (TRA), that significantly improve cisplatin efficacy both in vitro and in vivo. These findings highlight a critical role of LDHA in promoting cisplatin resistance, and suggest that targeting LDHA may represent a promising therapeutic strategy for patients with advanced LUAD.

Phosphatidyl amino acids (p-AAs) are metabolites characterized by the phosphorylation of the hydroxyl, amino, carboxyl, and thiol groups of amino acids. Previous research has primarily focused on the phosphorylation sites within macromolecular proteins, with a particular emphasis on typical O-p-AAs. In this study, we established a prediction library of p-AAs based on existing knowledge. To improve detection rates of p-AAs in biological samples, we employed a chemical labeling-based LC-MS/MS method, utilizing p-[3,5-(dimethylamino)-2,4,6-triazine] benzene-1-sulfonyl piperazine (Tmt-PP) and its deuterated form (d12-Tmt-PP) as paired labeling reagents. A preliminary identification was performed by matching characteristic MS fragments with available standards. Additionally, strategies such as in vitro methods were implemented for further identification. The phosphatase treatment aids in identifying phosphate-modified metabolites by dephosphorylating them, while cell extract incubation helps determine if novel phosphorylated amino acids are generated in vivo. Ultimately, we identified 11 p-AAs, 6 of which are novel metabolites reported for the first time. A pseudotargeted metabolomics method covering 11 identified p-AAs was established and applied to investigate the differences between cisplatin-resistant non-small cell lung cancer (NSCLC) cells and their parental cells, as well as their derived exosomes. This approach enhances our understanding of the role of p-AAs in various health and disease conditions and contributes to the discovery of additional novel phosphatidyl metabolites.

Patients with ulcerative colitis (UC) have a higher risk of developing colorectal cancer (CRC), however, the metabolic shifts during the UC-to-CRC transition remain elusive. In this study, an AOM-DSS-induced three-stage colitis-associated colorectal cancer (CAC) model is constructed and targeted metabolomics analysis and pathway enrichment are performed, uncovering the metabolic changes in this transition. Spatial metabolic trajectories in the "normal-to-normal adjacent tissue (NAT)-to-tumor" transition, and temporal metabolic trajectories in the "colitis-to-dysplasia-to-carcinoma" transition are identified through K-means clustering of 74 spatially and 77 temporally differential metabolites, respectively. The findings reveal two distinct metabolic profile categories during the inflammation-to-cancer progression: those with consistent changes, either increasing (e.g., kynurenic acid, xanthurenic acid) or decreasing (e.g., long-chain fatty acids, LCFAs), and those enriched at specific disease stages (e.g., serotonin). Further analysis of metabolites with consistent temporal trends identifies eicosapentaenoic acid (EPA) as a key metabolite, potentially exerting anti-inflammatory and anti-cancer effects by inhibiting insulin-like growth factor binding protein 5 (IGFBP5). This study reveals novel metabolic mechanisms underlying the transition from UC to CAC and suggests potential targets to delay the progression.

Advanced glycation end products (AGEs), formed through reactions between carbonyl compounds and amino groups, mostly originate from lysine and arginine, with other amino-acid-derived AGEs remaining largely uncharacterized. Here, we developed a comprehensive strategy to annotate novel AGEs. First, a prediction library of 216 AGEs was constructed based on reported formation pathways. Available standards were labeled by dansyl chloride to obtain characteristic fragments via liquid chromatography-tandem mass spectrometry (LC-MS/MS). Using Maillard reaction models of heated amino acid and carbonyl mixtures, combined with LC-MS/MS and high-resolution MS, we identified 20 AGEs, including 7 new structures. A pseudotargeted method covering these AGEs was developed and applied to study their dynamic changes in herbs subjected to varying steam-bask cycles and to investigate differences between free and protein-bound AGEs in high-temperature processed foods. This strategy advances the discovery and understanding of diverse AGEs in food and herbal matrices.

Free fatty acids (FFAs) play a key role in living organisms and participate in metabolic processes, mainly as a source of energy for cells. The CC position isomer of FFAs is strongly associated with many diseases, but quantification of its double bond position isomer remains a challenge in lipid analysis. In this study, based on the requirements of the pseudotargeted metabolomics, an analytical method based on a two-step derivatization LC-MS/MS method and a multiple reaction monitoring (MRM) mode was established and fully validated in terms of linearity, precision, and stability. The results demonstrated that the method relatively quantified 30 FFAs in plasma samples. These included 8 saturated fatty acids (SFAs), 12 monounsaturated fatty acids (MUFAs), and 10 polyunsaturated fatty acids (PUFAs). The developed method was applied to analyze the increase or down-regulation of the relative content of FFAs before and after the administration of the drug in beagles which may help to explain the therapeutic effect of sacubitril valsartan. The establishment of this method allows the study of FFAs in beagles plasma to be no longer limited to analysis at the subclass level but can be focused at the isomer level.

In our previous study, a chemical derivatization reagent named 5-(dimethylamino) naphthalene-1-sulfonyl piperazine (Dns-PP) was developed to enhance the chromatographic retention and the mass spectrometric response of free fatty acids (FFAs) in reversed-phase liquid chromatography coupled with electrospray ionization-mass spectrometry (RPLC-ESI-MS). However, Dns-PP exhibited strong preferences for long-chain FFAs, with limited improvement for short- or medium-chain FFAs. In this study, a new series of labeling reagents targeting FFAs were designed, synthesized, and evaluated. Among these reagents, Tmt-PP (N2, N2, N4, N4-tetramethyl-6-(4-(piperazin-1-ylsulfonyl) phenyl)-1,3,5-triazine-2,4-diamine) exhibited the best MS response and was selected for further evaluations. We compared Tmt-PP with Dns-PP and four commonly used carboxyl labeling reagents from existing studies, demonstrating the advantages of Tmt-PP. Further comparisons between Tmt-PP and Dns-PP in measuring FFAs from biological samples revealed that Tmt-PP labeling enhanced the MS response for about 80% (30/38) of the measured FFAs, particularly for short- and medium-chain FFAs. Moreover, Tmt-PP labeling significantly improved the chromatographic retention of short-chain FFAs. To ensure accurate quantification, we developed a stable isotope-labeled Tmt-PP (i.e., d12-Tmt-PP) to react with chemical standards and serve as one-to-one internal standards (IS). The method was validated for accuracy, precision, sensitivity, linearity, stability, extraction efficiency, as well as matrix effect. Overall, this study introduced a new chemical derivatization reagent Tmt-PP (d12-Tmt-PP), providing a sensitive and accurate option for quantifying FFAs in biological samples.