Search Results (225)

Background: Uncontrolled diabetes is characterised by a loss of blood glucose control and increased oxidation of fatty acids to produce ATP. Use of metabolic inhibitors to blunt fatty acid oxidation and restore glucose metabolism is a poorly studied intervention for diabetes. Methods: Steptozotocin-induced diabetes was developed in Wistar male rats. A subset was supplemented with mildronate (100 mg/kg—14 days). Exploiting liquid chromatography-mass spectrometry for workflows including ion exchange-, C18-reverse phase- and HILIC-based chromatography methods, metabolite levels were quantified in plasma liver and brain tissue. Using both untargeted and targeted metabolomic analysis changes to the global tissue metabolome and individual metabolic pathways were estimated. Results: We document that an inhibitor of carnitine synthesis, mildronate, decreased plasma (50% p < 0.01) carnitine abundance and decreased plasma glucose concentration by one-third compared to streptozotocin (STZ)-treated rats (p < 0.001). Targeted metabolomic analysis of the liver showed decreased alpha-ketoglutarate abundance (35% p < 0.05) by STZ diabetes that was further decreased following mildronate treatment (50% p < 0.05). For both beta-hydroxybutyrate and succinate levels, STZ diabetes increased hepatic abundance by 50% (p < 0.05 for both), which was restored to control levels by mildronate (p < 0.05 for both). In contrast, brain TCA intermediate abundances were unaffected by either STZ diabetes or mildronate (NS for all). STZ diabetes also decreased abundance of pentose phosphate pathway (PPP) metabolites in the liver (glucose-6-phosphate, 6-phosphogluconolactone, 6-phosphogluconate 50% for all; p < 0.05), which was not restored by mildronate treatment. However, brain PPP metabolite abundance was unchanged by STZ diabetes or mildronate (NS for all). However, mildronate treatment did not affect the increased abundance of brain sorbitol, sorbitol-6-phosphate and glucose-6-phosphate as a result of STZ diabetes. Conclusions: Together, these observations highlight the potential role that metabolic inhibitors, like mildronate, may play in restoring blood glucose for diabetic patients, without a direct effect of tissues that represent obligate consumers of glucose (e.g., brain) whilst manipulating fat oxidation in tissues such as the liver. Full article

Parkinson’s disease (PD) is a progressive neurodegenerative disorder primarily characterized by the degeneration of dopaminergic neurons, leading to significant motor and non-motor symptoms. This study investigates glycosylation patterns with a significant emphasis on male Parkinson’s Disease (PD) patients, revealing unique alterations distinguishing PD from healthy states, utilizing high-performance liquid chromatography coupled with mass spectrometry (HILIC-LC-MS). Findings reveal significantly altered serum N-glycosylation profiles between male and female patients, with increased levels of high-mannose glycans and reduced mono-sialylated glycans in male patients. ROC curve analysis indicates that these glycan changes are the most important features for distinguishing PD from healthy states, with AUC values of 0.71 for M5 and 0.85 for M6. This study underscores the critical role of glycosylation in the pathophysiology of Parkinson’s disease and highlights its potential in early detection and monitoring of disease progression. Full article

Polar compounds can be separated on polar stationary phases attached on the surface of silica hydride (Type C silica). Although aqueous normal phase (ANP) chromatography has been used to denote this mode of separation, there have been no detailed studies on the retention mechanisms. We have applied the quantitative assessment methodology to investigate the retention mechanisms of polar compounds on the silica-hydride-based polar phases using a widely used hybrid silica-based amide phase for comparison. The study results indicate that the silica-hydride-based polar phases are not fundamentally different from the hybrid silica-based phase in terms of the adsorbed water layer and the retention mechanisms for polar compounds. Similar forces governing the retention in HILIC (i.e., partitioning, adsorption, and electrostatic interactions) are sufficient to describe the retention mechanisms of polar compounds on the silica-hydride-based polar phases. However, some small differences in selectivity are observed between the silica-hydride-based and hybrid silica-based phases. Full article

The gut microbiome evolves in response to host development, health state, lifestyle, nutrition, and microbial interactions. The survival of gut microbiota depends on its ability to utilize its host-indigestible complex oligosaccharides. Certain gut microbes produce glycosidases that cleave N-glycoproteins to release N-glycans that are then used as a carbon source. However, commercial glycosidases are inefficient and, thus, require improved deglycosylation strategies to study their functions and scale up their production. Therefore, the main objective of this study was to recombinantly produce and characterize the novel endo-β-N-acetylglucosaminidase 2 (EndoBI-2) from Bifidobacterium longum subsp. infantis (B. infantis) and to evaluate its enzymatic performance for controlled N-glycan release. Furthermore, the optimum reaction conditions for EndoBI-2 were investigated on model glycoprotein RNAse B using model glycoprotein. The released N-glycans were profiled by hydrophilic interaction liquid chromatography-fluorescence detection-quadrupole time-of-flight tandem mass spectrometry (HILIC-FLD-QTOF-MS/MS). We demonstrated that EndoBI-2 possesses a strong temperature tolerance and efficiently cleaves N-glycans under mild reaction conditions, exhibiting high activity at pH 5. These findings highlight EndoBI-2 as a robust and efficient biocatalyst for the production of bioactive N-glycans from diverse N-glycoproteins, with potential applications in glycobiotechnology. Full article

Methenamine, a urinary antiseptic with antimicrobial properties, decomposes into toxic formaldehyde under acidic conditions. Its use is prohibited in dairy cattle in Korea to prevent harmful residues in milk. This study was designed to develop and validate a sensitive and reliable LC–MS/MS method for determining methenamine in raw milk and bovine muscle in compliance with the Positive List System (PLS) regulations. Samples were extracted with acetonitrile (ACN)–methanol (MeOH) (7:3, v/v) containing ammonia water, followed by defatting with n-hexane and purification with primary secondary amine (PSA). Chromatographic separation was performed on a hydrophilic interaction liquid chromatography (HILIC) column, and quantification was conducted using matrix-matched calibration to minimize matrix effects. The method showed excellent linearity (R² > 0.999), low limits of quantification (LOQ) (0.49 μg/kg for raw milk; 0.64 μg/kg for bovine muscle), and acceptable recoveries (78.1–102.8%) with precision (CV ≤ 8.75%), meeting Codex CAC/GL 71-2009 criteria. Stability studies demonstrated that methenamine remained stable in stock solutions, working standards and processed extracts under the storage and handling conditions used. Application to incurred samples resulted in the detection of methenamine in 2 of 32 raw milk samples (0.65 and 1.14 μg/kg) but in none of the 25 bovine muscle samples, with all detected levels below the Korean PLS limit. These findings confirm that the developed method is accurate, sensitive, and applicable for routine surveillance of methenamine residues to ensure consumer safety. Full article

Many polar compounds of biochemical and pharmaceutical relevance exhibit low retention in reversed-phase liquid chromatography (RPLC), making their separation challenging. While hydrophilic interaction liquid chromatography (HILIC) columns are commonly used for such analyses, they require mobile phases with high organic solvent content. This work explores an alternative approach using RPLC with conventional C18 columns and mobile phases containing low percentages of acetonitrile, along with small amounts of the surfactant sodium dodecyl sulfate (SDS). This combination significantly enhances the retention of highly polar compounds. When the SDS concentration is sufficiently low, below the critical micellar concentration in water (8 mM), the retention increase follows a linear pattern. The retention behavior of polar compounds with different properties (nucleosides, methylxanthines, sulfonamides, and the diuretic hydrochlorothiazide) is examined using mobile phases in the submicellar region, with SDS concentrations ranging from 0 to 0.3 mM, acetonitrile contents between 10 and 20% (v/v), and temperatures varying from 25 to 55 °C. Changes in peak half-widths are also analyzed. Since SDS adsorbs onto the stationary phase, modifying its surface, the equilibration time has been investigated as a critical factor affecting retention reproducibility, influenced by the SDS concentration, acetonitrile content, and temperature. The results emphasize the need for complete equilibration to ensure reliable and consistent results. Full article

Hydrophilic interaction liquid chromatography (HILIC) is widely used for the analysis of glycans and oligosaccharides, yet the molecular basis of retention remains incompletely understood. In this study, we investigated dextran ladders labelled with 2-aminobenzamide (2-AB) and Rapifluor-MS™ (Waters, Milford, MA, USA) across a wide range of degrees of polymerization (DP 2–15), temperature conditions (10 °C to 70 °C), and gradient programs using a Acquity™ Premier Glycan BEH Amide column (Bridged Ethylene Hybrid, Waters, Milford, MA, USA). Van’t Hoff analysis revealed distinct enthalpic and entropic contributions to retention, allowing identification of a mechanistic transition from enthalpy-dominated docking interactions at low DP to entropy-driven dynamic adsorption at higher DP. This transition occurred reproducibly between DP 4–6, depending on the fluorescent label, while gradient steepness primarily influenced the location of the minimum enthalpy. Molecular dynamics simulations provided additional evidence, showing increased conformational flexibility and end-to-end distance variability for longer oligomers. This finding is consistent with entropy-dominated adsorption accompanied by displacement of structured interfacial water. Together, these results establish a molecular-level framework linking retention thermodynamics, conformational behavior, and solvation effects, thereby advancing our mechanistic understanding of glycan separation in HILIC. Full article

The detection of tetrodotoxins (TTXs) in European shellfish led the European Union to request a risk assessment from the European Food Safety Authority (EFSA). EFSA set a reference limit of 44 µg TTX equivalents kg⁻¹ and called for more data on TTX occurrence, especially in gastropods, which can accumulate in TTXs but remain poorly studied. Recently, preliminary monitoring has revealed the recurrent presence of TTXs in mussels in three areas along the North–Central Adriatic coast of Italy, while research on non-bivalve organisms has not yet been carried out. This study presents a preliminary survey, conducted from January 2023 to March 2025, on the presence of TTXs in gastropods, echinoderms, and arthropods collected from this area. A method in Hydrophilic Interaction Liquid Chromatography coupled with tandem Mass Spectrometry (HILIC-MS/MS) for detecting TTXs in bivalve mollusks was first tested through an international proficiency test, then optimized for the other invertebrates, the object of this study. TTX levels in all gastropods and arthropod samples were undetectable, while traces (~5 µg kg⁻¹) were found in one echinoderm sample (Paracentrotus lividus), marking the first reported occurrence of TTX in this species. Sea urchins are widely consumed in Italy; therefore, this finding is of particular importance from a public health perspective and deserves further investigation. Some gastropod genera or species sampled (e.g., Nassarius, Rapana venosa) have been identified as TTX carriers in other regions; therefore, the negative results obtained in this study may be related to seasonal or geographic variability. These results provide valuable data to EFSA’s call for monitoring emerging risks, particularly as climate change may increase TTX prevalence in European waters as well as worldwide. Full article

Background: Currently there are no clinically validated biomarkers recommended for prostate cancer (PCa) risk stratification other than prostate-specific antigen (PSA). Objective: This study aimed to identify urine metabolites that are associated with the presence of high-grade PCa at the time of radical prostatectomy. Methods: Urine samples were collected from patients who underwent radical prostatectomy. High-resolution metabolomics were implemented using liquid chromatography mass spectrometry (LC-MS). To enhance metabolic feature identification, sample extracts were analyzed in two modes, C18 chromatography [reverse-phase (RP)] and hydrophilic interaction chromatography (HILIC). Results: This analysis included a total of 22 patients with PCa (10 high-grade and 12 low-grade) and identified 52 differential metabolites, 40 in RP and 12 in HILIC, at the p-value 0.05 level. Among these, methyl alpha-aspartyl phenylalaninate was most significantly differentiated, while 3-methylbutanoicacid had the largest difference (slope −3.488). In the pathway analysis, the histidine metabolism pathway was significantly enriched (p < 0.05) with an enrichment factor of 3.5. Although not statistically significant, alterations were also observed in the vitamin B12, B7 (biotin), B6, and B3 (niacin) pathways. Conclusions: These findings suggest that urinary metabolites may have the potential to differentiate high-grade from low-grade PCa. Our study also highlights the metabolic reprogramming that occurs as PCa becomes more aggressive and potential differences in dietary patterns. Full article

Background/Objectives: The multi-attribute method (MAM) has found diverse use in the analytical characterization of therapeutic protein products during their development and production. As the MAM matures it has the potential to enter quality control (QC) laboratories, consolidating and replacing many less informative chromatographic techniques; however, this requires an appropriate risk assessment and understanding of method capability. Methods: A validated MAM approach was used to quantify product quality attributes (PQAs) using three different mass spectrometers across two laboratories; the results were compared to conventional hydrophilic interaction chromatography–fluorescence detection (HILIC-FLD) and cation exchange chromatography–ultraviolet (CEX-UV) techniques. Results: Stressed, long-term, and accelerated stability studies were performed, and their effects on glycosylation, deamidation, oxidation and N- and C-termini were quantified. Conclusions: Overall, the inter-instrument inter-laboratory data provided here showed important considerations for transferring methods between laboratories and establishing the correlation between the MAM and conventional data, elements which are necessary to transition the MAM to the QC environment and ultimately achieving the goal of replacing orthogonal QC methods. Full article

The reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) is a primary electron donor for both antioxidant enzymes, such as glutathione reductase, and pro-oxidant enzymes, such as NADPH oxidases that produce reactive oxygen species (ROS) and nitric oxide synthases that generate nitric oxide which act as signaling molecules. Monitoring NADPH levels, NADPH/NADP⁺ ratio, and especially distinguishing from NADH, provides vital information about cellular redox status, energy generation, survival, lineage specification, and death pathway selection. NADPH detection is key to understanding metabolic reprogramming in cancer, aging, and cardiovascular, hormonal, neurodegenerative, and autoimmune diseases. Liquid chromatography combined with mass spectrometry (LC-MS) is crucial for NADPH detection in redox signaling because it offers the high sensitivity, specificity, and comprehensive profiling needed to quantify this vital but labile redox cofactor in complex biological samples. Using hepatoma cell lines, liver tissues, and primary hepatocytes from mice lacking transaldolase or nicotinamide nucleotide transhydrogenase, or having lupus, this study demonstrates that accurate measurement of NADPH depends on its preservation in reduced form which can be optimally achieved by extraction of metabolites in alkaline solution, such as 0.1 M potassium hydroxide (KOH) in comparison to 80% methanol (MeOH) alone or 40:40:20 methanol/acetonitrile/formic acid solution. While KOH extraction coupled with hydrophilic interaction liquid chromatography (HILIC) and mass spectrometry most reliably detects NADPH, NADP, NADH, NAD, polyamines, and polyols, MeOH extraction is best suited for detection of glutathione and overall discrimination between complex metabolite extracts. This study therefore supports performing parallel KOH and MeOH extractions to enable comprehensive metabolomic analysis of redox signaling. Full article

Background/Objectives: This study comprehensively characterized the O- and N-glycosylation profiles of bispecific antibodies (BsAbs) via advanced analytical techniques to evaluate their structural and functional implications. Methods: High-resolution MS revealed O-xylosylation at Ser468 within the (G4S)4 linker peptide, which was identified as xylose with a molecular weight of 132.042 Da. HILIC-HPLC analysis of N-glycosylation revealed glycan species engineered to eliminate Fc effector functions. O-glycosylation analysis via β-elimination followed by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) identified xylose as the predominant glycan. Results: O-xylosylation does not affect the binding of BsAbs to either antigen Programmed Death-1 (PD-1) or Vascular Endothelial Growth Factor (VEGF). Notably, O-xylosylation interactions with mannose receptor represent the first discovery highlighting potential immunomodulatory roles. Conclusions: This study highlights the critical importance of monitoring comprehensive glycosylation characterization during the development of BsAb with (G4S)n linkers to ensure optimal therapeutic efficacy, safety, and reduced immunogenic potential. Full article

Nucleosides are of significant interest to biomedical and pharmaceutical research and have been successfully separated in hydrophilic interaction liquid chromatography (HILIC). However, there have been few studies focusing on the retention mechanisms, and detailed retention mechanisms are not clearly understood. The quantitative assessment methodology based on the linear relationship between the observed retention factors and the phase ratio has been shown to be a new tool to investigate the retention mechanisms of polar compounds in HILIC. This study evaluated the retention mechanisms of 16 nucleosides on a bare silica column. The retention contributions by partitioning, adsorption, and electrostatic attractions are quantitatively determined, and the main retention mechanism can be unambiguously identified for each nucleoside. The study results indicate that the main retention mechanism can shift with the salt concentration in the mobile phase, but partitioning seems to dominate at higher salt concentrations. In addition, the partitioning coefficients are measured using the quantitative assessment methodology and have a relatively strong correlation with the log P values of the nucleosides. Considering large errors in the log P values for these very polar compounds, the partitioning coefficients measured experimentally in the HILIC system may provide a more accurate measure for polarity assessment. Full article

Avocado is a unique fruit in which of seven-carbon (C7) sugars (notably D-mannoheptulose and perseitol) dominate the carbohydrate profile at harvest. Despite growing interest in sugar-mediated ripening processes, limited comparative data exist across cultivars. This work characterises the dynamic changes in non-structural carbohydrates in the mesotecarp of three commercially relevant avocado varieties—Bacon, Fuerte, and Hass—across four defined ripening stages, from unripe to overripe, with five biological replicates per stage. Using a validated hydrophilic interaction liquid chromatography–mass spectrometry (HILIC–MS) method, we quantified five key sugars and assessed their evolution through ripening. Concentrations varied among the studied samples within the following ranges: D-mannoheptulose, 0.4–49 mg/g dry weight (DW); perseitol, 0.5–23 mg/g DW; glucose, 0.8–5.3 mg/g DW; fructose, 0.6–4.5 mg/g DW; and sucrose, 0.5–3.4 mg/g DW. C7 sugar levels consistently declined, while C6 sugars increased—primarily between the intermediate and ready-to-eat stages—with distinct cultivar-specific patterns. Bacon maintained elevated C7 concentrations for a longer period; Fuerte exhibited a rapid transition from C7 to C6 sugars; and Hass displayed a more gradual and balanced shift. Multivariate analysis (partial least squares discriminant analysis, PLS-DA) effectively discriminated between cultivars at each ripening stage, confirming cultivar-specific metabolic signatures. These findings offer new insights into avocado carbohydrate metabolism, emphasising variety-dependent pathways that could inform breeding strategies, optimise postharvest ripening protocols, and support the nutritional characterisation of different avocado cultivars. Full article

Background/Objectives: Cow’s milk is a complex food, and research into its metabolome can provide information useful in the study of animal health, farming practices, food safety and the adulteration of milk. Comparative interlaboratory metabolic analysis is hampered by the lack of standardized methods—a requirement addressed in this study. Methods: We studied the influence of the chromatography column and extraction solvent on the metabolites isolated during untargeted metabolomics. Results: After studying fifteen columns and four extraction solvents, it was determined that an HILIC column offered the best compromise between retention time and separation of metabolites. Each extraction solvent covered a different area of the metabolome, only overlapping with previously annotated compounds. Extraction mixtures containing methanol tend to give better recovery. Conclusions: The choice of extraction solvent was crucial when looking at the difference between samples, but if interest lies only in previously annotated compounds, then there is little difference between the solvents. Full article