Search Results (351)

Vehicle indoor air quality (VIAQ) remains poorly standardized despite its growing health relevance. This study developed and applied a real-road test protocol to quantify in-cabin exposure to particulate and gaseous pollutants under different heating, ventilation, and air-conditioning (HVAC) modes: outside air (OA), recirculation (RC), and automatic (Auto). Concentrations of PM_2.5, particle number (PN), NO, and NO₂ were simultaneously measured inside and outside passenger vehicles using validated instruments. In-cabin PM_2.5 levels were lowest in RC, intermediate in Auto, and highest in OA, showing strong HVAC dependence. Particle number distributions were dominated by submicron particles (<1.0 μm). Under RC, NO gradually increased while NO₂ decreased, likely due to NO–NO₂ interconversion and activated-carbon filtration. Short-duration, reproducible on-road tests were conducted under standardized vehicle, occupant, and HVAC settings to minimize variability. Although external conditions could not be fully controlled, consistent routes and configurations ensured comparability. The findings highlight HVAC operation as the dominant factor governing short-term VIAQ and provide practical insight toward harmonized test procedures and design improvements for cabin air management. Full article

Type 2 diabetes is a major global health burden, causing approximately 2 million deaths annually. Recent studies have revealed a strong positive correlation between elevated triglyceride levels and plasma glucose, as well as increased prevalence, incidence, and mortality of type 2 diabetes, suggesting a potential causal link. This review explores the metabolic interconversion between triglycerides and glucose, emphasizing how excess carbohydrate intake leads to ectopic triglyceride accumulation, which in turn enhances hepatic gluconeogenesis. It highlights key signaling pathways through which ectopic triglyceride deposition drives insulin resistance, hyperinsulinemia, β-cell dysfunction and apoptosis, and increased glucose production—central mechanisms in diabetes pathogenesis. Evidence from clinical interventions, such as the reversal of type 2 diabetes through bariatric surgery and dietary energy restriction, supports the hypothesis that ectopic triglyceride accumulation is a driving factor. Furthermore, this review explains why omega-3 fatty acids and niacin, in contrast to fibrates, do not protect against type 2 diabetes, despite lowering triglycerides. Overall, this review emphasizes the contribution of ectopic triglyceride accumulation—driven by obesity, hypertriglyceridemia, excessive consumption of carbohydrates and fats, and physical inactivity—to the onset and progression of type 2 diabetes, offering valuable insights into potential therapeutic strategies. Full article

Aroma volatiles constitute the primary molecular basis of fruit flavor quality, governing sensory attributes and marketability. Based on their chemical states, aroma compounds are categorized into bound and free forms. Bound aroma compounds predominantly exist as non-volatile glycosides, which can be hydrolyzed enzymatically or through acid treatment to release volatile free aroma compounds, thereby enhancing fruit fragrance. Although the dynamic interconversion between free and bound aroma compounds is pivotal for fruit flavor development, the governing mechanisms, including the principal controlling factors, regulatory networks, and external influences, are still under investigation. This review primarily synthesizes recent advances regarding the structural diversity, analysis, biosynthesis, and regulation of bound aroma compounds. Additionally, it examines how key regulatory networks and environmental factors modulate the synthesis and transformation of these compounds. The integrated overview provides new insights for future regulation of aroma metabolism in fruits. Full article

Copper is a vital micronutrient for animals and plants acting as a crucial cofactor in the synthesis of numerous metabolic enzymes and contributing to mitochondrial respiration, metabolism, oxido-reductive reactions, signal transmission, and oxidative and nitrosative damage. In the cells, copper may exist in the Cu⁺ and Cu⁺⁺ oxidation states and the interconversion between these two states may occur via various redox reactions regulating cellular respiration, energy metabolism, and cell growth. The human body maintains a low level of copper, and copper deficiency or copper excess may adversely affect cellular functions; therefore, regulation of copper levels within a narrow range is important for maintaining metabolic homeostasis. Recent studies identified a new copper-dependent form of cell death called cuproptosis. Cuproptosis occurs due to copper binding to lipoylated enzymes (for instance, pyruvate dehydrogenase and α-ketoglutarate dehydrogenase) in the tricarboxylic acid Krebs cycle. In recent years, extensive studies on copper homeostasis and copper-induced cell death in degenerative disorders, like Menkes, Wilson, Alzheimer, Parkinson’s, Huntington’s diseases, and Amyotrophic Lateral Sclerosis, have discussed the therapeutic potential of targeting cuproptosis. Copper contamination in the environment, which has increased in recent years due to the expansion of agricultural and industrial activities, is associated with a wide range of human health risks. Soil used for the cultivation of grapes has a long history of copper-based fungicide application (the Bordeaux mixture is rich in copper) resulting in copper accumulation at levels capable of causing toxicity in plants that co-inhabit the vineyards. Phytoremediation, which uses plants and biological solutions to remove toxic heavy metals and pesticides and other contaminants from soil and water, is an environmentally friendly and cost-effective technology used for the removal of copper. It requires plants to be tolerant of high levels of copper and capable of accumulating metal copper in plants’ aerial organs and roots. This review aims at highlighting the importance of copper as an essential metal, as well as its involvement in cuproptosis and neurodegenerative diseases. Full article

Cancer cell plasticity, defined as the ability of tumor cells to reversibly adopt distinct functional states, plays a central role in tumor heterogeneity, therapy resistance, and disease relapse. This process enables cells to enter stem-like, dormant, or drug-tolerant persister states in response to treatment or environmental stress without undergoing genetic changes. Such reversible transitions complicate and limit current treatments. Conventional cancer models often fail to capture the complexities of these adaptive states. In contrast, patient-derived tumor organoids (PDOs), which retain the cellular diversity and structure of primary tumors, provide a unique system for investigating plasticity. This review describes how PDOs can model cellular plasticity, such as the emergence of drug-tolerant persister cells and the interconversion between cancer stem cell states across multiple tumor types. We particularly focused on colorectal cancer organoids, for which research on the mechanism of plasticity is the most advanced. Combined with single-cell analysis, lineage tracing, and functional assays, PDOs can help identify the molecular pathways that control plasticity. Understanding these mechanisms is important for developing therapies to prevent treatment failure and control disease progression. Full article

This study explores the thermochemical properties and formation mechanisms of reactive oxygen species (ROS) relevant to photocatalytic processes, aiming to clarify their molecular characteristics and reaction dynamics. The research focuses on key ROS, including the superoxide anion radical (^•O₂⁻), hydrogen peroxide (H₂O₂), singlet oxygen (¹O₂), and hydroxyl radical (^•OH), employing Møller–Plesset second-order perturbation theory (MP2)-level quantum chemical calculations. Solvent effects were modeled using water to simulate conditions commonly found in photocatalytic environments. The computed energetic profiles and stabilities of the ROS offer insights into their relative reactivities and possible interconversion pathways. These findings enhance the understanding of how ROS behave under photocatalytic conditions, with implications for their role in degradation mechanisms and redox cycles. Overall, the results support the development and optimization of photocatalytic technologies for environmental applications, including pollutant degradation and disinfection of water and air. Full article

Structure and nonlinear spectra of the basal surface of ice Ih were investigated by molecular dynamics simulations. At a temperature significantly lower than the melting temperature $T_m$, the ice structure at the interface is only weakly perturbed by the presence of surface. The computed nonlinear spectrum of the interface well agrees with the experimental data and the results of the calculations provide the molecular-level interpretation of spectral features. In particular, the ice surface specific positive peaks in the Im[${\chi }^{\left(2\right)}$] spectrum at ∼3180 cm⁻¹ and at ∼3420 cm⁻¹ were found to result from the low- and high-frequency vibrational modes of quadruply H-bonded surface molecules, respectively. The spectrum of the crystalline ice interface is significantly affected by intermolecular interactions. Upon increasing the temperature, the structural disorder extends to the second water bilayer. The thickness of the premelted water layer of 6–8 Å can be estimated at the temperature by ca. 5 K below $T_m$. The increase in the temperature results in a change in the intensity and shape of the nonlinear spectrum of the ice Ih interface. The changes can be explained by the interconversion between different H-bonded surface species and by an increase in disordering of water molecules that reduces strength of intermolecular interactions. Results of the present work contribute to our understanding of the structure–spectrum relationship of the ice/air interface, and shed light on the origins of features in the nonlinear spectra of the system. Full article

Allopregnanolone (allo) and isoallopregnanolone (isoallo) are neuroactive steroid epimers that differ in hydroxyl orientation at carbon three. Allo is a potent GABA-A receptor agonist, while isoallo acts as an antagonist, influencing brain function through their interconversion. Their metabolism varies across brain regions due to enzyme distribution, with AKR1C1–AKR1C3 active in the brain and AKR1C4 restricted to the liver. In rats, AKR1C9 (liver) and AKR1C14 (intestine) perform similar roles. Beyond AKR1Cs, HSD17Bs regulate steroid balance, with HSD17B6 active in the liver, thyroid, and lung, while HSD17B10, a mitochondrial enzyme, influences metabolism in high-energy tissues. Our current data obtained using the GC-MS/MS platform show that allo and isoallo in rats undergo significant metabolic conversion, suggesting a regulatory role in neurosteroid action. High allo levels following isoallo injection indicate brain interconversion, while isoallo clears more slowly from blood and undergoes extensive conjugation. Metabolite patterns differ between brain and plasma—allo injection leads to 5α-DHP and isoallo production, whereas isoallo treatment primarily yields allo. Human plasma contains mostly sulfate/glucuronided steroids (2.4–6% non-sulfate/glucuronided), whereas male rats exhibit much higher free steroid levels (29–56%), likely due to the absence of zona reticularis. These findings highlight tissue-specific enzymatic differences, which may impact neurosteroid regulation and CNS disorders. Full article

Poplar (Populus spp.) is a keystone commercial tree species in Northeast China, valued for its high economic returns. The genotype-by-environment (G × E) interaction critically governs its growth performance and ecological adaptability, which are pivotal for ensuring the long-term sustainability and economic viability of poplar plantations. In this study, the fibrous roots of the (P. simonii × P. nigra) × P. deltoides clone planted at three distinct sites, including Lishu (named SR1), Xinmin (named SR2), and Cuohai (named SR3), were used to perform transcriptome and metabolome. Comparative analysis revealed 6246, 3455, and 3854 differentially expressed genes (DEGs) in the SR1 vs. SR2, SR1 vs. SR3, and SR2 vs. SR3 comparisons, respectively. These DEGs were functionally enriched in pathways associated with antioxidant enzyme activity, stimulus response, plant hormone signal transduction pathways, and α-linolenic acid metabolism. Metabolomic analysis identified 106, 147, and 189 significantly differentially accumulated metabolites (DAMs) across the same comparisons, primarily linked to glutathione metabolism, butanoate metabolism, and pentose–glucuronate interconversions. Notably, we identified a core regulatory module comprising 57 genes and four key metabolites within the α-linolenic acid metabolic pathway, which exhibited strong correlations with phenotypic adaptability. These findings provide mechanistic insights into poplar’s plasticity under environmental heterogeneity, offering a molecular roadmap for future breeding strategies and the sustainable expansion of poplar cultivation. Full article

Background: Lespedeza davurica is an important perennial leguminous shrub endemic to China’s Loess Plateau, and it plays a crucial role in ecosystem restoration and soil erosion control. However, phosphorus deficiency and environmental stresses limit its growth potential and ecological function. Methods: In the present study, the interaction between Acinetobacter calcoaceticus DP25, a phosphate-solubilizing rhizobacterium isolated from L. davurica rhizosphere, and L. davurica was investigated. We performed biochemical analyses of leaves from L. davurica planted in saline–alkali soil to monitor antioxidant defense systems and stress-related metabolites, and conducted a combination of transcriptomics and metabolomics approaches to elucidate the bacteria-mediated enhancement of growth and stress tolerance in L. davurica. Results: DP25 inoculation substantially enhanced L. davurica growth performance, increasing plant height by 47.68%, biomass production by 102.54–132.42%, and root architecture parameters by 62.68–78.79% (p < 0.0001). Catalase activity, a key antioxidant enzyme, showed a marked increase of 41.53% (p < 0.001), while malondialdehyde and free proline contents decreased by 18.13% and 19.33%, respectively (p < 0.05). Transcriptomic analysis revealed 263 differentially expressed genes, with enrichment in carotenoid biosynthesis, ABC transporters, and pentose and glucuronate interconversion pathways. Metabolomic profiling identified 246 differentially accumulated metabolites, highlighting enhanced secondary metabolite production and stress response mechanisms. Integration of multi-omics data revealed 19 co-regulated pathways involved in growth promotion and stress tolerance. Conclusions: A. calcoaceticus DP25 enhances L. davurica growth through coordinated regulation of metabolic pathways involved in photosynthesis, antioxidant defense, and secondary metabolite biosynthesis. These findings provide molecular insights into beneficial plant–microbe interactions and support the development of sustainable strategies for ecosystem restoration in degraded environments. Full article

Soluble sugars are among the key components determining the flavor quality of rapeseed bolting. However, the potential regulatory network governing the biosynthesis of soluble sugars during the growth and development of rapeseed bolting remains largely unknown. In this study, the total soluble sugar and starch contents were measured at the seedling and bolting stages in 203 Brassica napus germplasms. Among them, the inbred lines No51 and No106 were identified as high- and low-sugar materials, respectively. A comparative analysis of the soluble sugar composition between these two extreme lines revealed that sucrose and glucose are the key metabolites contributing to differences in the soluble sugar content. A total of 36,893 differentially expressed genes (DEGs) were identified by transcriptomics, including 19,031 significantly upregulated genes and 17,862 downregulated genes. Metabolomics has identified 25 common and unique metabolites. The combined analysis of transcriptomics and metabolomics showed that differentially expressed genes and metabolites were mainly concentrated in starch and sucrose metabolism, galactose metabolism, and the interconversion of pentose and glucuronic acid. The expression patterns obtained by RNA seq and qRT PCR are highly consistent. A regulatory network related to soluble sugar synthesis and metabolism was constructed, leading to the identification of BnaC02G0100500ZS, BnaC02G0100700ZS, and BnaC02G0092700ZS as potential key genes involved in the regulation of soluble sugar biosynthesis. Full article

The nitrogen cycle (N-cycle) is a cornerstone of global biogeochemistry, regulating nitrogen availability and affecting atmospheric chemistry, agricultural productivity, and ecological balance. Central to this cycle is the reversible interplay between nitrate (NO₃⁻) and nitrite (NO₂⁻), mediated by molybdenum-dependent enzymes—Nitrate reductases (NARs) and Nitrite oxidoreductases (NXRs). Despite catalyzing opposite reactions, these enzymes exhibit remarkable structural and mechanistic similarities. This review aims to elucidate the molecular underpinnings of nitrate reduction and nitrite oxidation by dissecting their enzymatic architectures, redox mechanisms, and evolutionary relationships. By focusing on recent structural, spectroscopic, and thermodynamic data, we explore how these two enzyme families represent “two sides of the same coin” in microbial nitrogen metabolism. Special emphasis is placed on the role of oxygen atom transfer (OAT) as a unifying mechanistic principle, the influence of environmental redox conditions, and the emerging evidence of bidirectional catalytic potential. Understanding this dynamic enzymatic interconversion provides insight into the flexibility and resilience of nitrogen-transforming pathways, with implications for environmental management, biotechnology, and synthetic biology. Full article

Lactate dehydrogenase (LDH) catalyzes the reversible interconversion of pyruvate and lactate, coupled with the redox cycling of NADH and NAD⁺. While LDHA has been extensively studied as a therapeutic target, particularly in cancer, due to its role in the Warburg effect, LDHB remains underexplored, despite its involvement in the metabolic reprogramming of specific cancer types, including breast and lung cancers. Most known LDH inhibitors are designed against the LDHA isoform and act competitively at the active site. In contrast, LDHB exhibits distinct kinetic properties, substrate preferences, and structural features, warranting isoform-specific screening strategies. In this study, 115 natural compounds previously reported as LDHA inhibitors were systematically evaluated for LDHB inhibition using an integrated in silico and in vitro approach. Virtual screening identified 16 lead phytochemicals, among which luteolin and quercetin exhibited uncompetitive inhibition of LDHB, as demonstrated by enzyme kinetic assays. These findings were strongly supported by molecular docking analyses, which revealed that both compounds bind at an allosteric site located at the dimer interface, closely resembling the binding mode of the established LDHB uncompetitive inhibitor AXKO-0046. In contrast, comparative docking against LDHA confirmed their active-site binding and competitive inhibition, underscoring their isoform-specific behavior. Our findings highlight the necessity of assay conditions tailored to LDHB’s physiological role and demonstrate the application of a previously validated colorimetric assay for high-throughput screening. This work lays the foundation for the rational design of selective LDHB inhibitors from natural product libraries. Full article

Pear buds exhibit inherent dormancy, during which carbohydrates play a pivotal role in dormancy release and germination. In this study, Pyrus pyrifolia ‘Cuiguan’ was employed as the experimental material to investigate the molecular mechanisms underlying flower bud dormancy release. The results revealed that the dynamic balance between starch and soluble sugar is critical for promoting dormancy release and germination in P. pyrifolia ‘Cuiguan’ flower buds. Through transcriptomic and proteomic profiling, a total of 4035 differentially expressed genes (DEGs) and 1596 differentially expressed proteins (DEPs) were identified, which were predominantly associated with carbohydrate metabolism, particularly sugar metabolism pathways. Their changes were coordinately regulated at both transcriptional and translational levels. Key structural genes involved in maltose and sucrose biosynthesis, including BAM (LOC103949270), AAM (LOC125479337, LOC103940334, and LOC103941903), SPS (LOC125475683), and INV (LOC125478747), were significantly upregulated during the germination stage, facilitating flower bud sprouting. Integrated multi-omic analysis demonstrated that starch–sugar interconversion may govern dormancy release and sustained bud growth by modulating sugar metabolism-related genes and proteins. These findings provide novel insights into the molecular mechanisms of carbohydrate biosynthesis and associated protein regulation during dormancy release and development of P. pyrifolia ‘Cuiguan’ under natural conditions. Full article

Salmonella colonization in the gastrointestinal tract of turkeys presents a risk to the safety of products derived from them. Lactobacillus-based probiotics and a plant-derived compound, trans-cinnamaldehyde, have previously been found to be effective in reducing multidrug-resistant Salmonella enterica subsp. enterica serovar Heidelberg (S. Heidelberg) in turkey poults. However, the effect of the challenge and the application of the treatments on the cecal metabolome has yet to be elucidated. Thus, the objective of the present study was to characterize alterations in the metabolic profiles of cecal contents collected from poults following S. Heidelberg challenge and treatment with Lactobacillus salivarius UMNPBX2 and L. ingluviei UMNPBX19 (LB), trans-cinnamaldehyde (TC), or a combination of both (CO) using untargeted gas chromatography–mass spectrometry (GC-MS). Poults in the challenged control (PC) group had the most distinct and convergent metabolome profiles, with the most pronounced disparity observed compared to the unchallenged control (NC), indicating the effect of the S. Heidelberg challenge. Perturbations in metabolites in the primary bile acid biosynthesis, pentose and glucuronate interconversions, and steroid biosynthesis were the most prominent. The greater abundance of metabolites, such as primary bile acids and sugars, in the PC group may be associated with S. Heidelberg colonization or potential shifts in microbiota. The treatments yielded varying effects on the metabolome profiles, with the TC and CO groups exhibiting the closest similarity, although TC was more similar to NC. The findings revealed alterations to ceca-associated metabolites, which are likely a response to the S. Heidelberg challenge and the application of the TC and LB treatments. Additional studies are needed to validate the possible causal relationship between the observed shifts. Gaining insight into the alterations to the metabolic microenvironment in the avian cecum will help elucidate the mechanisms by which they facilitate Salmonella persistence. Understanding these relationships can aid in designing more effective pre-harvest Salmonella control strategies and enhancing the efficacy of interventions within the flock. Full article