Concentrations Of Specific Metabolites Research Articles

Dual-Purpose Aptamer-Based Sensors for Real-Time, Multiplexable Monitoring of Metabolites in Cell Culture Media.

The availability of high-frequency, real-time measurements of the concentrations of specific metabolites in cell culture systems will enable a deeper understanding of cellular metabolism and facilitate the application of good laboratory practice standards in cell culture protocols. However, currently available approaches to this end either are constrained to single-time-point and single-parameter measurements or are limited in the range of detectable analytes. Electrochemical aptamer-based (EAB) biosensors have demonstrated utility in real-time monitoring of analytes in vivo in blood and tissues. Here, we characterize a pH-sensing capability of EAB sensors that is independent of the specific target analyte of the aptamer sequence. We applied this dual-purpose EAB to the continuous measurement of pH and phenylalanine in several in vitro cell culture settings. The miniature EAB sensor that we developed exhibits rapid response times, good stability, high repeatability, and biologically relevant sensitivity. We also developed and characterized a leak-free reference electrode that mitigates the potential cytotoxic effects of silver ions released from conventional reference electrodes. Using the resulting dual-purpose sensor, we performed hourly measurements of pH and phenylalanine concentrations in the medium superfusing cultured epithelial tumor cell lines (A549, MDA-MB-23) and a human fibroblast cell line (MRC-5) for periods of up to 72 h. Our scalable technology may be multiplexed for high-throughput monitoring of pH and multiple analytes in support of the broad metabolic qualification of microphysiological systems.

Diagnostic Accuracy of Urinary Biomarkers in Periodontitis: A Systematic Review and Meta-Analysis.

Biomarkers can be measured in various biological samples. Urine is among the most useful biofluids for routine testing, and several experimental and clinical studies support its role as a tool for the diagnosis and prevention of various diseases. The present systematic review aimed to examine periodontitis-specific urine biomarkers that could have a diagnostic relevance and to provide a qualitative assessment of the current literature. Relevant studies identified from PubMed, Embase, Cochrane Library, and Scopus databases were examined to answer the following PECO question: "Could the concentration of specific metabolites in the urine be related to periodontal health and what is their diagnostic accuracy?". Quality of included studies was rated using ROBINS-I tool. Meta-analysis was conducted on available quantitative data. After the screening of 768 titles, five studies were included in qualitative synthesis. The studies included referred to the evaluation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and neopterin. Meta-analysis was conducted for neopterin concentration on data available in four studies involving 129 participants. Higher concentrations of neopterin were found in periodontitis-affected patients compared to controls and patients treated for periodontitis. The literature appears controversial in attributing a role to neopterin and 8-OHdG as periodontal biomarkers, highlighting the need for further clinical studies on this topic. While some studies report variations in 8-OHdG and neopterin levels in periodontally affected patients versus either controls or periodontally treated patients, the level of evidence appears still limited to draw firm conclusions (PROSPERO CRD42020222681).

Emerging Role of Functional Magnetic Resonance Spectroscopy (MRS) to Monitor Response to Kinase Inhibitors in Cancer.

Inhibitors of kinases involved in signaling and other intracellular pathways, have revolutionized cancer treatment by providing highly targeted and effective therapies. However, timely monitoring treatment response remains a considerable challenge since conventional methods such as assessing changes in tumor volume do not adequately capture early responses or resistance development, due to the predominantly cytostatic rather than cytotoxic effect of kinase inhibitors. Magnetic resonance spectroscopy (MRS) is a non-invasive imaging technique that can provide insights into cellular metabolism by detecting changes in metabolite concentrations. By measuring metabolite levels, MRS offers a means to assess treatment response in real-time, providing earlier indications of efficacy or resistance compared to conventional imaging modalities. Bruton's Tyrosine Kinase (BTK) is a critical enzyme involved in B-cell receptor signaling. BTK inhibitors have been approved for the treatment of Mantle Cell Lymphoma (MCL) and other B-cell malignancies. Recent studies involving genome-scale gene expression, metabolomic, and fluxomic analyses have demonstrated that ibrutinib, an index BTK inhibitor, profoundly affects the key metabolic pathways in MCL cells., including glycolysis, glutaminolysis, pentose shunt, TCA cycle and phospholipid metabolism. Importantly, the effects of ibrutinib on MCL cells directly and proportionately correlates with their sensitivity to the drug. Consequently, changes in specific metabolite concentrations detectable non-invasively by MRS such as lactate and alanine reflecting mostly the status of cellular glycolysis and glutaminolysis, respectively, have emerged as potential biomarkers for predicting response and resistance of MCL cells to BTK inhibition, both in vitro and in vivo. Preparations to validate the utility of these biomarkers in clinical setting are under way. These studies may pave the way to monitor therapeutic response to kinase inhibitors also in other types of cancer.

Misalignment in circadian‐regulated glymphatic clearance as a driver of neurodegeneration

AbstractBackgroundGlymphatic system (GS) is a glial‐dependent perivascular network that under circadian regulation (Hablitz et al, 2020) controls the clearance of waste products in the central nervous system during the sleep (Xie et al, 2013) and its function is suppressed in several neurodegenerative diseases. Our aim is to investigate whether alteration in the circadian‐controlled dynamics of the GS may be the linker between the periphery and the brain. Our hypothesis is that the disruption of the gut‐brain dialogue, due to peripheral colonic inflammation, alters the circadian clockwork both in periphery and CNS, thereby impacting on the circadian‐regulated GS flux in the brain.MethodThe peripheral inflammation was obtained using an acute dextran sulfate sodium (DSS) mouse model of colitis. Alterations in GS dynamics and in the relative concentrations of selected metabolites in the brain have been evaluated by MRI and MRS, respectively. Aquaporin‐4, α‐syntropin, Connexin‐43 as well as clock genes expression have been assessed in colon, and in different brain areas, by real‐time PCR. AQP4 mis‐location has been evaluated by transmission electron microscopy.ResultOur data demonstrate that, in DSS‐driven acute colitis model, the inflammatory hit strongly impacts on the circadian clockwork both at peripheric and central level, by altering the expression of the core clock components. Such alteration in the clock components expression pattern correlates with changes in GS dynamics in the brain. In particular, colonic inflammation impacts on the expression of astrocyte aquaporin‐4, as well as of α‐syntropin and Connexin‐43, in both cerebellum and cortex, thus suggesting a potential molecular derangement in the regulation of glymphatic influx. Alterations in GS dynamics have also been detected in the relative concentrations of specific metabolites in selective brain areas by MRS. As a consequence of brain changes in GS dynamics, we observed an increased phospho‐tau deposition in the hippocampus of DSS mice.ConclusionThe characterization of the cascade of events and the relationship among gut inflammation, glymphatic influx alteration and brain waste product deposition has a novel significance since it will allow understanding how a persistent peripheral enteric hit may disorganize a central hierarchy thus triggering a self‐sustaining process prodromal of neurodegeneration.

Human Serum and Salivary Metabolomes: Diversity and Closeness

Saliva, which contains molecular information that may reflect an individual’s health status, has become a valuable tool for discovering biomarkers of oral and general diseases. Due to the high vascularization of the salivary glands, there is a molecular exchange between blood and saliva. However, the composition of saliva is complex and influenced by multiple factors. This study aimed to investigate the possible relationships between the salivary and serum metabolomes to gain a comprehensive view of the metabolic phenotype under physiological conditions. Using 1H-NMR spectroscopy, we obtained the serum metabolite profiles of 20 healthy young individuals and compared them with the metabolomes of parotid, submandibular/sublingual, and whole-saliva samples collected concurrently from the same individuals using multivariate and univariate statistical analysis. Our results show that serum is more concentrated and less variable for most of the shared metabolites than the three saliva types. While we found moderate to strong correlations between serum and saliva concentrations of specific metabolites, saliva is not simply an ultrafiltrate of blood. The intense oral metabolism prevents very strong correlations between serum and salivary concentrations. This study contributes to a better understanding of salivary metabolic composition, which is crucial for utilizing saliva in laboratory diagnostics.

Phosphorus deficiency alters root length, acid phosphatase activity, organic acids, and metabolites in root exudates of soybean cultivars.

Phosphorus (P) deficiency alters the root morphological and physiological traits of plants. This study investigates how soybean cultivars with varying low-P tolerance values respond to different P levels in hydroponic culture by assessing alterations in root length, acid phosphatase activity, organic acid exudation, and metabolites in root exudates. Three low-P-tolerant cultivars ('Maetsue,' 'Kurotome,' and 'Fukuyutaka') and three low-P-sensitive cultivars ('Ihhon,' 'Chizuka,' and 'Komuta') were grown under 0 (P0) and 258 μM P (P8) for 7 and 14 days after transplantation (DAT). Low-P-tolerant cultivars increased root length by 31% and 119%, which was lower than the 62% and 144% increases in sensitive cultivars under P0 compared to P8 at 7 and 14 DAT, respectively. Acid phosphatase activity in low-P-tolerant cultivars exceeded that in sensitive cultivars by 5.2-fold and 2.0-fold at 7 and 14 DAT. Root exudates from each cultivar revealed 177 metabolites, with higher organic acid exudation in low-P-tolerant than sensitive cultivars under P0. Low-P-tolerant cultivars increased concentrations of specific metabolites (oxalate, GABA, quinate, citrate, AMP, 4-pyridoxate, and CMP), distinguishing them from low-P-sensitive cultivars under P0. The top five metabolomic pathways (purine metabolism, arginine and proline metabolism, TCA cycle, glyoxylate and dicarboxylate metabolism, alanine, aspartate, and glutamate metabolism) were more pronounced in low-P-tolerant cultivars at 14 DAT. These findings indicate that increasing root length was not an adaptation strategy under P deficiency; instead, tolerant cultivars exhibit enhanced root physiological traits, including increased acid phosphatase activity, organic acid exudation, specific metabolite release, and accelerated metabolic pathways under P deficiency.

SAT441 Association Of PFOS Exposure And The Risk Of Coronary Artery Disease In Postmenopausal Women

Abstract Disclosure: A. Arredondo Eve: None. E. Tunc: None. D. Mehta: None. H. Erbak-Yilmaz: None. S. Volkan Emren: None. F. Akyildiz-Akcay: None. Z. Madak Erdogan: None. Cardiovascular diseases (CVD) are the number one cause of death globally. In addition to traditional risk factors such as unhealthy lifestyles (smoking, obesity, sedentary) and genetics, common environmental exposures, including persistent environmental contaminants, may also influence cardiovascular disease risk. Perfluoroalkyl substances (PFAS) are a class of highly fluorinated chemicals used in our daily household necessities and industrial products known to persist in our environment for years, causing health concerns that are now linked to endocrine disruptions and related outcomes in women, including interference of the cardiovascular and reproductive systems. In postmenopausal women, higher levels of PFAS are observed than in premenopausal women due to the cessation of menstruation, which is crucial for PFAS excretion. Because of these findings, we explored the association between Perfluorooctanoic acid (PFOA), Perfluorooctane sulfonate (PFOS), Perfluorobutanesulfonic acid (PFBS) in postmenopausal women from our previously established CVD cohort using liquid chromatography with tandem mass spectrometry (LC-MS-MS) analysis and supported by machine learning approaches. Here we show that PFOS levels were significantly higher in postmenopausal women with coronary cardiovascular disease (CAD) when compared to control and coronary microvascular disease (CMD) group. We also found that specific metabolite concentrations (alanine, isoleucine, proline, and tyrosine) were negatively associated with serum PFOS levels. A significant correlation with changes in the expression of proteins such as growth hormone (GH), tyrosine-protein kinase Mer (MERTK), metalloproteinase inhibitor 4 (TIMP4), transferrin receptor protein 1 (TFRC), thrombospondin-2 (THBS2) and PFOS was observed. Our findings may provide new insight into the potential mechanism underlying the increased risk of cardiovascular events in postmenopausal women and the emerging evidence on PFAS-induced risk of cardiovascular diseases in this vulnerable population. Presentation: Saturday, June 17, 2023

Endocrine and metabolic profiles in pregnant and non-pregnant Criollo mares

Gestation leads to metabolic changes, prioritizing nutrients’ delivery to the developing fetus (Fowden et al. Equine Veterinary Journal. 1984; 16(4), 239-246). Insulin, adiponectin, and leptin are key metabolic hormones that have been associated with pregnancy success in several species (Coverdale et al. J Anim Sci. 2015; 93(7), 3261-3267.; Meikle et al. Anim. Reprod., v.15, (Suppl.1), p.899-911. 2018). Information on these hormones and their metabolites during gestation of horses is lacking, specifically in native breeds. Therefore, the objective of this study was to establish the endocrine-metabolic profile in pregnant and non-pregnant Criollo mares, a native breed that is popular in South America. Mares (n=56) were categorized as pregnant (n=41) or non-pregnant (n=15). Animals were bled between days 200 and 250 of gestation and the Body Condition Score (BCS) was determined (scale 1-9, Henneke et al. Equine Veterinary Journal. 1983; 15(4), 371-372). The controls were assayed at the same time samples were taken, during the winter, between June and August. Insulin was determined by immunoradiometric analysis, leptin and adiponectin by Radioimmunoassay and other biochemistry variables by spectrophotometer. Hematology variables were determined by hematologic counter. Variables were analyzed by ANOVA using a mixed procedure. The reproductive status did not affect theleptin (9.4±1.6 vs 9.0±1.0 ng/mL, P=0.804 in pregnant and non-pregnant mares respectively), adiponectin concentrations (18.9±2.7 vs 15.5±1.6 ng/mL, P=0.304 in pregnant and non-pregnant mares respectively), nor the BCS (7.3±0.2 vs 7.6±0.1, P=0.356 in pregnant and non-pregnant mares respectively). Insulin (18.2±2.9 vs 17.7±1.7 UI/mL, P=0.644 in pregnant and non-pregnant mares respectively) and glucose (87.0±2.6 vs 83.0±1.6 mg/dL, P=0.180 in pregnant and non-pregnant mares respectively) concentrations were not affected either. Cholesterol concentrations were not affected by the reproductive status, while triglyceride concentrations were higher in pregnant when compared to non-pregnant mares (31.0±1.9 vs 21.6±3.1 mg/dL, P=0.012). Urea and creatinine concentrations were also higher in pregnant than in non-pregnant mares (52.8±1.0 vs 46.7±1.6 mg/dL, P=0.002 and 1.25±0.03 vs 1.01±0.05 mg/dL, P=0.0002 respectively). Hepatic enzymes and white blood cell count were not affected by the reproductive status. This study shows higher concentrations of triglycerides, urea and creatinine in pregnant mares. These changes could be associated with the metabolic prioritization of glucose delivery to the developing fetus, which leads to a differential nutrient partitioning, as reflected in different concentrations of specific metabolites of the protein and lipid pathways.

The interplay between the gut microbiota and metabolism during the third trimester of pregnancy.

The gut microbiota undergoes dynamic changes during pregnancy. The gut microbial and metabolic networks observed in pregnant women have not been systematically analyzed. The primary purpose of this study was to explore the alterations in the gut microbiota and metabolism during late pregnancy and investigate the associations between the gut microbiota and metabolism. A total of thirty healthy pregnant women were followed from 30 to 32 weeks of gestation to full term. Fecal samples were collected for microbiome analysis and untargeted metabolomic analysis. The characteristics of the gut microbiota were evaluated by 16S ribosomal RNA gene sequencing of the V3-V4 regions. The plasma samples were used for untargeted metabolomic analysis with liquid chromatography-tandem mass spectrometry. The interplay between the gut microbiota and metabolism was analyzed further by bioinformatics approaches. We found that the relative abundances of Sellimonas and Megamonas were higher at full term, whereas that of Proteobacteria was lower. The correlation network of the gut microbiota tended to exhibit weaker connections from 32 weeks of gestation to the antepartum timepoint. Changes in the gut microbiota during late pregnancy were correlated with the absorbance and metabolism of microbiota-associated metabolites, such as fatty acids and free amino acids, thereby generating a unique metabolic system for the growth of the fetus. Decreasing the concentration of specific metabolites in plasma and increasing the levels of palmitic acid and 20-hydroxyarachidonic acid may enhance the transformation of a proinflammatory immune state as pregnancy progresses.

Changes in Metabolism as a Diagnostic Tool for Lung Cancer: Systematic Review.

Lung cancer is the leading cause of cancer-related mortality worldwide, with five-year survival rates varying from 3–62%. Screening aims at early detection, but half of the patients are diagnosed in advanced stages, limiting therapeutic possibilities. Positron emission tomography-computed tomography (PET-CT) is an essential technique in lung cancer detection and staging, with a sensitivity reaching 96%. However, since elevated 18F-fluorodeoxyglucose (18F-FDG) uptake is not cancer-specific, PET-CT often fails to discriminate between malignant and non-malignant PET-positive hypermetabolic lesions, with a specificity of only 23%. Furthermore, discrimination between lung cancer types is still impossible without invasive procedures. High mortality and morbidity, low survival rates, and difficulties in early detection, staging, and typing of lung cancer motivate the search for biomarkers to improve the diagnostic process and life expectancy. Metabolomics has emerged as a valuable technique for these pitfalls. Over 150 metabolites have been associated with lung cancer, and several are consistent in their findings of alterations in specific metabolite concentrations. However, there is still more variability than consistency due to the lack of standardized patient cohorts and measurement protocols. This review summarizes the identified metabolic biomarkers for early diagnosis, staging, and typing and reinforces the need for biomarkers to predict disease progression and survival and to support treatment follow-up.

Metabolomics of gingival crevicular fluid to identify biomarkers for periodontitis: A systematic review with meta-analysis.

The present systematic review aimed to examine periodontitis-specific biomarkers in the gingival crevicular fluid (GCF) that could have a diagnostic relevance, and to provide a qualitative assessment of the current literature. Metabolites are reliable indicators of pathophysiological statuses, and their quantification in the GCF can provide an outlook of the changes associated with periodontitis and have diagnostic value. Relevant studies identified from PubMed, Embase, Cochrane Library, and Scopus databases were examined to answer the following PECO question: "In systemically healthy individuals, can concentration of specific metabolites in the GCF be used to discriminate subjects with healthy periodontium (H) or gingivitis from patients with periodontitis (P) and which is the diagnostic accuracy?" Quality of included studies was rated using a modified version of the QUADOMICS tool. Meta-analysis was conducted whenever possible. After the screening of 1,554 titles, 15 studies were selected, with sample size ranging from 30 to 93 subjects. Eleven studies performed targeted metabolomics analysis and provided data for 10 metabolites. Among the most consistent markers, malondialdehyde levels were found higher in the P group compared with H group (SMD=2.86; 95% CI: 1.64, 4.08). Also, a significant increase of 8-hydroxy-deoxyguanosine, 4-hydroxynonenal, and neopterin was detected in periodontally diseased sites, while glutathione showed an inverse trend. When considering data from untargeted metabolomic analysis in four studies, more than 40 metabolites were found significantly discriminant, mainly related to amino acids and lipids degradation pathways. Notably, only one study reported measures of diagnostic accuracy. Several metabolites were differentially expressed in GCF of subjects across different periodontal conditions, having a major potential for investigating periodontal pathophysiology and for site-specific diagnosis. Oxidative stress-related molecules, such as malondialdehyde and 8-hydroxy-deoxyguanosine, were the most consistently associated to periodontitis (PROSPERO CRD42020188482).

Clinical Application of Magnetic Resonance Spectroscopy in Diagnosis of Intracranial Mass Lesions.

Conventional MR imaging provides highly detailed anatomic information with unrivalled soft tissue contrast making it the mainstay in the diagnosis of suspected brain lesions. Despite this, MRI alone at times cannot answer the diagnostic questions in quite a few patients. Proton MR Spectroscopy (H-MRS) provides information on the metabolic composition within an area under interrogation. By comparing the relative concentrations of specific metabolites, the neuroradiologist can deduce critical information regarding neuronal cell density and integrity, cell membrane turnover, metabolic fuel, and possible necrosis in the region of interest. This provides a biochemical picture of the underlying pathology and thus aids in the diagnosis. This was a cross-sectional comparative study. Of the 63 patients examined by MRI and MRS for intracranial mass lesions, the radiologists were able to offer a single imaging diagnosis based on MRI alone in only 15 patients (23.8%) while when MRI imaging was combined with MR spectroscopy, a single imaging diagnosis was offered in 47 patients (74.6%). This was an overall statistically significant improvement. MRS aided the radiologist in offering a single diagnosis in high versus low-grade gliomas, high-grade gliomas versus tuberculomas, and recurrent tumours versus radiation necrosis.

Changes in the Salivary Metabolic Profile of Generalized Periodontitis Patients after Non-surgical Periodontal Therapy: A Metabolomic Analysis Using Nuclear Magnetic Resonance Spectroscopy.

Pattern analysis of the salivary metabolic profile has been proven accurate in discriminating between generalized periodontitis (GP) patients and healthy individuals (HI), as this disease modifies the salivary concentrations of specific metabolites. Due to the scarcity of data from previous studies, this study aimed to evaluate if non-surgical periodontal therapy (NST) could affect the metabolomic profile in GP patients’ saliva and if it compares to that of HI. Unstimulated salivary samples were collected from 11 HI and 12 GP patients before and 3 months after NST. Nuclear Magnetic Resonance (NMR) spectroscopy, followed by a supervised multivariate statistical approach on entire saliva spectra and partial least square (PLS) discriminant analysis, were performed to obtain metabolic profiles. In the GP group, periodontal treatment improved all clinical parameters, but not all the diseased sites were eradicated. PLS revealed an accuracy of 100% in distinguishing between metabolic profiles of GP patients before and after NST. Orthogonal projection to latent structure was able to discriminate between the three groups of subjects with an accuracy of 85.6%. However, the post-NST metabolic profile of GP patients could not be completely assimilated to that of HI. Although NST may produce significant changes in the metabolic profile, GP patients maintained a distinctive fingerprint compared to HI.

Metabolomics: population epidemiology and concordance in Australian children aged 11-12 years and their parents.

ObjectivesNuclear magnetic resonance (NMR) metabolomics is high throughput and cost-effective, with the potential to improve the understanding of disease and risk. We examine the circulating metabolic profile by quantitative NMR metabolomics of a sample of Australian 11–12 year olds children and their parents, describe differences by age and sex, and explore the correlation of metabolites in parent–child dyads.DesignThe population-based cross-sectional Child Health CheckPoint study nested within the Longitudinal Study of Australian Children.SettingBlood samples collected from CheckPoint participants at assessment centres in seven Australian cities and eight regional towns; February 2015–March 2016.Participants1180 children and 1325 parents provided a blood sample and had metabolomics data available. This included 1133 parent–child dyads (518 mother–daughter, 469 mother–son, 68 father–daughter and 78 father–son).Outcome measures228 metabolic measures were obtained for each participant. We focused on 74 biomarkers including amino acid species, lipoprotein subclass measures, lipids, fatty acids, measures related to fatty acid saturation, and composite markers of inflammation and energy homeostasis.ResultsWe identified differences in the concentration of specific metabolites between childhood and adulthood and in metabolic profiles in children and adults by sex. In general, metabolite concentrations were higher in adults than children and sex differences were larger in adults than in children. Positive correlations were observed for the majority of metabolites including isoleucine (CC 0.33, 95% CI 0.27 to 0.38), total cholesterol (CC 0.30, 95% CI 0.24 to 0.35) and omega 6 fatty acids (CC 0.28, 95% CI 0.23 to 0.34) in parent–child comparisons.ConclusionsWe describe the serum metabolite profiles from mid-childhood and adulthood in a population-based sample, together with a parent–child concordance. Differences in profiles by age and sex were observed. These data will be informative for investigation of the childhood origins of adult non-communicable diseases and for comparative studies in other populations.

The Relationships between Somatic Cells and Isoleucine, Leucine and Tyrosine Content in Cow Milk

The early diagnosis of cow subclinical mastitis represents a pivotal factor for a prompt and adequate animal treatment. Although several methods are available, the somatic cells count (SCC) still remains the elective test directly carried out on milk samples. In mastitis affected cows (even at subclinical stages), altered concentrations of specific metabolites, including free amino acids, is a well-known occurrence. In order to define the relationships between the variation of the unbound amino acids content with the SCC value, a direct ion-pairing reversed-phase method based on the use of the evaporative light-scattering detector (IP-RP-HPLC-ELSD) was applied to 65 cow milk samples. The statistical analysis of variance (ANOVA) was pursued in order to find a correlation between the SCC value and the concentration of isoleucine (Ile), leucine (Leu), valine (Val) and tyrosine (Tyr). Samples were divided in two groups according to their SCC value: Group I comprised all ones with SCC < 400,000 cells/mL; Group II encompassed those with a SCC > 400,000 cells/mL. Statistical analyses highlighted significant differences in the content of the branched-chain amino acids Ile and Leu, between the two groups (p < 0.02* and <0.005**, respectively). This study confirms that a dysmetabolism of certain free amino acids parallels elevated SCC values.

Characterization of Brain Metabolism by Nuclear Magnetic Resonance.

The noninvasive, quantitative ability of nuclear magnetic resonance (NMR) spectroscopy to characterize small molecule metabolites has long been recognized as a major strength of its application in biology. Numerous techniques exist for characterizing metabolism in living, excised, or extracted tissue, with a particular focus on 1 H-based methods due to the high sensitivity and natural abundance of protons. With the increasing use of high magnetic fields, the utility of in vivo 1 H magnetic resonance spectroscopy (MRS) has markedly improved for measuring specific metabolite concentrations in biological tissues. Higher fields, coupled with recent developments in hyperpolarization, also enable techniques for complimenting 1 H measurements with spectroscopy of other nuclei, such as 31 P and 13 C, and for combining measurements of metabolite pools with metabolic flux measurements. We compare ex vivo and in vivo methods for studying metabolism in the brain using NMR and highlight insights gained through using higher magnetic fields, the advent of dissolution dynamic nuclear polarization, and combining in vivo MRS and ex vivo NMR approaches.

Diurnal variation of NMR based blood metabolites in calves fed a high plane of milk replacer: a pilot study

BackgroundBlood profiles have been used to monitor herd health status, diagnose disorders, and predict the risk of diseases in cattle and calves. Characterizing plasma metabolites in dairy calves could provide further insight into daily metabolic variations and the mechanisms that lead to metabolic diseases. In addition, by understanding physiological ranges of plasma metabolites relative to meal and the time of feeding in healthy animals, veterinarians can accurately diagnose abnormalities with a blood test. For diagnostic purposes, nuclear magnetic resonance (NMR) spectroscopy shows promise as a new and reliable method to determine a large number of blood metabolites simultaneously.ResultsResults demonstrated that the concentration of specific metabolites in plasma (i.e., lysine, isoleucine, leucine, tyrosine, glutamine, creatine, and 1-methylhistidine) fluctuated around meal times, while others (i.e., glutamic acid, methanol, formic acid, and acetic acid) maintained a stable temporal concentration. In addition to temporal changes in concentration, results also characterized differences for overall plasma metabolite concentrations; for example, methionine had the lowest (38 μM) while glutamine had the highest concentration (239 μM) amongst plasma AA. This is the first report describing how the plasma metabolome changes during 24-h period in young calves fed an elevated plane of milk replacer twice daily.ConclusionsData from this pilot study will help to establish reference standards for future metabolic diagnostics in dairy calves. In addition, this pilot study illustrated that feeding milk replacer may influence plasma metabolite concentrations. With the rapid implementation of blood metabolomics in monitoring animal health, it is then important to consider the time of feeding during the day when interpreting metabolomics analysis results.

Modeling the flux of metabolites in the juvenile hormone biosynthesis pathway using generalized additive models and ordinary differential equations.

Juvenile hormone (JH) regulates development and reproductive maturation in insects. The corpora allata (CA) from female adult mosquitoes synthesize fluctuating levels of JH, which have been linked to the ovarian development and are influenced by nutritional signals. The rate of JH biosynthesis is controlled by the rate of flux of isoprenoids in the pathway, which is the outcome of a complex interplay of changes in precursor pools and enzyme levels. A comprehensive study of the changes in enzymatic activities and precursor pool sizes have been previously reported for the mosquito Aedes aegypti JH biosynthesis pathway. In the present studies, we used two different quantitative approaches to describe and predict how changes in the individual metabolic reactions in the pathway affect JH synthesis. First, we constructed generalized additive models (GAMs) that described the association between changes in specific metabolite concentrations with changes in enzymatic activities and substrate concentrations. Changes in substrate concentrations explained 50% or more of the model deviances in 7 of the 13 metabolic steps analyzed. Addition of information on enzymatic activities almost always improved the fitness of GAMs built solely based on substrate concentrations. GAMs were validated using experimental data that were not included when the model was built. In addition, a system of ordinary differential equations (ODE) was developed to describe the instantaneous changes in metabolites as a function of the levels of enzymatic catalytic activities. The results demonstrated the ability of the models to predict changes in the flux of metabolites in the JH pathway, and can be used in the future to design and validate experimental manipulations of JH synthesis.

Specific Metabolic Markers Are Associated with Future Waist-Gaining Phenotype in Women.

ObjectiveOur study aims to identify metabolic markers associated with either a gain in abdominal (measured by waist circumference) or peripheral (measured by hip circumference) body fat mass.MethodsData of 4 126 weight-gaining adults (18–75 years) from three population-based, prospective German cohort studies (EPIC, KORA, DEGS) were analysed regarding a waist-gaining (WG) or hip-gaining phenotype (HG). The phenotypes were obtained by calculating the differences of annual changes in waist minus hip circumference. The difference was displayed for all cohorts. The highest 10% of this difference were defined as WG whereas the lowest 10% were defined as HG. A total of 121 concordant metabolite measurements were conducted using Biocrates AbsoluteIDQ® kits in EPIC and KORA. Sex-specific associations with metabolite concentration as independent and phenotype as the dependent variable adjusted for confounders were calculated. The Benjamini-Hochberg method was used to correct for multiple testing.ResultsAcross studies both sexes gained on average more waist than hip circumference. We could identify 12 metabolites as being associated with the WG (n = 8) or HG (n = 4) in men, but none were significant after correction for multiple testing; 45 metabolites were associated with the WG (n = 41) or HG (n = 4) in women. For WG, n = 21 metabolites remained significant after correction for multiple testing. Respective odds ratios (OR) ranged from 0.66 to 0.73 for tryptophan, the diacyl-phosphatidylcholines (PC) C32:3, C36:0, C38:0, C38:1, C42:2, C42:5, the acyl-alkyl-PCs C32:2, C34:0, C36:0, C36:1, C36:2, C38:0, C38:2, C40:1, C40:2, C40:5, C40:6, 42:2, C42:3 and lyso-PC C17:0.ConclusionBoth weight-gaining men and women showed a clear tendency to gain more abdominal than peripheral fat. Gain of abdominal fat seems to be related to an initial metabolic state reflected by low concentrations of specific metabolites, at least in women. Thus, higher levels of specific PCs may play a protective role in gaining waist circumference.

Ligand-Induced Stabilization of a Duplex-like Architecture Is Crucial for the Switching Mechanism of the SAM-III Riboswitch.

Riboswitches are structured RNA motifs that control gene expression by sensing the concentrations of specific metabolites and make up a promising new class of antibiotic targets. S-Adenosylmethionine (SAM)-III riboswitch, mainly found in lactic acid bacteria, is involved in regulating methionine and SAM biosynthetic pathways. SAM-III riboswitch regulates the gene expression by switching the translation process on and off with respect to the absence and presence of the SAM ligand, respectively. In this study, an attempt is made to understand the key conformational transitions involved in ligand binding using atomistic molecular dynamics (MD) simulations performed in an explicit solvent environment. G26 is found to recognize the SAM ligand by forming hydrogen bonds, whereas the absence of the ligand leads to opening of the binding pocket. Consistent with experimental results, the absence of the SAM ligand weakens the base pairing interactions between the nucleobases that are part of the Shine-Dalgarno (SD) and anti-Shine-Dalgarno (aSD) sequences, which in turn facilitates recognition of the SD sequence by ribosomes. Detailed analysis reveals that a duplex-like structure formed by nucleotides from different parts of the RNA and the adenine base of the ligand is crucial for the stability of the completely folded state in the presence of the ligand. Previous experimental studies have shown that the SAM-III riboswitch exists in equilibrium between the unfolded and partially folded states in the absence of the ligand, which completely folds upon binding of the ligand. Comparison of the results presented here to the available experimental data indicates the structures obtained using the MD simulations resemble the partially folded state. Thus, this study provides a detailed understanding of the fully and partially folded structures of the SAM-III riboswitch in the presence and absence of the ligand, respectively. This study hypothesizes a dual role for the SAM ligand, which facilitates conformational switching between partially and fully folded states by forming a stable duplex-like structure and strengthening the interactions between SD and aSD nucleotides.