Associations between TCA cycle plasma metabolites and fatigue in black females with systemic lupus erythematosus: An untargeted metabolomics pilot study.

OBJECTIVE: In this pilot study, we used untargeted metabolomics to identify biochemical mechanisms or biomarkers potentially underlying SLE-related fatigue. METHODS: Metabolon conducted untargeted metabolomic plasma profiling using ultrahigh performance liquid chromatography/tandem mass spectrometry on plasma samples of 23 Black females with systemic lupus erythematosus (SLE) and 21 no SLE controls. Fatigue phenotypes of general fatigue, physical fatigue, mental fatigue, reduced activity, and reduced motivation were measured with the reliable and valid Multidimensional Fatigue Inventory (MFI). RESULTS: A total of 290 metabolites were significantly different between the SLE and no SLE groups, encompassing metabolites related to glycolysis, TCA cycle activity, heme catabolism, branched chain amino acids, fatty acid metabolism, and steroids. Within the SLE group, controlling for age and co-morbidities, TCA cycle metabolites of alpha-ketoglutarate (AKG) and succinate were statistically significantly associated (p < .05) with physical and general fatigue. CONCLUSION: While pervasive perturbations in the entire TCA cycle have been implicated as a potential mechanism for fatigue, our results suggest individual metabolites of AKG and succinate may be potential biomarkers or targets of intervention for fatigue symptom management in SLE. Additionally, perturbations in heme metabolism in the SLE group provide additional insights into mechanisms that promote systemic inflammation.

Determination of succinic acid and lactic acid in pigs' serum, intestinal contents, and meat by ultrahigh-performance liquid chromatography-tandem mass spectrometry.

RATIONALE: Succinic acid and lactic acid have been associated with diarrhea in weaned piglets. The level of succinic acid and lactic acid in serum, meat, and intestinal contents is important to elucidate the mechanism of diarrhea in weaned piglets. METHODS: A facile method was developed for the quantification of succinic acid and lactic acid in pigs' serum, intestinal contents, and meat using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC/MS/MS). The serum samples underwent protein precipitation with methanol. The meat and intestinal contents were freeze-dried and homogenized using a tissue grinding apparatus. Methanol-water mixture (80:20, v/v) was used for homogenizing the meat, while water was used for homogenizing the intestinal contents. An additional step of protein precipitation with acetonitrile was required for the intestinal contents. The resulting solution was diluted with water before being analyzed by UHPLC/MS/MS. Separation of succinic acid and lactic acid could be achieved within 3 min using a Kinetic XB-C18 column. RESULTS: The coefficients of variation for peak areas of succinic acid and lactic acid were less than 5.0%. The established method demonstrated good linearity as indicated by correlation coefficients exceeding 0.996. Additionally, satisfactory recoveries ranging from 88.58% to 108.8% were obtained. The detection limits (RS/N = 3) for succinic acid and lactic acid were determined to be 0.75 ng/mL and 0.02 µg/mL, respectively. CONCLUSION: This method exhibited high sensitivity, simplicity in operation, and small sample weight, making it suitable for quantitative determination of succinic acid and lactic acid in pigs' serum, intestinal contents, and meat. The method developed will provide valuable technical support in studying the metabolic mechanisms of succinic acid and lactic acid in pigs.

Elevated plasma succinate levels are linked to higher cardiovascular disease risk factors in young adults.

BACKGROUND: Succinate is produced by both host and microbiota, with a key role in the interplay of immunity and metabolism and an emerging role as a biomarker for inflammatory and metabolic disorders in middle-aged adults. The relationship between plasma succinate levels and cardiovascular disease (CVD) risk in young adults is unknown. METHODS: Cross-sectional study in 100 (65% women) individuals aged 18-25 years from the ACTIvating Brown Adipose Tissue through Exercise (ACTIBATE) study cohort. CVD risk factors, body composition, dietary intake, basal metabolic rate, and cardiorespiratory fitness were assessed by routine methods. Plasma succinate was measured with an enzyme-based assay. Brown adipose tissue (BAT) was evaluated by positron emission tomography, and circulating oxylipins were assessed by targeted metabolomics. Fecal microbiota composition was analyzed in a sub-sample. RESULTS: Individuals with higher succinate levels had higher levels of visceral adipose tissue (VAT) mass (+ 42.5%), triglycerides (+ 63.9%), C-reactive protein (+ 124.2%), diastolic blood pressure (+ 5.5%), and pro-inflammatory omega-6 oxylipins than individuals with lower succinate levels. Succinate levels were also higher in metabolically unhealthy individuals than in healthy overweight/obese peers. Succinate levels were not associated with BAT volume or activity or with fecal microbiota composition and diversity. CONCLUSIONS: Plasma succinate levels are linked to a specific pro-inflammatory omega-6 signature pattern and higher VAT levels, and seem to reflect the cardiovascular status of young adults.

Differences in the serum metabolome and lipidome identify potential biomarkers for seronegative rheumatoid arthritis versus psoriatic arthritis.

OBJECTIVES: The differential diagnosis of seronegative rheumatoid arthritis (negRA) and psoriasis arthritis (PsA) is often difficult due to the similarity of symptoms and the unavailability of reliable clinical markers. Since chronic inflammation induces major changes in the serum metabolome and lipidome, we tested whether differences in serum metabolites and lipids could aid in improving the differential diagnosis of these diseases. METHODS: Sera from negRA and PsA patients with established diagnosis were collected to build a biomarker-discovery cohort and a blinded validation cohort. Samples were analysed by proton nuclear magnetic resonance. Metabolite concentrations were calculated from the spectra and used to select the variables to build a multivariate diagnostic model. RESULTS: Univariate analysis demonstrated differences in serological concentrations of amino acids: alanine, threonine, leucine, phenylalanine and valine; organic compounds: acetate, creatine, lactate and choline; and lipid ratios L3/L1, L5/L1 and L6/L1, but yielded area under the curve (AUC) values lower than 70%, indicating poor specificity and sensitivity. A multivariate diagnostic model that included age, gender, the concentrations of alanine, succinate and creatine phosphate and the lipid ratios L2/L1, L5/L1 and L6/L1 improved the sensitivity and specificity of the diagnosis with an AUC of 84.5%. Using this biomarker model, 71% of patients from a blinded validation cohort were correctly classified. CONCLUSIONS: PsA and negRA have distinct serum metabolomic and lipidomic signatures that can be used as biomarkers to discriminate between them. After validation in larger multiethnic cohorts this diagnostic model may become a valuable tool for a definite diagnosis of negRA or PsA patients.

Comprehensive lipidomic, metabolomic and proteomic profiling reveals the role of immune system in vitiligo.

BACKGROUND: Vitiligo is a common depigmentation disorder resulting from destruction of melanocytes, and has both genetic and environmental influences. Although genomic analyses have been performed to investigate the pathogenesis of vitiligo, the lipidomics, metabolomics and proteomics of serum have not been reported, and the role of small molecules and serum proteins in vitiligo remains unknown. AIM: To study the metabolite and protein profiles in patients with vitiligo and healthy controls (HCs). METHODS: Plasma samples from 60 participants (29 patients with vitiligo and 31 HCs) were analysed. Untargeted lipidomics, metabolomics and isobaric tags for relative and absolute quantification-based proteomics were performed using high performance liquid chromatography-tandem mass spectrometry. In addition, to validate differentially expressed metabolites in patients with vitiligo, plasma enzyme-linked immunosorbent assay was performed. RESULTS: We identified differential expression of several metabolites and proteins involved in the immune system. Among these metabolites and proteins, lysophosphatidylcholine, platelet-activating factor, sn-glycerol-3-phosphocholine, succinic acid, CXCL4 and CXCL7 were significantly elevated in the plasma of patients with vitiligo, while aspartate was downregulated. CONCLUSION: Our study has characterized several serum metabolites and proteins that could be potential candidate biomarkers in vitiligo, and provides a comprehensive insight into the role of immune system and aspartate metabolism in vitiligo.

Deep Vein Thrombosis Exhibits Characteristic Serum and Vein Wall Metabolic Phenotypes in the Inferior Vena Cava Ligation Mouse Model.

OBJECTIVES: Deep vein thrombosis (DVT) is a major health problem, responsible for significant morbidity and mortality. The identification of a simple and effective diagnostic biomarker of DVT remains a challenge. Metabolomics have recently emerged as a new powerful scientific tool to characterise metabolic phenotypes of complex diseases and investigate small molecules in biofluids. The aim of the study was to identify the blood and vein wall metabolomic signature of DVT in a murine experimental model. METHODS: An established inferior vena cava ligation mouse model of DVT (n=10) was used and compared with sham surgery controls (n=10). Comprehensive untargeted metabolic profiling of serum and vein wall extracts was undertaken using liquid chromatography coupled mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy. RESULTS: Multivariate and univariate statistical analysis demonstrated a differential metabolic profile when comparing DVT mice and control animals. Serum from DVT mice was characterised by differential concentrations of adenosine (decreased in DVT mice 9.6 fold), adenine (decreased 10.6 fold), and tricyclic acid cycle (TCA) intermediates, including citrate, succinate, and fumarate (1.5, 2.3, and 2.8 fold decreases, respectively). l-carnitine was found to be of greater abundance in the serum of DVT animals (67.0 fold change). A number of lipid moiety classes, including sphingomyelins, phosphatidylcholines, and triglycerides, were differentially abundant. Several metabolites were found in vein wall, including acetylcarnitine (increased in DVT mice 1.9 fold), adenosine (increased 2.2 fold), and ceramide (increased 2.7 fold). Correlation analysis illustrated the biochemical relationships between assigned metabolites, with the discriminatory molecules being highly correlated with each other, in both serum and vein wall. CONCLUSIONS: The present findings demonstrate that metabolic dysregulations in DVT centre on energy metabolism, sphingolipid, and adenosine metabolism, representing a DVT specific metabolite signature in a murine experimental model.

Serum metabolic changes in rats after intragastric administration of dextromethorphan.

Dextromethorphan is recognized as a substance of abuse around the world. An estimated 3.1 million people between the ages of 12 and 25 years (5.3%) misused over-the-counter cough and cold medications in 2006. In this study, we developed a serum metabolomic method by gas chromatography-mass spectrometry (GC-MS) to evaluate the effect of abuse of dextromethorphan on rats. The dextromethorphan-treated rats were given 12, 24 and 48 mg/kg (low, medium, high) of dextromethorphan by intragastric administration each day for 3 days. Partial least squares-discriminate analysis revealed that intragastric administration of dextromethorphan induced metabolic perturbations. Compared with the control (healthy) group, the levels of propanoic acid, urea, heptafluorobutanoic acid, 2-hexyldecanoic acid and butanedioic acid of the low group decreased; levels of propanoic acid and heptafluorobutanoic acid of the medium group decreased, while that of benzoic acid increased; and levels of 2-hexyldecanoic acid, glycerol and butanedioic acid of the high group increased. These biomarkers are involved in the citric acid cycle, urea cycle, glycerolipid metabolism and tricarboxylic acid cycle. The results indicate that the metabolomic method by GC-MS may be useful to elucidate abuse of dextromethorphan. According to the pathological changes in the liver at different dosages, dextromethorphan is not hepatotoxic after intragastric administration of 12, 24 and 48 mg/kg for 3 days.

An LC-MS/MS method for serum methylmalonic acid suitable for monitoring vitamin B12 status in population surveys.

Methylmalonic acid (MMA), a functional indicator of vitamin B12 insufficiency, was measured in the US population in the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2004 using a GC/MS procedure that required 275 µL of sample and had a low throughput (36 samples/run). Our objective was to introduce a more efficient yet highly accurate LC-MS/MS method for NHANES 2011-2014. We adapted the sample preparation with some modifications from a published isotope-dilution LC-MS/MS procedure. The procedure utilized liquid-liquid extraction and generation of MMA dibutyl ester. Reversed-phase chromatography with isocratic elution allowed baseline resolution of MMA from its naturally occurring structural isomer succinic acid within 4.5 min. Our new method afforded an increased throughput (≤160 samples/run) and measured serum MMA with high sensitivity (LOD = 22.1 nmol/L) in only 75 µL of sample. Mean (±SD) recovery of MMA spiked into serum (2 d, 4 levels, 2 replicates each) was 94 % ± 5.5 %. Total imprecision (41 d, 2 replicates each) for three serum quality control pools was 4.9 %-7.9 % (97.1-548 nmol/L). The LC-MS/MS method showed excellent correlation (n = 326, r = 0.99) and no bias (Deming regression, Bland-Altman analysis) compared to the previous GC/MS method. Both methods produced virtually identical mean (±SD) MMA concentrations [LC-MS/MS: 18.47 ± 0.71 ng/mL (n = 17), GC/MS: 18.18 ± 0.67 ng/mL (n = 11)] on a future plasma reference material compared with a GC/MS method procedure from the National Institute of Standards and Technology [18.41 ± 0.70 ng/mL (n = 15)]. No adjustment will be necessary to compare previous (1999-2004) to future (2011-2014) NHANES MMA data.

Metabolic alterations in the sera of Chinese patients with mild persistent asthma: a GC-MS-based metabolomics analysis.

AIM: To character the specific metabolomics profiles in the sera of Chinese patients with mild persistent asthma and to explore potential metabolic biomarkers. METHODS: Seventeen Chinese patients with mild persistent asthma and age- and sex-matched healthy controls were enrolled. Serum samples were collected, and serum metabolites were analyzed using GC-MS coupled with a series of multivariate statistical analyses. RESULTS: Clear intergroup separations existed between the asthmatic patients and control subjects. A list of differential metabolites and several top altered metabolic pathways were identified. The levels of succinate (an intermediate in tricarboxylic acid cycle) and inosine were highly upregulated in the asthmatic patients, suggesting a greater effort to breathe during exacerbation and hypoxic stress due to asthma. Other differential metabolites, such as 3,4-dihydroxybenzoic acid and phenylalanine, were also identified. Furthermore, the differential metabolites possessed higher values of area under the ROC curve (AUC), suggesting an excellent clinical ability for the prediction of asthma. CONCLUSION: Metabolic activity is significantly altered in the sera of Chinese patients with mild persistent asthma. The data might be helpful for identifying novel biomarkers and therapeutic targets for asthma.

Succinate causes pathological cardiomyocyte hypertrophy through GPR91 activation.

BACKGROUND: Succinate is an intermediate of the citric acid cycle as well as an extracellular circulating molecule, whose receptor, G protein-coupled receptor-91 (GPR91), was recently identified and characterized in several tissues, including heart. Because some pathological conditions such as ischemia increase succinate blood levels, we investigated the role of this metabolite during a heart ischemic event, using human and rodent models. RESULTS: We found that succinate causes cardiac hypertrophy in a GPR91 dependent manner. GPR91 activation triggers the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), the expression of calcium/calmodulin dependent protein kinase IIδ (CaMKIIδ) and the translocation of histone deacetylase 5 (HDAC5) into the cytoplasm, which are hypertrophic-signaling events. Furthermore, we found that serum levels of succinate are increased in patients with cardiac hypertrophy associated with acute and chronic ischemic diseases. CONCLUSIONS: These results show for the first time that succinate plays an important role in cardiomyocyte hypertrophy through GPR91 activation, and extend our understanding of how ischemia can induce hypertrophic cardiomyopathy.

Could thermal sensitivity of mitochondria determine species distribution in a changing climate?

For many aquatic species, the upper thermal limit (Tmax) and the heart failure temperature (THF) are only a few degrees away from the species' current environmental temperatures. While the mechanisms mediating temperature-induced heart failure (HF) remain unresolved, energy flow and/or oxygen supply disruptions to cardiac mitochondria may be impacted by heat stress. Recent work using a New Zealand wrasse (Notolabrus celidotus) found that ATP synthesis capacity of cardiac mitochondria collapses prior to T(HF). However, whether this effect is limited to one species from one thermal habitat remains unknown. The present study confirmed that cardiac mitochondrial dysfunction contributes to heat stress-induced HF in two additional wrasses that occupy cold temperate (Notolabrus fucicola) and tropical (Thalassoma lunare) habitats. With exposure to heat stress, T. lunare had the least scope to maintain heart function with increasing temperature. Heat-exposed fish of all species showed elevated plasma succinate, and the heart mitochondria from the cold temperate N. fucicola showed decreased phosphorylation efficiencies (depressed respiratory control ratio, RCR), cytochrome c oxidase (CCO) flux and electron transport system (ETS) flux. In situ assays conducted across a range of temperatures using naive tissues showed depressed complex II (CII) and CCO capacity, limited ETS reserve capacities and lowered efficiencies of pyruvate uptake in T. lunare and N. celidotus. Notably, alterations of mitochondrial function were detectable at saturating oxygen levels, indicating that cardiac mitochondrial insufficiency can occur prior to HF without oxygen limitation. Our data support the view that species distribution may be related to the thermal limits of mitochondrial stability and function, which will be important as oceans continue to warm.

Succinate promotes pulmonary fibrosis through GPR91 and predicts death in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is believed to be associated with a notable disruption of cellular energy metabolism. By detecting the changes of energy metabolites in the serum of patients with pulmonary fibrosis, we aimed to investigate the diagnostic and prognostic value of energy metabolites in IPF, and further elucidated the mechanism of their involvement in pulmonary fibrosis. Through metabolomics research, it was discovered that the TCA cycle intermediates changed dramatically in IPF patients. In another validation cohort of 55 patients with IPF compared to 19 healthy controls, it was found that succinate, an intermediate product of TCA cycle, has diagnostic and prognostic value in IPF. The cut-off levels of serum succinate were 98.36 µM for distinguishing IPF from healthy controls (sensitivity, 83.64%; specificity, 63.16%; likelihood ratio, 2.27, respectively). Moreover, a high serum succinate level was independently associated with higher rates of disease progression (OR 13.087, 95%CI (2.819-60.761)) and mortality (HR 3.418, 95% CI (1.308-8.927)). In addition, accumulation of succinate and increased expression of the succinate receptor GPR91 were found in both IPF patients and BLM mouse models of pulmonary fibrosis. Reducing succinate accumulation in BLM mice alleviated pulmonary fibrosis and 21d mortality, while exogenous administration of succinate can aggravate pulmonary fibrosis in BLM mice. Furthermore, GPR91 deficiency protected against lung fibrosis caused by BLM. In vitro, succinate promoted the activation of lung fibroblasts by activating ERK pathway through GPR91. In summary, succinate is a promising biomarker for diagnosis and prognosis of IPF. The accumulation of succinate may promote fibroblast activation through GPR91 and pulmonary fibrosis.

Metabolomics-based search for lung cancer markers among patients with different smoking status.

Tobacco smoking is the main etiological factor of lung cancer (LC), which can also cause metabolome disruption. This study aimed to investigate whether the observed metabolic shift in LC patients was also associated with their smoking status. Untargeted metabolomics profiling was applied for the initial screening of changes in serum metabolic profile between LC and chronic obstructive pulmonary disease (COPD) patients, selected as a non-cancer group. Differences in metabolite profiles between current and former smokers were also tested. Then, targeted metabolomics methods were applied to verify and validate the proposed LC biomarkers. For untargeted metabolomics, a single extraction-dual separation workflow was applied. The samples were analyzed using a liquid chromatograph-high resolution quadrupole time-of-flight mass spectrometer. Next, the selected metabolites were quantified using liquid chromatography-triple-quadrupole mass spectrometry. The acquired data confirmed that patients' stratification based on smoking status impacted the discriminating ability of the identified LC marker candidates. Analyzing a validation set of samples enabled us to determine if the putative LC markers were truly robust. It demonstrated significant differences in the case of four metabolites: allantoin, glutamic acid, succinic acid, and sphingosine-1-phosphate. Our research showed that studying the influence of strong environmental factors, such as tobacco smoking, should be considered in cancer marker research since it reduces the risk of false positives and improves understanding of the metabolite shifts in cancer patients.

1H NMR derived metabolomic profile of neonatal asphyxia in umbilical cord serum: implications for hypoxic ischemic encephalopathy.

Neonatal hypoxic ischemic encephalopathy (HIE) is a severe consequence of perinatal asphyxia (PA) that can result in life-long neurological disability. Disease mechanisms, including the role and interaction of individual metabolic pathways, remain unclear. As hypoxia is an acute condition, aerobic energy metabolism is central to global metabolic pathways, and these metabolites are detectable using 1H NMR spectroscopy, we hypothesized that characterizing the NMR-derived umbilical cord serum metabolome would offer insight into the consequences of PA that lead to HIE. Fifty-nine at-risk infants were enrolled, together with 1:1 matched healthy controls, and stratified by disease severity (n=25, HIE; n=34, non-HIE PA). Eighteen of 37 reproducibly detectable metabolites were significantly altered between study groups. Acetone, 3-hydroxybutyrate, succinate, and glycerol were significantly differentially altered in severe HIE. Multivariate data analysis revealed a metabolite profile associated with both asphyxia and HIE. Multiple-linear regression modeling using 4 metabolites (3-hydroxybutyrate, glycerol, O-phosphocholine, and succinate) predicted HIE severity with an adjusted R2 of 0.4. Altered ketones suggest that systemic metabolism may play a critical role in preventing neurological injury, while altered succinate provides a possible explanation for hypoxia-inducible factor 1-α (HIF-1α) stabilization in HI injury.

Preclinical pharmacokinetic analysis of armillarisin succinate ester in mouse plasma and tissues by LC-MS/MS.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed and validated to determine the concentration of armillarisin succinate ester in mouse plasma and tissues, used for preclinical evaluation. Bavachin was employed as the internal standard. Separation was performed on a 3.5 µm Zorbax SB-C(18) column (30 × 2.1 mm), with a mobile phase consisting of methanol and aqueous 20 mm ammonium acetate. Both analyte and internal standard were determined using electrospray ionization and the MS data acquisition was via selected ion monitoring in negative scanning mode. Quantification was performed using the transitions m/z 333 → 233 and 323 → 221 for armillarisin succinate ester and internal standard, respectively. The method was validated with respect to linearity, accuracy, precision, recovery and stability. This assay has been successfully applied to a pharmacokinetic and tissue distribution study after intravenous injection of ASE in mouse in a dose of 10 mg/kg.

Elevated plasma succinate in PTEN, SDHB, and SDHD mutation-positive individuals.

PURPOSE: Cowden syndrome results from germline mutations in the gene for phosphatase and tensin homologue deleted on chromosome 10 (PTEN) and from variants in succinate dehydrogenase B and D subunits. We hypothesized that succinate accumulation may be common among individuals with SDH variants/mutations and those with PTEN mutations. METHODS: Urine and blood were collected from individuals meeting full or partial Cowden syndrome diagnostic criteria or those with paraganglioma (PGL) or a known susceptibility paraganglioma-associated gene mutation, and succinate was measured. PTEN, SDHB, SDHC, and SDHD genes were sequenced from genomic DNA. RESULTS: Elevated plasma succinate was observed in 13/21 (62%) individuals with germline PTEN, SDHB, or SDHD mutations as compared with 5/32 (16%) controls (P < 0.001), in 10/15 (67%) individuals with pathogenic PTEN mutations but in <20% of mutation-negative individuals meeting identical criteria, and in individuals with mutations in SDHB (1/1, 100%) and SDHD (2/5, 40%). CONCLUSION: Our data suggest that mutations in PTEN, SDHB, and SDHD reduce catalytic activity of succinate dehydrogenase, resulting in succinate accumulation, and identify a common biochemical alteration in these two patient populations (PTEN and SDHx mutation positive individuals). Plasma organic acid analysis may provide an effective and inexpensive screening method to determine when more expensive gene sequencing of PTEN and SDH genes is warranted.

[Intestinal absorption of enteric coating potassium sodium dehydroandroan drographolide succinate pellets in rat and in vivo pharmacokinetics study].

OBJECTIVE: To develop a method for determination the content of Potassium Sodium Dehydroandroan drographolide Succinate (PSDS) in rat intestinal contents and plasma and investigate the intestinal absorption of PSDS pellets in rat and in vivo pharmacokinetics of PSDS pellets. METHODS: The content of PSDS in rat intestinal contents and plasma was determined by HPLC. In vivo pharmacokinetic properties and intestinal absorption of PSDS pellets in rat were investigated. RESULTS: Two hours after administration, pellets were not found in the small intestine and large intestine, four hours after administration, the largest number of pellets were found in the small intestine and the concentration of PSDS was the highest in the intestinal contents (3593.13 microg). The characteristics of plasma concentration-time curve was consistent with a single compartment model. The main drug pharmacokinetic parameters were calculated. t1/2, T(max), C(max) and AUC were 2.69 h, 5 h, 3.02 microg/mL and 6.42 microg x h/mL, respectively. CONCLUSION: PSDS has a good absorption in the rat small intestine and it is feasible to prepare PSDS enteric-coated pellets for oral administration.

Tricarboxylic acid cycle related-metabolites and risk of atrial fibrillation and heart failure.

BACKGROUND: Tricarboxylic acid (TCA) cycle deregulation may predispose to cardiovascular diseases, but the role of TCA cycle-related metabolites in the development of atrial fibrillation (AF) and heart failure (HF) remains unexplored. This study sought to investigate the association of TCA cycle-related metabolites with risk of AF and HF. METHODS: We used two nested case-control studies within the PREDIMED study. During a mean follow-up for about 10 years, 512 AF and 334 HF incident cases matched by age (±5 years), sex and recruitment center to 616 controls and 433 controls, respectively, were included in this study. Baseline plasma levels of citrate, aconitate, isocitrate, succinate, malate and d/l-2-hydroxyglutarate were measured with liquid chromatography-tandem mass spectrometry. Multivariable conditional logistic regression models were fitted to estimate odds ratios (OR) and 95% confidence intervals (95% CI) for metabolites and the risk of AF or HF. Potential confounders included smoking, family history of premature coronary heart disease, physical activity, alcohol intake, body mass index, intervention groups, dyslipidemia, hypertension, type 2 diabetes and medication use. RESULTS: Comparing extreme quartiles of metabolites, elevated levels of succinate, malate, citrate and d/l-2-hydroxyglutarate were associated with a higher risk of AF [ORQ4 vs. Q1 (95% CI): 1.80 (1.21-2.67), 2.13 (1.45-3.13), 1.87 (1.25-2.81) and 1.95 (1.31-2.90), respectively]. One SD increase in aconitate was directly associated with AF risk [OR (95% CI): 1.16 (1.01-1.34)]. The corresponding ORs (95% CI) for HF comparing extreme quartiles of malate, aconitate, isocitrate and d/l-2-hydroxyglutarate were 2.15 (1.29-3.56), 2.16 (1.25-3.72), 2.63 (1.56-4.44) and 1.82 (1.10-3.04), respectively. These associations were confirmed in an internal validation, except for aconitate and AF. CONCLUSION: These findings underscore the potential role of the TCA cycle in the pathogenesis of cardiac outcomes.

A transepithelial pathway delivers succinate to macrophages, thus perpetuating their pro-inflammatory metabolic state.

The gut metabolite composition determined by the microbiota has paramount impact on gastrointestinal physiology. However, the role that bacterial metabolites play in communicating with host cells during inflammatory diseases is poorly understood. Here, we aim to identify the microbiota-determined output of the pro-inflammatory metabolite, succinate, and to elucidate the pathways that control transepithelial succinate absorption and subsequent succinate delivery to macrophages. We show a significant increase of succinate uptake into pro-inflammatory macrophages, which is controlled by Na+-dependent succinate transporters in macrophages and epithelial cells. Furthermore, we find that fecal and serum succinate concentrations were markedly augmented in inflammatory bowel diseases (IBDs) and corresponded to changes in succinate-metabolizing gut bacteria. Together, our results describe a succinate production and transport pathway that controls the absorption of succinate generated by distinct gut bacteria and its delivery into macrophages. In IBD, this mechanism fails to protect against the succinate surge, which may result in chronic inflammation.

Plasma methionine metabolic profile is associated with longevity in mammals.

Methionine metabolism arises as a key target to elucidate the molecular adaptations underlying animal longevity due to the negative association between longevity and methionine content. The present study follows a comparative approach to analyse plasma methionine metabolic profile using a LC-MS/MS platform from 11 mammalian species with a longevity ranging from 3.5 to 120 years. Our findings demonstrate the existence of a species-specific plasma profile for methionine metabolism associated with longevity characterised by: i) reduced methionine, cystathionine and choline; ii) increased non-polar amino acids; iii) reduced succinate and malate; and iv) increased carnitine. Our results support the existence of plasma longevity features that might respond to an optimised energetic metabolism and intracellular structures found in long-lived species.