The blood serum metabolome profile after different phases of a 4-km cycling time trial: Secondary analysis of a randomized controlled trial.

It has been assumed that exercise intensity variation throughout a cycling time trial (TT) occurs in alignment of various metabolic changes to prevent premature task failure. However, this assumption is based on target metabolite responses, which limits our understanding of the complex interconnection of metabolic responses during exercise. The current study characterized the metabolomic profile, an untargeted metabolic analysis, after specific phases of a cycling 4-km TT. Eleven male cyclists performed three separated TTs in a crossover counterbalanced design, which were interrupted at the end of the fast-start (FS, 600 ± 205 m), even-pace (EP, 3600 ± 190 m), or end-spurt (ES, 4000 m) phases. Blood samples were taken before any exercise and 5 min after exercise cessation, and the metabolomic profile characterization was performed using Nuclear Magnetic Resonance metabolomics. Power output (PO) was also continually recorded. There were higher PO values during the FS and ES compared to the EP (all p < 0.05), which were accompanied by distinct metabolomic profiles. FS showed high metabolite expression in TCA cycle and its related pathways (e.g., glutamate, citric acid, and valine metabolism); whereas, the EP elicited changes associated with antioxidant effects and oxygen delivery adjustment. Finally, ES was related to pathways involved in NAD turnover and serotonin metabolism. These findings suggest that the specific phases of a cycling TT are accompanied by distinct metabolomic profiles, providing novel insights regarding the relevance of specific metabolic pathways on the process of exercise intensity regulation.

Vitamin K Effects on Gas6 and Soluble Axl Receptors in Intensive Care Patients: An Observational Screening Study.

Growth arrest-specific gene 6 protein (Gas6) is avitamin K-dependent tissue bound protein. Gas6 has been shown to promote growth and therapy resistance among different types of cancer as well as thromboembolism. The aim of this prospective screening study: ClinicalTrials.gov; Identifier: NTC3782025, was to evaluate the effects of intravenously administered vitamin K1 on Gas6 and its soluble (s)Axl receptor plasma levels in intensive care patients. Vitamin K1 was intravenously injected in non-warfarin treated patients with prolonged Owren prothrombin time international normalized ratio (PT-INR) > 1.2 and blood samples were retrieved before and 20-28 h after injection. Citrate plasma samples from 52 intensive care patients were analysed for different vitamin K dependent proteins. There was a significant, but small increase in median Gas6. Only one patient had a large increase in sAxl, but overall, no significant changes in sAxl Gas6 did not correlate to PT-INR, thrombin generation assay, coagulation factors II, VII, IX and X, but to protein S and decarboxylated matrix Gla protein (dp-ucMGP). In conclusion, there was a small increase in Gas6 over 20-28 h. The pathophysiology and clinical importance of this remains to be investigated. To verify a true vitamin K effect, improvement of Gas6 carboxylation defects needs to be studied.

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.

Changes in Circulating Metabolites During Weight Loss are Associated with Adiposity Improvement, and Body Weight and Adiposity Regain During Weight Loss Maintenance: The SATIN Study.

SCOPE: To examine the relationship between changes in circulating metabolites during diet-induced weight loss and changes of adiposity. This study also investigates changes in these metabolites in relation to body weight and adiposity regain during a weight loss maintenance period. METHODS AND RESULTS: This cohort study is nested within the Satiety Innovation (SATIN) study. Participants (n = 162) achieving ≥8% weight loss during an initial 8-week low-calorie formula diet (LCD) are included in a 12-week weight loss maintenance period. A targeted metabolite profiling (123 metabolites) approach is applied using three different platforms (proton nuclear magnetic resonance, liquid chromatography mass spectrometry, gas chromatography mass spectrometry). Changes in several lipid species and citric acid are significantly associated with greater reduction of body weight, total fat, and abdominal adiposity distribution during the LCD. Decreases in the concentrations of lysophosphatidylcholines (LPCs) 14:0, LPC 20:3, phosphatidylcholine (PC) 32:2, PC 38:3, sphingomyelin (SM) 32:2, and increases in citric acid concentrations during the LCD are associated with adiposity regain and loss, respectively, during the weight loss maintenance period. CONCLUSIONS: The results show that weight loss is associated with changes in lipid species and citric acid. These changes are related to subsequent weight and adiposity regain identifying the adipose lipid metabolism as an important factor for the maintenance of lost weight and adiposity.

UPLC-Q-TOF/MS-based plasma metabolome to identify biomarkers and time of injury in traumatic brain injured rats.

BACKGROUND: To identify the potent metabolic biomarkers and time of injury of traumatic brain injured (TBI). METHODS: A total of 70 Sprague-Dawley rats were used to establish the TBI model in this study. The serum was collected at 3 h, 6 h, 12 h, 24 h, 3 days and 7 days after surgery. Ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was performed to analyze metabolic changes in the serum of the TBI rats from different groups. The differences between the metabolic profiles of the rats in seven groups were analyzed using partial least squares discriminant analysis. RESULTS: Metabolic profiling revealed significant differences between the sham-operated and other groups. A total of 49 potential TBI metabolite biomarkers were identified between the sham-operated group and the model groups at different time points. Among them, six metabolites (methionine sulfone, kynurenine, 3-hydroxyanthranilic acid, 3-Indolepropionic acid, citric acid and glycocholic acid) were identified as biomarkers of TBI to estimate the injury time. CONCLUSION: Using metabolomic analysis, we identified new TBI serum biomarkers for accurate detection and determination of the timing of TBI injury.

Effects of sevoflurane anesthesia and abdominal surgery on the systemic metabolome: a prospective observational study.

BACKGROUND: Metabolic status can be impacted by general anesthesia and surgery. However, the exact effects of general anesthesia and surgery on systemic metabolome remain unclear, which might contribute to postoperative outcomes. METHODS: Five hundred patients who underwent abdominal surgery were included. General anesthesia was mainly maintained with sevoflurane. The end-tidal sevoflurane concentration (ETsevo) was adjusted to maintain BIS (Bispectral index) value between 40 and 60. The mean ETsevo from 20 min after endotracheal intubation to 2 h after the beginning of surgery was calculated for each patient. The patients were further divided into low ETsevo group (mean - SD) and high ETsevo group (mean + SD) to investigate the possible metabolic changes relevant to the amount of sevoflurane exposure. RESULTS: The mean ETsevo of the 500 patients was 1.60% ± 0.34%. Patients with low ETsevo (n = 55) and high ETsevo (n = 59) were selected for metabolomic analysis (1.06% ± 0.13% vs. 2.17% ± 0.16%, P < 0.001). Sevoflurane and abdominal surgery disturbed the tricarboxylic acid cycle as identified by increased citrate and cis-aconitate levels and impacted glycometabolism as identified by increased sucrose and D-glucose levels in these 114 patients. Glutamate metabolism was also impacted by sevoflurane and abdominal surgery in all the patients. In the patients with high ETsevo, levels of L-glutamine, pyroglutamic acid, sphinganine and L-selenocysteine after sevoflurane anesthesia and abdominal surgery were significantly higher than those of the patients with low ETsevo, suggesting that these metabolic changes might be relevant to the amount of sevoflurane exposure. CONCLUSIONS: Sevoflurane anesthesia and abdominal surgery can impact principal metabolic pathways in clinical patients including tricarboxylic acid cycle, glycometabolism and glutamate metabolism. This study may provide a resource data for future studies about metabolism relevant to general anaesthesia and surgeries. TRIAL REGISTRATION: www.chictr.org.cn . identifier: ChiCTR1800014327 .

Modulation of the gut microbiota by probiotics and symbiotics is associated with changes in serum metabolite profile related to a decrease in inflammation and overall benefits to metabolic health: a double-blind randomized controlled clinical trial in women with obesity.

Modulation of the gut microbiota may help in treating obesity by improving host metabolic health. We aimed to evaluate the effects of probiotics or symbiotics on body weight and serum metabolite profile in women with obesity. A double-blind, parallel, randomized, controlled clinical trial was conducted with 32 adult women with body mass index ranging from 30 to 34.9 kg m-2. Volunteers followed a low-energy diet and were subjected to 8 weeks intervention: probiotic group (PG - Bifidobacterium lactis UBBLa-70, n = 10), symbiotic group (SG - Bifidobacterium lactis UBBLa-70 and fructooligosaccharide, n = 11), or control group (CG - placebo, n = 11). Analyses of anthropometric variables, gut microbiota and serum metabolites by 1H nuclear magnetic resonance (NMR) were performed at baseline and after the intervention. Multivariate statistics showed that all groups presented a decrease in glycerol and increase in arginine, glutamine and 2-oxoisovalerate. Therefore, a low-energy diet per se promoted changes in the metabolite profile related to decreased inflammation and positive effects on body weight. SG presented unique changes in metabolites (increase in pyruvate and alanine and decrease in citrate and BCAA). Negative correlations between arginine and glutamine with fat mass were observed in the SG. PG presented a decrease in 1H NMR lipid signals and negative correlation between Verrucomicrobia and Firmicutes with (CH2)n lipids. Both probiotics and symbiotics promoted changes in metabolites related to improved metabolic health. Specific metabolite changes following symbiotic intervention might suggest some advantage in providing Bifidobacterium lactis in combination with fructooligosaccharide in a low-energy diet, rather than probiotics or diet alone. Clinical trial: NCT02505854.

Measurement of the Concentration of Citrate in Human Biofluids in Patients Undergoing Continuous Renal Replacement Therapy Using Regional Citrate Anticoagulation: Application of a Two-Step Enzymatic Assay.

BACKGROUND: Continuous renal replacement therapy (CRRT) with regional citrate anticoagulation (RCA) is now commonly used to treat acute kidney injury in critically ill patients. The concentration of citrate is not routinely measured, with citrate accumulation and/or toxicity primarily assessed using surrogate measures. OBJECTIVES: The aim of this study was to measure the concentration of citrate in plasma and ultrafiltrate in patients receiving CRRT with RCA using a modified commercial enzymatic assay. METHODS: After meeting inclusion criteria, blood was sampled from 20 patients before, during, and after episodes of filtration. Using spectrophotometry, samples were tested for citrate concentration. Demographic and other clinical and biochemical data were also collected. Throughout, a 15 mmol/L solution of trisodium citrate was used as the prefilter anticoagulant. Results were analysed using STATA (v15.0) and presented as mean (SD), median (IQR), or simple proportion. Comparisons were made using either the Student t test or the Wilcoxon rank-sum test. Correlation was assessed using Pearson's r. RESULTS: Twenty patients (17 males) were enrolled in the study. Mean (SD) age was 63.7 years (9.9). Median (IQR) ICU length of stay was 281 h (199, 422) with 85% undergoing intermittent positive pressure ventilation. Median APACHE 3 score was 95 (87, 117) with an overall 30% mortality rate. Median filtration time was 85 h (46, 149). No difference was found between pre- and post-filtration plasma citrate concentrations (79 µmol/L [50] vs. 71 µmol/L [42], p = 0.65). Mean citrate concentration during filtration was 508 µmol/L (221) with a maximum of 1,070 µmol/L. This was significantly higher than the pre/post levels (p < 0.001). CONCLUSIONS: Plasma concentrations of citrate rose significantly during episodes of CRRT using RCA returning back to normal after cessation of treatment.

Metabolomics of the diabetic nephropathy: behind the fingerprint of development and progression indicators. / Metabolómica de la nefropatía diabética: tras la huella de indicadores de desarrollo y progresión.

Current diagnostic methods are not very sensitive to detect the initial stages diabetic nephropathy of type 2. In this work, a review of metabolomic approximation studies for the identification of biomarkers of this disease with potential to differentiate between early stages, evaluate and direct treatment and help slow kidney damage. Using public (Pubmed and Google Scholar) and private (Scopus and Web of Knowledge) databases, a systematic search of the information published related to metabolomics of diabetic nephropathy in different biospecimens (urine, serum, plasma and blood) was made. Later, the MetaboAnalyst 4.0 software was used to identify the metabolic pathways associated with these metabolites. Groups of potential metabolites were identified for monitoring diabetic nephropathy with the available literature data. In the urine, oxide-3-hydroxyisovalerate, TMAO, aconite and citrate and hydroxypropionate derivatives are highlighted; meanwhile, in the serum: citrate, creatinine, arginine and its derivatives; and in the plasma: amino acids such as histidine, methionine and arginine has a potential contribution. Using MetaboAnalyst 4.0 the metabolic pathways related to these metabolites were related. The search for biomarkers to measure the progression of diabetic nephropathy, together with analytical strategies for their detection and quantification, are the starting point for designing new methods of clinical chemistry analysis. The association between the metabolic pathway dysfunction could be useful for the overall assessment of the treatment and clinical follow-up of this disease.

Determinants of Total/ionized Calcium in patients undergoing citrate CVVH: A retrospective observational study.

PURPOSE: To identify potential determinants of the Total/ionized Ca ratio (T/iCa), a marker of citrate accumulation. MATERIALS AND METHODS: Single-center retrospective observational study evaluating citrate dose, citrate target, albumin, phosphate, pH, lactate, and APACHE II score as potential determinants. Linear mixed models (LMM) using citrate dose and citrate target were developed describing associations with T/iCa. RESULTS: From a dataset of 471 samples in 103 patients, an LMM in 379 complete samples (95 patients) sets revealed that citrate dose, pH, phosphate, albumin and APACHE were interactively related to T/iCa. A rising citrate dose was associated with a higher increase in T/iCa when phosphate was high, and less when phosphate was low. A rising albumin was associated with a higher increase in T/iCa when APACHE was high and phosphate was low and less when APACHE was low and phosphate high. In case of acidosis, a rising lactate was associated with a higher increase in T/iCa. In the LMM using citrate target, citrate target and pH were the main independent predictors of T/iCa with albumin, phosphate and APACHE score as modifiers. CONCLUSIONS: Besides citrate dose, a high pH and high phosphate, albumin and APACHE are also associated with a rising T/iCa.

Dark brown serum and plasma samples: a case report.

This case report describes occurrence of unusual, dark brown coloration of citrate plasma and serum samples in a female 68 years old patient admitted into Emergency department (ED). Patient complained of nausea and vomiting, fever up to 38.9°C, colicky pain in abdomen, diminished urinary output and yellowish skin tone. Her medical history included arterial hypertension, hypothyroidism and facial squamous cell carcinoma. For previous two years, she was treated with tuberculostatic therapy for Mycobacterium avium positive interstitial lung disease. Regular follow-up showed no signs of active disease. Upon admission to ED, complete blood count (CBC) analysis showed low red blood count (RBC) (3.76 x1012/L (reference interval (RI) 3.86 - 5.08 x1012/L)), low haemoglobin (Hb) concentration (111 g/L (RI 119 - 157 g/L)) and low haematocrit (Hct) (0.310 L/L (RI 0.360 - 0.470 L/L)). Biochemistry analytes were high, with foremost lactate dehydrogenase (LD) activity (2900 U/L, RI < 240 U/L). After communication with the clinician, methaemoglobin measured in arterial blood gas sample was reported. Patient was admitted to the Intensive care unit and upon reflex testing of haptoglobin, intravascular haemolysis was confirmed. This case indicates that every case of brown coloration of the serum must be promptly communicated to the clinician. Reflex testing assured timely diagnosis and favourable patient outcome.

Effects of organic acids and common household products on the occurrence of false positive test results using immunochromatographic assays.

Forensic serological analyses often rely on lateral flow immunochromatographic assays to detect proteins that are characteristic of forensically relevant body fluids. In this study, we demonstrate that a positive result, however, is not limited to target protein binding. Citric and lactic acids at various pH levels were tested using 9 different commercial immunochromatographic assays. Varying rates of false positive results were observed with commercial serological assays irrespective of brand or target biological fluid over a wide pH range. The use of kit specific buffers were only partially effective in mitigating the occurrence of organic acid-associated false positive results. Common household products containing organic acids were also tested and found to produce non-specific binding events. This is not to suggest that immunochromatographic assays are not useful as presumptive indicators of bodily fluids. Rather, this study provides a cautionary demonstration of the ease with which organic acids in common household products can generate false positives results. This finding underscores the presumptive nature of these antibody-based lateral flow assay systems.

Associations of serum citrate levels with knee structural changes and cartilage enzymes in patients with knee osteoarthritis.

OBJECTIVE: The aim of this study was to investigate cross-sectional associations between serum levels of citrate and knee structural changes and cartilage enzymes in patients with knee osteoarthritis (OA). METHOD: A total of 137 subjects with symptomatic knee OA (mean age 55.0 years, range 34-74, 84% female) were included. Knee radiography was used to assess knee osteophytes, joint space narrowing (JSN) and radiographic OA assessed by Kellgren-Lawrence (K-L) grading system. T2-weighted fat-suppressed fast spin echo magnetic resonance imaging (MRI) was used to determine knee cartilage defects, bone marrow lesions (BMLs) and infrapatellar fat pad (IPFP) signal intensity alternations. Colorimetric fluorescence was used to measure the serum levels of citrate. Enzyme-linked immunosorbent assay was used to measure the serum cartilage enzymes including matrix metalloproteinase (MMP)-3 and MMP-13. RESULTS: After adjustment for potential confounders (age, sex, body mass index), serum citrate was negatively associated with knee osteophytes at the femoral site, cartilage defects at medial femoral site, total cartilage defects, and total BMLs (odds ratio [OR] 0.17-0.30, all P < .05). Meanwhile, serum citrate was negatively associated with IPFP signal intensity alteration (OR 0.30, P = .05) in multivariable analyses. Serum citrate was significantly and negatively associated with MMP-13 (ß -3106.37, P < .05) after adjustment for potential confounders. However, citrate was not significantly associated with MMP-3 in patients with knee OA. CONCLUSION: Serum citrate was negatively associated with knee structural changes including femoral osteophytes, cartilage defects, and BMLs and also serum MMP-13 in patients with knee OA, suggesting that low serum citrate may be a potential indicator for advanced knee OA.

Metabolomics analysis in adults with high bone mass identifies a relationship between bone resorption and circulating citrate which replicates in the general population.

OBJECTIVE: Bone turnover, which regulates bone mass, may exert metabolic consequences, particularly on markers of glucose metabolism and adiposity. To better understand these relationships, we examined cross-sectional associations between bone turnover markers (BTMs) and metabolic traits in a population with high bone mass (HBM, BMD Z-score ≥+3.2). DESIGN: ß-C-terminal telopeptide of type-I collagen (ß-CTX), procollagen type-1 amino-terminal propeptide (P1NP) and osteocalcin were assessed by electrochemiluminescence immunoassays. Metabolic traits, including lipids and glycolysis-related metabolites, were measured using nuclear magnetic resonance spectroscopy. Associations of BTMs with metabolic traits were assessed using generalized estimating equation linear regression, accounting for within-family correlation, adjusting for potential confounders (age, sex, height, weight, menopause, bisphosphonate and oral glucocorticoid use). RESULTS: A total of 198 adults with HBM had complete data, mean [SD] age 61.6 [13.7] years; 77% were female. Of 23 summary metabolic traits, citrate was positively related to all BTMs: adjusted ßß-CTX  = 0.050 (95% CI 0.024, 0.076), P = 1.71 × 10-4 , ßosteocalcin  = 6.54 × 10-4 (1.87 × 10-4 , 0.001), P = .006 and ßP1NP  = 2.40 × 10-4 (6.49 × 10-5 , 4.14 × 10-4 ), P = .007 (ß = increase in citrate (mmol/L) per 1 µg/L BTM increase). Inverse relationships of ß-CTX (ß = -0.276 [-0.434, -0.118], P = 6.03 × 10-4 ) and osteocalcin (-0.004 [-0.007, -0.001], P = .020) with triglycerides were also identified. We explored the generalizability of these associations in 3664 perimenopausal women (age 47.9 [4.4] years) from a UK family cohort. We confirmed a positive, albeit lower magnitude, association between ß-CTX and citrate (adjusted ßwomen  = 0.020 [0.013, 0.026], P = 1.95 × 10-9 ) and an inverse association of similar magnitude between ß-CTX and triglycerides (ß = -0.354 [-0.471, -0.237], P = 3.03 × 10-9 ). CONCLUSIONS: Bone resorption is positively related to circulating citrate and inversely related to triglycerides. Further studies are justified to determine whether plasma citrate or triglyceride concentrations are altered by factors known to modulate bone resorption, such as bisphosphonates.

Longitudinal study of kidney water management in patients diagnosed with idiopathic hypercalciuria in childhood. / Estudio longitudinal del manejo renal del agua en pacientes diagnosticados de hipercalciuria idiopática en la infancia.

INTRODUCTION: There is much debate about whether idiopathic hypercalciuria (IH) affects kidney water management. For the first time in the literature, we carried out a longitudinal study of kidney water management (KWM) in patients diagnosed with IH in childhood and followed-up until adulthood (mean follow-up 17.7±1.4 years). METHODS: Twenty-nine patients (7 M, 22 F) over the age of 24 years (mean 28.2±2.9 years, range: 24.1-35.9) who were diagnosed with IH in childhood (mean 7.6±3.2 years, range: 1-14) were included. Maximum urine osmolality (UO) and/or urine volume adjusted for 100ml of glomerular filtration rate (V/GFR) in both age groups (paediatric and adult) were determined. Moreover, whenever possible, in both age groups plasma creatinine levels, plasma sodium levels, uric acid levels, the citrate/creatinine ratio and the calcium/citrate ratio were recorded and a renal and bladder ultrasound was performed. RESULTS: In the paediatric age group, KWM was altered in 9/29 cases (31%) (4 with reduced maximum UO and 5 with elevated V/GFR). In adulthood, KWM was found to be affected in 7/29 cases (24.1%) (6 with reduced UO and one with elevated V/GFR). Compared to the paediatric age group, adult patients had lower V/GFR, calcium/creatinine and citrate/creatinine values, as well as higher plasma creatinine, uric acid and calcium/citrate. There were no differences in the maximum UO in both age groups. However, UO in adulthood was significantly lower in subjects who had renal colic compared to those who did not (P=.04). CONCLUSIONS: KWM was affected in approximately one third of patients with IH, which persisted 20 years after diagnosis. We think that these results may be due to adherence to the recommended protective diet and to the pharmacological treatment administered at the diagnosis of IH during childhood.

Regional citrate anticoagulation for continuous renal replacement therapy in newborns and infants: Focus on citrate accumulation.

Continuous renal replacement therapy (CRRT) with regional citrate anticoagulation (RCA) in newborns and infants is challenging and accumulation of citrate can occur. There are only a few studies reporting the detailed data on RCA. We aimed to analyze RCA-CRRT at our institution with focus on citrate accumulation. Critically ill newborns and infants up to 11 kg of body weight (BW), treated with RCA-CRRT in the 2011-2016 period were included in this retrospective observational study. Prismaflex(R) and Multifiltrate-CiCa(R) dialysis monitors were used with either automated or manual RCA. Data was collected regarding the circuit lifetime, parameters of RCA, markers of citrate accumulation (total/ionized calcium ratio > 2.5), and metabolic complications. We included 10 children with mean age of 2.6 ± 3.8 months and BW of 4.6 ± 2.7 kg. In-hospital mortality was 60%. RCA-CRRT parameters were: blood flow 46 ± 9 mL/min (12 ± 5 mL/min/kg BW), citrate dose 2.8 ± 0.6 mmol/L of blood resulting in estimated citrate load to the patient of 1.7 ± 0.8 mmol/h/kg BW. In total, 57 dialysis circuits were used with mean filter lifetime of 39 ± 29 h. Citrate accumulation (total/ionized calcium ratio > 2.5) was observed in 7/10 patients and in 14/57 (25%) of circuits; those circuits were performed in children with lower age and BW, had higher relative blood flow and citrate load, while citrate dose was similar. When citrate load to the patient was used to predict citrate accumulation, AUC under the ROC curve was 0.78 and 1.7 mmol/h/kg BW was considered the optimal cutoff value (sensitivity 71% and specificity 72%). CRRT with RCA using equipment, developed for adult population, is feasible in newborns and infants. Signs of citrate accumulation developed relatively often. To prevent it, we suggest avoiding citrate loads above 1.7 mmol/h/kg BW, which can best be achieved by keeping the blood flow below 9 mL/min/kg BW.

Citrate NMR peak irreproducibility in blood samples after reacquisition of spectra.

BACKGROUND: In our metabolomics studies we have noticed that repeated NMR acquisition on the same sample can result in altered metabolite signal intensities. AIMS: To investigate the reproducibility of repeated NMR acquisition on selected metabolites in serum and plasma from two large human metabolomics studies. METHODS: Two peak regions for each metabolite were integrated and changes occurring after reacquisition were correlated. RESULTS: Integral changes were generally small, but serum citrate signals decreased significantly in some samples. CONCLUSIONS: Several metabolite integrals were not reproducible in some of the repeated spectra. Following established protocols, randomising analysis order and biomarker validation are important.

Heparin and citrate additive carryover during blood collection.

Background Published evidence on the risk of additive carryover during phlebotomy remains elusive. We aimed to assess potential carryover of citrated and heparinized blood and the relative volume needed to bias clinical chemistry and coagulation tests. Methods We simulated standardized phlebotomies to quantify the risk of carryover of citrate and heparin additives in distilled water, using sodium and lithium as surrogates. We also investigated the effects of contamination of heparinized blood samples with increasing volumes of citrated blood and pure citrate on measurements of sodium, potassium, chloride, magnesium, total and ionized calcium and phosphate. Likewise, we studied the effects of contamination of citrated blood samples with increasing volumes of heparinized blood on heparin (anti-Xa) activity, lithium, activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT). We interpreted these results based on measurement deviations beyond analytical, biological and clinical significance. Results Standardized phlebotomy simulations revealed no significant differences in concentration of surrogate markers. Clinically significant alterations were observed after contamination of heparinized blood samples with volumes of citrated blood beyond 5-50 µL for ionized calcium and beyond 100-1000 µL for sodium, chloride and total calcium. Investigations of pure citrate carryover revealed similar results at somewhat lower volumes. Heparinized blood carryover showed clinically significant interference of coagulation testing at volumes beyond 5-100 µL. Conclusions Our results suggest that during a standardized phlebotomy, heparin or citrate contamination is highly unlikely. However, smaller volumes are sufficient to severely alter test results when deviating from phlebotomy guidelines.

Metabolite Exchange between Mammalian Organs Quantified in Pigs.

Mammalian organs continually exchange metabolites via circulation, but systems-level analysis of this shuttling process is lacking. Here, we compared, in fasted pigs, metabolite concentrations in arterial blood versus draining venous blood from 11 organs. Greater than 90% of metabolites showed arterial-venous differences across at least one organ. Surprisingly, the liver and kidneys released not only glucose but also amino acids, both of which were consumed primarily by the intestine and pancreas. The liver and kidneys exhibited additional unexpected activities: liver preferentially burned unsaturated over more atherogenic saturated fatty acids, whereas the kidneys were unique in burning circulating citrate and net oxidizing lactate to pyruvate, thereby contributing to circulating redox homeostasis. Furthermore, we observed more than 700 other cases of tissue-specific metabolite production or consumption, such as release of nucleotides by the spleen and TCA intermediates by pancreas. These data constitute a high-value resource, providing a quantitative atlas of inter-organ metabolite exchange.

Serum Concentrations of Citrate, Tyrosine, 2- and 3- Hydroxybutyrate are Associated with Increased 3-Month Mortality in Acute Heart Failure Patients.

Considering the already established relationship between the extent of the metabolic dysfunction and the severity of heart failure (HF), it is conceivable that the metabolomic profile of the serum may have a prognostic capacity for 3-month mortality in acute heart failure (AHF). Out of 152 recruited patients, 130 serum samples were subjected to the metabolomic analyses. The 3-month mortality rate was 24.6% (32 patients). Metabolomic profiling by nuclear magnetic resonance spectroscopy found that the serum levels of 2-hydroxybutyrate (2-HB), 3-hydoxybutyrate (3-HB), lactate, citrate, and tyrosine, were higher in patients who died within 3 months compared to those who were alive 3 months after onset of AHF, which was confirmed by univariable logistic regression analyses (p = 0.009, p = 0.005, p = 0.008, p<0.001, and p<0.001, respectively). These associations still remained significant for all tested metabolites except for lactate after adjusting for established prognostic parameters in HF. In conclusion, serum levels of 2-HB, 3-HB, tyrosine, and citrate measured at admission are associated with an increased 3-month mortality rate in AHF patients and might thus be of prognostic value in AHF.