Metabolite Concentrations In Patients Research Articles

Quantification of Thiopurine Metabolites in Human Erythrocytes by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

The thiopurine drugs, azathioprine, mercaptopurine, and thioguanine, are widely used in the treatment of several malignant and nonmalignant diseases. These inactive prodrugs undergo extensive metabolism to form active cytotoxic metabolites, which act mainly by incorporating into DNA and affecting cell replication. Thiopurine methyltransferase is a highly variable cytosolic enzyme that catalyzes the S-methylation of the thiopurine bases-an inactivating pathway. Patients with low-activity variants of TPMT can be affected by pronounced pharmacologic effects when receiving thiopurine medications. Clinical studies have reported significant interpatient variability in intracellular thiopurine metabolite concentrations in patients receiving thiopurine therapy. In this chapter, we present an LC-MS/MS method to monitor the thiopurine metabolites: 6-thioguanine nucleotides and 6-methylmercaptopurine derivatives in human erythrocytes. This method utilizes acid hydrolysis to release the bases and improves upon previously published procedures by utilizing stable isotope internal standards and a more efficient chromatographic separation.

BIOM-14. INCREASED RATIO OF GLUTAMATE TO TOTAL CREATINE IN GLIOBLASTOMA PATIENTS WITH THE POST-OPERATIVE EPILEPSY

Abstract Epilepsy in glioblastoma patients significantly reduces their quality of life; however, little is known about the association between predicting epilepsy and metabolites in tumors. In this study, we used 3.0-T magnetic resonance imaging (MRI) and 1H-magnetic resonance spectroscopy (MRS) to quantify metabolite concentrations in patients with varying epilepsy histories. MRS data were quantified with linear combination model (LC-Model) software. From January 2013 to April 2020, fifty-one patients with primary glioblastoma underwent pretreatment 3.0-T MRI/1H-MRS scanning. Twenty-one patients (41%) suffered from epilepsy during the postoperative course, although forty-seven patients (97%) took anti-epileptic drug after surgery. MRS data were compared between groups with and without the post-operative epilepsy. The higher ratios of glutamate (Glu) and glutamate + glutamine (Glx) to total creatine (tCr) in the tumor were significantly associated with epilepsy history (Glu/tCr P < 0.001, Glx/tCr P = 0.004, respectively). The receiver operating characteristic curve analysis showed that a Glu/tCr value of 1.81 was 70% sensitive and 90% specific for the prediction of epilepsy during the postoperative course (area under curve: 0.82). These results suggest that the Glu/tCr ratio in tumors can be a predictive maker for early detection of epileptic seizures after surgery in glioblastoma patients.

Impaired kynurenine metabolism in patients with primary Sjögren’s syndrome

ObjectivesPrimary Sjögren’s syndrome (pSS) is an autoinflammatory disease characterized by inflammation of the exocrine glands. Elevated inflammation causes an increase in kynurenine pathway (KP) metabolite levels by activating indoleamine 2,3-dioxygenase (IDO). The aim of this study was to measure serum KP metabolite concentrations in patients with pSS and to evaluate the relationship between these metabolites with disease activity score and clinical manifestations. Design & MethodsA total of 80 patients with pSS and 80 healthy controls were enrolled in this study. Serum tryptophan (TRP), kynurenine (KYN), kynurenic acid (KYNA), 3-hydroxyanthranilic acid (3HAA), 3-hydroxykynurenine (3HK), quinolinic acid (QUIN) concentrations were quantified with liquid chromatography with tandem mass spectrometry (LC-MS/MS). Demographic characteristics, clinical manifestations and disease activity score (ESSDAI) of the participants were recorded. ResultsThe serum level of KYN and QUIN were significantly higher in patients with pSS with low and moderate activity compared those healthy controls, while the serum level of TRP, KYNA/KYN and 3HK/KYN were lower. In addition, the significant difference for the serum level of KYNA was only in patients with moderate activity from healthy controls, and the difference was higher in favor of pSS patients. Moreover, the KYN/TRP levels were significantly increased with disease activity. The ESSDAI score was positively correlated with KYN/TRP ratio, but negatively correlated with KYNA/KYN ratio. ConclusionsThese findings indicated that KP metabolites may play a role in the etiopathogenesis, activation and progression of pSS.

Glutamic Acid and Total Creatine as Predictive Markers for Epilepsy in Glioblastoma by Using Magnetic Resonance Spectroscopy Before Surgery

Epilepsy in glioblastoma patients significantly reduces their quality of life; however, little is known about the association between predicting epilepsy and metabolites in tumors. In this study, we used 3.0-T magnetic resonance imaging and 1H-magnetic resonance spectroscopy (MRS) to quantify metabolite concentrations in patients with varying epilepsy histories. Fifty-one patients with glioblastoma underwent pretreatment 3.0-T MRI/1H-MRS scanning. Single-voxel (1.5 cm3) MRS, in an enhanced lesion, was acquired using adouble-echo point-resolved spectroscopic sequence with chemical-shift selective water suppression. MRS data were quantified with linear combination model (LC-Model) software. We compared the MRS data between groups withand without epilepsy during the postoperative course(EP). The ratios of glutamate (Glu) and glutamate+ glutamine (Glx) to total creatine (Glu/tCr and Glx/tCr) in the tumor were associated with epilepsy history. The receiver operating characteristic curve analysis showed that a Glu/tCr value of 1.81 was 70% sensitive and 90% specific for the prediction of EP (area under curve: 0.82). In the analysis excluding patients with preoperative epilepsy, a Glu/tCr value of 1.81 was 75% sensitive and 88% specific for the prediction (area under curve: 0.87). Intratumoral metabolite concentrations measured using pretreatment 3.0-T MRI/1H-MRS changed characteristically in the group with EP. Our study suggests that the Glu/tCr ratio in tumors has adequate reliability in predicting EP. Pretreatment MRS is a minimally invasive and simple procedure that can provide useful information on glioblastoma patients.

FC 060METABOLIC PROFILING AS A MARKER OF CARDIOVASCULAR DISEASE AND ARTERIAL CALCIFICATION IN THE COPENHAGEN CHRONIC KIDNEY DISEASE COHORT

Abstract Background and Aims The relation between chronic kidney disease and adverse cardiovascular events is well-established. It is also known that traditional risk factors of cardiovascular disease such as smoking, low-density lipoprotein (LDL) cholesterol and increased blood pressure, cannot fully explain the increased cardiovascular burden observed in patients with chronic kidney disease. In addition, patients with chronic kidney disease do not demonstrate typical clinical symptoms of cardiovascular disease. Thus, good biomarkers for identifying patients at risk and a better understanding of the pathophysiology leading to cardiovascular disease in patients with chronic kidney disease are needed. The objective of the present study was to investigate associations between plasma metabolites and prevalent cardiovascular disease, as well as subclinical cardiovascular disease measured as coronary artery calcification score (CACS), in patients with chronic kidney disease. Method More than 200 metabolic biomarkers, including subclasses of lipoproteins as well as the lipid composition of these, were quantified using nuclear magnetic resonance spectroscopy in 725 patients and 174 controls from the Copenhagen Chronic Kidney Disease Cohort, a single-centre prospective, observational study of non-dialysis patients with stage 1-5 chronic kidney disease. Associations between metabolites and prevalent cardiovascular disease and between metabolites and CACS were determined using multivariable logistic regression and linear regression, respectively. The statistical models were adjusted for traditional cardiovascular risk factors and multiple testing. CACS was determined by CT-scannning and calcium scores were subsequently divided into categories of 0 (no calcification), 1-100, 101-400 and > 400. Results When comparing metabolite concentrations in patients with controls, patients presented with the expected pattern of dyslipidaemia in CKD. We found that they had increased plasma triglyceride concentrations, mainly due to an increase in the triglyceride concentration in very low-density lipoprotein (VLDL) particles, while the concentration of cholesterol in high-density lipoprotein (HDL) particles was decreased. Overall, 85 metabolites were significantly associated with prevalent cardiovascular disease in a model adjusted for eGFR, age and sex (p < 0.001). After further adjusting for diabetes, body mass index, smoking and cholesterol-lowering medication, the significance was lost for all but six metabolites (p < 0.001). The consistent inverse associations with metabolites were primarily involved in HDL metabolism (e.g. ApoA-1, HDL-C and HDL-2). This also applied to the concentration of total lipids in large HDL particles, the concentration of phospholipids in large HDL particles and the the ratio of phospholipids to total lipids in very small VLDL particles. Of the 84 metabolites associated with prevalent cardiovascular disease, 71 were also associated with CACS in a similar pattern. Yet, in the model adjusted for all seven cardiovascular risk factors, only plasma glucose levels as well as the triglyceride content of larger LDL particles remained significant. Conclusion In this study we identified metabolites associated with prevalent cardiovascular disease and subclinical cardiovascular disease (CACS) in patients with CKD. For prevalent cardiovascular disease associations were mainly found for HDL associated metabolites, while CACS was associated with an increase in the triglyceride content of LDL particles and glucose. Further work needs to be done to establish whether these associations are merely a consequence of the cardiovascular burden or whether there is a causal relation.

Original and generic clopidogrel: A comparison of antiplatelet effects and active metabolite concentrations in patients without polymorphisms in the ABCB1 gene and the allele variants CYPC19*2 and *3

Ticagrelor and prasugrel are widely used as antiplatelet therapy after coronary angioplasty. However, there is a group of patients with indications for clopidogrel treatment. This population includes patients with chronic or acute coronary syndrome who are treated invasively and have contraindications to the use of novel antiplatelet drugs due to antithrombotic treatment (particularly with non-vitamin K antagonist oral anticoagulants). A wide range of generic forms of clopidogrel are available on the market. However, it is unclear whether they are as effective as the originator drug. In the current study, we aimed to assess the concentrations of the active metabolite of clopidogrel and its effect on platelet aggregation inhibition in patients receiving the originator drug in comparison with those receiving generic clopidogrel. We enrolled 22 healthy individuals without polymorphisms in the ABCB1 gene and the allele variants CYPC19*2 and CYPC19*3. All participants received a loading dose of clopidogrel (600 mg), followed by a maintenance dose of 75 mg for the next 3 days. On day 3, blood samples were obtained 1 h after drug administration to assess active metabolite concentrations using liquid chromatography with tandem mass spectrometry. In each participant, platelet aggregation was assessed with light transmission aggregometry after 5-μmol/L and 10-μmol/L adenosine diphosphate (ADP) stimulation. Assays were performed for the originator clopidogrel and 2 different generic groups. The mean ± standard deviation (SD) concentrations of active clopidogrel did not differ between the originator drug and 2 generic products with clopidogrel (12.7±5 pg/μL compared to 13.0 ±4 pg/μL compared to 14.4 ±4 pg/μL). Platelet aggregation inhibition after stimulation with 5 μmol/L and 10 μmol/L ADP was similar for all preparations. In comparison with original clopidogrel, the use of its generic form does not affect the blood concentrations of the active metabolite or its antiplatelet effect.

Cortical GABA in migraine with aura -an ultrashort echo magnetic resonance spectroscopy study

ObjectiveThe aim of this cross-sectional study was to investigate the cortical metabolite concentrations in patients suffering from migraine with aura (MWA). We hypothesized that occipital γ-aminobutyric acid (GABA) levels are lower in MWA patients.BackgroundRecent studies have indicated that a disturbance in the inhibitory GABA is involved in triggering the migraine aura. We aimed to explore this using a novel magnetic resonance spectroscopy sequence.MethodsUsing spin echo full intensity acquired localized spectroscopy on a Siemens 3 Tesla magnetic resonance scanner, we obtained occipital and parietal metabolite concentrations in 14 patients suffering from migraine with aura and a group of 16 matched healthy subjects.All scans were performed at Aarhus University Hospital, at the Center for Functionally Integrative Neuroscience (CFIN).ResultsNo difference was found in GABA/(Total creatine) levels in either the occipital cortex (p = 0.744) or in the somatosensory cortex (p = 0.305).ConclusionThese findings indicate that cortical GABA levels are normal in patients suffering from relatively few migraine attacks. Previous studies have reported that cortical GABA in patients with more frequent migraines is reduced; further investigation of the inhibitory system in migraine patients is warranted to determine the underlying mechanisms.

Association of Hepatic Global DNA Methylation and Serum One-Carbon Metabolites with Histological Severity in Patients with NAFLD.

Clinical relevance of global DNA methylation and one-carbon metabolite levels with histological severity remains uncertain in patients with nonalcoholic fatty liver disease (NAFLD). This study aimed to evaluate hepatic global DNA methylation and serum one-carbon metabolite concentrations in patients with NAFLD and the possible associations of these parameters with liver histology. Liver biopsies from 18 control participants and 47 patients with NAFLD were evaluated. The hepatic global DNA methylation level was significantly lower in the NAFLD group than in the control group among participants with overweight. Participants with moderate inflammation and mild fibrosis had significantly lower levels of global DNA methylation than those without these characteristics. Participants with borderline nonalcoholic steatohepatitis had significantly lower global DNA methylation levels than controls. The hepatic global DNA methylation level tended to decrease with the increasing hepatic inflammation grade and disease progression. The NAFLD group had a significantly higher serum homocysteine concentration than the control group among participants with overweight. This level tended to increase with increasinghepatic steatosis grade and disease progression. Patients with NAFLD exhibited lower hepatic levels of global DNA methylation and elevated serum homocysteine concentrations, which are associated with the histological severity of NAFLD.

Protein fermentation in the gut; implications for intestinal dysfunction in humans, pigs, and poultry.

The amount of dietary protein is associated with intestinal disease in different vertebrate species. In humans, this is exemplified by the association between high-protein intake and fermentation metabolite concentrations in patients with inflammatory bowel disease. In production animals, dietary protein intake is associated with postweaning diarrhea in piglets and with the occurrence of wet litter in poultry. The underlying mechanisms by which dietary protein contributes to intestinal problems remain largely unknown. Fermentation of undigested protein in the hindgut results in formation of fermentation products including short-chain fatty acids, branched-chain fatty acids, ammonia, phenolic and indolic compounds, biogenic amines, hydrogen sulfide, and nitric oxide. Here, we review the mechanisms by which these metabolites may cause intestinal disease. Studies addressing how different metabolites induce epithelial damage rely mainly on cell culture studies and occasionally on mice or rat models. Often, contrasting results were reported. The direct relevance of such studies for human, pig, and poultry gut health is therefore questionable and does not suffice for the development of interventions to improve gut health. We discuss a roadmap to improve our understanding of gut metabolites and microbial species associated with intestinal health in humans and production animals and to determine whether these metabolite/bacterial networks cause epithelial damage. The outcomes of these studies will dictate proof-of-principle studies to eliminate specific metabolites and or bacterial strains and will provide the basis for interventions aiming to improve gut health.

No major influence of regular tobacco smoking on cerebrospinal fluid monoamine metabolite concentrations in patients with psychotic disorder and healthy individuals

Metabolism of the monoamines dopamine, serotonin and noradrenaline, is altered in the central nervous system of people with schizophrenia, and their major metabolites homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG), respectively, have been intensively studied as indirect measures of these neurotransmitters in cerebrospinal fluid (CSF). Regular tobacco smoking has been shown to alter neurotransmitter metabolism in the brain and studies have found CSF monoamine metabolite concentrations to be substantially lower in smokers. However, few studies investigating these monoamines in CSF have controlled for regular tobacco smoking. We investigated if regular tobacco smoking influences CSF HVA, 5-HIAA and MHPG concentrations in patients treated for psychotic disorders (n = 69) and healthy non-psychotic human volunteers (n = 200). After lumbar puncture CSF samples were analyzed with mass fragmentography. CSF HVA, 5-HIAA and MHPG concentrations did not significantly differ between smokers and non-smokers neither in patients, nor in healthy subjects, whereas back-length predicted HVA and 5-HIAA and antipsychotic medication MHPG concentrations. The results indicate that regular tobacco smoking has no significant effect on monoamine metabolite concentrations in CSF. This suggests that lack of controlling for regular tobacco smoking should not substantially violate the results in studies of the major monoamine metabolites in CSF.

In vitro trials of a wearable artificial kidney (WAK).

This paper presents results of in vitro trials of a wearable artificial kidney (WAK). To carry out the trials, a test bench was developed. It consisted of a patient imitator, a tubing set and measuring equipment. Our WAK can eliminate urea, uric acid and creatinine from spent dialysate with mean mass rates of 0.85 ± 0.1 g/h, 0.10 ± 0.04 g/h and 0.05 ± 0.01 g/h, respectively. Concentrations of Na+, Cl- and Ca2+ ions were kept in the 10% range from initial values. We demonstrated that our WAK can operate for 38 hours without having to replace expendable materials. The WAK that we developed can eliminate metabolites from spent dialysis fluid with mass rates that are sufficient to maintain stable, physiologically normal metabolite concentrations in patients' blood.

Vitamin D levels in critically ill patients with acute kidney injury: a protocol for a prospective cohort study (VID-AKI)

IntroductionAcute kidney injury (AKI) affects more than 50% of critically ill patients. The formation of calcitriol, the active vitamin D metabolite, from the main inactive circulating form, 25-hydroxyvitamin D (25(OH)D),...

Cerebrospinal fluid monoamine metabolite profiles in bipolar disorder, ADHD, and controls

Alterations in monoaminergic signaling are suggested as key aspects of the pathophysiology in bipolar disorder and ADHD, but it is not known if the monoamine metabolic profile differs between these disorders. One method to study monoaminergic systems in humans is to measure monoamine end-point metabolite concentrations in cerebrospinal fluid (CSF). Here, we analyzed CSF monoamine metabolite concentrations in 103 adults with bipolar disorder, 72 adults with ADHD, and 113 controls. Individuals with bipolar disorder had significantly higher homovanillic acid (HVA, 264 ± 112 nmol/L, p < 0.001) and 5-hydroxyindoleacetic acid (5-HIAA, 116 ± 42 nmol/L, p = 0.001) concentration, but lower 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG, 38 ± 8 nmol/L, p < 0.001) concentrations than controls (HVA, 206 ± 70 nmol/L; 5-HIAA, 98 ± 31 nmol/L; and MHPG, 42 ± 7 nmol/L). Higher HVA concentrations were associated with a history of psychosis in the bipolar disorder sample. Subjects with ADHD had higher HVA (240 ± 94 nmol/L, p < 0.001) concentrations compared with controls. In addition, SSRI treatment was associated with lower 5-HIAA concentrations in both patient groups. A power analysis indicated that for within-group comparisons, only large effects would be reliably detectable. Thus, there may be moderate-to-small effects caused by medication that were not detected due to the limited size of the sub-groups in these analyses. In conclusion, the present study suggests disorder-specific alterations of CSF monoamine metabolite concentrations in patients with bipolar disorder and ADHD compared with controls; these differences were independent of acute symptoms and medication effects.

Kynurenine Pathway Activation in Human African Trypanosomiasis.

Background.The kynurenine pathway of tryptophan oxidation is associated with central nervous system (CNS) inflammatory pathways. Inhibition of this pathway ameliorates CNS inflammation in rodent models of the late (meningoencephalitic) stage of human African trypanosomiasis (HAT). In this study, we evaluate whether the kynurenine pathway is activated in clinical HAT and associated with CNS inflammatory responses.Methods.We measured cerebrospinal fluid (CSF) tryptophan and kynurenine metabolite concentrations in patients infected with Trypanosoma brucei rhodesiense, using liquid chromatography–mass spectrometry.Results.Kynurenine concentration in CSF was increased in both the early and late stages of disease, with a progressive increase in tryptophan oxidation associated with stage progression. Kynurenine pathway activation was associated with increases in neuroinflammatory markers, but there was no clear relationship to neurological symptoms.Conclusions.CNS kynurenine pathway activation occurs during HAT, including cases prior to the current diagnostic cutoff for late-stage infection, providing evidence for early CNS involvement in HAT. Metabolite data demonstrate that the kynurenine-3-monooxygenase and kynurenine aminotransferase branches of the kynurenine pathway are active. The association between tryptophan oxidation and CNS inflammatory responses as measured by CSF interleukin 6 (IL-6) concentration supports a role of kynurenine metabolites in the inflammatory pathogenesis of late-stage HAT.

Short-term effects of air temperature on plasma metabolite concentrations in patients undergoing cardiac catheterization

BackgroundEpidemiological studies have shown associations between air temperature and cardiovascular health outcomes. Metabolic dysregulation might also play a role in the development of cardiovascular disease. ObjectivesTo investigate short-term temperature effects on metabolites related to cardiovascular disease. MethodsConcentrations of 45 acylcarnitines, 15 amino acids, ketone bodies and total free fatty acids were available in 2869 participants from the CATHeterization GENetics cohort recruited at the Duke University Cardiac Catheterization Clinic (Durham, NC) between 2001 and 2007. Ten metabolites were selected based on quality criteria and cluster analysis. Daily averages of meteorological variables were obtained from the North American Regional Reanalysis project. Immediate, lagged, and cumulative temperature effects on metabolite concentrations were analyzed using (piecewise) linear regression models. ResultsLinear temperature effects were found for glycine, C16-OH:C14:1-DC, and aspartic acid/asparagine. A 5°C increase in temperature was associated with a 1.8% [95%-confidence interval: 0.3%; 3.3%] increase in glycine (5-day average), a 3.2% [0.1%; 6.3%] increase in C16-OH:C14:1-DC (lag of four days), and a −1.4% [−2.4%; −0.3%] decrease in aspartic acid/asparagine (lag of two days). Non-linear temperature effects were observed for alanine and total ketone bodies with breakpoint of 4°C and 20°C, respectively. Both a 5°C decrease in temperature on colder days (<4°C)and a 5°C increase in temperature on warmer days (≥4°C) were associated with a four day delayed increase in alanine by 6.6% [11.7; 1.8%] and 1.9% [0.3%; 3.4%], respectively. For ketone bodies we found immediate (0-day lag) increases of 4.2% [−0.5%; 9.1%] and 12.3% [0.1%; 26.0%] associated with 5°C decreases on colder (<20°C) days and 5°C increases on warmer days (≥20°C), respectively. ConclusionsWe observed multiple effects of air temperature on metabolites several of which are reported to be involved in cardiovascular disease. Our findings might help to understand the link between air temperature and cardiovascular disease.

Chemotyping the distribution of vitamin D metabolites in human serum.

Most studies examining the relationships between vitamin D and disease or health focus on the main 25-hydroxyvitamin D3 (25(OH)D3) metabolite, thus potentially overlooking contributions and dynamic effects of other vitamin D metabolites, the crucial roles of several of which have been previously demonstrated. The ideal assay would determine all relevant high and low-abundant vitamin D species simultaneously. We describe a sensitive quantitative assay for determining the chemotypes of vitamin D metabolites from serum after derivatisation and ultra-high performance liquid chromatography-electrospray ionisation-tandem mass spectrometry (UHPLC-ESI-MS/MS). We performed a validation according to the ‘FDA Guidance for Industry Bioanalytical Method Validation’. The proof-of-concept of the method was then demonstrated by following the metabolite concentrations in patients with chronic liver diseases (CLD) during the course of a vitamin D supplementation study. The new quantitative profiling assay provided highly sensitive, precise and accurate chemotypes of the vitamin D metabolic process rather than the usually determined 25(OH)D3 concentrations.

Relationship between blood plasma and synovial fluid metabolite concentrations in patients with osteoarthritis.

To investigate the relationship between plasma and synovial fluid (SF) metabolite concentrations in patients with osteoarthritis (OA). Blood plasma and SF samples were collected from patients with primary knee OA undergoing total knee arthroplasty. Metabolic profiling was performed by electrospray ionization tandem mass spectrometry using the AbsoluteIDQ kit. The profiling yielded 168 metabolite concentrations. Correlation analysis between SF and plasma metabolite concentrations was done on absolute concentrations as well as metabolite concentration ratios using Spearman's rank correlation (ρ) method. A total of 69 patients with knee OA were included, 30 men and 39 women, with an average age of 66 ± 8 years. For the absolute metabolite concentrations, the average ρ was 0.23 ± 0.13. Only 8 out of 168 metabolite concentrations had a ρ ≥ 0.45, with a p value ≤ 2.98 × 10(-4), statistically significant after correcting multiple testing with the Bonferroni method. For the metabolite ratios (n = 28,056), the average ρ was 0.29 ± 0.20. There were 4018 metabolite ratios with a ρ ≥ 0.52 and a p value ≤ 1.78 × 10(-6), significant after correcting multiple testing. Sex-separate analyses found no difference in ρ between men and women. Similarly, there was no difference in ρ between people younger and older than 65 years. Correlation between blood plasma and SF metabolite concentrations are modest. Metabolite ratios, which are considered proxies for enzymatic reaction rates and have higher correlations, should be considered when using blood plasma as a surrogate of SF in OA biomarker identification.

1H Magnetic Resonance Spectroscopy Findings in Idiopathic Inflammatory Myopathies at 3 T

The aim of this study was to investigate the feasibility and potential use of quantitative proton magnetic resonance spectroscopy (MRS) for determining metabolite concentrations in patients with suspected inflammatory myopathies. In this institutional review board-approved, Health Insurance Portability and Accountability Act-compliant prospective study, 35 patients with a suspected inflammatory myopathy and 6 age-matched healthy volunteers underwent magnetic resonance imaging (MRI) (T1-weighted and short tau inversion recovery [STIR] sequences) and single-voxel MRS (point-resolved spectroscopy; repetition time/echo time, 2000/135 milliseconds; voxel size, 2.0 × 2.0 × 4.0 cm) at 3 T. The voxel was placed in a thigh muscle and targeted to one with abnormal STIR signal when possible. Absolute trimethylamine, creatine (Cr), and bulk lipid concentrations in each voxel were determined using the phantom replacement method. The MRS results of patients and healthy subjects were compared using the Wilcoxon rank sum test. Twenty-one patients were diagnosed with an active idiopathic inflammatory myopathy (IIM). In 20 of these patients, MRI showed increased intramuscular STIR signal; however, the muscle where the voxel was placed was normal in 9 patients. Patients with an IIM demonstrated higher mean intramuscular Cr concentration compared with controls (62.1 vs 35.3 IU; P = 0.01), but there were no differences in the mean trimethylamine or lipid concentrations. In IIM patients with no intravoxel signal abnormality (9/21), the mean Cr concentration was still higher than that in healthy subjects (63.2 vs 35.3 IU; P = 0.001). Quantitative 3-T MRS is feasible and may supplement the role of conventional MRI in the evaluation of patients with inflammatory myopathies, especially where MRI shows no obvious muscle abnormalities.

Purine metabolites in fibromyalgia syndrome

ObjectiveTo evaluate serum purine metabolite concentrations in patients affected by fibromyalgia syndrome (FMS) and the relationships between their levels and FM clinical parameters. Design and methodsSerum purine levels were quantified using LC/UV–vis in 22 fibromyalgic females (according to the American College of Rheumatology classification criteria) and 22 healthy females. ResultsSignificantly higher serum inosine, hypoxanthine and xanthine levels (p<0.001) and significantly lower serum adenosine (p<0.05) were detected in the FMS patients vs healthy controls. Our data show a negative correlation between adenosine and Fibromyalgia Impact Questionnaire (FIQ). ConclusionsStudy results suggest that purines, in particular adenosine and inosine, may be involved in pain transmission in fibromyalgia.

Clinical usefulness of therapeutic drug monitoring of thiopurines in patients with inadequately controlled inflammatory bowel disease

Circulating concentrations of 6-thioguanine nucleotide (6-TGN) and 6-methyl mercaptopurine (6-MMP) are associated with thiopurine efficacy and may predict toxicity. This study aimed to examine retrospectively the utility of measuring metabolite concentrations in patients with inflammatory bowel disease (IBD) who had continuing symptoms despite stable thiopurine treatment. Concentrations of 6-TGN and 6-MMP were measured in lysates of washed red cells by high-performance liquid chromatography in peripheral blood drawn from 63 symptomatic patients with IBD (63% men, mean age 37, range 14-74 years, 67% Crohn's disease, 33% ulcerative colitis) treated with azathioprine or 6-mercaptopurine. Short-term clinical outcomes were examined. 6-TGN concentrations weakly correlated with the thiopurine dose (r = 0.28, P = 0.08). On weight-based criteria, 50% of patients were underdosed. However, metabolite patterns suggested 7 (11%) patients were noncompliant, 18 (29%) were being underdosed, 33 (52%) were refractory to treatment with either appropriate (41%) or elevated (11%) metabolite concentrations, and 6 (10%) had a raised 6-MMP:6-TGN ratio consistent with aberrant thiopurine metabolism. The clinical outcome improved in 40 of 46 (87%) of patients in whom the course of action taken was as recommended by a metabolite-directed algorithm, while 3 of 17 patients (18%) improved where discordant actions were taken (P = 0.0001; Fisher's exact test). Fifteen patients (24%) avoided inappropriate escalation of therapy. Dose-optimization or toxicity-avoidance strategies frequently result from metabolite testing in patients with inadequate efficacy from thiopurines, with evidence of better outcomes. Thiopurine metabolite testing is a potentially powerful tool for optimizing thiopurine usage in IBD.