Measurement Of Catecholamines Research Articles

Metabolic impact of pheochromocytoma/paraganglioma: targeted metabolomics in patients before and after tumor removal.

Excess catecholamine release by pheochromocytomas and paragangliomas (PPGL) leads to characteristic clinical features and increased morbidity and mortality. The influence of PPGLs on metabolism is ill described but may impact diagnosis and management. The objective of this study was to systematically and quantitatively study PPGL-induced metabolic changes at a systems level. Targeted metabolomics by liquid chromatography-tandem mass spectrometry of plasma specimens in a clinically well-characterized prospective cohort study. Analyses of metabolic profiles of plasma specimens from 56 prospectively enrolled and clinically well-characterized patients (23 males, 33 females) with catecholamine-producing PPGL before and after surgery, as well as measurement of 24-h urinary catecholamine using LC-MS/MS. From 127 analyzed metabolites, 15 were identified with significant changes before and after surgery: five amino acids/biogenic amines (creatinine, histidine, ornithine, sarcosine, tyrosine) and one glycerophospholipid (PCaeC34:2) with increased concentrations and six glycerophospholipids (PCaaC38:1, PCaaC42:0, PCaeC40:2, PCaeC42:5, PCaeC44:5, PCaeC44:6), two sphingomyelins (SMC24:1, SMC26:1) and hexose with decreased levels after surgery. Patients with a noradrenergic tumor phenotype had more pronounced alterations compared to those with an adrenergic tumor phenotype. Weak, but significant correlations for 8 of these 15 metabolites with total urine catecholamine levels were identified. This first large prospective metabolomics analysis of PPGL patients demonstrates broad metabolic consequences of catecholamine excess. Robust impact on lipid and amino acid metabolism may contribute to increased morbidity of PPGL patients.

3117 “A Gut Feeling”: Autonomic Instability and Dysbiosis in Connective Tissue Disease

INTRODUCTION: Ehlers-Danlos Syndrome (EDS) is a connective tissue disease in which mutations in certain genes result in a disruption of normal collagen. There are several subtypes of the disease. Among the various subtypes which exist, hypermobility is the most common. Many of these patients can have co-existing gastrointestinal symptoms, which are often times overlooked by practitioners. CASE DESCRIPTION/METHODS: A 23 year old female presented with chest tightness, daily palpitations, and diarrhea which had been persistent for three days. Her past medical history was notable for spinal stenosis and lactose intolerance. She denied any associated abdominal pain, fever, or chills. Her family history was non contributory. One month later, she continued to have diarrhea and heartburn. She endorsed symptoms of mucorrhea with associated bright red blood per rectum, lower abdominal pain, and fecal urgency. A thorough physical examination revealed hyper flexible joints and greater than normal mobility of her fingers. After genetic testing, she was later diagnosed with Ehlers-Danlos Type 3. DISCUSSION: Up to 57% of patients with EDS have coexisting functional bowel disorders.1 Chronic gastrointestinal discomfort was reported in 86% of patients with Ehlers-Danlos – hyper mobile subtype.2 Gastrointestinal complications can include gastro esophageal reflux disease, hiatal hernia, gastritis, gastric emptying, irritable bowel syndrome (found in 62% of patients), rectal evacuatory dysfunction, and delayed colonic transit.1,2,4 Symptoms are thought to occur as a result of bidirectional signaling between gut bacteria and the brain. Enterochromaffin cells are not only accessible by enteric microbiota but also have contact with afferent and efferent nerve terminals acting as “transducers” between the gut and brain,8 able to secrete various compounds, including serotonin. One study showed that pretreatment of animals with probiotic formulation consisting of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 attenuated hypothalamic pituitary axis and autonomic nervous system activities, which were assessed through the measurement of plasma cortisol and catecholamines.10 In our patient, she was treated with a course of Rifaximin for IBS-D and was placed on a bowel regimen including a probiotic. At a four-week follow up, her symptoms had improved.

Association Between Urinary Catecholamine Excretion and Urine Volume.

Several confounders must be considered in the evaluation of urinary catecholamine excretion. However, literature is contradictory about potential confounders. The aim of the present study was to assess correlations between catecholamine excretion and anthropometric or clinical parameters with special attention to urine volume. A total of 967 24-h urinary catecholamine measurements were performed in 593 patients for diagnostic purposes. The indication for urine examination was suspicion of secondary hypertension, phaeochromocytoma, or paraganglioma. From the patients examined, 57% were females and 43% were males. The patients' age ranged between 15 and 87 years with a median [Q1; Q3] of 51 [39; 62] years. Seventy-eight percent of the patients suffered from hypertension. Seventy percent of patients took one or more antihypertensive drugs. The most commonly used drugs were ACE inhibitors (43%), while α-blockers (15%) were the least used drugs. Urinary excretion was between 500 and 11 950 ml/24 h with a median of 2200 [1600; 2685] ml/24 h. The median body mass index (BMI) was 26.7 [24.0; 30.4] kg/m2. The excretion of all catecholamines was greater in men than in women (all p<0.0001). Epinephrine (p=0.0026), dopamine (p<0.0001), and metanephrine (p=0.0106) excretion decreased with age. BMI was associated with urinary excretion of dopamine (p<0.0001), norepinephrine (p=0.0026), normetanephrine (p<0.0001), and homovanillylmandelic acid (HVMA; p=0.0251). Urine volume correlated with urinary dopamine (p=0.0127), metanephrine (p<0.0001), normetanephrine (p=0.0070), and HVMA (p<0.0028) excretion. In addition to the established associations between urinary catecholamine excretion and age, gender, and BMI in the present study, urinary catecholamine excretion correlated also with urine volume.

Sex differences in stress and immune responses during confinement in Antarctica

BackgroundAntarctica challenges human explorers by its extreme environment. The effects of these unique conditions on the human physiology need to be understood to best mitigate health problems in Antarctic expedition crews. Moreover, Antarctica is an adequate Earth-bound analogue for long-term space missions. To date, its effects on human physiology have been studied mainly in male cohorts though more female expeditioners and applicants in astronaut training programs are selected. Therefore, the identification of sex differences in stress and immune reactions are becoming an even more essential aim to provide a more individualized risk management.MethodsTen female and 16 male subjects participated in three 1-year expeditions to the German Antarctic Research Station Neumayer III. Blood, saliva, and urine samples were taken 1–2 months prior to departure, subsequently every month during their expedition, and 3–4 months after return from Antarctica. Analyses included cortisol, catecholamine and endocannabinoid measurements; psychological evaluation; differential blood count; and recall antigen- and mitogen-stimulated cytokine profiles.ResultsCortisol showed significantly higher concentrations in females than males during winter whereas no enhanced psychological stress was detected in both sexes. Catecholamine excretion was higher in males than females but never showed significant increases compared to baseline. Endocannabinoids and N-acylethanolamides increased significantly in both sexes and stayed consistently elevated during the confinement. Cytokine profiles after in vitro stimulation revealed no sex differences but resulted in significant time-dependent changes. Hemoglobin and hematocrit were significantly higher in males than females, and hemoglobin increased significantly in both sexes compared to baseline. Platelet counts were significantly higher in females than males. Leukocytes and granulocyte concentrations increased during confinement with a dip for both sexes in winter whereas lymphocytes were significantly elevated in both sexes during the confinement.ConclusionsThe extreme environment of Antarctica seems to trigger some distinct stress and immune responses but—with the exception of cortisol and blood cell counts—without any major relevant sex-specific differences. Stated sex differences were shown to be independent of enhanced psychological stress and seem to be related to the environmental conditions. However, sources and consequences of these sex differences have to be further elucidated.

Importance of sympathetic nervous system activity during left ventricular functional recovery and its association with in-hospital complications in Takotsubo syndrome.

The relationship between activation of the sympathetic nervous system (SNS) and improvement of left ventricular (LV) function and how this correlates with clinical outcomes are not fully explored in Takotsubo syndrome (TS). The purpose of this study is to evaluate the relationship between activation of the SNS and LV function improvement and how this correlates with clinical outcomes in TS. Patients with TS were retrospectively identified. Patients were divided into two groups according to the timing of LV function improvement: < 1month (S group) and ≥ 1month (L group). Activation of the SNS was assessed by plasma catecholamine measurement and Iodine-123 meta-iodobenzylguanidine (I123-MIBG) scintigraphy. In-hospital complications included heart failure, cardiogenic shock, the use of invasive or noninvasive ventilation, life-threatening arrhythmia, cerebrovascular event and all-cause death. A total of 90 patients with TS were enrolled. Of these, 39 patients were in the S group and 51 in the L group. There were no significant differences between the two groups in clinical demographics. The L group was characterized by enhanced SNS activation, including higher levels of catecholamines and lower late heart-mediastinum ratio followed by higher washout rate in I123-MIBG scintigraphy, compared with the S group. In-hospital complications were increased in the L group (56% vs. 33.3%, p = 0.03), including higher rates of heart failure (45% vs. 23%, p = 0.03) and in-hospital death (8.0% vs. 0%, p = 0.03). In patients with TS, high activity of the SNS was observed in patients with delayed LV function recovery, which was associated with in-hospital adverse outcomes.

Core body temperature, energy expenditure, and epinephrine during fasting, eucaloric feeding, and overfeeding in healthy adult men: evidence for a ceiling effect for human thermogenic response to diet

BackgroundIn homeothermic animals, approximately 50% of daily energy expenditure (EE) is spent to maintain a consistent core body temperature (CBT). In humans, little is known about CBT responses to feeding and overfeeding and their relationship to diet-related changes in EE. ObjectiveTo study the effects of feeding and overfeeding on CBT and its association with diet-induced thermogenesis (DIT). DesignFifty-three healthy men with normal glucose regulation and a wide range of body composition (mean ± SD, body fat: 25 ± 8%, range: 7–43%) had 24-h EE assessed during fasting in a whole-room indirect calorimeter with concomitant CBT measurement by ingestible capsules and 24-h urinary collection for catecholamine measurements. Changes in 24-h EE (DIT) and CBT compared to fasting were assessed during three normal-protein (20%) diets using a cross-over design: one eucaloric diet (EBL, 50% carbohydrate, n = 37) and two overfeeding diets with 200% energy requirements: a high-fat (FNP, 60% fat, n = 25) and a high-carbohydrate (CNP; 75% carbohydrate, n = 24) diet. ResultsThe average 24-h CBT (avgCBT) during fasting was 36.81 ± 0.14 °C (inter-individual CV = 0.4%) and positively correlated with 24-h urinary epinephrine (r = 0.61, p < 0.001), but not with body composition measures (p > 0.05). AvgCBT increased during EBL (Δ = 0.06 ± 0.11 °C, p = 0.002), FNP (Δ = 0.13 ± 0.14 °C, p < 0.001), and CNP (Δ = 0.19 ± 0.13 °C, p < 0.001) and associated with increased DIT during EBL (r = 0.43, p = 0.01, β = 31 kcal/day/0.1 °C) and FNP (r = 0.60, p = 0.002, β = 43 kcal/day/0.1 °C), but not CNP (p = 0.47). A ceiling effect for the increase in CBT, but not in DIT, was observed during feeding and, particularly, overfeeding. ConclusionsCBT increases with feeding and is moderately associated with DIT to a different degree depending on the macronutrient composition of the overfeeding diet. There is a ceiling effect such that individuals with a higher CBT during fasting have limited capacity to increase CBT with feeding. Because of body thermoregulatory mechanisms that maintain a constant CBT, these results indicate that CBT has a limited role in the inter-individual variability in DIT.

Plasma catecholamine levels in the early stages of treatment-naïve Parkinson’s disease

Rationale: Parkinson's disease (PD) is a neurodegenerative disorder with predominant involvement of catecholamine-producing neurons of the central and peripheral nervous system. Taking into account the relative availability and low costs of plasma catecholamine measurements, it is worthwhile to study these parameters as biomarkers of the early stages of PD.Aim: To determinate whether plasma levels of dopamine (DA), norepinephrine (NE), L-3,4-dihydroxyphenylalanine (DOPA) and dihydroxyphenylacetic acid (DOPAC) in patients with early stages of PD are related with akinetic-rigid and tremor-dominant variants and to compare the results to healthy volunteers.Materials and methods: This was an observational cross-sectional cohort study performed from 2012 to 2015. The main study group included unselected outpatients who attended the Republican Consultative and Diagnostic Center of Movement Disorders and Botulinotherapy (Kazan, Russia) with newly diagnosed early PD (Hoehn and Yahr stages I and II, 1967), of various ages and both genders, who had not been given any specific antiparkinsonian treatment. The control group included healthy volunteers with no clinical signs of PD (they could have other chronic diseases of the non-extrapyramidal origin). Plasma catecholamine levels were measured by gas liquid chromatography.Results: One hundred and thirty (130) treatment-naïve patients with newly diagnosed PD (mean age 59.34 ± 8.42 years, male gender 45.38%) were enrolled into the main study group. The control group included 56 healthy volunteers matched for age and gender. The distribution of various PD forms and stages was as follows: PD tremor-dominant variant 56.9%, PD akinetic-rigid variant 43.1%; PD stage I 76.9%, PD stage II 23.1%. Irrespective of the variant and stage, the PD patients demonstrated decreased NE levels, compared to the controls (95% confidence intervals 124–216 and 248–428 pg/mL, respectively, р &lt; 0.026). DOPA plasma level was reduced only in the patients with akinetic-rigid PD variant (р = 0.017), while DOPAC level in the patients with PD stage II (р = 0.008). The average DA:NE:DOPA:DOPAC ratio was 1:32:105:64 in the control group, 1:62:238:88 in the patients with PD tremor-dominant variant (the difference is significant for NE and DOPA, р &lt; 0.05), and 1:29:96:32 in those with PD akinetic-rigid variant (p &gt; 0.05). In the healthy controls the changes in DOPA levels account for 84% of the DA and NE variability; no correlation between DOPAC and other catecholamines was found. On the contrary, in the PD patients regardless of the stage and the disease variant, DOPAC levels directly correlated with DA (p &lt; 0.04). The PD tremor-dominant variant patients demonstrated a direct correlation between plasma NE and DOPA levels (p &lt; 0.05).Conclusion: The results obtained on absolute and relative parameters catecholamine turnover in the patients with early PD stages support the hypothesis on different pathophysiology of the tremor-dominant and akinetic-rigid variants of PD.

Renal Denervation Reduced Ventricular Arrhythmia After Myocardial Infarction by Inhibiting Sympathetic Activity and Remodeling.

BackgroundVentricular arrhythmia after myocardial infarction is the most important risk factor for sudden cardiac death, which poses a serious threat to human health. As the correlation between autonomic nervous systemic dysfunction and heart rhythm abnormality has been gradually revealed, remedies targeting autonomic nervous system dysfunction, especially the sympathetic nerve, have emerged. Among them, renal denervation is noted for its powerful effect on the inhibition of sympathetic nerve activity. We aim to investigate whether renal denervation can reduce ventricular arrhythmia after myocardial infarction and thus decrease the risk of sudden cardiac death. In addition, we explore the potential mechanism with respect to nerve activity and remodeling.Methods and ResultsTwenty‐four beagles were randomized into the control (n=4), renal denervation (n=10), and sham (n=10) groups. Permanent left anterior descending artery ligation was performed to establish myocardial infarction in the latter 2 groups. Animals in the renal denervation group underwent both surgical and chemical renal denervation. Compared with dogs in the sham group, dogs in the renal denervation group demonstrated attenuated effective refractory period shortening and inhomogeneity, flattened restitution curve, increased ventricular threshold, and decreased ventricular arrhythmia. Heart rate variability assessment, catecholamine measurement, and nerve discharge recordings all indicated that renal denervation could reduce whole‐body and local tissue sympathetic tone. Tissue analysis revealed a significant decrease in neural remodeling in both the heart and stellate ganglion.ConclusionsSurgical and chemical renal denervation decreased whole‐body and local tissue sympathetic activity and reversed neural remodeling in the heart and stellate ganglion. Consequently, renal denervation led to beneficial remodeling of the electrophysiological characteristics in the infarction border zone, translating to a decrease in ventricular arrhythmia after myocardial infarction.

Norepinephrine and T4 Are Predictors of Fat Mass Gain in Humans With Cold-Induced Brown Adipose Tissue Activation.

In healthy adults with detectable cold-induced brown adipose tissue activation (CIBA), the relationships between sympathetic nervous system (SNS) or thyroid activity during energy balance (EBL) with CIBA and body composition change are undetermined. To investigate the relationships between CIBA and thermoneutral catecholamines and thyroid hormones measured during EBL and to determine if CIBA, catecholamines, or thyroid hormones predict body composition changes. Twelve healthy volunteers (seven male and five female) with positive CIBA [>2 standardized uptake value (g/mL)] had 24-hour energy expenditure (24hEE) assessed during EBL via whole-room indirect calorimetry while residing on a clinical research unit. Positron emission tomography/computed tomography scans were performed after exposure to 16°C for 2 hours to quantify CIBA. CIBA, 24hEE during EBL, and thermoneutrality with concomitant measurement of urinary catecholamines and plasma free T3 and free T4. Body composition at baseline and 6 months by dual-energy X-ray absorptiometry. Lower urinary norepinephrine and free T4 were associated with higher CIBA (r = -0.65, P = 0.03; and r = -0.75, P < 0.01, respectively), but CIBA was not associated with 24hEE at thermoneutrality (P = 0.77). Lower CIBA (β = -3.5 kg/standardized uptake value; P < 0.01) predicted fat mass gain, whereas higher urinary norepinephrine and free T4 predicted future fat mass gain at 6 months (β = 3.0 kg per twofold difference in norepinephrine, P = 0.03; and β = 1.2 kg per 0.1-ng/dL difference in free T4, P = 0.03, respectively). Lower SNS and free thyroid measurements at baseline indicate a greater capacity for CIBA, which may be predictive against fat mass gain.

Does sympathetic dysfunction occur before denervation in pure autonomic failure?

Pure autonomic failure (PAF) is a rare sporadic disorder characterized by autonomic failure in the absence of a movement disorder or dementia and is associated with very low plasma norepinephrine (NE) levels-suggesting widespread sympathetic denervation, however due to its rarity the pathology remains poorly elucidated. We sought to correlate clinical and neurochemical findings with sympathetic nerve protein abundances, accessed by way of a forearm vein biopsy, in patients with PAF and in healthy controls and patients with multiple systems atrophy (MSA) in whom sympathetic nerves are considered intact. The abundance of sympathetic nerve proteins, extracted from forearm vein biopsy specimens, in 11 patients with PAF, 8 patients with MSA and 9 age-matched healthy control participants was performed following a clinical evaluation and detailed evaluation of sympathetic nervous system function, which included head-up tilt (HUT) testing with measurement of plasma catecholamines and muscle sympathetic nerve activity (MSNA) in addition to haemodynamic assessment to confirm the clinical phenotype. PAF participants were found to have normal abundance of the NE transporter (NET) protein, together with very low levels of tyrosine hydroxylase (TH) (P<0.0001) and reduced vesicular monoamine transporter 2 (VMAT2) (P<0.05) protein expression compared with control and MSA participants. These findings were associated with a significantly higher ratio of plasma 3,4-dihydroxyphenylglycol (DHPG):NE in PAF participants when compared with controls (P<0.05). The finding of normal NET abundance in PAF suggests intact sympathetic nerves but with reduced NE synthesis. The finding of elevated plasma ratio of DHPG:NE and reduced VMAT2 in PAF indicates a shift towards intraneuronal NE metabolism over sequestration in sympathetic nerves and suggests that sympathetic dysfunction may occur ahead of denervation.

Vascular endothelial function masks increased sympathetic vasopressor activity in rats with metabolic syndrome.

Sympathetic hyperactivation, a common feature of obesity and metabolic syndrome, is a key trigger of hypertension. However, some obese subjects with autonomic imbalance present a dissociation between sympathetic activity-mediated vasoconstriction and increased blood pressure. Here, we aimed to determine in a rat model of metabolic syndrome whether the endothelium endothelial nitric oxide (NO) synthase (eNOS)-NO pathway contributes to counteract the vasopressor effect of the sympathetic system. Rats were fed a high-fat and high-sucrose (HFS) diet for 15 wk. Sympathovagal balance was evaluated by spectral analysis of heart rate variability and plasmatic catecholamine measurements. Blood pressure was measured in the presence or absence of N-nitro-l-arginine methyl ester (l-NAME) to inhibit the contribution of eNOS. Vascular reactivity was assessed on isolated aortic rings in response to α1-adrenergic agonist. The HFS diet increased sympathetic tone, which is characterized by a higher low on the high-frequency spectral power ratio and a higher plasmatic concentration of epinephrine. Despite this, no change in blood pressure was observed. Interestingly, HFS rats exhibited vascular hyporeactivity (-23.6%) to α1-adrenergic receptor stimulation that was abolished by endothelial removal or eNOS inhibition (l-NAME). In addition, eNOS phosphorylation (Ser1177) was increased in response to phenylephrine in HFS rats only. Accordingly, eNOS inhibition in vivo revealed higher blood pressure in HFS rats compared with control rats (147 vs. 126 mmHg for mean blood pressure, respectively). Restrain of adrenergic vasopressor action by endothelium eNOS is increased in HFS rats and contributes to maintained blood pressure in the physiological range. NEW & NOTEWORTHY Despite the fact that prohypertensive sympathetic nervous system activity is markedly increased in rats with early metabolic syndrome, they present with normal blood pressure. These observations appear to be explained by increased endothelial nitric oxide synthase response to adrenergic stimulation, which results in vascular hyporeactivity to α-adrenergic stimulation, and therefore blood pressure is preserved in the physiological range. Listen to this article's corresponding podcast at http://www.physiology.org/doi/10.1152/ajpheart.00217.2017 .

Ultrasonic-Aided Fabrication of Nanostructured Au-Ring Microelectrodes for Monitoring Transmitters Released from Single Cells.

We report a novel ultrasonic-aided fast and straightforward approach to fabricate Au microelectrodes by electroless deposition of nanostructured gold films on the rigid outer surface of pulled glass capillaries. Microelectrodes with tip diameters ranging from several hundred nanometers to several micrometers were fabricated within 20 min via three sequential ultrasonication steps. The ultrasonication technique has been validated to be a very effective route in engineering the morphology of Au film surfaces and improves the fabrication efficiency of Au microelectrodes. The nanostructured surfaces of the Au microelectrodes demonstrate excellent sensing activity and antifouling for dopamine oxidation. The microelectrodes were applied for measurement of catecholamines released from exocytosis events from single chromaffin cells and exhibited faster dynamic peak parameters, compared with carbon fiber microelectrodes. This report provides a generally accessible and complementary platform for analyzing catecholamines release events, which should be useful for new electrode designs and neurochemical sensing.

Quando hipertensão arterial persistente no adolescente tem uma origem endócrina rara: relato de dois casos e revisão da literatura

*** When persistent hypertension in adolescents has a rare endocrine etiology: report of two cases and literature review ***AIMS: To report two clinical cases of pheochromocytoma, a rare tumor in the pediatric population, that affects the adrenal medulla, is malignant in up to 47% of cases, and whose clinical manifestations result from hypersecretion of catecholamines.CASE DESCRIPTION: Two cases of pheochromocytoma in adolescents are described, both with persistent hypertension and one with headache, sweating, and tachycardia. Renal and adrenal ultrasound, computed tomography angiography, and measurements of catecholamines and their metabolites revealed pheochromocytoma in the left adrenal gland. Adrenalectomy was performed after pretreatment with α-blockers. Pathological examination confirmed the diagnosis. Blood pressure returned to normal in both patients after treatment.CONCLUSIONS: Pheochromocytoma has a varied and nonspecific clinical presentation, but this condition should always be considered in the differential diagnosis of high blood pressure. Early diagnosis may imply a less aggressive treatment, lower morbidity, and a lesser impact on patients’ quality of life. The high likelihood of recurrence of pheochromocytoma, including as metastatic disease, requires follow-up visits for several years after its initial clinical presentation, even in the case of an apparent cure.

Development and validation of a liquid chromatography tandem mass spectrometry method for the measurement of urinary catecholamines in diagnosis of pheochromocytoma.

The measurement of catecholamines in human body fluids is requested frequently for the differential diagnosis and monitoring of pheochromocytoma. The methods in most clinical laboratories focus on high-performance liquid chromatography coupled with electrochemical detection, which suffers from high background noise, low sensitivity, and poor separation. We reported and developed a robust high-throughput liquid chromatography tandem mass spectrometry method in routine clinical laboratories for the measurement of urinary catecholamines for diagnosis of pheochromocytoma. The method was validated for consistent linearity, good recovery (88-112%), excellent stability and low carryover. Intra- and inter-assay precision values for catecholamines were all below 3.35 and 4.83% respectively. Dilution linearity was investigated with satisfactory linearly dependent coefficients (r > 0.9988). The reference intervals were obtained from 310 results derived from patients in which the diagnosis of pheochromocytoma was excluded. This method was successfully used in our laboratory. The clinical characteristics of patients have been explored with satisfactory sensitivity and specificity. Therefore, we have developed a reliable assay for the liquid chromatography tandem mass spectrometry measurement of catecholamines in a routine clinical laboratory. The assay requires a small volume of urine, and all analytes are measured simultaneously. The assay is rapid and reliable to be executed, offering the potential for routine clinical laboratories.

Adrenal Vein Catecholamine Levels and Ratios: Reference Intervals Derived from Patients with Primary Aldosteronism.

Phaeochromocytoma localisation is generally reliably achieved with modern imaging techniques, particularly in sporadic cases. On occasion, however, there can be diagnostic doubt due to the presence of bilateral adrenal abnormalities, particularly in patients with mutations in genes predisposing them to the development of multiple phaeochromocytomas. In such cases, surgical intervention is ideally limited to large or functional lesions due to the long-term consequences associated with hypoadrenalism. Adrenal venous sampling (AVS) for catecholamines has been used in this situation to guide surgery, although there are few data available to support diagnostic thresholds. Retrospective analyses of AVS results from 2 centres were carried out. A total of 172 patients (88 men, 84 women) underwent AVS under cosyntropin stimulation for the diagnosis of established primary aldosteronism (PA) with measurement of adrenal and peripheral venous cortisol, aldosterone and catecholamines. Six patients (3 men, 3 women) with phaeochromocytoma underwent AVS for diagnostic purposes with subsequent histological confirmation. Reference intervals for the adrenal venous norepinephrine to epinephrine ratio were created from the PA group. Using the 97.5th centile (1.21 on the left, 1.04 on the right), the false negative rate in the phaeochromocytoma group was 0%. In conclusion, this study describes the largest dataset of adrenal venous catecholamine measurements and provides reference intervals in patients without phaeochromocytoma. This strengthens the certainty with which conclusions related to adrenal venous sampling for catecholamines can be drawn, acknowledging the procedure is not part of the routine diagnostic workup and is an adjunct for use only in difficult clinical cases.

Challenges of Simultaneous Measurement of Catecholamines in Mixtures: Steps Toward Neural Probes Suitable for In Vivo Analysis

The roles of catecholamines (dopamine, DA, norepinephrine, NE and epinephrine, EP) in neurological diseases are important in understanding brain function. Fast scan cyclic voltammetry, a conventional electrochemical technique used in such investigations in vivo, suffers from high background current and is either limited or unable to quantitate individual catecholamines in their mixtures. Redox cycling, however, can differentiate between catecholamines based on their propensity to survive diffusion from oxidative (generator) electrodes to and produce an electrochemical response at neighboring reductive (collector) electrodes1 at arrays of two or more closely-spaced sets of the microelectrodes. This process repeats for many rounds until the analyte is lost through diffusion into bulk solution or through homogeneous chemical reactions. At the generator electrode, the catecholamine undergoes a two-electron oxidation (E), producing an o-quinone (OQ) that can be re-reduced at the collector electrode back to the original catecholamine. However, the OQ can undergo an intramolecular cyclization process (C’) to form the leucoaminochrome (LAC), which is electroinactive under our conditions. The apparent intramolecular cyclization rate constants (k) for the three catecholamines are different2 (at pH= 7.4 in phosphate buffer, kEP~89 kNE, kEP~700 kDA, and kNE~7.5 kDA), which provide opportunity for differentiation by spatial distribution based on survival of the OQ form produced at the generator from the following chemistry C.3 Additionally, another OQ can undergo a bimolecular reaction (C’) with the LAC, reducing back to the original catecholamine, while LAC oxidizes to an aminochrome (AC), which is also electroinactive, and especially impacts the spatial distribution of OQ in mixtures of different catecholamines. The number of times that the catecholamine and OQ species go back and forth between generators and collectors defines the magnitude of the signal amplification, which leads to the ability to quantify the catecholamines and determine their detection limits. Fabrication of probes with suitable dimensions is paramount to measuring catecholamines in vivo. The probe shank for feasible catecholamine measurements should be less than 100 µm wide to minimize tissue damage and about 6 mm long to reach the areas of interest in a rat’s brain.4 The devices previously made in our laboratory with which we demonstrated differentiation of catecholamines by redox cycling,5 do not have proper dimensions for insertion into the brain without causing substantial tissue damage. Although other research groups have fabricated and implanted neural probes with multiple electrodes6-9, none to our knowledge have the requisite dimensions, geometry, and number of electrodes suitable for both redox cycling and tissue insertion. We will report the next steps we have taken to improve the design of electrodes to achieve desirable sensitivity and limits of detection and to fabricate the electrodes on probes with suitable dimensions. Using an equation proposed by Aoki et al.,10 we predict that a reversible diffusion-controlled current at an electrode at an array of nine interdigitated microband electrodes, each 100 µm long with our existing dimensions of 4 µm width and 4 µm separation, is about 24 pA for 0.4 µM DA. This current is suitable for quantitative measurements. By decreasing electrode width and gap (e.g. to 1 µm each), and by increasing the number of electrodes on the probe (e.g. 40), detection limits on the order of a tens of nM for a single catecholamine species by redox cycling should be possible. Integrating such designs with the approach to differentiate catecholamines in their mixtures and subsequent impact on detection limits will be discussed. Probe substrates are being constructed from polymer films that are subsequently lifted off a silicon substrate. The challenges associated with the use of SU-8 as the polymer material and new directions using other polymers such as polyimide and parylene will be examined.

Dilute, derivatise and shoot: Measurement of urinary free metanephrines and catecholamines as ethyl derivatives by LC-MSMS

BackgroundThe measurement of catecholamines and their metabolites in either urine or plasma is an important diagnostic test used to exclude the presence of neuroendocrine tumours. Because of weak chromatographic retention and potential ion-suppression, reverse-phase LC-MSMS is not ideal for analysis of these polar molecules. Here, we investigate derivatisation by ethylation as an alternative approach. MethodsA simple and rapid method involving acetaldehyde and a reducing agent was used to convert urine free metanephrines and catecholamines, and their deuterated analogues as internal standards, to mono-ethyl or diethyl- derivatives. Using an Agilent 6460 triple-quadrupole mass spectrometer, precursor and product ion mass spectra were recorded to allow comparison of multiple reaction monitoring methods for both derivatised and non-derivatised analytes under reverse-phase LC-MSMS conditions with positive electrospray ionization. ResultsConversion of biogenic amines to less polar ethyl derivatives increased their mass and enhanced the intensity of their molecular ions and fragments. Ethylation also improved the chromatographic properties of the amines, with greater retention and elution from reverse-phase HPLC columns with a methanol or acetonitrile gradient. The signal response of tandem mass spectrometric detection was increased up to 50-fold for ethyl metanephrines compared to non-derivatised compounds. This increase allowed for the omission of solid-phase extraction of urine as a clean-up step prior to analysis. The ‘dilute-derivatise-shoot’ method maintained analytical performance with respect to between-run imprecision (CV<6%) and accuracy in an external quality assurance program. Gender-related ranges for free metanephrines in early-morning spot urines, collected from adult patients, were similar using either derivatised or non-derivatised samples. ConclusionsThe LC-MSMS detection of free urine biogenic amines can be greatly enhanced by ethyl derivatisation, which is easy and rapid to perform. Advantages include improved chromatography and lower limits of quantitation, that negate the requirement for solid-phase clean-up of urine prior to analysis. A disadvantage is the potential toxicity of the derivatising agents used if they are not handled appropriately.

Influences of Experimental Air Pollution on Human Sympathetic Nerve Traffic and Norepinephrine Metabolism: A Double Blind, Randomized, Twofold Crossover Study

BackgroundMuch of the evidence linking air pollutant exposure with changes in human cardiovascular autonomic regulation relied on epidemiological studies, exposure estimates, and indirect autonomic nervous system measurements. We tested the hypothesis that in healthy older individuals, experimental exposure to fine particles increases sympathetic nervous system activity and more so with addition of ozone.Material and MethodsEighteen healthy participants (age &gt;50 years) completed all study visits and were included in the final analysis. Participants were exposed to clean air (‘placebo’), ultrafine particles (UFP, 50μg/m3), and combination of UFP+ozone (250 ppb) for 3 hours combined with intermittent bicycle ergometer training in a randomized, three‐period, cross‐over, double‐blind fashion. Three hours following exposure, respiration, ECG, blood pressure, and muscle sympathetic nerve activity (MSNA) were continuously recorded at supine rest, during deep breathing, and during a Valsalva maneuver. Venous blood samples for plasma catecholamine measurements were taken at baseline. Induced sputum was obtained at the end of each study day.ResultsCombined exposure to ozone and UFP but not UFP alone caused a significant increase in sputum neutrophils and circulating leucocytes. We did not detect significant effects on blood pressure or heart rate. Resting MSNA was 47±12 with clean air, 47±14 with UFP, and 45±14 bursts/min with UFP+ozone. Maximum MSNA during Valsalva phase IIb was similar. Yet, with UFP+ozone plasma norepinephrine concentrations were significantly increased with concomitant reduction in the dihydroxyphenylglycol (DHPG)/norepinephrine ratio. Respiratory sinus arrhythmia and Valsalva ratio were unaffected by experimental air pollution.ConclusionExposure to ultrafine particles with or without ozone does not elicit clinically relevant changes in central sympathetic or parasympathetic activity in healthy older subjects. The paradoxical norepinephrine increase with UFP+ozone may be explained by reduced peripheral norepinephrine uptake and metabolism.Support or Funding InformationMM was funded by a grant from the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG, awarded to JJ: JO 284/8‐1). The German Aerospace Center (DLR) supported JT, KH, and MM (50 WB1117, 50WB1517).

Sympathoadrenal activation and endotheliopathy are drivers of hypocoagulability and hyperfibrinolysis in trauma: A prospective observational study of 404 severely injured patients.

One third of severely injured patients present with a laboratory-based diagnosis of coagulopathy. This study investigated clinical and biomarker profile of patients with rapid thrombelastography (rTEG) coagulopathy, hypothesizing that sympathoadrenal activation and endothelial damage were drivers of this condition. Prospective observational study of 404 trauma patients admitted to a Level 1 US Trauma Center. Patients with admission rTEG and plasma measurements of catecholamines (adrenaline, noradrenaline) and biomarkers reflecting endothelial activation/damage (syndecan-1, thrombomodulin, sE-selectin, sVE-cadherin, nucleosomes) were included. Demography, injury type/severity, physiology, treatment, and inhospital mortality were recorded. Patients had a median Injury Severity Score (ISS) of 17, 73% from blunt injury. One third (35%) of the patients had rTEG coagulopathy, which was associated with higher plasma adrenaline, syndecan-1, and nucleosomes (all <0.05), higher transfusion requirements and higher early (<24 hours, 9.3% vs. 2.5%) and late (28 days, 23.8% vs. 13.4%) mortality. By adjusted linear regression analyses, high plasma adrenaline, sVE-cadherin, and syndecan-1 (reflecting sympathoadrenal activation and endothelial cell junction and glycocalyx damage) along with male sex, high ISS, low platelet count and prehospital red blood cell transfusion were independently associated with hypocoagulable rTEG, whereas prehospital plasma and sE-selectin (reflecting endothelial activation) were independently associated with more hypercoagulable rTEG. In this cohort of severely injured trauma patients, rTEG coagulopathy was associated with sympathoadrenal activation, endotheliopathy, and excess mortality. High adrenaline and biomarkers reflecting endothelial cell junction and glycocalyx damage were independently associated with hypocoagulability and hyperfibrinolysis. These findings support that sympathoadrenal activation and endotheliopathy contribute to trauma-induced coagulopathy and warrants further studies of endothelial repair management. Prognostic, Level III.

Determination of urine catecholamines and metanephrines by reversed-phase liquid chromatography-tandem mass spectrometry

The measurement of urine catecholamine and metanephrine concentrations is important for biochemical screening and diagnosis of pheochromocytoma. The goal of this work was to develop a simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determining catecholamines and metanephrines in urine to replace an existing liquid chromatographic method using electrochemical detection. Urine samples were prepared using Oasis weak-cation-exchange cartridges. The eluate was analyzed on an Agilent ZORBAX Eclipse Plus Phenyl-Hexyl column in 3 min. Adrenaline, noradrenaline, dopamine, metanephrine, normetanephrine, and their deuterated internal standards were monitored in positive electrospray ionization mode by multiple reaction monitoring (MRM). No evidence of ion suppression was observed. The assay was linear up to 5μmol/L for adrenaline, 5μmol/L for noradrenaline, 6.1μmol/L for dopamine, 5.6μmol/L for metanephrine, and 34.6μmol/L for normetanephrine, with lower limits of quantification of 5, 5, 12, 6 and 7 nmol/L, respectively. The intra-day and inter-day precisions for all analytes ranged from 0.59% to 4.64% and 1.98% to 4.80%, respectively. External quality assurance samples were assayed and showed excellent agreement with the target values. This simple method provides an improved assay for determining urine catecholamines and metanephrines.