Albrecht Eisert

Effects of tryptophan depletion on reactive aggression and aggressive decision‐making in young people with ADHD

Kötting WF, Bubenzer S, Helmbold K, Eisert A, Gaber TJ, Zepf FD. Effects of tryptophan depletion on reactive aggression and aggressive decision‐making in young people with ADHD.

Effects of serotonin depletion on punishment processing in the orbitofrontal and anterior cingulate cortices of healthy women

Diminished synthesis of the neurotransmitter serotonin (5-HT) has been linked to disrupted impulse control in aversive contexts. However, the neural correlates underlying a serotonergic modulation of female impulsivity remain unclear. The present study investigated punishment-induced inhibition in healthy young women. Eighteen healthy female subjects (aged 20-31) participated in a double-blinded, counterbalanced, placebo-controlled, within subjects, repeated measures study. They were assessed on two randomly assigned occasions that were controlled for menstrual cycle phase. In a randomized order, one day, acute tryptophan depletion (ATD) was used to reduce 5-HT synthesis in the brain. On the other day, participants received a tryptophan-balanced amino acid load (BAL) as a control condition. Three hours after administration of ATD/BAL, neural activity was recorded during a modified Go/No-Go task implementing reward or punishment processes using functional magnetic resonance imaging (fMRI). Neural activation during No-Go trials in punishment conditions after BAL versus ATD administration correlated positively with the magnitude of central 5-HT depletion in the ventral and subgenual anterior cingulate cortices (ACC). Furthermore, neural activation in the medial orbitofrontal cortex (mOFC) and the dorsal ACC correlated positively with trait impulsivity. The results indicate reduced neural sensitivity to punishment after short-term depletion of 5-HT in brain areas related to emotion regulation (subgenual ACC) increasing with depletion magnitude and in brain areas related to appraisal and expression of emotions (mOFC and dorsal ACC), increasing with trait impulsivity. This suggests a serotonergic modulation of neural circuits related to emotion regulation, impulsive behavior, and punishment processing in females.

L-Carnitine Ameliorates L-Asparaginase-Induced Acute Liver Toxicity in Steatotic Rat Livers

Background: Chemotherapy with <smlcap>L</smlcap>-asparaginase is associated with hepatotoxicity resulting in organ dysfunction in patients with preexisting liver disorders. This study investigated the protective effect of <smlcap>L</smlcap>-carnitine during chemotherapy in a steatotic rat liver model. Methods: Livers from nonsteatotic and steatotic rats were tested in an isolated liver reperfusion model adding <smlcap>L</smlcap>-asparaginase and <smlcap>L</smlcap>-carnitine to the reperfusate. Portal venous pressure (PVP), hepatic oxygen consumption, aspartate aminotransferase, lactate dehydrogenase, glutamate dehydrogenase and α-glutathione S-transferase levels were assessed. Further histopathological analysis was performed and cytotoxicity was verified in vitro. Results:<smlcap>L</smlcap>-Asparaginase induced toxicity in fatty livers whereas low toxicity was observed in normal livers. <smlcap>L</smlcap>-Carnitine induced a decline in PVP and oxygen consumption, and reduced parenchymal and mitochondrial damage in fatty livers. Cytotoxicity of <smlcap>L</smlcap>-asparaginase was not impaired by the presence of <smlcap>L</smlcap>-carnitine. Conclusions: Our study emphasizes the potential of <smlcap>L</smlcap>-carnitine to reduce <smlcap>L</smlcap>-asparaginase-induced hepatotoxicity in patients with preexisting liver disorders.

Hypercholesterolemia and its association with enhanced stem cell mobilization and harvest after high-dose cyclophosphamide+G-CSF.

High-dose chemotherapy with autologous peripheral blood SCT is a common treatment option in several hematological and non-hematological malignancies. So far, prediction of successful stem cell mobilization and harvest is limited. Just recently, hypercholesterolemia was shown to increase mobilization of hematopoietic progenitor cells into the peripheral circulation in mice. On the basis of these results, we performed a retrospective multivariate analysis incorporating a variety of clinical parameters in 83 patients following high-dose cyclophosphamide+G-CSF treatment. Interestingly, we found a significant positive correlation between stem cell mobilization and harvest for plasma cholesterol and lactate dehydrogenase (LDH) only. Patients with hypercholesterolemia showed a substantially higher median peripheral blood CD34+-peak (126 vs 47/μL, P=0.003), higher median number of harvested CD34+-cells/kg (9.6 vs 7.4 × 106/kg, P<0.001) and a sufficient number for at least one SCT in a remarkably higher proportion (84.9 vs 52.9%, P=0.003) compared with patients with normal cholesterol levels.

Change in electrodermal activity after acute tryptophan depletion associated with aggression in young people with attention deficit hyperactivity disorder (ADHD)

Abstract We investigated the impact of acute tryptophan depletion (ATD) and reduced brain serotonin synthesis on physiological arousal in 15 young people with ADHD participating in an aggression-inducing game. ATD was not associated with altered physiological arousal, as indexed by electrodermal activity (EDA). Baseline aggression was negatively correlated with the mean ATD effect on EDA. In accordance with the low arousal theory related to aggressive behavior, subjects with reduced physiological responsiveness/lower electrodermal reactivity to ATD tended to display elevated externalizing behavior.

Cortico-limbic connectivity in MAOA-L carriers is vulnerable to acute tryptophan depletion

A gene–environment interaction between expression genotypes of the monoamine oxidase A (MAOA) and adverse childhood experience increases the risk of antisocial behavior. However, the neural underpinnings of this interaction remain uninvestigated. A cortico‐limbic circuit involving the prefrontal cortex (PFC) and the amygdala is central to the suppression of aggressive impulses and is modulated by serotonin (5‐HT). MAOA genotypes may modulate the vulnerability of this circuit and increase the risk for emotion regulation deficits after specific life events. Acute tryptophan depletion (ATD) challenges 5‐HT regulation and may identify vulnerable neuronal circuits, contributing to the gene–environment interaction.

Effects of a short-term reduction in brain serotonin synthesis on the availability of the soluble leptin receptor in healthy women

Serotonin (5-HT) and the hormone leptin have been linked to the underlying neurobiology of appetite regulation with evidence coming from animal and cellular research, but direct evidence linking these two pathways in humans is lacking. We examined the effects of reduced brain 5-HT synthesis due to acute tryptophan depletion (ATD) on levels of soluble leptin receptor (sOb-R), the main high-affinity leptin binding protein, in healthy adults using an exploratory approach. Women, but not men, showed reduced sOb-R concentrations after ATD administration. With females showing reduced baseline levels of central 5-HT synthesis compared to males diminished brain 5-HT synthesis affected the leptin axis through the sOb-R in females, thereby potentially influencing their vulnerability to dysfunctional appetite regulation and co-morbid mood symptoms.

Acute tryptophan depletion – converging evidence for decreasing central nervous serotonin synthesis in rodents and humans

We read the comment provided by Simon N. Young (1) on the articles (2–5) in the special issue of Acta Psychiatrica Scandinavica (6) dealing with the acute tryptophan depletion (ATD) methodology with great interest. ATD is a pharmacological method designed to lower central nervous system (CNS) synthesis of the neurotransmitter serotonin (5-HT) for a brief period that can also be used in both adults and young people (7). As 5-HT plays an important role in behavioral inhibition (8– 10) and other important processes in the brain (11–14), ATD is a translational method to study the effects of changes in CNS 5-HT function that has particular value, as discussed at a recent symposium dedicated to the role of 5-HT in psychopathology (7–11, 15). The author of this particular comment expressed concerns that ATD might not always decrease CNS 5-HT synthesis and that the lack of the amino acid histidine (HIS) in the depletion mixtures used might influence the results due to the potential role of 5-HT–histamine interactions in any observed outcome. We appreciate the comments made and would like to address the issues raised, point by point. Young argues that ‘there is no evidence that ATD does always decrease serotonin release (in humans)’. This is contradictory by decades of work in rodents and in humans demonstrating that ATD can decrease 5-HT synthesis and release in rodents and lower 5-HIAA in human CSF (16–19). In one of our laboratories, the acute tryptophan depletion (ATD) protocol termed ‘Moja-De’ has been shown to decrease 5-HT release in rodents (20, 21) and to lower tryptophan (TRP) comparably in humans (22), suggesting that this mixture successfully decreases 5-HT synthesis as postulated. While some experiments (23) fail to detect changes in central 5-HT function after ATD, this is the exception rather than the rule in published studies. The author of this comment was also concerned that there would be regional variations in the inhibition of serotonin function. This is logical and consistent with published data on the effects of Moja-De ATD in mice. Mouse studies indicated that depletion of TRP was comparable across different brain areas but that the extent of decrease in 5-HIAA varied by region (20, 21). Regional release of 5-HT is controlled by a combination of cell firing including regionally selective input, the concentration of 5-HT1b receptors on terminals, the amount of tryptophan hydroxylase, and many other factors (24). However, there is no evidence that 5-HT release happens only in selective regions, but we agree the magnitude of ATD effects on release is likely to vary between regions despite comparable depletion of TRP. As regards potential interactions between 5-HT and histamine, we agree that measurement of histidine after depletion of TRP or any other formula lacking HIS is of interest. Young has questioned the results of ATD experiments in which HIS was not included, stating that ‘histidine is an essential amino acid’. However, the essentiality of this amino acid is not clearly established (25). It has been reported that HIS was not necessary for the maintenance of nitrogen balances in short-term (26, 27). Kriengsunyos et al. (28) observed after a long-term histidine depletion administered to healthy adults that there were no effects on the protein metabolism (urinary nitrogen excretion and nitrogen balance). They suggested that the essentiality of this amino acid in healthy adults is still unclear as there are some components that may serve as sources of HIS, although the data they reported indicate that this amount may not be enough for maintain the HIS pool. The other concern expressed by Young was that effects of ATD could reflect disruption of a histamine–serotonin interaction, as ATD would cause a dramatic decrease in histamine synthesis. This is possible, as it is well established that the neurotransmitter histamine is formed from HIS (29), and histamine turnover seems to occur faster than other biogenic amines, such as norepinephrine or 5-HT (30). Therefore, in the absence of HIS, competition from the amino acid mixtures could indeed lower histamine production. However, neither the control nor the ATD mixture in most studies contains histidine, and so histamine would not be differentially affected by the ATD mixture, but should be comparably depleted in both control and ATD mixtures. Nevertheless, it is possible that some interaction between histamine depletion and 5-HT depletion could have behavioral effects. Unfortunately, no behavioral effects of histamine depletion have been clearly established in the literature. A study by Young and his collaborators of HIS depletion effects on sensory and motor behavior in healthy adults (31) showed that HIS in plasma decreased 20% and the ratio HIS/ΣLNAA decreased 59%, but there were no behavioral effects of this depletion. Finally, we disagree with the statement that ‘the relevance of such animal studies to the far more complex human brain is uncertain’. It is well known that validation of translational methods has allowed modeling many aspects of the neuropsychopathology with the use of appropriate animal models, the majority of them throughout the use of rodents (32, 33). Translation of behavioral findings is challenging, due to limits in extrapolating simple behavioral tasks in rodents to sophisticated behaviors in humans. However, biochemical studies of ATD effects in humans and rodents have shown considerable concordance. For example, our studies in humans (5, 22) have been validated in mice (20, 21), consistent with the field as described above (16–19). As Dr. Young points out, detailed anatomic studies of 5-HT synthesis in the human brain are technologically demanding and rarely conducted. However, the concordance between the dependent measures that can be collected in humans (CSF 5-HIAA for example) and comparable measures in rodents (tissue 5-HIAA content, 5-HT and 5-HIAA content in microdialysate) supports the concordance of findings after ATD in humans. In summary, there is convincing and converging evidence that ATD decreases 5-HT synthesis in the brain in both rodents and humans. Interactions between 5-HT and

Clinical decision support systems differ in their ability to identify clinically relevant drug interactions of immunosuppressants in kidney transplant patients

In kidney transplant patients, clinically relevant drug–drug interactions (DDIs) with immunosuppressants potentially lead to serious adverse drug events (ADEs). The aim of this study was (i) to show that five clinical decision support systems (CDSSs) differ in their ability to identify clinically relevant potential DDIs (pDDIs) of immunosuppressants in kidney transplant patients and (ii) to compare CDSSs in terms of their ability to identify clinically relevant pDDIs in this context.

Incidence and Severity of Prescribing Errors in Parenteral Nutrition for Pediatric Inpatients at a Neonatal and Pediatric Intensive Care Unit

Objectives Pediatric inpatients are particularly vulnerable to medication errors (MEs), especially in highly individualized preparations like parenteral nutrition (PN). Aside from prescribing via a computerized physician order entry system (CPOE), we evaluated the effect of cross-checking by a clinical pharmacist to prevent harm from PN order errors in a neonatal and pediatric intensive care unit (NICU/PICU). Methods The incidence of prescribing errors in PN in a tertiary level NICU/PICU was surveyed prospectively between March 2012 and July 2013 (n = 3,012 orders). A pharmacist cross-checked all PN orders prior to preparation. Errors were assigned to seven different error-type categories. Three independent experts from different academic tertiary level NICUs judged the severity of each error according to the National Coordinating Council for Medication Error Reporting and Prevention (NCC MERP) Index (categories A–I). Results The error rate was 3.9% for all 3,012 orders (118 prescribing errors in 111 orders). 77 (6.0%, 1,277 orders) errors occurred in the category concentration range, all concerning a relative overdose of calcium gluconate for peripheral infusion. The majority of all events (60%) were assigned to categories C and D (without major harmful consequences) while 28% could not be assigned due to missing majority decision. Potential harmful consequences requiring interventions (category E) could have occurred in 12% of assessments. Conclusion Next to systematic application of clinical guidelines and prescribing via CPOE, order review by a clinical pharmacist is still required to effectively reduce MEs and thus to prevent minor and major adverse drug events with the aim to enhance medication safety.