Seven genomic subtypes of chronic fatigue syndrome/myalgic encephalomyelitis: a detailed analysis of gene networks and clinical phenotypes

AIM

Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is a multisystem disease, the pathogenesis of which remains undetermined. The authors have recently reported a study of gene expression that identified differential expression of 88 human genes in patients with CFS/ME. Clustering of quantitative PCR (qPCR) data from patients with CFS/ME revealed seven distinct subtypes with distinct differences in Medical Outcomes Survey Short Form-36 scores, clinical phenotypes and severity.

METHODS

In this study, for each CFS/ME subtype, those genes whose expression differed significantly from that of normal blood donors were identified, and then gene interactions, disease associations and molecular and cellular functions of those gene sets were determined. Genomic analysis was then related to clinical data for each CFS/ME subtype.

RESULTS

Genomic analysis revealed some common (neurological, haematological, cancer) and some distinct (metabolic, endocrine, cardiovascular, immunological, inflammatory) disease associations among the subtypes. Subtypes 1, 2 and 7 were the most severe, and subtype 3 was the mildest. Clinical features of each subtype were as follows: subtype 1 (cognitive, musculoskeletal, sleep, anxiety/depression); subtype 2 (musculoskeletal, pain, anxiety/depression); subtype 3 (mild); subtype 4 (cognitive); subtype 5 (musculoskeletal, gastrointestinal); subtype 6 (postexertional); subtype 7 (pain, infectious, musculoskeletal, sleep, neurological, gastrointestinal, neurocognitive, anxiety/depression).

CONCLUSION

It was particularly interesting that in the seven genomically derived subtypes there were distinct clinical syndromes, and that those which were most severe were also those with anxiety/depression, as would be expected in a disease with a biological basis.

D-Cycloserine and performance under different states of anxiety in healthy volunteers

RATIONALE

There is interest in the development of augmentation therapy in the treatment of anxiety disorders. Recent publications have shown that D-cycloserine can benefit exposure therapy in a group of acrophobic (height phobic) subjects and in patients with social anxiety disorder. These studies were based on the animal data suggesting that drugs acting to enhance glutamate function may be developed to accelerate the behavioural treatment of anxiety disorders. Perhaps by enhancing glutamate/N-methyl-D-aspartate receptor function, learning is thus enhanced. This study examines the effects of D-cycloserine 50 mg on a task that involves learning. We manipulated anxiety levels to model the effects of high anxiety.

OBJECTIVES

To evaluate performance and learning, we used the Manikin task. Two groups of 24 healthy volunteers participated in a double-blind, placebo-controlled study. One group received the inhalation of CO(2) 7.5% to model high anxiety, and the second group received air to represent lower anxiety. Subjects received D-cycloserine 50 mg or placebo, and the Manikin task was performed during the gas inhalation.

RESULTS

There were significant differences in the group inhaling air, but not CO(2), with the D-cycloserine group showing an increase in correct responses. This difference was apparent at several time blocks during the 20-min task. These findings were supported by subjective measures in that participants who received D-cycloserine reported that the task was easier.

CONCLUSIONS

We have shown that at lower anxiety levels, D-cycloserine 50 mg improved the performance of this challenging visuospatial cognitive task. This increase in performance was not seen when anxiety was higher, and D-cycloserine did not appear to increase subjective anxiety. These data lend support to the use of D-cycloserine and related glutamate enhancers as cognitive modulators and suggest that the actions of D-cycloserine are not simply related to increased arousal or anxiety.

Evidence-based guidelines for management of attention-deficit/hyperactivity disorder in adolescents in transition to adult services and in adults: recommendations from the British Association for Psychopharmacology

Attention-deficit/hyperactivity disorder (ADHD) is an established diagnosis in children, associated with a large body of evidence on the benefits of treatment. Adolescents with ADHD are now leaving children's services often with no readily identifiable adult service to support them, which presents problems as local pharmacy regulations often preclude the prescription of stimulant drugs by general practitioners (GPs). In addition, adults with ADHD symptoms are now starting to present to primary care and psychiatry services requesting assessment and treatment. For these reasons, the British Association for Psychopharmacology (BAP) thought it timely to hold a consensus conference to review the body of evidence on childhood ADHD and the growing literature on ADHD in older age groups. Much of this initial guidance on managing ADHD in adolescents in transition and in adults is based on expert opinion derived from childhood evidence. We hope that, by the time these guidelines are updated, much evidence will be available to address the many directions for future research that are detailed here.

Current research priorities in chronic fatigue syndrome/myalgic encephalomyelitis: disease mechanisms, a diagnostic test and specific treatments

Chronic fatigue syndrome (CFS) is an illness characterised by disabling fatigue of at least 6 months duration, which is accompanied by various rheumatological, infectious and neuropsychiatric symptoms. A collaborative study group has been formed to deal with the current areas for development in CFS research--namely, to develop an understanding of the molecular pathogenesis of CFS, to develop a diagnostic test and to develop specific and curative treatments. Various groups have studied the gene expression in peripheral blood of patients with CFS, and from those studies that have been confirmed using polymerase chain reaction (PCR), clearly, the most predominant functional theme is that of immunity and defence. However, we do not yet know the precise gene signature and metabolic pathways involved. Currently, this is being dealt with using a microarray representing 47,000 human genes and variants, massive parallel signature sequencing and real-time PCR. It will be important to ensure that once a gene signature has been identified, it is specific to CFS and does not occur in other diseases and infections. A diagnostic test is being developed using surface-enhanced, laser-desorption and ionisation-time-of-flight mass spectrometry based on a pilot study in which putative biomarkers were identified. Finally, clinical trials are being planned; novel treatments that we believe are important to trial in patients with CFS are interferon-beta and one of the anti-tumour necrosis factor-alpha drugs.

Pharmacotherapy of anxiety

The pharmacological treatment of anxiety has a long and chequered history, and recent years have seen a rich development in the options available to prescribers. Most of the currently used anxiolytic agents act via monoaminergic (chiefly serotonin) or amino acid (GABA or glutamate) neurotransmitters, and this chapter describes the pharmacology of the major drug groups. Clinical applications are discussed with respect to the five major anxiety disorders, as well as simple phobia and depression with concomitant anxiety. Prospective future developments in the field are considered.

GABA-benzodiazepine receptor function in alcohol dependence: a combined 11C-flumazenil PET and pharmacodynamic study

RATIONALE

Gamma-aminobutyric acid (GABA)-benzodiazepine receptor function is hypothesised to be reduced in alcohol dependence.

OBJECTIVES

We used positron emission tomography (PET) with [11C]flumazenil, a non-selective tracer for brain GABA-benzodiazepine (GABA-BDZ) receptor binding, to determine in vivo the relationship between BDZ receptor occupancy by an agonist, midazolam, and its functional effects.

METHODS

Abstinent male alcohol dependent subjects underwent [11C]flumazenil PET to measure occupancy of BDZ receptors by midazolam whilst recording its pharmacodynamic effects on behavioural and physiological measures. Rate constants describing the exchange of [11C]flumazenil between the plasma and brain compartments were derived from time activity curves.

RESULTS

A 50% reduction in electroencephalography (EEG)-measured sleep time was seen in the alcohol dependent group despite the same degree of occupancy by midazolam as seen in the control group. The effects of midazolam on other measures of benzodiazepine receptor function, increasing EEG beta1 power and slowing of saccadic eye movements, were similar in the two groups. No differences in midazolam or flumazenil metabolism were found between the groups.

CONCLUSIONS

In summary, our study suggests that alcohol dependence in man is associated with a reduced EEG sleep response to the benzodiazepine agonist, midazolam, which is not explained by reduced BDZ receptor occupancy, and is consistent with reduced sensitivity in this measure of GABA-BDZ receptor function in alcohol dependence. The lack of change in other functional measures may reflect a differential involvement of particular subtypes of the GABA-BDZ receptor.

Using sleep to evaluate comparative serotonergic effects of paroxetine and citalopram

BACKGROUND

SSRIs suppress rapid eye movement (REM) sleep, probably by increasing serotonin in the brainstem, and also increase sleep fragmentation. Although in the UK, paroxetine (PAR) and citalopram (CIT) have recommended doses of 20 mg/day for the treatment of depression, the recommended dose of CIT in USA is higher (40 mg). If similar doses of PAR and CIT have similar effects on central serotonin then they should have similar effects on sleep measures in volunteers.

METHOD

This was a randomised, double blind placebo controlled crossover study in 12 healthy volunteers. Subjects took PAR 20 mg mane, CIT 20 mg mane or placebo mane for 3 days and sleep was recorded overnight at home on the third night. Standard measures of sleep were derived.

RESULTS

REM sleep was significantly suppressed and sleep fragmentation increased by both drugs. Measures of REM sleep and sleep continuity previously found to be altered by SSRIs were considered together and compared with placebo as a 'serotonin response'; this was significantly greater in the PAR group.

CONCLUSIONS

Sleep effects typical of SSRIs were greater with PAR 20 mg/day than CIT 20 mg/day, suggesting greater effects on 5HT uptake blockade.

Invited review: the evolution of antidepressant mechanisms

Present antidepressants are all descendents of the serendipitous findings in the 1950s that the monoamine oxidase inhibitor iproniazid and the tricyclic antidepressant imipramine were effective antidepressants. The identification of their mechanism of action, and those of reserpine and amphetamine, in the 1960s, led to the monoamine theories of depression being postulated; first, with noradrenaline then 5-hydroxytryptamine being considered the more important amine. These monoamine theories of depression predominated both industrial and academic research for four decades. Recently, in attempts to design new drugs with faster onsets of action and more universal therapeutic action, downstream alterations common to current antidepressants are being examined as potential antidepressants. Additionally, the use of animal models has identified a number of novel targets some of which have been subjected to clinical trials in humans. However, monoamine antidepressants remain the best current medications and it may be some time before they are dislodged as the market leaders.

[On the role of GABA in anxiety and depression]

Data on the role of gamma-aminobutyric acid (GABA) in pathogenesis of anxiety and depression are critically assessed. Clinical and experimental results indicative of an important role of GABA as the neurotransmitter involved in these mental states and their integration within a common pathogenic process are considered. The general neurochemical, pharmacological, and neurophysiological aspects of anxiety and depression are analyzed in the context of GABAergic system involvement in this process and the possibility of using GABAergic agents for the therapy of various related disorders.

The role of serotonin in panic: evidence from tryptophan depletion studies

There has been growing interest in the role of serotonin (5-hydroxytryptamine, 5-HT) in anxiety, including pathological states such as panic disorder. The technique of tryptophan depletion (TD), which causes an acute, temporary and reversible reduction in brain 5-HT levels, is a useful minimally invasive paradigm to aid the research of the role of 5-HT in various disorders. This review discusses the evidence supporting the hypothesis that 5-HT function is of importance in the neurobiology of panic disorder and considers in more detail how our understanding has been influenced by work using the technique of TD. Possible avenues for future research are also discussed.

Evaluation of actigraphy and automated telephoned questionnaires to assess hypnotic effects in insomnia

This study aimed to explore new methodologies in insomnia research, namely whether actigraphy was suitable to show hypnotic effects over weeks in insomnia, and to compare an automated method of questionnaire data collection with traditional methods. Thirty-eight insomniacs took part in a 5-week, double-blind, placebo-controlled study of the effects of 2 weeks of administration of temazepam 20 mg on sleep. Outcome measures were actigraphy and daily St Mary's Hospital Sleep Questionnaires (SMHSQ). Actigraphy was performed using Actiwatch (CNT) and analysed using both the automated Actiwatch sleep analysis software and non-parametric analysis of rest-activity rhythms. The questionnaires were administered as straightforward pencil-and-paper for half of the time and an automated telephoned system for the other half. The experimental paradigm allowed within-subject comparison of traditional and automated data collection, both on and off drug. Actigraphy showed a high degree of inter-subject variability but, nevertheless, some sleep variables (Fragmentation Index, Actual Sleep Time %) showed significant improvement during drug treatment, and Sleep Efficiency and Actual Sleep Time were significantly worsened during the first post-drug week. Nonparametric circadian rhythm analysis showed no significant effect. Subjective data from the SMHSQ showed significant drug effects and there was no significant difference in scores between the automated and pencil-and-paper methods; automated data collection was slightly more acceptable to patients and minimized data entry and management. Effect sizes using within-subject and between-subject comparisons were calculated for the subjective and objective measures to inform future studies

Novel Ligands for the Investigation of Imidazoline Receptors and Their Binding Proteins

New ligands for imidazoline receptors are described so that these receptors can be more fully explored and understood. BU224, (2-(4,5-dihydroimidaz-2-yl)-quinoline, shows high affinity and is selective for the imidazoline-2 (I(2)) class of receptors. BU224 was tested in the rat Porsolt forced swim paradigm where it was found to decrease time spent immobile and increase the time spent swimming, consistent with an antidepressant profile. BU224 was tritiated and, in radioligand binding studies, was found to label a single population of saturable sites with high affinity. In vitro brain autoradiography with [(3)H]BU224 also showed a pattern of distribution similar to the known labeling of I(2) receptors. A new series of four 2BFI (2-(benzofuranyl)-2-imidazoline) derivatives were investigated as potential ligands for imaging brain I(2) receptors using positron emission tomography (PET). At least two, BU20012 and BU20013, retained high affinity and moderate selectivity and penetrated the brain when administered peripherally in the mouse. 2BFI has undergone the Mannich reaction to immobilized diaminodipropyl amine to fabricate an affinity column, which was used to isolate a protein from rabbit brain; this protein was sequenced and identified as the enzyme creatine kinase.

In Vivo Estimation of Imidazoline2 Binding Site Turnover

Turnover of imidazoline(2) (I(2)) binding sites in the mouse and rat brain has been measured following an acute intravenous dose of BU99006. This ligand selectively and irreversibly knocks out I(2) sites, as defined by [(3)H]2BFI binding. Recovery was measured using radioligand binding and autoradiography to determine global and regional changes in I(2) density. The density of I(2) sites in brain recovered from BU99006 treatment with a half-life of 2.1 hours in mice and 4.3 hours in rats. Monoamine oxidase (MAO) activity and MAO binding density were unaltered in the brains of BU99006-treated animals. These data suggest that the I(2) site that reacts with BU99006 recovers rapidly and is independent of MAO.

Relationship Between Imidazoline2 Sites and Monoamine Oxidase

I(2) site-selective compounds are known to interact with and inhibit monoamine oxidase (MAO), but it remains unclear as to whether this interaction occurs through an allosteric or competitive interaction. This study used the new selective, irreversible I(2) ligand BU99006, to clarify the relationship between MAO and the I(2) binding sites (I(2)-BS). Results demonstrate that irreversible binding of BU99006 to rat brain membranes does not inhibit the enzyme or interfere with its interaction with other imidazoline enzyme inhibitors. This finding suggests that the I(2) sites that react with BU99006 are not those implicated in MAO inhibition and points to the existence of at least two distinct I(2) binding proteins.

Investigation of the Affinities of Two New b-Carbolines for Rat Brain Imidazoline2 Receptors

The beta-carbolines are possible endogenous ligands and modulators of the imidazoline binding sites (I-BSs). Relatively little is known about this class of compound and its interaction with the I-BS. Presented here are the binding data for two aryl ring substituted dihydro-beta-carbolines at the imidazoline(2) binding site (I(2)-BS) and alpha(2)-adrenoceptor: BG-326 (5-bromo-4,9-dihydro-3H-b-carboline) and BG-350 (5-methoxy-4,9-dihydro-3H-b-carboline). Both compounds show good affinity and selectivity for the I(2)-BS.

Endogenous -Carbolines as Clonidine-Displacing Substances

Endogenous beta-carbolines, such as harmane, are known to occur in mammalian species including humans. Radioligand binding studies have revealed that certain beta-carbolines display high affinity for both I(1) and I(2) imidazoline-binding sites (IBS). Functional studies have shown that the beta-carboline harmane elicits many characteristics expected of an endogenous ligand IBS. This article discusses the evidence relating to beta-carbolines as endogenous ligands and presents a case for harmane and related compounds as endogenous ligands for IBS.

Identification of an I2 Binding Protein From Rabbit Brain

Imidazoline-2 binding proteins exist as a heterogeneous population. The aim of this study was to isolate and identify I(2) binding proteins from rabbit brain using an affinity column synthesized with a highly selective I(2) ligand, 2-(2-benzofuranyl)2-imidazoline (2BFI). The results revealed an approximately 45-kD protein to be brain creatine kinase (EC 2.7.3.2). [(3)H]-2BFI (5nM) was able to bind specifically to the purified enzyme. This study has identified brain creatine kinase as a novel I(2) binding protein.

Initial Evaluation of Novel Selective Ligands for Imidazoline2 Receptors in Rat Whole Brain

Indazim, the indazole analogue of 2BFI, and four methyl-substituted analogues were tested for their affinity at the imidazoline(2) binding site (I(2)-BS), and this affinity was compared with their affinity at the alpha(2)-adrenoceptor to determine their structure, affinity relationship, and selectivity at the I(2)-BS. These studies showed that these ligands were highly selective for the I(2)-BS compared with 2BFI and that substitution at the 4 and 7 positions increased affinity without affecting selectivity.

BU98008, a Highly Selective Imidazoline1-Receptor Ligand

BU98008 (1-(4, 5-dihydro-1H-imidazol-2-yl)isoquinoline) is a novel isoquinoline derivative. Radioligand binding studies revealed it had high affinity for the I(1) receptor in rat kidney membranes but low affinity for the I(2) binding site and alpha(2)-adrenoceptor in rat brain membranes. Further evaluation of BU98008 in vivo revealed no effect on blood pressure following peripheral administration. These preliminary data suggest BU98008 may be an antagonist at I(1) receptors. Further evaluation following central administration must be performed before a hypotensive action can be excluded.