Urinary 4-hydroxy-3-methoxyphenylglycol is not a predictor for clinical response to amitriptyline in depressive illness

Biomarkers as predictors of treatment response to tricyclic antidepressants in major depressive disorder: A systematic review

Tricyclic antidepressants (TCAs) are frequently prescribed in case of non-response to first-line antidepressants in Major Depressive Disorder (MDD). Treatment of MDD often entails a trial-and-error process of finding a suitable antidepressant and its appropriate dose. Nowadays, a shift is seen towards a more personalized treatment strategy in MDD to increase treatment efficacy. One of these strategies involves the use of biomarkers for the prediction of antidepressant treatment response. We aimed to summarize biomarkers for prediction of TCA specific (i.e. per agent, not for the TCA as a drug class) treatment response in unipolar nonpsychotic MDD. We performed a systematic search in PubMed and MEDLINE. After full-text screening, 36 papers were included. Seven genetic biomarkers were identified for nortriptyline treatment response. For desipramine, we identified two biomarkers; one genetic and one nongenetic. Three nongenetic biomarkers were identified for imipramine. None of these biomarkers were replicated. Quality assessment demonstrated that biomarker studies vary in endpoint definitions and frequently lack power calculations. None of the biomarkers can be confirmed as a predictor for TCA treatment response. Despite the necessity for TCA treatment optimization, biomarker studies reporting drug-specific results for TCAs are limited and adequate replication studies are lacking. Moreover, biomarker studies generally use small sample sizes. To move forward, larger cohorts, pooled data or biomarkers combined with other clinical characteristics should be used to improve predictive power.

Depressive-like behavior observed with a minimal loss of locus coeruleus (LC) neurons following administration of 6-hydroxydopamine is associated with electrophysiological changes and reversed with precursors of norepinephrine

Depression is a common co-morbid condition most often observed in subjects with mild cognitive impairment (MCI) and during the early stages of Alzheimer's disease (AD). Dysfunction of the central noradrenergic nervous system is an important component in depression. In AD, locus coeruleus (LC) noradrenergic neurons are significantly reduced pathologically and the reduction of LC neurons is hypothesized to begin very early in the progression of the disorder; however, it is not known if dysfunction of the noradrenergic system due to early LC neuronal loss is involved in mediating depression in early AD. Therefore, the purpose of this study was to determine in an animal model if a loss of noradrenergic LC neurons results in depressive-like behavior. The LC noradrenergic neuronal population was reduced by the bilateral administration of the neurotoxin 6-hydroxydopamine (6-OHDA) directly into the LC. Forced swim test (FST) was performed three weeks after the administration of 6-OHDA (5, 10 and 14 μg/μl), animals administered the 5 μg/μl of 6-OHDA demonstrated a significant increase in immobility, indicating depressive-like behavior. This increase in immobility at the 5 μg/μl dose was observed with a minimal loss of LC noradrenergic neurons as compared to LC neuronal loss observed at 10 and 14 μg/μl dose. A significant positive correlation between the number of surviving LC neurons after 6-OHDA and FST immobile time was observed, suggesting that in animals with a minimal loss of LC neurons (or a greater number of surviving LC neurons) following 6-OHDA demonstrated depressive-like behavior. As the 6-OHDA-induced loss of LC neurons is increased, the time spent immobile is reduced. Depressive-like behavior was also observed with the 5 μg/μl dose of 6-OHDA with a second behavior test, sucrose consumption. FST increased immobility following 6-OHDA (5 μg/μl) was reversed by the administration of a single dose of L-1-3-4-dihydroxyphenylalanine (DOPA) or l-threo-3,4-dihydroxyphenylserine (DOPS) prior to behavioral assessment. Surviving LC neurons 3 weeks after 6-OHDA (5 μg/μl) demonstrated compensatory changes of increased firing frequency, a more irregular firing pattern, and a higher percentage of cells firing in bursts. These results indicate that depressive-like behavior in mice is observed following the administration of 6-OHDA and the loss of LC noradrenergic neurons; however, the depressive-like behavior correlates positively with the number of surviving LC neurons with 6-OHDA administration. This data suggests the depression observed in MCI subjects and in the early stages of AD may due to the hypothesized early, minimal loss of LC neurons with remaining LC neurons being more active than normal.

Depression: The predisposing influence of stress

Aversive experiences have been thought to provoke or exacerbate clinical depression. The present review provides a brief survey of the stress-depression literature and suggests that the effects of stressful experiences on affective state may be related to depletion of several neurotransmitters, including norepinephrine, dopamine, and serotonin. A major element in determining the neurochemical changes is the organism's ability to cope with the aversive stimuli through behavioral means. Aversive experiences give rise to behavioral attempts to cope with the stressor, coupled with increased utilization and synthesis of brain amines to contend with environmental demands. When behavioral coping is possible, neurochemical systems are not overly taxed, and behavioral pathology will not ensue. However, when there can be no behavioral control over the stressful stimuli, or when the aversive experience is perceived as uncontrollable, increased emphasis is placed on coping through endogenous neurochemical mechanisms. Amine utilization increases appreciably and may exceed synthesis, resulting in a net reduction of amine stores, which in turn promotes or exacerbates affective disorder. The processes governing the depletions may be subject to sensitization or conditioning, such that exposure to traumatic experiences may have long-term repercussions when the organism subsequently encounters related stressful stimuli. With continued uncontrollable stimulation, adaptation occurs in the form of increased activity of synthetic enzymes, and levels of amines approach basal values. It is suggested that either the initial amine depletion provoked by aversive experiences or a dysfunction of the adaptive processes, resulting in persistent amine depletion, contributes to behavioral depression. Aside from the contribution of behavioral coping, several organismic, experiential, and environmental variables will influence the effects of aversive experiences on neurochemical activity, and may thus influence vulnerability to depression.

Organization of the stress system and its dysregulation in melancholic and atypical depression: high vs low CRH/NE states

Stress precipitates depression and alters its natural history. Major depression and the stress response share similar phenomena, mediators and circuitries. Thus, many of the features of major depression potentially reflect dysregulations of the stress response. The stress response itself consists of alterations in levels of anxiety, a loss of cognitive and affective flexibility, activation of the hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system, and inhibition of vegetative processes that are likely to impede survival during a life-threatening situation (eg sleep, sexual activity, and endocrine programs for growth and reproduction). Because depression is a heterogeneous illness, we studied two diagnostic subtypes, melancholic and atypical depression. In melancholia, the stress response seems hyperactive, and patients are anxious, dread the future, lose responsiveness to the environment, have insomnia, lose their appetite, and a diurnal variation with depression at its worst in the morning. They also have an activated CRH system and may have diminished activities of the growth hormone and reproductive axes. Patients with atypical depression present with a syndrome that seems the antithesis of melancholia. They are lethargic, fatigued, hyperphagic, hypersomnic, reactive to the environment, and show diurnal variation of depression that is at its best in the morning. In contrast to melancholia, we have advanced several lines of evidence of a down-regulated hypothalamic-pituitary adrenal axis and CRH deficiency in atypical depression, and our data show us that these are of central origin. Given the diversity of effects exerted by CRH and cortisol, the differences in melancholic and atypical depression suggest that studies of depression should examine each subtype separately. In the present paper, we shall first review the mediators and circuitries of the stress system to lay the groundwork for placing in context physiologic and structural alterations in depression that may occur as part of stress system dysfunction.

Divergent endocrine abnormalities in melancholic and atypical depression: clinical and pathophysiologic implications

Mediators of neuroendocrine and autonomic function seem to play important roles in the core symptoms of major depression. Although centrally directed corticotropin-releasing hormones and norepinephrine contribute to core symptoms such as alterations in anxiety, arousal, and mood, they also exert significant potentially clinically relevant effects on key processes that proceed in the periphery. Thus, the core clinical manifestations of major depression may represent a fraction of a complicated systemic illness that not only influences thought and feeling, but also the processes involved in premature cardiovascular disease, osteoporosis, and premature death. Subdividing patients with major depression into meaningful biologic subgroups will facilitate the elucidation of the mechanisms that underlie the central and peripheral manifestations of major depressive illness.

Is there a role for a pure noradrenergic drug in the treatment of depression?

Depression is thought to result from a dysfunction in the noradrenergic or serotonergic systems. The noradrenergic system appears to be associated with increased drive, whereas the serotonergic system relates more to changes in mood and it is possible that the different symptoms of depression may benefit from drugs acting mainly on one or other of the neurotransmitter systems. A series of studies has shown that interruption of serotonin synthesis compromises the efficacy of serotonin but not noradrenaline reuptake inhibitors, and interruption of noradrenaline synthesis compromises the efficacy of noradrenaline but not serotonin reuptake inhibitors (SSRIs). This suggests that the two classes of drugs owe their activity to functional changes in different neurotransmitter systems. Reboxetine represents a new class of drugs-the selective noradrenaline reuptake inhibitors (NARIs). It acts specifically at noradrenergic sites unlike the non-selective tricyclic antidepressants (TCAs). NARIs have a role in the treatment of depression, either alone or as adjunctive therapy.

Clinical significance of plasma levels of clomipramine, its hydroxylated and desmethylated metabolites: prediction of clinical outcome in mood disorders using discriminant analysis of therapeutic drug monitoring data

We measured the plasma concentrations of clomipramine and its metabolites, N-desmethylclompiramine, 8-hydroxy-N-desmethylclomipramine, 8-hydroxyclomipramine in 65 depressed patients with subtypes of DSM-III-R mood disorders receiving clomipramine hydrochloride. There were large interindividual variations in the concentrations of the parent and each of the metabolic compounds, though the overall correlations between drug concentrations and daily doses of clomipramine were highly significant. Metabolic ratios for both desmethylation and hydroxylation varied by 15-35-fold interindividually. Discriminant analysis of the data from drug concentrations and scores of Global Assessment of Functioning revealed that it is useful to monitor the concentrations of both desmethylated and hydroxylated metabolites in order to predict the clinical effects of clomipramine.

Does 24-h urinary MHPG predict treatment response to antidepressants? I. A review

The ability of pretreatment 3-methoxy-4-hydroxyphenylglycol (MHPG) to predict response to various antidepressants is reviewed. MHPG appears to be a modest predictor of treatment response to imipramine but does not appear to be a reliable predictor for other antidepressants.

Rapid non-enzymatic HPLC determination of total MHPG in human plasma

We have previously reported a method for the determination of total 3-methoxy-4-hydroxy phenylethylene glycol (MHPG) in brain, based on a simple acid-catalyzed hydrolysis. Now we extend this procedure to the determination of plasma total MHPG. The method involves the deproteinization of plasma with perchloric acid, followed by 3 minutes of an acid-catalyzed step. The hydrolysates are injected into the HPLC system, using a formic acid/methanol eluent with fluorimetric detection. Sample detection limit is below 1 ng MHPG/mL of plasma. This procedure has been used for the determination of plasma total MHPG from 109 healthy individuals of both sexes. Mean value was: 5.4 + 2.3 ng total MHPG/mL of plasma (means +/- S.D., N = 109). No sex differences were observed, and a slight correlation with age (r = 0.24, p less than 0.02) has been found. Plasma-free MHPG was also determined in a subgroup of 15 randomly chosen individuals (3.0 +/- 1.2 ng free MHPG/mL plasma, means +/- S.D.). A significant correlation was obtained with plasma total MHPG (r = 0.77, p less than 0.001, N = 15). The main advantage of the present method lays in its simplicity, since no enzymatic hydrolysis or extraction procedures are needed, being its reliability fully proven through 109 plasma total MHPG determinations.

Biogenic amines and their metabolites in body fluids of normal, psychiatric and neurological subjects

The biogenic monoamines and their metabolites have been isolated, identified and quantified in human body fluids over the past forty years using a wide variety of chromatographic separation and detection techniques. This review summarizes the results of those studies on normal, psychiatric and neurological subjects. Tables of normal values and the methods used to obtain them should prove to be useful as a reference source for benchmark amine and metabolite concentrations and for successful analytical procedures for their chromatographic separation, detection and quantification. Summaries of the often contradictory results of the application of these methods to psychiatric and neurological problems are presented and may assist in the assessment of the validity of the results of experiments in this field. Finally, the individual, environmental and the methodological factors affecting the concentrations of the amines and their metabolites are discussed.

Unsolved problems in the pharmacotherapy of depression

Five unsolved problems in the pharmacotherapy of depression are discussed: (a) it is not possible to differentiate endogenous and nonendogenous depression; (b) a selective efficacy of serotonin and noradrenaline reuptake inhibitors cannot be demonstrated; (c) the relationship between plasma levels and antidepressant effect is still unclear: plasma levels are influenced by pharmacogenetic factors, age, route of application, and concomitant treatment with other drugs; (d) evidence is growing for the development of tolerance towards therapeutic effects of antidepressants; (e) no pretreatment variable allows prediction of treatment response: the best predictor is the initial response to treatment.

3-MHPG as a non-predictor of antidepressant response to imipramine and electroconvulsive therapy

The urinary excretion of 3-methoxy, 4-hydroxyphenyl-glycol, (3-MHPG) was measured in 20 unipolar depressed patients before treatment with imipramine and electroconvulsive therapy (ECT) to investigate the relationship between pretreatment urinary excretion of 3-MHPG and clinical response. There was no difference in 3-MHPG excretion for depressed patients and controls. There was no significant difference between the mean percentage reduction of Hamilton Depression Rating Scale Scores in "low" and "high" excretors of 3-MHPG in the imipramine and ECT group of patients after four weeks of treatment.

Urinary 3-methoxy, 4-hydroxyphenylethylene glycol and therapeutic response to maprotiline and indalpine in major depression

The potential value of pretreatment urinary 3-methoxy, 4-hydroxyphenylethyleneglycol (MHPG) levels to predict the therapeutic response to antidepressants was studied by measuring urinary MHPG output in 42 depressed inpatients treated with a selective inhibitor of serotonin (Indalpine) or noradrenaline (Maprotiline) reuptake. Among the 42 depressed inpatients there were 33 cases of major depressive episode. Patients were treated for at least 3 weeks, firstly with intravenous infusions of maprotiline or indalpine which have been administered at random. No difference in pretreatment urinary MHPG levels was found between the responders to indalpine (1.08 +/- 0.48 micrograms/24 h/mg of creatinine) and the responders to maprotiline (1.15 +/- 0.62 micrograms/24 h/mg of creatinine). However, there was a difference in the pretreatment levels of urinary MHPG between the non-responders to indalpine (0.56 +/- 0.28 microgram/24 h/mg of creatinine) and the non-responders to maprotiline (1.37 +/- 0.68 micrograms/24 h/mg of creatinine). No correlation between this biochemical parameter and HDRS score was found. These results indicate that, in this study, there is no obvious relationship between the pretreatment urinary MHPG levels in depressed patients and their therapeutic response to specific inhibitors of noradrenaline or serotonin reuptake. However, there was a positive trend towards a lower pretreatment MHPG level to be associated with lack of response to indalpine.

Opposite effects of chronic imipramine treatment on brain and urine MHPG levels in the rat

Acute imipramine (IMI; 20 mg/kg, ip) in rats decreased the brain concentration of 3-methoxy-4-hydroxyphenethylene glycol (MHPG), a metabolite of norepinephrine (NE), to 85% of control 24 hr after injection. In contrast, chronic IMI (20 mg/kg, ip, daily for 14 days) significantly raised brain MHPG levels to 123% of control, while reducing brain NE levels. Urinary MHPG levels were reduced by both acute and chronic IMI treatments, to 52% and 51%, respectively. These data suggest that the brain turnover of NE is reduced after acute IMI, but is elevated after chronic treatment. Although urinary levels of MHPG changed in parallel with brain levels following an acute administration of IMI, such was not the case after chronic administration. We conclude that caution must be used in extrapolating drug-induced changes in urinary metabolite levels to brain amine function.

Adrenergic receptors in depression. Effects of electroconvulsive therapy

Platelet alpha 2-and lymphocyte beta 2-adrenoceptor densities, plasma noradrenaline and serum cortisol were measured before, during and one week after a course of EEG-monitored electroconvulsive therapy, in nine depressed patients. A 50% fall in Hamilton Depression Rating scores occurred after a fairly consistent total seizure time, regardless of the amount of ECT given. Platelet alpha 2-adrenoceptor densities showed a statistically significant fall after three ECTs, but were unchanged after the full course of ECT and were independent of clinical change. Lymphocyte beta 2-adrenoceptor densities were unaltered. Plasma noradrenaline concentrations were initially high, and fell with ECT in a manner paralleling clinical recovery. Plasma noradrenaline may be a more useful index of central changes during antidepressant treatment than peripheral blood cell receptor densities.

Neurochemical aspects of depression: the past and the future?

The role of aberrant neurochemical substrates in the etiology of depression and the neurochemical mechanisms of antidepressant therapies have been the subjects of many hypotheses in the last 30 years. Pharmacological studies of early antidepressant drugs indicated that brain monoamines were significantly affected by these drugs and these led to the formulation of the biogenic amine hypothesis of depression. Although this hypothesis has been of heuristic value in the study of drug mechanisms and has provided a basis for screening drugs for antidepressant potential, deficiencies in it have become apparent. Neuroanatomical and neurochemical considerations favour the view that brain noradrenaline and serotonin systems may serve as bias adjusting systems for each other and numerous other neural systems. As a consequence of such a relationship, a primary defect in some other neural system would appear amplified in measurements of serotonin or noradrenaline. A possible site for this primary defect may be in membrane composition and function. Recent studies have found that typical and other antidepressant therapies have a pronounced effect on membrane lipids. Thus, in view of the important functions of membrane lipids and the fact that they have been linked to the initiation and development of a number of other disease processes, it is now suggested that consideration be given to them as playing primary causal roles in the etiology of depression and as a site of action for antidepressant drugs.

MHPG excretion in endogenous depression: relationship to clinical state and the effects of ECT

In a group of 70 patients with endogenous depression entering a controlled trial of real versus sham ECT, urinary 3-methoxy-4-hydroxyphenylglycol (MHPG) excretion was significantly reduced by comparison with previously studied groups of control subjects, of acute and chronic schizophrenic patients and of anxious patients. However, urinary MHPG was unrelated to severity of depression, or to the presence of delusions, retardation or agitation. MHPG excretion did not predict clinical outcome, or the response to ECT. Urinary MHPG content at trial entry was unrelated to past tricyclic antidepressant or benzodiazepine medication, although an influence of the latter on the findings cannot be excluded, since all patients received benzodiazepine (nitrazepam) night sedation during the trial. During the 4-week trial MHPG excretion remained low and did not increase in relation to change in clinical state, although there was a small but significant increase in patients who received real ECT. The findings confirm that urinary MHPG excretion is reduced in depression, but establish that such reductions are not state dependent. Since the increase in MHPG excretion with ECT is not related to changes in clinical state, the former presumably does not reflect the mechanism of action of ECT.

Sex differences in biological factors putatively related to depression

Gender differences in the prevalence of affective disorders were suggested by several authorities in the field. Such differences may be attributed to sex-related differences in levels or activity of monoamine transmitters, especially since some of these variables have been shown to be altered by gonadal hormones. The reported association of perimenstrual and postpartum dysphoria, with affective disorders may contribute to further elucidation of pathophysiology of depression in women--in light of the hormonal-behavioral dynamics of these periods. Several factors associated with monoamines biosynthesis, availability, uptake and metabolism were found to be more abnormal in normal and depressed women compared to men. Age-sex differences in some biological markers for depression are reported as well. Their relevance to the underlying pathophysiology of depression is unclear but they may provide clues for further research.

Failure to correlate urinary MHPG with clinical response to amitriptyline

On the basis of studies carried out in a group of 44 patients with endogenous depressive illness, the authors conclude that MHPG in urine is not a good predictor of response to amitriptyline treatment. There are no correlations between MHPG level and clinical improvement after 2 weeks' treatment and with final results of the therapy.

Monoamine metabolites as predictors of antidepressant response: a critique

Monoamine metabolite measurements are being increasingly used for making nosological, symptomatological and pharmacological profiles of the affective disorders. A number of unresolved methodological issues question the validity of using baseline metabolite levels for predicting treatment response. Some studies show correlations between baseline metabolite levels and response to treatment with specific antidepressant agents. Effects of antidepressant treatment on metabolite levels may be useful in predicting drug response.

Trends in research and treatment of affective disorders

Trends in research on affective disorders were reviewed. Studies which described the contribution of neurotransmitters and neuroendocrines to depression, unipolar and bipolar, and manic states were cited. Women more frequently suffer from affective disorders but women's response to different therapies sometimes is more favorable than men's. Age and married status influence sex differences in the incidence of affective disorders. Symptoms of pain and depression intertwine, and response to analgesia may emerge as an index of response to therapy for depression. Trends in pharmacotherapies for affective disorders were reviewed: lithium, tricyclic antidepressants, and MAOI drugs, as well as trends in the employment of ECT and sleep deprivation to relieve symptoms of affective disorders were reviewed.