Sequential comparison of L-tryptophan with E.C.T. in severe depression

Changes in Tryptophan-Kynurenine Metabolism in Patients with Depression Undergoing ECT-A Systematic Review

The kynurenine pathway of tryptophan (Trp) metabolism generates multiple biologically active metabolites (kynurenines) that have been implicated in neuropsychiatric disorders. It has been suggested that modulation of kynurenine metabolism could be involved in the therapeutic effect of electroconvulsive therapy (ECT). We performed a systematic review with aims of summarizing changes in Trp and/or kynurenines after ECT and assessing methodological issues. The inclusion criterium was measures of Trp and/or kynurenines before and after ECT. Animal studies and studies using Trp administration or Trp depletion were excluded. Embase, MEDLINE, PsycInfo and PubMed were searched, most recently in July 2022. Outcomes were levels of Trp, kynurenines and ratios before and after ECT. Data on factors affecting Trp metabolism and ECT were collected for interpretation and discussion of the reported changes. We included 17 studies with repeated measures for a total of 386 patients and 27 controls. Synthesis using vote counting based on the direction of effect found no evidence of effect of ECT on any outcome variable. There were considerable variations in design, patient characteristics and reported items. We suggest that future studies should include larger samples, assess important covariates and determine between- and within-subject variability. PROSPERO (CRD42020187003).

L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications

An essential component of the human diet, L-tryptophan is critical in a number of metabolic functions and has been widely used in numerous research and clinical trials. This review provides a brief overview of the role of L-tryptophan in protein synthesis and a number of other metabolic functions. With emphasis on L-tryptophan's role in synthesis of brain serotonin, details are provided on the research uses of L-tryptophan, particularly L-tryptophan depletion, and on clinical trials that have been conducted using L-tryptophan supplementation. The ability to change the rates of serotonin synthesis in the brain by manipulating concentrations of serum tryptophan is the foundation of much research. As the sole precursor of serotonin, experimental research has shown that L-tryptophan's role in brain serotonin synthesis is an important factor involved in mood, behavior, and cognition. Furthermore, clinical trials have provided some initial evidence of L-tryptophan's efficacy for treatment of psychiatric disorders, particularly when used in combination with other therapeutic agents.

Tryptophan and 5-hydroxytryptophan for depression

BACKGROUND

5 Hydroxytryptophan (5-HTP) and tryptophan are so-called natural alternatives to traditional antidepressants, used to treat unipolar depression and dysthymia.

OBJECTIVES

To determine whether 5-HTP and tryptophan are more effective than placebo, and whether they are safe to use to treat depressive disorders in adults.

SEARCH STRATEGY

Trials were searched in computerized general (Medline, Psychlit, and Embase) and specialized databases (Cochrane Controlled Clinical Trials Register, Cochrane Collaboration Depression, Anxiety and Neurosis Controlled Trial Register); by checking reference lists of relevant articles; by handsearching relevant specialist journals; and by contacting relevant authors where appropriate. Publications in all languages were sought.

SELECTION CRITERIA

Trials were included if they were randomized, included patients with unipolar depression or dysthymia, compared preparations of 5-HTP or tryptophan with placebo, and included clinical outcomes assessed by scales assessing depressive symptoms.

DATA COLLECTION AND ANALYSIS

Data was extracted independently by the three reviewers, onto data collection forms. Inclusion criteria were applied to all potential studies independently and a coefficient of agreement (Kappa) was calculated for them. Disagreement was resolved by reaching consensus. Trial quality was scored according to risk of bias. Analysis for 5-HTP and tryptophan were combined due to the small number of included trials.

MAIN RESULTS

108 trials were located using the specified search strategy. Of these, only two trials, involving a total of 64 patients, were of sufficient quality to meet inclusion criteria. The available evidence suggests these substances were better than placebo at alleviating depression (Peto Odds Ratio 4.10; 95% confidence interval 1.28-13.15; RD 0.36; NNT 2.78). However, the evidence was of insufficient quality to be conclusive.

REVIEWER'S CONCLUSIONS

A large number of studies appear to address the research questions, but few are of sufficient quality to be reliable. Available evidence does suggest these substances are better than placebo at alleviating depression. Further studies are needed to evaluate the efficacy and safety of 5-HTP and tryptophan before their widespread use can be recommended. The possible association between these substances and the potentially fatal Eosinophilia-Myalgia Syndrome has not been elucidated. Because alternative antidepressants exist which have been proven to be effective and safe the clinical usefulness of 5-HTP and tryptophan is limited at present.

Dietary tryptophan reverses alcohol-induced impairment of facial recognition but not verbal recall

The present study demonstrates that alcohol-induced memory impairment can be attenuated by pretreatment with an oral tryptophan supplementation. These results provide support for the role of a brain serotonin deficit in this impairment and highlight the impact a dietary manipulation can have on a complex behavioral process.

L-5HTP in depression resistant to re-uptake inhibitors. An open comparative study with tranylcypromine

L-5HTP and tranylcypromine were compared in an open, but controlled and cross-over study, in patients suffering from major depression; all were non-responders to several reuptake inhibitors, including oxaprotiline and fluvoxamine. After four unsuccessful sleep-deprivations, L-5HTP or tranylcypromine were given during four weeks in a crossover design. Of 17 patients given L-5HTP during both treatment periods, none responded, whereas of 26 patients treated with tranylcypromine, 15 responded. Thus, L-5HTP is not a therapeutically effective alternative in depressed patients who have not responded to reuptake inhibitors.

A controlled study of a specific MAO A reversible inhibitor (R011-1163) and amitriptyline in depressive illness

A double blind comparative study of amitriptyline and a new reversible MAO A inhibitor R011-1163 was conducted in 25 depressed inpatients over 4 weeks. Response to treatment was assessed with the Hamilton depression rating scale, the Carroll depression self rating scale and the Visual analogue scale. Both drugs produced significant changes in depressive symptomatology (P less than 0.01, MANOVA) and there were no statistically significant differences between drugs (P greater than 0.05 MANOVA). Side effects were of mild to moderate severity with dry mouth the most commonly reported side effect of amitriptyline and vague, generalised headache in patients, treated with R011-1163.

Maprotiline in affective illness. Plasma concentration and clinical response

Twenty patients suffering from endogenous depression were treated with maprotiline for 4 weeks. Blood samples were collected at weekly intervals and severity of depression assessed using the Hamilton Depression Rating Scale. No simple relationship between plasma maprotiline concentration and amelioration score was observed at week 3 (rs = 0.25) or week 4 (rs = -0.05). No significant difference in plasma concentrations between responders and non-responders was observed at week 4. Maprotiline was effective as an antidepressant in some patients.

The treatment of depression in general practice: a comparison of L-tryptophan, amitriptyline, and a combination of L-tryptophan and amitriptyline with placebo

One hundred and fifteen patients from 5 general practices participated in a 12-week, double-blind study comparing L-tryptophan, amitriptyline, L-tryptophan-amitriptyline combination and placebo in the treatment of depression. Analysis of total score on the Hamilton Depression Scale and a global rating of depression showed that all 3 active treatments were more effective than placebo. Significantly more patients were withdrawn as treatment failures in the placebo group compared with the active treatment groups. Side-effects necessitated withdrawal of more patients from the amitriptyline group than from the other active treatment groups, but this difference was not significant. Plasma amitriptyline and nortriptyline levels were similar in the amitriptyline and combined treatment groups. Standard haematological and biochemical profiles did not alter significantly in any group, but mean heart rate was significantly increased in patients receiving amitriptyline. There was no change in free or total plasma tryptophan concentration with treatment or on remission of symptoms.

Diet-induced mood changes in normal populations

Using an 11-item questionnaire and a double-blind experimental design, changes in mood, hunger and food preference after taking caffeine (100 mg), tryptophan (500 mg), tyrosine (500 mg) or placebo, were investigated in 60 volunteers. At the end of the study, volunteers also ranked the four treatments on a sedation/stimulation scale. Caffeine significantly increased scores for wakefulness, vigor, clarity of mind, energy, feeling full of ideas, feeling full of go and feeling efficient. Caffeine was also ranked as the most stimulating treatment (p less than 0.001). Tyrosine produced no changes, while tryptophan shifted mean scores towards somnolent and lethargic, and was ranked most sedating (p less than 0.05). None of the treatments changed hunger ratings or carbohydrate/protein preference.

Urinary hesitancy with therapeutic doses of L-tryptophan

L-tryptophan, a precursor of serotonin, in doses of 4 to 5 g/d, has been found to be effective in increasing sleep time, reducing sleep latency, and reducing the number of awakenings. In this report, L-tryptophan 4-6 g/d was administered, along with niacinamide 100 mg and pyridoxine 50 mg, for sleep. Two days after starting L-tryptophan, the patient reported difficulty in voiding. Medications with known anticholinergic activity were selectively discontinued during the patient's hospital course. Seven days after the last dose of L-tryptophan, improvement was noted in the patient's urinary status. Prior to discharge, doxepin was restarted and titrated up to 150 mg/d without a recurrence of urinary problems.

Metabolism of an oral tryptophan load. I: Effects of dose and pretreatment with tryptophan

1 The metabolism of three oral doses of L-tryptophan (50, 25 and 10 mg/kg) in healthy young males has been investigated. 2 There was a linear relationship between both peak and area under curve of the total plasma tryptophan concentrations whilst the relationship between these parameters and plasma free tryptophan was hyperbolic. 3 Before the tryptophan load about 85% of plasma tryptophan was bound to albumin. As plasma tryptophan concentrations increased there was a hyperbolic increase in free tryptophan. Scatchard analysis revealed 1.4 binding sites/molecule albumin with a dissociation constant (Kd) of 57.9 microM. Following administration of L-tryptophan (50 mg/kg) twice daily for 7 days there was no alteration in the number of binding sites but the dissociation constant (Kd) had decreased to 30.9 microM. 4 L-Tryptophan (50 mg/kg twice daily for 7 days) markedly increased both basal plasma total and free tryptophan. However following a further load the total tryptophan curve was comparable to that seen after acute administration. The plasma free tryptophan curve was lowered relative to that seen after an acute dose. 5 Increasing the tryptophan dose shortened the plasma half-life and decreased the volume of distribution and the rate of clearance. Longer term tryptophan administration had no significant effect on plasma half-life or volume of distribution but did decrease the rate of plasma clearance. 6 The plasma kynurenine concentration increased with increasing tryptophan dose and basal concentrations increased markedly after longer term tryptophan administration. 7 Tryptophan administration either acutely or chronically produced little change in urinary tryptophan or 5-hydroxyindole acetic acid excretion. Urinary kynurenine and indole acetic acid excretion increased with increasing doses of tryptophan. 8 Data are discussed in relation to the administration of L-tryptophan for the treatment of depression.

Viloxazine plasma concentrations and clinical response

Eleven patients suffering from primary depressive illness were treated with 300 mg/d of viloxazine for 29 days. Blood samples were collected at weekly intervals and severity of depression assessed using the Hamilton depression rating scale. Mean plasma viloxazine level for all patients during the trial was 1.20 micrograms/ml and ranged from 0.40 to 2.70 micrograms/ml. No simple relationship between plasma concentration and amelioration score was observed at day (rs = -0.02), day 22 (rs = -0.29) or day 29 (rs = 0.09). No significant difference in plasma concentrations between responders and non-responders was observed at day 29. Side effects were not correlated with plasma concentrations.

Antidepressant potentiation of 5-hydroxytryptophan by L-deprenil in affective illness

In an open trial study, L-Deprenil, an irreversible selective MAO-B inhibitor without 'chesse effect' was given to 14 patients with unipolar and bipolar depression receiving L-5-Hydroxytryptophan (L-5-HTP) and benzerazide. Ten out of 14 patients showed a good response to the combination of drugs and a correlation was found between the degree of platelet MAO inhibition and clinical response. In a double-blind controlled study, 18 affectively ill patients were randomly allocated to L-Deprenil plus L-5-HTP and benzerazide, 21 patients were treated with L-5-HTP and benzerazide and 19 patients with placebo only. Patients treated with the combination of L-Deprenil and L-5-HTP showed a significantly greater clinical improvement than placebo patients but this was not the case for patients treated with 5-HTP alone. A positive relationship was demonstrated between mood improvement and degree of platelet MAO inhibition in patients treated with L-Deprenil.

Tryptophan antidepressant 'physiological sedative': fact or fancy?

Some recent publications relating to the allegedly antidepressive and sedative effects of L-tryptophan the precursor of 5-HT have been reviewed. The evidence to date suggests that the amino acid is as effective as standard tricyclic drugs in alleviating the symptoms of depression, especially those cases presenting with mainly psychomotor retardation, and is synergistic with MAOIs. L-Tryptophan would also appear to be a 'physiological sedative'. This action, however, appears to be related to the time of administration and at present has only been demonstrated at night. when endogenous levels of 5-HT are at their peak. In terms of practical therapeutics L-tryptophan would appear to have greater potential as an 'antidepressant' than as a 'sedative'.

L-tryptophan and 5-hydroxytryptophan in the treatment of depression. A review

Trials performed do not provide evidence for an antidepressant effect of 5-HTP. L-TP, without interacting pharmaca, does not appear to be a well-documented antidepressant. The only convincing evidence for L-TP as an antidepressant is that L-TP enhances the effect of MAOI.

Manipulation of cerebral monoamines in the treatment of human epilepsy: a pilot study

The effects of L-DOPA, L-tryptophan, monoamine oxidase inhibitor (MAOI), and MAOI plus L-tryptophan, each for 3 months, have been assessed in 10 severe, adult epileptics with placebo control. There was no overall reduction in seizure frequency, but 2 patients with minor partial seizures improved, 1 with L-DOPA, MAOI, and MAOI plus L-tryptophan, and the other with L-tryptophan and MAOI plus L-tryptophan. We have not been able to demonstrate an increased turnover of cerebral serotonin (5-HT), as measured by cerebrospinal fluid 5-hydroxyindoleacetic acid, after treatment with L-tryptophan for 3 months. This observation casts doubt on the ability of L-tryptophan to alter the long-term metabolism and functional activity of brain 5-HT. The importance of further exploration of manipulation of cerebral monoamines as a possible approach to the treatment of epilepsy is emphasized.

Tryptophan and depressive illness

Plasma free tryptophan is significantly decreased in monopolar, depressed patients. No evidence was found to suggest that poor nutritional history prior to hospital admission was responsible for these low levels. Factors known to influence tryptophan-albumin binding in plasma, e.g. concentration of plasma proteins, albumin and non-esterified fatty acids, did not account for the low levels of free tryptophan in depressed patients. A significant decrease in plasma free tryptophan levels was found in perimenopausal but not in pre- or post-menopausal female controls. This mirrors the decrease in circulating oestrogens. Although exogenously administered oestrogens do not have any therapeutic efficacy in relieving mild residual depressive symptoms of lithium treated patients, they increased the levels of plasma free tryptophan. Clofibrate also displaces tryptophan from plasma protein binding sites in both depressed patients and controls. Utilization of the increased levels of plasma free tryptophan is reduced in depressed patients. A situation therefore exists in depressed patients where the plasma free tryptophan is not only reduced but also leaves the plasma less readily than in control subjects.

A new antidepressant butriptyline: plasma levels and clinical response

Ten patients who suffered from a primary depressive illness were treated with a new antidepressant drug butriptyline (150 mg/day). Six of the patients showed marked clinical improvement, as judged by depression rating scores, at the end of 22 days of treatment. No simple relationship was found between clinical response and plasma butriptyline concentration. Butriptyline is an effective antidepressant agent, well tolerated and with few side effects.

Comparative trial of L-tryptophan and amitriptyline in depressive illness

Depressed patients who were suitable for drug treatment were allocated randomly to treatment for four weeks with either amitriptyline in doses reaching 150 mg daily or with L-tryptophan in a maximal dose of 8 G daily. Both in-patients and out-patients were included. The trial was double-blind and ratings were made at the start of treatment and weekly for the subsequent four weeks: the patients were then followed for a further six months. Both groups of patients improved steadily over the course of four weeks and there were no marked differences between the treatment groups though there was some tendency for the improvement of the tryptophan-treated patients to fade between the third and fourth weeks. Within the tryptophan group anxious patients improved least. It is concluded that L-tryptophan probably has some antidepressive action in patients with depressive illness of moderate severity.

Plasma amino acids as an index for subgroups in manic depressive psychosis: correlation to effect of tryptophan

Two biochemical distinct groups of manic depressive patients seem to be present. One group showed a normal pattern of plasma amino acids and was resistant to oral tryptophan medication. Another group, characterized by a relative deficiency of tryptophan in plasma as measured by the ratio of total plasma tryptophan to competing amino acids, responded readily to tryptophan treatment. No significant differences could be demonstrated in the free tryptophan, total tryptophan, percentage of free tryptophan or kynurenine in the plasma between patients and controls. The findings are discussed in view of changes in the transport conditions of tryptophan from plasma into the brain.

Precursors and metabolites of 5-hydroxytryptamine and dopamine in the ventricular cerebrospinal fluid of psychiatric patients

Tryptophan and 5-hydroxyindoleacetic acid (precursor and metabolite respectively of 5-hydroxytryptamine) were determined in ventricular CSF of psychiatric patients undergoing stereotactic subcaudate tractotomy. Tyrosine and homovanillic acid (precursor and metabolite respectively of dopamine) were also determined. Results suggest an association between affective state and the above precursor amino acids with lower concentrations in primary depression and higher ones when anxiety or agitation predominate. This leads to lower 5-hydroxyindoleacetic acid concentrations in depression and higher concentrations in anxiety and agitation.

The effect of tryptophan and a tryptophan/5-hydroxytryptophan combination on indoles in the brains of rats fed a tryptophan deficient diet

Rats maintained on a tryptophan deficient diet had reduced brain and serum tryptophan and brain 5-hydroxyindolacetic acid levels compared to controls. 5-Hydroxytryptophan and L-tryptophan administered to these deficient rats in a combination (5:95) produced a greater elevation of indolamines and tryptophan in the brain than either amino acid alone. In rats maintained on a normal diet the urinary output of 3-hydroxykynurenine was considerably reduced by treatment with the combination of amino acids as compared to tryptophan treatment. 5-Hydroxytryptophan reduced the induction of kynurenine synthesis in the liver produced by tryptophan, implying that it is capable of inhibiting the enzyme tryptophan pyrrolase in vivo. It is suggested that the possession by 5-hydroxytryptophan of tryptophan pyrrolase inhibitory properties may make the administration of the combination a better treatment of depressed patients exhibiting an indolamine deficit than either amino acid alone.

The acute effects of oral (--)-tryptophan in human subjects

1 The psychotropic effects of a single oral dose of (--)-tryptophan (5 g) in human volunteers were investigated using a series of physiological and psychological tests. 2 Self-ratings of mood showed increase in drowsiness but no euphoria was detected. 3 Severe initial nausea occurred and headache increased; other bodily symptoms were unaffected. 4 Trptophan caused increased activity in the slow wavebands of the EEG but did not alter the other physiological measures. 5 The levels of total and free tryptophan in the plasma increased 8 and 20 fold respectively to peak levels 2 h after ingestion.

A sequential trial comparing two plasma levels of nortriptyline

Pairs of depressed patients were matched for age, sex, and severity of depression, and treated for four weeks with nortriptyline so that plasma levels of below 49 ng/ml and above 140 ng/ml were, obtained.

Comparisons of pairs of patients as regards to improvement of depression, using a sequential skew restricted design, suggested that it was unlikely that a significant difference between the two treatment regimes would be detected.

The Hamilton Rating Scale for depression: a factor analysis

A factor analysis was carried out of ratings on the Hamilton Scale on a group of 134 male and 213 female depressed patients. The original data covered a wide range of severity of illness and the distribution of severity scores was not biased from normal. Hamilton's general factor was confirmed but his bipolarity between agitated and retarded depression did not emerge. Sex differences in factor patterns were found and a preliminary experiment showed that factor scores could isolate anxiety features and personality factors.

Huntington's chorea and tryptophan

Daily use of 7 g l-tryptophan and 70 mg pyridoxine for 14 days led to no deterioration of objectively measured manual motor skills in a small group of patients with Huntington's chorea.