ECT and Tryptophan-Kynurenine Metabolism: Systematic Review

Out on PubMed, from investigators in Norway, is this paper:

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

Aarsland TIM, Instanes JT, Posserud MR, Ulvik A, Kessler U, Haavik J.Pharmaceuticals (Basel). 2022 Nov 19;15(11):1439. doi: 10.3390/ph15111439.PMID: 36422569 

The abstract is copied below:

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).

Keywords: age; comorbidity; depression; electroconvulsive therapy; inflammation; kidney function; kynurenine; quinolinic acid; stress; tryptophan.

The pdf is here.

And from the text:

Here's one for you hardcore biochemistry aficionados; I admit it gave me biochem PTSD. And if Figure 6 (above) is a "simplified overview", I would hate to see the full one.

All kidding aside, this is a massive undertaking with potentially very interesting theoretical and mechanistic insights. Unfortunately, at the current level of study and methodological heterogeneity, there is no there there. Kudos to the authors for their valiant effort.