Analysis of tryptophan metabolites ... in human and murine tissue ... using high resolution mass spectroscopy, 2024, Abuirais, Bergquist et al

Analysis of tryptophan metabolites and related compounds in human and murine tissue: development and validation of a quantitative and semi-quantitative method using high resolution mass spectrometry

Sandy Abujrais, ab S. J. Kumari A. Ubhayasekera ab and Jonas Bergquist *ab

Abstract
This study explores the metabolic differences between human and murine plasma in addition to differences between murine subcutaneous and visceral white adipose tissue. A quantitative and semi-quantitative targeted method was developed and validated for this purpose. The quantitative method includes tryptophan and its metabolites in addition to tyrosine, phenylalanine, taurine, B vitamins, neopterin, cystathionine and hypoxanthine. While the semi-quantitative method includes; 3-indoleacetic acid, 5-hydroxyindoleacetic acid, acetylcholine, asymmetric dimethylarginine, citrulline and methionine.

Sample preparation was based on protein precipitation, while quantification was conducted using ultrahigh-performance liquid chromatography coupled to a quadrupole Orbitrap tandem mass spectrometer with electrospray ionization in the parallel reaction monitoring (PRM) mode. The low limit of quantification for all metabolites ranged from 1 to 200 ng mL−1. Matrix effects and recoveries for stable isotope labelled internal standards were evaluated, with most having a coefficient of variation (CV) of less than 15%. Results showed that a majority of the analytes passed both the intra- and interday precision and accuracy criteria.

The comparative analysis of human and murine plasma metabolites reveals species-specific variations within the tryptophan metabolic pathway. Notably, murine plasma generally exhibits elevated concentrations of most compounds in this pathway, with the exceptions of kynurenine and quinolinic acid. Moreover, the investigation uncovers noteworthy metabolic disparities between murine visceral and subcutaneous white adipose tissues, with the subcutaneous tissue demonstrating significantly higher concentrations of tryptophan, phenylalanine, tyrosine, and serotonin.

The findings also show that even a semi-quantitative method can provide comparable results to quantitative methods from other studies and be effective for assessing metabolites in a complex sample. Overall, this study provides a robust platform to compare human and murine metabolism, providing a valuable insight to future investigations.

https://pubs.rsc.org/en/content/articlelanding/2024/ay/d3ay01959d
open access

 

Copying Mango's post from the Bergquist thread:

From OMF email newsletter:

Research Summary: From the Desk of Dr. Jonas Bergquist:

“Our recent study, published in the Analytical Methods Journal, aimed to investigate the levels of tryptophan metabolites in human plasma using an advanced technique called high-resolution mass spectrometry. Tryptophan is an essential amino acid that plays a crucial role in various metabolic processes. Disruptions in its pathway have been implicated in several diseases.

Our goal is to incorporate this methodology in our upcoming study to analyze plasma samples from people diagnosed with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) and comparing them to samples from healthy individuals, to uncover potential mechanisms involved in the development of this debilitating disease. This study supports the Kynurenine trap model for ME/CFS, shedding light on the pathogenesis of the condition. We hope that our findings will contribute to a deeper understanding of ME/CFS.”