Do endothelial cells eat tryptophan to die?

The role of the kynurenine pathway in cognitive functioning after stroke: A prospective clinical study

BACKGROUND

The kynurenine pathway is the main metabolic pathway of tryptophan degradation and has been associated with stroke and impaired cognitive functioning, but studies on its role in post-stroke cognitive impairment (PSCI) are scarce. We aimed to investigate associations between metabolites of the kynurenine pathway at baseline and post-stroke cognitive functioning over time.

METHODS

Baseline plasma kynurenines were quantified in 198 stroke patients aged 65.4 ± 10.8 years, 138 (69.7%) men, who were followed up over a period of three years after stroke. Baseline and longitudinal associations of kynurenines with PSCI and cognitive domain scores were investigated using linear mixed models, adjusted for several confounders.

RESULTS

No evidence of associations between kynurenines and odds of PSCI were found. However, considering individual cognitive domains, higher plasma levels of anthranilic acid (AA) were associated with better episodic memory at baseline (β per SD 0.16 [0.05, 0.28]). Additionally, a linear-quadratic association was found for the kynurenic acid/ quinolinic acid ratio (KA/QA), a neuroprotective index, with episodic memory (Wald χ2 = 8.27, p = .016). Higher levels of KA were associated with better processing speed in women only (pinteraction = .008; β per SD 0.15 [95% CI 0.02, 0.27]). These associations did not change over time.

CONCLUSIONS

Higher levels of KA, AA and KA/QA were associated with better scores on some cognitive domains at baseline. These associations did not change over time. Given the exploratory nature and heterogeneity of findings, these results should be interpreted with caution, and verified in other prospective studies.

Metabolic Pattern of Systemic Sclerosis: Association of Changes in Plasma Concentrations of Amino Acid-Related Compounds With Disease Presentation

OBJECTIVE

Amino acids (AA) and their derivatives play an integral role in the synthesis of structural and regulatory elements in human organisms and therefore pathologies such as systemic sclerosis that may alter the blood pattern of these compounds. This study aimed to evaluate changes in plasma concentrations of amino acid-related metabolites in systemic sclerosis in a search for potential biomarkers and mechanisms of the disease.

METHODS

Plasma samples from 42 patients diagnosed with systemic sclerosis (SSc) according to the 2013 American College of Rheumatology and European League Against Rheumatism ACR/EULAR classification criteria were compared to 27 matched healthy controls. Liquid chromatography/mass spectrometry was applied for the analysis of 36 amino acid-related metabolites.

RESULTS

The analysis of plasma AA metabolite patterns revealed the number of changes including an increase (20%) in concentrations of NO synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA) in SSc vs. healthy subjects. Furthermore, SSc patients had higher glutamine, proline, betaine, 1-methylhistidine, and methylnicotinamide levels, while the concentration of tryptophan was lower. The specific metabolic pattern was identified for several aspects of disease presentation. Most interestingly NOS inhibitor L-NAME was elevated in patients with diffuse systemic sclerosis or telangiectasia.

CONCLUSIONS

These results provide further evidence for the involvement of endothelium-dependent pathways in the mechanisms and presentation of SSc. Endothelial dysfunction biomarkers may be useful in the assessment of presentation and prognosis in SSc.