Tryptophan metabolite kynurenine may be linked to ischaemic heart disease

There appears to be a possibility that kynurenine, one of the main metabolites of tryptophan, is positively associated with ischaemic heart disease (IHD), but further studies are needed to confirm any link and underlying mechanism, suggests a recent study.

“Observationally, plasma tryptophan is inversely associated with IHD,” the authors said. “[H]owever, its main metabolites, serotonin, and kynurenine are positively associated with IHD, which makes the effects of tryptophan difficult to infer.”

A two-sample Mendelian randomization study was conducted to obtain less confounded estimates of the associations of tryptophan and physiologically related factors (serotonin and kynurenine) with IHD, its risk factors and depression.

The authors used genetic instruments independently associated with tryptophan, serotonin and kynurenine metabolites applied to a meta-analysis of the UK Biobank SOFT CAD study with the CARDIoGRAMplusC4D consortium (cases, n≤76,014; controls, n≤264,785), and other consortia for risk factors including diabetes, lipids and blood pressure, as well as for depression.

No association was found between tryptophan or serotonin and IHD. Kynurenine, on the other hand, showed a nominal and positive correlation with IHD (odds ratio, 1.57, 95 percent confidence interval, 1.05–2.33). However, this association did not persist after correction for multiple comparisons.

Furthermore, null associations were observed with IHD risk factors and depression.

Tryptophan is an essential amino acid derived from dietary items, including dairy products, eggs, nuts, legumes and grains. It has also been recommended as a dietary supplement to boost mental health, according to the authors.