Tryptophan is a mood-enhancing hormone that is closely related to serotonin. It is commonly found in depressed individuals who have low levels of serotonin. Tryptophan metabolism happens through the kynurenine pathway, which takes one of two branches: protect brain tissue or harm it.
To protect brain tissue, an enzyme known as KAT is required so that tryptophan metabolism can be completed. Aerobic and resistant exercise has been found to increase KAT, which promotes tryptophan metabolism. This ensures there is more brain tissue protection rather than destruction.
Previous research in young adults has found that exercise can cause changes in the muscles which lead to mood-boosting effects, but little is known of these effects in older adults.
Canadian researchers looked at men over the age of 65 in a 12-week trial involving resistance exercise and high-intensity interval training. Blood and muscle samples were collected and examined for gene and protein expression before and after the trial.
The researchers found that expression of transcription factors and KAT increased significantly during exercise trials, which replicated the previous work conducted on younger adults.
They concluded, “The significant exercise training-induced increase in the expression of skeletal muscle transcription factors and KAT in older adults is encouraging given the potential implications related to kynurenine pathway regulation. Future studies are warranted to explore the impact of various exercise modalities and intensities on transient changes of such factors in depressed adults.”
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