The role an amino acid plays in depression has been identified in a study. The amino acid is proline that’s found in numerous types of foods. The study also links the consumption of a diet rich in proline to a higher likelihood of developing depression.1✅ JOURNAL REFERENCE
DOI: 10.1016/j.cmet.2022.04.001
To arrive at these findings, the amount and kind of amino acids in the diets of the individuals participating in the study were analyzed. A questionnaire was also completed to measure the depressive mood of the participants.
The evaluation of the questionnaire revealed that the consumption of proline is what was most linked to depression. To confirm this, the researchers evaluated plasma metabolomics which revealed the proline concentration to be one of the metabolites most linked to depression indicators.
However, not everybody who had a high proline intake stated in the questionnaire to be more depressed. When these Individual’s intestinal microbiota was examed, a connection was also seen between bacteria and depression, and also between depression and bacterial genes linked to proline metabolism.
It was thus found that circulating levels of proline were microbiota dependant. The microbiota of individuals with high consumption of proline but low proline plasma levels was comparable to the microbiota linked to low depression levels and was abundant in bacterial genes associated with the transport and metabolism of proline.
To determine whether proline’s presence caused or was a consequence of depression, the microbiota of the participants was transplanted into mice. These mice that received the microbiota of individuals with high proline became more depressed.
Different genes linked to proline transport were also observed in the rodents’ brains. The possibility that the depression phenotype can be transferred from humans to mice by transplanting microbiota and that such transplantation was demonstrated to generate proline transport alterations shows that this proline could be linked causally to depression.
Another experiment was conducted to confirm these results making use of fruit flies which allows for a more depressive mood to be induced. Two types of bacteria were isolated from the microbiota linked to the consumption of proline and they were added to the sterilized feed of the flies.
Flies ingesting food containing Lactobacillus, which was linked to less depression in mice, were more prepared to recover from difficulties. In comparison, flies ingesting Enterobacter, which is linked to human depression, were a lot more depressed.
The experiment was then conducted on flies that had been genetically modified to remove the channels that transport proline to the brain. The proline was in this scenario unable to get to the brain, and the flies were found to be highly depression resilient.
Image Source – compoundchem
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