A team from Augusta University highlighted in a study the important role of the amino acid, tryptophan, in maintaining mood, energy levels, and immune response and protecting our microbiome as we age. This study, published in the International Journal of Molecular Sciences, reveals the entire relationship between tryptophan, the gut microbiome, and the inflammatory response.
Intestinal Microbiota
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Tryptophan is an amino acid found in high concentrations in foods such as milk, turkey, chicken, and oats. Adequate intake keeps our microbiome healthy, but our needs seem to increase as we age. So a diet low in tryptophan makes the gut microbiome less protective and increases the risk of inflammation throughout the body. A healthy microbiome also helps optimize the beneficial effects of tryptophan, including the production of the neurotransmitter serotonin, which reduces the risk of depression, and melatonin, which promotes good quality sleep, explains lead author Sadanand Fulzele, Ph.D., an expert on aging at the Medical College of Augusta University.
The relationship between tryptophan, the microbiome, aging, and inflammation is interdependent and particularly sensitive in older age.
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The study involved older mice in which just eight weeks of a low tryptophan diet led to harmful changes in the bacterial communities of the gut microbiota with higher levels of systemic inflammation.
The researchers found that diet was directly related to microbiota composition, and the changes were described as “striking.”
For example, low levels of tryptophan lead to lower levels of Clostridium sp. bacteria, which metabolize this essential amino acid and enable the production of beneficial compounds or hormones, including serotonin, in the gut.
Also were observed reduced levels of Mucispirillum and Blautia bacteria, which play an important role in maintaining healthy microbiota.
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Additionally, low tryptophan levels, lead to a threefold increase in Acetatifactor bacteria, which has been linked to gut inflammation.
Most importantly some of these changes in bacterial communities are also observed in chronic inflammatory bowel disease (IBD).
The role of the microbiome in aging is also confirmed by a study focusing on tryptophan: “We show that the microbiome plays an important role in the aging process and identify one of the key players in ‘microbiota’ aging, tryptophan, which produces metabolites essential for organs function,” – explains lead author Dr. Carlos M. Isales, of the Center for Healthy Aging and an expert in endocrinology, diabetes, and metabolism: “We see that the composition of the bacteria that use tryptophan changes, so even if you take more tryptophan, you may not be using it properly.
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Less tryptophan, more cytokines: These damaging changes in the microbiome also lead to increased release of cytokines, signaling molecules that promote inflammation, including IL-17, IL-1a, which largely promote inflammation. NB: IL-6 and IL-27 can promote or suppress inflammation depending on their levels. In contrast, mice fed a tryptophan-rich diet showed higher levels of the moderating IL-27.
Reversal is possible within a few days: When the mice were fed tryptophan again, these harmful changes were reversed within a few days, but they still had some negative effects. It would therefore be better, say the researchers, to feed metabolites that help the microbiota function slowly again, rather than with a sudden excess of tryptophan.
Each person has a unique microbiota that needs to be protected from the non-natural aging process associated with chronic diseases such as IBS, neurodegenerative diseases, and a weakened immune system. The gut microbiota is an important regulator of “normal” or healthy aging. Amino acids such as tryptophan, which are important for protein production, play a key role in our cellular function and ultimately the health of our organs and tissues.
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