Nate,
I think the group led by C. Franceschi came to realize inflammation is key in aging (“inflammaging”), as one would expect, but found details are much more complex. The best and simplest description I found is in a great 2015 review paper (1) where other well-known aging experts also contributed (the paper touches on some of the molecules Logic mentions in his previous post too):
“Chronic, low-grade inflammation is recognized as a major characteristic of aging. This phenomenon is so pervasive that the term inflammaging (Franceschi et al., 2000; Franceschi & Campisi, 2014) has been coined to emphasize that many major age-related disabilities, including cancers, susceptibility to infections, and dementia have immunopathogenic components (Franceschi & Campisi, 2014). Thus, as inflammation is associated with many age-related conditions, genes and pathways that regulate inflammation are candidate targets to combat them (Franceschi & Campisi, 2014). Inflammaging appears to be much more complex than we previously thought, and a variety of tissues and organs participate in producing inflammatory stimuli (Franceschi et al., 2007; Cevenini et al., 2012). The list is extensive and includes the immune system, but also adipose tissue, skeletal muscle, liver, and the gut. The gut is of unique importance, because it is the body’s largest immune organ and contains trillions of bacteria that can release inflammatory stimuli into the portal and systemic circulation (Biagi et al., 2010).”
To come to your two questions, as tryptophan metabolizes to melatonin I guess there is an overall reduction of melatonin:
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https://en.wikipedia.../wiki/Melatonin
However, consider that there is a huge difference between gut and pineal gland content of melatonin. Studies (2) have shown that melatonin in the gut is about 400x higher than in pineal gland. So it must be important for the gut even if its function there is less clear than in the central nervous system. There are important hints though e.g. related to irritable bowel syndrome, colon motility and immune system regulation. Also, gut melatonin is independent from day/night cycles while depending on age.
A depletion in tryptophan also looks not a good thing as reported in C. Franceschi’s slide 67 of his presentation and my post as it can finally nurture inflammation. They noticed an increased abundance of genes involved in the tryptophan metabolism pathway in the centenarians:
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What about supplementation?
I would say that if I do not have the major troubles as above, my mood is OK and I sleep well, I would not care too much about supplementation with tryptophan and melatonin on regular basis. OTOS, probiotics could be a good idea with the well-known health beneficial strains. I would also run a microbiological stool analysis at baseline. However, I think we are far from specific strains self-prescription based on the centenarian study I reported (such as Akkermansia, Bifidobacterium and Christensenellaceae). The study makes clear that, while it could be hypothesized: “It is not possible to know whether these health-associated features were already present at a younger age in these exceptional individuals, and/or they are somewhat related to the past lifestyle, due to the cross-sectional nature of the study; indeed, only longitudinal studies, which would be very difficult to apply to the field of human longevity, could explain whether these gut bacteria are always lost during aging and reacquired by the subjects who get to live longer or whether they are maintained across aging and longevity only by long-living subjects.”
Maybe a smarter idea before we clarify if all those microorganisms characterizing the centenarians can be supplemented to our benefit is to look at pre-biotics and nutrients they like and let the gut microbiome adapts and balances (homeostasis). A thread on the Reddit forum for example has looked at Akkermansia and suggests pomegranates, fructooligosaccharides, glucosamine, glutamine and fish oil are good nutrients for those bacteria.
The EU’s NU-AGE project posted before by Niner ended in April 2016 (you have good webminars on the final closing conference with highlights and results, look first at the highlights by C. Franceschi) and is all about a “whole diet”, basically a Mediterranean ad-hoc fortified for the elderly diet (look at Agnes Berendsen's presentation) positively impacting the elderly toward an healthy aging, an urgent and healthcare European cost priority.
So in sum and barring major diseases, I think probiotics are a good idea but before going to more exotic types in search of what possibly benefited centenarians, it is maybe smarter to get first a “whole diet” as per the NU-AGE project, to which I would add a stool microbiology analysis and possibly use some of the nutrients which centenarians typical strains such as Akkermansia, Bifidobacterium and Christensenellaceae like to eat and are also beneficial for a host of other conditions (e.g. consider the effects of pomegranates and fish oil)
(1) Interventions to Slow Aging in Humans: Are We Ready?
http://www.ncbi.nlm....pubmed/25902704
(2) Distribution, function and physiological role of melatonin in the lower gut.