Working Towards Biomarkers of Aging Based on Analysis of Saliva

There is much less interest in analysis of saliva than of blood or urine when it comes to mining metabolite and protein data in search of biomarkers of aging. Saliva has less to work with in terms of useful molecules. Nonetheless, some groups are making inroads in the analysis of biomolecules in saliva, as noted here. It should be expected that any sufficiently diverse set of biological data will exhibit characteristic changes with the accumulation of age-related damage and dysfunction. Somewhere in all of these options lies a simple, low-cost test that accurately reflects the state of that damage and dysfunction, and can thus be used to rapidly assess the degree to which any potential rejuvenation therapy actually works.

Researchers have conducted a comprehensive analysis of the metabolites that make up human saliva using samples given voluntarily from a group of 27-to-33-year-old individuals and a group of 72-to-80-year-old individuals. The sample collection was easy and noninvasive. Twenty-seven volunteers supplied their saliva, which they collected themselves at home. These were transferred to the laboratory for analysis. In general, the concentration of metabolites in saliva is very low compared to that in blood and urine, making it more challenging to detect them. However, using a comprehensive method, the researchers identified 99 metabolites, some of which were previously unreported in saliva. They also found that saliva contains information that reflects biological aging. Twenty metabolites, including those related to antioxidative activity, energy synthesis, and muscle maintenance, were lower in the elderly individuals than the young people, whereas one metabolite actually increased.

"It's interesting that ATP, the metabolite related to energy production, increased 1.96-fold in the elderly. This is possibly due to reduced ATP consumption in the elderly individuals. Amongst the metabolites that declined in quantity were two that are related to taste, suggesting that the elderly lose some ability to taste, and others that are related to muscle activity such as swallowing. These age-linked salivary metabolites together illuminate a metabolic network that reflects a decline of oral function during human aging."

Although this is the first comprehensive analysis to be performed on the metabolites of saliva, the researchers are planning to continue this work. In the future, they hope that saliva will be a sample that can be given readily and easily but could provide an enormous amount of information about an individual's health. "In saliva, age-linked metabolites are related to relatively broad metabolic conditions so that age-related information obtained from salivary metabolites may be distinct from that of blood and urine."


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