Microbiome and Antiaging Medicine: Predicting Longevity from the Microbiome

If it becomes possible to use an individual’s gut microbiota, bacterial flora information as an indicator of biological age, and propose specific measures, it could contribute to lifespan extension (healthy longevity). For this, analysis based on long-term cohort study data and information from intervention trials during relatively chronic periods, not acute, would be useful. Wilmanski et al. [1] conducted a study on the diversity of gut bacterial flora and proposed a unique indicator, Bray–Curtis uniqueness, a new indicator of β diversity at the genus level or ASV (amplicon sequence variant) level. This uniqueness index increases with age and showed the highest correlation with chronological age compared to various clinical biomarkers. Further analysis of gut bacteria correlated with this uniqueness revealed a correlation between increased uniqueness and a decrease in the genus Bacteroides, and groups with low uniqueness or a high occupancy rate of the genus Bacteroides had a lower survival rate 4 years later, as revealed by a cohort study. Salosensaari et al. [2] tracked the relationship between gut bacterial flora and mortality in a population cohort of 7211 people for 15 years and revealed the characteristics of gut bacterial flora associated with mortality. They found that α diversity (Shannon, Observed) was not related to mortality, and among β diversity, the third component (PC3) of principal component analysis had a positive correlation with mortality, and they proceeded with the analysis of factors affecting PC3. As a result, the correlation between PC3 and mortality was not affected by age, sex, BMI, smoking, diabetes, anticancer drugs, immunomodulators, hypertension, and antihypertensive drugs and was observed similarly in the western and eastern districts of Finland with different lifestyles, and it was revealed that it was strongly influenced by the gut bacterial family (Enterobacteriaceae family). Gut bacterial family bacteria are dominant bacteria of the Proteobacteria phylum, facultative anaerobes, and ferment glucose, and many have nitrate reductase activity, including Escherichia, Klebsiella, Proteus, Salmonella, Shigella, Yersinia, etc. Furthermore, groups with a high occupancy rate of the gut bacterial family have a high mortality rate from cancer, especially gastrointestinal cancer (HR 1.80, 95% CI 1.35–2.41) was also shown. These two cohort studies indicate that there is no single gut bacterium that predicts healthy longevity, and that the balance of gut microbiota found in diversity indices is useful. When considering occupancy rates, it seems that a low rate of Bacteroides and gut bacteria is associated with longevity, but it is also known that the gut microbiota of Japanese people has low similarity with Westerners, so careful analysis is needed to determine whether it can be applied to Japanese people. At least in the analysis of gut microbiota data from healthy elderly people in the Kyotango Longevity Cohort Study, a low rate of Bacteroides and Proteobacteria and a high rate of Firmicutes have been observed [3] (Fig. 56.1).