Gut microbiota in healthy and unhealthy long-living people.

The human gut microbiota in long-living people has been characterized, however, its metabolic potential is still largely unknown in this group. In this study, the gut microbiota was assessed in 37 Chinese long-living participants (aged 90 + years) by metagenomic sequencing of stool samples. Participants were categorized into two groups, healthy long-living (n = 28) and unhealthy long-living (n = 9). Gut microbiota composition and function were compared among these two groups. We found that the gut microbiota in the healthy long-living group was significantly separated from the unhealthy group. The healthy long-living group contained a higher abundance of Bacteroidetes and more functional pathways in energy metabolism, glycan biosynthesis and metabolism, metabolism of cofactors and vitamins, and biosynthesis of other secondary metabolites. The unhealthy group contained a higher abundance of Streptococcus and other pathogenic bacteria, and also contained more functional pathways for xenobiotics biodegradation and metabolism than the healthy group. Additionally, the unhealthy group had decreased levels of carbohydrate-active enzymes, including host-glycan and fiber degrading enzymes, and an increase in starch-degrading enzymes. In conclusion, the gut microbiota of unhealthy long-living people contains more pathogenic bacteria, and the overall gut microbiota may be in an unhealthy state, "dysbiosis", which leads to a decrease in carbohydrate digestion, glycan and thiamine (B1) metabolites, and fatty acid biosynthesis.