Recent population studies have significantly advanced our understanding of how age shapes the gut microbiota. However, the actual role of age could be inevitably confounded due to the complex and variable environmental factors in human populations. A well-controlled environment is thus necessary to reduce undesirable confounding effects, and recapitulate age-dependent changes in the gut microbiota of healthy primates. Herein we performed 16S rRNA gene sequencing, characterized the age-associated gut microbial profiles from infant to elderly crab-eating macaques reared in captivity, and systemically revealed the lifelong dynamic changes of the primate gut microbiota. While the most significant age-associated taxa were mainly found as commensals such as Faecalibacterium, the abundance of a group of suspicious pathogens such as Helicobacter was exclusively increased in infants, underlining their potential role in host development. Importantly, topology analysis indicated that the network connectivity of gut microbiota was even more age-dependent than taxonomic diversity, and its tremendous decline with age could probably be linked to healthy aging. Moreover, we identified key driver microbes responsible for such age-dependent network changes, which were further linked to altered metabolic functions of lipids, carbohydrates, and amino acids, as well as phenotypes in the microbial community. The current study thus demonstrates the lifelong age-dependent changes and their driver microbes in the primate gut microbiota, and provides new insights into their roles in the development and healthy aging of their hosts.

Emerging evidence has been reported to support the involvement of the gut microbiota in the host’s blood lipid and hyperlipidemia (HLP). However, there remains unexplained variation in the host’s blood lipid phenotype. Herein a nonhuman primate HLP model was established in cynomolgus monkeys fed a high-fat diet (HFD) for 19 months. At month 19%, 60% (3/5) of the HFD monkeys developed HLP, but surprisingly 40% of them (2/5) exhibited strong tolerance to the HFD (HFD-T) with their blood lipid profiles returning to normal levels. Metagenomic analysis was used to investigate the compositional changes in the gut microbiota in these monkeys. Furthermore, the relative abundance of Megasphaera remarkably increased and became the dominant gut microbe in HFD-T monkeys. A validation experiment showed that transplantation of fecal microbiota from HFD-T monkeys reduced the blood lipid levels and hepatic steatosis in HLP rats. Furthermore, the relative abundance of Megasphaera significantly increased in rats receiving transplantation, confirming the successful colonization of the microbe in the host and its correlation with the change of the host’s blood lipid profiles. Our results thus suggested a potentially pivotal lipid-lowering role of Megasphaera in the gut microbiota, which could contribute to the variation in the host’s blood lipid phenotype.

23Recent population studies have significantly advanced our understanding of how age shapes 24 the gut microbiota. However, the actual role of age could be inevitably confounded due to 25 varying environmental factors in human populations. A well-controlled environment is thus 26 necessary to reduce undesirable cofounding effects, and recapitulate age-dependent 27 taxonomic and functional changes in the healthy primate gut microbiota. Herein we 28 performed 16S rRNA gene sequencing, characterized age-associated gut microbial profiles 29 from infant to elderly crab-eating macaques reared in captivity, and systemically revealed 30 lifelong dynamic changes of primate gut microbiota in the model. While the most 31 significantly age-associated gut microbial taxa were mainly found in commensals such as 32Faecalibacterium, a set of suspicious pathogens such as Helicobacter were exclusively 33 enriched in infants, pointing to their potential role in host development. Importantly, topology 34 analysis indicated that the connectivity of gut microbial network was even more 35 age-dependent than taxonomic diversity, with its tremendous decline probably linked to the 36 host's healthy aging. NetShift analysis identified Prevotella 9, Rikenellaceae RC9 gut group 37 and Megasphaera as key drivers during gut microbiota maturation and development, actively 38 involved in age-dependent changes in phenotypes and functions of the gut microbial 39 community. The current study demonstrates lifelong age-dependent changes in healthy 40 primate gut microbiota. Our findings indicate potential importance of appropriate exposure to 41 suspicious pathogens in infant development. The age-associated baseline profiles and driver 42 microbes of primate gut microbiota in the current study could provide new insight into its 43 role in the host's development and healthy aging. 44