Good Microbiome: A sign of ‘healthy aging’

The microbiome is a community of microorganisms inhabiting a specific environment. Microorganisms living inside gut make up a gut microbiome. In humans, the microbiome is often discussed in the context of the gut, but also includes microbiomes on the skin, in the mouth, and elsewhere.

Long-lived individuals, such as centenarians, are examples of highly successful aging. The gut microbiome contributes a lot to it, increasing evidence suggests that the gut microbiome lies at the core of many age-associated changes, including immune system dysregulation and susceptibility to diseases.[1],[2],[3] In fact, gut microbiome differences among individuals emerge much earlier than expected and have prolonged effects on health.

Microbiome across different life spans

The development of the gut microbiome during foetal is likely exposed to microbial metabolites from the mother. In infancy, microbiomes are less diverse, primarily involving facultative anaerobic microbes like Enterobacteriaceae and Streptococcus. The adult microbiome appears to be highly personalised and stable, it is affected by various external factors such as diet and physical activities. Compared to young people, old people show a lower diversity of microbes and higher in abundance. [4]

Microbiome early development in infancy and childhood

The transfer of microorganisms occurs while infants are given birth and is continuously affected by whether the baby is breast or formula fed. Infants delivered by early c-section show an early acquisition of skin flora, and a delayed acquisition of obligatory anaerobic organisms. [5],[6],[7] Moreover, children born via C-section tended to have a higher need for antibiotics due to respiratory infections in the first year of life because of the differences in acquisition of bacteria. Delivery mode influences neurodevelopment as well, and it likely has long-lasting consequences into adulthood. Breast-fed infants have distinct microbiomes compared to formula-fed ones, and more pathways associated with fatty acid biosynthesis. Breast milk also offers important initial immune protection to the infant through transmission of prebiotics, which can promote probiotic growth. Optimizing the gut microbiome in infancy could also reduce the incidence of developmental disability. [8]

Microbiome signature in elders

The decrease in gut microbiota diversity and alterations in specific core microbial groups serve as indicators of aging.[9],[10] Bifidobacteria and Lactobacilli are involved in the maintenance of immune tolerance, and they show lower abundance in the aging microbiome, while more strains linked to inflammation stimulation, such as Enterobacteriaceae and Clostridium, are found.[11],[12] An aging microbiome increases the abundance of pathways associated with short-chain fatty acids (SCFAs) degradation and TMAO synthesis, which contribute to an increased abundance of pathobionts.[13] The Microbiome is highly dependent on the health status of the old adults. The degradation or “unhealthy aging” of the microbiome is not an inevitable process. Microbiome profiles are quite similar between healthy young adults and healthy old people, or even better in healthy long-lived individuals.[14],[15] However, microbial taxa still associated with healthy aging, as centenarians show a microbiome signature with high diversity and abundance of beneficial strains such as Akkermansia and Faecalibacterium.[16],[17] The oldest-old adults’ unique is the ability to maintain or upregulate anti-inflammatory activity despite a concomitant uptick of pro-inflammatory activity that occurs in all older adults, and it is supported by the increases in health-promoting microbial taxa.[18] The gut microbial function in centenarians also revealed heightened central metabolic capacities, which lead to an increase in SCFAs. Microbial metabolism of compounds in the diet also likely impacts health and age-related disease. Age-associated shifts in the gut microbiome contribute to an increased possibility of aged individuals to certain diseases, including CVD, obesity, cancers, diabetes, skin aging and neurodegenerative diseases.[19] Maintaining a balanced composition of different gut microbial communities for sustaining gut microbiota stability is important.[20]

Regulation of aging gut microbiota

Prebiotics and probiotics regulate the gut microbial community and prevent age-related changes. For elderly people, maintaining a healthy gut microbiome requires focusing on a fibre-rich diet, avoiding unnecessary antibiotics, and taking prebiotic/probiotic supplements as recommended by healthcare providers.[21]

Summary

More research is needed to identify which specific microbes are most important for healthy aging, and to understand how they interact with the immune system and affect metabolism. 

Sources

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