Reviewing the Contribution of the Gut Microbiome to Neurodegeneration
The state of the gut microbiome is probably as influential as the state of physical fitness when it comes to effects on long-term health. With age the balance of microbial populations shifts for the worse, in fact one of the earlier detrimental aspects of aging. Studies suggest that meaningful changes are in evidence by the time someone reaches their mid-30s. Beneficial species producing metabolites that contribute to tissue function diminish in number, while harmful species that provoke chronic inflammation increase in number.
Fortunately, it is possible to adjust the gut microbiome, to rejuvenate it and restore a more youthful balance of microbial populations, via approaches such as fecal microbiota transplantation from a young donor to an older patient. In short-lived species, this improves health and even extends life span. Fecal microbiota transplantation is used in the clinic in a limited way, but it remains to be seen as to when this and other forms of therapy that may reverse the aging of the gut microbiome become more widely available. As of the moment, it is largely self-experimenters who are performing this sort of treatment upon themselves.
As the world population ages, the burden of age-related health problems grows, creating a greater demand for new novel interventions for healthy aging. Advancing aging is related to a loss of beneficial mutualistic microbes in the gut microbiota caused by extrinsic and intrinsic factors such as diet, sedentary lifestyle, sleep deprivation, circadian rhythms, and oxidative stress, which emerge as essential elements in controlling and prolonging life expectancy of healthy aging. This condition is known as gut dysbiosis, and it affects normal brain function via the brain-gut microbiota axis, which is a bidirectional link between the gastrointestinal tract and the central nervous system (CNS) that leads to the emergence of brain disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS), and frontotemporal dementia.
A substantial amount of research has been conducted on the role and abundance of the intestinal microbiome as well as the implications for maintaining a healthy state. Gut microbiota is an ecosystem metabolic of a million different microorganisms living in the gastrointestinal tract and forming a symbiotic connection with the host. Because the gut microbiota helps to maintain physiological homeostasis, alterations in microbiome abundance taxa cause intestinal dysbiosis related to numerous pathological conditions, including neurodegenerative diseases. Thus, microbiota-based therapies emerge as a potential therapeutic target, including prebiotic or probiotic administration, nutrition, and physical activity to reshape the gut microbiota.
Here, we review the role of the gut microbiome in aging and neurodegenerative diseases, as well as provide a comprehensive review of recent findings from preclinical and clinical studies to present an up-to-date overview of recent advances in developing strategies to modulate the intestinal microbiome by probiotic administration, dietary intervention, fecal microbiota transplantation (FMT), and physical activity to address the aging process and prevent neurodegenerative diseases. The findings of this review provide researchers in the fields of aging and the gut microbiome design innovative studies that leverage results from preclinical and clinical studies to better understand the nuances of aging, gut microbiome, and neurodegenerative diseases.