Correlations Between Sarcopenia and Measurable Gut Microbiome Characteristics
The composition of the gut microbiome is influential on long term health and aging, possibly to a similar degree to lifestyle choices such as degree of physical exercise. Data shows that the relative sizes of microbial populations in the gut change with age in ways that provoke greater inflammation and reduce the production of beneficial metabolites. Conversely, it appears possible to produce lasting change in the gut microbiome, such as via fecal microbiota transplantation or therapies that cause the immune system to ramp up its destruction of problematic microbial species.
These approaches have yet to make their way into human medicine in any sizable way because regulators require a great deal more characterization of the microbiome and its alterations than presently exists. For example, given that microbial contributions to disease are far from fully mapped, and may proceed slowly over time, it is presently impossible to state in certainty that a fecal microbiota transplant will not introduce some novel problem for the recipient.
Nonetheless, there is considerable motivation to find ways to engineer therapeutic changes in the gut microbiome. Today's open access paper is one example of a continued flow of reviews and findings that report on distinct features of the gut microbiome in patients suffering from specific age-related conditions. Find ways to remove those features from the microbiome may turn out to be a viable approach to therapy for much of the panoply of age-related dysfunction and decline.
Sarcopenia, characterized by age-related decline in muscle mass and function, significantly increases the risk of adverse outcomes such as impaired quality of life, falls, hip fractures, frailty, hospitalization, disability, and mortality. Individuals with sarcopenia have a higher likelihood of premature mortality compared to their age-matched counterparts. Sarcopenia also strongly predicts disability, defined as limitations in activities of daily living (ADL) and care home admissions. However, it is plausible that age-associated modifications in the gut microbiota and muscle tissue composition could be driven by shared underlying processes, such as chronic inflammation, dysfunction of the immune system, and changes in hormone levels, which could influence both microbiota alterations and the onset of sarcopenia.
Currently, there is no single effective therapeutic intervention for sarcopenia. The 'gut-muscle axis', which explores how the gut microbiome affects muscle mass, strength, and function in older adults, plays a crucial role in both the prevention and management of sarcopenia. Previous research indicates that diet composition and the gut microbiome change with age and are correlated with muscle mass decline, thereby impacting physical performance. Advanced age leads to gut microbiome dysbiosis, characterized by altered microbial diversity, predominant bacteria, and reduced beneficial bacterial metabolites. These biological processes, particularly those related to inflammation and the immune system, are greatly influenced by the gut microbiome. Studies show differences in gut microbiome composition, measured using RNA sequencing, between older and younger participants, marked by variations in alpha diversity//en.wikipedia.org/wiki/Alpha_diversity">alpha diversity (species diversity within a sample) and beta diversity (species diversity between samples). Animal studies support these findings, suggesting that variations in the gut microbiome and metagenome influence biological processes such as inflammation, nutrient bioavailability, and lipid metabolism, contributing to age-related muscle decline.
This review provides insight into potential novel interventions for sarcopenia prevention and treatment. A systematic search was conducted for studies published between 2002 and 2022 involving participants aged 50+. Studies were included if they assessed sarcopenia using at least one measure of muscle mass (skeletal muscle mass, bioelectrical impedance analysis, MRI), muscle strength, or muscle performance. The microbiome was measured using at least RNA/DNA sequencing or shotgun metagenomic sequencing. Twelve studies were analyzed. Findings revealed that a higher abundance of bacterial species such as Desulfovibrio piger, and Clostridium symbiosum and reduced diversity of butyrate-producing bacteria was associated with sarcopenia severity, as indicated by decreased grip strength, muscle mass, or physical performance. The gut microbiome plays a significant role in age-related muscle loss. Probiotics, prebiotics, and bacterial products could be potential interventions to improve muscle health in older adults.