Gut Microbiome Changes Correlate with Low Grip Strength in Older People
At least when considering study populations as a whole rather than individuals on their own, grip strength remains a decent proxy measure for risk of mortality and age-related disease. Loss of muscle mass and strength occurs for everyone in later life, leading to the condition known as sarcopenia, and is sensitive to many of the important mechanisms of aging, such as chronic inflammation. Low grip strength is likely indicative of a higher burden of cell and tissue damage throughout the body, because the mechanisms that contribute to loss of strength, such as inflammation, also contribute to other declines, forms of damage, and loss of function.
As noted in today's open access paper, there is a growing interest in age-related changes in the relative sizes of microbial populations making up the gut microbiome. With age there is a loss of beneficial metabolite production and an increase in pro-inflammatory microbial activity. This is thought to provide a significant contribution to degenerative aging, an influence on long-term health that is likely as sizable as the effects of lifestyle choices related to diet and physical fitness. Thus one might expect to see, as here, correlations between the aging of the gut microbiome and loss of grip strength in later life.
Handgrip strength (HGS), which represents global muscle strength, is a powerful indicator of disability and mortality in older adults; it is also used for the diagnosis of possible or probable sarcopenia and physical frailty. This study aimed to explore the metabolic mechanisms and potential biomarkers associated with declining HGS among older adults. We recruited 15 age- and environment-matched inpatients (age, 77-90 years) with low or normal HGS. Liquid chromatography-mass spectrometry (LC-MS) and 16S ribosomal DNA (rDNA) gene sequencing were performed to analyze the metabolome of serum and stool samples and the gut microbiome composition of stool samples. Spearman's correlation analysis was used to identify the potential serum and fecal metabolites associated with HGS.
We assessed the levels of serum and fecal metabolites belonging to the class of cinnamic acids and derivatives and reported that the levels of carboxylic acids and their derivatives decreased in the low-HGS group. Serum levels of microbial metabolites, including cinnamoylglycine, 4-methoxycinnamic acid, and (e)-3,4,5-trimethoxycinnamic acid, were positively correlated with HGS. We found that gut microbial α-diversity was significantly higher in the low-HGS group, whereas higher β-diversity was observed in the normal group. The relative abundances of the genera Parabacteroides and Intestinibacter increased significantly in the low-HGS group and were negatively correlated with the serum levels of cinnamoylglycine. The identified metabolites whose levels were markedly altered, and intestinal flora associated with these metabolites suggest the potential metabolic underpinnings for HGS and provide a basis for the further identification of biomarkers of muscle strength decline in older adults.