A Unique Gut Microbiome-Physical Function Axis Exists in Older People with HIV: An Exploratory Study.

Impairments in physical function and increased systemic levels of inflammation have been observed in middle-aged and older persons with HIV (PWH). We previously demonstrated that in older persons, associations between gut microbiota and inflammation differed by HIV serostatus. To determine whether relationships between the gut microbiome and physical function measurements would also be distinct between older persons with and without HIV, we reanalyzed existing gut microbiome and short chain fatty acid (SCFA) data in conjunction with previously collected measurements of physical function and body composition from the same cohorts of older (51-74 years), nonfrail PWH receiving effective antiretroviral therapy (N = 14) and age-balanced uninfected controls (N = 22). Associations between relative abundance (RA) of the most abundant bacterial taxa or stool SCFA levels with physical function and body composition were tested using HIV-adjusted linear regression models. In older PWH, but not in controls, greater RA of Alistipes, Escherichia, Prevotella, Megasphaera, and Subdoligranulum were associated with reduced lower extremity muscle function, decreased lean mass, or lower Short Physical Performance Battery (SPPB) scores. Conversely, greater RA of Dorea, Coprococcus, and Phascolarctobacterium in older PWH were associated with better muscle function, lean mass, and SPPB scores. Higher levels of the SCFA butyrate associated with increased grip strength in both PWH and controls. Our findings indicate that in older PWH, both negative and positive associations exist between stool microbiota abundance and physical function. Different relationships were observed in older uninfected persons, suggesting features of a unique gut-physical function axis in PWH.