Possible correlation between gut microbiota and immunity among healthy middle-aged and elderly people in southwest China

The present study was conducted to investigate the possible association between gut microbes and immunity among healthy middle-aged and elderly individuals in southwest China. A total of 148 healthy adults aged ≥ 50 years were divided into two age groups: middle-aged group (50-59 years; n = 67, 54.13 ± 3.32) and elderly group (≥ 60 years; n = 81, 64.70 ± 3.93). Blood samples were collected to measure serum immune and biochemical indices. Gut microbiota compositions of the groups were characterized on the basis of faecal DNA using 16S rRNA gene sequencing. Among the detected gut microbes, the presence of was negatively correlated with age in both groups. In the middle-aged group, age was negatively correlated with the presence of and . In the elderly group, was present at significantly higher levels; age was negatively correlated with the presence of , and the Chao index, whereas positively correlated with the presence of In the middle-aged group, the presence of was positively correlated with serum immunoglobulin G (IgG) levels and the percent of CD8 T cells and negatively correlated with the CD4 /CD8 ratio; the presence of was negatively correlated with IgM levels; ratio was positively correlated with IgG and IgM levels and Simpson index was negatively correlated with the percent of CD8 T cells and positively correlated with CD4 /CD8 ratio. In the elderly group, the presence of (identified as genus ) was positively correlated with IgA levels and the percent of CD8 T cells and negatively correlated with the percent of CD4 T cells and CD4 /CD8 ratio; the Chao index and observed species were positively correlated with IgA levels. These results indicated that ageing could significantly correlate with the composition of gut microbiota in terms of quantity and quality. Changes in gut microbiota caused by ageing, characterized by decreased levels, might be associated with immunosenescence among healthy middle-aged and elderly people in southwest China.