Effects of co-housing and social isolation on the gut microbiota

It is well documented that both social connection patterns and gut microbiota influence individuals' mental and physical health through multiple systems, such as the neuroendocrine, immune, and metabolic systems. Social connections shape the gut microbiota, and altered gut microbiota in turn modulates the host's social behavior in a feedback loop. We therefore hypothesize that the gut microbiota mediates the interaction between social connection patterns and individual well-being. In this pilot study, the effects of co-housing (CH) and social isolation (SI) on shaping gut microbiota community structure were investigated using a mouse model. Twenty-four 3-week-old mice were randomly divided into CH and SI groups (6/sex/group) for 8 weeks. CH mice were socially housed in cages containing 3 mice per cage, while SI mice were individually housed in cages with opaque barriers to prevent interaction. We found that CH increased gut microbiota diversity and stabilized its composition, whereas SI decreased gut microbiota diversity and resulted in more compositional fluctuations-changes previously associated with immunity, metabolism, and neurodevelopment. Meanwhile, this work also demonstrates that including litter controls may be pivotal in establishing a stable baseline for gut microbiota research.