Microbiome and Metabolome Variation as Indicator of Social Stress in Female Prairie Voles

Abstract

Social isolation is detrimental to the health of social mammals inducing neurochemical and hormonal changes related to depression and anxiety, as well as impairments of cardiovascular and immune functioning. Likewise, perceptions of loneliness are increasingly recognized as detrimental to human psychological well-being, cognitive functioning, and physical health. Few studies, however, have examined the impact of social isolation on the intestinal microbiome and metabolome. To better understand the impact of social isolation on these systems, intestinal microbiota, and the systemic impact via the gut-brain axis, we employed prairie voles. Physiological stress on female prairie voles (n = 22) either with a same-sex sibling (n = 11) or in isolation (n = 11) for four weeks demonstrated behavioral indicators of increased anxiety and depression in isolated voles (p ≤ 0.01). Bacterial DNA from fecal and colon samples, collected at five time points (T_0-4), were sequenced for all nine hypervariable regions of the 16S rRNA gene. Microbiome analyses revealed several differences in gut communities of paired and isolated voles with greater differences at T₄. Notably, several taxa associated with host health including Anaerostipes and Lactobacillaceae were more prevalent in paired voles, whereas several taxa associated with known pathogens (e.g., Staphylococcaceae and Enterococcus) or disease were elevated in isolated animals. Similarly, metabolome analyses suggested isolated voles, when compared to paired animals, exhibited differences in metabolites associated with diabetes and colitis. These findings further contribute to our understanding of the harmful effects of social isolation, which cause perturbations in the gut microbiome and serum metabolites.

Keywords: colitis; gut microbiome; gut–brain axis; prairie voles; social isolation; type two diabetes.

Figure 1

When placed in the elevated plus maze, socially isolated prairie voles exhibited behaviors associated with hyperactivity, anxiety, and depression. (A) Isolated voles exhibited a greater number of center crosses (N = 9, M = 15.667, SEM 2.224) than paired voles (N = 11, M = 10.45, SEM = 1.436). (B) Isolated voles spent less time in the open arms of the EPM (N = 9, M = 41.778, SEM = 6.105) than paired voles (N = 11, M = 56.091, SEM = 6.362). (C) When placed in the FST, isolated voles exhibited increased immobility (N = 11, M = 126.8, SEM = 13.8) compared to paired voles (N = 11, M = 51.5, SEM, 11.7). * denotes statistically significant differences (p < 0.05).

Figure 2

(A) Shannon diversity exhibited a trend toward significance with greater diversity driven by greater diversity being present at T4 than at T2 (p = 0.066). (B) Bray Curtis dissimilarity (p = 0.018), and (C) Jaccard distance (p = 0.001) demonstrate distinct groupings at T4.

Figure 3

Heatmap depicting taxa that exhibited significant changes in abundance between five time points for all animals. Cells in red indicate higher abundance, whereas blue indicates lower abundance. The scale on the right indicates the heatmap scale. For clarity, x-axis labels show information for every other fecal sample included in the analysis. Ruminococcus were not included here, because the higher general abundance of this taxon would offset the scale of the heatmap.

Figure 4

LEfSe analyses revealed differences in the proportional abundance of numerous taxa when the fecal communities of paired and isolated voles were compared at T₀–T₄. (A) At T₀ notable differences include a greater proportional abundance of the phylum Proteobacteria at in paired voles (N = 11) compared to isolated voles (N = 10). (B) At T₁ notable differences include a greater proportional abundance of Bacteroidetes, Prevotella, and Paraprevotella in paired voles (N = 11) compared to isolated voles (N = 11). (C) At T₂ notable differences include a greater proportional abundance of Anaerostipes in paired voles (N = 11) compared to isolated voles (N = 11). (D) At T₃ notable differences include a greater proportional abundance of Anaerostipes in paired voles (N = 11) compared to isolated voles (n = 10). (E) At T₄, notable differences include greater proportional abundances of Lactobacillaceae in paired voles (N = 11) and Bdellovibrionales, Bdellovibrionaceae, and Vampirovibrio in isolated voles (N = 11).

Figure 5

LEfSe analyses demonstrated differential abundance of microbial community members in colons of paired (N = 11) and isolated voles (N = 11). Bacteroidetes, Prevotellaceae, Rhodobacteraceae, Williamwhitmaniaceae, and Amaricoccus exhibited a greater abundance in paired voles and Clavibacter, Sporobacter, and Lawsonibacter in isolated voles.