(A) Experimental schematic. Three monogamous MRD lineage or MHFD lineage F1 breeder cages were used to establish MRD- and MHFD-descendant F2 generations, respectively. Upon weaning at 3 weeks old, all mice were given drinking water containing 108 CFU/mL L. reuteri daily through behavior assessment.
(B) Analysis of the reciprocal social interaction times between pairs revealed no differences between males (male MHFD + L reuteri versus MRD + L. reuteri: t(22) = 0.01855, p = 0.9854), with increased interaction times between F2 MHFD + L. reuteri females compared with F2 MRD + L. reuteri females (female MHFD + L. reuteri versus MRD + L. reuteri: t(25) = 6.340, p < 0.0001).
(C and D) (C) F2 male MHFD + L. reuteri offspring show typical preference during sociability (MRD: t(56) = 4.515, p < 0.0001; MHFD: t(56) = 4.373, p = 0.0001) and (D) social novelty (MRD: t(28) = 5.472, p < 0.0001; MHFD: t(28) = 4.28, p = 0.0004).
(E–H) (E) Likewise, MHFD + L. reuteri F2 female offspring show a statistically significant preference during sociability (MRD: t(36) = 2.633, p = 0.0246; MHFD: t(36) = 4.253, p = 0.0003) and (F) preference for social novelty (MRD: t(18) = 0.7226, p = 0.7228; MHFD: t(18) = 3.763, p = 0.0028). Representative MRD + L. reuteri (light blue) or MHFD + L. reuteri (light orange) track plots for (G) males and (H) females, respectively. Bar graphs show mean ± SEM with individual data points.
(I) PCoA of unweighted UniFrac distances from the averaged rarefied 16S rRNA gene amplicon sequencing dataset (5,508 reads/sample; n = 1,000 rarefactions) revealed statistically significant clusters based on diet (p = 0.001, R2 = 0.148).
(J–L) L. reuteri administration differentially affects MRD and MHFD F2 gut microbiome alpha diversity, as measured by observed OTUs (MHFD F2 + L. reuteri versus MRD F2 + L. reuteri: t(50) = 5.285, p < 0.0001), Chao1 index (MHFD F2 + L. reuteri versus MRD F2 + L. reuteri: t(52) = 4.143, p = 0.0001), and Shannon index (MHFD F2 + L. reuteri versus MRD F2 + L. reuteri: t(50) = 4.436, p < 0.0001). Bar graphs show mean ± SEM with individual data points representing biological replicates. B, N = 10–16 pairs per group; (C–F) N = 10–15 subjects per group; (I–L) N = 24–28 subjects per group.