Although it is clear that probiotics improve intestinal barrier function, little is known about
the effects of probiotics on the aging intestine. We investigated effects of 10-week bacterial
supplementation of Lactobacillus plantarum WCFS1, Lactobacillus casei BL23, or
Bifidobacterium breve DSM20213 on gut barrier and immunity in 16-week-old accelerated
aging Ercc1−/Δ7 mice, which have a median lifespan of ~20 weeks, and their wild-type
littermates. The colonic barrier in Ercc1−/Δ7 mice was characterized by a thin (< 10 μm)
mucus layer. L. plantarum prevented this decline in mucus integrity in Ercc1−/Δ7 mice,
whereas B. breve exacerbated it. Bacterial supplementations affected the expression of
immune-related genes, including Toll-like receptor 4. Regulatory T cell frequencies were
increased in the mesenteric lymph nodes of L. plantarum- and L. casei-treated Ercc1−/Δ7
mice. L. plantarum- and L. casei-treated Ercc1−/Δ7 mice showed increased specific
antibody production in a T cell-dependent immune response in vivo. By contrast, the
effects of bacterial supplementation on wild-type control mice were negligible. Thus,
supplementation with L. plantarum – but not with L. casei and B. breve – prevented the
decline in the mucus barrier in Ercc1−/Δ7 mice. Our data indicate that age is an important
factor influencing beneficial or detrimental effects of candidate probiotics. These findings
also highlight the need for caution in translating beneficial effects of probiotics observed
in young animals or humans to the elderly.
