Dietary cellulose attenuates intestinal inflammation by promoting microbiota maturation and gut barrier function

It is almost fifty years ago that dietary fibres were recognized to be healthpromoting. However, the cellular and molecular mechanisms of health-promoting effects are not yet well understood, especially with respect to dietary cellulose, the most common biopolymer on earth. In this study, the impact of dietary cellulose on the intestinal microbiota, immune and epithelial cell functions in health and disease was examined. Cellulose served as a potential substrate for intestinal microbes and promoted the maturation of the gut microbiota. Moreover, the lack of this fibre skewed immune responses towards inflammation, decreased the transcription of antimicrobial REG3g and increased the susceptibility to acute colitis. One of the genera most affected by cellulose deprivation was Alistipes. Analysis of Alistipes finegoldii, a dominant representative of this genus, revealed that this microbe mimics some of the molecular and cellular effects of dietary cellulose in a gnotobiotic mouse model. We found that A. finegoldii is equipped with cellulolytic enzymes and that intestinal colonization led to enhanced expression of IL-22 and REG3g. Functionally, A. finegoldii was able to restore intestinal barrier function during acute colitis. Collectively, this study supports epidemiological observations and gives a rationale for the health promoting effects of dietary cellulose. Since the intake of fibres in most western societies is very low, this study provides a scientific rationale to set up recommendations on fibre consumption, with special emphasis on cellulose, in order to improve public health.