Effects of dietary-fiber levels on RANK/RANKL/OPG expression in the appendix of weanling rabbits

Background/purposeThe dietary fiber can regulate the intestinal mucosal immunity, and the M cell is the portal for initiating mucosal immunity. We investigated the effects of dietary fiber on the transport of Escherichia coli to assess the function of microfold (M) cells in the appendix.MethodA total of 150 New Zealand rabbits were fed three diets (high fiber (HF): 31.72%; control: 37.36%; low dietary fiber (LF): 41.84%; neutral detergent fiber (NDF). An infection model was established in vivo using E. coli containing green fluorescent protein as the indicator in appendix loops. Samples were collected before and after inoculation with indicator for 10, 30, or 60 min. The M cells number, differentiation-related genes and proteins were monitored by respectively using immunofluorescence, Q-PCR and Western-blot.ResultsThe number of M cells in HF group was significantly higher than that of LF group before and at 10 min, 30 min post injection with E.coli (P < 0.01), which has an opposite at 60 min. The number of fluorescent E. coli transported across the appendix was significantly increased in the HF group (P < 0.01) compared with the LF group at 30 min (P < 0.001); expression of RANKL gene and protein levels were no difference between HF and LF group. The variation tendency of RANK, OPG genes and proteins were consistent with the change of M cell transport indicator number in different time points.ConclusionOur study showed that a high-fiber diet can increase number of M cells and speed up antigen transfer under regulation of ANKL/OPG/RANK system.