The abundance of Akkermansia muciniphila (AM) in the colon is inversely correlated with morbidities such as obesity, diabetes, and inflammatory bowel disease. While animal studies using morbid mice reported that AM improves the gut-barrier function, the mechanisms underlying the effects of AM proliferation on colon physiology remain unclear. We examined the effects of AM on the colon physiology of healthy rats using skate-skin mucin (SM) as AM-targeting prebiotics. Rats were fed either a control diet or a diet supplemented with 1.2% SM for 2 or 3 weeks. The results showed that SM promoted AM proliferation in the cecum and colon, and significantly reduced the thickness of the colon mucin layer by over 40% compared with rats fed the control diet. AM proliferation did not affect gut permeability (plasma lipopolysaccharide influx, urinary chromium excretion rate) or the amount of tight junction proteins in the colon. Moreover, we investigated the effects of long-term SM intake (8 weeks) on glucose tolerance and the effects of SM intake (2 weeks) in rats with dextran sulfate sodium (DSS)-induced colitis. The results showed that SM-induced AM proliferation did not affect either glucose tolerance or DSS-induced colitis. AM proliferation per se was found to be neutral, at least in healthy rats. Therefore, it is speculated that the improvement of the intestinal barrier function by AM may occur solely under pathological conditions, depending on the strain and diet composition of the animals.
Key Words: Akkermansia muciniphila, mucus layer, gut permeability, skate-skin mucin, healthy rats |
