Fermentable dietary fibers such as inulin and oligosaccharides increase production of mucin (which is the main constituent of mucus) but reduce the cecal pH in rats. The total quantity of cecal mucin represents the difference between mucin synthesized by goblet cells and the mucin degraded by enteric bacteria. However, a reduction in mucinase activity secondary to reduced pH may contribute to increased cecal mucin. The cecal pH does not decrease following the intake of beet fiber (B); therefore, the cause of increased cecal mucin secondary to B intake may differ from increased mucin caused by other dietary fibers. We investigated the effect of B on mucin production through the measurement of cecal pH, mucin quantity, mucin core protein gene expression, and mucinase activity. Rats were fed either a purified diet (control) or a diet containing 2.5%, 5%, or 10% B for 14 days. Weight gain and food intake were unaffected by the diet. Cecal pH was reduced in a dose-dependent manner in rats fed the B diet (2.5B: p=0.024, 5B: p<0.001, 10B: p<0.001); however, the cecal pH was at least 7.05. Cecal mucin increased in a dose-dependent manner in rats fed the B diet (5B: p=0.005, 10B: p<0.001). Rats fed the B diet showed a dose-dependent increase in Muc2 gene expression (10B: p=0.035) and also a significant dose-dependent increase in mucinase activity (2.5B: p=0.049, 5B: p=0.015, 10B: p=0.011).
Key words: beet fiber, cecum, mucin, mucinase, rats |
