α-Amylase expressed in human small intestinal epithelial cells is essential for cell proliferation and differentiation.

α-Amylase, which plays an essential role in starch degradation, is expressed mainly in the pancreas and salivary glands. Human α-amylase is also detected in other tissues, but it is unclear whether the α-amylase is endogenously expressed in each tissue or mixed exogenously with one expressed by the pancreas or salivary glands. Furthermore, the biological significance of these α-amylases detected in tissues other than the pancreas and salivary glands has not been elucidated. We discovered that human α-amylase is expressed in intestinal epithelial cells and analyzed the effects of suppressing α-amylase expression. α-Amylase was found to be expressed at the second-highest messenger RNA level in the duodenum in human normal tissues after the pancreas. α-Amylase was detected in the cell extract of Caco-2 intestinal epithelial cells but not secreted into the culture medium. The amount of α-amylase expressed increased depending on the length of the culture of Caco-2 cells, suggesting that α-amylase is expressed in small intestine epithelial cells rather than the colon because the cells differentiate spontaneously upon reaching confluence in culture to exhibit the characteristics of small intestinal epithelial cells rather than colon cells. The α-amylase expressed in Caco-2 cells had enzymatic activity and was identified as AMY2B, one of the two isoforms of pancreatic α-amylase. The suppression of α-amylase expression by small interfering RNA inhibited cell differentiation and proliferation. These results demonstrate for the first time that α-amylase is expressed in human intestinal epithelial cells and affects cell proliferation and differentiation. This α-amylase may induce the proliferation and differentiation of small intestine epithelial cells, supporting a rapid turnover of cells to maintain a healthy intestinal lumen.

Usefulness of conventional glass ionomer cements in an environment of insufficient moisture exclusion.

PURPOSE: Moisture exclusion while treating dental caries can be challenging, and the glass ionomer cements (GICs) used for these procedures are susceptible to water. Few studies have examined the effects of the powder/liquid ratio (PLR) on the physical properties of GICs exposed to water. In this study, the hardness and thickness of the water-susceptible surface layer of three GICs were evaluated. METHODS: Three conventional GICs were mixed in increasing PLRs, and hardness over time was measured under conditions of no water exposure, distilled water exposure, and saliva exposure. Furthermore, the thickness of the water-susceptible layer for each GIC was determined. RESULTS: A water-susceptible layer of approximately 250 µm was evident for all GICs, and the thickness decreased with increasing PLR. GIC hardness increased with increasing PLR in conditions without water for all GIC types. Furthermore, the removal of the water-susceptible layer restored the physical properties of each GIC. CONCLUSION: Overall, the results indicate that conventional GIC restoration with the removal of the water-susceptible surface layer is a feasible strategy for treating dental caries in individuals for whom exclusion of moisture can be difficult.