The intestinal epithelium is a significant barrier to oral absorption of hydrophilic compounds, and their passage through the intercellular space is restricted by the tight junctions. In this study we found that hyperosmosis is a significant factor altering paracellular transport in Caco-2 cell monolayers. Osmotic regulators, such as sodium chloride, mannitol, and raffinose, decreased transepithelial electrical resistance and enhanced lucifer yellow permeability. The effect of these osmotic regulators on Caco-2 cell monolayers was not likely to be caused by gross cytotoxicity. Although certain amino acids and oligosaccharides have been reported to have specific tight junction-modulating activity, we found that the increased paracellular permeability of Caco-2 monolayers induced by these compounds was at least partly due to the increased osmotic pressure of the test solutions. These findings provide a new potential precaution in the evaluation of paracellular permeability-modulating substances using the Caco-2 cell monolayer system.
We developed a beverage that forms a gel containing gas bubbles in the stomach and induces satiety. In a preliminary experiment, we confirmed that when a carbonated beverage containing any one of three types of ionic polysaccharides was mixed with artificial gastric juice, it resulted in the formation of a gel containing gas bubbles. Among the three types of polysaccharides referenced above, low methoxyl pectin (LM pectin) was identified as being the optimal for preparation of the test beverage in this study. Both static evaluation using a vessel and dynamic evaluation using the Gastric Digestion Simulator (GDS) revealed that the volume of the bubble-containing gel remained relatively stable with time. Presence of the bubble-containing gel in the stomach following consumption of the carbonated beverage containing LM pectin was confirmed in a clinical Magnetic Resonance Imaging (MRI) study. Consumption of this test beverage resulted in a greater increase of the intragastric volume than consumption of the same amount of water. Moreover, in the satiety questionnaire, the subjects reported a higher degree of satiety following consumption of the beverage than following consumption of an equal amount of water. These results indicate that when this test beverage, a carbonated beverage containing LM pectin that forms a bubble-containing gel in the stomach, is consumed, the stomach becomes distended, inducing a feeling of satiety.
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