Uptake of Vitamins D(2), D(3), D(4), D(5), D(6), and D(7) Solubilized in Mixed Micelles by Human Intestinal Cells, Caco-2, an Enhancing Effect of Lysophosphatidylcholine on the Cellular Uptake, and Estimation of Vitamins D’ Biological Activities

Vitamins D have various biological activities, as well as intestinal calcium absorption. There has been recent concern about insufficient vitamin D intake. In addition to vitamins D(2) and D(3), there are lesser-known vitamins D(4)–D(7). We synthesized vitamins D(5)–D(7), which are not commercially available, and then evaluated and compared the mixed micelles-solubilized vitamins D uptake by Caco-2 cells. Except for vitamin D(5), the uptake amounts of vitamins D(4)–D(7) by differentiated Caco-2 cells were similar to those of vitamins D(2) and D(3). The facilitative diffusion rate in the ezetimibe inhibited pathway was approximately 20% for each vitamin D type, suggesting that they would pass through the pathway at a similar rate. Lysophosphatidylcholine enhanced each vitamin D uptake by approximately 2.5-fold. Lysophosphatidylcholine showed an enhancing effect on vitamin D uptake by reducing the intercellular barrier formation of Caco-2 cells by reducing cellular cholesterol, suggesting that increasing the uptakes of vitamins D and/or co-ingesting them with lysophosphatidylcholine, would improve vitamin D insufficiency. The various biological activities in the activated form of vitamins D(4)–D(7) were estimated by Prediction of Activity Spectra for Substances (PASS) online simulation. These may have some biological activities, supporting the potential as nutritional components.