Volume 122, Issue 4, Pages 948-956 (April 2002) Dietary sphingomyelin suppresses intestinal cholesterol absorption by decreasing thermodynamic activity of cholesterol monomers  Erik R.M. Eckhardt, * ,‡,§, David Q.–H. Wang, *,§, Joanne M. Donovan, *,‡,§, Martin C. Carey, *,§  Gastroenterology  Volume 122, Issue 4, Pages 948-956 (April 2002) DOI: 10.1053/gast.2002.32539 Copyright © 2002 American Gastroenterological Association Terms and Conditions

Fig. 1 Influence of PL class on cholesterol At in solutions with TC plus EYPC, DPPC, or MSM and cholesterol (total lipid concentration 1 g/dL), at various TC/(TC + PL) ratios. The upper panel shows results with systems containing 1% cholesterol, the lower panel with systems containing 3% cholesterol (note the difference in scales of the vertical axes). All bars represent the means of 4 experiments ± SEM; the asterisks indicate statistically significant differences between groups. Cholesterol At increases with increasing TC/(TC + PL) ratio and is significantly lower in systems with MSM and DPPC compared with EYPC. All DPPC-containing systems were turbid and contained multilamellar vesicles upon examination by polarizing light microscopy. EYPC-containing systems were optically clear (indicating absence of multilamellar vesicles), except at 3% cholesterol and TC/(TC + PL) = 0.5. MSM-systems were optically clear only at 1% cholesterol and TC/(TC + PL) > 0.5. Gastroenterology 2002 122, 948-956DOI: (10.1053/gast.2002.32539) Copyright © 2002 American Gastroenterological Association Terms and Conditions

Fig. 2 Influence of PL class on cholesterol monomer uptake by monolayers of Caco-2 cells (normalized per mg cell protein) from model solutions containing TC, cholesterol, and either MSM or EYPC (total lipid concentration 1 g/dL; n = 4; means ± SEM). The upper panel shows results with systems containing 1% cholesterol, the lower panel with systems containing 3% cholesterol (note the difference in scales of the vertical axes). Statistically significant differences between groups are indicated with an asterisk. MSM decreases cholesterol uptake significantly at all dose levels except TC/(TC + PC) = 0.5 with 3% cholesterol. Gastroenterology 2002 122, 948-956DOI: (10.1053/gast.2002.32539) Copyright © 2002 American Gastroenterological Association Terms and Conditions

Fig. 3 Relationship between At and its uptake by Caco-2 cells. The upper panel displays results obtained with systems containing 1% cholesterol (R2 = 0.97; P < 0.0001), the lower panel with systems containing 3% cholesterol (R2 = 0.86; P < 0.001). Each point represents the mean of 4 independent experiments, with the error bars indicating ±SD. Open symbols represent mixtures with added MSM; closed symbols represent mixtures with added EYPC. There is a marked curvilinear correlation between cholesterol At and cholesterol uptake by Caco-2 cells. Gastroenterology 2002 122, 948-956DOI: (10.1053/gast.2002.32539) Copyright © 2002 American Gastroenterological Association Terms and Conditions

Fig. 4 Effects of PL feeding on small intestinal cholesterol absorption by male C57L mice. The X-axis shows amount (in % of dry weight) of PL added to mouse chow. The Y-axis represents percent decrease in cholesterol absorption compared with C57L mice on standard chow. At 0.5% and 5% levels, both MSM- and DPPC-enrichment led to highly significant decreases in intestinal cholesterol absorption (P < 0.001 and P < 0.005, respectively). At 0.1% dietary enrichment with MSM, there was also a significant decrease in cholesterol absorption (P < 0.05). In contrast, even large amounts of EYPC did not alter intestinal cholesterol absorption in either direction. All bars represent results of the means of 6 animals ± SEM. The asterisks indicate statistically significant decreases compared with mice acting as their own controls. Gastroenterology 2002 122, 948-956DOI: (10.1053/gast.2002.32539) Copyright © 2002 American Gastroenterological Association Terms and Conditions