Purpose: The objective of this study was to determine how a novel hydrophilic phytostanol (FM-VP4) affects the cellular accumulation of [3H]cholesterol in human colon carcinoma (Caco-2) cell monolayers grown in Transwell chambers.
Methods: To determine cellular accumulation of cholesterol and FM-VP4, [3H]cholesterol- containing micelles (50 microM cholesterol containing 1.27x10 (-4)% [3H]cholesterol) or [3H]FM-VP4 (50 microM) was incubated on the apical side of differentiated Caco-2 cell monolayers for 1 to 4 h at 37 degrees C in the absence or presence of increasing concentrations (10-200 microM) of unlabeled FM-VP4 or cholesterol, respectively.
Results: The accumulation of [3H]cholesterol (presented in micelles) into Caco-2 cell monolayers in the presence of 50 microM FM-VP4 was significantly lower (33.7 +/- 7.0%) compared to control (59.8 +/- 5.2%, p<0.05) following 4 h of incubation. Conversely, cholesterol inhibited the accumulation of [3H]FM-VP4, although to a lesser extent, suggesting competition for binding sites. The inhibitory effects of FM-VP4 and cholesterol on each other were detectable after 1 h of incubation and increased with time. The extent of FM-VP4 inhibition of [3H]cholesterol accumulation was consistent whether FM-VP4 was co-incorporated into micelles or added separately in solution, suggesting that FM-VP4 does not elicit its effects through inhibition of cholesterol incorporation into micelles. In addition, pancreatic lipase activity ([3H]triolein hydrolysis) and p-glycoprotein (rhodamine 123 fluorescence) activity, were not affected by FM-VP4.
Conclusions: In conclusion, FM-VP4 rapidly inhibits cholesterol accumulation within Caco-2 cell monolayers in a mode independent of pancreatic lipase activity, p-glycoprotein activity or cholesterol incorporation in micelles.