Awad Atif B, Fink Carol S, Trautwein Elke A, Ntanios Fady Y
Department of Exercise and Nutrition Sciences, University at Buffalo, 14214, USA.
J Nutr Biochem. 2005 Nov;16(11):650-5. doi: 10.1016/j.jnutbio.2005.04.004.
Previous studies from our laboratory on tumor cells suggest that phytosterols stimulate ceramide production, which was associated with cell growth inhibition and stimulation of apoptosis. The objective of the present study was to examine the effect of phytosterols on ceramide metabolism in small intestinal cells that represent the first cells in contact with dietary phytosterols. Caco(2) cells, an accepted model for human intestinal epithelial cells, were used in this study. Ceramide and ceramide-containing lipids were examined by labeling the ceramide pool with (3)H-serine. Cells were supplemented with 16 microM of sterols (cholesterol, beta-sitosterol or campesterol) for 16 days postconfluence and continued to differentiate. Of the two phytosterols, beta-sitosterol, but not campesterol, induced more than double the serine labeling when compared with cholesterol. This increase was uniform in sphingomyelin (SM), ceramide and sphingosine labeling. Sterols had no effect on SM concentration in the cells. In addition, sterol had no effect on the activity of SM synthase or sphingomyelinases. There was an inhibition of ceramidases with campesterol supplementation. These data suggest that the observed increases in SM and sphingosine labeling were due to an increase in ceramide turnover. The increase in ceramide turnover with beta-sitosterol supplementation was not associated with growth inhibition but was with increases in ceramide glycosylation products such as cerebrosides and gangliosides. It was concluded that beta-sitosterol has no effect on differential Caco(2), a model of normal small intestinal cells. The increase in the glycosylated ceramide products may offer a means to protect the cells from the harmful effect of ceramide by excreting them with lipoproteins.
我们实验室之前对肿瘤细胞的研究表明，植物甾醇可刺激神经酰胺的产生，这与细胞生长抑制和细胞凋亡的诱导有关。本研究的目的是检测植物甾醇对小肠细胞中神经酰胺代谢的影响，小肠细胞是最先接触膳食植物甾醇的细胞。本研究使用了人肠上皮细胞公认的模型——Caco(2)细胞。通过用(3)H-丝氨酸标记神经酰胺池来检测神经酰胺和含神经酰胺的脂质。细胞在汇合后用16 microM的甾醇（胆固醇、β-谷甾醇或菜油甾醇）处理16天，并持续分化。在这两种植物甾醇中，与胆固醇相比，β-谷甾醇而非菜油甾醇诱导的丝氨酸标记增加了一倍多。这种增加在鞘磷脂（SM）、神经酰胺和鞘氨醇标记中是一致的。甾醇对细胞中SM的浓度没有影响。此外，甾醇对SM合酶或鞘磷脂酶的活性没有影响。补充菜油甾醇会抑制神经酰胺酶。这些数据表明，观察到的SM和鞘氨醇标记增加是由于神经酰胺周转率的增加。补充β-谷甾醇后神经酰胺周转率的增加与生长抑制无关，但与神经酰胺糖基化产物如脑苷脂和神经节苷脂的增加有关。得出的结论是，β-谷甾醇对正常小肠细胞模型Caco(2)没有差异影响。糖基化神经酰胺产物的增加可能提供了一种通过与脂蛋白一起排泄来保护细胞免受神经酰胺有害影响的方法。
