Shivapurkar N, Tang Z, Frost A, Alabaster O
Institute for Disease Prevention, George Washington University, Washington, D.C. 20037, USA.
Cancer Lett. 1995 May 4;91(1):125-32. doi: 10.1016/0304-3835(95)03729-g.
In this study we evaluated the effect of dietary administration of a high-fat, low-fiber diet (HRD) supplemented with Vitamin E, beta-carotene or folic acid and wheat bran on the growth of pre-existing aberrant crypt foci (ACF) that had been induced in Fischer-344 rats exposed to azoxymethane (AOM) and a HRD for 10 weeks. The rats (25 rats/dietary group) were fed a HRD for 2 weeks and were then given 2 subcutaneous injections of AOM (15 mg/kg body weight) while the rats continued on the HRD. After 6 weeks, rats were either maintained on the HRD (control) or crossed over to a HRD containing non-toxic levels of either Vitamin E, beta-carotene, folic acid or wheat bran. At 10, 14 and 18 weeks after the initiation of the experiment, 5 rats from each group were killed and the number of aberrant crypt foci (ACF) with different multiplicities were compared between groups. The dietary intervention was continued for 30 weeks to determine whether the inhibitory effect on the growth of ACF influenced the subsequent development of colonic tumors. The results revealed that vitamin E and beta-carotene caused a significant decrease in the number of ACF of different multiplicities when compared to the effect of the HRD alone. The decrease in the number of ACF due to folic acid and wheat bran appeared to be much smaller and in most cases was not significant. However, there was also a significant decrease in the incidence of colonic tumors and tumor multiplicity in both the vitamin E and beta-carotene groups that was not seen in the control group. The reports clearly demonstrates the ability of vitamin E and beta-carotene to inhibit the growth of colonic ACF, even in the presence of the strong promoting effect of high levels of dietary fat, using a post-initiation experimental design.
在本研究中，我们评估了在高脂、低纤维饮食（HRD）中添加维生素E、β-胡萝卜素、叶酸或麦麸对已在暴露于偶氮甲烷（AOM）和HRD 10周的Fischer-344大鼠中诱导产生的预先存在的异常隐窝灶（ACF）生长的影响。大鼠（每组25只）先喂食HRD 2周，然后皮下注射2次AOM（15 mg/kg体重），同时大鼠继续食用HRD。6周后，大鼠要么继续维持HRD饮食（对照组），要么转而食用含有无毒水平的维生素E、β-胡萝卜素、叶酸或麦麸的HRD。在实验开始后的第10、14和18周，每组处死5只大鼠，比较不同多倍体的异常隐窝灶（ACF）数量。饮食干预持续30周，以确定对ACF生长的抑制作用是否会影响随后结肠肿瘤的发生。结果显示，与单独的HRD相比，维生素E和β-胡萝卜素可使不同多倍体的ACF数量显著减少。叶酸和麦麸导致的ACF数量减少似乎要小得多，且在大多数情况下不显著。然而，维生素E组和β-胡萝卜素组的结肠肿瘤发生率和肿瘤多倍体也显著降低，而对照组未出现这种情况。该报告清楚地证明了维生素E和β-胡萝卜素抑制结肠ACF生长的能力，即使在高水平膳食脂肪的强烈促进作用存在的情况下，采用的是启动后实验设计。
