Tang Z C, Shivapurkar N, Frost A, Alabaster O
Institute for Disease Prevention, George Washington University Medical Center, Washington, DC 20037, USA.
Nutr Cancer. 1996;25(2):151-9. doi: 10.1080/01635589609514437.
Female Sprague-Dawley rats (n = 270) were randomly divided into nine subgroups (30 rats/group) and fed diets with fat contents ranging from 5% to 45% of total energy, in which fat was isocalorically substituted for carbohydrates. At Week 3, the rats were given a single injection of methylnitrosourea (MNU, 50 mg/kg body wt). At Weeks 4 and 5, rats were given an injection of azoxymethane (AOM, 15 mg/kg body wt sc). The rats were maintained on their respective experimental diets until they were sacrificed. Nine weeks after the injection of MNU, 10 rats from each group were killed and their mammary tissue was examined for tumors and their colons for aberrant crypt foci (ACF) formation. The results showed no significant increase in the number of colonic ACF or mammary tumors at 11 weeks among individual groups consuming 5-25% energy from fat or among groups consuming 30-45% energy from fat. Data analysis indicated that the effects of the two diets (5-25% energy from fat and 30-45% energy from fat) on ACF formation as well mammary tumor development were statistically different. Continuation of the diets for 32 weeks led to the development of colonic and mammary tumors. Analysis of the combined group tumor incidence data clearly showed that the colonic and mammary tumor incidence in groups fed 30-45% of energy from fat was significantly higher than that observed among groups fed 5-25% of energy from fat. Linear regression analysis of the colonic ACF at 11 weeks, colonic tumor incidence at 32 weeks, and mammary tumor incidence at 11 and 32 weeks showed good linear correlation, demonstrating the potential value of ACF and mammary tumors at 11 weeks for evaluating the carcinogenic risk associated with different diets. The main conclusion of the experiment is that the incidence of colon and mammary cancers increased rapidly when the dietary levels of fat were increased from 15% to 30% of calories and that there was no significant influence on the colon and mammary cancer risk beyond 30% of calories from fat.
将270只雌性斯普拉格 - 道利大鼠随机分为9个亚组（每组30只），喂养脂肪含量占总能量5%至45%的日粮，其中脂肪等量替代碳水化合物。在第3周，给大鼠单次注射甲基亚硝基脲（MNU，50毫克/千克体重）。在第4周和第5周，给大鼠注射氧化偶氮甲烷（AOM，15毫克/千克体重，皮下注射）。大鼠维持各自的实验日粮直至处死。注射MNU九周后，每组处死10只大鼠，检查其乳腺组织中的肿瘤以及结肠中的异常隐窝灶（ACF）形成情况。结果显示，摄入脂肪占能量5% - 25%的各个组以及摄入脂肪占能量30% - 45%的各个组在11周时结肠ACF数量或乳腺肿瘤数量均未显著增加。数据分析表明，两种日粮（脂肪占能量5% - 25%和脂肪占能量30% - 45%）对ACF形成以及乳腺肿瘤发展的影响在统计学上存在差异。持续喂养日粮32周导致结肠和乳腺肿瘤的发生。对合并组肿瘤发病率数据的分析清楚地表明，摄入脂肪占能量30% - 45%的组中结肠和乳腺肿瘤发病率显著高于摄入脂肪占能量5% - 25%的组。对11周时结肠ACF、32周时结肠肿瘤发病率以及11周和32周时乳腺肿瘤发病率进行线性回归分析显示出良好的线性相关性，表明11周时ACF和乳腺肿瘤对于评估不同日粮相关致癌风险具有潜在价值。该实验的主要结论是，当日粮中脂肪水平从热量的15%增加到30%时，结肠癌和乳腺癌的发病率迅速上升，而脂肪热量超过30%对结肠癌和乳腺癌风险没有显著影响。
