Thompson H J, Ronan A M, Ritacco K A, Tagliaferro A R, Meeker L D
Department of Animal and Nutritional Sciences, University of New Hampshire, Durham 03824.
Cancer Res. 1988 May 15;48(10):2720-3.
Although data reported in several epidemiological investigations indicate that reduced consumption of dietary fat and increased levels of physical activity are associated with reduced risk for breast cancer, the results of some studies do not support these observations. Underlying this situation is the unanswered question about whether degree of body fatness, which is affected by dietary composition, total caloric intake, and energy expenditure, is the critical determinant affecting breast cancer risk. The objective of this work was to establish whether increasing energy expenditure by exercise would reduce the occurrence of mammary carcinomas induced by 7,12-dimethylbenz[a]anthracene (DMBA) in animals consuming a high fat diet to the level of occurrence observed in sedentary animals consuming a low fat diet. Female Sprague-Dawley rats were obtained at 21 days of age and maintained on a 5% (w/w) corn oil diet (AIN-76A) until they were 64 days of age. At 50 days of age, rats received either 5 mg DMBA or the solvent in which the carcinogen was dissolved. Fourteen days after DMBA intubation they were randomized into one of three groups: 5% fat (w/w), sedentary; 24.6% fat (w/w), sedentary; or 24.6% fat (w/w), exercised. Animals were exercised on a motor-driven treadmill at a belt speed of 20 m/min and a 1-degree incline for 15 min/day, 5 days/week for 18 weeks. Feeding a high fat versus a low fat diet increased the number of breast cancers induced and the rate at which they appeared in agreement with previous investigations. However, rather than retarding the development of tumors as was hypothesized, moderate treadmill exercise increased the incidence and number of cancers induced and shortened cancer latency in comparison to animals that received either the high fat or low fat diet and were sedentary. Body composition was not altered by the exercise regime imposed, although these animals weighed more than either sedentary group. These data document a heretofore unreported effect of a moderate level of aerobic work on breast cancer induction.
尽管多项流行病学调查所报告的数据表明，膳食脂肪摄入量的减少以及身体活动水平的提高与乳腺癌风险的降低相关，但一些研究结果并不支持这些观察结果。造成这种情况的根本原因是一个尚未得到解答的问题，即受饮食组成、总热量摄入和能量消耗影响的身体肥胖程度是否是影响乳腺癌风险的关键决定因素。这项研究的目的是确定通过运动增加能量消耗是否会将食用高脂肪饮食的动物中由7,12 - 二甲基苯并[a]蒽（DMBA）诱发的乳腺癌发生率降低到食用低脂肪饮食的久坐不动动物中所观察到的发生率水平。雌性斯普拉格 - 道利大鼠在21日龄时获得，并维持在5%（w/w）玉米油饮食（AIN - 76A）中，直至64日龄。在50日龄时，大鼠接受5毫克DMBA或致癌物溶解于其中的溶剂。DMBA插管14天后，它们被随机分为三组之一：5%脂肪（w/w），久坐不动；24.6%脂肪（w/w），久坐不动；或24.6%脂肪（w/w），运动组。动物在电动跑步机上以20米/分钟的皮带速度和1度的坡度运动，每天15分钟，每周5天，持续18周。与先前的研究一致，喂食高脂肪饮食与低脂肪饮食相比，增加了诱发的乳腺癌数量及其出现的速率。然而，与接受高脂肪或低脂肪饮食且久坐不动的动物相比，适度的跑步机运动并没有如假设的那样延缓肿瘤的发展，反而增加了诱发癌症的发生率和数量，并缩短了癌症潜伏期。尽管这些动物比任何一个久坐组的动物体重都更重，但运动方案并未改变身体组成。这些数据记录了中等强度有氧运动对乳腺癌诱发的一种迄今未报道的影响。
