【作者】 王斌；

【导师】 糜漫天；

【作者基本信息】 第三军医大学 ， 营养与食品卫生学， 2008， 博士

【摘要】 乳腺癌是女性最常见的恶性肿瘤,严重威胁着女性的生命与健康。据美国癌症协会报道,2007年世界范围内共有130万浸润性乳腺癌新发病例,并有46.5万妇女死于乳腺癌。在西欧、北美等发达国家,乳腺癌发病率占女性恶性肿瘤首位。我国以往属乳腺癌的低发区,然而近年来随着居民生活方式和膳食结构的改变,我国乳腺癌的发病率正以每年平均3%的速度递增,成为妇女死亡率增长最快的恶性肿瘤,同时乳腺癌的发病年龄也呈逐渐年轻化的趋势,给患者和社会都带来了沉重的负担。为了降低乳腺癌的发病风险,国内、外学者对乳腺癌的发病机制以及早期诊断和预防的方法进行了广泛研究。近期研究发现,在乳腺癌高危人群中适时开展健康教育、化学预防或必要的手术预防能显著降低该人群乳腺癌的发生率,并改善其生活质量。因此,研究人员目前正致力于建立和完善乳腺癌的风险预测模型,通过对乳腺癌危险因素及生物标记物的确认和归纳,以有效从人群水平上筛选出乳腺癌的高危人群,从而为该人群激素替代治疗及常规检查方案的选择以及化学预防和手术预防的实施提供依据,以进一步巩固乳腺癌在人群水平上的预防效果。目前国际上已经确认的乳腺癌常规危险因素主要包括年龄、乳腺癌家族史、乳腺良性疾病史、膳食因素、生殖因素、社会因素、性激素水平等。然而,以上研究大都在高加索籍妇女中开展。我国开展的乳腺癌病因学研究相对较少,且由于研究人群、设计方案、样本量及统计方法等因素的差异,这些研究结果之间也缺乏统一性,因而也不清楚种族差异是否会影响这些常规危险因素与乳腺癌发生的相关性。此外,大量的动物实验及人群研究表明乳腺癌也是与膳食、营养因素,尤其是膳食脂肪关系最为密切的一类肿瘤。然而,进一步研究发现饱和脂肪酸(SFA)、单不饱和脂肪酸(MUFA)和多不饱和脂肪酸(PUFA)对乳腺癌的发生与发展存在不同的效应,且不同n-6 PUFA与n-3PUFA比例也会影响乳腺癌的发生。尽管全球范围内对膳食、营养与乳腺癌之间的关系进行了大量的研究,但是由于各地膳食模式的差异、膳食成分的多样性和膳食摄入量估计的复杂性等方面的问题,膳食、脂肪酸与乳腺癌之间的关系还不完全清楚。因此,探讨当前阶段我国妇女乳腺癌发生的危险因素,同时结合居民膳食结构变迁的实际,全面评价不同脂肪酸摄入对乳腺癌发生的影响,对正确认识膳食脂肪的营养价值,指导人们从膳食途径及行为途径上预防乳腺癌具有积极的意义,并为乳腺癌高危人群的筛选和临床防治提供理论依据。基于以上分析,本课题围绕“膳食脂肪酸与乳腺癌”的关系开展研究。通过开展乳腺癌组、乳腺良性疾病组和健康对照组的病例-对照研究,按统一标准共纳入乳腺癌新发病例458名,乳腺良性疾病新发病例392名,健康对照者789名,并按月经状态分成绝经前期和绝经后期,探讨了重庆地区妇女乳腺癌及乳腺良性疾病的危险因素,采用半定量食物频数表调查了各研究人群的食物消费以及脂肪酸摄入情况,并通过气相色谱法和电化学发光法检测了各人群血浆的脂肪酸组成谱及性激素水平,使用SPSS13.0软件比较各组脂肪酸及性激素水平的差异并分析不同暴露水平与乳腺癌发生风险的相关性。同时,本课题复制了MNU诱导的SD大鼠乳腺癌模型。通过膳食干预实验,观察了不同膳食脂肪酸(SFA、MUFA、n-6 PUFA、n-3 PUFA、1:1 n-6/n-3、5:1 n-6/n-3、10:1 n-6/n-3以及1:2:1 S/M/P)干预对化学致癌剂MNU诱导下大鼠乳腺癌发生的影响,同时利用气相色谱法检测各组大鼠血浆的脂肪酸组成,并分析了不同血浆脂肪酸水平与乳腺癌发生率差异的关系。主要研究结果:一、人群试验1.乳腺癌常规危险因素调查:重庆地区乳腺癌发病多为教育程度高、精神抑郁、初产年龄大且有乳腺良性疾病史以及乳腺癌家族史的妇女,而BMI值大、WHR值大、行经年数长及有生殖系统疾病史的绝经后妇女亦为乳腺癌发病的高危人群。此外,人际关系好、初潮年龄大以及累积哺乳时间长等因素能在绝经前、后不同程度地降低乳腺癌的发生风险。影响乳腺良性疾病发生的主要因素与此类似,主要是教育程度高、精神抑郁、累积哺乳时间长、行经年数长以及生殖系统疾病史和乳腺癌家族史等。2.血浆性激素水平与乳腺癌发生的相关性:乳腺癌患者三个时期内的雌二醇水平、黄体期的孕酮水平和绝经后期的睾酮水平均显著高于健康对照组(P<0.05)。Logistic回归分析提示血浆雌二醇水平上升是重庆地区妇女乳腺癌发生的重要危险因素,而睾酮水平上升也与绝经后妇女乳腺癌风险呈显著的正相关。黄体期和绝经后期妇女血浆的雌二醇水平上升亦能增加乳腺良性疾病的发生风险。3.膳食脂肪酸摄入与乳腺癌发生的相关性:各组间的SFA及n-3 PUFA的摄入水平在绝经前、后均无明显差异。但是,绝经前、后期乳腺癌组MUFA(主要为C18:1)摄入显著低于健康对照组,而膳食n-6 PUFA(主要为C18:2)摄入和n-6/n-3比值则显著高于健康对照组。进一步分析发现,MUFA、n-6 PUFA摄入量及膳食n-6/n-3比能显著影响乳腺癌的发生,而该类因素仅在绝经后期与乳腺良性疾病的发生呈显著相关。此外,调查结果还提示膳食中高水平的膳食纤维、Ca、Zn、Vit C和胡萝卜素摄入对乳腺癌及乳腺良性疾病的发生具有一定的保护作用。4.血浆脂肪酸组成与乳腺癌发生的相关性:绝经前、后妇女血浆高水平的C16:0和C18:1对乳腺癌的发生具有保护作用,而高水平的C18:2和n-6/n-3比值则能显著增加乳腺癌的发生风险。此外,绝经前期女性血浆高水平的C18:0也能显著增加乳腺癌的发病风险。血浆C18:1、C18:2水平及n-6/n-3比值亦能显著影响绝经后妇女乳腺良性疾病的发生风险。二、动物干预实验1.大鼠乳腺癌模型的复制:采用甲基亚硝基脲(MNU)以50mg/kg体重的剂量一次性给50日龄SD清洁级雌性大鼠腹腔注射,经病理学确认成功复制出大鼠乳腺癌模型;2.不同膳食脂肪酸构成比对MNU诱导大鼠乳腺癌发生的影响:1:1 n-6/n-3组大鼠的乳腺癌发生率、多发率等指标显著低于SFA组、MUFA组、n-6 PUFA组、5:1 n-6/n-3组、10:1 n-6/n-3组以及1:2:1 S/M/P组大鼠。实验期内未观察到n-3 PUFA组大鼠乳腺癌的发生。3.不同膳食脂肪酸干预对大鼠血浆脂肪酸组成的影响:膳食脂肪酸干预能显著影响大鼠体内血浆的脂肪酸组成,其变化趋势与膳食脂肪酸干预模式基本一致。与无乳腺癌诱发或低乳腺癌诱发的n-3 PUFA和1: 1 n-6/n-3组相比,高乳腺癌诱发组大鼠的血浆中C18: 0、C18: 2和n-6/n-3比值显著上升,而EPA和DHA含量显著降低。以上结果提示,不同膳食脂肪酸干预下大鼠血浆脂肪酸组成的改变以及n-6/n-3比例失衡可能是各组间大鼠乳腺癌发生差异性的主要原因之一。综上所述,本研究从病例-对照研究和动物实验两方面,探讨了重庆地区乳腺癌发病的相关危险因素,并重点分析了膳食脂肪酸摄入、体内脂肪酸组成与乳腺癌发生的相关性。研究发现教育程度高、精神抑郁、经常痛经、BMI值大、行经年数长、乳腺良性疾病史、恶性肿瘤家族史、生殖系统疾病史以及血浆雌二醇和睾酮水平上升是重庆地区妇女乳腺癌发病的重要危险因素,而保持良好的人际关系、初潮年龄大、月经规则以及累积哺乳时间长则有助于预防乳腺癌的发生。影响乳腺良性疾病发生的危险因素与此类似,但在暴露程度和效应关系上有所不同。膳食因素在绝经前、后的乳腺癌发生中均起着重要作用,膳食纤维、Ca、Zn、Vit C、胡萝卜素摄入能有效预防乳腺癌的发生。同时,膳食MUFA的摄入能降低乳腺癌的发生风险,而n-6 PUFA摄入水平及膳食n-6/n-3比升高能增加乳腺癌的风险。人群血浆脂肪酸组成分析和动物实验结果与之类似,进一步提示合理的膳食脂肪酸构成比对预防乳腺癌的发生起着重要的作用,且膳食来源和体内血浆水平的n-6/n-3比例失衡是乳腺癌及乳腺良性疾病的重要危险因素。以上结果提示女性应在日常生活中保持良好的精神心理状态并选择合理的生活方式及生育方式;同时积极调整饮食平衡,保证蔬菜和水果的摄入,并在合理控制总脂肪、总SFA的基础上,适当降低n-6 PUFA的摄入而保证n-3 PUFA、MUFA的摄入,以从行为途径和膳食途径上更好地预防乳腺癌的发生。更多还原

【Abstract】 Breast cancer, the most common malignancy tumor in women, severely threatens women’s health and life. According to the report of American Cancer Society, about 1.3 million new cases of invasive breast cancer were diagnosed among women worldwide in 2007, and 465,000 women were died from breast cancer. Breast cancer has the highest incidence rate than the other malignant tumors among women in the developed countries, such as in Western Europe and North America. Chinese women had traditionally lower incidence of breast cancer in the past. However, with the change of life style and dietary structure in the recent twenty years, breast cancer incidence has been increased by 3% per year in China, accompanied by the largely increased breast cancer mortalities. At the same time, the age of women who developed breast cancer became younger than before.Obviously, Breast cancer has imposed heavy burdens on the patients and society. To decrease the incidence rate of breast cancer, extensive studies has been conducted on the pathogenesis, early diagnose and preventive methods of breast cancer at home and abroad. According to the recent foundings, health education, chemoprevention and prophylactic surgery can significantly lower the incidence of breast cancer among those people who were at higher risk of breast cancer, and subsequently improve their quality of life. Therefore, researchers are engaged to establish and modify the risk predict mode for breast cancer, and to effectively screen the women at higher breast cancer risk from the general population through confirming and inducing the risk factors and biomarkers of breast cancer. These achievements are expected to provide rational advice on the hormone replacement therapy, routine breast examination, or essential chemoprevention and prophylactic surgery on these women.According to the comprehensive etiology studies of breast cancer, the established conventional risk factors of breast cancer are believed to include age, family history of breast cancer, history of breast benign diseases, dietary factors, reproductive factors, social factors and sex hormones. However, these data were mainly obtained from Caucasian women. In our country, there were much fewer studies on breast cancer etiology. Due to the differences of study population, research protocols, sample size and statistical method among these researches, the findings lack uniformity. Consequently, it is still unclear whether racial inheritance affects the relationship between conventional risk factors and breast cancer risk. In addition, large animal experiments and cohort studies indicated that breast cancer has a close relationship with dietary factors, especially in dietary fat. However, further studies suggested that saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) had different effects on the breast carcinogenesis. Furthermore, different ratio of n-3/n-6 PUFA had different effects on the breast carcinogenesis. Although large quantities of researches had been conducted on the relationship between dietary nutrition intake and breast cancer risk, the relations between dietary fatty acid and breast cancer is still unclear due to different dietary mode, diversity of food composition and complexity of food intake estimation. As a result, the study on the risk factors of breast cancer among Chinese women and evaluation on the relationship between dietary fatty acid intake levels and breast cancer risk has important significance on the dietary and behavior prevention of breast cancer.This project was designed to mainly evaluate the relationship between dietary fatty acid and women health. A case-control study was carried out to explore the conventional risk factors of breast cancer and breast benign disease. A total of 458 newly incident and histologically confirmed breast cancer, 392 breast benign disease patients and 789 healthy controls were enrolled into our study from February 2004 to December 2006. Subjects were divided into the premenopausal and postmenopausal group according to their menstrual status. All of the eligible participants were Chongqing female residents and consent to participate in our study. Semi-quantitative food frequency questionnaire table was used to investigate the dietary pattern and fatty acid intake in the recent year. Gas chromatography was used to determine the plasma fatty acid composition, and the electrochemiluminescene immunoassay (ECLIA) technique was used to determine plasma sex hormone levels. Software SPSS 13.0 was applied to analyze the difference of fatty acid and sex hormone levels among different groups, and to evaluate the associations of breast cancer risk with plasma fatty acid compostion and sex steroid hormone levels. At the same time, animal experiment was conducted to study the intervention effect of the different fatty acid composition dietary (SFA、MUFA、n-6 PUFA、n-3 PUFA、1:1 n-6/n-3、5:1 n-6/n-3、10:1 n-6/n-3 and 1:2:1 S/M/P) on the incidence of the MNU induced breast cancer. We also determined the plasma fatty acid composition using gas chromatography and explored the underlying mechanism of different fatty acid compositions on the mammary carcinogenesis.Main results1. Population study1.1 Study on the conventional risk factors of breast cancer: Our study suggested that higher education extent, mental depression, older at first live birth, with breast benign disease history and with family history of breast cancer were the risk factors of breast cancer among both pre- and post-menopausal women. Besides, higher BMI value, higher WHR value, longer duration of menstruation and with history of reproductive disease could also significantly increased the breast camcer risk among postmenopausal women. On the contray, better human relationship, older at menarche, longer duration of breastfeeding could effectively decrease the risk of breast cancer. Similar to breast cancer, factors affecting benign breast disease include higher education degree, spirit hurt, longer cumulative duration of lactation, longer duration of menstruation, history of reproductive disease and family history of breast cancer.1.2 Plasma sex hormone levels and risk of breast cancer: Study period was divided into follicle phase, luteal phase and postmenopausal period here. We observed that levels of estrodiol in three periods, progesterone in the luteal phase, testosterone in the postmenopausal women were significantly higher than the respective healthy controls (P< 0.05). Furthermore, we observed significantly positive associations with the risk of breast cancer for estrodiol in all periods, progesterone in the luteal phase and testosterone in the postmenopausal period. Higher level of estrodiol in the luteal phase and in the postmenopausal period could also increase the incidence risk of breast benign disease.1.3 Dietary fatty acid intake and its relevance to the breast cancer: There was no difference in SFA and n-3 PUFA intake among the three groups both in pre- and post-menopausal women. However, the intake of MUFA (mainly C18:1) in the breast cancer group were significantly lower than the healthy controls while n-6 PUFA (mainly C18:2) intake and ratio of n-6/n-3 were significantly higher than controls. Further analysis indicated that MUFA, n-6 PUFA intake and ratio of n-6/n-3 could significantly influence the incidence of breast cancer. While the MUFA, n-6 PUFA intake and ratio of n-6/n-3 had significant correlation with breast benign disease only in the postmenopausal women. In addition, We observed the corresponding protective effects of dietary fiber, Ca, Zn, Vit C and carotene on the incidence of breast cancer and breast benign disease.1.4 Plasma fatty acid composition and its association with breast cancer risk: We observed high plasma levels of C16:0 and C18:1 were protective factors, while C18:2 and the ratio of n-6/n-3 were the risk factors of breast cancer both in pre- and post-menopausal women. We also observed that high plasma level of C18:0 could significantly increase the incidence risk of breast cancer in premenopausal women. Plasma levels of C18:1 and C18:2 and the ratio of n-6/n-3 could significantly influence the incidence risk of breast benign disease in post-menopause women.2. Animal intervention experiment2.1 SD rat mammary carcinogenesis model replication: The SD female rats (50 days old) of SPF grade were given MNU 50mg/kg once through intraperitoneal injection. The replication of SD rat mammary carcinogenesis model was confirmed by histopathology observation.2.2 The effects of different fatty acid composition intervention on the incidence of MNU induced mammary tumors: The incidence rate and multiple sites incidence rate of mammary tumors were significantly lower in rats of 1:1 n-6/n-3 group than those in groups of SFA, MUFA, n-6 PUFA, 5:1 n-6/n-3, 10:1 n-6/n-3 and 1:2:1 S/M/P. We did not observed the breast carcinogenesis in rats of n-3 PUFA group.2.3 The effects of different fatty acid composition intervention on the plasma fatty acid composition: The intervention of different dietary fatty acid could significantly influence the plasma fatty acid composition in rats, and the compositions were changed according to the corresponding mode of dietary fatty acid. Compared with n-3 PUFA group and 1:1 n-6/n-3 PUFA group which had no breast carcinogenesis or low breast tumor incidence, the plasma level of C18:0, C18:2 and ratio of n-6/n-3 increased significantly while the plasma level of EPA and DHA reduced significantly in the other groups with high mammary tumor incidence. The above results suggest that the changes of plasma fatty acid compositions might be the important factors to affect the incidence of mammary tumor.In summary, through the above population study and animal experiment, our project investigated the risk factors of breast cancer in Chongqing, evaluated the associations of dietary fatty acid intake, plasma fatty acid composition and plasma sex hormone levels with breast cancer risk. We observed that higher education extent, mental depression, higher BMI values, longer duration of menstruation, history of breast benign disease, family history of breast cancer, history of reproductive disease, higher levels of estradiol and testosterone were the important risk factors of breast cancer in Chongqing women. Besides, good human relationship, older at menarche, and longer duration of breastfeeding were the protective factors of breast cancer. The risk factors influencing the breast benign disease were similar with those influencing the breast cancer. Dietary factors are also closely related with breast cancer risk both in pre- and post-menopause women. Dietary fiber, Ca, Zn, Vit C, carotene and MUFA intake might effectively prevent the breast cancer, while dietary n-6 PUFA intake and increased ration of n-6/n-3 might increase the risk of breast cancer. The above factors could influence breast benign disease risk in postmenopausal women as well. Combined with the results of dietary fatty acid intake, plasma fatty acid composition and animal experiment, we found that MUFA and n-6 PUFA levels are closely related with breast cancer risk. Besides, the unbalanced ratio of n-6/n-3 in dietary intake and plasma fatty acid composition might also be the important risk factor of breast cancer and breast benign disease. In consideration of the residents’current dietary structure and life style, the above results suggested that women should keep good mental state and reasonable life style (including possible selection of menstruation and reproductive style). At the same time, basing on the rational dietary structure, they should control the intake level of total fat and total SFA, reduce the intake of n-6 PUFA and assure the intake of n-3 PUFA, MUFA and dietary fiber, so as to eventually prevent breast cancer from behavior and dietary pathways.更多还原