EFFECTS OF DIETARY POLYUNSATURATED FAT ON HELICOBACTER PYLORI

幽门螺杆菌(Hp)感染是人类慢性胃炎最常见的病因，与消化性溃疡的发生发展密切相关。最近，流行病学研究表明，幽门螺杆菌是胃癌的独立危险因素，感染幽门螺杆菌的人患这种疾病的风险是未感染的人的3-6倍。从幽门螺杆菌相关性浅表性胃炎发展到萎缩性胃炎伴肠上皮化生被认为是胃癌发生的先兆。研究人员推测，幽门螺杆菌相关性慢性胃炎的自然发展是萎缩性胃炎，而萎缩性胃炎可能会因饮食因素而延长或缩短。富含水果和蔬菜、低淀粉和低盐的饮食与降低患胃癌的风险有关。这些饮食中抗氧化剂的存在被认为是降低癌症风险的因素。这些饮食中多不饱和脂肪的含量也很高，与饱和脂肪相反，已被证明能抑制细菌生长。最近的研究证实，多不饱和HAT在体外可以抑制幽门螺杆菌(被世界卫生组织命名为I类致癌物质，估计患胃癌的归因风险为50-60%)的生长。因此，抑制细菌生长的药物，即多不饱和脂肪，可能会降低由于这种致癌物质而导致的癌症风险。该项目的研究人员假设，由于多不饱和脂肪的细菌静态特性，富含水果和蔬菜的饮食可以保护胃癌。由于维生素E等抗氧化剂存在于富含多不饱和脂肪的油脂中，它们认为它们主要是作为摄取这些脂肪的标志，而不是预防胃癌的主要制剂。这项拨款建议在一项横断面研究中记录多不饱和脂肪摄入量和胃细菌负荷之间的间接相关性。体外研究将阐明多不饱和脂肪不仅会抑制生长，还会抑制这种细菌与人胃上皮细胞黏附所产生的细胞毒性。证实这一假设对世界上胃癌高发地区非常重要，因为这些地区幽门螺杆菌的发病率很高，而且成功的抗生素治疗后，幽门螺杆菌再感染率很高。了解饮食中富含多不饱和脂肪将降低患胃癌的风险，很可能是预防这种疾病的一种经济有效的方法，因为有疫苗可用，而且抗生素疗法在某些国家并不实用。

Helicobacter pylori (H. pylori) infection is the most common cause of chronic gastritis in man, and it has been implicated as an etiological factor in the development of peptic ulcer disease. More recently, epidemiological studies have demonstrated that H. pylori is an independent risk factor for gastric cancer and that people infected with H. pylori have a 3-6 fold higher risk of developing this condition than non-infected persons. Progression from H. pylori-related superficial gastritis to atrophic gastritis with intestinal metaplasia is felt to be a precursor to gastric cancer development. Investigators have postulated that the natural progression of H. pylori-associated chronic gastritis is to atrophic gastritis, which may be prolonged or shortened by dietary factors. Diets rich in fruits and vegetables and low in starch and salt are associated with a decreased risk of gastric cancer. The presence of antioxidants in these diets has been postulated to be the factors responsible for the decrease in cancer risk. These diets are also high in polyunsaturated fat which, as opposed to saturated ft, has been shown to inhibit bacterial growth. Recent studies have confirmed that polyunsatuated hat will inhibit H. pylori (named as a Class I carcinogen with an estimated attributable risk of 50-60% for gastric cancer by the World Health Organization) growth in vitro. Therefore, agents which inhibit bacterial growth, i.e., polyunsaturated fats are likely to decrease the risk of cancer due to this carcinogen. Investigators for this project postulate that diets high in fruits and vegetables protect gastric cancer because of the bacterial static properties of polyunsaturated fats. Since antioxidants such as vitamin E are present in oils rich in polyunsaturated fat, they feel that they serve mainly as a marker for ingestion of these fats, and are not the primary agents protecting against gastric cancer. This grant proposes to document in a cross-sectional study, the indirect correlation between polyunsaturated fat ingestion and gastric bacterial load. In vitro studies will be performed to elucidate the extent to which polynsaturated fat will not only inhibit growth, but also inhibit cytotoxicity induced by adherence of this bacterium to human gastric epithelial cells. Confirming this hypothesis would be very important to areas of the world which have a high incidence of gastric cancer, since these areas have both a high incidence of H. pylori and a high rate of re-infection with this organism after successful antibiotic treatment. Knowledge that dietary intake rich in polyunsaturated fat will reduce gastric cancer risk is likely to be a cost-effective way of preventing this disease, since there is a vaccine available and antibiotic therapy is not practical in certain countries.