上海交通大学医学院附属瑞金医院宁光教授领导的研究团队近期通过大样本人群，对中国成人尿增塑剂双酚A（bisphenol A, 双酚A）水平与2型糖尿病(T2DM)的相关性进行了研究，结果发现人体双酚A暴露达到一定程度时，可能会增加2型糖尿病患病风险，但尚不能证实双酚A与2型糖尿病之间存在明确的相关性。相关结果于 2011年9月20日刊登在美国《内科学年鉴》（Ann Intern Med September 20, 2011 vol. 155 no. 6 368-374）。

　　2型糖尿病的发病机制非常复杂，遗传因素与环境因素是影响2型糖尿病发生和发展的两个主要因素。动物试验显示，机体长期接触双酚A可能通过刺激肝脏、肌肉胰岛素抵抗以及改变胰岛β细胞功能，引发糖代谢异常，进而导致2型糖尿病的发生。一定剂量的双酚A进入体内后具有模拟雌激素的作用，可影响性发育、神经系统发育和糖脂代谢，尤其是器官发育未完全的婴幼儿。既往人体相关研究非常少，美国国家健康与营养调查（NHANES）2003-2004年的数据显示，人体尿中双酚A水平与2型糖尿病的患病风险显著相关。但由于该研究存在的局限性（如2型糖尿病未经临床诊断，仅根据被调查者提供的病史信息等），医学科学界对该研究结果存在一定的争论。

　　宁光教授领导的研究团队在3423名40岁以上的社区人群中，通过口服葡萄糖耐量试验结合病史对2型糖尿病患者进行了明确诊断，并测定了所有研究对象的尿双酚A水平与血糖水平。研究显示，在受试人群中87.7%可检测到尿液中含有双酚A，平均水平为0.81ng/mL。研究者根据尿双酚A水平将受试者分为4组后发现，较高水平的尿双酚A（>1.43 ng/mL）显著增加2型糖尿病的患病风险，但是，较低水平的尿双酚A(<1.43 ng /mL）与2型糖尿病患病风险之间未发现明确的相关性。。据此，研究者推测，当人体双酚A暴露达到一定程度时，可能会增加2型糖尿病患病风险。但是未发现短期少量的接触对2型糖尿病的患病风险产生显著影响。《内科学年鉴》在配发的评论中指出，“鉴于双酚A的暴露是世界性的，我们期待企业与政府联合起来推进双酚A对健康的影响的研究。”

　　研究者的观点

　　我们应该客观理性地看待双酚A给日常生活带来的利与弊。其实，公众根本无需为双酚A而恐慌，在婴儿奶瓶中禁用双酚A是应该的，同时在反复加热塑料容器如微波炉用容器中最好没有双酚A，而一般使用的容器中少量的双酚A，因为能进入人体的量很低，不会对人体造成影响。研究结果也启示我们，对待与人民生活密切相关的日用品中的许许多多的化学添加剂，应采取审慎、科学、公正的态度，即不能忽视对人体可能得损害，但也不能随意夸大危害，不仅可能引起不必要的担忧，而且还有可能用更昂贵的替代品，从而增加社会成本。

　　当然，研究显示的高水平尿双酚A对人类健康尤其是血糖代谢紊乱的影响应该引起适度的关注。“眼下亟需形成稳定支持的科学团队，并有长期固定的监测基地，建立一套长效机制，进行长期的随访与深入研究，从而客观公正科学审慎地评价各类环境内分泌干扰物对人体健康可能的危害，不仅形成中国自己的相关数据，而且为采取措施提供依据。”研究团队的负责人、上海市高校内分泌代谢病E研究院首席研究员、上海交通大学医学院附属瑞金医院宁光教授指出。

　　背景资料链接

　　2008年10月18日，加拿大宣布禁止在婴儿奶瓶制作过程中使用双酚A。2009年3月，美联邦提案禁止在“可重复使用的食品容器”中使用双酚A。 2011年3月1日起，欧盟禁止使用含双酚A的塑料婴儿奶瓶。2011年5月30日，我国卫生部公告表示与婴幼儿食品接触的包装材料中禁用双酚A。

　　双酚A是在塑料制造中广泛使用的一种碳氢化合物，连接其他分子形成高分子树脂。作为增塑剂，双酚A是用来制造塑料，包括饮料包装、奶瓶、水瓶、微波炉专用产品、盛装食物和饮料的罐子、牙具、磁盘、眼镜以及医疗器材等的重要物质。通常情况下，双酚A仅少量释放，人们在日常生活中通过饮食、呼吸、皮肤接触等途径少量吸收双酚A。但是加热或与酸碱化合物接触会加速塑料中双酚A 的释放，人们也常会因为使用塑料产品盛装热饮、微波加热等过程增加双酚A的吸收。据统计，美国人群中约有93%到95%可在尿液中检测出双酚A。

　　链接：路透社新闻稿

　　Study sees no clear link between BPA,diabetes

　　In a study of 3,400 Chinese adults age 40 and up, researchers found no clear-cut connection between people's urinary levels of bisphenol A -- better known as BPA -- and their odds of having diabetes.

　　The one-quarter with the highest BPA levels did have a higher risk of diabetes than the quarter with the lowest levels. But the researchers failed to find a "dose-response" relationship -- where the risk of diabetes would steadily climb as BPA exposure did.

　　And the researchers say that means they cannot conclude there is a BPA-diabetes connection.

　　But the findings, published in the Annals of Internal Medicine, are far from settling the issue of BPA's possible health effects. And researchers not involved in the study questioned the authors' conclusions.

　　BPA is a so-called endocrine disruptor, which means it may affect normal hormone activity in the body.

　　It's also ubiquitous. BPA has been used for decades to make hard plastic containers, and linings for metal food and drink cans. Research suggests that most people, including about 95 percent of Americans, have some amount of BPA in their blood.

　　Recent animal studies have hinted that the chemical could play a role in certain cancers, heart disease and abnormal brain development in children. Due to the controversy over BPA, the major manufacturers of infant bottles and feeding cups in the U.S. have stopped using the chemical.

　　But BPA's true effects in humans remain unknown. Two large studies have found a link between higher BPA levels and higher heart disease risk. And a 2008 study found that of Americans in a government health survey, those with higher BPA levels showed a higher diabetes risk.

　　None of that proves cause-and-effect, however.

　　And these latest findings "do not confirm" a BPA-diabetes connection, write the researchers, led by Dr. Guang Ning of Shanghai Jiao-Tong University School of Medicine.

　　Of the 3,423 men and women studied, 32 percent had type 2 diabetes. When the researchers separated all participants into four groups based on urinary BPA level, they found that the group with the highest levels was 37 percent more likely to have diabetes than the group with the lowest BPA concentrations.

　　That was with other factors -- like age, weight and kidney function -- taken into account.

　　On the other hand, Ning's team found, the study group with the second-highest BPA levels showed no increase in their diabetes risk, while the one with the second-lowest did.

　　So there was no "clear, monotonic relationship" between BPA and diabetes risk, Ning told Reuters Health in an email.

　　"The evidence was not sufficient enough to declare an association," Ning said.

　　But an editorial published with the study says the researchers took an "idiosyncratic" approach to their data, essentially dismissing the diabetes risk seen in the highest-BPA group.

　　"It would be great to see the data released to the wider scientific community," Tamara Galloway, a professor at the University of Exeter in the UK and one of the editorial writers, told Reuters Health in an email.

　　That's what was done with the U.S. data used in the 2008 study that did find a BPA-diabetes link, noted Galloway -- who was one of the researchers on that study.

　　Another limitation of the study, according to Galloway, is that participants' BPA levels were quite low. The typical level of the entire group was 0.8 nanograms per milliliter, whereas the typical level in the U.S. is closer to 2 nanograms per milliliter.

　　"The levels in this Chinese population were very low compared with the USA, Europe and Japan," Galloway said, "so the lesson for these more highly exposed populations remain ambiguous."

　　Ning's team agrees on the need for further studies. Another limit of the current one is that it looked at people at one time point, rather than following them over time to see whether higher BPA levels foretell a higher risk of developing diabetes later on.

　　The researchers are now following this same study group to answer that question.

　　Such studies are "crucially needed," Galloway said.

　　"This is particularly important for associations with cardiovascular disease," she added, "which have been reported now in two separate large-scale population studies."

　　It's biologically plausible that BPA could affect diabetes risk, according to Galloway.

　　Studies have suggested that the chemical may act like a hormone in the body, possibly interfering with normal metabolism. Type 2 diabetes arises when the body can no longer properly use insulin, a hormone that regulates blood sugar.

　　"There are, however, huge gaps in our understanding of the health effects of exposure to this chemical," Galloway said, "We need better data on how people are exposed, and how the compound is metabolized in the body."

　　For now, she said, people who are concerned about BPA exposure can try cutting down on canned foods and avoiding food containers made of polycarbonate plastics -- especially for reheating food, since high heat may transfer small amounts of BPA into food.

　　Polycarbonate plastics are usually marked with the recycling code "7," Galloway noted.

　　SOURCE: bit.ly/pDoDmlAnnals of Internal Medicine, online September 19, 2011.