ScienceDaily (Aug. 1, 2009) — Researchers at Georgia State University have found that diets high in fructose — a type of sugar found in most processed foods and beverages — impaired the spatial memory of adult rats.

Amy Ross, a graduate student in the lab of Marise Parent, associate professor at Georgia State's Neuroscience Institute and Department of Psychology, fed a group of Sprague-Dawley rats a diet where fructose represented 60 percent of calories ingested during the day.

She placed the rats in a pool of water to test their ability to learn to find a submerged platform, which allowed them to get out of the water. She then returned them to the pool two days later with no platform present to see if the rats could remember to swim to the platform's location.

"What we discovered is that the fructose diet doesn't affect their ability to learn," Parent said. "But they can't seem to remember as well where the platform was when you take it away. They swam more randomly than rats fed a control diet."

Fructose, unlike another sugar, glucose, is processed almost solely by the liver, and produces an excessive amount of triglycerides — fat which get into the bloodstream. Triglycerides can interfere with insulin signaling in the brain, which plays a major role in brain cell survival and plasticity, or the ability for the brain to change based on new experiences.

Results were similar in adolescent rats, but it is unclear whether the effects of high fructose consumption are permanent, she said.

Parent's lab works with Timothy Bartness, Regents' Professor of Biology, and John Mielke of the University of Waterloo in Waterloo, Ontario, Canada to examine how diet influences brain function.

Although humans do not eat fructose in levels as high as rats in the experiments, the consumption of foods sweetened with fructose — which includes both common table sugar, fruit juice concentrates, as well as the much-maligned high fructose corn syrup — has been increasing steadily. High intake of fructose is associated with numerous health problems, including insulin insensitivity, type II diabetes, obesity and cardiovascular disease.

"The bottom line is that we were meant to have an apple a day as our source of fructose," Parent said. "And now, we have fructose in almost everything." Moderation is key, as well as exercise, she said.

Exercise is a next step in ongoing research, and Parent's team will investigate whether exercise might mitigate the memory effects of high fructose intake. Her lab is also researching whether the intake of fish oil can prevent the increase of triglycerides and memory deficits. Results from that research will be presented by her graduate student Emily Bruggeman at the 2009 Society for Neuroscience meeting in Chicago this fall.

科学日报（20090716）乔治亚州大学的研究者们发现，饮食中果糖（存在于大多数加工食品或饮料中的一种糖）含量过高有损于成年大鼠的空间记忆能力。
Georgia 州神经研究所和心理学系的助理教授兼Marise Parent实验室的学者――Amy Ross，选用SD大鼠做实验，大鼠每天摄入能量的60%来自果糖。
她把实验大鼠放入特制的水池中，来检测大鼠空间识别能力。首先，在此水池中预先放入一被水淹没的平台，当大鼠爬上此平台后，大鼠就露出水平。二天后，她把实验大鼠再次放入平台已撤离的上述水池中，看看这些大鼠能否游到以前放置平台的位置。
“我们发现，果糖饮食不会影响大鼠的学习能力。”Parent实验室（发言人）说，“但当我们撤离平台后，这些大鼠好象忘了平台放置的位置。与对照组大鼠相比，它们在水池中游地更无目的性”
果糖与蔗糖（另一种糖）不一样，它只在肝脏降解，并大量产生一种能进入血流的脂类物质――甘油三酯。该脂类物质能干扰脑胰岛素的信号传导。脑胰岛素信号传导通路在脑细胞的存活与可塑性方面发挥着重要作用。或在脑接受新事物方面发挥重要作用。
她说，在成年大鼠的实验中，结果是相似的。但是，果糖的上述效应是否持久目前还不清楚。
研究饮食对脑功能影响的实验室除了Parent实验外，还有与之合作的生物学教授Regent的Timothy Bartness实验室、加拿大安大略省Waterloo大学的John Mielke实验室。
尽管人不会饮用象实验中大鼠摄入的（那么高水平的）果糖。但在人们摄入的食物当中，用果糖加甜食物（如both common table sugar,果汁浓缩液及对人有害的高果糖玉米糖浆）所占比例正逐渐增多。高摄入果糖可引起许多疾病，如胰岛素抵抗，II型糖尿病，肥胖及心血管疾病。
Parent说，“我们推荐每天补充果糖的量以一个苹果为限。然而现在几乎每种食物都含有果糖。减少果糖的摄入与加强（自身体育）锻炼是最有效的办法。”

体育锻炼（对降低果糖对机体的影响）是进一步研究的课题。Parent研究小组将研究体育锻炼是否能减轻高摄入果糖对记忆的影响。该实验室也着手研究，鱼油的摄入能否阻止（血中）甘油三酯水平的升高及对记忆力的损害。该实验结果将于2009年秋季的神经科学年会上由其学生Emily Bruggeman来陈述。

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