Those Rastafarians with dreadlocks who never wash their hair may be on to something. Two compounds found in some shampoos, diethanolamine (DEA) and triethanolamine (TEA), may seep through the skin, into the brain, and block the ability of neurons to take up choline. Steven H. Zeisel, M.D., Ph.D and colleagues at University of North Carolina at Chapel Hill believe the reduction in choline uptake may reduce neural cell replication.
The research in animals centers around diethanolamine (DEA), a chemical used in shampoos, lotions, creams and other cosmetics. DEA is used widely because it provides a rich lather in shampoos and keeps a favorable consistency in lotions and creams, but there's also some research that shows it may rob the brain of its ability to make memory cells."Depending on the treatment, some mice are stupid, some are not," said researcher Dr. Steven Zeisel.
In the modern scientific telling of the ancient story Samson was shampooed by Delilah and he became so dumb she was able to manipulate him to do her bidding without cutting off his hair.
Dr. Zeisel says if the dea-hypothesis holds true, the memory impact would probably be minimal in adults. But it could have a bigger effect on the developing brain, during pregnancy and the first few years of life.
Dr. Zeisel is investigating whether choline supplementation can counteract the effect of DEA and TEA.
The US National Institutes of Health National Library of Medicine happens to have an online database of household products and their ingredients. Check out the lists of Shampoo/Conditioner and Shampoo products and what each contains. It doesn't appear that all products are listed. Also, the ingredient lists look like what you find by reading the side of the bottle anyway. Still, if you want to check a number of different products while still remembering the names of these chemicals it is pretty quick to do.
Other recent work by Zeisel's lab showed how choline upregulates a gene to cause neurons to divide.
Now, working with nerve tissue derived from a human cancer known as a neuroblastoma, the UNC researchers have discovered why more choline causes stem cells -- the parents of brain cells -- to reproduce more than they would if insufficient choline were available.
A report on the findings will appear in the April issue of the Journal of Neurochemistry. Authors are doctoral student Mihai D. Niculescu and Dr. Steven H. Zeisel, professor and chair of nutrition at the UNC schools of public health and medicine. Dr. Yutaka Yamamuro, a former postdoctoral fellow in Zeisel's laboratory now with Nihon University in Japan, was a key contributor.
"We found that if we provided them with less choline, those nerve cells divided less and multiplied less," Zeisel said. "We then went on to try to explain why by looking at genes known to regulate cell division."
Scientists focused on cyclin-dependent kinase inhibitor 3 genes, which keep cells from dividing until a biochemical message turns the genes off, he said. They found exactly what they expected.
"We showed that choline donates a piece of its molecule called a methyl group and that gets put on the DNA for those genes," Zeisel said. "When the gene is methylated, its expression is shut down."
But when the gene is under-methylated -- such as when there’s not enough choline in the diet -- then it’s turned on -- halting or slowing nerve cell division, he said.
"Nature has built a remarkable switch into these genes something like the switches we have on the walls at home and at work," Zeisel said. "In this very complicated study, we’ve discovered that the diet during pregnancy turns on or turns off division of stem cells that form the memory areas of the brain. Once you have changed formation of the memory areas, we can see it later in how the babies perform on memory testing once they are born. And the deficits can last a lifetime."
The next step, Zeisel said, will be confirm that the same things happen in living mouse fetuses when the mothers receive either high or low doses of choline.
Dr. Zeisel and other collaborators at UNC Chapel Hill and Tufts University have recently shown that insufficient folic acid even in later pregnancy results in lifelong reduction in cognitive ability in rats and mice.
CHAPEL HILL -- Folic acid is not just critical for brain development in embryos during the earliest stages of pregnancy, but it is a key to healthy brain growth and function late in pregnancy too, scientists at the University of North Carolina at Chapel Hill have discovered.Humans and other mammals lacking sufficient folic acid shortly before they are born can suffer lifelong brain impairment, the UNC animal studies indicate. Such research can never be done directly in growing human fetuses for obvious reasons, scientists say.
...The experiments involved feeding pregnant mice and rats high, normal or low amounts of folic acid in otherwise healthy diets, Zeisel said. Researchers then examined fetuses' brains and looked specifically at stem, or progenitor, cells that divide and give rise to various forebrain structures. "In the babies of folic acid-deficient mothers, the stem cells divided less than half as much as in the babies of mothers on normal diets so there were less than half the number of stem cells available to help populate the brain," he said. "In addition, the number of cells that were dying off was much greater -- twice as high as it should have been. "So not only were fewer cells being born, but many more were dying so that there were many fewer available to form important areas of brain. That means that those parts will be abnormal permanently, and that the folic acid story does not end soon after the beginning of pregnancy." Essentially, folic acid is somehow promoting stem cell growth and survival so that the brain can form good memory centers, Zeisel said. To the researchers' knowledge, no one had ever looked before at folic acid's effects on brain in late pregnancy. "In mice and rats, the brain centers we are talking about are almost identical to those in human beings, and -- along with what we already know our human folic acid needs -- that's why we think these animal findings are applicable to humans," Zeisel said. "We have every reason to believe that this is true for pregnant women. It likely is the best evidence we're going to get because these experiments can never be done in humans."
|Share |||Randall Parker, 2004 May 14 02:37 AM Brain Enhancement|