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David Ludwig, MD, PhD Move over, Atkins
First came low-fat diets, then came low-carb diets, now David Ludwig, MD, PhD, director of the Optimal Weight for Life (OWL) obesity program at CHB, is weighing in on the low-glycemic-index (low-GI) diet—one whose carbohydrates are low in sugar or release sugar slowly.
In a study published in The Lancet (August 28), Ludwig's team fed rats tightly controlled diets with identical nutrients, except for the type of starch. At follow-up, rats eating the high-GI starch had 71 percent more body fat than rats eating the low-GI starch. They also had higher blood glucose and insulin levels and more abnormalities in the cells that make insulin—all changes that occur in diabetes. In addition, their blood triglyceride levels, a risk factor for cardiovascular disease, were nearly tripled.
Ludwig hopes these findings, reported in The New York Times, Washington Post, and other media outlets, convince health groups to include the glycemic index in their dietary guidelines. "The Atkins diet tries to get rid of all carbohydrates," he says, "but you don't have to go to this extreme if you choose low-GI carbs like legumes, vegetables, most fruits and whole grains." Endocrinology research fellow Dorota Pawlak, PhD, was first author on the study.
Children's is now recruiting people ages 18 to 35 for a human study of the low-GI diet. Hospital employees are eligible; for information contact Erica Garcia-Lago, ext. 5-2500.
Viral structure provides lead for diarrhea vaccine
Almost all infants and toddlers contract rotavirus, which causes diarrhea and vomiting, sometimes severe.
Philip Dormitzer, MD, PhD Philip Dormitzer, MD, PhD, a physician and structural virologist in Children's Laboratory of Molecular Medicine, has constructed high-resolution images that reveal the molecular gymnastics rotavirus uses to get into cells. Based on these discoveries, which were published in the August 26 issue of Nature, Dormitzer is working on a vaccine that he hopes will stop the virus in its tracks.
Structurally, rotavirus is a large, 20-sided, soccer ball-shaped particle. Sixty "spikes" project from its surface, each made up of a protein called VP4. Dormitzer's team found that VP4 undergoes two shape changes once it arrives in the intestines—the spikes become rigid and then fold back, enabling rotavirus to break through the surface of the cell it's infecting. Additionally, the moving components of VP4 trigger the immune system, making it possible to fashion them into a vaccine without using the whole rotavirus. Unlike whole-virus vaccines, the VP4 components appear to be stable at room temperature and relatively cheap to produce, a boon for developing countries, where rotavirus can be fatal.
Stephen Harrison, PhD, chief of the Laboratory of Molecular Medicine and a Howard Hughes Medical Institute investigator, was senior author on the study.
Beaker bytes is a monthly column in Children's News. If you have received a grant, launched a new study or have a paper accepted for publication, contact Nancy Fliesler at ext. 5-2426 or via email at nancy.fliesler@childrens.harvard.edu.
