Newfound Stomach Hormone
Could Suppress Hunger
Scientists have discovered a new hormone produced by the stomach and intestines that appears to play a crucial role in regulating appetite, possibly offering a new way to help people lose weight.
Aaron Hsueh of Stanford University and his colleagues identified the hormone, dubbed obestatin, while scouring genetic material across species. They were surprised to discover that a genetic sequence that carries instructions for the production of the recently discovered hormone ghrelin, which the stomach sends to the brain to stimulate appetite, also produced a previously unidentified chemical messenger that seems to have the opposite effect.
Suspecting the hormone also played a role in regulating appetite, the researchers synthesized the substance in the laboratory and injected it into normal rats, which promptly cut their food intake in half and dropped about 20 percent of their weight in just eight days, according to a report in the Nov. 11 issue of the journal Science.
The researchers plan next to see if giving the substance to obese animals makes them, too, lose weight. They also plan to test humans to see if levels of the hormone are related to appetite and weight.
If so, the substance itself or other agents that mimic its action could offer effective new drugs to help people lose weight, the researchers and others said.
"This is certainly a major discovery. Obese patients shouldn't get their hopes up yet that there is a new drug, but it's certainly one step in the right direction," said Matthias Tschoep of the University of Cincinnati, who wrote a commentary accompanying the report.
Tschoep and others cautioned, however, that previously identified naturally occurring hormones that regulate appetite and weight, most notably the hormone leptin, have so far failed to yield effective weight-loss drugs.
-- Rob Stein
Foliage Migration Documented
In Previous Global Warming
Southern-dwelling trees and shrubs moved rapidly north 55 million years ago to survive during a period of global warming, according to a study of fossil leaves by federally funded scientists.
The study, which appeared in the Nov. 11 issue of the journal Science, showed that some plants -- among them relatives of papaw, poinsettia and sumac -- migrated from the Gulf Coast to Wyoming, a distance of about 1,000 miles, in 10,000 years or less. It happened during the Paleocene-Eocene Thermal Maximum, when global temperatures rose by as much as 18 degrees Fahrenheit.
Scott Wing, a paleobiologist at the Smithsonian Institution's National Museum of Natural History, who led the team, said the plants' ranges during this period changed as rapidly as they did when glaciers retreated in the past 20,000 years. Plants might respond similarly to today's human-induced global warming, Wing added, though habitat destruction because of development may make it harder for plants to disperse to a more favorable climate.
"No two events are ever exactly the same, but the history of life on this planet has a lot to tell us about our possible future," he said.
Scientists studied fossil leaves and pollen in the Bighorn Basin of northwestern Wyoming.
-- Juliet Eilperin
What Does the Body Good
May Boost Brain Power, Too
Light exercise may keep your brain in shape as well as your muscles.
Research on lab rats presented at the Society for Neuroscience's annual meeting in Washington this weekend showed that animals that exercised more experienced less brain damage from oxidation -- believed to be associated with memory loss and possibly Alzheimer's disease in humans.
The researchers found evidence of decreased cellular aging in tissue samples from the more active rats. Their brain cells had healthier molecular fats -- needed to keep cell membranes strong -- and healthier DNA than samples from the more sedentary animals.
"For this study animals were not forced to run; they did it because it was entertaining, the same as a pet hamster on a running wheel," said lead researcher Thomas Foster of the University of Florida College of Medicine. "The results show that regular mild exercise can prevent oxidative damage. In people, that translates to a daily 30-minute walk or a light one-mile run."
Foster said that after two years, the DNA from animals that had a wheel that allowed them to exercise moderately looked similar to animals that were six months old. Rats without a wheel for exercise had far more damage to the lipids and DNA in their cells.
The oxidative damage occurs when molecules of oxygen gain electrons and become free radicals -- a situation the body rebalances by passing electrons to neighboring molecules, but sometimes not before cell damage occurs.
The scientists will now research which natural chemicals and mechanisms are triggered by exercise to fight oxidative stress, and whether reducing the oxidation improves brain function.
-- Marc Kaufman