Biology

ATLANTIC BILINGUAL SCHOOL

BIOLOGY ARTICLE


OCT. 4, 2010

Dieting Monkeys Offer Hope for Living Longer
Known as caloric restriction, the diet has all the normal healthy ingredients but contains 30 percent fewer caloriesthan usual. Mice kept on such a diet from birth have long been known to live up to 40 percent longer than comparisonmice fed normally.
Would the same be true in people? More than 20 years ago, two studies of rhesus monkeys were begun to see if primates responded to caloric restriction the same way that rodents did. Since rhesus monkeys live an average of 27 years and a maximum of 40, these are experiments that require patience.
The results from one of the two studies, conducted by a team led by Ricki J. Colmanand Richard Weindruch at the University of Wisconsin, were reported Thursday in Science. The researchers say that now, 20 years after the experiment began, the monkeys are showing many beneficial signs of caloric resistance, including significantly less diabetes,cancer, and heart and brain disease. “These data demonstrate that caloric restriction slows aging in a primate species,” they conclude.Some critics say this conclusion is premature. But in an interview, Dr. Weindruch called it “very good news.”
“It says much of the biology of caloric restriction is translatable into primates,” he said, “which makes it more likely it would apply to humans.”
In terms of deaths, 37 percent of the comparison monkeys have so far died in ways judged to be due to old age, compared with 13 percent ofthe dieting group.
Dr. Weindruch and his statistician, David Allison of the University of Alabama, Birmingham, said the dieting monkeys were expected to enjoy a life span extension of 10 percent to 20 percent, based on equivalent studies started in mice at the same age.
Few people can keep to a diet with 30 percent fewer calories than usual. So biologists have been looking for drugs that mightmimic the effects of caloric restriction, conferring the gain without the pain. One of these drugs is resveratrol, a substance found in red wine, though in quantities too small to have any effect.
Dr. Weindruch said the study data offered “very encouraging” signs that resveratrol could duplicate in people some of the effects of caloric restriction.
Critics, however, are not yet ready to acceptthat the rhesus study proves caloric restriction works in primates.
If caloric restriction can delay aging, then there should have been significantly fewer deaths in the dieting group of monkeys than in the normally fed comparison group. But this is not the case. Though a smaller number of dieting monkeys have died, the difference is not statistically significant, the Wisconsin team reports.
TheWisconsin researchers say that some of the monkey deaths were not related to age and can properly be excluded. Some monkeys died under the anesthesia given while taking blood samples. Some died from gastric bloat, a disease that can strike at any age, others from endometriosis. When the deaths judged not due to aging are excluded, the dieting monkeys lived significantly longer.
Some biologiststhink it is reasonable to exclude these deaths, but others do not. Steven Austad, an expert on aging at the University of Texas Health Science Center, said some deaths could have been due to caloric restriction, even if they did not seem to be related to aging. “Ultimately the results seem pretty inconclusive at this point,” Dr. Austad said. “I don’t know why they didn’t wait longer to publish.”Leonard Guarente, a biologist who studies aging at the Massachusetts Institute of Technology, also had reservations about the findings. “The survival data needs to be fleshed out a little bit more before we can say that caloric restriction extends life in primates,” Dr. Guarente said. In mouse studies, people just count the number of dead animals without asking which deaths might be unrelated to...