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Living
Longer and Larger: It's in the Size of Cholesterol-Carrying Molecules
By
Mary Duenwald, the Scientists trying to figure out why just 1 person in 10,000 lives to be 100 have found an important clue in the blood. Centenarians, a new study shows, tend to have larger than average cholesterol-carrying molecules. The study, to be published today, in The Journal of the American Medical Association, adds to an emerging collection of evidence that suggests that the size of lipoproteins, both good and bad, may play a significant role in heart disease, diabetes and, consequently, longevity. "Large particle size seems to give people an extra 20 years of
life, with very little disability to go along with it," said Dr. Nir
Barzilai, who directed the study at the Albert Einstein College of
Medicine in the Dr. Barzilai also traced large lipoproteins to a specific gene that influences lipoprotein size. The study looked at 213 centenarians and 216 of their offspring, as well as a control group of 256 people in their 60's and 70's whose parents did not live to 100. The three groups were similar in their average total cholesterol; in their bad cholesterol, or low density lipoproteins; and in their body mass indexes, which are based on a ratio of height and weight and are used to gauge whether people are overweight. The centenarians and offspring, as would be expected, had higher levels of the good cholesterol. But when the researchers looked at lipoprotein size, the centenarians stood out. Eighty percent of them were found to have an unusually high proportion of large particles. Nearly half of their children also had the large particles, suggesting an even chance of inheriting the quality, Dr. Barzilai said. Just 8 percent of the control group had the larger lipoproteins. The researchers also found that subjects with cardiovascular problems were less likely to have large lipoproteins. "It's no surprise that centenarians would be specially protected
against cardiovascular disease," said Dr. Thomas T. Perls, a
geriatrician at the Another centenarian researcher, Dr. James W. Vaupel, director of the
Max Planck Institute for Demographic Research in Smaller lipoprotein size "looks to be a risk factor for cardiovascular disease," Dr. Vaupel said. "But there are many other risk factors — high blood pressure, smoking, eating a fatty diet, not getting enough exercise." In the last five years, other researchers have also found a connection
between small molecules of the bad cholesterol, or L.D.L., and the
perilous buildup of plaques in the arteries. Small L.D.L. particles are
better at digging into the walls of blood vessels and creating the
conditions for plaques to form, said Dr. W. Timothy Garvey, chairman of
nutrition sciences at the "All L.D.L. particles are bad," Dr. Garvey said. "But the smaller ones are worse than the bigger ones." When people who have been sedentary start performing regular exercise,
their L.D.L. particles grow bigger, as shown by Dr. William E. Kraus, a
cardiologist at the "For years," Dr. Kraus said, "scientists had known that exercise helped prevent heart disease. But we didn't know how it could be beneficial, because it didn't affect cholesterol levels. Now we know that exercise makes small dense L.D.L. particles larger and fluffier." How size affects the operation of the good cholesterol, or high density lipoproteins, is not known. H.D.L. carries cholesterol out of the blood vessels and into the liver. One possibility is that the larger H.D.L. molecules simply carry a bigger load. But, Dr. Barzilai said, "The situation may be more complex." He traced the larger particles from a mutation in a gene that is responsible for creating a protein, C.E.T.P., or cholesterol ester transfer protein, which helps regulate the size of cholesterol particles. Dr. Barzilai found that nearly 25 percent of the centenarians in his study carried two copies of a particular variant of the gene that suppresses C.E.T.P. activity. In the control group, just 8 percent had the variant. The gene may be one reason why some centenarians in Dr. Barzilai's study have lived to 100, even though they were overweight or ate badly. "I hate to say it," he said. "but I think it's true. If you have this gene, you can smoke and you can be fat and you can not exercise. This sounds to me terrible." Dr. Barzilai suspects that perhaps four or five other genes also have roles in determining lipoprotein size. He said he had begun to zero in on a second gene that appears to be as important as the C.E.T.P. gene. Copyright
© 2002 Global Action on Aging |
