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Liver protein may explain younger women's low risk of heart disease SANTA FE, N.M. (March 21, 1998 6:54 p.m. EST http://www.nando.net) -- New discoveries about an enzyme that regulates cholesterol levels could help explain one of the enduring mysteries of the sexes -- why men die younger than women from heart disease. Everywhere researchers have looked in the world, heart disease strikes men at earlier ages than women. In Western countries, where heart trouble is the biggest killer of both sexes, men generally die from it about 10 years sooner. Differences in traditional risk factors -- high blood pressure, smoking and obesity, among others -- do not entirely explain this disparity, nor do the obvious hormonal and physical differences. However, scientists say their research into gender differences in a liver enzyme called hepatic lipase may well explain why women typically have better cholesterol levels than men, especially before menopause when their risk of heart trouble is very low. Dr. John E. Hokanson of the University of Washington in Seattle presented the findings at an American Heart Association conference, which concluded Saturday. Younger women's risk is low because of their favorable lipid profiles -- the types, not just the quantity, of cholesterol in their blood. Cholesterol and fats called triglycerides cannot dissolve in blood. So they are carried through the bloodstream by transport molecules called lipoproteins, which are produced by the liver. The liver also makes hepatic lipase, which breaks down these combinations so the fats can be used by the body. Most of the cholesterol is transported by low-density lipoprotein, or LDL. This is generally called the bad cholesterol, since it deposits excess cholesterol on the artery walls and leads to blockages. LDL also comes in different sizes, and small, dense LDL is considered especially harmful. High-density lipoprotein, or HDL, is helpful, because it carries cholesterol and fats out of the bloodstream before they harm the arteries. The higher the proportion of HDL, the lower the risk of heart attacks. Typically, young women have higher HDL, lower LDL and less dense LDL than do men the same age. Hokanson and colleagues tested 25 men and 39 premenopausal women. They ranged in age from 21 to 59 and had normal cholesterol levels. Hepatic lipase levels were 53 percent higher in the men. Hokanson found that the men's higher amounts of this enzyme could explain 42 percent of the difference between the sexes in the density of the LDL they carried. And it could explain 97 percent of the difference between men and women in HDL levels. "We believe that hepatic lipase is an important modulator of HDL," said Hokanson. "This accounts for the difference in coronary risk lipid profiles in men and women." While he said this does not explain all of the difference in heart disease risks between the sexes, it could play a significant part. Experts think women's risk goes up after menopause because they lose the protective effects of estrogen, the female sex hormone. Estrogen appears to regulate the body's levels of hepatic lipase, and Hokanson found this enzyme increases after menopause. Hokanson said estrogen's effects on this enzyme may be one reason why hormone replacement therapy significantly lowers older women's risk of heart attacks. He said cholesterol-lowering drugs also may work by affecting levels of hepatic lipase. In the United States, 29 percent of men in their 40s have cardiovascular disease, compared with 17 percent of women. By the time they reach their 70s, about 70 percent of both sexes have heart disease. Dr. Shiriki Kumanyika of the University of Illinois at Chicago said understanding the reasons for young women's protection could help men of all ages, as well as older women. "The question is: What is it about women?" she said. "Why don't they get heart disease so soon? If we could figure that out, maybe we could give it to men." By DANIEL Q. HANEY, AP Medical Editor Copyright 1998 Nando.net Copyright 1998 The Associated Press janet paterson 51-10 / sinemet-selegiline-prozac almonte-ontario-canada / [log in to unmask]