Heart Differences Obscure Enzyme May Explain Mystery - why men die younger

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Heart Differences: Obscure Enzyme May Explain Mystery

Winona

Daily News

 

 

 

 

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.

 

 

 

 

 

 

 

 

 

Associated Press

SANTA FE,

N.M. — 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.

Shirild 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."