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Appetites are linked to enzyme

Scientists say an enzyme in the brain that monitors energy in cells also appears to regulate appetite and weight, a discovery that could lead to new treatments for obesity.

The enzyme is known as AMP-activated protein kinase, or AMPK. Its activity is regulated by the hormone leptin, which previously was linked to appetite suppression.

Harvard researchers found in experiments with mice that when AMPK was inhibited, the animals ate less and lost weight. When AMPK levels were boosted, the mice ate more and gained weight.

Barbara B. Kahn, the lead author of the study, said the work identifies a new leptin signaling pathway and a promising new target in humans.

The study appeared Wednesday in an online version of the journal Nature.

Some researchers believe AMP-kinase might be more effective in weight control than leptin because it works more directly on appetite. Clinical trials on human patients will take years to complete, researchers said.

WASHINGTON - A type of artificial heart moved a step closer to the U.S. market Wednesday, but it's not a permanent replacement - just a temporary device to keep certain patients alive long enough to receive a heart transplant.

There are serious questions about who should get the CardioWest Total Artificial Heart, a complex and risky device that requires cutting out the bottom half of the heart to implant, scientific advisers to the Food and Drug Administration cautioned.

Still, they concluded it should sell because it could benefit a small number of patients.

"These people are dying who don't have any good alternative," said Dr. Judah Weinberger of Columbia University as the panel voted 10-1 to recommend approval. The FDA isn't bound by the panel's advice, but usually follows it.

Some 3,460 people were on the national waiting list for a heart transplant Wednesday; just over 2,000 receive a heart each year.

The average person born in the United States can expect to live to the respectable, if not ripe, old age of 77.4 years - up two-tenths of a year to a new record high.

Men still lag years behind women, and blacks continue to trail whites, but the encouraging news is this: People in each group have bought themselves a little more time.

Life expectancy - a fundamental measure of a society's well-being - has been climbing steadily for more than a century, thanks in large part to public health advances such as clean water and antibiotics. But, given how far we've come, it can't be expected to climb much higher.

"While we may be experiencing some increases today, unless there's some sort of major medical breakthrough, these increases are going to slow down and probably come to a halt," said S. Jay Olshansky, an epidemiologist at the University of Chicago and an expert on longevity.

By "breakthrough," Olshansky means something far bigger than finding a cure for America's three leading killers: heart disease, cancer and stroke. Even wiping out cancer, which causes more than a quarter of the 2.4-million deaths annually, would add only about 31/2 years to the country's overall average life expectancy, he said.

The problem is that people who overcome that disease will die of something else. Our bodies, after all, are not built to last.

In extending our life expectancy, we have become victims of our own success. The higher it climbs, experts say, the harder it will be to record further gains.

"When you save a baby from dying, you add many more years to life. When you save an 80-year-old from dying, by comparison, you add many fewer years to life," Olshansky said. "We've achieved most of the gains that can be achieved by saving the young, and now the vast majority in the rise in life expectancy has to result in saving population over the age of 50."

The new life-expectancy figures apply to babies born in 2002.