Fitness Study Shows Differences in Blood Vessel Repair, Fat Hormone

Fit, healthy people tend to have higher numbers of circulating cells that regenerate blood vessels, a new study from Emory University shows.

Findings were presented Sunday, March 30, 2008, at the American College of Cardiology's 57^th Annual Scientific Session in Chicago.

A team of scientists, led by Emory cardiologist Arshed Quyyumi, MD, professor of medicine, Emory University School of Medicine, measured the ability of 33 healthy middle-aged subjects of normal weight to withstand aerobic exercise. They also measured the levels of leptin and endothelial progenitor cells in study participants' blood.

"We have shown for the first time in a healthy population that increased fitness and reduced body fat are associated with higher levels of circulating progenitor cells," says cardiology researcher Mick Ozkor, MD, Emory University School of Medicine, who presented the data.

"Exercise may be the reason for the differences in regenerative capacity, even in apparently healthy individuals without risk factors," adds Dr. Ozkor.

Endothelial progenitor cells repair blood vessels by providing new cells that form blood vessels' linings. Previous studies have shown that exercise quickly increases their level in the blood, and a course of exercise can boost their numbers in patients with cardiovascular disease.

In addition, study findings show lean people with higher levels of leptin, an inflammatory hormone produced by fat cells, have fewer regenerative cells. Leptin's negative effects can be seen in healthy people free of cardiovascular risk factors, Dr. Ozkor says.

Leptin sends "I've had enough to eat" signals to the hypothalamus, a part of the brain that controls appetite. Most obese people appear to produce an abundance of leptin, but for them, leptin's appetite-controlling effects are muted. High levels of leptin also have been associated with inflammation and vascular disease.