Psychic hotline for MIs

Portentous peptide predicts heart attack risk in men � the healthy ones and the overweight boozers with a pack-a-day habit

By Sharon Rueben

Michael Kirin just celebrated his 50th birthday two days ago. Unfortunately it didn't turn out to be quite the party he had in mind for the big 5-0. There was cake and there were balloons, but the atmosphere was decidedly sombre, which is pretty normal since the celebration took place in a cramped hospital room. Michael, a lawyer, had suffered a heart attack five days earlier while prosecuting a case in court. A small group of friends and family put on brave faces and tried to salvage the occasion, but Michael couldn't shake the melancholy mood he was in. He kept asking himself why there hadn't been any warning signs. He'd never been diagnosed with heart disease and as far as he knew wasn't particularly at risk � he watched what he ate, went regularly to the gym, and had never smoked. If he'd had an inkling that he was at risk for an attack, maybe it could have been prevented.

If a recent study continues to bear fruit, there could be a predictive test in the not-too-distant future to warn seemingly healthy people like Michael that they might be at risk for suffering a myocardial infarction (MI). Researchers at the Harvard School of Public Health have found a link between plasma levels of adiponectin peptide and MI risk in men. High levels of adiponectin may be related to a lower risk of MI, according to their paper published in the April 14 issue of The Journal of the American Medical Association.

"Adiponectin is a recently discovered adipocyte-derived peptide, and is involved in the regulation of insulin sensitivity and lipid oxidation. Adiponectin is also inversely associated with traditional cardiovascular risk factors, such as blood pressure, heart rate, and total and low-density lipoprotein cholesterol and triglyceride levels, and is positively related to high-density lipoprotein cholesterol levels," writes lead author Dr Tobias Pischon. The exact mechanism of the peptide isn't known but the authors note that "recent studies suggest that it may have antiatherogenic and anti-inflammatory properties."

PROMISE OF PREVENTION
The large study used data from the Health Professionals Follow-up Study to identify 18,225 men aged 40 to 75 who were free of cardiovascular disease. During the six-year follow up, 266 men experienced a cardiovascular event � 196 had a nonfatal MI and 70 died from coronary heart disease (CHD). To form a heart disease-free control group, 532 men were randomly selected and matched two to one with the cardiovascular event case group subjects for age, date of blood sample and smoking status. In the case group, adiponectin levels were significantly lower, at 15.6mg/L, than the control population, who had 17.9mg/L, leading the authors to surmise that "high plasma adiponectin levels may be related to a lower risk of coronary heart disease."

Another surprising find was that adiponectin's predictive value was independent of traditional risk factors such as family history of MI, body mass index, alcohol consumption, physical activity, smoking, diabetes and hypertension. This study is the first to suggest that the peptide may predict cardiovascular events years in advance in people with undiagnosed heart disease. The findings are significant, though the authors do acknowledge that there are some limitations to the study. These include the absence of female participants, the limited timeframe, and the possibility that subjects might have had atherosclerosis that was undetected when they enrolled in the study.

The predictive value of adiponectin holds promise for prevention of an attack for those with low levels of the peptide. Whether the data will hold up for women and in longer-term studies remains to be seen.