Hidden Heart Hazards

Abstract

E i 0 new predictor of heart disease risk and could force them to reexamine dietary prescriptions for improving heart health. By some estimates, up to 25 percent of trim people in the United States inherit or acquire an inefficient response to insulin, the pancreas-secreted hormone that directs cells to take up glucose. These people are not diabetic, but their lethargic response to insulin means the pancreas must churn out more of the hormone to keep blood sugar levels normal. Most diabetes specialists believe people with insulin resistance face a risk of developing Type II, or non-insulindependent, diabetes when the pancreas exhausts its ability to crank out enough hormone to meet the body's needs. Not everyone with insulin resistance develops Type II diabetes, which generally strikes after age 40. Yet even in those who escape it, some researchers now believe that a long-standing elevation of insulin in the blood silently damages the cardiovascular system by an unknown process that results in the buildup of fatty deposits on artery walls. That theory has sobering implications for outwardly healthy people with insulin resistance as well as for the 10 million Type 11 diabetics in the United States, most of whom are insulin resistant. Resistance to insulin-stimulated glucose uptake is involved in the development of coronary artery contends Gerald M. Reaven of Stanford University School of Medicine. Although this concept may seem outlandish at first blush, the notion is consistent with available experimental data. Reaven's 20 years of research on insulin resistance led him in 1988 to coin the term X, describing seemingly healthy people who have insulin resistance and display a cluster of coronary risk factors, including high blood pressure, elevated triglycerides (a form of lipid, or fat, in the bloodstream) and decreased high-density lipoproteins, or HDLs the beneficial transport molecules that carry cholesterol from the bloodstream to the liver for excretion (SN: 9/9/89, p.171). Insulin resistance may explain why Type 11 diabetics are two to four times as likely as nondiabetics to develop heart disease, running a coronary risk comparable to that of insulin-dependent, Type I diabetics without kidney disease. But Reaven's theory of syndrome X goes well beyond diabetics in stating that trim, outwardly healthy people with a defective insulin response also face a greaterthan-average risk of heart disease a notion many diabetes specialists view with cautious skepticism. It's an interesting idea, but [syndrome X] is not proven by the data, comments diabetes researcher Daniel W Foster of the University of Texas Southwestern Medical Center in Dallas. Adds cholesterol researcher Scott M. Grundy, also at Southwestern Medical Center: Syndrome X might be syndrome zero. Nonetheless, the notion is attracting considerable attention as new scientific reports from around the world support the link between insulin resistance and coronary artery disease.