Despite the strong links between cholesterol and heart disease, more than half of all patients with heart attacks have a normal cholesterol profile and no other well-established risk factors. Clearly, other factors are involved in the development of coronary artery disease in these people. These same factors may also contribute to development of atherosclerosis in people with unfavorable cholesterol levels. The following are among the leading other possible risk factors:
■ Elevated blood levels of homocysteine have been implicated as a strong predictor for heart disease, independent of the person’s cholesterol or lipid profle. Homocysteine is formed as an intermediate product during metabolism of the essential dietary amino acid methionine. Investigators believe homocysteine contributes to atherosclerosis by promoting proliferation of vascular smooth muscle cells, an early step in development of this condition. Furthermore, homocysteine appears to damage endothelial cells and cause oxidation of LDL, both of which contribute to plaque formation. Three B vitamins—folic acid, vitamin B12 and vitamin B6—all are important in pathways that clear homocysteine from the blood.
■ People with elevated levels of C-reactive protein (CRP) , a bloodborne marker of inflammation, have a higher risk for developing coronary artery disease. About half of all people who have a heart attack have high CRP, whereas high CRP is much less common in those without heart disease. Because inflammation plays a crucial role in the development of atherosclerosis, anti-inflammatory drugs such as aspirin help prevent heart attacks. Furthermore, aspirin protects against heart attacks through its role in inhibiting clot formation. Also, statin drugs not only lower LDL, but also have antiinflammatory effects.
■ Accumulating data implicate an infectious agent as the underlying culprit in some cases of atherosclerotic disease. Among the leading suspects are respiratory infection–causing Chlamydia pneumoniae, cold sore–causing herpes virus, and gum disease–causing bacteria. If a link between infections and coronary artery disease can be confrmed, antibiotics may be added as a heart-disease prevention strategy. As you can see, the relationships among atherosclerosis, cholesterol, and other factors are far from clear. Much research on this complex disease is currently in progress because the incidence of atherosclerosis is so high and its consequences are potentially fatal.
Source: Human Physiology, Sherwood.
