The fact that even young men can develop atherosclerosis was reported following autopsies of German soldiers during World War I. However, it was a U.S. Armed Forces Institute of Pathology report toward the end of the Korean War (Enos et al., 1953) showing that young men (average age 22) had evidence of coronary heart disease (CHD) that made the medical profession take note of the epidemic that was CHD. The problem is still extensive in spite of considerable, but slow, progress since the 1950s. By the early 1980s there were 5.4 million Americans with symptomatic diagnosed CHD. The number of undiagnosed cases is, of course, unknown. In any case, the results were 1.5 million heart attacks and over 550,000 deaths. A review of the medical literature since the late 1950s shows the name cholesterol, and particularly hypercholesterolemia (HPC), to be associated with CHD with increasing frequency. By the early 1970s HPC was implicated as the primary CHD risk factor. Hypertension and smoking are now also recognized as important risk factors.
More recently the term hyperlipoproteinemia has become useful. Saturated fatty acids, usually esterified to glycerol as triacylglycerides (i.e., fats), can be related to cardiovascular disease since they increase plasma cholesterol levels. This cholesterol is now known to be primarily associated with a low-density lipoprotein (LDL) fraction. Lipoproteins are complex particles consisting of proteins, triacylglycerol (fat), phospholipids, cholesterol, and cholesterol esters. LDL has density of 1.00-1.06 and contains at least 45% cholesterol. It is the cholesterol found in the LDL fraction that is the harbinger of human arterial plaque manifested as atheroma. An inverse relationship has been established between cholesterol in high-density lipoprotein (HDL) (d = 1.20, 18% cholesterol) and CHD. HDL transports cholesterol from accumulation in arterial walls to the liver for biodégradation.
In the popular literature HDL is frequently referred to as "good cholesterol" and LDL as "bad cholesterol." Blood chemistry reports often state total cholesterol levels, even though LDL and HDL values (or their ratios) would probably be more relevant to a patient's clinical evaluation. Total serum cholesterol levels, normally reported in milligrams/deciliter (mg%) do not indicate the fraction that is free, esterified, or bound up in the various lipoprotein fractions.
Developments in genetic research, when combined with population studies, have made it clear that low levels of HDL actually increase the risk of cardiovascular disease. At the same time, a high level of cholesterol in the form of LDL is the primary etiological factor
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