Dr. Robert Rosenson's Myths and Facts About Cholesterol


robert-rosenson
As our genes evolve, our risk factors for high LDL cholesterol increase.
(ROBERT ROSENSON)
Robert S. Rosenson, MD, is the director of lipoprotein disorders and clinical atherosclerosis research at the University of Michigan in Ann Arbor.

Q: Is the "total cholesterol" number my doctor talks about obsolete, or does it still have some value?

A: It has some relevance because, typically, the higher the cholesterol, the higher the bad cholesterol—but it also could be the higher the good cholesterol. And thats why we focus on HDL and LDL cholesterol. By focusing on the total cholesterol, people can often be misled about their risk [for cardiovascular disease] being too high or too low. One can have total cholesterol of 175 and HDL cholesterol of 25 and be at incredibly high risk for a cardiovascular event. By contrast, one can have total cholesterol of 240 and HDL cholesterol of 65 and not be at increased risk. So its the components that comprise the total cholesterol that are important.

Q: The thinking about cholesterol has changed rapidly in recent years. Has it stalled, or is it likely to continue to evolve?

A: People misunderstand the concept of cholesterol. Cholesterol is a fat that is easy to measure analytically. But cholesterol is carried in lipoproteins, and lipoproteins are what contribute to atherosclerosis. So we need to start thinking in terms of lipoproteins, and therapies that modify lipoproteins, instead of just the cholesterol carried in the lipoproteins.

This is very relevant because individuals who are obese and insulin-resistant—such as those with the metabolic syndrome or type 2 diabetes—do not have elevated LDL cholesterol levels but they have an increased number of LDL particles that puts them at a substantially increased risk for cardiovascular events. So this is where the terminology needs to change from a cholesterol concept to a lipoprotein concept.


Q: Are lipoproteins harder to test for?

A: They are, but commercial tools are available to measure lipoproteins or apolipoproteins, the major protein on the particles. Apolipoprotein tests are available in all hospital laboratories. Lipoprotein subclasses can be measured through three methodologies: nuclear magnetic resonance, ultracentrifugation, and gradient gel electrophoresis.

Q: What about triglycerides?

A: Triglycerides have emerged as a significant independent risk predictor for coronary heart disease (CAD). There was a large meta-analysis of 263,000 individuals that showed that high triglycerides were associated with a 1.72-fold increased risk of CAD events. LDL cholesterol was about 1.8–2.0, so elevated triglycerides are not so far behind LDL cholesterol. High triglycerides often predate or antedate the development of type 2 diabetes and are often a predictor of CAD.




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Last Updated: August 12, 2008

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