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Toward a Better Understanding of Lipids and Heart Disease Risk: A study of genetic mutations explores the relationships between cholesterol, triglycerides, and apolipoprotein B.

When we get our annual bloodwork, one of the top numbers we hear about is the cholesterol level. It is widely accepted that elevated low-density lipoprotein (LDL) cholesterol increases the risk of coronary heart disease (CHD). But while regular blood checks also measure triglycerides, less is known about their role in CHD risk. A team of researchers turned to genetics to shed new light on how these two fats compare when it comes to heart health.

They reported in the January issue of JAMA that reducing triglycerides can lower CHD risk as much as reducing cholesterol, but they suggest that the real story isn't as simple as looking at just cholesterol or just triglycerides. The true risk-reduction may actually come from how reducing those fats affects a third player: apolipoprotein B (APOB).

What the Study Assessed. The researchers analyzed data from close to 700,000 people enrolled in 63 cohort or case-control studies to identify genetic mutations that affect triglyceride levels (in the lipoprotein lipase gene [LPL]) and LDL cholesterol (in the LDL receptor). They developed genetic scores, which researchers use to understand how genetic variations affect risk, and looked at how those scores were related to CHD risk per unit of lowered APOB. They found that each 10-milligram/deciliter (mg/dL) reduction of APOB resulted in a similar lower risk of CHD--regardless of whether it came from triglyceride or cholesterol reduction. The researchers concluded that the benefit of reducing triglycerides or LDL cholesterol may depend on how those changes affect APOB.

The APOB Test. Some experts have suggested that testing APOB is a superior way to assess CHD risk. APOB levels can be elevated in a person with normal LDL levels, which may be why one study found that about half of the people hospitalized for heart attacks had normal or low LDL levels. A favorable level of APOB is less than 100 mg/dL, but people with existing cardiovascular disease or diabetes should aim for less than 80 mg/dL or even lower. APOB assays are difficult to standardize, however, and some specialists prefer physical measurement of lipoprotein particle numbers by nuclear magnetic resonance or ion mobility.

If your doctor doesn't yet order the APOB or particle number test, don't be surprised. Experts note that busy primary care physicians might not be looking to add even more tests when the standard cholesterol screens are already pretty good. As research and pharmaceutical industry interest grows, that may change in the future.


About the Cast of Characters

Both cholesterol and triglycerides are insoluble in water, so they can't travel in blood on their own. Instead, they hitch a ride on different types of lipoproteins.

* Very-low-density lipoproteins (VLDL) carry about 85 percent of triglycerides.

* Low-density lipoproteins (LDL) carry cholesterol throughout the body.

* High-density lipoproteins (HDL) transport cholesterol out of the body.

* APOB is a surface molecule that travels on lipoprotein particles such as VLDL and LDL, but not HDL. Because there is one APOB per particle, it can be used to measure the number of cholesterol-and triglyceride-carrying particles in the blood.

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Title Annotation:CARDIOLOGY
Publication:Duke Medicine Health News
Article Type:Disease/Disorder overview
Date:Jun 29, 2019
Next Article:A Complicated Dance.

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