by

Joseph

Having high levels of good cholesterol doesn't necessarily prevent a person from developing heart disease, new research suggests. According to the results of a study published in Science, a rare genetic defect prevents cells from taking up circulating good cholesterol. This finding suggests that people with this genetic variant may require special attention to reduce their cardiovascular disease risk.

While most of us can rely on high density lipoprotein (HDL) to protect us from a build up of cholesterol in the bloodstream; this is due to the presence of Scavenger receptor BI (SR-BI) which binds cholesteryl esters to HDL in the liver. But an international team of researchers discovered that a rare gene prevents HDL from clearing cholesterol in certain individuals.

Research scientist Paolo Zanoni from the University of Pennsylvania, led a team which sought to better understand what would happen to cholesterol levels if the SR-BI was unable to properly do its job.

To find the answer, Zanoni et al used genetic sequencing to identify 328 individuals who carrying a rare defect that prevents SR-BI from functioning. People with the genetic defect are at great risk for cardiovascular disease.

To get a better handle on what this means, we need to take a step back and talk briefly about receptors and genes.

You can think of receptors as locks. When you want to enter a locked room, you need a key that fits the lock. If the lock is broken, you won't be able to open the door even though the key fits.

Genes can be thought of as the lock maker. If there is something wrong with the lock maker, it will produce defective locks.

Now imagine that you have a lot of deliveries arriving at a certain address, and a key is required to get into the room to deposit the deliveries. Because the lock doesn't work, the deliveries are left outside. Unfortunately, there's no way to stop the deliveries so they continue to arrive at the locked room. Eventually the deliveries pile up outside the room causing a huge problem.

That's what happens to people who have a broken SR-BI gene. Even though they have high levels of HDL (the good cholesterol), they're still at great risk for heart disease.

HDL can't properly bind the cholesteryl esters which which prevents the liver from removing excess cholesterol from the body the way it was meant to. Because the liver can't do its job, these people will have increased amounts of circulating cholesterol which eventually clogs the arteries thereby putting them at greater risk for heart attacks and strokes.

Therefore, identifying carriers of these defective genes and finding a way to correct the problem is very important.

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Article Reference

Zanoni P, Khetarpal SA, Larach DB, Hancock-Cerutti WF, Millar JS, Cuchel M, DerOhannessian S, Kontush A, Surendran P, Saleheen D, Trompet S, Jukema JW, De Craen A, Deloukas P, Sattar N, Ford I, Packard C, Majumder Aa, Alam DS, Di Angelantonio E, Abecasis G, Chowdhury R, Erdmann J, Nordestgaard BG, Nielsen SF, Tybjærg-Hansen A, Schmidt RF, Kuulasmaa K, Liu DJ, Perola M, Blankenberg S, Salomaa V, Männistö S, Amouyel P, Arveiler D, Ferrieres J, Müller-Nurasyid M, Ferrario M, Kee F, Willer CJ, Samani N, Schunkert H, Butterworth AS, Howson JM, Peloso GM, Stitziel NO, Danesh J, Kathiresan S, Rader DJ, CHD Exome+ Consortium, CARDIoGRAM Exome Consortium, & Global Lipids Genetics Consortium (2016). Rare variant in scavenger receptor BI raises HDL cholesterol and increases risk of coronary heart disease. Science (New York, N.Y.), 351 (6278), 1166-71 PMID: 26965621

"Rare Defect May Cause Good Cholesterol To Increase Heart Disease Risk" copyright © 2016 Living Fit, Healthy and Happy_(SM). All Rights Reserved.

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