Featured Research

from universities, journals, and other organizations

New Mechanism Increases Atherosclerosis In Mice

Date:
November 9, 2009
Source:
Rockefeller University
Summary:
A shot of espresso may rev you up in the morning, but the downside is that it may also ramp up levels of bad cholesterol due to its effects on a unique liver protein called PXR. New research now shows that when chronically activated, the protein rejiggers how cholesterol is broken down in and cleared from the liver, a disturbance that can lead to high levels of the waxy substance or worse, full-blown atherosclerosis.

Hard evidence. Unlike mice that are fed a normal diet (top), those fed a diet laced with a PXR-activating drug (bottom) develop clogged arteries, a symptom of atherosclerosis.
Credit: Image courtesy of Rockefeller University

A shot of espresso may rev you up in the morning, but the downside is that it may also ramp up levels of bad cholesterol due to its effects on a unique liver protein called PXR. New research from Rockefeller University now shows that when chronically activated, the protein rejiggers how cholesterol is broken down in and cleared from the liver, a disturbance that can lead to high levels of the waxy substance or worse, full-blown atherosclerosis.

"It's the first time that PXR has been shown to have a direct impact on balancing cholesterol levels in the body," says first author Changcheng Zhou, a research associate in Jan L. Breslow's Laboratory of Biochemical Genetics and Metabolism at Rockefeller.

Unlike other receptor proteins, which can recognize only one or a few chemicals, PXR -- short for pregnane x receptor -- can recognize more than a hundred, including cafestrol, present in unfiltered brewed coffee, and many prescription medications. The research, led by Breslow, may have direct clinical consequences for patients taking drugs such as the antibiotic rifampicin for tuberculosis treatment, the antiretroviral drug ritonavir for HIV treatment and the antiepileptic drugs carbamazipine and phenobarbital, all of which activate PXR.

"At the time these drugs were being developed -- the antivirals, the antibiotics, anti-cancers and even herbal supplements like St. John's Wort -- their interactions with PXR weren't known," explains Zhou. "Now patients under long-term treatment with PXR-activating drugs can be more informed about these drugs' effects."

When activated, PXR, which resides in the nucleus of liver cells in all animals, including humans, latches on to strips of DNA and turns on genes that regulate how chemicals or drugs are metabolized and cleared from the liver. Many drugs that can activate PXR have been shown to increase cholesterol levels in patients, and too much of the stuff in the bloodstream is a well-established risk factor for cardiovascular disease, the nation's biggest killer. However, it was not clear whether PXR could jumpstart this process.

In their work, Zhou and Breslow introduced a mouse-specific PXR activator called PCN into the diets of normal mice for two weeks and found that while their levels of good cholesterol, or HDL, were not affected, their levels of bad cholesterol skyrocketed six-fold. Another group of mice that were fed PCN for eight weeks and were genetically engineered to lack the protein ApoE experienced the flipside: Their good cholesterol plummeted and they also went on to develop full-blown atherosclerosis.

Several gene targets of PXR were the same for both normal mice and those lacking the ApoE protein, including a cholesterol metabolism enzyme called CYP39A1 and a transportation protein called Apo-IV. A gene called CD36 was another target specifically associated with the uptake of modified bad cholesterol by certain cells, which contribute to the accumulation of artery-clogging fat.

To Zhou, this research is only the beginning. "Many chemicals exposed in the air are also PXR activators," says Zhou. "So what we have in our hands now may not only be a heart health issue but also a public health one."


Story Source:

The above story is based on materials provided by Rockefeller University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Zhou et al. Activation of PXR induces hypercholesterolemia in wild-type and accelerates atherosclerosis in apoE deficient mice. The Journal of Lipid Research, 2009; 50 (10): 2004 DOI: 10.1194/jlr.M800608-JLR200

Cite This Page:

Rockefeller University. "New Mechanism Increases Atherosclerosis In Mice." ScienceDaily. ScienceDaily, 9 November 2009. <www.sciencedaily.com/releases/2009/11/091106112119.htm>.
Rockefeller University. (2009, November 9). New Mechanism Increases Atherosclerosis In Mice. ScienceDaily. Retrieved October 2, 2014 from www.sciencedaily.com/releases/2009/11/091106112119.htm
Rockefeller University. "New Mechanism Increases Atherosclerosis In Mice." ScienceDaily. www.sciencedaily.com/releases/2009/11/091106112119.htm (accessed October 2, 2014).

Share This



More Health & Medicine News

Thursday, October 2, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Pregnancy Spacing Could Have Big Impact On Autism Risks

Pregnancy Spacing Could Have Big Impact On Autism Risks

Newsy (Oct. 1, 2014) A new study says children born less than one year and more than five years after a sibling can have an increased risk for autism. Video provided by Newsy
Powered by NewsLook.com
Robotic Hair Restoration

Robotic Hair Restoration

Ivanhoe (Oct. 1, 2014) A new robotic procedure is changing the way we transplant hair. The ARTAS robot leaves no linear scarring and provides more natural results. Video provided by Ivanhoe
Powered by NewsLook.com
Insertable Cardiac Monitor

Insertable Cardiac Monitor

Ivanhoe (Oct. 1, 2014) A heart monitor the size of a paperclip that can save your life. The “Reveal Linq” allows a doctor to monitor patients with A-Fib on a continuous basis for up to 3 years! Video provided by Ivanhoe
Powered by NewsLook.com
Attacking Superbugs

Attacking Superbugs

Ivanhoe (Oct. 1, 2014) Two weapons hospitals can use to attack superbugs. Scientists in Ireland created a new gel resistant to superbugs, and a robot that can disinfect a room in minutes. Video provided by Ivanhoe
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins