Featured Research

from universities, journals, and other organizations

Protein Implicated In Decline Of Aging Hearts

Date:
October 6, 2003
Source:
Duke University Medical Center
Summary:
Duke University Medical Center researchers have linked elevated levels of a specific heart protein in elderly hearts to a decrease in the pumping ability of the heart.

DURHAM, N.C. – Duke University Medical Center researchers have linked elevated levels of a specific heart protein in elderly hearts to a decrease in the pumping ability of the heart.

Since levels of this protein, known as G-alpha-i, are also elevated in patients with congestive heart failure, the researchers believe that not only do they better understand why the heart's pumping ability decreases with age, but that there may be a pharmacological approach to prevent this age-related decline.

It is known that a class of drugs known as beta-blockers can improve the symptoms of patients with congestive heart failure. Interestingly, these drugs also reduce the levels of G-alpha-i, leading the researchers to speculate that beta-blockers drugs could be potentially used in healthy patients to forestall the natural decline of the aging heart.

The results of the Duke study were published today (Oct. 4, 2003) in the Journal of Cardiovascular Pharmacology. The study was support by the National Institutes of Aging.

G-alpha-i mediates signaling through a family of G protein-coupled receptors (GPCR), which are important in cardiac function. Beta-adrenergic receptors (beta-AR), which respond to the hormones epinephrine and norepinephrine in the so-called "fight-or-flight" response to increase cardiac output, are also members of this family.

G-alpha-i is one protein that can prevent these hormones from "coupling" to beta-ARs, thereby decreasing the heart's contractability. The mechanism of action for G-alpha-i appears to be its ability to block adenylel cyclase, an enzyme that resides within cells and is responsible for transmitting messages within the cell in response to hormonal stimulation.

"The results from our study suggest that the dampening of G-alpha-i activity in the human heart may improve the age-induced decreases in cardiac function," said Duke pharmocologist Madan Kwatra, Ph.D., principal investigator of the study. "From what we know now, it would seem logical to consider the use of beta-blockers in a preventative role. More research, however, is needed to prove this hypothesis."

Numerous studies in animals attempting to prove an association between elevated levels of G-alpha-i and failing hearts have been inconclusive, researchers said. However, Kwatra's team published results last year which demonstrated that an age-induced increase in G-alpha-i occurs in rat ventricles (lower heart chambers) and was the cause of a decrease in receptor-mediated activation of adenylyl cyclase seen in aged hearts, and they wanted to see if the same held true in humans.

For their studies, the Duke team collected samples of human atria, the upper chambers of the heart, from 28 patients undergoing surgery that required the use of the heart-lung machine. In order to hook up the circulatory system to the heart-lung machine, a small "plug" of atrial appendage tissue must be removed to attach the tubing. None of the patients had congestive heart failure.

Atrial samples were then divided into two 14-patient groups based on age: mature (40-55) and elderly (71-79).

"After thorough testing the samples, we found that levels of G-alpha-i were 82 percent higher in the elderly patients when compared to the younger patients," Kwatra continued. "Additionally, this is the first study to show that G-alpha-i can be activated through more than one GPCR."

Kwtara concludes that blocking the effects of G-alpha-i with a targeted drug could be an effective way of protecting the heart from age-related decline.

"Beta-blockers, which have been quite effective in improving the heart function of patients with congestive heart failure, would seem to be a likely candidate," Kwatra said. "That class of drugs is already very well understood and has very few side effects."

By blocking the stimulatory effects of epinephrine and norepinephrine, beta-blockers reduce heart rate and blood pressure. The drugs have been used for 20 years for different ailments, but are primarily used to help treat high blood pressure, chest pain, and heartbeat irregularities.

"The obvious next step, which we are already pursuing, is to see if what we observed in human atria also occurs in ventricles, (lower heart chambers)" Kwatra said. "When we finish those experiments, we should have a much better understanding of the role of G-alpha-i in the aging heart.

Other Duke team members were Jason Kilts, Ph.D., Toshimasa Akazawa, M.D., Habib El-Moalem, Ph.D., Joseph Mathew, M.D., and Mark Newman, M.D.


Story Source:

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


Cite This Page:

Duke University Medical Center. "Protein Implicated In Decline Of Aging Hearts." ScienceDaily. ScienceDaily, 6 October 2003. <www.sciencedaily.com/releases/2003/10/031006064954.htm>.
Duke University Medical Center. (2003, October 6). Protein Implicated In Decline Of Aging Hearts. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2003/10/031006064954.htm
Duke University Medical Center. "Protein Implicated In Decline Of Aging Hearts." ScienceDaily. www.sciencedaily.com/releases/2003/10/031006064954.htm (accessed July 23, 2014).

Share This




More Health & Medicine News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Courts Conflicted Over Healthcare Law

Courts Conflicted Over Healthcare Law

AP (July 22, 2014) Two federal appeals courts issued conflicting rulings Tuesday on the legality of the federally-run healthcare exchange that operates in 36 states. (July 22) Video provided by AP
Powered by NewsLook.com
Why Do People Believe We Only Use 10 Percent Of Our Brains?

Why Do People Believe We Only Use 10 Percent Of Our Brains?

Newsy (July 22, 2014) The new sci-fi thriller "Lucy" is making people question whether we really use all our brainpower. But, as scientists have insisted for years, we do. Video provided by Newsy
Powered by NewsLook.com
Scientists Find New Way To Make Human Platelets

Scientists Find New Way To Make Human Platelets

Newsy (July 22, 2014) Boston scientists have discovered a new way to create fully functioning human platelets using a bioreactor and human stem cells. Video provided by Newsy
Powered by NewsLook.com
Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

Gilead's $1000-a-Pill Drug Could Cure Hep C in HIV-Positive People

TheStreet (July 21, 2014) New research shows Gilead Science's drug Sovaldi helps in curing hepatitis C in those who suffer from HIV. In a medical study, the combination of Gilead's Hep C drug with anti-viral drug Ribavirin cured 76% of HIV-positive patients suffering from the most common hepatitis C strain. Hepatitis C and related complications have been a top cause of death in HIV-positive patients. Typical medication used to treat the disease, including interferon proteins, tended to react badly with HIV drugs. However, Sovaldi's %1,000-a-pill price tag could limit the number of patients able to access the treatment. TheStreet's Keris Lahiff reports from New York. Video provided by TheStreet
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:
from the past week

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