Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Heart failure wall stress drops 38% with moderate thyroid hormone therapy

13.05.2005


Unexpected cell shape change raises possibility of novel therapeutic approach; Further animal study urged before human testing



Not only is low thyroid function very common in congestive heart failure, it also indicates a reduced likelihood of recovery, and an increased chance of death.
But based on earlier work showing that whatever leads to heart failure it is always preceded by changes in the heart cells, a new study demonstrates that a moderate dose of thyroid hormones (TH) over 30 days "normalizes" the shape of the cardiac cells (myocytes) and reduces stress on the heart’s wall nearly 40%. "As patients move toward heart failure, the myocytes become longer and flatter, and the wall stress worsens," according to the head of the laboratory where the research was performed. "But moderate TH therapy selectively targeted myocyte cross-sectional shape and modified it in a positive way.

This is the first clue on what might be a novel therapeutic approach to heart failure because of the return to a more normal heart cell shape," according to A. Martin Gerdes, director of the Cardiovascular Research Institute, University of South Dakota.



The study, entitled "Thyroid hormones induce unique and potentially beneficial changes in cardiac myocyte shape in hypertensive rats near heart failure," appears in the May issue of the American Journal of Physiology-Heart and Circulatory Physiology, published by the American Physiological Society. The research was conducted by Tracy A. Thomas, James A. Kuzman, Brent E. Anderson, Susan M. K. Andersen, Evelyn H. Schlenker, Maurice S. Holder and A. Martin Gerdes.

More animal testing needed before move to humans

Based on positive preliminary findings, the University of South Dakota-Florida A&M University research paper reports that moderate TH positively affected heart remodeling and reduced wall stress in ways warranting further study. However the authors warn that since the mechanism of thyroid hormone influence on diseased hearts isn’t known, continuous TH therapy could endanger heart failure patients, particularly in accidental overdose.

In the U.S. alone, heart failure contributes to or causes about 300,000 deaths each year, according to the National Heart, Lung, and Blood Institute. The unit of the National Institutes of Health estimates that about 5 million people in the U. S. have heart failure and the number is growing. Each year, 550,000 people are diagnosed for the first time.

Unique cardiac cell re-shaping reduced heart wall stress 38%

"This is the first study to look at the implications of thyroid hormone therapy on hypertensive heart failure," Gerdes said. There is "an abundance of evidence that thyroid dysfunction contributes to heart failure," Gerdes noted, "but this study showed that a moderate TH dosage reduced wall stress 38% without affecting blood pressure."

The paper said the effect came about because the TH "produced a unique, never-before-observed pattern of myocyte remodeling." This is particularly important, Gerdes said, because no matter what the underlying cause of heart failure in humans, the last phase in heart failure – progression to dilatation – is always accompanied by elongation of heart muscle cells (myocytes), without concomitant cell widening.

The paper notes that "it isn’t clear at this time whether the critical defect in myocyte remodeling in progression to congestive heart failure is due solely to excessive myocyte lengthening or to impaired transverse growth. It is possible that myocytes are responding normally to increased preload by adding new series sarcomeres, whereas the normal check on this system -- balanced myocyte transverse growth -- is where the true dysfunction lies."

However Gerdes warned since "this is the first study to disclose these positive effects with TH, we don’t yet have enough information to do this intelligently in humans. Care should be taken in administering TH to humans for heart disease since there is so little information available from animal studies."

The current study said that the "most interesting effects were on the left ventricular myocyte shape…and these changes correlated beautifully with echocardiogram-derived measurements of chamber diameter and wall thickness. Additionally, the anatomical changes led to a surprising reduction in left ventricular systolic wall stress despite the presence of sustained hypertension."

Next steps

  • Since there appears to be such a strong link between low thyroid function and heart failure, more animal studies need to focus on this entire subject. "There is a strong likelihood that improvements in human patient outcome may occur if we have the proper scientific basis on which to proceed in an intelligent manner," Gerdes said.
  • Future animal studies also should try to demonstrate that TH treatment can actually reduce mortality in heart failure, since this is the most important question from a clinical standpoint, Gerdes said.
  • An area where additional work is merited, the paper says, is to uncover the signaling mechanisms by which the THs alter myocyte shape, which aren’t known. If the impaired thickening of myocytes in progression to chamber dilatation and failure is related to thyroid dysfunction, which is common in heart failure patients, it is possible that treatment may help arrest progressive chamber dilatation.
  • Interestingly, there was no change in myocyte shape with the low-dose TH despite reversal of the myosin-isoform abnormality, which is a marker of fetal-gene program (FGP) reactivation, the paper notes. "This suggests that signaling related to myocyte growth could be independent of changes in the FGP" -- another potential area for follow up.

Mayer Resnick | EurekAlert!
Further information:
http://www.the-aps.org

More articles from Studies and Analyses:

nachricht The Great Unknown: Risk-Taking Behavior in Adolescents
19.01.2017 | Max-Planck-Institut für Bildungsforschung

nachricht A sudden drop in outdoor temperature increases the risk of respiratory infections
11.01.2017 | University of Gothenburg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland

19.01.2017 | Earth Sciences

Not of Divided Mind

19.01.2017 | Life Sciences

Molecule flash mob

19.01.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>