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 Smart Data Transformation – Surfing the Big Wave
02.12.2016 | Fraunhofer-Institut für Angewandte Informationstechnik FIT

nachricht Climate change could outpace EPA Lake Champlain protections
18.11.2016 | University of Vermont

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: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

IHP presents the fastest silicon-based transistor in the world

05.12.2016 | Power and Electrical Engineering

InLight study: insights into chemical processes using light

05.12.2016 | Materials Sciences

High-precision magnetic field sensing

05.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>