Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists find unsuspected molecular link between obesity and insulin resistance

22.07.2010
Discovery raises possibility of safer, more selective diabetes drugs

A new understanding of insulin resistance and the action of diabetes drugs such as Avandia and Actos could pave the way for improved medications that are more selective and safer, say scientists from Dana-Farber Cancer Institute and The Scripps Research Institute.

"Our findings strongly suggest that good and bad effects of these drugs can be separated by designing second-generation drugs that focus on the newly uncovered mechanism," said Bruce Spiegelman, PhD, of Dana-Farber, senior author on a report appearing in the July 22 issue of Nature.

Avandia and Actos, known generically as rosiglitazone and pioglitazone, are widely used to counteract the obesity-related abnormalities in insulin response that lead to diabetes. The drugs act on a master regulatory protein called PPAR-gamma, primarily in fat cells, which governs genes involved in the body's response to insulin.

Obesity resulting from a high-fat diet alters the function of PPAR-gamma and disrupts the expression of those insulin response genes, including adipsin and adiponectin. Avandia and Actos work by binding to PPAR-gamma and reversing the gene expression changes.

The drugs were believed to work by stimulating or "agonizing" the PPAR-gamma receptor, causing it to rev up some genes and dampen the activity of others.

In the Nature report, however, the researchers say they have identified "an entirely new and surprising mechanism by which PPAR-gamma can control whole-body insulin sensitivity." It is mainly through this mechanism, they found, that the diabetes drugs counteract insulin resistance – not their agonist effect on PPAR-gamma. Moreover, they say, agonism of PPAR-gamma may be largely responsible for the harmful drug side effects.

The newly identified pathway linking obesity and insulin response involves cdk5, a protein kinase, or molecular "switch." When cdk5 is activated by the development of obesity in mice, it causes a chemical change in PPAR-gamma called phosphorylation. In contrast to agonism of PPAR-gamma, phosphorylation has a narrow effect, disrupting a smaller set of genes that lead to insulin resistance.

In addition to agonizing PPAR-gamma, Avandia and Actos also block the phosphorylation of PPAR-gamma by cdk5. It's this latter effect that accounts for most of the drugs' anti-diabetic benefits, the authors contend. "Agonism may not be therapeutically necessary and likely results in a lot of the toxicities," Spiegelman said.

The strength of various drugs' agonist effects on PPAR-gamma doesn't correlate with how well they work, the researchers observe; instead, it is their ability to block cdk5 phosphorylation that counts. In support of this assertion, the paper describes the researchers' findings from patients treated with Avandia in a German clinical trial. It showed that improvements in insulin sensitivity were tightly correlated with decreased phosphorylation of PPAR-gamma.

"I think this is a really important finding, and potentially very timely in light of the current discussions about Avandia," commented Jeffrey Flier, MD, Dean of the Harvard Medical School, a leading researcher in obesity, insulin resistance, and diabetes.

"It may motivate pharmaceutical companies to take another look at compounds acting through PPAR-gamma that were taken to various stages of development but put on hold because they did not demonstrate strong agonism of PPAR-gamma," Flier said. "People may have been focusing on the wrong outcomes."

Avandia and Actos belong to a relatively new class of compounds called thiazolidinediones, the first medications that can reverse insulin resistance. They have been widely used to treat Type 2 diabetes since being approved in 1999. However, in recent years they have been linked in some patients to heart attacks, heart failure, and strokes. Thousands of lawsuits have been filed against the maker of Avandia, and the US Food and Drug Administration is currently weighing whether it should be taken off the market.

The research was supported by grants from the National Institutes of Health.

The paper's first author is Jang-Hyun Choi, PhD, of Dana-Farber.

The co-authors are Alexander S. Banks, PhD, Jennifer L. Estall, PhD, Shingo Kajimura, PhD, Pontus Bostrom, MD, PhD, Dina Laznik, Jorge L. Ruas, PharmD, PhD, Dana-Farber; Patrick R. Griffin, PhD, Michael J. Chalmers, PhD, and Theodore M. Kamenecka, PhD, Scripps Research Institute, Jupiter, Fla.; and Matthias Bluher, MD, University of Leipzig, Germany.

Dana-Farber Cancer Institute (www.dana-farber.org) is a principal teaching affiliate of the Harvard Medical School and is among the leading cancer research and care centers in the United States. It is a founding member of the Dana-Farber/Harvard Cancer Center (DF/HCC), designated a comprehensive cancer center by the National Cancer Institute. It provides adult cancer care with Brigham and Women's Hospital as Dana-Farber/Brigham and Women's Cancer Center and it provides pediatric care with Children's Hospital Boston as Dana-Farber/Children's Hospital Cancer Center. Dana-Farber is the top ranked cancer center in New England, according to U.S. News & World Report, and one of the largest recipients among independent hospitals of National Cancer Institute and National Institutes of Health grant funding.

Teresa Herbert | EurekAlert!
Further information:
http://www.dfci.harvard.edu

More articles from Life Sciences:

nachricht Toward a 'smart' patch that automatically delivers insulin when needed
18.01.2017 | American Chemical Society

nachricht 127 at one blow...
18.01.2017 | Stiftung Zoologisches Forschungsmuseum Alexander Koenig, Leibniz-Institut für Biodiversität der Tiere

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

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...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

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

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>