Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fat-cell hormone linked to kidney disease

23.04.2008
Reduced levels of a hormone produced by fat cells and linked to the development of insulin resistance may also be related to a higher risk of kidney disease, according to a study led by researchers at the University of California, San Diego School of Medicine and Thomas Jefferson University. Their study, to be published in the Journal of Clinical Investigation on April 22, could point the way to drug therapies that can protect renal and cardiac function in patients with obesity.

The new findings show that the hormone, adiponectin, produced by fat cells, circulates in the blood and acts to both suppress inflammation – known to be a contributor to diabetes and cardiovascular disease – and to reduce protein in the urine.

“A deficiency in adiponectin could be the major reason why obese patients develop the initial signs of kidney disease,” said principal investigator Kumar Sharma, M.D., F.A.H.A., professor of medicine and Director of Translational Research in Kidney Disease at UC San Diego’s School of Medicine. He added that an elevated level of protein in the urine, termed albuminuria, is often seen with obesity. Albuminuria is an indicator of kidney disease and an important risk factor for cardiovascular disease. “At present, the connections between the kidney and the cardiovascular system are not clear. A better understanding of the relationships between the kidney, the cardiovascular system and obesity will be of major benefit in treating these common public health problems at an early stage.”

“The findings in the kidney are consistent with beneficial effects we reported for adiponectin in the microvasculature, in which it reduces oxidative stress and inflammatory responses,” said co-corresponding author Barry J. Goldstein, M.D., Ph.D., professor and director of the Division of Endocrinology, Diabetes and Metabolic Diseases at Thomas Jefferson University in Philadelphia. “In this setting, adiponectin suppresses the adverse effects of high glucose, which implies that it may eventually be shown to serve a protective role in patients with diabetes as well as those with obesity.”

A network of fine capillaries in the kidney acts as a filter to prevent proteins in the blood from being secreted into the urine. This filter is made up of three components, one of which – the podocyte cell – serves to regulate albuminuria.

“We discovered that the hormone adiponectin, produced by fat cells, is directly linked to the healthy function of podocytes,” said Sharma. In a study of obese patients without obvious diabetes or kidney disease, the research team found that when blood adiponectin levels were low, there was a direct correlation to elevated albumin protein levels in the urine.

Sharma explained that levels of adiponectin hormone are sometimes reduced in obesity. With reduced levels of the hormone, there is an associated loss of the protective effect of adiponectin in the podocytes, leading to an overproduction of inflammatory molecules. In addition, the dysfunctional podocyte allows albumin to enter the urine and may contribute to the overall inflammation occurring in the body.

To explore whether the lower hormone levels were simply an indication of albuminuria or played a causative role in its development, the scientists studied a knockout model of a mouse lacking the adiponectin hormone, and discovered that these mice had high urine albumin levels. Treatment of the mice with adiponectin brought the albuminuria back to normal levels.

They also focused on a receptor on the podocyte cell surface that is associated with a molecular signaling pathway, the AMP kinase enzyme (AMPK), which acts as an energy sensor for the cell and is activated by adiponectin. The research showed that if AMPK is stimulated, either chemically or by introducing adiponectin, the filter works normally to keep albumin from leaking out of the blood and into the urine. However, when there is a lack of adiponectin, the resulting decrease in AMPK activity contributes to dysfunction of the filter. Therefore, the researchers concluded that deficiency of adiponectin is indeed causative to albuminuria.

“We know there are certain medicines that stimulate the AMPK pathway, including adiponectin and a drug called Metformin, which is commonly given to patients with diabetes,” said Sharma. “This study suggests that using the hormone adiponectin, Metformin or other therapies could work to protect kidney function in patients who are obese, even before they have diabetes.”

Last, the researchers looked at markers of inflammation in the kidney that may be regulated by adiponectin, and found that the podocyte also produces an inflammatory enzyme called NOX4 which is increased in the absence of the hormone.

“When you don’t have the hormone there to suppress it, NOX4 enzyme is stimulated and can potentially contribute to the inflammation going on in the kidney and perhaps elsewhere in the body,” said Sharma. Sharma added that replacing the hormone adiponectin in obese patients might work preventively to help the podocytes do their job, thus preventing kidney damage and inflammation.

Debra Kain | EurekAlert!
Further information:
http://www.ucsd.edu

More articles from Health and Medicine:

nachricht Laser activated gold pyramids could deliver drugs, DNA into cells without harm
24.03.2017 | Harvard John A. Paulson School of Engineering and Applied Sciences

nachricht What does congenital Zika syndrome look like?
24.03.2017 | University of California - San Diego

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>