Featured Research

from universities, journals, and other organizations

Mouse With Designer Liver Has Enhanced Glucose Tolerance And Improved Insulin Response

Date:
April 26, 2005
Source:
Burnham Institute
Summary:
A collaborative effort led by The Burnham Institute's Gen-Sheng Feng has created a mouse with improved glucose tolerance and insulin activity in the liver, and generated new findings about insulin-signaling in the liver that could prove useful in understanding the pathogenesis of type 2 diabetes. These results, to be published by Nature Medicine in May, were made available to the scientific community by advance posting online at the journal's website on April 10th.

(La Jolla, CA). A collaborative effort led by The Burnham Institute's Gen-Sheng Feng has created a mouse with improved glucose tolerance and insulin activity in the liver, and generated new findings about insulin-signaling in the liver that could prove useful in understanding the pathogenesis of type 2 diabetes. These results, to be published by Nature Medicine in May, were made available to the scientific community by advance posting online at the journal's website on April 10th.

The liver plays a major role in the uptake of glucose from the bloodstream, its storage, and regulation. Insulin resistance in the liver is a crucial factor in the development of hyperglycemia and hypertriglyceridemia in individuals who suffer type 2-diabetes. Precisely how insulin-initiated signals are modulated in liver cells for glucose uptake and metabolism is unknown.

Gen-Sheng Feng, Ph.D., a Professor in The Burnham Institute's Signal Transduction Program, has focused his efforts on a recently discovered protein called Gab1. Gab1 has a structure that is similar to other proteins in a family known as Insulin Receptor-Signaling, or IRS, proteins. IRS proteins relay signals initiated by insulin receptors and thus play a critical role in insulin regulation inside cells. Biochemical studies on Gab1 in cell cultures suggested that Gab1 is also involved in insulin signaling, but it is not clear how Gab1 acts to control insulin activity in the liver.

To learn how Gab1 functions in the liver, Feng used a highly advanced genetic engineering technology, called tissue-specific gene deletion, to create a mouse in which the Gab1 gene was deleted, or "knocked out", from the liver, and only the liver. Offsprings were termed "LGKO" for liver-Gab1 knockout mice.

Dr. Feng's laboratory, in collaboration with Drs. Andrea Hevener and Jerrold Olefsky at the University of California, San Diego, conducted a thorough investigation of the glucose metabolism and insulin activity in this newly-created mouse strain. Interestingly, the LGKO mice had reduced blood glucose levels and lower levels of serum insulin. The mice retained triglycerides in the liver with a commensurate decrease of circulating triglycerides in the bloodstream. Insulin response to glucose load was diminished in LGKO mice, thus glucose tolerance in the liver was significantly improved in the absence of Gabl protein.

The Feng team conducted biochemical analyses on the LGKO mice, homing in on enzymatic pathways critical to insulin response in cells. Upon stimulation with insulin, they found an elevated level of Akt/PkB kinase, an enzyme needed for insulin signaling, and elevated activity of IRS proteins. There was no activation of another enzyme, Erk, which is elevated in normal liver in reaction to insulin stimulation. Dr. Feng concluded that the function of Gab1 in normal liver cells is to promote signaling in the Erk pathway, which reduces insulin response signals flowing through IRS and Akt proteins.

"We propose that Gab1 acts as a negative regulator on insulin signal strength in the liver," said Dr. Feng. "In this work, by making a new liver-specific gene knockout mouse model, we found a novel balancing mechanism for control of liver insulin signaling. Our observation might be instrumental for understanding better the pathogenesis of type II diabetes and designing anti-diabetes drugs."

Co-authors on this study from Dr. Feng's laboratory were Emilie Bard-Chapeau, Ph.D., and Shinong Long, Ph.D., postdoctoral fellows, and Eric Zhang, graduate student in the Burnham Institute-UCSD's joint graduate training program in Molecular Pathology.

Jerrold Olefsky, Ph.D. and Andrea Hevener, Ph.D. are Professor and Adjunct Associate Professor, respectively, in the Department of Medicine at the University of Calfornia, San Diego.

###

This project was supported by grants from the National Institutes of Health awarded to Drs. Feng, Olefsky, and Hevener. Dr. Feng acknowledges with appreciation the American Diabetes Foundation for support early in his career that has provided a foundation for much of his current research.

The Burnham Institute, founded in 1976, is an independent not-for-profit biomedical research institution dedicated to advancing the frontiers of scientific knowledge and providing the foundation for tomorrow's medical therapies. The Institute is home to three major centers: the original Cancer Center, the Del E. Webb Neuroscience and Aging Center established in 1999, and the Infectious and Inflammatory Disease Center dedicated in 2004. Since 1981, the Institute's Cancer Center has earned the prestigious designation as a Non-comprehensive Cancer Center by the National Cancer Institute. Discoveries by Burnham scientists have contributed to the development of new drugs for Alzheimer's disease, heart disease and several forms of cancer. Today the Burnham Institute employs over 700, including more than 550 scientists. The majority of the Institute's funding derives from federal sources, but private philanthropic support is essential to continuing bold and innovative research. For additional information about the Institute and ways to support the research efforts of the Institute, visit www.burnham.org.


Story Source:

The above story is based on materials provided by Burnham Institute. Note: Materials may be edited for content and length.


Cite This Page:

Burnham Institute. "Mouse With Designer Liver Has Enhanced Glucose Tolerance And Improved Insulin Response." ScienceDaily. ScienceDaily, 26 April 2005. <www.sciencedaily.com/releases/2005/04/050425205607.htm>.
Burnham Institute. (2005, April 26). Mouse With Designer Liver Has Enhanced Glucose Tolerance And Improved Insulin Response. ScienceDaily. Retrieved April 17, 2014 from www.sciencedaily.com/releases/2005/04/050425205607.htm
Burnham Institute. "Mouse With Designer Liver Has Enhanced Glucose Tolerance And Improved Insulin Response." ScienceDaily. www.sciencedaily.com/releases/2005/04/050425205607.htm (accessed April 17, 2014).

Share This



More Health & Medicine News

Thursday, April 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Is Apathy A Sign Of A Shrinking Brain?

Is Apathy A Sign Of A Shrinking Brain?

Newsy (Apr. 17, 2014) A recent study links apathetic feelings to a smaller brain. Researchers say the results indicate a need for apathy screening for at-risk seniors. Video provided by Newsy
Powered by NewsLook.com
Could Even Casual Marijuana Use Alter Your Brain?

Could Even Casual Marijuana Use Alter Your Brain?

Newsy (Apr. 16, 2014) A new study conducted by researchers at Northwestern and Harvard suggests even casual marijuana use can alter your brain. Video provided by Newsy
Powered by NewsLook.com
Thousands Of Vials Of SARS Virus Go Missing

Thousands Of Vials Of SARS Virus Go Missing

Newsy (Apr. 16, 2014) A research institute in Paris somehow misplaced more than 2,000 vials of the deadly SARS virus. Video provided by Newsy
Powered by NewsLook.com
Formerly Conjoined Twins Released From Dallas Hospital

Formerly Conjoined Twins Released From Dallas Hospital

Newsy (Apr. 16, 2014) Conjoined twins Emmett and Owen Ezell were separated by doctors in August. Now, nearly nine months later, they're being released from the hospital. Video provided by Newsy
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