Leptin's long-distance call to the pancreas

Dec 22, 2008
More insulin-positive cells (brown) occur in mice lacking leptin-making fat cells (left) than in control mice (right). Image from: Hinoi, E., et al. 2008. J. Cell Biol. doi:10.1083/jcb.200809113.

Rube Goldberg—the cartoonist who devised complex machines for simple tasks—would have smiled at one of leptin's mechanisms for curbing insulin release. As Hinoi et al. show, the fat-derived hormone enlists the sympathetic nervous system to prevent bone-making cells from releasing a molecule that prods the pancreas to discharge insulin.

The study will appear online December 22, 2008 (www.jcb.org) and in the December 29, 2008 print issue of The Journal of Cell Biology (JCB).

In the fight against obesity and diabetes, leptin is one of the good guys. Mice lacking the hormone become corpulent, and their sky-high insulin levels eventually lead to diabetes. Leptin can curtail insulin release directly. But there's also a back-door route that researchers are still trying to piece together. Scientists knew that leptin nudges osteoblasts, cells known for building bone but that also manufacture osteocalcin, a protein that stimulates insulin release. Hinoi et al. tested whether leptin acts on the pancreas through osteocalcin.

Leptin channels many of its effects through the nervous system. The team thus tested whether the hormone relied on the sympathetic nervous system, the branch that pumps out adrenaline during emergencies but at other times emits a hormonal trickle to maintain a low level of stimulation. This baseline activity was lower in mice lacking the leptin receptor, indicating a connection between leptin and the sympathetic nervous system. When that connection was broken by deleting the adrenaline receptor from mice osteoblasts, insulin levels shot up.

The researchers then dosed mice with a sympathetic stimulator. Rodents lacking leptin or the adrenaline receptor on their osteoblasts turned out normal amounts of osteocalcin, but much of it was in an inert form. That result suggests leptin affects insulin release by indirectly inactivating osteocalcin. The work boosts researchers' hopes of using osteocalcin to treat diabetes—a possibility some drug companies have already started to investigate.

Citation: Hinoi, E., et al. 2008. J. Cell Biol. doi:10.1083/jcb.200809113

Source: Rockefeller University

Explore further: Dwindling wind may tip predator-prey balance

add to favorites email to friend print save as pdf

Related Stories

Enzyme Crucial to Insulin Resistance Found in Brain

Sep 14, 2009

An enzyme known to cause insulin resistance in muscle is also located in the brain and has a similar function there, a research team that includes a University of Cincinnati scientist has found.

Dessert on your mind? Your muscles may be getting the message

Dec 01, 2009

Even the anticipation of sweets may cause our muscles to start taking up more blood sugar, say researchers reporting in the December issue of Cell Metabolism. That message is delivered via neurons in the brain's hypothalamus contai ...

Too many calories send the brain off kilter

Oct 02, 2008

An overload of calories throws critical portions of the brain out of whack, reveals a study in the October 3rd issue of the journal Cell, a Cell Press publication. That response in the brain's hypothalamus—the "headquarters" for ma ...

Your brain and hormones may conspire to make you fat

Apr 30, 2007

Why do some people get fat even when they eat relatively little? What creates that irresistible urge for a bag of potato chips or a hunk of chocolate cake, as opposed to a nice crisp apple? Can food urges be irresistible?

Recommended for you

Dwindling wind may tip predator-prey balance

Sep 19, 2014

Bent and tossed by the wind, a field of soybean plants presents a challenge for an Asian lady beetle on the hunt for aphids. But what if the air—and the soybeans—were still?

Environmental pollutants make worms susceptible to cold

Sep 19, 2014

Some pollutants are more harmful in a cold climate than in a hot, because they affect the temperature sensitivity of certain organisms. Now researchers from Danish universities have demonstrated how this ...

Research helps steer mites from bees

Sep 19, 2014

A Simon Fraser University chemistry professor has found a way to sway mites from their damaging effects on bees that care and feed the all-important queen bee.

User comments : 0