Where Fat Comes From

Researchers have found that most fat cells arise from cells in the walls of blood vessels in fat tissue. This insight may lead to new approaches to prevent and treat obesity.

White adipose, or fat, tissue plays a role in regulating our metabolism, reproduction and life spans. Fat cells form throughout life, but despite scientists' growing understanding of the roles these cells play in the body, little has been known about how they develop.

A research team at the University of Texas Southwestern Medical Center, led by Dr. Jonathan M. Graff, set out to discover where fat cells, or adipocytes, come from. Their work, which was funded by NIH's National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), appeared in the October 24, 2008, issue of Science.

The researchers created transgenic mice, putting production of a marker protein under the control of a known regulator of fat formation. This allowed them to track when adipocytes form. By looking at adipose tissue formation, the researchers found that most adipocytes descend from cells that are committed to become adipocytes either prenatally or early after birth.

The researchers used proteins expressed on cell surfaces to identify these precursor cells from adipose tissues. A gene expression analysis revealed that the cells have a unique molecular signature that could be used to track and identify them.

To find out where these cells come from, the researchers isolated sections of adipose tissue. They found that most of the adipocyte precursors were in the walls of blood vessels. Not all the cells within blood vessels were adipocyte precursors, and not all the blood vessels had them. Blood vessels in other tissues didn't harbor the cells, either.

This research shows that fat cells arise from the network of blood vessels in adipose tissue. The interplay between this network and adipocytes may provide potential targets for therapies to treat obesity. That could have implications for obesity-related diseases, such as diabetes, heart disease and some cancers.

— by Harrison Wein, Ph.D.