Researchers have found that a bone growth protein, known as BMP-7, also aids the growth of brown (or “good”) fat that helps fight obesity.
“Obesity is occurring at epidemic rates in the U.S. and worldwide and that impacts the risk and prognosis of many diseases,” said Yu-Hua Tseng, Ph.D. an Assistant Investigator in the Joslin Section on Obesity and Hormone Action and lead author of the paper published in the August 21 issue of Nature. “We hope this study can be translated into applications to help treat or prevent obesity.”
Dr. Teng cited obesity as a major risk factor for type 2 diabetes, and its close relationship to the metabolic syndrome, a group of medical problems associated with insulin resistance that can increase the risk of atherosclerosis.
Dr. Teng states that there are 2 main types of fat cells, white and brown. In laboratory studies of mouse cells, she and her colleagues found that a bone-producing protein called BMP-7 drives precursor cells giving rise to mature brown fat cells.
“White fat cells are the ‘conventional’ form of fat designed to store energy. By contrast, the main role of brown fat is to burn calories by generating heat. Brown fat cells largely disappear by adulthood in humans, but their precursors still remain in the body,” Tseng explained.
An earlier (2005) Joslin study by Dr. Teng and colleagues discovered genes that control the creation of the precursor cells of brown fat. A later (2007) Joslin study by C. Ronald Kahn, M.D., head of the Joslin Section on Obesity and Hormone Action and also a co-author of the current Nature study, found clusters of brown fat cells dispersed between bundles of muscle fibers in an obesity-resistant strain of mice.
The study identified BMP-7 as the protein capable of inducing the formation and function of brown fat cells.Delivery of BMP-7 into mice using adenovirus as a vector resulted in an increase in the development of brown fat tissue. In one of the experiments, the mice that developed brown fat tissue gained less weight than those that did not. In another experiment, mice that received injections of progenitor cells—similar to stem cells—that had been pre-treated with BMP-7 also developed additional brown fat tissue.
The purpose of the study was to determine what controls the development of fat depots, a central question in adipocyte biology. BMPs are a family of proteins known to regulate organ formation during embryonic development. Dr. Teng and associates suggested that different members of BMPs determine brown versus white fat cell fate. Scientists hope that improved knowledge of fat development will lead to new drugs or therapeutic approaches to fight obesity.
“Diet and exercise are still the best approaches for weight reduction in the general population,” Tseng said. “However, for people who are genetically predisposed to obesity, these approaches may have very little effect.” As we learn more about the controls of brown fat development, medical interventions to increase energy expenditure by brown fat inducing agents, such as BMP-7, may provide hope to these individuals in losing weight and preventing the metabolic disorders associated with obesity,” she said.
Source: Nature, August 21, 2008