September 8, 2011

The Anti-Obesity Effect

(Ivanhoe Newswire) — Interior design may have a new meaning. Scientists have discovered a biological switch that gives energy-storing white fat the characteristics of energy-burning brown fat.

The findings show the transformation occurs when an environment is designed with a variety of social and physical challenges included. The discovery could lead to new strategies for treating obesity.

“One of the holy grails of obesity therapy is to understand how to switch white fat to brown fat, and this study describes a new way to do exactly that,” study leader and researcher Dr. Matthew J. During was quoted as saying.

The animal study by researchers at The Ohio State University Medical Center used 15-20 mice housed in large containers designed with “enriched environments” including running wheels, tunnels, huts, wood toys, a maze, and nesting material, in addition to unlimited food and water. Control mice were housed in groups of five in smaller laboratory containers without toys, but also with unlimited food and water.

The enriched environment stimulates production of a protein called brain-derived neurotrophic factor (BDNF), increasing sympathetic nerve output to white fat, causing the “browning” of white fat and the burning of stored energy. The normal function of BDNF is to help control food intake and energy balance.

Key findings of the study showed enriched animals had a significant reduction in abdominal white fat mass, up to 49 percent less than the controls. In addition, enriched animals gained 29 percent less weight than control mice and remained lean when fed a high fat diet. More importantly, exercise alone did not account for the changes. The enriched animals also had a higher body temperature, suggesting that greater energy output led to the resistance to obesity.

Overall, the study shows that environmental enrichment has an anti-obesity effect that involves the transformation of white fat to brown fat. The change is due to the activation of a nerve, and biochemical pathway that begins in the part of the brain involved in energy balance, the hypothalamus, and ends in white fat cells. The pathway, called the hypothalamic-adipocyte axis, also induces brown-fat-like cells within masses of white fat.

“Up to now the only known approach to inducing brown fat has been through exposure to chronic cold. Our research reveals a novel way of doing this without cold exposure. We show that animals living in an enriched environment become lean and resistant to diet-induced obesity, even in the presence of unlimited food,” lead and corresponding author Dr. Lei Cao was quoted as saying.
Next, Dr. During, Dr. Cao and their colleagues plan to identify which components of environmental enrichment — sensory, cognitive, motor, or social stimulation are essential to the browning effect.

SOURCE: Cell Metabolism