Researchers in Sweden believe they have discovered a previously unidentified body fat regulatory system. The mechanism senses excessive body weight much like bathroom scales, signaling the brain to reduce food intake. If confirmed, this will be the first new fat regulatory mechanism to be discovered in over two decades.
"Quite simply, we have found support for the existence of internal bathroom scales," explains lead author on the study, John-Olov Jansson. "The weight of the body is registered in the lower extremities. If the body weight tends to increase, a signal is sent to the brain to decrease food intake and keep the body weight constant."
The team initially discovered the mechanism after implanting a series of animal models with weight capsules. After two weeks, compared to a control group, the animals with the extra weight had reduced their food intake and biological fat mass, as well as displaying an increase in glucose tolerance.
In order to understand how this body weight mechanism could be working the researchers looked at osteocytes, a common cell type that resides inside bone tissue. Previous research had already suggested that osteocytes not only have the ability to sense bone strain but can also affect energy and glucose metabolism.
The researchers created a transgenic mouse model with depleted osteocytes and recreated the weight capsule experiments. The previously observed effects of decreased food intake and weight reduction did not appear in the mice with depleted osteocytes, leading the team to propose that the internal weight sensor mechanism is fundamentally controlled by osteocytes in weight-bearing bones.
About 23 years ago, a hormone called leptin was discovered to be a key regulator of the body's metabolism. Anti-obesity research over the last couple of decades has focused on understanding how this hormone controls our appetite and fat metabolism. This new study reveals a previously undiscovered mechanism that operates to regulate fat mass entirely independently of leptin.
"The mechanism that we have now identified regulates body fat mass independently of leptin, and it's possible that leptin combined with activation of the internal body scales can become an effective treatment for obesity," says Professor Claes Ohlsson.
One fascinating proposition that stems from this new research is that the discovery could potentially explain a frequently observed correlation between the time a person spends sitting and increases in metabolic diseases such as obesity and diabetes. In the study the researchers conclude, "We propose that much sitting time results in decreased loading of osteocytes in the weight-bearing long bones and, thereby, the homeostatic regulation of body weight does not activate its afferent signal to the brain, resulting in obesity."
Despite the research being clearly still in its nascent stages, this is a compelling hypothesis that could point to some entirely new ways to treat obesity and other associated diseases.
The research was published in the journal Proceedings of the National Academy of Sciences of the United States of America.
