Obesity: You Get Fat Because Your Brain Says So
Obesity affects more than a third of (or 78.6 million) adults in the United States.
Obesity is a huge public health concern, not least because it is associated with poor mental health and many other serious medical problems. These include some of the leading causes of death in the U.S. and the rest of the world, such as diabetes, stroke, heart disease, and some cancers.
The main drivers of the epidemic are largely non-genetic, such as the combination of ready access to an unlimited supply of calorie-rich food and sedentary lifestyles. It shows the important role that the antenna-like structures can play in brain signaling.
Obesity: Latest Research Results
Researchers studying obesity have discovered that antenna-like structures on brain cells that form part of the body’s hunger circuit seem to play a key role in appetite regulation.
Most single-gene causes of severe obesity are due to gene alterations in a hunger circuit that involves leptin, a signaling hormone, that is released by fat cells.
The circuit is a network of nerve cells in the hypothalamus area of the brain that helps to keep weight stable by adjusting appetite and energy usage depending on leptin levels.
Mutations in the gene that codes for leptin, or in genes involved in monitoring and responding to the protein, can lead to failure to detect when the body has a sufficient amount of fat. This can happen in mice and humans, causing them to keep eating as if they are starving.
Obesity: Locations of appetite regulating signals
In a further set of experiments, the researchers found that after blocking ADCY3 in the mice, the animals increased their food intake significantly and started to become obese.
The researchers concluded that proteins ADCY3 and MC4R work together in the primary cilia of the leptin-detecting neurons. Together they detect that body fat levels are increasing, which, in turn, reduces appetite.
Mice engineered to have the version of the gene that is linked to severe obesity in humans did not have the MC4R protein in those cilia.
These findings made the team wonder whether these primary cilia on the hypothalamic neurons were the main location for the appetite-regulating function of the leptin hunger circuit.
Recent discoveries also have revealed that another protein called adenylyl cyclase 3 (ADCY3) is also linked to obesity, and that it also concentrates in primary cilia. ADCY3 is known to link up with MC4R when it sends signals.
While this research is new, it does suggest that obesity is controlled by genetics and by the absence of certain proteins that regulate body weight and food intake. So, in some cases, aperson may have no control over how fat they are.