An improved ability to consume fat stores is something that many people dream of. Burning fat can help make weight loss easier, leading to better health. Weight control is normally regulated by the hormone leptin, which is produced by fat cells to send the "I'm full" signal to the brain that gets us to stop eating . In obese individuals, however, leptin stops working, meaning their brain never gets the signal that they’re full and they consume more food then they need. Overcoming this defect in leptin signaling is critical to these individuals to help them lose weight.
In the work by Zeng et al.  the link between the sympathetic nervous system, which controls the fight or flight response, and lipolysis, the breakdown of fat into fatty acids and glycerol which can be used as energy sources, was investigated. Before this work it was unknown if the sympathetic nervous system even entered adipose tissue where fat is stored. The researchers proved that sympathetic nerve endings did in fact enter the adipose tissue near the kidneys of mice, called the inguinal fat pad. Using a mouse line that allowed gene insertion specifically into sympathetic nerves, the researchers tested if activation of these nerves affected adipose tissue. This was done by inserting a channelrhodopsin (ChR2) gene into the sympathetic nerves of the mice; ChR2 is a light-activated ion channel, that when exposed to blue light would make the nerves signal. Mice had optic fibers inserted in them near the inguinal fat pads, which when activated would in turn activate the ChR2ion channels in the vicinity. Activation of the ion channels, and subsequently the sympathetic nervous system through these optic fibers, as well as local treatment with leptin itself, was found to decrease fat pad size. Leptin treatment was ineffective however if the nerves were damaged, indicating that the signaling from the nerves was necessary to make leptin work.
This research showed that the breakdown of fat could be controlled through the combined actions of leptin, a hunger control hormone, and the sympathetic nervous system. This research could help individuals who experience leptin resistance. If the sympathetic nervous system can be activated in fat tissue, the effects of leptin may be restored, helping these individuals lose weight.