Researchers have mapped the complex nerve pathways that supply brown adipose tissue, otherwise known as ‘brown fat'. It’s the first step in developing a way of stimulating the nerves to burn fat as a novel treatment for obesity and related metabolic conditions.
Since it was first discovered in 1972, brown adipose tissue (BAT), or ‘brown fat’, has been the subject of much research, much of it to do with the effect BAT has on metabolism. Whereas white fat is designed for energy storage, BAT helps burn calories by creating heat right before your body starts to shiver (thermogenesis).
In adults, the largest deposits of BAT are found in the neck and supraclavicular area, the area above the collarbone. In a new study, researchers led by UCLA mapped out the nerve pathways that supply supraclavicular brown fat pad.
“We know from previous literature that the sympathetic nervous system is the main ‘on switch’ for BAT activity,” said Preethi Srikanthan, corresponding author of the study. “However, the sympathetic nervous system is also responsible for many other stimulatory effects on organs such as the heart and gut. Finding a way to increase activity of BAT alone has been challenging, so finding out the path these sympathetic nerves take to BAT will allow us to explore ways of using nerve to provide a very specific stimulus to activate BAT.”
The researchers carefully dissected the necks of eight cadavers to trace the sympathetic nerves that terminated in the supraclavicular fat pad. They found multiple sympathetic pathways innervating the area, including from the third and fourth cervical nerves and the cervical sympathetic plexus, a network of nerve fibers that innervates some of the structures in the neck and chest. They also found that the activity of BAT had changed in clinical cases where neck pathology, such as an increase in BAT temperature following tumor removal, had caused a change in the nerves.
The researchers are hopeful they can use their discovery to find a way to coax BAT into producing a constant source of fat-burning heat.
“There is a need to find long-term solutions for obesity, and while we are lucky to have effective drugs such as Wegovy and Mounjaro, people need to take them long-term for weight loss,” Srikanthan said.
While Wegovy (semaglutide) is FDA-approved for obesity, Mounjaro (tirzepatide) is approved for type 2 diabetes but used off-label for obesity. Its manufacturer is seeking FDA approval for the drug to be covered for weight management.
“There is literature suggesting – and we are doing another study to confirm it – that these drugs act by stimulating BAT,” said Srikanthan. “By identifying the nerve pathways supplying BAT we hope to explore methods of chronically stimulating nerves to BAT and hopefully achieving similar therapeutic outcomes of weight loss.”
The researchers acknowledge the limitations of their study, namely the small number of cadavers dissected and their advanced age, which causes them to have a smaller amount of BAT compared to younger bodies.
The study was published in the journal PLOS One.
Source: UCLA Health