Oct. 17, 2023 — A process your body uses to remain warm in cool weather could sooner or later result in recent treatments for obesity.
Scientists have mapped for the primary time the precise neural pathways that activate brown fat or brown adipose tissue (BAT), a special fat that produces heat. Low temperatures stimulate brown fat, helping the body maintain its temperature and burn calories in the method.
“It has long been speculated that activating this type of fat could be useful in the treatment of obesity and related metabolic diseases,” said Dr. Preethi Srikanthan, an endocrinologist and professor of medication who oversaw the study research on the UCLA School of Medicine. “The challenge was to seek out a technique to selectively stimulate it [it].”
Brown fat is different from the fat typically associated with obesity: the kind that accumulates around the stomach, hips, and thighs. That is White fat. White fat stores energy; Brown fat burns it. That's because brown fat cells have more mitochondria, a part of the cell that produces energy.
After Srikanthan and her team dissected the necks of eight human cadavers, they traced the branches of the sympathetic nerve within the fat pad above the collarbone – where the most important deposit of brown fat in adults is stored. They stained the nerves, took samples and checked out them under a microscope.
They found that nerves that result in brown fat arise from the third and fourth cervical nerves of the spine, nerves that sense parts of the face, head, neck and shoulders and help control the diaphragm.
In a previous case study, damage to those nerves appeared to forestall a chemical tracer from reaching brown fat. The evidence suggests that altering this nerve supply could alter brown fat activity, potentially resulting in recent treatments for obesity and metabolic diseases reminiscent of type 2 diabetes, Srikanthan said.
A possible mechanism for Ozempic?
Brown fat has already been linked to at the least one breakthrough within the treatment of obesity. Some evidence suggests that popular medications reminiscent of semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro) may affect brown fat activity. These belong to a category of medication often called glucagon-like peptide-1 (GLP-1) receptor agonists. They work by mimicking the hormone GLP-1, which is released within the gut and brain in response to consumption of glucose (sugary foods or drinks).
“GLP-1 agonists have been shown to increase [brown fat] activity in rodents and humans, but probably indirectly through activation of specific regions in the brain,” explained Varman Samuel, MD, PhD, associate professor of medication at Yale School of Medicine and chief of endocrinology on the VA Connecticut Healthcare System.
The scientific literature is split on this, but there’s enough evidence for further investigation, Srikanthan said. Her team has begun a study to research this connection.
We open the door for future obesity treatments
However, their discovery implies that more recent treatments could also be on the horizon.
Previous research had shown that the sympathetic nervous system, which controls your body's stress response, controls brown fat activity. But now that UCLA scientists have discovered the precise nerves that connect brown fat to the sympathetic nervous system, we could find ways to stimulate these pathways to activate brown fat – without the various associated organs (like the guts and stomach). to stimulate vast network of nerves, Srikanthan said.
According to the study, methods for this might include medication, electrical stimulation or heat therapy.
Still, there’s reason to temper expectations. “[Brown fat] “Depots are highly metabolically active, but quite small,” said Samuel. “The overall contribution to the energy balance of the whole body in humans is therefore likely to be small.”
On the opposite hand, this prediction doesn’t keep in mind what we have no idea.
“We are learning more about how tissues communicate with each other, beyond the release of hormones or metabolites,” said Samuel. Activating brown fat could “trigger signals that help coordinate energy metabolism throughout the body.”