"The groundwork of all happiness is health." - Leigh Hunt

Scientists find the “on” switch for energy-burning brown fat

Oct. 17, 2023 — A process your body uses to remain warm in cool weather could someday result in latest 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 drugs who oversaw the study research on the UCLA School of Medicine. “The challenge was to find a way to selectively stimulate [it].”

Brown fat is different from the fat typically related to obesity: the type that accumulates across 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, an element 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 latest 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] “Nerve cell activity is observed in rodents and humans, but probably indirectly through activation of specific brain regions,” explains Varman Samuel, MD, PhD, associate professor of medicine at Yale School of Medicine and chief of endocrinology at the VA Connecticut Healthcare System.

The scientific literature is divided on this matter, but there is enough evidence for further study, Srikanthan said. Her team has begun a study to investigate this connection.

We open the door for future obesity treatments

However, their discovery means that other new treatments may 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 many associated organs (like the heart and stomach). to stimulate vast network of nerves, Srikanthan said.

According to the study, methods for this could include medication, electrical stimulation or heat therapy.

Still, there is reason to temper expectations. “[Brown fat] Depots are metabolically highly active, but quite small,” said Samuel. “Therefore, their overall contribution to whole-body energy balance in humans is likely to be small.”

On the opposite hand, this prediction doesn't consider what we have no idea.

“We are learning more about how tissues communicate with each other, beyond the release of hormones or metabolites,” Samuel said. Activation of brown fat could “trigger signals that help coordinate energy metabolism throughout the body.”