5 facts your patients should know about brown fat

Naveed Saleh, MD, MS | November 11, 2021

Here’s an interesting fact: We have more than one color of fat in the body. Most of our fat is white fat. White fat stores extra energy. A more enigmatic type of adipose tissue is brown fat. It metabolizes glucose and fat molecules to generate heat and maintain body temperature. Cold temperatures trigger brown fat activity, causing a range of metabolic changes in the body.

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Young research scientist looking through microscope

Investigators are studying brown fat for its potential role in treating a variety of metabolic diseases.

Whereas excess white fat results in obesity, researchers are interested in leveraging the potential of brown fat to treat obesity, diabetes, and other metabolic diseases, according to the CDC.

Brown fat may be of interest to you and your patients. Here are five points to consider about brown fat.

It’s healthy

White fat consists of large lipid droplets and serves as a sink for energy. On the other hand, brown adipose tissue (BAT) has loads of mitochondria and converts chemical energy into heat to maintain body temperature. 

BAT activity is positively associated with human metabolic rate, and this activity decreases energy storage. Approaches that mediate BAT development and heighten BAT activity could combat obesity, as noted by the authors of a study published in Frontiers in Genetics.

It curbs the risk of cardiometabolic disease

Results from a study published in Nature Medicine bode well for obesity. Researchers retrospectively analyzed 134,529 18F-fluorodeoxyglucose positron emission tomography-computed tomography scans from 52,487 patients for the presence or absence of BAT. Notably, these scans were first used to diagnose, treat, or monitor cancer.

The researchers found that participants with BAT had a lower prevalence of cardiometabolic diseases, with the presence of BAT predicting lower rates of type 2 diabetes, dyslipidemia, coronary artery disease, cerebrovascular disease, congestive heart failure, and hypertension. These observations were bolstered by improved blood glucose, triglyceride, and high-density lipoprotein levels.

The investigators found that the benefits of BAT were greater in those who were overweight or had obesity. Consequently, BAT could attenuate the health harms of obesity, in addition to boosting heart health. 

Researchers are making strides in understanding it 

In light of its positive properties, researchers have taken great interest in unlocking the secrets of  BAT. For years, drug targeting focused on the β3-adrenergic receptor (β3-AR), which is the adrenergic receptor hypothesized to mediate BAT thermogenesis. Targeting this receptor, however, has largely failed in human clinical trials. In humans, the oral administration of the β3-AR agonist mirabegron boosted BAT thermogenesis only when taken at maximum doses.

The targeting of the β3-AR receptor is based on data from rodent studies. In a recent study published in Cell Metabolism, investigators report that, unlike in rodents, BAT lipolysis and thermogenesis transpire by β2-AR signaling.

“Our discovery that β2-AR stimulation is essential to human BAT lipolysis and thermogenesis now presents a novel pharmacological target to stimulate human BAT,” the authors wrote. “These results also provoke further questions regarding the intrinsic differences between human and rodent brown adipocytes and the implications for translational BAT research.”

Polyphenols could ‘brown’ white fat 

Experts hypothesize that fat browning could be a means of treating obesity and co-morbid metabolic disorders. The recruitment of BAT could lead to increased energy dissipation and lowered adiposity. 

In an article published in Critical Reviews in Food Science and Nutrition, authors wrote that mounting evidence indicates that the intake of polyphenols, which are antioxidants found in fruits, vegetables, and supplements, along with gut microecology could be linked to fat browning.

Based on a review of studies involving mouse models, they found that polyphenols may lead to brown fat activation and fat browning due to regulatory actions on gut microecology, such as microbial community profile, gut metabolites, and gut-derived hormones.

Testing for brown fat is difficult 

Even for researchers, testing for brown fat levels amounts to an ordeal. Only PET scans pick up brown fat, and they are expensive and involve radiation. This makes investigating brown fat in population-based studies challenging. Routine testing in any individual would be untenable.

Bottom line

The benefits of brown fat for obesity and metabolic disease are emerging. Although drug targets involving brown fat are being researched, fat browning or BAT recruitment are currently not accessible. Nevertheless, intake of certain foods, such as those containing polyphenols, might harness some benefits of brown fat.

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