Human brown fat associated with improved cardiac metabolic health

A study led by a team at The Rockefeller University found that people with detectable brown fat in their bodies were at lower risk of heart and metabolic disorders such as type 2 diabetes (T2DM) and coronary artery disease. .. The study, which the team analyzed positron emission tomography (PET) scans from more than 52,000 people, is claimed to be by far the largest in humans, confirming evidence of the health benefits of brown fat. And is expanding. Suggested by previous studies. “For the first time, we have a link to reducing the risk of certain conditions,” said Paul Cohen, MD, MD, assistant professor and attending physician at Rockefeller University Hospital. “These findings give us more confidence in the potential to target brown fat for therapeutic effects.”

Resnick and colleagues Nature medicine, “Brown adipose tissue is associated with cardiac metabolic health“Our study shows an important contribution of BAT to the health of cardiac metabolism and suggests that BAT has a therapeutic effect on humans,” they conclude.

Brown fat-or brown adipose tissue. BAT-Researchers have suggested that it is the type of organization you want more. Unlike white adipose tissue (white adipose tissue; WAT), which stores calories, brown fat burns the energy dissipated as heat, and scientists hope it holds the key to new treatments for obesity.

Brown fat has been studied in newborns and animals for decades, but scientists admitted that BAT is also found in some adults, usually the neck and shoulders, in 2009. was. “In 2009, a series of treatises confirmed the presence of active BAT in adults, which included lower body mass index (BMI), lower age, lower outside temperature, lower female gender, and lower blood sugar levels. Correlated with, “says the author. Since then, researchers have scrambled to study these elusive fat cells, which have the power to burn calories to generate heat in cold conditions.

However, it has long been unclear whether people rich in brown fat are healthier. In a small study of healthy humans, cold-activated BAT was associated with increased energy expenditure that “generated enthusiasm for BAT as a therapeutic target for obesity and related diseases,” among other metabolic effects. It is shown to be doing. But they admitted, “… these studies are too small to clearly address whether BAT is a clinically meaningful modulator of human metabolic and cardiovascular disease.”

Even identifying someone who has brown fat is difficult because the tissue is hidden deep inside the body. This means that large-scale studies of brown adipose are virtually impossible because the tissue is only visible on positron emission tomography (PET) scans. “These scans are expensive, but more importantly, they use radiation,” said Tobias Becher, lead author of the study and former clinician in Cohen’s lab. “We don’t want to expose many healthy people to it.”

Doctor-scientist Becher has come up with an alternative. His lab is directly opposite the Memorial Sloan Kettering Cancer Center, where thousands of people undergo PET scans each year to assess cancer. Becher knew that radiologists would regularly record brown fat detected in these scans so that it would not be mistaken for a tumor. “We realized that this could be a valuable resource to start looking at brown fat on a population scale,” Becher said.

In collaboration with Memorial Sloan Kettering’s Heiko Schoder and Andreas Wibmer, researchers reviewed 130,000 PET scans from 52,487 patients and found the presence of brown fat in nearly 10% of individuals. Cohen suggested that this number is likely to be underestimated, as patients were instructed to avoid cold exposure, exercise, and caffeine, which are thought to increase brown fat activity.

When researchers analyzed the data, they found that some common and chronic illnesses were less common among people with detectable brown fat. For example, only 4.6% had type 2 diabetes, compared to 9.5% of those who did not detect brown fat. Similarly, 18.9% of people with brown fat had abnormal cholesterol, but 22.2% of people without brown fat did.

In addition, the study found that people with brown fat also had a lower risk of high blood pressure, congestive heart failure, and coronary artery disease. These links have not been observed in previous studies. “BAT patients have a low prevalence of cardiovascular metabolic disease, and the presence of BAT is independent of type 2 diabetes, dyslipidemia, coronary artery disease, cerebrovascular disease, congestive heart failure, and reduced incidence of hypertension. They report that they were correlated, “they write. paper.

Another surprising finding was that brown fat may reduce the adverse health effects of obesity. “The beneficial effects of BAT are more pronounced in people who are overweight or obese, indicating that BAT may play a role in reducing the harmful effects of obesity,” they added. In general, obese people are at increased risk of heart and metabolic status. However, researchers have found that among obese people with brown fat, the prevalence of these conditions is similar to that of non-obese people. “They seem to be protected from the harmful effects of white fat,” Cohen said. “Obesity is generally associated with reduced BAT function, but obese people with BAT activity appear to be protected from conditions associated with excessive obesity,” the researchers further commented. did.

The actual mechanism by which brown fat may contribute to better health is still unknown, but there are some clues. For example, brown fat cells consume glucose to burn calories, which can lower blood sugar levels, a major risk factor for developing diabetes.

The role of brown fat is more mysterious in other conditions, such as hypertension, which is closely related to the hormonal system. “We are investigating that brown adipose tissue not only consumes glucose and burns calories, but is probably actually involved in hormonal signaling to other organs,” Cohen added.

The team plans to study the biology of brown fat further, looking for genetic variants that may explain why some people have more tissue than others. This knowledge may represent the first step in developing a drug that stimulates brown adipose activity as an approach for treating obesity and related conditions. “… The prevalence and activity volatility of BAT suggests potential genetic determinants of the biology,” the authors explained. “In line with this, our understanding of genetics as a contributor to T2DM development has evolved significantly. In that case, the genetic factors that contribute to the development and activity of BAT are type 2 diabetes and metabolic syndrome. May affect the etiology of. “

Cohen added, “A natural question everyone has is” what can we do to increase brown fat? ” There is no good answer to that yet, but it will be an exciting space for scientists to explore in the coming years. “

And, as the authors conclude, “despite considerable efforts to improve prevention and treatment, the emergence of BAT as a potential therapeutic target is attractive as the global obesity crisis worsens. Future research should aim to better understand human BAT regulation and develop mechanisms to safely coordinate BAT activities. “