Research: turning white fat into brown fat

Geschatte leestijd: 5 minuten White fat stores energy while brown fat boosts metabolism. Researchers have now succeeded in extracting white fat from your body, converting it into brown fat, and reimplanting it.

Brown fat

We have previously written about the differences between brown fat, white fat, and beige fat. In short, white fat cells store energy. They serve as a reserve fuel, but also contribute to the current epidemic of obesity. Brown fat has a different function. It can regulate temperature by generating extra heat. It does this by releasing energy to raise body temperature. Brown fat is mainly found in babies to protect them from cold. It was long thought that brown fat almost entirely disappeared afterward. Brown fat had been found in adults, but in very small amounts. Researchers therefore thought that brown fat in adults could not significantly contribute to fat burning [1,2]. About 10 years ago, however, it became clear that adults can also have significant amounts of brown fat [3-6]. This has brought brown fat into the spotlight of scientists who want to use this knowledge in the fight against obesity. Although more brown fat remains in adults than previously thought, this is still a smaller amount than in youth. This could therefore be a possible (partial) explanation for increasing obesity with age. Amounts of brown fat and its activity can vary from person to person, but are also dependent on certain circumstances. Exposure to cold remains an important external factor that can activate brown fat [7,8]. Brown fat also increases under those conditions because some white fat cells (also called ‘beige fat’) can start behaving like brown fat cells. Such a process that stimulates white fat cells to behave like brown fat cells is also called ‘browning of fat cells’.

Converting white fat into brown fat

We have previously written about experimental ways to achieve this ‘browning’. Earlier this year, researchers were able to inject thyroid hormone via a special patch. It would be a safer way to administer the drug directly. Other researchers, however, discovered a protein in the body that inhibits the conversion of white to brown fat. Disabling the protein led to weight loss in mice despite a high-fat diet. But the most well-known method remains cryolysis (or ‘cryolipolysis’). Exposure to cold. However, this has its practical limitations. Systemically administering cryotherapy is not possible for everyone. Local cold therapy remains safe and effective, but results are long-lasting and only localized [9,10,11].

Converting white fat outside the body into brown fat

In 2009, researchers already considered converting white fat into brown fat outside the body [12]. This would have several advantages. You don’t have to work with cold that needs to be systematically applied over a long term. You also don’t have to administer drugs into the body that can have side effects. And that’s exactly what researchers from Columbia Engineering have done [14]. They have developed a simple method to directly convert white fat outside the body into brown fat. The fat is removed and replaced using the same techniques plastic surgeons use daily in so-called ‘fat-grafting’. As an example, you can think of the buttocks of Temptation Island temptress Kelly, which are filled with fat from her abdomen. Now, however, it’s not about moving fat, but about replacing fat.

Our approach to increasing brown fat is potentially safer than drugs because the only thing going into patients is their own tissue, and it’s highly controllable because we can tune the amount of brown fat we inject. The process is also so simple that it could be potentially performed using an automated system within a doctor’s office or clinic.

“Refreshing your fat”

The team of researchers took fat cultures and exposed them to various growth factors and other ‘browning’ factors present in our bodies. They assessed the degree of browning by measuring various properties of brown fat such as the previously treated protein UCP1. In one of the experiments, they discovered that white fat from mice could be directly converted into brown fat outside the body. Moreover, the brown fat remained stable for a long time after injection into the same mouse (two months in the experiment). The latter is of course an important fact. Brown fat cells that arise, for example, from cold therapy, quickly revert back under normal temperatures. Although this ‘fat refresh treatment’ is minimally invasive, it helps if it doesn’t have to be performed weekly. After experiments with fat from mice, the researchers were successful in converting white fat from humans into brown fat outside their body.

This suggests that it might be possible one day to attempt our approach in humans as a potential therapy to help with weight loss, control of blood glucose levels, or to prevent weight gain

Although the treated mice showed no difference in body weight development, the researchers are hopeful. In their follow-up studies, they want to find out which dosages of brown fat are effective.

References

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12. Brown Fat in Humans: Turning up the Heat on ObesityDiabetes. 2009 Jul; 58(7): 1482–1484.doi:  10.2337/db09-0622
13. Nicole R. Blumenfeld, Hwan June Kang, Anna Fenzl, Ziwei Song, Janice J. Chung, Ranjodh Singh, Roshawn Johnson, Ayse Karakecili, Jun B. Feranil, Ninna S. Rossen, Vivian Zhang, Sahir Jaggi, Bret McCarty, Steven Bessler, Gary J. Schwartz, Robert Grant, Judith Korner, Florian W. Kiefer, Brian M. Gillette, Samuel K. Sia. A direct tissue-grafting approach to increasing endogenous brown fat. Scientific Reports, 2018; 8 (1)