Though it's long been known that there are two forms of fat or adipose tissue, white, which stores calories, and brown, which burns them for energy and warmth, figuring out how to safely create more of the desirable brown type has remained elusive. In an ideal world, there'd simply be a switch one could flip to convert white fat into brown and obesity would eventually become a thing of the past. Now, UC San Francisco (UCSF) Diabetes Center brown fat researcher Shingo Kajimura and his team have made a discovery that leads them to believe they've found that switch and one day, it just may lead to the long-sought solution for human obesity.

"It used to be thought that brown fat only exists in small animals, and only in infants in humans," Kajimura said. "Now we know that most adult humans have a significant amount of brown fat. A few years ago, we discovered a protein called PRDM16," he added. "This protein is considered to be a master regulator of brown fat development. The brown fat cells need this protein."

In their recent study, the UCSF team reports the discovery that a class of commonly prescribed Type-2 diabetes drugs, called TZDs (thiazolidinediones, such as Actos and Avandia), promoted the conversion of white fat cells into brown (in mice and culture dishes) by stabilizing the PRDM16 protein. Apparently, as more stabilized PRDM16 accumulates in white fat cells, it eventually reaches a concentration high enough to flip the gene-controlled switch that begins the desired conversion to brown fat. Unfortunately, TZDs can cause some serious problems on their own.

"A major concern with TZD drugs is that there are multiple side-effects including fluid retention and a risk of heart failure," Kajimura explained. "If we can design drugs that specifically stabilize PRDM16 protein, this can convert white blood cells into brown fat with fewer side-effects. While new drugs that target this protein may be years away, knowing the target may speed their development."

In the meantime, if you're prone to putting on the pounds, calorie deprivation and the treadmill may be the safest options for weight loss, at least until we learn how to safely throw that switch.

In the video below, Shingo Kajimura explains more about his team's discovery:

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