The skin patch burns unwanted fat. (Credit: Columbia University Medical Center)

Researchers have devised a medicated skin patch that could be used to burn off pockets of unwanted fat such as “love handles” and treat metabolic disorders, such as obesity and diabetes. The patch turns energy-storing white fat into energy-burning brown fat locally while raising the body’s overall metabolism.

Humans have two types of fat. White fat stores excess energy in large triglyceride droplets. Brown fat has smaller droplets and a high number of mitochondria that burn fat to produce heat. Newborns have a relative abundance of brown fat, which protects against exposure to cold temperatures. But by adulthood, most brown fat is lost.

To apply the treatment, the drugs are first encased in nanoparticles, each roughly 250 nm in diameter. The nanoparticles are then loaded into a centimeter-square skin patch containing dozens of microscopic needles. When applied to skin, the needles painlessly pierce the skin and gradually release the drug from nanoparticles into underlying tissue.

The new treatment approach was tested in obese mice by loading the nanoparticles with one of two compounds known to promote browning: rosiglitazone (Avandia) or CL316243, a beta adrenergic agonist that has been shown to brown white fat in mice. Mice treated with either of the two drugs had a 20 percent reduction in fat on the treated side compared with the untreated side. They also had significantly lower fasting blood glucose levels than untreated mice.

The patch has not been tested in humans. The researchers are currently studying which drugs, or combination of drugs, work best to promote localized browning and increase overall metabolism.

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