CAMBRIDGE, Mass., May 2 (UPI) -- Fat mice lost 10 percent of their body weight after scientists treated them with drugs, packaged in nanoparticles, to turn energy-storing white fat into energy-burning brown fat, according to a recent study.
The transformation of white fat to brown fat in order to help obese people lose weight is not a new concept, though drugs that promote it can be harmful -- a problem scientists at the Massachusetts Institute of Technology and Brigham and Women's Hospital think they've solved.
Previous studies have shown turning white fat into brown or beige fat can help people lose weight, but there have not been effective methods of doing so.
Scientists at MIT have shown using the process of angiogenesis to promote the growth of new blood vessels can help with the transformation, though drugs to do so can harm other parts of the body.
In order to help the drugs reach their proper destination, the scientists devised a nanoparticle using two polymers to guide the drugs to their proper destination.
"This is a proof-of-concept approach for selectively targeting the white adipose tissue and 'browning it' to allow the body to burn fat," Dr. Omid Farokhzad, director of the Laboratory of Nanomedicine and Biomaterials at Brigham and Women's Hospital, said in a press release. "The technology could then be used with other drug molecules that may be developed or other targets that may come up."
For the study, published in the Proceedings of the National Academy of Sciences, the scientists sought to send two drugs, rosiglitazone, approved for diabetes treatment but rarely used because of its side effects, and a version of the human hormone prostaglandin, to activate a cellular receptor on blood vessels surrounding white adipose tissue.
The drugs are packaged with an inner shell made of the polymer polylactic-co-glycolic acid, which is used in many medical devices, and an outer shell of polyethylene glycol.
Using mice that had been fed a high-fat diet until they were obese, the scientists then intravenously treated them with the nanoparticle drug cocktail. The rodents lost about 10 percent of their body weight within 25 days, their levels of cholesterol and triglycerides went down and their bodies became more sensitive to insulin. No side effects were seen in the mice, which were dosed with the nanoparticle every other day for the duration of the trial.
Although the scientists suggest the drug could be given to morbidly obese patients in dire need of treatment using the intravenous method, they suggest further research should be done on an oral method.
The challenge is for a version that can penetrate the lining of the intestines while keeping the drugs from causing side effects if exposed to other organs, they say.
"The advantage here is now you have a way of targeting it to a particular area and not giving the body systemic effects," said Dr. Robert Langer, a professor at MIT and researchers at the Koch Institute for Integrative Cancer Research. "You can get the positive effects that you'd want in terms of antiobesity but not the negative ones that sometimes occur."
